keep an auto-recipe building's summary between its cycles

A Smelter's recipe summary was dropped whenever it sat between cycles and shown
again when the next one started, as REQ-UI-RECIPE-SUMMARY asked. It is the
widest row of the card and a row of its own height, so the panel changed width
and height every time the building started or stopped -- which is exactly when
its status caption changes, and why the two looked connected.

It now keeps describing the recipe it ran last until another one runs, which
also holds the input chips' per-cycle amounts still instead of letting them
fall back to bare item names each time. A building that has never run a cycle
still has nothing to describe and shows no summary.

A Miner or Assembler never had this: its recipe is player-selected and outlives
the cycle.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JcReq7hVk4KUPhTDKWAG7K

docs/architecture.md

@@ -124,13 +124,31 @@ Within a single simulation tick, subsystems run in this fixed order. The order i
 Three product targets plus tests:
 
 - `lib/` — simulation + config. Depends on Qt Core + Qt Gui, toml++, tinyexpr. No QtWidgets.
-- `ui/` — QtWidgets + `QOpenGLWidget` code: header bar, game world view, selection panel, build button bar. Depends on `lib` and on Qt's OpenGL widgets module.
+- `ui/` — QtWidgets + `QOpenGLWidget` code: header bar, game world view, selection panel, build button bar, controls panel. Depends on `lib` and on Qt's OpenGL widgets module.
   - `ui/selection/` — the selection panel's contents. `SelectionPanel` itself only arbitrates between the two selection categories, picks a card from the catalog (`SelectionContentFactory`), and hosts one at a time; each kind of selection has its own `SelectionContent` subclass assembled from shared parts (REQ-UI-SELECTION-CARD, REQ-UI-SELECTION-CONTENT).
 - `app/` — thin `main()` that creates the simulation, the UI, and wires them together. Depends on `ui`.
 - `tests/` — Catch2 tests. Links only against `lib`.
 
 Directory discipline inside `lib/` keeps the internal sim/config seam clear; sim code must not reach into config parsing and vice versa.
 
+## Player Input
+
+Every player control is declared once, in `lib/core/ControlAction.h`, and read by three consumers that must never disagree about it:
+
+* **`ControlsPanel`** asks which actions apply and draws a row per action (REQ-UI-CONTROLS-CONTENT).
+* **`InputMapper`** resolves a key press to an action and fires the event that action stands for.
+* **`GameWorldView`** resolves a mouse gesture to an action and runs the branch that carries it out.
+
+The file declares; it never performs. It holds no simulation access, fires no events, and names nothing — display strings live in `ui/ControlActionText.h`, which renders each badge from the binding the resolver actually matches, so a chip cannot claim a key that does nothing. What an action *does* stays in the widget that always did it: the drag state machines, hit-testing, and command enqueuing were not moved.
+
+Three invariants are easy to break here:
+
+* **Do not add a shortcut straight to `InputMapper`'s switch or `mousePressEvent`'s branches.** Add the action and its binding to the table; the handler switches on the resolved action. A binding added directly is invisible to the panel, which is the drift the table exists to prevent. (Build hotkeys and `F3`/`F4` are deliberate exceptions, documented in the header and in REQ-UI-CONTROLS-ACCURACY.)
+* **Availability and display are different questions.** An action can be live in a context the panel does not advertise it in — `Ctrl`+click with an empty selection is the standing example. `isControlActionAvailable` answers the first, the per-context row lists answer the second, and `ControlActionTest` asserts the pairing that matters: every row's bindings resolve back to that row's action.
+* **Gesture state is shared, not owned by an action.** Whether a belt drag is in progress decides what the right mouse button means, so it lives on `BuildModeController` where the resolver can see it — as does the hovered-transfer flag. `m_boxSelecting` is likewise one gesture serving two actions (box select and deconstruct area).
+
+`ControlContext` is a plain snapshot rather than references to the live controllers, which is what keeps the rules testable without a world and stops an action reaching into the simulation: if a rule needs a fact, the fact is named in the struct and the caller supplies it. When bindings become player-configurable, only the binding tables in `ControlAction.cpp` turn from hard-coded data into loaded data.
+
 ## Belt Subsystem
 
 Belts and splitters are their own specialized subsystem. Belt items are **not** entities — they are transient data flowing through the belt representation. They do not have identities that persist across ticks.

docs/requirements.md

@@ -428,7 +428,7 @@ Any ship, module, building, or assembler recipe id that appears in no unlock gro
 
 ### Layout
 
-The screen is a single column: a header bar across the top and the game world view filling the whole area below it. There is no side panel. Both permanent UI widgets float over the game world — the build button bar (REQ-UI-BUILD-BAR) at its bottom center, and the selection panel (REQ-UI-SELECTION-PANEL) at its right edge, centered vertically within the height left above the build button bar and shown only while something is selected. Blueprints have no permanent screen real estate; they are reached through modal dialogs (REQ-UI-BLUEPRINT-DIALOG):
+The screen is a single column: a header bar across the top and the game world view filling the whole area below it. There is no side panel. All three permanent UI widgets float over the game world — the build button bar (REQ-UI-BUILD-BAR) at its bottom center, the selection panel (REQ-UI-SELECTION-PANEL) beside whatever is currently selected, shown only while something is selected and holding its place on the screen until the next selection, and the controls panel (REQ-UI-CONTROLS-PANEL) in its bottom-left corner, beside the build button bar and rising above it only when the two would overlap. Blueprints have no permanent screen real estate; they are reached through modal dialogs (REQ-UI-BLUEPRINT-DIALOG):
 
 ```
 +-----------------------------------------------------------+
@@ -439,9 +439,10 @@ The screen is a single column: a header bar across the top and the game world vi
 |                    Game World               |   Panel   | |
 |                                             +-----------+ |
 |                                                           |
-|                  +------------------+                     |
-|                  | Build Button Bar |                     |
-+------------------+------------------+---------------------+
+| +----------+                                              |
+| | Controls |     +------------------+                     |
+| |  Panel   |     | Build Button Bar |                     |
++-+----------+-----+------------------+---------------------+
                      (full window width)
 ```
 
@@ -454,14 +455,17 @@ The screen is a single column: a header bar across the top and the game world vi
 - REQ-UI-PAUSE-BORDER: While the game is paused (speed 0×, whether set via the speed controls (REQ-UI-SPEED), the Space toggle (REQ-UI-HOTKEYS), or an auto-pausing modal), a vignette border is drawn around the edges of the game world view to make the paused state hard to miss. The border is black and fades in the alpha channel from fully transparent at its inner (center-facing) edge to 50% opacity at the viewport edge, over a thickness of 100 pixels (capped at half the smaller viewport dimension on very small views).
 - REQ-UI-DECONSTRUCT-BORDER: While deconstruct mode is active (REQ-UI-DECONSTRUCT-BUTTON, REQ-UI-HOTKEYS), a vignette border is drawn around the edges of the game world view to signal the mode, matching the geometry of the paused-state vignette (REQ-UI-PAUSE-BORDER): a 100-pixel thickness (capped at half the smaller viewport dimension on very small views) with the four sides meeting along mitred corner diagonals. It fades in the alpha channel from fully transparent at its inner (center-facing) edge to the deconstruct tint color at the viewport edge. The color — including its alpha, which sets the peak opacity at the viewport edge — is read from `visuals.toml [overlays].deconstruct_tint`, the same deconstruct-mode color used for the hover tint. The border is presentation-only and has no effect on the simulation. If the game is both paused and in deconstruct mode, both vignettes are drawn and compose over each other.
 - REQ-UI-EXPAND-BUTTON: The header bar shows an asteroid expansion button captioned `Expand: <x>` followed by the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON) in place of the trailing `Blocks` word, where `<x>` is the current expansion cost computed from `world.toml [expansion].cost_building_blocks_formula` at the current number of purchased expansions (REQ-EXP-COST). When no icon file exists for `building_block`, the caption falls back to the `Expand: <x> Blocks` text. Clicking the button unlocks the next asteroid expansion (REQ-EXP-UNLOCK, REQ-GW-ASTEROID-EXPAND), spending that many building blocks from the global stock. The button is disabled when the player cannot currently afford the cost (consistent with REQ-UI-BUILD-DISABLED). The caption updates as the cost changes with each purchased expansion.
-- REQ-UI-WORLD-SIZE: The game world view occupies the full width of the game window and the full height below the header bar. No widget insets it: the build button bar (REQ-UI-BUILD-BAR) and the selection panel (REQ-UI-SELECTION-PANEL) float over it.
-- REQ-UI-SELECTION-PANEL: The **selection panel** (the panel described under Selection Panel, REQ-UI-SINGLE-SELECTION and following) is a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), anchored to the view's right edge with a small margin. It is **sized to its content in both width and height**, so it grows and shrinks as the selection changes, staying right-anchored as its size changes.
-
-  The panel's vertical placement and maximum height are defined against an **available band**: the height of the game world view, less the panel's top and bottom margins, less the height of the horizontal strip occupied by the build button bar at the bottom of the view (the bar's height plus its bottom margin, REQ-UI-BUILD-BAR) — the bar's band is subtracted over the full view width, regardless of how wide the bar currently is. The panel is **vertically centered within that available band**, not within the full view height, so it sits slightly above the view's vertical center. Should its content ever be taller than the band, the panel's height is capped at the band height and the content scrolls vertically within it.
+- REQ-UI-WORLD-SIZE: The game world view occupies the full width of the game window and the full height below the header bar. No widget insets it: the build button bar (REQ-UI-BUILD-BAR), the selection panel (REQ-UI-SELECTION-PANEL), and the controls panel (REQ-UI-CONTROLS-PANEL) float over it.
+- REQ-UI-SELECTION-PANEL: The **selection panel** (the panel described under Selection Panel, REQ-UI-SINGLE-SELECTION and following) is a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), placed **beside the objects it describes** rather than at a fixed corner of the view, so it appears where the player is already looking. It is **sized to its content in both width and height**, so it grows and shrinks as the content changes. It keeps the same small margin from the view's edges that it uses as its gap from the selection.
+  - **Anchor rectangle.** The panel is placed against the screen rectangle of the selection **at the moment that selection started**: the footprint of the single object selected (a building or construction site, an actor, or a piece of debris), or, when the selection started as a multi-selection (REQ-UI-MULTI-SELECT), the bounding box of all the objects it started with.
+  - **Side.** The panel goes to the **right** of the anchor rectangle, separated from it by the panel's margin, whenever it fits within the view there. Otherwise it goes to the **left** of the anchor rectangle by that same margin. When it fits on neither side — a bounding box spanning most of the view, or an object too close to an edge — it is placed on whichever side leaves more room and then pushed inside the view. That is the one case in which the panel covers part of the selection.
+  - **Vertical placement.** The panel's **top edge is aligned with the anchor rectangle's top edge** and it extends downward. Its bottom is limited by the lowest of: the view's bottom edge less the panel's margin; and the top edge, less that margin, of the build button bar (REQ-UI-BUILD-BAR) or the controls panel (REQ-UI-CONTROLS-PANEL) — but each of those two only where the panel's own horizontal extent actually overlaps that widget's current rectangle, so a panel whose column misses them is not shortened by them. Should the panel not fit above that limit, it is shifted up, as far as the view's top margin and no further; if it still does not fit, its height is capped at the space available there and the content scrolls vertically within it.
+  - **Fixed for the life of the selection.** The anchor rectangle and the side are determined once, when the selection starts, and are not revisited while that selection lasts; the panel's own size is the only thing that may still move it (see **Resizing in place** below). The panel **keeps its place on the screen** when the player scrolls the view (REQ-UI-SCROLL) and when a selected object moves under it (a selected ship flying away), rather than following the object — which may leave it beside nothing, or beside an object that has left the view entirely. It likewise does not move when the selection is **expanded** by adding objects or reduced by removing them (REQ-UI-MULTI-SELECT), nor when a selected object is destroyed or deconstructed. Starting a **new** selection — clicking a different object, or a box drag that replaces the selection — places the panel anew against the new anchor rectangle.
+  - **Resizing in place.** Only the anchor rectangle and the chosen side are fixed for the life of the selection; the panel's geometry is **re-solved from them** whenever its content size changes (a section appearing or disappearing as the selection's state changes), the view is resized, or the build button bar's or controls panel's rectangle changes. Re-solving keeps the two edges the panel was placed by — its top edge, and the edge facing the anchor rectangle (its left edge when it sits to the right of the selection, its right edge when it sits to the left) — so the panel grows away from the selection rather than over it, and it never switches sides for as long as the selection lasts. What re-solving may change is the vertical result: growth that would take the panel outside the view or into either of those two widgets is resolved as in **Vertical placement** above, by shifting it up and capping its height, and a panel that shrinks again regains the room.
   - **Visibility.** The panel is shown only while at least one object is selected. With an empty selection it is not shown at all (REQ-UI-EMPTY-SELECTION), leaving the full game world view visible.
-  - **Overlay behavior.** As for the build button bar (REQ-UI-BUILD-BAR): the panel occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected. It is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full right-hand band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the panel. The panel and the build button bar never overlap, because the panel's available band excludes the bar's strip; the bar itself never moves on the panel's account (REQ-UI-BUILD-BAR).
+  - **Overlay behavior.** As for the build button bar (REQ-UI-BUILD-BAR): the panel occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected. It is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the panel. The panel never overlaps the build button bar or the controls panel, because it stays above both wherever their rectangles meet its own; neither of them ever moves on the panel's account (REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL).
   - **Input.** Mouse events over the panel are consumed by the panel and never reach the game world: hovering it shows no builder-mode ghost at the tile beneath, and clicking it neither places a building nor changes the selection. Right-clicking the panel does not exit builder mode (REQ-BLD-BUILDER-MODE) or cancel a belt drag (REQ-BLD-BELT-DRAG).
-- REQ-UI-MODAL-DIM: While a modal dialog, menu, or full-screen state screen is open on top of the game, a transparent black overlay (a dim/scrim) is drawn over the **entire game window** — the header bar, the game world view, and the widgets floating over it (the build button bar, REQ-UI-BUILD-BAR, and the selection panel, REQ-UI-SELECTION-PANEL) — behind that modal, so the game reads as inactive while the modal holds focus. The overlay is shown for every modal that auto-pauses the simulation — the escape menu (REQ-UI-GAME-MENU), the recipe/schematic selection dialog (REQ-UI-SELECT-BUTTON), the layout configuration dialog (REQ-MOD-UI-DIALOG), the schematic choice dialog (REQ-DEF-SCHEMATIC-DROP), the blueprint save dialog (REQ-UI-BLUEPRINT-CREATE), and the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG) — as well as the game-over screen (REQ-HQ-GAME-OVER) and the win screen (REQ-WIN-SCREEN), which end rather than pause the game. When modals are nested (for example the Create Blueprint name dialog (REQ-MOD-UI-BLUEPRINT-CREATE) opened from the layout configuration dialog), only a single dim is shown over the game window; nested modals do not stack additional overlays. The same applies when one modal hands directly off to another — the blueprint save dialog opening the blueprint selection dialog on confirm (REQ-UI-BLUEPRINT-CREATE): the dim persists across the handoff rather than flickering off and back on, and the simulation is not resumed in between. The dim color and opacity are read from `visuals.toml [overlays]` (a semi-transparent black modal-dim color), consistent with the other overlay colors. The overlay is presentation-only and has no effect on the simulation.
+- REQ-UI-MODAL-DIM: While a modal dialog, menu, or full-screen state screen is open on top of the game, a transparent black overlay (a dim/scrim) is drawn over the **entire game window** — the header bar, the game world view, and the widgets floating over it (the build button bar, REQ-UI-BUILD-BAR, the selection panel, REQ-UI-SELECTION-PANEL, and the controls panel, REQ-UI-CONTROLS-PANEL) — behind that modal, so the game reads as inactive while the modal holds focus. The overlay is shown for every modal that auto-pauses the simulation — the escape menu (REQ-UI-GAME-MENU), the recipe/schematic selection dialog (REQ-UI-SELECT-BUTTON), the layout configuration dialog (REQ-MOD-UI-DIALOG), the schematic choice dialog (REQ-DEF-SCHEMATIC-DROP), the blueprint save dialog (REQ-UI-BLUEPRINT-CREATE), and the blueprint selection dialog (REQ-UI-BLUEPRINT-DIALOG) — as well as the game-over screen (REQ-HQ-GAME-OVER) and the win screen (REQ-WIN-SCREEN), which end rather than pause the game. When modals are nested (for example the Create Blueprint name dialog (REQ-MOD-UI-BLUEPRINT-CREATE) opened from the layout configuration dialog), only a single dim is shown over the game window; nested modals do not stack additional overlays. The same applies when one modal hands directly off to another — the blueprint save dialog opening the blueprint selection dialog on confirm (REQ-UI-BLUEPRINT-CREATE): the dim persists across the handoff rather than flickering off and back on, and the simulation is not resumed in between. The dim color and opacity are read from `visuals.toml [overlays]` (a semi-transparent black modal-dim color), consistent with the other overlay colors. The overlay is presentation-only and has no effect on the simulation.
 
 ### Game World
 
@@ -504,6 +508,8 @@ The screen is a single column: a header bar across the top and the game world vi
     - **1** — Belt, **2** — Splitter, **3** — Tunnel (the unified tunnel build mode, REQ-BLD-TUNNEL-MODE). Hotkey 4 is unused.
     - **Shift+1** — Miner, **Shift+2** — Smelter, **Shift+3** — Assembler, **Shift+4** — Shipyard, **Shift+5** — Salvage Bay, **Shift+6** — Reprocessing Plant.
 
+  These shortcuts are the definition; the controls panel (REQ-UI-CONTROLS-PANEL) displays the subset of them that applies to the player's current situation, and the build buttons carry the build hotkeys on their badges (REQ-UI-BUILD-COST). Neither display defines a binding of its own.
+
 ### Debug Draw
 
 - REQ-UI-DEBUG-DRAW: A debug draw mode can be toggled on and off with the **F3** key. It is inactive by default. While active, the sensor range of every ship — both player and enemy — is drawn as a circle centered on the ship, using that ship schematic's outline color from `visuals.toml`.
@@ -534,7 +540,7 @@ The panel shows exactly one **content** at a time, picked from the catalog in RE
 - REQ-UI-SELECTION-CARD: **Card structure.** Every panel content is a card with the same three parts, top to bottom:
   - **Header** — always shown. It holds the selection's identity symbol on the left — the building's icon glyph (REQ-UI-WORLD-ICON), a ship's schematic color swatch, or the kind symbol of a defence station or piece of debris — the selection's name beside it, and one optional **right slot**. The right slot holds a status indicator (REQ-UI-SELECTION-STATUS), a ship's current behavior (REQ-UI-SHIP-BEHAVIOR), or an object count — never more than one of them; which one applies is stated per content in REQ-UI-SELECTION-CONTENT.
   - **Configuration group** — the controls that change how the selected object is set up: the recipe/schematic selection control (REQ-UI-SELECT-BUTTON), a shipyard's layout preview and Configure button (REQ-MOD-UI-PREVIEW), and a splitter's output filters (REQ-BLD-SPLITTER). It is shown identically for an operational building and for a construction site of the same type (REQ-BLD-SITE-CONFIG).
-  - **Runtime group** — what the object is currently doing: buffer contents, production progress, HP, remaining scrap, and the belt clear action (REQ-UI-BELT-CLEAR). For a **construction site** the entire runtime group is replaced by a captioned `Construction` section: a progress bar filled to the site's construction completion with that completion as an integer percentage beside the caption — the same value the world draws on the footprint (REQ-UI-CONSTRUCTION-PROGRESS) — followed by a note that buffers appear once the building is built, because a site has neither buffers nor a production cycle (REQ-BLD-SITE-CONFIG). The configuration group is unaffected and stays visible on a site.
+  - **Runtime group** — what the object is currently doing: buffer contents, production progress, HP, remaining scrap, and the belt clear action (REQ-UI-BELT-CLEAR). Where the object has **HP**, its bar is the first thing in this group, above everything else the card shows (REQ-UI-HQ-PANEL, REQ-UI-SHIP-STATS-PANEL, REQ-UI-STATION-STATS-PANEL) — how close the thing is to dying outranks what it is holding. For a **construction site** the entire runtime group is replaced by a captioned `Construction` section: a progress bar filled to the site's construction completion with that completion as an integer percentage beside the caption — the same value the world draws on the footprint (REQ-UI-CONSTRUCTION-PROGRESS) — followed by a note that buffers appear once the building is built, because a site has neither buffers nor a production cycle (REQ-BLD-SITE-CONFIG). That section sits **directly below the header, above the configuration group**, so how far along the site is reads first; the configuration group is otherwise unaffected and stays visible on a site.
 
   A group with nothing to show takes no space, so a content may consist of a header alone. Within a group, related parts form **sections** carrying a short caption above them (e.g. `Layout`, `Input buffers`, `Production`, `Output buffer`); a section and its caption are shown only while that section has content, so e.g. a Miner (which consumes nothing) shows no input buffer section.
 - REQ-UI-SELECTION-CONTENT: **Content catalog.** Which content the panel shows follows from the selection alone:
@@ -565,9 +571,13 @@ The panel shows exactly one **content** at a time, picked from the catalog in RE
   - an **input** chip shows the per-cycle amount below the count (the items consumed per run, e.g. `/ 2 per cycle`), or the count alone when the building has no selected recipe or schematic to give one;
   - an **output** chip shows the count against the output buffer's capacity as `a / b` (REQ-MAT-OUTPUT-BUFFER), with the item's name below.
 
-  Input and output chips form separately captioned sections, each shown only while it holds something (REQ-UI-SELECTION-CARD). For a selected construction site the buffer sections are omitted (REQ-BLD-SITE-CONFIG).
-- REQ-UI-RECIPE-SUMMARY: Below the recipe/schematic selection control, a building running a recipe or schematic shows a one-line **recipe summary**: each input item's icon with its per-cycle amount, an arrow, each output item's icon with its per-cycle amount, and the cycle time in seconds. It restates what the building will do without opening the selection dialog, and it is the panel's only display of the cycle time. For a Shipyard the summary is built from the schematic's materials and production time including the placed modules' contributions (REQ-BLD-SHIPYARD, REQ-MOD-STAT-CALC), matching the buffers beneath it. Auto-recipe buildings (Smelter, Reprocessing Plant — REQ-BLD-SMELTER, REQ-BLD-REPROCESSING) have no player-selected recipe and so show no selection control; they show the summary of the recipe currently in production, and none while idle. A building with no recipe or schematic selected shows no summary.
-- REQ-UI-PRODUCTION-PROGRESS: For buildings that produce items or ships (miner, smelter, assembler, reprocessing plant, shipyard), the panel's runtime group shows a captioned **production section**: a horizontal progress bar filled to the completion of the active production cycle, with that completion beside the caption as an integer percentage (e.g. `72%`), or the text `idle` in place of the percentage and an empty bar when no production cycle is active. The cycle time is shown in the recipe summary (REQ-UI-RECIPE-SUMMARY) rather than repeated here. When no recipe or schematic is selected, the production section is not shown at all.
+  Input and output chips form separately captioned sections (REQ-UI-SELECTION-CARD). A section lists a chip for **every item the building's cycle involves**, and for an auto-recipe building every item it handles at all, whether or not the buffer currently holds any: an empty buffer reads `0` rather than its chip disappearing, so the card keeps one shape while the building runs. A section left with no chips at all is not shown. The production section (REQ-UI-PRODUCTION-PROGRESS) sits **between them**, so the card reads in the direction the materials flow: what goes in, what is being made of it, what has come out. For a selected construction site the buffer sections are omitted (REQ-BLD-SITE-CONFIG).
+
+  **Only unlocked items are listed.** A building's buffers may carry entries for items the player cannot make yet — an auto-recipe building's buffers are sized over *every* recipe of its type (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING), including recipes that are still locked. Those entries are left out of both sections, consistent with the rest of the UI hiding what is not unlocked yet (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SPLITTER), so a Smelter shows the ores it can actually smelt rather than every ore in the game.
+
+  **An idle auto-recipe building still shows what it handles.** Having no selected recipe (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING), it would otherwise show empty sections whenever it happens to be between cycles. Its input and output sections instead list the unlocked items of every recipe of its type — the same union its buffers were sized over — with a count and no per-cycle denominator, since no one recipe is in force. While a cycle is running, that cycle's recipe supplies the denominators as for any other building.
+- REQ-UI-RECIPE-SUMMARY: Below the recipe/schematic selection control, a building running a recipe or schematic shows a one-line **recipe summary**: each input item's icon with its per-cycle amount, an arrow, each output item's icon with its per-cycle amount, and the cycle time in seconds. It restates what the building will do without opening the selection dialog, and it is the panel's only display of the cycle time. For a Shipyard the summary is built from the schematic's materials and production time including the placed modules' contributions (REQ-BLD-SHIPYARD, REQ-MOD-STAT-CALC), matching the buffers beneath it. Auto-recipe buildings (Smelter, Reprocessing Plant — REQ-BLD-SMELTER, REQ-BLD-REPROCESSING) have no player-selected recipe and so show no selection control; they show the summary of the recipe currently in production and, while between cycles, of the one they ran last. They keep it rather than dropping it, because a summary that came and went with each cycle would resize the card in step with the building's status (REQ-UI-SELECTION-STATUS), which is the one thing the panel must not do while the player is reading it (REQ-UI-SELECTION-PANEL). Such a building shows no summary only until it has run its first cycle. A building with no recipe or schematic selected shows no summary.
+- REQ-UI-PRODUCTION-PROGRESS: For buildings that produce items or ships (miner, smelter, assembler, reprocessing plant, shipyard), the panel's runtime group shows a captioned **production section** between the input and output buffer sections (REQ-UI-SINGLE-SELECTION): a horizontal progress bar filled to the completion of the active production cycle, with that completion beside the caption as an integer percentage (e.g. `72%`), or the text `idle` in place of the percentage and an empty bar when no production cycle is active. The cycle time is shown in the recipe summary (REQ-UI-RECIPE-SUMMARY) rather than repeated here. When no recipe or schematic is selected, the production section is not shown at all.
 - REQ-UI-MULTI-SELECT: The player selects multiple objects by box-drag or by Ctrl+clicking individual objects to add or remove them from the selection. Multi-select operates within a single category (REQ-UI-SELECTION-CATEGORIES). A box-drag that covers at least one building selects buildings (any field objects within the box are ignored — buildings win); a box-drag that covers no building but does cover ships, defence stations, or debris selects all of those field objects together (REQ-UI-ENTITY-CLICK-SELECT, REQ-UI-DEBRIS-MULTI-SELECT).
 - REQ-UI-MULTI-SELECTION: When multiple buildings are selected and the selection does not aggregate (REQ-UI-SELECTION-AGGREGATE), the panel shows a count summary. Its header names the size of the selection as `<n> buildings` in place of an object name, and carries no symbol and nothing in its right slot. Below it is one row per selected building type — the type's symbol, its name, and the number selected as `x<count>` — one type per row, and no per-building detail. A final row shows the **total building block cost** of the selection, captioned `Total cost` with the value followed by the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON): the sum of each selected building's placement cost (`buildings.toml [[building]].cost`, per REQ-BLD-COST), counting only player-placeable buildings (buildings with a button in the build button bar); non-player-placeable buildings (the HQ and defence stations) are excluded from the total, consistent with the blueprint total (REQ-UI-BLUEPRINT-CARD). Construction sites count at their building type's full placement cost regardless of construction progress.
 - REQ-UI-CONFIG-INLINE: Recipe and schematic configuration for a selected building is shown within this panel, in its configuration group (REQ-UI-SELECTION-CARD). Recipe selection (miner, assembler) and schematic selection (shipyard) use the selection button and dialog (REQ-UI-SELECT-BUTTON) rather than an inline control. For shipyards, the panel additionally shows the ship layout preview and "Configure" button below the schematic selection button (REQ-MOD-UI-PREVIEW).
@@ -577,7 +587,7 @@ The panel shows exactly one **content** at a time, picked from the catalog in RE
   - For a **ship schematic** (Shipyard): the ship's `display_name`; the name and quantity of each base required material (`[ship.schematic].materials`, excluding any module contributions); the base production time (`[ship.schematic].production_time_seconds`); and "Produces: 1 <ship display name>".
 - REQ-UI-RECIPE-ICON: In the recipe-selection dialog (REQ-UI-SELECT-BUTTON) for a Miner or Assembler, each recipe option button shows the icon of the recipe's produced item **instead of** its name caption (icon-only). The item shown is the recipe's `icon` field if set, otherwise its first output item; the icon is that item's icon per REQ-UI-ITEM-ICON. When the item has no icon file, the button falls back to the recipe/item name caption. The recipe name and details remain available on hover via the selection info tooltip (REQ-UI-SELECT-TOOLTIP). The `(None)` option keeps its text caption. This applies only to recipe options; the Shipyard schematic-selection dialog is unaffected and continues to show ship name captions.
 - REQ-UI-BELT-CLEAR: When one or more belt, splitter, tunnel entry, or tunnel exit tiles are selected, the panel's runtime group shows a **"Clear stuck items"** button that removes all items from the selected tiles. Clearing a tunnel entry or exit also discards all items currently in transit through that tunnel (REQ-BLD-TUNNEL-TRANSIT). This can be used to resolve stalled belts, splitters, and tunnels. The button acts on every selected tile, which is why a selection of belts and tunnel ends aggregates into one content rather than a count summary (REQ-UI-SELECTION-AGGREGATE).
-- REQ-UI-HQ-PANEL: When the HQ is selected, the panel shows the **global building blocks stock** — the same value as the header bar's stock display (REQ-UI-BLOCKS-ICON), rendered as an item chip (REQ-UI-SINGLE-SELECTION) carrying the `building_block` icon — and the HQ's **HP** as a bar labelled `current / maximum` (REQ-HQ-STATS, REQ-UI-HP-BARS). The HQ has no input or output buffers of its own: building blocks delivered by belt go straight into the global stock (REQ-HQ-BELT-INPUT), and showing that stock on the HQ is what tells the player to route blocks there. The HQ has no configuration group and no status indicator (REQ-UI-SELECTION-STATUS), and it is never a construction site.
+- REQ-UI-HQ-PANEL: When the HQ is selected, the panel shows the HQ's **HP** as a bar labelled `current / maximum` (REQ-HQ-STATS, REQ-UI-HP-BARS) and, beneath it, the **global building blocks stock** — the same value as the header bar's stock display (REQ-UI-BLOCKS-ICON), rendered as an item chip (REQ-UI-SINGLE-SELECTION) carrying the `building_block` icon. The HP comes first, as it does on every card that has it (REQ-UI-SELECTION-CARD). The HQ has no input or output buffers of its own: building blocks delivered by belt go straight into the global stock (REQ-HQ-BELT-INPUT), and showing that stock on the HQ is what tells the player to route blocks there. The HQ has no configuration group and no status indicator (REQ-UI-SELECTION-STATUS), and it is never a construction site.
 - REQ-UI-ENTITY-CLICK-SELECT: The player can click any ship (player or enemy) or any defence station (player or enemy) in the game world to select it. A plain click on a ship or defence station makes it the sole selection, clearing any previous selection. Ships and defence stations can be multi-selected — by Ctrl+clicking individual actors to add or remove them, or by box-drag (REQ-UI-MULTI-SELECT) — and can be selected together with debris and with one another in a single field selection (REQ-UI-SELECTION-CATEGORIES), freely mixing player and enemy actors. Actors cannot be selected together with buildings: selecting a ship or defence station clears any building selection, and selecting a building clears the actors (buildings win). Clicking a piece of debris adds to or establishes a field selection (REQ-UI-DEBRIS-CLICK-SELECT). Clicking empty world space (no building, ship, defence station, or piece of debris) clears the selection.
 - REQ-UI-SHIP-STATS-PANEL: When exactly one ship is selected (REQ-UI-ENTITY-CLICK-SELECT) and no debris is selected, the selection panel shows a **ship stats panel**. (If debris is also selected, the panel shows the compact count summary instead, per REQ-UI-FIELD-MULTI-SELECTION.) The panel structure mirrors REQ-MOD-UI-STATS-PANEL but reflects the ship's actual live state: stats are computed from its installed modules per REQ-MOD-STAT-CALC. Its header (REQ-UI-SELECTION-CARD) carries the schematic's color swatch and display name, with the ship's current behavior in the right slot (REQ-UI-SHIP-BEHAVIOR). The panel always shows all hull stats: HP (current / maximum) as a **bar** with the two values beside its caption, then max linear speed, sensor range, main acceleration, maneuvering acceleration, angular acceleration, and max rotation speed as label/value rows. In addition, capability module summaries are shown below the hull stats, each as its own outlined row, conditioned on which module types are installed and using the same aggregation rules as REQ-MOD-UI-STATS-PANEL: weapons (combined DPS, maximum range), salvage (combined collection rate, maximum range), and repair (combined repair rate, maximum range), each appearing only if at least one instance of that module type is installed. While debug draw mode is active (REQ-UI-DEBUG-DRAW), the panel additionally shows the ship's derived threat cost (REQ-MOD-THREAT).
 - REQ-UI-SHIP-BEHAVIOR: The ship stats panel (REQ-UI-SHIP-STATS-PANEL) additionally displays the selected ship's **current behavior** in its header's right slot (REQ-UI-SELECTION-CARD) — a single label naming the top-priority behavior currently governing the ship's navigation, as resolved by the fixed-priority behavior arbitration. Only the winning behavior is named; lower-priority behaviors that are suppressed are not shown, and neither are the salvage/repair cycles that run regardless of the active behavior (REQ-SHP-SALVAGE, REQ-SHP-REPAIR). The label updates live as the ship's behavior changes, and it is always shown (independent of debug draw mode, unlike the threat-cost line of REQ-UI-SHIP-STATS-PANEL). This applies to both player and enemy ships (REQ-UI-ENTITY-CLICK-SELECT); enemy ships only ever show **Engaging** or **Advancing**. The behavior labels (all wrapped in `tr()`) are:
@@ -598,7 +608,7 @@ The panel shows exactly one **content** at a time, picked from the catalog in RE
 
 - REQ-UI-BUILD-BAR: All placeable building types are shown as a **single horizontal row** of buttons with no grouping and no wrapping, inside a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), horizontally centered and anchored at the bottom edge with a small margin. Tunnel Entry and Tunnel Exit share a single **Tunnel** button (REQ-BLD-TUNNEL-MODE) rather than one button each. The bar is sized to its buttons and re-centers whenever the set of shown buttons changes (REQ-LOCK-BUILDING) or the view is resized.
   - **Overlay behavior.** The bar occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected (the world is not inset for the bar). The bar is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full 100-pixel bottom band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the bar.
-  - **No overlap with the selection panel.** The bar and the selection panel (REQ-UI-SELECTION-PANEL) never overlap, and keeping them apart is entirely the panel's job: the bar's position depends only on its own button set and the view size, and it never moves, re-centers, or resizes because the panel appears, disappears, or changes size. The panel instead confines itself to the view height less the bar's strip (REQ-UI-SELECTION-PANEL).
+  - **No overlap with the selection panel.** The bar and the selection panel (REQ-UI-SELECTION-PANEL) never overlap, and keeping them apart is entirely the panel's job: the bar's position depends only on its own button set and the view size, and it never moves, re-centers, or resizes because the panel appears, disappears, or changes size. The panel instead steps around the bar's current rectangle wherever its own column would meet it (REQ-UI-SELECTION-PANEL).
   - **Input.** Mouse events over the bar are consumed by the bar and never reach the game world: hovering it shows no builder-mode ghost at the tile beneath, and clicking it neither places a building nor changes the selection. Right-clicking the bar does not exit builder mode (REQ-BLD-BUILDER-MODE) or cancel a belt drag (REQ-BLD-BELT-DRAG).
 - REQ-UI-BUILD-COST: Each button is **icon-only with a cost**, its face composed of three elements: the button's **hotkey badge** in the top-left corner, the building's icon (REQ-UI-BUILD-ICON) centered below it, and the building block cost centered under the icon, shown with the `building_block` item icon (REQ-UI-BLOCKS-ICON, REQ-UI-ITEM-ICON) to the right of the number in place of the trailing `Blocks` word, e.g. `2` then a small block icon. The building name is not shown on the button; it is shown in the button's hover tooltip instead (REQ-UI-BUILD-TOOLTIP). When no icon file exists for `building_block`, the cost is shown as the bare number. The Deconstruct button (REQ-UI-DECONSTRUCT-BUTTON) has no cost and shows its name as a text caption in the cost's place.
   - **Hotkey badge.** The badge names the build hotkey that activates the button (REQ-UI-HOTKEYS), so the player can learn the shortcuts from the bar itself. It is rendered dimmer than the cost so it reads as secondary, but at the same size and in bold, because a smaller badge is not legible. A plain-digit hotkey is shown as the bare digit (`1`, `2`, `3`); a Shift+digit hotkey is shown with an upwards arrow prefixed and no separator (`↑1` … `↑6`); the Deconstruct button shows `Q`. A button whose building type has no build hotkey shows no badge and keeps the same face size, so the row stays even.
@@ -607,6 +617,79 @@ The panel shows exactly one **content** at a time, picked from the catalog in RE
 - REQ-UI-BUILD-DISABLED: Buttons for buildings the player cannot currently afford are shown as disabled. A disabled button's icon (REQ-UI-BUILD-ICON) is rendered in a greyed variant, with its colored chip background recolored grey while the white glyph is retained.
 - REQ-UI-DECONSTRUCT-BUTTON: A dedicated **Deconstruct** button is shown in the build button bar (REQ-UI-BUILD-BAR), as the last entry of the row and **visually separated** from the building-type buttons by a gap (not a divider line), because it toggles a mode rather than selecting a building type. Its face follows REQ-UI-BUILD-COST with two differences: its hotkey badge reads `Q`, and because it has no building block cost it shows its **Deconstruct** name as a text caption where the building-type buttons show their cost — so it is the one labelled button in the bar. It is therefore wider than the building-type buttons, which share a uniform width. Clicking it toggles deconstruct mode on and off, equivalent to the Q deconstruct toggle (REQ-UI-HOTKEYS). The button is shown in a visually active/pressed state while deconstruct mode is active. The button shows a hover tooltip stating the deconstruction refund (REQ-BLD-DECONSTRUCT): that deconstructing a fully-built building returns `world.toml [world].refund_percentage` percent of its building block cost once deconstruction completes, and that a construction site removed before it finishes building is refunded in full. When `refund_percentage` is 100% both cases yield the same refund, and the tooltip is simplified to state the single refund percentage without distinguishing the two cases. Unlike the building-type button tooltips (REQ-UI-BUILD-TOOLTIP), this tooltip is not config-defined text but is composed from the refund percentage.
 
+### Controls Panel
+
+The controls panel tells the player which controls are available right now. It is context-sensitive: the game is always in exactly one **control context**, derived from the active build mode and the current selection, and the panel shows that context's rows and no others. Its position, size, and overlay behavior are defined in REQ-UI-CONTROLS-PANEL; its structure in REQ-UI-CONTROLS-CARD; and which rows each context shows in REQ-UI-CONTROLS-CONTENT. The panel never defines a binding: every row restates one already defined in REQ-UI-HOTKEYS or in the mouse gestures cited beside it.
+
+- REQ-UI-CONTROLS-PANEL: The **controls panel** is a widget that **floats over the game world view** (REQ-UI-WORLD-SIZE), anchored to the view's **bottom-left corner** with a small margin on both edges. It is **sized to its content in both width and height**, growing and shrinking upward from that corner as the context changes. Should its content ever be taller than the view, the panel's height is capped at the view height less its margins and the content scrolls vertically within it. The selection panel is placed beside the current selection (REQ-UI-SELECTION-PANEL) and so can reach this corner; the two never overlap, and keeping them apart is entirely the selection panel's job — this panel's position depends only on its own content, the view size, and the build button bar, and it never moves or resizes because the selection panel appears, disappears, or changes size.
+  - **Stepping around the build button bar.** Like the selection panel (REQ-UI-SELECTION-PANEL), the panel does **not** confine itself to the band above the build button bar's strip: the bar is horizontally centered and sized to its buttons (REQ-UI-BUILD-BAR), so it normally leaves this corner free, and the panel shares the view's bottom edge with it. The panel **rises only to avoid an actual overlap**: whenever the panel at the bottom-left corner would intersect the bar's current rectangle, it is moved up so that its bottom edge clears the bar's top by the same margin it keeps from the view's edges, and its height is capped at the space that leaves. Whether it rises therefore depends on how wide the bar and the panel currently are, and it returns to the corner as soon as they no longer meet. The bar never moves on the panel's account (REQ-UI-BUILD-BAR).
+  - **Visibility.** The panel is shown whenever the game is being played. Unlike the selection panel it has no empty state (REQ-UI-EMPTY-SELECTION): every context has rows, so there is never nothing to show.
+  - **Collapsing.** Clicking anywhere on the panel's header (REQ-UI-CONTROLS-CARD) toggles the panel between **expanded** and **collapsed**. Collapsed, it shows its header alone, keeping the context name visible and the header clickable so the panel can be expanded again; expanded, it shows the header followed by every row of the current context. The panel starts **expanded**. Changing context does not change the collapsed state: a panel collapsed in one context stays collapsed in the next, and its header updates in place. The collapsed state is presentation-only — it is not a player command, never enters the replay stream, and has no effect on the simulation. It persists for as long as the application runs, including across a restart from the escape menu (REQ-UI-GAME-MENU), and is not saved to disk.
+  - **Overlay behavior.** As for the build button bar and the selection panel (REQ-UI-BUILD-BAR, REQ-UI-SELECTION-PANEL): the panel occludes the strip of the game world it covers; the world view itself keeps its full extent and the view's scrolling, ghost rendering, and tile geometry are unaffected. It is drawn above the pause and deconstruct vignettes (REQ-UI-PAUSE-BORDER, REQ-UI-DECONSTRUCT-BORDER), which keep their full left-hand band underneath it, and below the modal dim (REQ-UI-MODAL-DIM), which covers the entire game window including the panel.
+  - **Input.** Mouse events over the panel are consumed by the panel and never reach the game world: hovering it shows no builder-mode ghost at the tile beneath, and clicking it neither places a building nor changes the selection. Right-clicking the panel does not exit builder mode (REQ-BLD-BUILDER-MODE) or cancel a belt drag (REQ-BLD-BELT-DRAG). The only control the panel itself offers is the header click that collapses and expands it.
+- REQ-UI-CONTROLS-CARD: **Card structure.** The panel is a card with two parts, top to bottom:
+  - **Header** — always shown, and the panel's only interactive element (REQ-UI-CONTROLS-PANEL). It holds a colored context dot on the left, the context's name beside it in upper case, and, for contexts that define one, a **detail suffix** separated by a middle dot (`BUILD MODE · Assembler`). The name and detail per context are given in REQ-UI-CONTROLS-CONTENT.
+  - **Rows** — one per available control, shown only while the panel is expanded. Each row is one or more **key badges** on the left — the key or mouse button drawn as a small bordered chip — and a **label** beside them naming what it does. An action reachable two ways carries both badges in the same row (`RMB` `Q` — Exit placement) rather than occupying two rows. A row whose action leaves the current mode is drawn with the destructive badge styling, distinguishing it from the rows that act within the mode. No row is ever drawn greyed or otherwise disabled: a control the player cannot currently use is not shown at all (REQ-UI-CONTROLS-ACCURACY).
+
+  The rows that are live in every context (REQ-UI-CONTROLS-CONTENT) are shown last, under a divider and the caption `ALWAYS AVAILABLE`. This holds in every context including the General one, which has context rows of its own above the divider like any other, so the card is read the same way wherever the player is.
+- REQ-UI-CONTROLS-CONTENT: **Content catalog.** The control context follows from the active build mode and the selection alone. Build modes are mutually exclusive (REQ-BLD-BUILDER-MODE), so exactly one context applies at any moment:
+
+  | Context | When | Header name | Header detail |
+  |---|---|---|---|
+  | General | no build mode active, nothing selected | `GENERAL` | — |
+  | Selection | no build mode active, at least one object selected | `SELECTION` | `<n> buildings` or `<n> objects` |
+  | Build | builder mode active (REQ-BLD-BUILDER-MODE) | `BUILD MODE` | the building type's name |
+  | Blueprint | blueprint placement mode active (REQ-UI-BLUEPRINT-MODE) | `BLUEPRINT MODE` | the blueprint's name, or `Temporary` for a temporary blueprint (REQ-UI-BLUEPRINT-TEMP) |
+  | Deconstruct | deconstruct mode active (REQ-UI-DECONSTRUCT-BUTTON) | `DECONSTRUCT MODE` | — |
+
+  The Selection context's detail counts the selection and names its category (REQ-UI-SELECTION-CATEGORIES): `<n> buildings` for a building selection, `<n> objects` for a field selection, in the singular at a count of one. The Build and Blueprint contexts show **the same rows** and differ only in their header.
+
+  **Always-available rows**, shown in every context:
+
+  | Badges | Label | Shown |
+  |---|---|---|
+  | `A` `D` | Move | always |
+  | `W` `S` | Game speed | always |
+  | `Space` | Toggle pause | always |
+  | `V` | Paste last | only while a temporary blueprint exists (REQ-UI-BLUEPRINT-TEMP) |
+  | `Ctrl` `V` | Blueprints | always |
+  | `Esc` | Menu | always |
+
+  **Context rows**, shown above the always-available block:
+
+  | Context | Badges | Label |
+  |---|---|---|
+  | General | `LMB` | Select |
+  | | `LMB` drag | Select area |
+  | | `Q` | Deconstruct mode |
+  | Selection | `LMB` | Select / clear selection |
+  | | `LMB` drag | Select area |
+  | | `Ctrl` `LMB` | Add / remove from selection |
+  | | `Ctrl` `LMB` drag | Add area to selection |
+  | | `Q` | Deconstruct mode |
+  | | `C` | Copy to temporary blueprint |
+  | | `Ctrl` `C` | Create blueprint |
+  | Build, Blueprint | `LMB` | Place |
+  | | `LMB` drag | Place belt line |
+  | | `R` / `Shift` `R` | Rotate |
+  | | `RMB` `Q` | Exit placement |
+  | Deconstruct | `LMB` | Toggle deconstruct |
+  | | `LMB` drag | Deconstruct area |
+  | | `RMB` `Q` | Exit deconstruct mode |
+
+  Four rows are conditional on more than the context, because the binding behind them is:
+  - **`C` / `Ctrl` `C`** are shown only while the selection holds at least one player-placeable building, the condition under which those keys do anything (REQ-UI-HOTKEYS). A selection of ships, defence stations, or debris shows neither.
+  - **`LMB` drag — Place belt line** is shown only in builder mode for the Belt type, the only type placed by dragging (REQ-BLD-BELT-DRAG). Every other builder type and blueprint placement omit the row.
+  - **`RMB` `Q` — Exit placement** splits into two rows **while a belt drag is in progress**, because the two bindings then part company (REQ-BLD-BELT-DRAG): `RMB` reads **Cancel belt line** and cancels the drag while leaving builder mode active, and `Q` reads **Exit placement** and leaves the mode outright.
+  - **`LMB` — Place** reads **Apply settings** instead whenever the ghost under the cursor resolves to a configuration transfer (REQ-UI-BLUEPRINT-TRANSFER) — a single-building blueprint hovering a same-type building of a configurable type, which is the case in which clicking hands over settings rather than placing anything. A blueprint holding more than one building keeps the `Place` label, since its click both places and transfers (REQ-UI-BLUEPRINT-PLACE).
+- REQ-UI-CONTROLS-ACCURACY: **The panel never advertises a binding that would do nothing.** Every row shown must, if triggered in the situation the panel is showing it in, have the effect its label names; a binding that is inert in the current context is omitted rather than shown greyed (REQ-UI-CONTROLS-CARD). The relation holds in one direction only: the panel may omit a binding that is available, and deliberately does so in three cases:
+  - **Build hotkeys** (REQ-UI-HOTKEYS) are live in every context, but are advertised on the build buttons' badges (REQ-UI-BUILD-COST) instead of taking eleven rows in every context of this panel.
+  - **`C` and `Ctrl` `C`** are omitted from the Build, Blueprint, and Deconstruct contexts even though a selection surviving into a build mode keeps them working. They belong to the Selection context, and repeating them in every mode would defeat the panel's purpose of showing what the player's current situation affords.
+  - **`Ctrl` `LMB` and `Ctrl` `LMB` drag** work with nothing selected — they select the object under the cursor much as a plain click would — but are shown only in the Selection context. "Add / remove from selection" names an operation on a selection, and there is none to operate on until something is selected; the plain `LMB` row already covers what the gesture does before then.
+  - **`F3` and `F4`** (REQ-UI-DEBUG-DRAW) are development controls rather than player controls and appear in no context.
+
+  This asymmetry between what is available and what is shown is why the two are separate questions in the implementation, and why the tests assert that a resolvable input is *available* rather than that it is displayed.
+
 ### Blueprints
 
 Blueprints occupy no permanent screen space. They are saved with **Ctrl+C** from the current selection (REQ-UI-BLUEPRINT-CREATE) and picked for placement from the blueprint selection dialog, opened with **Ctrl+V** (REQ-UI-BLUEPRINT-DIALOG). The unmodified **C** and **V** keys are the throwaway counterparts of the same two gestures: they capture and re-place a single unnamed temporary blueprint that is never saved and never listed (REQ-UI-BLUEPRINT-TEMP). Blueprints have no widget on the game screen at all. (The ship layout blueprint panel of the layout configuration dialog, REQ-MOD-UI-BLUEPRINT-PANEL, is a separate feature and is unaffected.)

src/lib/core/BuildModeController.cpp

@@ -72,6 +72,7 @@ void BuildModeController::enterMode(BuildMode mode)
             std::make_shared<BuilderModeExitedEvent>());
         break;
     case BuildMode::Blueprint:
+        m_hoveredGhostIsTransfer = false;
         EventManager::getInstance()->sendEventImmediately(
             std::make_shared<BlueprintModeExitedEvent>());
         break;
@@ -249,6 +250,16 @@ void BuildModeController::setBlueprintGhostTile(QPoint tile)
     m_blueprintGhostTile = tile;
 }
 
+bool BuildModeController::isHoveredGhostTransfer() const
+{
+    return m_hoveredGhostIsTransfer;
+}
+
+void BuildModeController::setHoveredGhostTransfer(bool transfer)
+{
+    m_hoveredGhostIsTransfer = transfer;
+}
+
 const std::optional<BuildingId>&
 BuildModeController::getDeconstructHoverBuildingId() const
 {

src/lib/core/BuildModeController.h

@@ -95,6 +95,15 @@ public:
     QPoint           getBlueprintGhostTile() const;
     void             setBlueprintGhostTile(QPoint tile);
 
+    // Whether the ghost under the cursor would hand its settings to the building
+    // already there rather than place anything (REQ-UI-BLUEPRINT-TRANSFER). Classifying
+    // it needs the factory state, so the caller resolves it and stores the answer here,
+    // as with setGhostValidity. Kept here rather than recomputed per reader so the
+    // click, the ghost's colour, and the controls panel cannot disagree about what the
+    // cursor is over.
+    bool isHoveredGhostTransfer() const;
+    void setHoveredGhostTransfer(bool transfer);
+
     // --- deconstruct mode -----------------------------------------------------
     const std::optional<BuildingId>& getDeconstructHoverBuildingId() const;
     void setDeconstructHoverBuildingId(std::optional<BuildingId> id);
@@ -118,6 +127,7 @@ private:
 
     Blueprint m_blueprint;
     QPoint    m_blueprintGhostTile;
+    bool      m_hoveredGhostIsTransfer = false;
 
     std::optional<BuildingId> m_deconstructHoverBuildingId;
 };

src/lib/core/CMakeLists.txt

@@ -16,8 +16,10 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/TunnelCompletion.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCoordinates.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCamera.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanelPlacement.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SelectionController.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildModeController.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlAction.h
     PARENT_SCOPE
 )
 
@@ -31,8 +33,10 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/TunnelCompletion.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCoordinates.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldCamera.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanelPlacement.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/SelectionController.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildModeController.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlAction.cpp
     PARENT_SCOPE
 )
 

src/lib/core/ControlAction.cpp

@@ -0,0 +1,263 @@
+#include "ControlAction.h"
+
+namespace
+{
+
+// A binding that a belt drag can take over. Availability is a property of the action,
+// but a binding can be claimed by a different action while a gesture is in progress:
+// right-click cancels the drag instead of leaving builder mode (REQ-BLD-BELT-DRAG), so
+// ExitMode's right-click drops out and it is left with Q alone.
+enum class BindingCondition
+{
+    Always,
+    NotDraggingBelt
+};
+
+struct KeyBindingEntry
+{
+    ControlAction         action;
+    int                   key;
+    // Shown on the badge, and Ctrl additionally participates in matching. Every other
+    // modifier is display only -- see resolveKeyAction.
+    Qt::KeyboardModifiers modifiers;
+};
+
+struct MouseBindingEntry
+{
+    ControlAction    action;
+    MouseBinding     binding;
+    BindingCondition condition;
+};
+
+// Resolution is first-match-wins over these tables, so an entry that must beat another
+// on the same input is listed above it -- CancelBeltLine before ExitMode on the right
+// mouse button. Everything else is disjoint by availability.
+const KeyBindingEntry KEY_BINDINGS[] = {
+    {ControlAction::Move,             Qt::Key_A,      Qt::NoModifier},
+    {ControlAction::Move,             Qt::Key_D,      Qt::NoModifier},
+    {ControlAction::GameSpeed,        Qt::Key_W,      Qt::NoModifier},
+    {ControlAction::GameSpeed,        Qt::Key_S,      Qt::NoModifier},
+    {ControlAction::TogglePause,      Qt::Key_Space,  Qt::NoModifier},
+    {ControlAction::CopyTemporary,    Qt::Key_C,      Qt::NoModifier},
+    {ControlAction::CreateBlueprint,  Qt::Key_C,      Qt::ControlModifier},
+    {ControlAction::PasteTemporary,   Qt::Key_V,      Qt::NoModifier},
+    {ControlAction::OpenBlueprints,   Qt::Key_V,      Qt::ControlModifier},
+    // One binding, two badges: Shift picks the rotation direction and is read by the
+    // handler, the way a build hotkey's digit is (REQ-BLD-ROTATE). Both entries match
+    // the same press, and both resolve to the same action, so listing them twice costs
+    // nothing and is what puts "R" and "Shift+R" on the row.
+    {ControlAction::Rotate,           Qt::Key_R,      Qt::NoModifier},
+    {ControlAction::Rotate,           Qt::Key_R,      Qt::ShiftModifier},
+    {ControlAction::EnterDeconstruct, Qt::Key_Q,      Qt::NoModifier},
+    {ControlAction::ExitMode,         Qt::Key_Q,      Qt::NoModifier},
+    {ControlAction::OpenMenu,         Qt::Key_Escape, Qt::NoModifier},
+};
+
+const MouseBindingEntry MOUSE_BINDINGS[] = {
+    {ControlAction::Select,             MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::Place,              MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::ApplySettings,      MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::ToggleDeconstruct,  MouseBinding::LeftClick,     BindingCondition::Always},
+    {ControlAction::SelectArea,         MouseBinding::LeftDrag,      BindingCondition::Always},
+    {ControlAction::PlaceBeltLine,      MouseBinding::LeftDrag,      BindingCondition::Always},
+    {ControlAction::DeconstructArea,    MouseBinding::LeftDrag,      BindingCondition::Always},
+    {ControlAction::AddToSelection,     MouseBinding::CtrlLeftClick, BindingCondition::Always},
+    {ControlAction::AddAreaToSelection, MouseBinding::CtrlLeftDrag,  BindingCondition::Always},
+    {ControlAction::CancelBeltLine,     MouseBinding::RightClick,    BindingCondition::Always},
+    {ControlAction::ExitMode,           MouseBinding::RightClick,    BindingCondition::NotDraggingBelt},
+};
+
+bool isConditionMet(BindingCondition condition, const ControlContext& context)
+{
+    if (condition == BindingCondition::NotDraggingBelt) { return !context.draggingBelt; }
+    return true;
+}
+
+bool isPlacementMode(const ControlContext& context)
+{
+    return context.mode == BuildMode::Builder || context.mode == BuildMode::Blueprint;
+}
+
+std::vector<ControlAction> filterAvailable(const std::vector<ControlAction>& actions,
+                                           const ControlContext& context)
+{
+    std::vector<ControlAction> available;
+    for (ControlAction action : actions)
+    {
+        if (isControlActionAvailable(action, context)) { available.push_back(action); }
+    }
+    return available;
+}
+
+}  // namespace
+
+bool isControlActionAvailable(ControlAction action, const ControlContext& context)
+{
+    switch (action)
+    {
+    case ControlAction::None:
+        return false;
+
+    case ControlAction::Move:
+    case ControlAction::GameSpeed:
+    case ControlAction::TogglePause:
+    case ControlAction::OpenBlueprints:
+    case ControlAction::OpenMenu:
+        return true;
+
+    // Does nothing until something has been captured with C, so it is not offered
+    // before then (REQ-UI-BLUEPRINT-TEMP, REQ-UI-CONTROLS-ACCURACY).
+    case ControlAction::PasteTemporary:
+        return context.temporaryBlueprintExists;
+
+    case ControlAction::Select:
+    case ControlAction::SelectArea:
+    case ControlAction::AddToSelection:
+    case ControlAction::AddAreaToSelection:
+    case ControlAction::EnterDeconstruct:
+        return context.mode == BuildMode::None;
+
+    // Both need something a blueprint can be made of; a selection of ships or debris
+    // leaves them inert (REQ-UI-HOTKEYS).
+    case ControlAction::CopyTemporary:
+    case ControlAction::CreateBlueprint:
+        return context.mode == BuildMode::None && context.placeableBuildingSelected;
+
+    // Place and ApplySettings are the same click; which one it is depends on whether
+    // the ghost under the cursor is a transfer target (REQ-UI-BLUEPRINT-TRANSFER).
+    case ControlAction::Place:
+        return isPlacementMode(context) && !context.hoveredGhostIsTransfer;
+    case ControlAction::ApplySettings:
+        return context.mode == BuildMode::Blueprint && context.hoveredGhostIsTransfer;
+
+    // The only building type placed by dragging (REQ-BLD-BELT-DRAG).
+    case ControlAction::PlaceBeltLine:
+        return context.mode == BuildMode::Builder
+               && context.builderType == BuildingType::Belt;
+
+    case ControlAction::Rotate:
+        return isPlacementMode(context);
+    case ControlAction::CancelBeltLine:
+        return context.draggingBelt;
+    case ControlAction::ExitMode:
+        return context.mode != BuildMode::None;
+
+    case ControlAction::ToggleDeconstruct:
+    case ControlAction::DeconstructArea:
+        return context.mode == BuildMode::Deconstruct;
+    }
+    return false;
+}
+
+std::vector<ControlBinding> getControlActionBindings(ControlAction action,
+                                                     const ControlContext& context)
+{
+    std::vector<ControlBinding> bindings;
+    for (const MouseBindingEntry& entry : MOUSE_BINDINGS)
+    {
+        if (entry.action != action)                    { continue; }
+        if (!isConditionMet(entry.condition, context)) { continue; }
+        ControlBinding binding;
+        binding.isMouse = true;
+        binding.mouse   = entry.binding;
+        bindings.push_back(binding);
+    }
+    for (const KeyBindingEntry& entry : KEY_BINDINGS)
+    {
+        if (entry.action != action) { continue; }
+        ControlBinding binding;
+        binding.key       = entry.key;
+        binding.modifiers = entry.modifiers;
+        bindings.push_back(binding);
+    }
+    return bindings;
+}
+
+ControlContextKind getControlContextKind(const ControlContext& context)
+{
+    switch (context.mode)
+    {
+    case BuildMode::Builder:     return ControlContextKind::Build;
+    case BuildMode::Blueprint:   return ControlContextKind::Blueprint;
+    case BuildMode::Deconstruct: return ControlContextKind::Deconstruct;
+    case BuildMode::None:        break;
+    }
+    return context.selection == ControlSelection::None ? ControlContextKind::General
+                                                       : ControlContextKind::Selection;
+}
+
+std::vector<ControlAction> getContextActions(const ControlContext& context)
+{
+    // The candidates of each context, in the order REQ-UI-CONTROLS-CONTENT lists them,
+    // then filtered by availability.
+    //
+    // The General and Selection lists differ rather than one filtered list serving
+    // both, because the additive-selection rows are an omission and not an
+    // unavailability: Ctrl+click does work with nothing selected, it just picks the
+    // object like a plain click would. "Add / remove from selection" is a row that
+    // means nothing until there is a selection to add to, so it waits for one
+    // (REQ-UI-CONTROLS-ACCURACY permits omitting an available binding).
+    switch (getControlContextKind(context))
+    {
+    case ControlContextKind::Build:
+    case ControlContextKind::Blueprint:
+        return filterAvailable({ControlAction::Place, ControlAction::ApplySettings,
+                                ControlAction::PlaceBeltLine, ControlAction::Rotate,
+                                ControlAction::CancelBeltLine, ControlAction::ExitMode},
+                               context);
+    case ControlContextKind::Deconstruct:
+        return filterAvailable({ControlAction::ToggleDeconstruct,
+                                ControlAction::DeconstructArea, ControlAction::ExitMode},
+                               context);
+    case ControlContextKind::Selection:
+        return filterAvailable({ControlAction::Select, ControlAction::SelectArea,
+                                ControlAction::AddToSelection,
+                                ControlAction::AddAreaToSelection,
+                                ControlAction::EnterDeconstruct,
+                                ControlAction::CopyTemporary,
+                                ControlAction::CreateBlueprint},
+                               context);
+    case ControlContextKind::General:
+        break;
+    }
+    return filterAvailable({ControlAction::Select, ControlAction::SelectArea,
+                            ControlAction::EnterDeconstruct},
+                           context);
+}
+
+std::vector<ControlAction> getAlwaysAvailableActions(const ControlContext& context)
+{
+    return filterAvailable({ControlAction::Move, ControlAction::GameSpeed,
+                            ControlAction::TogglePause, ControlAction::PasteTemporary,
+                            ControlAction::OpenBlueprints, ControlAction::OpenMenu},
+                           context);
+}
+
+ControlAction resolveKeyAction(int key, Qt::KeyboardModifiers modifiers,
+                               const ControlContext& context)
+{
+    // Ctrl distinguishes a chord from the bare key (Ctrl+C is not C); every other
+    // modifier is ignored, so Shift+A still pans and Shift+R still rotates. This is
+    // what the key handler has always done, and matching modifiers exactly instead
+    // would silently drop those presses.
+    const bool controlHeld = (modifiers & Qt::ControlModifier) != 0;
+    for (const KeyBindingEntry& entry : KEY_BINDINGS)
+    {
+        if (entry.key != key) { continue; }
+        const bool entryNeedsControl = (entry.modifiers & Qt::ControlModifier) != 0;
+        if (entryNeedsControl != controlHeld) { continue; }
+        if (isControlActionAvailable(entry.action, context)) { return entry.action; }
+    }
+    return ControlAction::None;
+}
+
+ControlAction resolveMouseAction(MouseBinding binding, const ControlContext& context)
+{
+    for (const MouseBindingEntry& entry : MOUSE_BINDINGS)
+    {
+        if (entry.binding != binding)                        { continue; }
+        if (!isConditionMet(entry.condition, context))       { continue; }
+        if (isControlActionAvailable(entry.action, context)) { return entry.action; }
+    }
+    return ControlAction::None;
+}

src/lib/core/ControlAction.h

@@ -0,0 +1,164 @@
+#pragma once
+
+#include <vector>
+
+#include <Qt>
+
+#include "BuildModeController.h"
+#include "BuildingType.h"
+
+// The single statement of what the player can do right now, and which input does it
+// (REQ-UI-CONTROLS-CONTENT, REQ-UI-CONTROLS-ACCURACY).
+//
+// This file declares actions; it never performs them and it never names them. It knows
+// an action's bindings and the situations in which it does something -- nothing about
+// the simulation, the widgets, the events an action ends up firing, or the words shown
+// to the player. Display text lives in ui/ControlActionText.h, which formats the
+// bindings this hands it, so a badge is derived from the real binding rather than
+// typed beside it.
+//
+// Three readers, all of them consuming this and none of them extending it:
+//
+//  * ControlsPanel calls getContextActions()/getAlwaysAvailableActions() and draws them.
+//  * InputMapper calls resolveKeyAction() and fires the event the action stands for.
+//  * GameWorldView calls resolveMouseAction() and runs the branch it already ran.
+//
+// Two bindings are deliberately absent. Build hotkeys (REQ-UI-HOTKEYS) are advertised
+// on the build buttons instead of in the panel, and InputMapper::getBuildHotkeyLabel
+// already derives their badges from the same table the handler switches on, so they
+// have no drift to fix. F3/F4 are development controls and appear nowhere
+// (REQ-UI-CONTROLS-ACCURACY).
+//
+// When bindings become player-configurable, only the binding tables in the .cpp turn
+// from hard-coded data into loaded data. The actions, the availability rules, the
+// panel, and every handler are unaffected.
+enum class ControlAction
+{
+    None,  // no action is bound to the queried input in the queried context
+
+    // Always available (REQ-UI-CONTROLS-CONTENT).
+    Move,
+    GameSpeed,
+    TogglePause,
+    PasteTemporary,
+    OpenBlueprints,
+    OpenMenu,
+
+    // No build mode active.
+    Select,
+    SelectArea,
+    AddToSelection,
+    AddAreaToSelection,
+    EnterDeconstruct,
+
+    // No build mode active, with something selected.
+    CopyTemporary,
+    CreateBlueprint,
+
+    // Builder and blueprint placement mode.
+    Place,
+    ApplySettings,
+    PlaceBeltLine,
+    Rotate,
+    CancelBeltLine,
+    ExitMode,
+
+    // Deconstruct mode.
+    ToggleDeconstruct,
+    DeconstructArea
+};
+
+// The mouse gestures that carry a binding. Each is a whole gesture rather than a raw
+// event: a drag is one binding, not a press plus a release, because that is the unit
+// the player and the panel both think in. Which events make up the gesture, and the
+// state it runs on, stay with the widget that owns them.
+enum class MouseBinding
+{
+    LeftClick,
+    LeftDrag,
+    CtrlLeftClick,
+    CtrlLeftDrag,
+    RightClick
+};
+
+// Which selection category is held, mirroring REQ-UI-SELECTION-CATEGORIES without
+// depending on SelectionController.
+enum class ControlSelection
+{
+    None,
+    Buildings,
+    FieldObjects
+};
+
+// Which card the panel is showing (REQ-UI-CONTROLS-CONTENT). Named rather than
+// spelled, so the heading text stays a presentation concern.
+enum class ControlContextKind
+{
+    General,
+    Selection,
+    Build,
+    Blueprint,
+    Deconstruct
+};
+
+// Everything the availability rules are allowed to depend on, as a plain snapshot.
+//
+// Taking a snapshot rather than references to the live controllers is what keeps this
+// testable without a world, and it is what stops an action from reaching into the
+// simulation: if a rule needs a fact, the fact is named here and the caller supplies it.
+struct ControlContext
+{
+    BuildMode        mode                      = BuildMode::None;
+    BuildingType     builderType               = BuildingType::Belt;  // while mode == Builder
+    bool             draggingBelt              = false;
+    // A single-building blueprint whose ghost is over a configuration-transfer target,
+    // so clicking hands over settings rather than placing (REQ-UI-BLUEPRINT-TRANSFER).
+    bool             hoveredGhostIsTransfer    = false;
+    ControlSelection selection                 = ControlSelection::None;
+    int              selectionCount            = 0;
+    // At least one selected building is player-placeable, the condition under which
+    // C and Ctrl+C do anything (REQ-UI-HOTKEYS).
+    bool             placeableBuildingSelected = false;
+    bool             temporaryBlueprintExists  = false;
+};
+
+// One input an action answers to, in structured form so the badge can be rendered from
+// it. `modifiers` is what the badge shows; matching is looser than equality, see
+// resolveKeyAction.
+struct ControlBinding
+{
+    bool                  isMouse    = false;
+    MouseBinding          mouse      = MouseBinding::LeftClick;
+    int                   key        = 0;  // Qt::Key_*, when !isMouse
+    Qt::KeyboardModifiers modifiers  = Qt::NoModifier;
+};
+
+// True when triggering the action in this context would do what its label says. The
+// panel shows exactly the available actions, and the resolvers return only available
+// ones, which is REQ-UI-CONTROLS-ACCURACY expressed as one function.
+bool isControlActionAvailable(ControlAction action, const ControlContext& context);
+
+// The inputs an action answers to, in the order the panel should badge them.
+// Context-dependent because a binding can be taken over: while a belt drag is in
+// progress the right mouse button cancels the drag, so ExitMode is left with its key
+// binding alone (REQ-BLD-BELT-DRAG).
+std::vector<ControlBinding> getControlActionBindings(ControlAction action,
+                                                     const ControlContext& context);
+
+// Which card is showing, and the rows it holds -- the context's own, then the block
+// available everywhere (REQ-UI-CONTROLS-CARD). Both lists are already filtered to the
+// available actions and ordered as REQ-UI-CONTROLS-CONTENT lists them.
+ControlContextKind         getControlContextKind(const ControlContext& context);
+std::vector<ControlAction> getContextActions(const ControlContext& context);
+std::vector<ControlAction> getAlwaysAvailableActions(const ControlContext& context);
+
+// The action a key press or a mouse gesture triggers here, or None when the input is
+// unbound in this context. Both return only actions that are available, so a caller can
+// act on the result without re-checking the situation.
+//
+// Rotation direction is not part of the action: R and Shift+R are one Rotate, and the
+// caller reads the modifier for the direction, exactly as the digit of a build hotkey
+// is read from the key. An action with a parameter keeps the parameter at the handler.
+ControlAction resolveKeyAction(int key, Qt::KeyboardModifiers modifiers,
+                               const ControlContext& context);
+ControlAction resolveMouseAction(MouseBinding binding, const ControlContext& context);

src/lib/core/EntityAdmin.h

@@ -28,7 +28,7 @@ public:
     void forEach(Func&& f) const;
 
     template <typename... Ts>
-    bool hasAll(entt::entity entity);
+    bool hasAll(entt::entity entity) const;
 
     template <typename T>
     T& get(entt::entity entity);
@@ -101,7 +101,7 @@ void EntityAdmin::forEach(Func&& f) const
 }
 
 template <typename... Ts>
-bool EntityAdmin::hasAll(entt::entity entity)
+bool EntityAdmin::hasAll(entt::entity entity) const
 {
     return m_registry.all_of<Ts...>(entity);
 }

src/lib/core/FloatingPanelPlacement.cpp

@@ -0,0 +1,76 @@
+#include "FloatingPanelPlacement.h"
+
+#include <algorithm>
+
+int getAvailableBottomPx(const QRect& band, const std::vector<QRect>& occupiedRects,
+                         int leftPx, int rightPx, int marginPx)
+{
+    int bottomPx = band.bottom();
+    for (const QRect& occupied : occupiedRects)
+    {
+        if (occupied.isEmpty())
+        {
+            continue;
+        }
+        // Only what is actually in the way counts: a widget entirely to one side of this
+        // span is not below it, however tall it is.
+        if (occupied.right() < leftPx || occupied.left() > rightPx)
+        {
+            continue;
+        }
+        bottomPx = std::min(bottomPx, occupied.top() - marginPx - 1);
+    }
+    return bottomPx;
+}
+
+PanelSide chooseSide(const QRect& band, const QRect& anchorRect, int widthPx,
+                     int marginPx)
+{
+    // What each side offers: the gap between the anchor and that edge of the band, less
+    // the margin the panel keeps from the anchor.
+    const int roomRightPx = band.right() - anchorRect.right() - marginPx;
+    const int roomLeftPx  = anchorRect.left() - band.left() - marginPx;
+
+    if (roomRightPx >= widthPx)
+    {
+        return PanelSide::Right;
+    }
+    if (roomLeftPx >= widthPx)
+    {
+        return PanelSide::Left;
+    }
+    // Neither side can hold it without covering the selection, so it goes where it
+    // covers the least of it.
+    return (roomRightPx >= roomLeftPx) ? PanelSide::Right : PanelSide::Left;
+}
+
+QRect placeBesideAnchor(const QRect& band, const QRect& anchorRect, PanelSide side,
+                        QSize wantedSize, const std::vector<QRect>& occupiedRects,
+                        int marginPx)
+{
+    const int widthPx = std::min(wantedSize.width(), band.width());
+
+    // Against the anchor on the chosen side, growing away from it: the edge facing the
+    // selection is the one that stays put as the panel's content resizes.
+    int leftPx = (side == PanelSide::Right) ? anchorRect.right() + marginPx + 1
+                                            : anchorRect.left() - marginPx - widthPx;
+    // A panel that does not fit there is pushed back inside the view rather than hanging
+    // off it, which is what puts it over the selection when neither side had room.
+    leftPx = std::min(leftPx, band.right() - widthPx + 1);
+    leftPx = std::max(leftPx, band.left());
+
+    // Only the widgets its own column meets can shorten it.
+    const int bottomPx = getAvailableBottomPx(band, occupiedRects, leftPx,
+                                              leftPx + widthPx - 1, marginPx);
+    const int heightPx =
+        std::min(wantedSize.height(), std::max(0, bottomPx - band.top() + 1));
+
+    // Top-aligned with the anchor, then lifted by however much of it hangs below what is
+    // free. Never above the band: a panel taller than the space left is capped instead,
+    // and scrolls.
+    int topPx = std::max(anchorRect.top(), band.top());
+    topPx     = std::min(topPx, bottomPx - heightPx + 1);
+    topPx     = std::max(topPx, band.top());
+
+    return QRect(leftPx, topPx, widthPx, heightPx);
+}

src/lib/core/FloatingPanelPlacement.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include <vector>
+
+#include <QRect>
+#include <QSize>
+
+// Geometry for the widgets floating over the game world view (REQ-UI-WORLD-SIZE). Their
+// owner places them in one ordered pass, each into the space the earlier ones left free,
+// and these are the rules they place themselves by. Pure geometry -- no widget is
+// involved, which is what lets the rules be tested without a display.
+
+// The lowest bottom edge available to a widget occupying the horizontal span
+// [leftPx, rightPx] inside band: the band's own bottom, or marginPx above the topmost
+// occupied rectangle whose horizontal extent meets that span. A rectangle beside the
+// span is not in the way and does not shorten it (REQ-UI-SELECTION-PANEL,
+// REQ-UI-CONTROLS-PANEL). The result is inclusive, as QRect::bottom() is.
+int getAvailableBottomPx(const QRect& band, const std::vector<QRect>& occupiedRects,
+                         int leftPx, int rightPx, int marginPx);
+
+// Which side of the selection the panel stands on (REQ-UI-SELECTION-PANEL).
+enum class PanelSide
+{
+    Right,
+    Left
+};
+
+// The side a panel widthPx wide takes beside anchorRect: the right of it where it fits
+// within band, otherwise the left, and where it fits on neither, whichever side leaves
+// more room -- the one case in which the panel ends up over the selection
+// (REQ-UI-SELECTION-PANEL). Decided once when the selection starts and kept for as long
+// as it lasts, so a card that grows later never flips the panel across the object.
+PanelSide chooseSide(const QRect& band, const QRect& anchorRect, int widthPx,
+                     int marginPx);
+
+// Where a panel of wantedSize stands beside anchorRect on the given side: separated from
+// it by marginPx and growing away from it, its top edge on the anchor's top edge, pushed
+// inside band and above whatever occupies it. The returned height is short of
+// wantedSize's when there was not enough room, which is the caller's cue to scroll its
+// content (REQ-UI-SELECTION-PANEL).
+QRect placeBesideAnchor(const QRect& band, const QRect& anchorRect, PanelSide side,
+                        QSize wantedSize, const std::vector<QRect>& occupiedRects,
+                        int marginPx);

src/lib/eventsystem/event/CMakeLists.txt

@@ -9,6 +9,7 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/BossWaveUpdatedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoicesAvailableEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/SelectionChangedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/SelectionAnchorChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/GameOverEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/GameResetEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/WinEvent.h
@@ -43,6 +44,7 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/BeamFiredEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/DebugDrawToggledEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/CommandRequestedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/FloatingLayoutInvalidatedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/PlayerCommandsAppliedEvent.h
 	PARENT_SCOPE
 )

src/lib/eventsystem/event/FloatingLayoutInvalidatedEvent.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include "Event.h"
+
+// Asks the owner of the widgets floating over the game world view to re-run its placement
+// pass (see ui/FloatingPanel.h). Published by a floating widget whose content or
+// visibility changed: what space that widget may take depends on the ones placed before
+// it, so it cannot re-place itself alone (REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL,
+// REQ-UI-SELECTION-PANEL). Carries no payload -- the pass re-reads every widget.
+class FloatingLayoutInvalidatedEvent : public Event
+{
+};

src/lib/eventsystem/event/SelectionAnchorChangedEvent.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <QRect>
+
+#include "Event.h"
+
+// Where on the screen the selection that is about to be made sits: the bounds of the one
+// object selected, or of all of them when the selection starts as a multi-selection
+// (REQ-UI-SELECTION-PANEL). The rectangle is in the game world view's own widget
+// coordinates.
+//
+// Published only when a selection *starts* -- a plain click or drag, or an additive one
+// onto an empty selection -- and always immediately before the selection itself. Adding
+// to a selection publishes nothing, which is what leaves the selection panel where it
+// is while the selection grows; and because the rectangle is screen space frozen at that
+// moment, scrolling the view or a selected ship flying off does not move the panel
+// either.
+class SelectionAnchorChangedEvent : public Event
+{
+public:
+    explicit SelectionAnchorChangedEvent(QRect rectPx)
+        : rectPx(rectPx) {}
+
+    const QRect rectPx;
+};

src/test/CMakeLists.txt

@@ -14,8 +14,10 @@ add_files(
     TunnelCompletionTest.cpp
     WorldCoordinatesTest.cpp
     WorldCameraTest.cpp
+    FloatingPanelPlacementTest.cpp
     SelectionControllerTest.cpp
     BuildModeControllerTest.cpp
+    ControlActionTest.cpp
     BuildingTest.cpp
     BuildingConfigTest.cpp
     ShipTest.cpp

src/test/ControlActionTest.cpp

@@ -0,0 +1,328 @@
+#include "catch.hpp"
+
+#include <algorithm>
+#include <vector>
+
+#include "BuildModeController.h"
+#include "BuildingType.h"
+#include "ControlAction.h"
+
+// REQ-UI-CONTROLS-ACCURACY. The panel and the input handling read one table, and these
+// tests are what makes that pay: the round-trip case below fails the moment a row is
+// shown whose binding resolves elsewhere, which is the drift the whole design exists to
+// prevent. Everything here works on action ids -- the display strings live in the ui
+// target and are not what can silently go wrong.
+
+namespace
+{
+
+ControlContext generalContext()
+{
+    return ControlContext();
+}
+
+ControlContext selectionContext(bool placeable = true)
+{
+    ControlContext context;
+    context.selection                 = ControlSelection::Buildings;
+    context.selectionCount            = 3;
+    context.placeableBuildingSelected = placeable;
+    return context;
+}
+
+ControlContext builderContext(BuildingType type)
+{
+    ControlContext context;
+    context.mode        = BuildMode::Builder;
+    context.builderType = type;
+    return context;
+}
+
+ControlContext blueprintContext(bool transfer = false)
+{
+    ControlContext context;
+    context.mode                   = BuildMode::Blueprint;
+    context.hoveredGhostIsTransfer = transfer;
+    return context;
+}
+
+ControlContext deconstructContext()
+{
+    ControlContext context;
+    context.mode = BuildMode::Deconstruct;
+    return context;
+}
+
+// A spread wide enough that every availability rule and every binding condition is
+// exercised by the whole-table properties below.
+std::vector<ControlContext> allContexts()
+{
+    ControlContext beltDragging = builderContext(BuildingType::Belt);
+    beltDragging.draggingBelt   = true;
+
+    ControlContext generalWithBlueprint            = generalContext();
+    generalWithBlueprint.temporaryBlueprintExists  = true;
+
+    ControlContext fieldSelection      = selectionContext(false);
+    fieldSelection.selection           = ControlSelection::FieldObjects;
+
+    return {generalContext(),
+            generalWithBlueprint,
+            selectionContext(),
+            fieldSelection,
+            builderContext(BuildingType::Belt),
+            builderContext(BuildingType::Assembler),
+            beltDragging,
+            blueprintContext(false),
+            blueprintContext(true),
+            deconstructContext()};
+}
+
+std::vector<ControlAction> shownActions(const ControlContext& context)
+{
+    std::vector<ControlAction> actions = getContextActions(context);
+    const std::vector<ControlAction> always = getAlwaysAvailableActions(context);
+    actions.insert(actions.end(), always.begin(), always.end());
+    return actions;
+}
+
+bool contains(const std::vector<ControlAction>& actions, ControlAction action)
+{
+    return std::find(actions.begin(), actions.end(), action) != actions.end();
+}
+
+}  // namespace
+
+TEST_CASE("ControlAction: every shown row is available", "[controls]")
+{
+    for (const ControlContext& context : allContexts())
+    {
+        for (ControlAction action : shownActions(context))
+        {
+            REQUIRE(isControlActionAvailable(action, context));
+        }
+    }
+}
+
+TEST_CASE("ControlAction: no row is shown twice", "[controls]")
+{
+    for (const ControlContext& context : allContexts())
+    {
+        std::vector<ControlAction> actions = shownActions(context);
+        std::vector<ControlAction> unique  = actions;
+        std::sort(unique.begin(), unique.end());
+        unique.erase(std::unique(unique.begin(), unique.end()), unique.end());
+        REQUIRE(unique.size() == actions.size());
+    }
+}
+
+// The core anti-drift property: a row's badges are rendered from its bindings, so every
+// binding a row advertises must actually trigger that row's action in that same context.
+TEST_CASE("ControlAction: every advertised binding resolves back to its own action",
+          "[controls]")
+{
+    for (const ControlContext& context : allContexts())
+    {
+        for (ControlAction action : shownActions(context))
+        {
+            const std::vector<ControlBinding> bindings =
+                getControlActionBindings(action, context);
+            REQUIRE_FALSE(bindings.empty());
+
+            for (const ControlBinding& binding : bindings)
+            {
+                if (binding.isMouse)
+                {
+                    REQUIRE(resolveMouseAction(binding.mouse, context) == action);
+                }
+                else
+                {
+                    REQUIRE(resolveKeyAction(binding.key, binding.modifiers, context)
+                            == action);
+                }
+            }
+        }
+    }
+}
+
+// The other direction: an input that resolves to something must resolve to an action
+// that is actually available there, so no input can trigger a no-op. This is weaker
+// than "must be a shown row" on purpose -- a context may omit an available binding
+// (Ctrl+click in the General context), which REQ-UI-CONTROLS-ACCURACY permits; what it
+// may never do is act on an unavailable one.
+TEST_CASE("ControlAction: every resolvable input is available", "[controls]")
+{
+    const std::vector<MouseBinding> mouseBindings = {
+        MouseBinding::LeftClick, MouseBinding::LeftDrag, MouseBinding::CtrlLeftClick,
+        MouseBinding::CtrlLeftDrag, MouseBinding::RightClick};
+
+    for (const ControlContext& context : allContexts())
+    {
+        for (MouseBinding binding : mouseBindings)
+        {
+            const ControlAction action = resolveMouseAction(binding, context);
+            if (action != ControlAction::None)
+            {
+                REQUIRE(isControlActionAvailable(action, context));
+            }
+        }
+
+        const std::vector<int> keys = {Qt::Key_A, Qt::Key_D, Qt::Key_W, Qt::Key_S,
+                                       Qt::Key_Space, Qt::Key_C, Qt::Key_V, Qt::Key_R,
+                                       Qt::Key_Q, Qt::Key_Escape};
+        for (int key : keys)
+        {
+            for (Qt::KeyboardModifiers modifiers :
+                 {Qt::KeyboardModifiers(Qt::NoModifier),
+                  Qt::KeyboardModifiers(Qt::ShiftModifier),
+                  Qt::KeyboardModifiers(Qt::ControlModifier)})
+            {
+                const ControlAction action = resolveKeyAction(key, modifiers, context);
+                if (action != ControlAction::None)
+                {
+                    REQUIRE(isControlActionAvailable(action, context));
+                }
+            }
+        }
+    }
+}
+
+TEST_CASE("ControlAction: contexts are named by mode and selection", "[controls]")
+{
+    REQUIRE(getControlContextKind(generalContext()) == ControlContextKind::General);
+    REQUIRE(getControlContextKind(selectionContext()) == ControlContextKind::Selection);
+    REQUIRE(getControlContextKind(builderContext(BuildingType::Belt))
+            == ControlContextKind::Build);
+    REQUIRE(getControlContextKind(blueprintContext()) == ControlContextKind::Blueprint);
+    REQUIRE(getControlContextKind(deconstructContext())
+            == ControlContextKind::Deconstruct);
+}
+
+TEST_CASE("ControlAction: Q enters deconstruct mode, or leaves the active one",
+          "[controls]")
+{
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, generalContext())
+            == ControlAction::EnterDeconstruct);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, selectionContext())
+            == ControlAction::EnterDeconstruct);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, builderContext(BuildingType::Belt))
+            == ControlAction::ExitMode);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, blueprintContext())
+            == ControlAction::ExitMode);
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, deconstructContext())
+            == ControlAction::ExitMode);
+}
+
+TEST_CASE("ControlAction: Ctrl distinguishes the chords, other modifiers do not",
+          "[controls]")
+{
+    const ControlContext context = selectionContext();
+
+    REQUIRE(resolveKeyAction(Qt::Key_C, Qt::NoModifier, context)
+            == ControlAction::CopyTemporary);
+    REQUIRE(resolveKeyAction(Qt::Key_C, Qt::ControlModifier, context)
+            == ControlAction::CreateBlueprint);
+    REQUIRE(resolveKeyAction(Qt::Key_V, Qt::ControlModifier, context)
+            == ControlAction::OpenBlueprints);
+
+    // Shift+A must still pan, as it always has -- matching modifiers exactly instead of
+    // testing Ctrl alone would silently swallow the press.
+    REQUIRE(resolveKeyAction(Qt::Key_A, Qt::ShiftModifier, context) == ControlAction::Move);
+    REQUIRE(resolveKeyAction(Qt::Key_R, Qt::ShiftModifier, blueprintContext())
+            == ControlAction::Rotate);
+}
+
+TEST_CASE("ControlAction: a transfer target turns the click into Apply settings",
+          "[controls]")
+{
+    const ControlContext plain    = blueprintContext(false);
+    const ControlContext transfer = blueprintContext(true);
+
+    REQUIRE(resolveMouseAction(MouseBinding::LeftClick, plain) == ControlAction::Place);
+    REQUIRE(resolveMouseAction(MouseBinding::LeftClick, transfer)
+            == ControlAction::ApplySettings);
+
+    REQUIRE(contains(getContextActions(plain), ControlAction::Place));
+    REQUIRE_FALSE(contains(getContextActions(plain), ControlAction::ApplySettings));
+    REQUIRE(contains(getContextActions(transfer), ControlAction::ApplySettings));
+    REQUIRE_FALSE(contains(getContextActions(transfer), ControlAction::Place));
+}
+
+TEST_CASE("ControlAction: a belt drag takes the right mouse button from ExitMode",
+          "[controls]")
+{
+    ControlContext dragging   = builderContext(BuildingType::Belt);
+    dragging.draggingBelt     = true;
+    const ControlContext idle = builderContext(BuildingType::Belt);
+
+    REQUIRE(resolveMouseAction(MouseBinding::RightClick, idle) == ControlAction::ExitMode);
+    REQUIRE(resolveMouseAction(MouseBinding::RightClick, dragging)
+            == ControlAction::CancelBeltLine);
+
+    // Q still leaves the mode outright while the drag runs, so ExitMode stays shown --
+    // with its right-click badge dropped, since the button now means something else.
+    REQUIRE(resolveKeyAction(Qt::Key_Q, Qt::NoModifier, dragging) == ControlAction::ExitMode);
+
+    const std::vector<ControlBinding> idleBindings =
+        getControlActionBindings(ControlAction::ExitMode, idle);
+    const std::vector<ControlBinding> dragBindings =
+        getControlActionBindings(ControlAction::ExitMode, dragging);
+    REQUIRE(idleBindings.size() == 2);
+    REQUIRE(dragBindings.size() == 1);
+    REQUIRE_FALSE(dragBindings.front().isMouse);
+}
+
+TEST_CASE("ControlAction: dragging a line is offered for belts only", "[controls]")
+{
+    REQUIRE(resolveMouseAction(MouseBinding::LeftDrag, builderContext(BuildingType::Belt))
+            == ControlAction::PlaceBeltLine);
+    REQUIRE(resolveMouseAction(MouseBinding::LeftDrag,
+                               builderContext(BuildingType::Assembler))
+            == ControlAction::None);
+    REQUIRE(resolveMouseAction(MouseBinding::LeftDrag, blueprintContext())
+            == ControlAction::None);
+}
+
+TEST_CASE("ControlAction: blueprint keys are offered only where they do something",
+          "[controls]")
+{
+    // V does nothing until C has captured something (REQ-UI-BLUEPRINT-TEMP).
+    ControlContext withBlueprint                  = generalContext();
+    withBlueprint.temporaryBlueprintExists        = true;
+    REQUIRE_FALSE(contains(shownActions(generalContext()), ControlAction::PasteTemporary));
+    REQUIRE(contains(shownActions(withBlueprint), ControlAction::PasteTemporary));
+    REQUIRE(resolveKeyAction(Qt::Key_V, Qt::NoModifier, generalContext())
+            == ControlAction::None);
+
+    // C and Ctrl+C need a selection holding something placeable (REQ-UI-HOTKEYS).
+    ControlContext fieldSelection = selectionContext(false);
+    fieldSelection.selection      = ControlSelection::FieldObjects;
+    REQUIRE(contains(getContextActions(selectionContext()), ControlAction::CopyTemporary));
+    REQUIRE_FALSE(contains(getContextActions(fieldSelection), ControlAction::CopyTemporary));
+    REQUIRE(resolveKeyAction(Qt::Key_C, Qt::NoModifier, fieldSelection)
+            == ControlAction::None);
+
+    // Ctrl+V opens the dialog whatever is going on (REQ-UI-HOTKEYS).
+    for (const ControlContext& context : allContexts())
+    {
+        REQUIRE(resolveKeyAction(Qt::Key_V, Qt::ControlModifier, context)
+                == ControlAction::OpenBlueprints);
+    }
+}
+
+TEST_CASE("ControlAction: selection rows appear only once something is selected",
+          "[controls]")
+{
+    const std::vector<ControlAction> general   = getContextActions(generalContext());
+    const std::vector<ControlAction> selection = getContextActions(selectionContext());
+
+    REQUIRE(contains(general, ControlAction::Select));
+    REQUIRE(contains(general, ControlAction::EnterDeconstruct));
+    REQUIRE_FALSE(contains(general, ControlAction::AddToSelection));
+    REQUIRE_FALSE(contains(general, ControlAction::CreateBlueprint));
+
+    REQUIRE(contains(selection, ControlAction::AddToSelection));
+    REQUIRE(contains(selection, ControlAction::AddAreaToSelection));
+    REQUIRE(contains(selection, ControlAction::CreateBlueprint));
+    REQUIRE(contains(selection, ControlAction::EnterDeconstruct));
+}

src/test/FloatingPanelPlacementTest.cpp

@@ -0,0 +1,156 @@
+#include "catch.hpp"
+
+#include <vector>
+
+#include <QRect>
+
+#include "FloatingPanelPlacement.h"
+
+// The band every case below places into: 1000x600, so a bottom edge of 599.
+static QRect makeBand()
+{
+    return QRect(0, 0, 1000, 600);
+}
+
+static const int kMarginPx = 8;
+
+TEST_CASE("With nothing in the way a widget may use the whole band", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: the band's own bottom is the limit when no other floating
+    // widget has been placed yet.
+    REQUIRE(getAvailableBottomPx(makeBand(), {}, 0, 999, kMarginPx) == 599);
+}
+
+TEST_CASE("A widget in the same column pushes the bottom above it", "[layout]")
+{
+    // The build button bar sitting at the bottom center leaves the space above it, less
+    // the margin kept between the two (REQ-UI-BUILD-BAR).
+    const std::vector<QRect> occupied = { QRect(400, 520, 200, 72) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 350, 650, kMarginPx) == 511);
+}
+
+TEST_CASE("A widget beside the column does not shorten it", "[layout]")
+{
+    // The controls panel in the bottom-left corner is not in the way of a panel standing
+    // at the right edge, however tall it is (REQ-UI-CONTROLS-PANEL).
+    const std::vector<QRect> occupied = { QRect(0, 100, 200, 499) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 700, 999, kMarginPx) == 599);
+
+    // Touching columns do count as meeting: the panel starts exactly where the widget
+    // ends, which is an overlap of one pixel.
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 199, 999, kMarginPx) == 91);
+}
+
+TEST_CASE("The topmost widget in the column decides", "[layout]")
+{
+    // Several widgets meet the column: the one that reaches highest is the binding one,
+    // whatever order they are given in.
+    const std::vector<QRect> occupied = { QRect(400, 520, 200, 72),
+                                          QRect(0, 300, 500, 299),
+                                          QRect(900, 560, 100, 40) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 450, 550, kMarginPx) == 291);
+}
+
+TEST_CASE("An empty rectangle occupies nothing", "[layout]")
+{
+    // A floating widget that is hidden contributes a null rect rather than being left
+    // out of the pass.
+    const std::vector<QRect> occupied = { QRect(), QRect(400, 520, 200, 0) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 0, 999, kMarginPx) == 599);
+}
+
+TEST_CASE("A widget filling the column leaves nothing", "[layout]")
+{
+    // The caller is expected to notice that the space left is not positive rather than
+    // being handed a floor of its own.
+    const std::vector<QRect> occupied = { QRect(0, 0, 1000, 600) };
+    REQUIRE(getAvailableBottomPx(makeBand(), occupied, 0, 999, kMarginPx) == -9);
+}
+
+// ---------------------------------------------------------------------------
+// Which side of the selection the panel takes
+// ---------------------------------------------------------------------------
+
+TEST_CASE("The panel stands to the right of the selection where it fits", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: right of the anchor is the first choice.
+    REQUIRE(chooseSide(makeBand(), QRect(100, 100, 60, 60), 300, kMarginPx)
+            == PanelSide::Right);
+}
+
+TEST_CASE("The panel goes left when the right cannot hold it", "[layout]")
+{
+    // A selection near the right edge leaves 100 px there, not enough for a 300 px
+    // panel, and the left is wide open.
+    REQUIRE(chooseSide(makeBand(), QRect(880, 100, 20, 60), 300, kMarginPx)
+            == PanelSide::Left);
+}
+
+TEST_CASE("Fitting on neither side, the panel takes the roomier one", "[layout]")
+{
+    // A bounding box spanning most of the view: 192 px free on the left, 92 on the
+    // right, and a 300 px panel fits in neither. It covers as little as it can.
+    REQUIRE(chooseSide(makeBand(), QRect(200, 100, 700, 200), 300, kMarginPx)
+            == PanelSide::Left);
+    REQUIRE(chooseSide(makeBand(), QRect(100, 100, 700, 200), 300, kMarginPx)
+            == PanelSide::Right);
+}
+
+// ---------------------------------------------------------------------------
+// Where it then stands
+// ---------------------------------------------------------------------------
+
+TEST_CASE("The panel sits beside the anchor with its top edges aligned", "[layout]")
+{
+    // REQ-UI-SELECTION-PANEL: separated by the margin, growing away from the selection,
+    // top edge on the anchor's top edge.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 120, 60, 60),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(168, 120, 300, 200));
+
+    const QRect placedLeft = placeBesideAnchor(makeBand(), QRect(500, 120, 60, 60),
+                                               PanelSide::Left, QSize(300, 200), {},
+                                               kMarginPx);
+    REQUIRE(placedLeft == QRect(192, 120, 300, 200));
+}
+
+TEST_CASE("A panel that would hang below the view is lifted", "[layout]")
+{
+    // Top-aligning with a selection low in the view would put the panel's bottom past
+    // the band, so it rises until it fits rather than overrunning it.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 500, 60, 60),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(168, 400, 300, 200));
+}
+
+TEST_CASE("A panel standing over another widget rises above it", "[layout]")
+{
+    // The controls panel in the bottom-left is in the way of a panel placed to the left
+    // of a selection: it clears the top of it by the margin (REQ-UI-CONTROLS-PANEL).
+    const std::vector<QRect> occupied = { QRect(0, 300, 260, 300) };
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(500, 250, 60, 60),
+                                           PanelSide::Left, QSize(300, 200), occupied,
+                                           kMarginPx);
+    REQUIRE(placed == QRect(192, 92, 300, 200));
+}
+
+TEST_CASE("A panel taller than the space left is capped", "[layout]")
+{
+    // Capping is the caller's cue to scroll: it asked for 700 and got what there was.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 100, 60, 60),
+                                           PanelSide::Right, QSize(300, 700), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(168, 0, 300, 600));
+}
+
+TEST_CASE("A panel that fits on neither side is pushed inside the view", "[layout]")
+{
+    // The one case where it covers part of the selection (REQ-UI-SELECTION-PANEL): it
+    // stands as far from the anchor as the band allows, not off the edge of it.
+    const QRect placed = placeBesideAnchor(makeBand(), QRect(100, 100, 700, 200),
+                                           PanelSide::Right, QSize(300, 200), {},
+                                           kMarginPx);
+    REQUIRE(placed == QRect(700, 100, 300, 200));
+}

src/ui/BlueprintLibrary.cpp

@@ -39,6 +39,11 @@ bool BlueprintLibrary::getCanCaptureSelection() const
     return selectionHasPlaceableBuilding(*m_sim, m_selectedBuildingIds);
 }
 
+bool BlueprintLibrary::getHasTemporaryBlueprint() const
+{
+    return m_temporaryBlueprint.has_value();
+}
+
 void BlueprintLibrary::saveSelectionAs(const QString& name)
 {
     Blueprint blueprint = createBlueprintFromSelection();

src/ui/BlueprintLibrary.h

@@ -44,6 +44,11 @@ public:
     // (REQ-UI-BLUEPRINT-CREATE).
     bool getCanCaptureSelection() const;
 
+    // True once C has captured something -- the condition under which V does anything
+    // (REQ-UI-BLUEPRINT-TEMP), and so the condition under which the controls panel
+    // offers it (REQ-UI-CONTROLS-ACCURACY).
+    bool getHasTemporaryBlueprint() const;
+
     // Captures the current selection under the given name and appends it to the list.
     // Silently does nothing when nothing player-placeable is selected.
     void saveSelectionAs(const QString& name);

src/ui/BuildButtonBar.cpp

@@ -24,6 +24,7 @@
 #include "DisplayName.h"
 #include "EventManager.h"
 #include "ExitBuilderModeRequestedEvent.h"
+#include "FloatingLayoutInvalidatedEvent.h"
 #include "IconCaption.h"
 #include "InputMapper.h"
 #include "ItemIconCache.h"
@@ -270,15 +271,25 @@ BuildButtonBar::~BuildButtonBar()
     unregisterForEvents();
 }
 
-void BuildButtonBar::anchorTo(const QRect& worldViewRect)
+void BuildButtonBar::placeIn(const QRect& viewRect,
+                             const std::vector<QRect>& /*occupiedRects*/)
 {
-    m_viewRect = worldViewRect;
-    recenter();
-}
+    if (viewRect.isNull())
+    {
+        return;
+    }
+    // The layout drops hidden buttons from its size hint, but only once it has been
+    // re-run: an unlock changes which buttons are shown, and Qt would not get around to
+    // it before the bar is measured here.
+    layout()->activate();
 
-int BuildButtonBar::getStripHeightPx() const
-{
-    return height() + kBottomMarginPx;
+    const QSize barSize = sizeHint();
+    // Centered, except that a bar wider than the view stays flush with its left edge
+    // rather than hanging off both sides.
+    const int x = qMax(viewRect.left(),
+                       viewRect.left() + (viewRect.width() - barSize.width()) / 2);
+    const int y = viewRect.bottom() - kBottomMarginPx - barSize.height() + 1;
+    setGeometry(QRect(QPoint(x, y), barSize));
 }
 
 void BuildButtonBar::clearActiveButton()
@@ -328,29 +339,11 @@ void BuildButtonBar::updateVisibility()
     {
         m_buttons[i]->setVisible(m_sim->isBuildingUnlocked(m_types[i]));
     }
-    // A hidden button leaves the row, so the bar has to take up its new width and
-    // re-center on it (REQ-UI-BUILD-BAR).
-    recenter();
-}
-
-void BuildButtonBar::recenter()
-{
-    if (m_viewRect.isNull())
-    {
-        return;
-    }
-    // The layout drops hidden buttons from its size hint, but only once it has been
-    // re-run: updateVisibility() calls this straight after setVisible(), before Qt
-    // would get around to it on its own.
-    layout()->activate();
-
-    const QSize barSize = sizeHint();
-    // Centered, except that a bar wider than the view stays flush with its left edge
-    // rather than hanging off both sides.
-    const int x = qMax(m_viewRect.left(),
-                       m_viewRect.left() + (m_viewRect.width() - barSize.width()) / 2);
-    const int y = m_viewRect.bottom() - kBottomMarginPx - barSize.height() + 1;
-    setGeometry(QRect(QPoint(x, y), barSize));
+    // A hidden button leaves the row, so the bar takes up a new width and has to be
+    // re-centered on it -- and the widgets that keep clear of the bar have to be placed
+    // against that new rect too, so the whole pass is re-run (REQ-UI-BUILD-BAR).
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<FloatingLayoutInvalidatedEvent>());
 }
 
 void BuildButtonBar::onBuildButton(int index)

src/ui/BuildButtonBar.h

@@ -15,6 +15,7 @@
 #include "BuildingType.h"
 #include "DeconstructModeChangedEvent.h"
 #include "EventHandler.h"
+#include "FloatingPanel.h"
 #include "GameConfig.h"
 #include "UnlockedBuildingsChangedEvent.h"
 
@@ -24,10 +25,12 @@ class BuildingIconCache;
 class ItemIconCache;
 
 // The build menu: one horizontal row of build buttons floating over the game world
-// view (REQ-UI-BUILD-BAR). The bar is sized to its buttons; its owner hands it the
-// world view's rect through anchorTo() and it centers itself along that rect's
-// bottom edge.
+// view (REQ-UI-BUILD-BAR). The bar is sized to its buttons and centers itself along the
+// bottom edge of the rect its owner places it in. It is placed first of the floating
+// widgets and so takes the space it wants outright: nothing ever moves it aside, and the
+// widgets placed after it keep out of its way instead.
 class BuildButtonBar : public QWidget,
+                       public FloatingPanel,
                        public CombinedEventHandler<BuilderModeExitedEvent,
                                                    DeconstructModeChangedEvent,
                                                    BuildHotkeyPressedEvent,
@@ -45,15 +48,11 @@ public:
                    QWidget* parent = nullptr);
     ~BuildButtonBar() override;
 
-    // Centers the bar along the bottom edge of the game world view's rect, given in
-    // the bar's parent coordinates (REQ-UI-BUILD-BAR). The rect is remembered, so a
-    // re-center later driven by an unlock needs no second call from the owner.
-    void anchorTo(const QRect& worldViewRect);
-
-    // Height of the strip the bar occupies along the bottom of the world view: its own
-    // height plus the margin below it. The selection panel keeps out of this strip, and
-    // the bar never moves for the panel in return (REQ-UI-BUILD-BAR).
-    int getStripHeightPx() const;
+    // Centers the bar along the bottom edge of the game world view's rect, given in the
+    // bar's parent coordinates (REQ-UI-BUILD-BAR). Nothing is occupied yet when the bar
+    // is placed, so it ignores what it is handed there.
+    void placeIn(const QRect& viewRect,
+                 const std::vector<QRect>& occupiedRects) override;
 
     void clearActiveButton();
 
@@ -67,11 +66,6 @@ private:
     // unlock state (REQ-LOCK-BUILDING); a locked building type's button is hidden.
     void updateVisibility();
 
-    // Shrinks the bar to its currently shown buttons and re-centers it in the
-    // anchored rect (REQ-UI-BUILD-BAR). Does nothing until anchorTo() supplied that
-    // rect, so the construction-time call is harmless.
-    void recenter();
-
     void handleEvent(std::shared_ptr<const BuilderModeExitedEvent> event) override;
     void handleEvent(std::shared_ptr<const DeconstructModeChangedEvent> event) override;
     void handleEvent(std::shared_ptr<const BuildHotkeyPressedEvent> event) override;
@@ -91,5 +85,4 @@ private:
     std::map<BuildingType, int>      m_costs;
     std::optional<std::size_t>       m_activeIndex;
     QPushButton*                     m_deconstructButton;
-    QRect                            m_viewRect;
 };

src/ui/CMakeLists.txt

@@ -12,8 +12,12 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldPrimitives.h
     ${CMAKE_CURRENT_SOURCE_DIR}/WorldRenderer.h
     ${CMAKE_CURRENT_SOURCE_DIR}/HeaderBar.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/FloatingPanel.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonBar.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SelectionPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionBounds.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlsPanel.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlActionText.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintLibrary.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSelectionDialog.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutDialog.h
@@ -45,6 +49,9 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/HeaderBar.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BuildButtonBar.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/SelectionPanel.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/SelectionBounds.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlsPanel.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/ControlActionText.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintLibrary.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/BlueprintSelectionDialog.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ShipLayoutDialog.cpp

src/ui/ControlActionText.cpp

@@ -0,0 +1,92 @@
+#include "ControlActionText.h"
+
+#include <QCoreApplication>
+#include <QKeySequence>
+
+namespace
+{
+
+// tr() for a file of free functions. Q_DECLARE_TR_FUNCTIONS expands with access
+// specifiers, so it needs a class rather than a namespace; this struct exists only to
+// carry it and give the strings a single lupdate context.
+struct Strings
+{
+    Q_DECLARE_TR_FUNCTIONS(ControlActionText)
+};
+
+QString getMouseBadge(MouseBinding binding)
+{
+    switch (binding)
+    {
+    case MouseBinding::LeftClick:     return Strings::tr("LMB");
+    case MouseBinding::LeftDrag:      return Strings::tr("LMB drag");
+    case MouseBinding::CtrlLeftClick: return Strings::tr("Ctrl+LMB");
+    case MouseBinding::CtrlLeftDrag:  return Strings::tr("Ctrl+LMB drag");
+    case MouseBinding::RightClick:    return Strings::tr("RMB");
+    }
+    return QString();
+}
+
+}  // namespace
+
+QString getControlBindingBadge(const ControlBinding& binding)
+{
+    if (binding.isMouse) { return getMouseBadge(binding.mouse); }
+
+    // QKeySequence spells the modifiers and the key together and localizes them, which
+    // is what makes this stay correct once keys are rebindable: the chip is generated
+    // from the binding rather than typed next to it.
+    return QKeySequence(binding.key | static_cast<int>(binding.modifiers))
+        .toString(QKeySequence::NativeText);
+}
+
+QString getControlActionLabel(ControlAction action, const ControlContext& context)
+{
+    switch (action)
+    {
+    case ControlAction::None:               return QString();
+    case ControlAction::Move:               return Strings::tr("Move");
+    case ControlAction::GameSpeed:          return Strings::tr("Game speed");
+    case ControlAction::TogglePause:        return Strings::tr("Toggle pause");
+    case ControlAction::PasteTemporary:     return Strings::tr("Paste last");
+    case ControlAction::OpenBlueprints:     return Strings::tr("Blueprints");
+    case ControlAction::OpenMenu:           return Strings::tr("Menu");
+    // A click on empty space clears and a click on an object replaces; naming only the
+    // first would be a half-truth once something is selected.
+    case ControlAction::Select:
+        return context.selection == ControlSelection::None
+                   ? Strings::tr("Select")
+                   : Strings::tr("Select / clear selection");
+    case ControlAction::SelectArea:         return Strings::tr("Select area");
+    case ControlAction::AddToSelection:     return Strings::tr("Add / remove from selection");
+    case ControlAction::AddAreaToSelection: return Strings::tr("Add area to selection");
+    case ControlAction::EnterDeconstruct:   return Strings::tr("Deconstruct mode");
+    case ControlAction::CopyTemporary:      return Strings::tr("Copy to temporary blueprint");
+    case ControlAction::CreateBlueprint:    return Strings::tr("Create blueprint");
+    case ControlAction::Place:              return Strings::tr("Place");
+    case ControlAction::ApplySettings:      return Strings::tr("Apply settings");
+    case ControlAction::PlaceBeltLine:      return Strings::tr("Place belt line");
+    case ControlAction::Rotate:             return Strings::tr("Rotate");
+    case ControlAction::CancelBeltLine:     return Strings::tr("Cancel belt line");
+    case ControlAction::ExitMode:
+        return context.mode == BuildMode::Deconstruct
+                   ? Strings::tr("Exit deconstruct mode")
+                   : Strings::tr("Exit placement");
+    case ControlAction::ToggleDeconstruct:  return Strings::tr("Toggle deconstruct");
+    case ControlAction::DeconstructArea:    return Strings::tr("Deconstruct area");
+    }
+    return QString();
+}
+
+QString getControlContextName(ControlContextKind kind)
+{
+    switch (kind)
+    {
+    case ControlContextKind::General:     return Strings::tr("GENERAL");
+    case ControlContextKind::Selection:   return Strings::tr("SELECTION");
+    case ControlContextKind::Build:       return Strings::tr("BUILD MODE");
+    case ControlContextKind::Blueprint:   return Strings::tr("BLUEPRINT MODE");
+    case ControlContextKind::Deconstruct: return Strings::tr("DECONSTRUCT MODE");
+    }
+    return QString();
+}

src/ui/ControlActionText.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <QString>
+
+#include "ControlAction.h"
+
+// What the player is shown for the actions and bindings declared in ControlAction.h
+// (REQ-UI-CONTROLS-CONTENT). Kept out of lib/core deliberately: that file decides what
+// is available and what triggers it, this one decides what it is called, and only this
+// half is presentation.
+//
+// A badge is rendered from the binding it belongs to rather than written beside it, so
+// what the panel shows on a chip is what the resolver actually matches. When bindings
+// become player-configurable, this is the only place that has to learn to spell a
+// rebound key.
+
+// The chip text for one binding: "Ctrl+V", "LMB drag", "RMB".
+QString getControlBindingBadge(const ControlBinding& binding);
+
+// What the action is called in this context. A few actions are named for their
+// situation rather than their implementation -- one exit action reads "Exit placement"
+// in a placement mode and "Exit deconstruct mode" in deconstruct mode.
+QString getControlActionLabel(ControlAction action, const ControlContext& context);
+
+// The heading, in the upper case the card shows it in (REQ-UI-CONTROLS-CARD).
+QString getControlContextName(ControlContextKind kind);

src/ui/ControlsPanel.cpp

@@ -0,0 +1,340 @@
+#include "ControlsPanel.h"
+
+#include <QFont>
+#include <QFrame>
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QMouseEvent>
+#include <QScrollArea>
+#include <QScrollBar>
+#include <QTimer>
+#include <QVBoxLayout>
+
+#include "ControlActionText.h"
+#include "EventManager.h"
+#include "FloatingLayoutInvalidatedEvent.h"
+#include "FloatingPanelPlacement.h"
+#include "GameWorldView.h"
+#include "selection/SelectionNames.h"
+
+namespace
+{
+
+const int kMarginPx      = 8;   // between the view's edge and the panel
+const int kCardMarginPx  = 8;   // inside the panel, around its content
+const int kHeadingGapPx  = 4;   // between the heading and the rows
+const int kRefreshMs     = 50;  // see the class comment on why this polls
+
+// The panel's border, from the stylesheet below. Spelled out because the stylesheet box
+// is what sets it and asking the style for it before the first show is unreliable.
+const int kBorderPx = 1;
+
+// Separates the heading's name from its detail, e.g. "BUILD MODE * Assembler".
+const QChar kHeadingSeparator(0x00B7);  // U+00B7 MIDDLE DOT
+
+// The upper-case heading and caption are tracked out a little so they read as labels
+// rather than as words. Set on the font because Qt's stylesheets have no letter-spacing
+// property -- writing one there is silently ignored apart from a warning per widget.
+QFont makeSpacedFont(QFont font, bool bold, int pointSizeDelta)
+{
+    font.setBold(bold);
+    if (pointSizeDelta != 0 && font.pointSize() > 0)
+    {
+        font.setPointSize(qMax(1, font.pointSize() + pointSizeDelta));
+    }
+    font.setLetterSpacing(QFont::AbsoluteSpacing, 1.0);
+    return font;
+}
+
+// One row: the chips for the bindings, then what the action is called. Built as a plain
+// widget rather than a class of its own -- it holds no state and answers no questions.
+QWidget* makeRow(ControlAction action, const ControlContext& context, QWidget* parent)
+{
+    QWidget*     row    = new QWidget(parent);
+    QHBoxLayout* layout = new QHBoxLayout(row);
+    layout->setContentsMargins(0, 2, 0, 2);
+    layout->setSpacing(4);
+
+    // Every badge is rendered from the binding the resolver matches, so a chip cannot
+    // claim a key that does nothing (REQ-UI-CONTROLS-ACCURACY). The chips of the row
+    // that leaves the mode are the ones marked, not its label (REQ-UI-CONTROLS-CARD).
+    const bool exitsMode = (action == ControlAction::ExitMode);
+    const std::vector<ControlBinding> bindings = getControlActionBindings(action, context);
+    for (const ControlBinding& binding : bindings)
+    {
+        QLabel* badge = new QLabel(getControlBindingBadge(binding), row);
+        badge->setObjectName(exitsMode ? QStringLiteral("controlBadgeExit")
+                                       : QStringLiteral("controlBadge"));
+        layout->addWidget(badge);
+    }
+
+    QLabel* label = new QLabel(getControlActionLabel(action, context), row);
+    label->setObjectName(QStringLiteral("controlLabel"));
+    layout->addSpacing(4);
+    layout->addWidget(label);
+    layout->addStretch(1);
+    return row;
+}
+
+// Adds a freshly built widget to the rows and shows it.
+//
+// The show is what makes it count. A widget created under an already-visible parent
+// starts hidden, and a layout treats a hidden item as empty -- it contributes nothing
+// to the size hint until something shows it, which otherwise does not happen until the
+// event loop next runs, long after the panel has measured itself.
+void addAndShow(QVBoxLayout* layout, QWidget* widget)
+{
+    layout->addWidget(widget);
+    widget->show();
+}
+
+}  // namespace
+
+ControlsPanel::ControlsPanel(const GameWorldView* view, QWidget* parent)
+    : QWidget(parent)
+    , m_view(view)
+{
+    // Floats over the rendered world, so it brings its own background to stay legible
+    // over any world content (REQ-UI-CONTROLS-PANEL). Palette colors match the build
+    // button bar's and the selection panel's chrome; like them this is widget chrome
+    // rather than world rendering, so it is deliberately not a visuals.toml color. The
+    // class scoped selector keeps the border on the panel rather than cascading onto
+    // its children.
+    setAttribute(Qt::WA_StyledBackground, true);
+    // Letter spacing is deliberately absent here: Qt's stylesheet syntax has no such
+    // property and warns on every widget it is applied to. The heading and the caption
+    // set it on their QFont instead.
+    setStyleSheet(QStringLiteral(
+        "ControlsPanel { background-color: palette(window);"
+        " border: 1px solid palette(mid); border-radius: 4px; }"
+        "QLabel#controlHeading { color: palette(text); }"
+        "QLabel#controlBadge { border: 1px solid palette(mid); border-radius: 3px;"
+        " padding: 1px 5px; font-family: monospace; color: palette(text); }"
+        "QLabel#controlLabel { color: palette(text); }"
+        // The row that leaves the mode is marked on its chips rather than its label
+        // (REQ-UI-CONTROLS-CARD): the label keeps the ordinary text color, so the row
+        // stays legible whatever the palette, and only the chips carry the warning.
+        //
+        // A literal red because there is no palette role for "destructive" -- the
+        // nearest, bright-text, is white by design, being meant for text over dark
+        // highlights, and was unreadable on this panel's chrome. This value reads on a
+        // light and a dark background alike. It is widget chrome, so like the rest of
+        // this stylesheet it is deliberately not a visuals.toml color.
+        "QLabel#controlBadgeExit { border: 1px solid #c0392b; border-radius: 3px;"
+        " padding: 1px 5px; font-family: monospace; color: #c0392b; }"
+        "QLabel#controlCaption { color: palette(mid); }"));
+
+    QVBoxLayout* outerLayout = new QVBoxLayout(this);
+    outerLayout->setContentsMargins(kCardMarginPx, kCardMarginPx,
+                                    kCardMarginPx, kCardMarginPx);
+    outerLayout->setSpacing(kHeadingGapPx);
+
+    m_heading = new QLabel(this);
+    m_heading->setObjectName(QStringLiteral("controlHeading"));
+    m_heading->setCursor(Qt::PointingHandCursor);
+    m_heading->setFont(makeSpacedFont(font(), /*bold*/ true, /*pointSizeDelta*/ 0));
+    outerLayout->addWidget(m_heading);
+
+    // Rows taller than the space available scroll rather than being cut off
+    // (REQ-UI-CONTROLS-PANEL). The viewport is transparent so the panel's own rounded
+    // chrome shows through, and horizontal scrolling is off because the width always
+    // follows the content.
+    m_rows       = new QWidget(this);
+    m_rowsLayout = new QVBoxLayout(m_rows);
+    m_rowsLayout->setContentsMargins(0, 0, 0, 0);
+    m_rowsLayout->setSpacing(0);
+    m_rows->setAutoFillBackground(false);
+
+    m_scrollArea = new QScrollArea(this);
+    m_scrollArea->setFrameShape(QFrame::NoFrame);
+    m_scrollArea->setWidgetResizable(true);
+    m_scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    m_scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
+    m_scrollArea->viewport()->setAutoFillBackground(false);
+    m_scrollArea->setWidget(m_rows);
+    outerLayout->addWidget(m_scrollArea);
+
+    // Polling rather than subscribing; see the class comment.
+    m_refreshTimer = new QTimer(this);
+    connect(m_refreshTimer, &QTimer::timeout, this, &ControlsPanel::refresh);
+    m_refreshTimer->start(kRefreshMs);
+
+    refresh();
+}
+
+void ControlsPanel::invalidateLayout()
+{
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<FloatingLayoutInvalidatedEvent>());
+}
+
+void ControlsPanel::mousePressEvent(QMouseEvent* event)
+{
+    // Only the heading toggles; a click anywhere else is swallowed so it never reaches
+    // the world beneath (REQ-UI-CONTROLS-PANEL).
+    if (m_heading->geometry().contains(event->pos()))
+    {
+        m_collapsed = !m_collapsed;
+        m_scrollArea->setVisible(!m_collapsed);
+        invalidateLayout();
+    }
+    event->accept();
+}
+
+void ControlsPanel::refresh()
+{
+    if (!m_view) { return; }
+
+    const ControlContext context = m_view->getControlContext();
+
+    const QString                    heading = getHeadingText(context);
+    const std::vector<ControlAction> contextActions = getContextActions(context);
+    const std::vector<ControlAction> alwaysActions  = getAlwaysAvailableActions(context);
+
+    if (heading == m_shownHeading && contextActions == m_shownContextActions
+        && alwaysActions == m_shownAlwaysActions)
+    {
+        return;
+    }
+
+    m_shownHeading        = heading;
+    m_shownContextActions = contextActions;
+    m_shownAlwaysActions  = alwaysActions;
+    rebuild(context);
+}
+
+void ControlsPanel::rebuild(const ControlContext& context)
+{
+    m_heading->setText(m_shownHeading);
+
+    // Rows are rebuilt wholesale rather than reconciled: a context change replaces
+    // nearly all of them, and the panel redraws only when something actually changed.
+    while (QLayoutItem* item = m_rowsLayout->takeAt(0))
+    {
+        delete item->widget();
+        delete item;
+    }
+
+    for (ControlAction action : m_shownContextActions)
+    {
+        addAndShow(m_rowsLayout, makeRow(action, context, m_rows));
+    }
+
+    // The always-available block sits under a divider in every context, the General one
+    // included, so the card is read the same way wherever the player is
+    // (REQ-UI-CONTROLS-CARD).
+    if (!m_shownAlwaysActions.empty())
+    {
+        QFrame* divider = new QFrame(m_rows);
+        divider->setFrameShape(QFrame::HLine);
+        divider->setFrameShadow(QFrame::Plain);
+        m_rowsLayout->addSpacing(6);
+        addAndShow(m_rowsLayout, divider);
+
+        QLabel* caption = new QLabel(tr("ALWAYS AVAILABLE"), m_rows);
+        caption->setObjectName(QStringLiteral("controlCaption"));
+        caption->setFont(makeSpacedFont(font(), /*bold*/ false, /*pointSizeDelta*/ -1));
+        addAndShow(m_rowsLayout, caption);
+    }
+
+    for (ControlAction action : m_shownAlwaysActions)
+    {
+        addAndShow(m_rowsLayout, makeRow(action, context, m_rows));
+    }
+
+    m_scrollArea->setVisible(!m_collapsed);
+    invalidateLayout();
+}
+
+QString ControlsPanel::getHeadingText(const ControlContext& context) const
+{
+    const ControlContextKind kind = getControlContextKind(context);
+    const QString            name = getControlContextName(kind);
+
+    QString detail;
+    switch (kind)
+    {
+    case ControlContextKind::Build:
+        detail = getBuildingTypeName(context.builderType);
+        break;
+    case ControlContextKind::Blueprint:
+    {
+        // The temporary blueprint is never named (REQ-UI-BLUEPRINT-TEMP), so it is
+        // labelled by what it is rather than left blank.
+        const QString blueprintName = m_view->getActiveBlueprintName();
+        detail = blueprintName.isEmpty() ? tr("Temporary") : blueprintName;
+        break;
+    }
+    case ControlContextKind::Selection:
+        detail = context.selection == ControlSelection::Buildings
+                     ? tr("%n building(s)", "", context.selectionCount)
+                     : tr("%n object(s)", "", context.selectionCount);
+        break;
+    case ControlContextKind::General:
+    case ControlContextKind::Deconstruct:
+        break;
+    }
+
+    if (detail.isEmpty()) { return name; }
+    return name + QStringLiteral(" ") + kHeadingSeparator + QStringLiteral(" ") + detail;
+}
+
+void ControlsPanel::placeIn(const QRect& viewRect, const std::vector<QRect>& occupiedRects)
+{
+    if (viewRect.isNull()) { return; }
+
+    // Rows are torn down and rebuilt wholesale, and a widget added to a layout is only
+    // shown once that layout runs -- without this the new rows count for nothing and
+    // the card is measured for the context before it. The polish belongs to the same
+    // step: a freshly created label reports an unstyled size hint until the stylesheet
+    // has reached it, and the badge chips carry border and padding that change it.
+    m_rows->ensurePolished();
+    m_rowsLayout->invalidate();
+    m_rowsLayout->activate();
+
+    const QRect band = viewRect.adjusted(kMarginPx, kMarginPx, -kMarginPx, -kMarginPx);
+    if (band.width() <= 0 || band.height() <= 0) { return; }
+
+    // Measured from the heading and the rows directly rather than from the panel's own
+    // layout: the rows now sit in a scroll area, whose size hint describes a viewport
+    // and says nothing about how tall its contents are. Deliberately not activating the
+    // panel's own layout either -- that lays its children out inside the geometry left
+    // over from the previous context, which is the wrong frame of reference for
+    // choosing the new one. setGeometry below re-runs it.
+    const int   chromePx    = 2 * (kCardMarginPx + kBorderPx);
+    const QSize headingHint = m_heading->sizeHint();
+    const QSize rowsHint    = m_rows->sizeHint();
+
+    int contentWidthPx  = headingHint.width();
+    int contentHeightPx = headingHint.height();
+    if (!m_collapsed)
+    {
+        contentWidthPx  = qMax(contentWidthPx, rowsHint.width());
+        contentHeightPx += kHeadingGapPx + rowsHint.height();
+    }
+    const int wantedHeightPx = contentHeightPx + chromePx;
+
+    // The bottom-left corner of the view, growing upward as rows are added
+    // (REQ-UI-CONTROLS-PANEL).
+    int widthPx = qMin(contentWidthPx + chromePx, band.width());
+
+    // The build button bar is centered and sized to its buttons, so it usually leaves
+    // this corner free and the panel can share the bottom edge with it. Only where the
+    // two would actually meet does the panel rise, clearing the bar's top by the same
+    // margin it keeps from the view's edges (REQ-UI-BUILD-BAR). The bar is the only
+    // widget placed before this one, so it is the only rect that can be in the way.
+    const int bottomPx = getAvailableBottomPx(band, occupiedRects, band.left(),
+                                              band.left() + widthPx - 1, kMarginPx);
+    int heightPx = qMin(wantedHeightPx, qMax(0, bottomPx - band.top() + 1));
+    int topPx    = bottomPx - heightPx + 1;
+
+    // Whatever the rows lost to either cap, they scroll for. The scrollbar needs its
+    // own width, or it would appear over the labels.
+    if (heightPx < wantedHeightPx)
+    {
+        widthPx = qMin(widthPx + m_scrollArea->verticalScrollBar()->sizeHint().width(),
+                       band.width());
+    }
+
+    setGeometry(band.left(), topPx, widthPx, heightPx);
+}

src/ui/ControlsPanel.h

@@ -0,0 +1,87 @@
+#pragma once
+
+#include <vector>
+
+#include <QRect>
+#include <QString>
+#include <QWidget>
+
+#include "ControlAction.h"
+#include "FloatingPanel.h"
+
+class GameWorldView;
+class QLabel;
+class QScrollArea;
+class QTimer;
+class QVBoxLayout;
+
+// Shows the controls available in the player's current situation
+// (REQ-UI-CONTROLS-PANEL). The panel decides nothing: which rows apply is
+// ControlAction.h's answer, the same one the key handling and the world view's mouse
+// dispatch act on, so what is shown and what happens cannot part company
+// (REQ-UI-CONTROLS-ACCURACY).
+//
+// It floats over the game world at the left edge, bottom-aligned within the band its
+// owner hands it, and collapses to its heading when the heading is clicked.
+//
+// Refreshed on a timer rather than by subscribing to events: two of the things that
+// change a row -- a belt drag starting, the ghost moving over a transfer target --
+// happen on mouse movement and publish nothing, and they still have to be reflected
+// while the game is paused, so there is no tick to hang it on either. The rebuild is
+// skipped unless the resolved content actually differs, which is a vector of enums to
+// compare.
+class ControlsPanel : public QWidget, public FloatingPanel
+{
+    Q_OBJECT
+
+public:
+    // Neither pointer is owned; both must outlive this widget. The view is the source
+    // of the control context, being the widget that owns the build mode and the
+    // selection.
+    ControlsPanel(const GameWorldView* view, QWidget* parent = nullptr);
+
+    // Places the panel in the bottom-left corner of the game world view. It shares the
+    // bottom edge with the build button bar rather than clearing its strip, the bar
+    // being centered and sized to its buttons and so usually leaving the left free; it
+    // rises above the bar only when the two would otherwise overlap
+    // (REQ-UI-CONTROLS-PANEL, REQ-UI-BUILD-BAR). The bar is the only thing placed before
+    // it, so it is the only rect it ever has to rise above.
+    void placeIn(const QRect& viewRect,
+                 const std::vector<QRect>& occupiedRects) override;
+
+protected:
+    // Clicking the heading collapses and expands the panel (REQ-UI-CONTROLS-PANEL).
+    void mousePressEvent(QMouseEvent* event) override;
+
+private:
+    // Re-resolves the context and rebuilds only if the rows or the heading changed.
+    void refresh();
+    // Replaces the rows with those of the current context.
+    void rebuild(const ControlContext& context);
+    // The heading's "<name> * <detail>" text for the context, detail omitted when the
+    // context has none.
+    QString getHeadingText(const ControlContext& context) const;
+    // Asks for the placement pass to be re-run, the panel's own size having changed.
+    void invalidateLayout();
+
+    const GameWorldView* m_view;
+
+    QLabel*      m_heading;
+    // Scrolls the rows once they outgrow the space the panel has (REQ-UI-CONTROLS-PANEL).
+    // The heading is deliberately outside it, so it stays put and stays clickable.
+    QScrollArea* m_scrollArea;
+    QWidget*     m_rows;
+    QVBoxLayout* m_rowsLayout;
+    QTimer*      m_refreshTimer;
+
+    // What is currently drawn, so a refresh that resolves to the same thing does
+    // nothing. The always-available block is kept separately because the divider
+    // between the two is part of what is drawn.
+    QString                    m_shownHeading;
+    std::vector<ControlAction> m_shownContextActions;
+    std::vector<ControlAction> m_shownAlwaysActions;
+
+    // Survives context changes and simulation restarts; presentation only, never a
+    // command (REQ-UI-CONTROLS-PANEL).
+    bool m_collapsed = false;
+};

src/ui/FloatingPanel.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <vector>
+
+#include <QRect>
+
+// A widget floating over the game world view (REQ-UI-WORLD-SIZE). MainWindow places all
+// of them in one ordered pass -- build button bar, then controls panel, then selection
+// panel -- and each places itself into the space the earlier ones have not taken. The
+// order is the priority the requirements state: the bar never moves for anyone
+// (REQ-UI-BUILD-BAR), the controls panel steps around the bar (REQ-UI-CONTROLS-PANEL),
+// and keeping clear of both is the selection panel's job (REQ-UI-SELECTION-PANEL).
+//
+// A widget never re-places itself, because what it may take depends on the widgets placed
+// before it. It instead publishes FloatingLayoutInvalidatedEvent whenever its content or
+// its visibility changed, and the owner re-runs the whole pass.
+class FloatingPanel
+{
+public:
+    virtual ~FloatingPanel() = default;
+
+    // Sets this widget's own geometry within viewRect, keeping clear of occupiedRects --
+    // the geometry of every floating widget already placed in this pass, in the same
+    // coordinates. A widget with nothing to show hides itself and takes no space.
+    virtual void placeIn(const QRect& viewRect,
+                         const std::vector<QRect>& occupiedRects) = 0;
+};

src/ui/GameWorldView.cpp

@@ -1,6 +1,7 @@
 #include "GameWorldView.h"
 #include "PlacementRules.h"
 #include "FactoryQueries.h"
+#include "BlueprintLibrary.h"
 
 #include <algorithm>
 #include <cctype>
@@ -46,6 +47,8 @@
 #include "ItemIconCache.h"
 #include "PositionComponent.h"
 #include "DebrisSystem.h"
+#include "SelectionAnchorChangedEvent.h"
+#include "SelectionBounds.h"
 #include "SelectionChangedEvent.h"
 #include "ShipIdentityComponent.h"
 #include "ShipSystem.h"
@@ -73,6 +76,23 @@
 namespace
 {
 
+// The action a left-button gesture triggers, with the Ctrl variant falling back to the
+// plain one wherever nothing is bound to it. That fallback is what keeps Ctrl+click
+// placing a building in builder mode and Ctrl+drag deconstructing an area: the modifier
+// only means something where an action claims it (REQ-UI-CONTROLS-CONTENT).
+ControlAction resolveLeftGesture(bool controlHeld, bool isDrag,
+                                 const ControlContext& context)
+{
+    if (controlHeld)
+    {
+        const ControlAction action = resolveMouseAction(
+            isDrag ? MouseBinding::CtrlLeftDrag : MouseBinding::CtrlLeftClick, context);
+        if (action != ControlAction::None) { return action; }
+    }
+    return resolveMouseAction(isDrag ? MouseBinding::LeftDrag : MouseBinding::LeftClick,
+                              context);
+}
+
 // Keep only the filter entries whose item type is currently unlocked
 // (REQ-LOCK-UI-BLUEPRINT). An empty result means "accept all".
 std::vector<ItemType> filterUnlockedItems(const std::vector<ItemType>& filter,
@@ -1075,7 +1095,7 @@ void GameWorldView::keyPressEvent(QKeyEvent* event)
     // Keys are turned into actions and published by the input mapper
     // (REQ-UI-HOTKEYS); this widget reacts to those as an ordinary subscriber, so
     // nothing is handled here directly.
-    if (m_inputMapper.handleKeyPress(event)) { return; }
+    if (m_inputMapper.handleKeyPress(event, getControlContext())) { return; }
 
     QOpenGLWidget::keyPressEvent(event);
 }
@@ -1087,7 +1107,7 @@ void GameWorldView::keyReleaseEvent(QKeyEvent* event)
         QOpenGLWidget::keyReleaseEvent(event);
         return;
     }
-    if (m_inputMapper.handleKeyRelease(event)) { return; }
+    if (m_inputMapper.handleKeyRelease(event, getControlContext())) { return; }
     QOpenGLWidget::keyReleaseEvent(event);
 }
 
@@ -1101,36 +1121,93 @@ void GameWorldView::focusOutEvent(QFocusEvent* event)
     QOpenGLWidget::focusOutEvent(event);
 }
 
+void GameWorldView::setBlueprintLibrary(const BlueprintLibrary* library)
+{
+    m_blueprintLibrary = library;
+}
+
+ControlContext GameWorldView::getControlContext() const
+{
+    ControlContext context;
+    context.mode                   = m_buildMode.getMode();
+    context.draggingBelt           = m_buildMode.isDraggingBelt();
+    context.hoveredGhostIsTransfer = m_buildMode.isHoveredGhostTransfer();
+    if (m_buildMode.isBuilderMode()) { context.builderType = m_buildMode.getBuilderType(); }
+
+    // Buildings win over field objects, so the two are never both non-empty
+    // (REQ-UI-SELECTION-CATEGORIES).
+    const std::vector<BuildingId>&   buildings = m_selection.getSelectedBuildings();
+    const std::vector<entt::entity>& actors    = m_selection.getSelectedActors();
+    const std::vector<entt::entity>& debris    = m_selection.getSelectedDebris();
+    if (!buildings.empty())
+    {
+        context.selection      = ControlSelection::Buildings;
+        context.selectionCount = static_cast<int>(buildings.size());
+    }
+    else if (!actors.empty() || !debris.empty())
+    {
+        context.selection      = ControlSelection::FieldObjects;
+        context.selectionCount = static_cast<int>(actors.size() + debris.size());
+    }
+
+    if (m_blueprintLibrary)
+    {
+        context.placeableBuildingSelected = m_blueprintLibrary->getCanCaptureSelection();
+        context.temporaryBlueprintExists  = m_blueprintLibrary->getHasTemporaryBlueprint();
+    }
+    return context;
+}
+
+QString GameWorldView::getActiveBlueprintName() const
+{
+    if (!m_buildMode.isBlueprintMode()) { return QString(); }
+    return m_buildMode.getBlueprint().name;
+}
+
 void GameWorldView::mousePressEvent(QMouseEvent* event)
 {
     const WorldCoordinates coordinates = getCoordinates();
+    const ControlContext   context     = getControlContext();
 
     if (event->button() != Qt::LeftButton)
     {
         if (event->button() == Qt::RightButton)
         {
-            if (m_buildMode.isBuilderMode() && m_buildMode.isDraggingBelt())
+            switch (resolveMouseAction(MouseBinding::RightClick, context))
             {
-                // Cancel the in-progress belt drag without placing anything;
-                // stay in belt builder mode (REQ-BLD-BELT-DRAG).
+            case ControlAction::CancelBeltLine:
+                // Drop the in-progress path without placing anything; belt builder
+                // mode stays active (REQ-BLD-BELT-DRAG).
                 m_buildMode.cancelBeltDrag();
-            }
-            else if (m_buildMode.getMode() != BuildMode::None)
-            {
+                break;
+            case ControlAction::ExitMode:
                 m_buildMode.exitCurrentMode();
+                break;
+            default:
+                break;
             }
         }
         return;
     }
 
     const QPoint tile = coordinates.widgetToTile(event->pos());
+    const bool   controlHeld = (event->modifiers() & Qt::ControlModifier) != 0;
 
-    if (m_buildMode.isBuilderMode())
+    // A press begins the click gesture; whether it turns out to be a drag is settled on
+    // release, where the drag binding is resolved instead.
+    switch (resolveLeftGesture(controlHeld, /*isDrag*/ false, context))
     {
-        if (m_buildMode.getBuilderType() == BuildingType::Belt)
+    case ControlAction::Place:
+    case ControlAction::ApplySettings:
+        if (m_buildMode.isBlueprintMode())
         {
-            // Deferred placement: start the drag and show the path ghost; nothing
-            // is placed until release (REQ-BLD-BELT-DRAG).
+            placeBlueprintAtTile(tile);
+        }
+        else if (m_buildMode.getBuilderType() == BuildingType::Belt)
+        {
+            // Belts place by dragging, so the press only anchors the path and shows its
+            // ghost; nothing is placed until release, and a plain click is the one-tile
+            // case (REQ-BLD-BELT-DRAG).
             m_buildMode.beginBeltDrag(tile);
             m_cursorWorldPos = coordinates.widgetToWorld(event->pos());
             recomputeBeltDragPath(tile);
@@ -1139,27 +1216,22 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
         {
             placeAtTile(tile);
         }
-    }
-    else if (m_buildMode.isBlueprintMode())
-    {
-        placeBlueprintAtTile(tile);
-    }
-    else if (m_buildMode.isDeconstructMode())
-    {
+        break;
+
+    case ControlAction::ToggleDeconstruct:
         // Start a deconstruct box drag; a plain click resolves as a 1x1 box on
         // release (REQ-BLD-DECONSTRUCT-CLICK, REQ-BLD-DECONSTRUCT-BOX).
         m_boxSelecting   = true;
         m_boxStartTile   = tile;
         m_boxCurrentTile = tile;
-    }
-    else
-    {
-        const bool ctrl = (event->modifiers() & Qt::ControlModifier) != 0;
+        break;
 
+    case ControlAction::Select:
+    case ControlAction::AddToSelection:
         // Only a click that hit nothing starts a box drag. Starting one on a hit
         // would re-resolve the same object as a 1x1 box on release and undo the
         // click: a Ctrl+click would toggle the building off, then straight back on.
-        if (!selectAtPoint(tile, coordinates.widgetToWorld(event->pos()), ctrl))
+        if (!selectAtPoint(tile, coordinates.widgetToWorld(event->pos()), controlHeld))
         {
             // selectAtPoint has already cleared the selection unless Ctrl is
             // preserving it for an additive drag.
@@ -1167,6 +1239,10 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
             m_boxStartTile    = tile;
             m_boxCurrentTile  = tile;
         }
+        break;
+
+    default:
+        break;
     }
 }
 
@@ -1181,6 +1257,7 @@ bool GameWorldView::selectAtPoint(QPoint tile, QVector2D worldPos, bool additive
     if (!buildingHit.has_value()) { buildingHit = siteAtTile(tile); }
     if (buildingHit.has_value())
     {
+        publishSelectionAnchor(mode, {*buildingHit}, {}, {});
         m_selection.selectBuildings({*buildingHit}, mode);
         return true;
     }
@@ -1188,6 +1265,7 @@ bool GameWorldView::selectAtPoint(QPoint tile, QVector2D worldPos, bool additive
     const entt::entity actorHit = entityAtWorldPos(m_sim->getAdmin(), worldPos);
     if (actorHit != entt::null)
     {
+        publishSelectionAnchor(mode, {}, {actorHit}, {});
         m_selection.selectFieldObjects({actorHit}, {}, mode);
         return true;
     }
@@ -1195,6 +1273,7 @@ bool GameWorldView::selectAtPoint(QPoint tile, QVector2D worldPos, bool additive
     const entt::entity debrisHit = debrisAtWorldPos(m_sim->getAdmin(), worldPos);
     if (debrisHit != entt::null)
     {
+        publishSelectionAnchor(mode, {}, {}, {debrisHit});
         m_selection.selectFieldObjects({}, {debrisHit}, mode);
         return true;
     }
@@ -1215,6 +1294,7 @@ void GameWorldView::selectInBox(bool additive)
         buildingsInBox(m_sim->getFactoryState(), m_boxStartTile, m_boxCurrentTile);
     if (!boxIds.empty())
     {
+        publishSelectionAnchor(mode, boxIds, {}, {});
         m_selection.selectBuildings(boxIds, mode);
         return;
     }
@@ -1225,6 +1305,7 @@ void GameWorldView::selectInBox(bool additive)
         debrisInBox(m_sim->getAdmin(), m_boxStartTile, m_boxCurrentTile);
     if (!boxActors.empty() || !boxDebris.empty())
     {
+        publishSelectionAnchor(mode, {}, boxActors, boxDebris);
         m_selection.selectFieldObjects(boxActors, boxDebris, mode);
         return;
     }
@@ -1233,6 +1314,35 @@ void GameWorldView::selectInBox(bool additive)
     if (!additive) { m_selection.clearAll(); }
 }
 
+void GameWorldView::publishSelectionAnchor(SelectionMode mode,
+                                           const std::vector<BuildingId>& buildings,
+                                           const std::vector<entt::entity>& actors,
+                                           const std::vector<entt::entity>& debris)
+{
+    // An additive gesture onto something already selected is growing that selection, not
+    // starting one, and the panel stays where it was put (REQ-UI-SELECTION-PANEL).
+    const bool startsSelection =
+        (mode == SelectionMode::Replace) || (m_selection.getSelectedBuildings().empty()
+                                             && m_selection.getSelectedActors().empty()
+                                             && m_selection.getSelectedDebris().empty());
+    if (!startsSelection)
+    {
+        return;
+    }
+
+    // Screen space, frozen here: the panel is placed against where the selection is at
+    // this moment and stays there, however far the view scrolls or the objects move
+    // afterwards.
+    const QRect anchorRect = getSelectionWidgetRect(*m_sim, getCoordinates(),
+                                                    buildings, actors, debris);
+    if (anchorRect.isNull())
+    {
+        return;
+    }
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<SelectionAnchorChangedEvent>(anchorRect));
+}
+
 void GameWorldView::mouseMoveEvent(QMouseEvent* event)
 {
     const WorldCoordinates coordinates = getCoordinates();
@@ -1263,6 +1373,21 @@ void GameWorldView::mouseMoveEvent(QMouseEvent* event)
     else if (m_buildMode.isBlueprintMode())
     {
         m_buildMode.setBlueprintGhostTile(tile);
+
+        // Resolved here, once, through the same classifier the click and the ghost's
+        // colour use, and stored on the mode: the controls panel says "Apply settings"
+        // exactly when clicking would transfer (REQ-UI-BLUEPRINT-TRANSFER). Only a
+        // single-building blueprint hit-tests the cursor, so only it can be a hovered
+        // transfer target.
+        const std::vector<BlueprintBuilding>& buildings =
+            m_buildMode.getBlueprint().buildings;
+        bool transfer = false;
+        if (buildings.size() == 1)
+        {
+            transfer = resolveBlueprintGhostHere(buildings.front(), tile).action
+                       == BlueprintGhostAction::Transfer;
+        }
+        m_buildMode.setHoveredGhostTransfer(transfer);
     }
     else if (m_buildMode.isDeconstructMode())
     {
@@ -1294,7 +1419,11 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
         const std::vector<BuildingId> boxIds =
             buildingsInBox(m_sim->getFactoryState(), m_boxStartTile, m_boxCurrentTile);
 
-        if (m_buildMode.isDeconstructMode())
+        const bool controlHeld = (event->modifiers() & Qt::ControlModifier) != 0;
+        const ControlAction dragAction =
+            resolveLeftGesture(controlHeld, /*isDrag*/ true, getControlContext());
+
+        if (dragAction == ControlAction::DeconstructArea)
         {
             const FactoryState& factory = m_sim->getFactoryState();
 
@@ -1356,7 +1485,9 @@ void GameWorldView::mouseReleaseEvent(QMouseEvent* event)
             return;
         }
 
-        selectInBox((event->modifiers() & Qt::ControlModifier) != 0);
+        // A Ctrl box adds and never deselects, where a plain one replaces
+        // (REQ-UI-MULTI-SELECT).
+        selectInBox(dragAction == ControlAction::AddAreaToSelection);
     }
 }
 

src/ui/GameWorldView.h

@@ -64,6 +64,7 @@
 
 struct Command;
 struct ParsedReplay;
+class BlueprintLibrary;
 class ItemIconCache;
 class ReplayPlayer;
 class Simulation;
@@ -102,6 +103,21 @@ public:
     void setGameSpeed(double multiplier);
     void resetForNewGame();
 
+    // The blueprint library is constructed after this widget, so it arrives by setter.
+    // Not owned; supplies the two facts about blueprints that the control context needs
+    // (REQ-UI-CONTROLS-CONTENT).
+    void setBlueprintLibrary(const BlueprintLibrary* library);
+
+    // The player's current situation, as the one snapshot every reader of the control
+    // table works from: this widget's own mouse dispatch, the input mapper, and the
+    // controls panel (REQ-UI-CONTROLS-CONTENT). Built here because this widget owns the
+    // build mode and the selection.
+    ControlContext getControlContext() const;
+
+    // Name of the blueprint being placed, for the controls panel's heading. Empty while
+    // no blueprint is active and for the unnamed temporary one (REQ-UI-BLUEPRINT-TEMP).
+    QString getActiveBlueprintName() const;
+
 protected:
     void initializeGL() override;
     void paintGL() override;
@@ -210,6 +226,15 @@ private:
     // which is the only case that goes on to start a box drag.
     bool                     selectAtPoint(QPoint tile, QVector2D worldPos, bool additive);
     void                     selectInBox(bool additive);
+    // Publishes where on the screen the selection about to be made sits, so the
+    // selection panel can be placed beside it (REQ-UI-SELECTION-PANEL). Called with
+    // what is about to be selected, immediately before selecting it, and publishes
+    // nothing unless that selection is starting rather than growing.
+    void                     publishSelectionAnchor(
+                                 SelectionMode mode,
+                                 const std::vector<BuildingId>& buildings,
+                                 const std::vector<entt::entity>& actors,
+                                 const std::vector<entt::entity>& debris);
     void                     stepSpeed(int delta);
     void                     placeAtTile(QPoint tile);
 
@@ -280,6 +305,8 @@ private:
     // between them (REQ-UI-SELECTION-CATEGORIES), including publishing the change
     // events. This widget only resolves what was hit.
     SelectionController   m_selection;
+    // Not owned; set after construction, so null until MainWindow has built it.
+    const BlueprintLibrary* m_blueprintLibrary = nullptr;
     bool                  m_boxSelecting;
     QPoint                m_boxStartTile;
     QPoint                m_boxCurrentTile;

src/ui/InputMapper.cpp

@@ -9,6 +9,7 @@
 #include "BlueprintSelectionRequestedEvent.h"
 #include "BuildHotkeyPressedEvent.h"
 #include "BuildingType.h"
+#include "ControlAction.h"
 #include "DebugDrawToggleRequestedEvent.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventManager.h"
@@ -77,7 +78,7 @@ QString InputMapper::getBuildHotkeyLabel(BuildingType type)
     return QString();
 }
 
-bool InputMapper::handleKeyPress(QKeyEvent* event)
+bool InputMapper::handleKeyPress(QKeyEvent* event, const ControlContext& context)
 {
     // Auto-repeat says nothing new about which keys are down, and a held action is
     // already held.
@@ -86,6 +87,9 @@ bool InputMapper::handleKeyPress(QKeyEvent* event)
     // Number-key build-mode hotkeys (REQ-UI-HOTKEYS). nativeVirtualKey gives the
     // physical digit independent of keyboard layout and Shift (with Shift held, key()
     // for the number row can arrive as Key_Exclam etc.). VK_1..VK_9 = 0x31..0x39.
+    // Not part of the ControlAction table: these are advertised on the build buttons
+    // rather than in the controls panel, and getBuildHotkeyLabel already reads the
+    // same binding table this does (REQ-UI-CONTROLS-ACCURACY).
     const quint32 virtualKey = event->nativeVirtualKey();
     if (virtualKey >= 0x31 && virtualKey <= 0x39)
     {
@@ -100,107 +104,102 @@ bool InputMapper::handleKeyPress(QKeyEvent* event)
         }
     }
 
-    // Blueprint chords (REQ-UI-HOTKEYS). Checked ahead of the plain-key switch below,
-    // which binds bare A/D/W/S/R/Q/C/V and must not fire on a Ctrl chord -- bare C and V
-    // are the temporary-blueprint counterparts of these two (REQ-UI-BLUEPRINT-TEMP). Both
-    // requests are decided by MainWindow, the only widget that can pause the game and dim
-    // the window for a modal.
-    if ((event->modifiers() & Qt::ControlModifier) != 0)
-    {
+    // Development controls, deliberately outside the table so they are never offered
+    // to the player (REQ-UI-CONTROLS-ACCURACY).
     switch (event->key())
     {
-        case Qt::Key_C:
-            EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<BlueprintSaveRequestedEvent>());
-            return true;
-        case Qt::Key_V:
-            EventManager::getInstance()->sendEventImmediately(
-                std::make_shared<BlueprintSelectionRequestedEvent>());
-            return true;
-        default:
-            break;
-        }
-    }
-
-    switch (event->key())
-    {
-    case Qt::Key_A:
-        m_panLeftHeld = true;
-        updatePanDirection();
-        return true;
-    case Qt::Key_D:
-        m_panRightHeld = true;
-        updatePanDirection();
-        return true;
-    case Qt::Key_Space:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<PauseToggleRequestedEvent>());
-        return true;
-    case Qt::Key_W:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<SpeedStepRequestedEvent>(+1));
-        return true;
-    case Qt::Key_S:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<SpeedStepRequestedEvent>(-1));
-        return true;
-    case Qt::Key_R:
-        // Shift reverses the rotation direction (REQ-BLD-ROTATE).
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<GhostRotationRequestedEvent>(
-                (event->modifiers() & Qt::ShiftModifier) != 0));
-        return true;
-    case Qt::Key_Q:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<ModeCancelRequestedEvent>());
-        return true;
-    case Qt::Key_C:
-        // Capture a temporary blueprint from the current selection (REQ-UI-BLUEPRINT-TEMP).
-        // The BlueprintLibrary owns the selection and blueprint-capture logic; it decides
-        // whether anything placeable is selected and drives placement mode from there.
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<TemporaryBlueprintCaptureRequestedEvent>());
-        return true;
-    case Qt::Key_V:
-        // Re-enter placement mode for the temporary blueprint captured with C, if there is
-        // one (REQ-UI-BLUEPRINT-TEMP). The library holds it; nothing is captured here.
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<TemporaryBlueprintPlaceRequestedEvent>());
-        return true;
     case Qt::Key_F3:
         EventManager::getInstance()->sendEventImmediately(
             std::make_shared<DebugDrawToggleRequestedEvent>());
         return true;
-    case Qt::Key_Escape:
-        EventManager::getInstance()->sendEventImmediately(
-            std::make_shared<EscapeMenuRequestedEvent>());
-        return true;
     case Qt::Key_F4:
         EventManager::getInstance()->addEvent(
             std::make_shared<TracePrintRequestedEvent>());
         return true;
     default:
+        break;
+    }
+
+    // Everything else: the key names an action, the action names an event. Which key
+    // is bound to what, and whether it does anything in this situation, are both the
+    // table's business -- this switch only knows what each action means
+    // (REQ-UI-HOTKEYS, REQ-UI-CONTROLS-ACCURACY).
+    switch (resolveKeyAction(event->key(), event->modifiers(), context))
+    {
+    case ControlAction::Move:
+        // A parameter of the action rather than an action of its own: the table binds
+        // both keys to Move and the direction is read off the key here, as the rotation
+        // direction and the build hotkey's digit are.
+        if (event->key() == Qt::Key_A) { m_panLeftHeld = true; }
+        else                           { m_panRightHeld = true; }
+        updatePanDirection();
+        return true;
+    case ControlAction::GameSpeed:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<SpeedStepRequestedEvent>(event->key() == Qt::Key_W ? +1 : -1));
+        return true;
+    case ControlAction::TogglePause:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<PauseToggleRequestedEvent>());
+        return true;
+    case ControlAction::Rotate:
+        // Shift reverses the rotation direction (REQ-BLD-ROTATE).
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<GhostRotationRequestedEvent>(
+                (event->modifiers() & Qt::ShiftModifier) != 0));
+        return true;
+    case ControlAction::EnterDeconstruct:
+    case ControlAction::ExitMode:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<ModeCancelRequestedEvent>());
+        return true;
+    case ControlAction::CopyTemporary:
+        // The BlueprintLibrary owns the selection and blueprint-capture logic; it drives
+        // placement mode from there (REQ-UI-BLUEPRINT-TEMP).
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<TemporaryBlueprintCaptureRequestedEvent>());
+        return true;
+    case ControlAction::PasteTemporary:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<TemporaryBlueprintPlaceRequestedEvent>());
+        return true;
+    case ControlAction::CreateBlueprint:
+        // Decided by MainWindow, the only widget that can pause the game and dim the
+        // window for a modal.
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<BlueprintSaveRequestedEvent>());
+        return true;
+    case ControlAction::OpenBlueprints:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<BlueprintSelectionRequestedEvent>());
+        return true;
+    case ControlAction::OpenMenu:
+        EventManager::getInstance()->sendEventImmediately(
+            std::make_shared<EscapeMenuRequestedEvent>());
+        return true;
+    default:
+        // Either nothing is bound to the key here, or what is bound is a mouse gesture
+        // the view handles. Unconsumed, so ordinary Qt shortcuts keep working.
         return false;
     }
 }
 
-bool InputMapper::handleKeyRelease(QKeyEvent* event)
+bool InputMapper::handleKeyRelease(QKeyEvent* event, const ControlContext& context)
 {
     if (event->isAutoRepeat()) { return false; }
 
-    switch (event->key())
+    // Only held actions have a release worth acting on. Resolved through the table
+    // rather than matched against A and D directly, so the keys stay rebindable in one
+    // place rather than two.
+    if (resolveKeyAction(event->key(), event->modifiers(), context) != ControlAction::Move)
     {
-    case Qt::Key_A:
-        m_panLeftHeld = false;
-        updatePanDirection();
-        return true;
-    case Qt::Key_D:
-        m_panRightHeld = false;
-        updatePanDirection();
-        return true;
-    default:
         return false;
     }
+
+    if (event->key() == Qt::Key_A) { m_panLeftHeld = false; }
+    else                           { m_panRightHeld = false; }
+    updatePanDirection();
+    return true;
 }
 
 void InputMapper::releaseAll()

src/ui/InputMapper.h

@@ -3,14 +3,19 @@
 #include <QString>
 
 #include "BuildingType.h"
+#include "ControlAction.h"
 #include "WorldCamera.h"
 
 class QKeyEvent;
 
 // Turns raw key events into the game's semantic actions and publishes them
 // (REQ-UI-HOTKEYS). Widgets react to the action, never to the key, so the two can
-// be rebound independently later; the bindings themselves are still hard-coded
-// here for now.
+// be rebound independently later.
+//
+// Which key means what is not decided here: the caller hands in a ControlContext and
+// ControlAction.h resolves the press against it, so this file only knows what each
+// action means once resolved. That is what keeps the controls panel and the key
+// handling from drifting apart -- both read the one table (REQ-UI-CONTROLS-ACCURACY).
 //
 // Two output shapes, chosen by the nature of the action rather than by taste:
 //
@@ -34,9 +39,10 @@ public:
     static QString getBuildHotkeyLabel(BuildingType type);
 
     // Both return true when the key was consumed; the caller passes anything else
-    // on to its base class so unrelated shortcuts keep working.
-    bool handleKeyPress(QKeyEvent* event);
-    bool handleKeyRelease(QKeyEvent* event);
+    // on to its base class so unrelated shortcuts keep working. `context` is the
+    // player's current situation, which decides what a key does (REQ-UI-CONTROLS-CONTENT).
+    bool handleKeyPress(QKeyEvent* event, const ControlContext& context);
+    bool handleKeyRelease(QKeyEvent* event, const ControlContext& context);
 
     // Drops all held-key state, publishing the resulting change. Call when the
     // receiving widget can no longer expect key-up events.

src/ui/MainWindow.cpp

@@ -29,6 +29,7 @@
 #include "SchematicChoiceDialog.h"
 #include "HeaderBar.h"
 #include "SelectionPanel.h"
+#include "ControlsPanel.h"
 #include "ShipLayoutBlueprintSerializer.h"
 #include "ShipLayoutDialog.h"
 #include "BuildingIconCache.h"
@@ -77,6 +78,10 @@ MainWindow::MainWindow(Simulation* sim, const std::string& configDir,
     // because only it can pause the game and raise the dim overlay. Built after the
     // world view because loading blueprints.toml may put a message box on screen.
     m_blueprintLibrary = std::make_unique<BlueprintLibrary>(sim, &sim->getConfig(), this);
+    // Two facts about blueprints decide what the world view offers the player
+    // (REQ-UI-CONTROLS-CONTENT); the library is built after the view, so it is handed
+    // over here rather than passed to the constructor.
+    m_gameWorldView->setBlueprintLibrary(m_blueprintLibrary.get());
 
     // Floats over the game world at its right edge rather than occupying a column of
     // its own, and hides itself while nothing is selected (REQ-UI-SELECTION-PANEL). Like
@@ -87,6 +92,11 @@ MainWindow::MainWindow(Simulation* sim, const std::string& configDir,
                                           m_itemIcons.get(), m_buildingIcons.get(),
                                           this);
 
+    // Floats at the world view's opposite edge from the selection panel and reads the
+    // world view for the player's current situation (REQ-UI-CONTROLS-PANEL). Built
+    // after the view for the same stacking reason as the panels above it.
+    m_controlsPanel = new ControlsPanel(m_gameWorldView, this);
+
     // Created last so it stacks above the other children; covers the whole window and
     // dims the game behind modal dialogs/menus (REQ-UI-MODAL-DIM).
     m_dimOverlay = new ModalDimOverlay(m_visuals.overlays.modalDim, this);
@@ -162,14 +172,50 @@ void MainWindow::layoutPanels()
     const QRect worldRect(0, headerH, totalW, totalH - headerH);
     m_headerBar->setGeometry(0, 0, totalW, headerH);
     m_gameWorldView->setGeometry(worldRect);
-    // Sizes itself to its buttons and centers along the bottom of the world view
-    // (REQ-UI-BUILD-BAR).
-    m_buildButtonBar->anchorTo(worldRect);
-    // The panel confines itself to what the bar leaves free, so the bar never has to
-    // move for it (REQ-UI-SELECTION-PANEL, REQ-UI-BUILD-BAR).
-    m_selectionPanel->anchorTo(
-        worldRect.adjusted(0, 0, 0, -m_buildButtonBar->getStripHeightPx()));
     m_dimOverlay->setGeometry(0, 0, totalW, totalH);
+
+    // The floating widgets are placed in one ordered pass, each into the space the
+    // earlier ones have not taken (FloatingPanel.h). The order is the priority the
+    // requirements state: the build button bar takes what it wants and never moves for
+    // anyone (REQ-UI-BUILD-BAR), the controls panel steps around the bar
+    // (REQ-UI-CONTROLS-PANEL), and the selection panel keeps clear of both
+    // (REQ-UI-SELECTION-PANEL). A widget with nothing to show hides itself in placeIn()
+    // and takes no space.
+    //
+    // Re-entry is refused rather than queued: setGeometry() on a widget in the pass can
+    // reach code that asks for another pass, and the one already running is about to
+    // produce the same answer.
+    if (m_layingOut)
+    {
+        return;
+    }
+    m_layingOut = true;
+
+    const std::vector<QWidget*> floatingWidgets = {
+        m_buildButtonBar, m_controlsPanel, m_selectionPanel };
+    const std::vector<FloatingPanel*> floatingPanels = {
+        m_buildButtonBar, m_controlsPanel, m_selectionPanel };
+
+    std::vector<QRect> occupiedRects;
+    for (std::size_t i = 0; i < floatingPanels.size(); ++i)
+    {
+        floatingPanels[i]->placeIn(worldRect, occupiedRects);
+        if (floatingWidgets[i]->isVisible())
+        {
+            occupiedRects.push_back(floatingWidgets[i]->geometry());
+        }
+    }
+
+    m_layingOut = false;
+}
+
+void MainWindow::handleEvent(
+    std::shared_ptr<const FloatingLayoutInvalidatedEvent> /*event*/)
+{
+    // One of the floating widgets changed size or visibility. What each of them may take
+    // depends on the ones placed before it, so the answer is the whole pass rather than
+    // that one widget re-placing itself.
+    layoutPanels();
 }
 
 void MainWindow::handleEvent(std::shared_ptr<const SchematicChoicesAvailableEvent> event)

src/ui/MainWindow.h

@@ -12,6 +12,7 @@
 #include "BuildingId.h"
 #include "EscapeMenuRequestedEvent.h"
 #include "EventHandler.h"
+#include "FloatingLayoutInvalidatedEvent.h"
 #include "GameConfig.h"
 #include "GameOverEvent.h"
 #include "LayoutDialogRequestedEvent.h"
@@ -29,6 +30,7 @@ class Simulation;
 class GameWorldView;
 class HeaderBar;
 class SelectionPanel;
+class ControlsPanel;
 class BuildButtonBar;
 class BlueprintLibrary;
 class BuildingIconCache;
@@ -44,7 +46,8 @@ class MainWindow : public QWidget,
                                                LayoutDialogRequestedEvent,
                                                RecipeSelectionRequestedEvent,
                                                BlueprintSaveRequestedEvent,
-                                               BlueprintSelectionRequestedEvent>
+                                               BlueprintSelectionRequestedEvent,
+                                               FloatingLayoutInvalidatedEvent>
 {
     Q_OBJECT
 
@@ -66,6 +69,7 @@ private:
     void handleEvent(std::shared_ptr<const RecipeSelectionRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const BlueprintSaveRequestedEvent> event) override;
     void handleEvent(std::shared_ptr<const BlueprintSelectionRequestedEvent> event) override;
+    void handleEvent(std::shared_ptr<const FloatingLayoutInvalidatedEvent> event) override;
 
     // Reloads the game config and visuals.toml from disk (REQ-CFG-RELOAD), shared
     // by every restart path. On success the reloaded visuals are applied to this
@@ -84,6 +88,8 @@ private:
     // both callers already hold theirs, which is what keeps the dim continuous when a
     // confirmed save hands straight over to this dialog (REQ-UI-MODAL-DIM).
     void showBlueprintSelectionDialog();
+    // Places the widgets floating over the game world view, in one ordered pass
+    // (FloatingPanel.h). Runs on a resize and on every FloatingLayoutInvalidatedEvent.
     void layoutPanels();
 
 private:
@@ -99,6 +105,7 @@ private:
     GameWorldView*         m_gameWorldView;
     HeaderBar*             m_headerBar;
     SelectionPanel*        m_selectionPanel;
+    ControlsPanel*         m_controlsPanel;
     BuildButtonBar*        m_buildButtonBar;
     // The saved blueprints themselves; they have no widget of their own any more and
     // are reached through the two modal dialogs (REQ-UI-BLUEPRINT-DIALOG).
@@ -107,4 +114,8 @@ private:
 
     std::vector<ShipLayoutBlueprint> m_layoutBlueprints;
     std::shared_ptr<ParsedReplay>    m_replay;  // non-null => view-only playback
+
+    // Set while the placement pass runs, so a widget placed in it cannot start a second
+    // pass from inside the first.
+    bool m_layingOut = false;
 };

src/ui/SelectionBounds.cpp

@@ -0,0 +1,115 @@
+#include "SelectionBounds.h"
+
+#include "Building.h"
+#include "DebrisComponent.h"
+#include "EntityAdmin.h"
+#include "FactoryQueries.h"
+#include "PositionComponent.h"
+#include "Simulation.h"
+#include "StationBodyComponent.h"
+#include "WorldCoordinates.h"
+#include "WorldPrimitives.h"
+
+namespace
+{
+
+// The widget rectangle of a footprint anchored at a tile, both kinds of body being
+// described the same way.
+QRectF getFootprintWidgetRect(const WorldCoordinates& coordinates, QPoint anchor,
+                              QSize footprint)
+{
+    const QPointF topLeft = coordinates.tileToWidget(anchor);
+    return QRectF(topLeft.x(), topLeft.y(),
+                  footprint.width()  * static_cast<qreal>(coordinates.getTilePx()),
+                  footprint.height() * static_cast<qreal>(coordinates.getTilePx()));
+}
+
+}  // namespace
+
+
+std::optional<QRectF> getBuildingWidgetRect(const FactoryState& state,
+                                            const WorldCoordinates& coordinates,
+                                            BuildingId id)
+{
+    if (const Building* building = findBuilding(state, id))
+    {
+        return getFootprintWidgetRect(coordinates, building->anchor, building->footprint);
+    }
+    if (const ConstructionSite* site = findSite(state, id))
+    {
+        return getFootprintWidgetRect(coordinates, site->anchor, site->footprint);
+    }
+    return std::nullopt;
+}
+
+std::optional<QRectF> getActorWidgetRect(const EntityAdmin& admin,
+                                         const WorldCoordinates& coordinates,
+                                         entt::entity actor)
+{
+    if (!admin.isValid(actor))
+    {
+        return std::nullopt;
+    }
+    if (admin.hasAll<StationBodyComponent>(actor))
+    {
+        const StationBodyComponent& body = admin.get<StationBodyComponent>(actor);
+        return getFootprintWidgetRect(coordinates, body.anchor, body.footprint);
+    }
+    if (admin.hasAll<PositionComponent>(actor))
+    {
+        // A ship is a triangle about its center; the square its longest extent fits in
+        // is what the panel is placed beside.
+        const QPointF center =
+            coordinates.worldToWidget(admin.get<PositionComponent>(actor).value);
+        const qreal extent = static_cast<qreal>(getShipForwardExtentPx(coordinates));
+        return QRectF(center.x() - extent, center.y() - extent,
+                      2.0 * extent, 2.0 * extent);
+    }
+    return std::nullopt;
+}
+
+std::optional<QRectF> getDebrisWidgetRect(const EntityAdmin& admin,
+                                          const WorldCoordinates& coordinates,
+                                          entt::entity debris)
+{
+    if (!admin.isValid(debris) || !admin.hasAll<PositionComponent, DebrisComponent>(debris))
+    {
+        return std::nullopt;
+    }
+    const QPointF center =
+        coordinates.worldToWidget(admin.get<PositionComponent>(debris).value);
+    const qreal radius = static_cast<qreal>(getDebrisRadiusPx(coordinates));
+    return QRectF(center.x() - radius, center.y() - radius, 2.0 * radius, 2.0 * radius);
+}
+
+QRect getSelectionWidgetRect(const Simulation& sim, const WorldCoordinates& coordinates,
+                             const std::vector<BuildingId>& buildings,
+                             const std::vector<entt::entity>& actors,
+                             const std::vector<entt::entity>& debris)
+{
+    QRectF bounds;
+    // A null rect unites to nothing of its own, so the first object found sets the box
+    // and every later one grows it.
+    auto add = [&bounds](const std::optional<QRectF>& rect)
+    {
+        if (rect.has_value())
+        {
+            bounds = bounds.isNull() ? *rect : bounds.united(*rect);
+        }
+    };
+
+    for (BuildingId id : buildings)
+    {
+        add(getBuildingWidgetRect(sim.getFactoryState(), coordinates, id));
+    }
+    for (entt::entity actor : actors)
+    {
+        add(getActorWidgetRect(sim.getAdmin(), coordinates, actor));
+    }
+    for (entt::entity piece : debris)
+    {
+        add(getDebrisWidgetRect(sim.getAdmin(), coordinates, piece));
+    }
+
+    return bounds.isNull() ? QRect() : bounds.toAlignedRect();
+}

src/ui/SelectionBounds.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <optional>
+#include <vector>
+
+#include <QRect>
+
+#include "entt/entity/entity.hpp"
+
+#include "BuildingId.h"
+
+class EntityAdmin;
+class Simulation;
+class WorldCoordinates;
+struct FactoryState;
+
+// Where selectable objects are on the screen. The world renderer draws every selection
+// outline from these rectangles, and the selection panel is placed beside the one that
+// covers the whole selection (REQ-UI-SELECTION-PANEL).
+//
+// All of them are in the game world view's own widget coordinates, and all of them are
+// only true for the WorldCoordinates they were asked for: the transform is a value built
+// per frame or per event, so a rectangle does not survive a scroll or a resize.
+
+// The footprint of a building or of a construction site (REQ-UI-SELECTION-CARD). Null
+// when the id names neither, which is what a deconstruction under the caller looks like.
+std::optional<QRectF> getBuildingWidgetRect(const FactoryState& state,
+                                            const WorldCoordinates& coordinates,
+                                            BuildingId id);
+
+// The body of a ship or of a defence station (REQ-UI-ENTITY-CLICK-SELECT): a station's
+// footprint, or the square the ship's triangle is drawn in.
+std::optional<QRectF> getActorWidgetRect(const EntityAdmin& admin,
+                                         const WorldCoordinates& coordinates,
+                                         entt::entity actor);
+
+// The circle a piece of debris is drawn as (REQ-UI-DEBRIS-CLICK-SELECT).
+std::optional<QRectF> getDebrisWidgetRect(const EntityAdmin& admin,
+                                          const WorldCoordinates& coordinates,
+                                          entt::entity debris);
+
+// The rectangle covering a whole selection -- one object, or the bounding box of all of
+// them (REQ-UI-SELECTION-PANEL). Objects that no longer resolve are skipped; the result
+// is null when none of them does.
+QRect getSelectionWidgetRect(const Simulation& sim, const WorldCoordinates& coordinates,
+                             const std::vector<BuildingId>& buildings,
+                             const std::vector<entt::entity>& actors,
+                             const std::vector<entt::entity>& debris);

src/ui/SelectionPanel.cpp

@@ -1,10 +1,15 @@
 #include "SelectionPanel.h"
 
+#include <QLayout>
+#include <QList>
 #include <QScrollArea>
 #include <QScrollBar>
 #include <QVBoxLayout>
 
 #include "BuildingIconCache.h"
+#include "EventManager.h"
+#include "FloatingLayoutInvalidatedEvent.h"
+#include "FloatingPanelPlacement.h"
 #include "ItemIconCache.h"
 #include "Simulation.h"
 #include "VisualsConfig.h"
@@ -13,8 +18,8 @@
 namespace
 {
 
-// Distance kept between the panel and the edges of the band it is anchored to
-// (REQ-UI-SELECTION-PANEL).
+// Distance kept between the panel and the edges of the game world view, and between it
+// and the widgets it steps around (REQ-UI-SELECTION-PANEL).
 const int kMarginPx = 8;
 
 // Upper bound on the card width. The panel is content-sized, but several of the cards'
@@ -62,7 +67,13 @@ SelectionPanel::SelectionPanel(Simulation* sim, const GameConfig* config,
     m_scrollArea->setFrameShape(QFrame::NoFrame);
     m_scrollArea->setWidgetResizable(true);
     m_scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
-    m_scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
+    // The panel works out for itself whether the card fits the band, and sizes itself to
+    // leave room for the bar when it does not (REQ-UI-SELECTION-PANEL), so refit() sets
+    // this policy rather than leaving the scroll area to decide. Asked to decide, it
+    // shows a bar the moment the card is momentarily larger than the viewport -- which
+    // happens while the card is being measured -- and does not take it back when the
+    // range turns out to be empty.
+    m_scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
     m_scrollArea->viewport()->setAutoFillBackground(false);
     m_body->setAutoFillBackground(false);
     m_scrollArea->setWidget(m_body);
@@ -88,10 +99,10 @@ SelectionPanel::~SelectionPanel()
     unregisterForEvents();
 }
 
-void SelectionPanel::anchorTo(const QRect& bandRect)
+void SelectionPanel::invalidateLayout()
 {
-    m_bandRect = bandRect;
-    updateVisibility();
+    EventManager::getInstance()->sendEventImmediately(
+        std::make_shared<FloatingLayoutInvalidatedEvent>());
 }
 
 void SelectionPanel::handleEvent(std::shared_ptr<const SelectionChangedEvent> event)
@@ -107,6 +118,18 @@ void SelectionPanel::handleEvent(std::shared_ptr<const SelectionChangedEvent> ev
     rebuildContent();
 }
 
+void SelectionPanel::handleEvent(
+    std::shared_ptr<const SelectionAnchorChangedEvent> event)
+{
+    // A new selection is starting. Both the anchor and the side are settled against it
+    // and then left alone for as long as it lasts (REQ-UI-SELECTION-PANEL); the side is
+    // only reset here, being resolved on the next placement once the card's width is
+    // known. The rect arrives in the world view's coordinates and is translated when the
+    // panel is placed, the two widgets being siblings in the same parent.
+    m_anchorRect = event->rectPx;
+    m_side.reset();
+}
+
 void SelectionPanel::handleEvent(
     std::shared_ptr<const EntitySelectionChangedEvent> event)
 {
@@ -172,7 +195,7 @@ void SelectionPanel::refreshContent()
     }
 
     m_content->refresh();
-    updateVisibility();
+    invalidateLayout();
 }
 
 void SelectionPanel::rebuildContent()
@@ -193,34 +216,38 @@ void SelectionPanel::rebuildContent()
     if (m_content)
     {
         m_bodyLayout->addWidget(m_content);
+        // The show is what makes the card count. A widget created under an
+        // already-visible parent starts hidden, and a layout treats a hidden item as
+        // empty -- it adds nothing to the size hint until something shows it, which
+        // otherwise does not happen until the event loop next runs, long after refit()
+        // has measured the panel. The panel then fits itself to an empty body and
+        // collapses to its scroll bar.
+        m_content->show();
         m_content->refresh();
     }
-    updateVisibility();
+    invalidateLayout();
 }
 
-void SelectionPanel::updateVisibility()
+void SelectionPanel::placeIn(const QRect& viewRect, const std::vector<QRect>& occupiedRects)
 {
     // Nothing selected in either category means no panel at all rather than an empty one
-    // (REQ-UI-EMPTY-SELECTION), leaving the whole game world view visible. Before the
-    // owner has anchored the panel there is nowhere to put it either, so it stays hidden
-    // until then.
-    const bool shouldShow = (m_content != nullptr) && !m_bandRect.isNull();
-    setVisible(shouldShow);
-    if (shouldShow)
+    // (REQ-UI-EMPTY-SELECTION), leaving the whole game world view visible.
+    setVisible(m_content != nullptr);
+    if (m_content == nullptr || viewRect.isNull())
     {
-        refit();
+        return;
     }
-}
 
-void SelectionPanel::refit()
-{
-    // The layout drops hidden widgets from its size hint, but only once it has been
-    // re-run: a card hides and shows its parts as it refreshes, before Qt would get
-    // around to it on its own.
-    m_body->layout()->activate();
+    const QRect band = viewRect.adjusted(kMarginPx, kMarginPx, -kMarginPx, -kMarginPx);
 
-    const QRect band =
-        m_bandRect.adjusted(kMarginPx, kMarginPx, -kMarginPx, -kMarginPx);
+    // The anchor is published in the world view's coordinates and this panel is placed in
+    // its parent's; the two widgets are siblings, so the view's own origin is the whole
+    // difference. Without an anchor the panel falls back to the top-right corner, by
+    // standing beside a point just outside that corner -- in practice unreachable, every
+    // non-empty selection following a click or a drag that publishes one.
+    const QRect anchorRect =
+        m_anchorRect.isNull() ? QRect(band.right() + kMarginPx + 1, band.top(), 1, 1)
+                              : m_anchorRect.translated(viewRect.topLeft());
 
     // The panel's border is drawn around the scroll area rather than around the card, so
     // it is added to whatever the card asks for. Spelled out here instead of read back
@@ -228,40 +255,115 @@ void SelectionPanel::refit()
     // style for it before the first show is unreliable.
     const int borderPx   = 1;
     const int maxWidthPx = qMin(kMaxContentWidthPx, band.width() - 2 * borderPx);
-    const int maxHeightPx = band.height() - 2 * borderPx;
-    if (maxWidthPx <= 0 || maxHeightPx <= 0)
+    if (maxWidthPx <= 0 || band.height() <= 2 * borderPx)
     {
         return;
     }
 
-    int contentWidthPx = qMin(m_body->sizeHint().width(), maxWidthPx);
-    // Word-wrapped labels only know their height once the width is fixed; the layout
-    // reports -1 when nothing in it wraps, in which case the plain hint is exact.
-    int contentHeightPx = m_body->heightForWidth(contentWidthPx);
-    if (contentHeightPx < 0)
+    // What the card asks for at a given width. The width has to be applied before
+    // asking, because a card's height depends on the room it is given -- and so, once
+    // laid out, does the width it reports. Measuring at whatever width the panel
+    // happens to have carries the previous card's shape into this one.
+    //
+    // Each measurement re-runs the card's layouts -- every one of them, not just the
+    // body's own. Changing a label's text posts a LayoutRequest to the widget holding it
+    // and that event is only delivered when the event loop next runs, so a layout nested
+    // inside the card still reports the width of the text before the change: measuring
+    // here and re-measuring on the following refresh then gives two different answers,
+    // and the panel visibly resizes a frame after its content changed. Re-activating
+    // them all is what a delivered LayoutRequest would have done.
+    //
+    // Cards are built and discarded whole, so this is also what discards the previous
+    // card's cached hints, and what accounts for the parts a card hides and shows as it
+    // refreshes. The polish belongs to the same step: a freshly created chip reports an
+    // unstyled hint until the stylesheet has reached it, and the chips carry border and
+    // padding that change their size.
+    auto measureAt = [this](int widthPx) -> QSize
     {
-        contentHeightPx = m_body->sizeHint().height();
+        m_body->resize(widthPx, m_body->height());
+        m_body->ensurePolished();
+
+        // Deepest first, so no layout is re-activated from children that are themselves
+        // still stale. findChildren walks parents before children, hence the reverse.
+        const QList<QLayout*> nested = m_body->findChildren<QLayout*>();
+        for (QList<QLayout*>::const_reverse_iterator it = nested.rbegin();
+             it != nested.rend(); ++it)
+        {
+            (*it)->invalidate();
+            (*it)->activate();
+        }
+        m_body->layout()->invalidate();
+        m_body->layout()->activate();
+        return m_body->sizeHint();
+    };
+
+    // Run twice. Parts of a card report an unstyled size until the style has actually
+    // reached them, which for a freshly built card happens during the first round of
+    // measuring; the second round then measures a card that is fully laid out and
+    // settles on the answer. Without it a card can end up a few pixels short of what it
+    // turns out to need, and the difference shows as a scroll bar over a card that
+    // looks like it fits.
+    for (int pass = 0; pass < 2; ++pass)
+    {
+        // First at the cap, the most room the card can ever get, to learn how wide it
+        // wants to be; then at that width for the height that follows from it.
+        int contentWidthPx  = qMin(measureAt(maxWidthPx).width(), maxWidthPx);
+
+        // Which side of the selection the panel takes is settled on the first placement
+        // after a new anchor and kept for as long as that selection lasts, so a card that
+        // grows or shrinks never flips the panel across the object it describes
+        // (REQ-UI-SELECTION-PANEL). This is the first point at which its width is known.
+        if (!m_side.has_value())
+        {
+            m_side = chooseSide(band, anchorRect, contentWidthPx + 2 * borderPx,
+                                kMarginPx);
         }
 
-    if (contentHeightPx > maxHeightPx)
+        // How much height there is depends on where the panel ends up standing: of the
+        // widgets placed before it, only those whose rectangles meet its own column are
+        // in its way. That column follows from the width just measured, so this cannot be
+        // settled before it -- and where the scroll bar below widens the panel, the second
+        // pass settles it again against the wider column. Asking for the whole band's
+        // height is what makes the answer the most the panel could have there.
+        const int maxHeightPx =
+            placeBesideAnchor(band, anchorRect, *m_side,
+                              QSize(contentWidthPx + 2 * borderPx, band.height()),
+                              occupiedRects, kMarginPx).height() - 2 * borderPx;
+        if (maxHeightPx <= 0)
         {
-        // A card taller than the band is capped there and scrolls
-        // (REQ-UI-SELECTION-PANEL). The scroll bar is laid out beside the card, so the
-        // panel widens by its width to keep the card as wide as the height was computed
-        // for.
-        contentHeightPx = maxHeightPx;
-        contentWidthPx  = qMin(
-            contentWidthPx + m_scrollArea->verticalScrollBar()->sizeHint().width(),
-            maxWidthPx);
+            return;
         }
 
+        int contentHeightPx = measureAt(contentWidthPx).height();
+
+        // A card taller than the space left is capped there and scrolls
+        // (REQ-UI-SELECTION-PANEL). The bar is laid out beside the card, so the panel
+        // widens by its width to leave the card the width its height was measured for --
+        // and where the cap does not allow that, the card is measured again at what is
+        // left over.
+        const bool scrolls = (contentHeightPx > maxHeightPx);
+        int viewportWidthPx = contentWidthPx;
+        if (scrolls)
+        {
+            const int scrollBarWidthPx =
+                m_scrollArea->verticalScrollBar()->sizeHint().width();
+            contentWidthPx  = qMin(contentWidthPx + scrollBarWidthPx, maxWidthPx);
+            contentHeightPx = maxHeightPx;
+            viewportWidthPx = contentWidthPx - scrollBarWidthPx;
+            measureAt(viewportWidthPx);
+        }
+        m_scrollArea->setVerticalScrollBarPolicy(
+            scrolls ? Qt::ScrollBarAlwaysOn : Qt::ScrollBarAlwaysOff);
+
+        // Left at the size the scroll area is about to give it, so the card is not
+        // briefly wider than its viewport.
+        m_body->resize(viewportWidthPx, m_body->sizeHint().height());
+
         const int panelWidthPx  = contentWidthPx + 2 * borderPx;
         const int panelHeightPx = contentHeightPx + 2 * borderPx;
 
-    // Right-aligned in the band and centered on it vertically. The band excludes the
-    // build button bar's strip, so centering here never puts the panel over the bar
-    // (REQ-UI-SELECTION-PANEL).
-    setGeometry(band.right() - panelWidthPx + 1,
-                band.top() + (band.height() - panelHeightPx) / 2,
-                panelWidthPx, panelHeightPx);
+        setGeometry(placeBesideAnchor(band, anchorRect, *m_side,
+                                      QSize(panelWidthPx, panelHeightPx),
+                                      occupiedRects, kMarginPx));
+    }
 }

src/ui/SelectionPanel.h

@@ -3,11 +3,17 @@
 #include <QRect>
 #include <QWidget>
 
+#include <optional>
+#include <vector>
+
 #include "DebrisSelectionChangedEvent.h"
 #include "DebugDrawToggledEvent.h"
 #include "EntitySelectionChangedEvent.h"
 #include "EventHandler.h"
+#include "FloatingPanel.h"
+#include "FloatingPanelPlacement.h"
 #include "PlayerCommandsAppliedEvent.h"
+#include "SelectionAnchorChangedEvent.h"
 #include "SelectionChangedEvent.h"
 #include "TickAdvancedEvent.h"
 #include "selection/SelectionContentFactory.h"
@@ -28,14 +34,16 @@ class QVBoxLayout;
 // What each card looks like lives in src/ui/selection/.
 //
 // The panel floats over the game world view rather than occupying a column of its own
-// (REQ-UI-SELECTION-PANEL): it sizes itself to its card, anchors to the right edge of
-// the band its owner hands it, and hides itself entirely while nothing is selected
-// (REQ-UI-EMPTY-SELECTION).
+// (REQ-UI-SELECTION-PANEL): it sizes itself to its card, places itself in what the build
+// button bar and the controls panel have left free, and hides itself entirely while
+// nothing is selected (REQ-UI-EMPTY-SELECTION).
 class SelectionPanel : public QWidget,
+                       public FloatingPanel,
                        public CombinedEventHandler<TickAdvancedEvent,
                                                    PlayerCommandsAppliedEvent,
                                                    EntitySelectionChangedEvent,
                                                    SelectionChangedEvent,
+                                                   SelectionAnchorChangedEvent,
                                                    DebrisSelectionChangedEvent,
                                                    DebugDrawToggledEvent>
 {
@@ -49,14 +57,16 @@ public:
                    BuildingIconCache* buildingIcons, QWidget* parent = nullptr);
     ~SelectionPanel() override;
 
-    // Confines the panel to the given band of the game world view: it right-aligns
-    // within it and centers vertically in it. The band is the world view less the strip
-    // the build button bar occupies, so the two never overlap and the bar never has to
-    // move (REQ-UI-SELECTION-PANEL, REQ-UI-BUILD-BAR).
-    void anchorTo(const QRect& bandRect);
+    // Sizes the panel to its card and places it beside the selection it describes, in
+    // what the widgets placed before it have left free. Keeping clear of them is entirely
+    // this panel's job; neither of them ever moves for it (REQ-UI-SELECTION-PANEL,
+    // REQ-UI-BUILD-BAR, REQ-UI-CONTROLS-PANEL).
+    void placeIn(const QRect& viewRect,
+                 const std::vector<QRect>& occupiedRects) override;
 
 private:
     void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const SelectionAnchorChangedEvent> event) override;
     void handleEvent(std::shared_ptr<const EntitySelectionChangedEvent> event) override;
     void handleEvent(std::shared_ptr<const DebrisSelectionChangedEvent> event) override;
     void handleEvent(std::shared_ptr<const TickAdvancedEvent> event) override;
@@ -69,11 +79,9 @@ private:
     void refreshContent();
     // Replaces the card with the one the current selection calls for.
     void rebuildContent();
-    // Shows the panel while a card exists and hides it otherwise
-    // (REQ-UI-EMPTY-SELECTION), re-fitting it to the card while it is shown.
-    void updateVisibility();
-    // Re-fits the panel to its card within the anchored band.
-    void refit();
+    // Asks for the placement pass to be re-run, the card having changed size or the
+    // panel having gained or lost its reason to be shown at all.
+    void invalidateLayout();
 
     SelectionContext m_context;
     // Read through m_context by the cards that need it, so a toggle reaches the card on
@@ -84,12 +92,18 @@ private:
     ContentKey        m_contentKey;
     SelectionContent* m_content = nullptr;
 
-    // The band the panel confines itself to, in the coordinates of its parent; null
-    // until the owner has anchored it for the first time.
-    QRect m_bandRect;
+    // Where the current selection was on the screen when it started, in the game world
+    // view's coordinates, and which side of it the panel took. Both are frozen for as
+    // long as the selection lasts: the anchor because the panel does not chase a
+    // scrolling view or a moving ship, the side because a card that grows must not flip
+    // the panel across the object (REQ-UI-SELECTION-PANEL). The side is resolved on the
+    // first placement after a new anchor, being the first point at which the panel's
+    // width is known.
+    QRect                    m_anchorRect;
+    std::optional<PanelSide> m_side;
 
-    // Scrolls the card once it outgrows the band (REQ-UI-SELECTION-PANEL). The card is a
-    // child of m_body, not of the panel itself.
+    // Scrolls the card once it outgrows the space the panel has (REQ-UI-SELECTION-PANEL).
+    // The card is a child of m_body, not of the panel itself.
     QScrollArea* m_scrollArea;
     QWidget*     m_body;
     QVBoxLayout* m_bodyLayout;

src/ui/WorldRenderer.cpp

@@ -35,6 +35,7 @@
 #include "ProductionRules.h"
 #include "RepairBehavior.h"
 #include "SalvageScrapBehavior.h"
+#include "SelectionBounds.h"
 #include "SensorRangeComponent.h"
 #include "ShipIdentityComponent.h"
 #include "Simulation.h"
@@ -108,7 +109,7 @@ QColor statusLightFill(ProductionStatus status, const StatusLightVisuals& sl)
 
 }  // namespace
 
-WorldRenderer::WorldRenderer(Simulation& sim, const VisualsConfig& visuals,
+WorldRenderer::WorldRenderer(const Simulation& sim, const VisualsConfig& visuals,
                              ItemIconCache* itemIcons, const std::string& configDir)
     : m_sim(sim)
     , m_visuals(visuals)
@@ -451,30 +452,6 @@ void WorldRenderer::drawBuildings(QPainter& painter, const WorldCoordinates& coo
     drawSelectionHighlights(painter, coordinates, frame);
 }
 
-std::optional<QRectF> WorldRenderer::footprintWidgetRect(
-    const WorldCoordinates& coordinates, BuildingId id) const
-{
-    std::optional<QPoint> anchor;
-    std::optional<QSize>  footprint;
-
-    if (const Building* b = findBuilding(m_sim.getFactoryState(), id))
-    {
-        anchor    = b->anchor;
-        footprint = b->footprint;
-    }
-    else if (const ConstructionSite* s = findSite(m_sim.getFactoryState(), id))
-    {
-        anchor    = s->anchor;
-        footprint = s->footprint;
-    }
-    if (!anchor.has_value() || !footprint.has_value()) { return std::nullopt; }
-
-    const QPointF tl = coordinates.tileToWidget(*anchor);
-    return QRectF(tl.x(), tl.y(),
-        footprint->width()  * static_cast<qreal>(coordinates.getTilePx()),
-        footprint->height() * static_cast<qreal>(coordinates.getTilePx()));
-}
-
 void WorldRenderer::drawSelectionHighlights(QPainter& painter, const WorldCoordinates& coordinates,
                                             const WorldRenderFrame& frame)
 {
@@ -483,7 +460,8 @@ void WorldRenderer::drawSelectionHighlights(QPainter& painter, const WorldCoordi
 
     for (BuildingId selId : frame.selection.getSelectedBuildings())
     {
-        const std::optional<QRectF> rect = footprintWidgetRect(coordinates, selId);
+        const std::optional<QRectF> rect =
+            getBuildingWidgetRect(m_sim.getFactoryState(), coordinates, selId);
         if (!rect.has_value()) { continue; }
         // Outline sits 1px outside the footprint (into adjacent tiles).
         painter.drawRect(rect->adjusted(-1, -1, 1, 1));

src/ui/WorldRenderer.h

@@ -77,7 +77,7 @@ public:
     // `itemIcons` is the window-wide per-item icon cache (REQ-UI-ITEM-ICON); not
     // owned, must outlive this renderer. `configDir` is used once, to load the
     // per-building world icons.
-    WorldRenderer(Simulation& sim, const VisualsConfig& visuals,
+    WorldRenderer(const Simulation& sim, const VisualsConfig& visuals,
                   ItemIconCache* itemIcons, const std::string& configDir);
     ~WorldRenderer();
 
@@ -139,16 +139,10 @@ private:
                           BuildingType type, const QRectF& box,
                           const QColor& fill) const;
 
-    // Widget-space rectangle covering a building or construction site's footprint,
-    // or nullopt if the id resolves to neither. Used by the selection highlight.
-    std::optional<QRectF> footprintWidgetRect(const WorldCoordinates& coordinates,
-                                              BuildingId id) const;
-
     std::optional<QVector2D> entityPosition(entt::entity entity) const;
 
-    // Non-const only because EntityAdmin's component accessors are; the renderer
-    // reads the simulation and never writes it.
-    Simulation&          m_sim;
+    // The renderer reads the simulation and never writes it.
+    const Simulation&    m_sim;
     const VisualsConfig& m_visuals;
 
     // Per-item icon cache (REQ-UI-ITEM-ICON), shared window-wide and owned by

src/ui/selection/AutoProductionContent.cpp

@@ -3,6 +3,7 @@
 #include "Building.h"
 #include "BuildingTarget.h"
 #include "GameConfig.h"
+#include "ProductionRules.h"
 
 AutoProductionContent::AutoProductionContent(const SelectionContext& context,
                                              const SelectionRequest& request,
@@ -19,13 +20,43 @@ BufferedBuildingContent::CycleInfo AutoProductionContent::getCycleInfo(
     // REQ-BLD-REPROCESSING), so its production section is always shown -- but only a
     // running cycle names a recipe, so while it is idle there is no cycle to describe.
     info.runsProduction = true;
-    if (!target.building || !target.building->production.has_value())
+
+    if (target.building)
+    {
+        // What the building handles at all, so its buffers are not blank whenever it
+        // happens to be between cycles (REQ-UI-SINGLE-SELECTION). This is the same union
+        // of every recipe of its type that the simulation sized the buffers over, and
+        // the locked ones among them are dropped when the card lists them.
+        for (const RecipeDef* recipe :
+             gatherCandidateRecipes(*getContext().config, *target.building))
+        {
+            for (const RecipeIngredient& ingredient : recipe->inputs)
+            {
+                info.handledInputs.push_back(ingredient.item);
+            }
+            for (const RecipeOutput& output : recipe->outputs)
+            {
+                info.handledOutputs.push_back(output.item);
+            }
+        }
+    }
+
+    // Which recipe describes the cycle: the one running, or -- between cycles -- the one
+    // that ran last. Dropping it while idle would take the summary row and the chips'
+    // per-cycle amounts away and bring them back with every cycle, resizing the card in
+    // step with the building's status (REQ-UI-RECIPE-SUMMARY). Only a building that has
+    // never run has nothing to describe.
+    if (target.building && target.building->production.has_value())
+    {
+        m_lastRecipeId = target.building->production->recipeId;
+    }
+    if (!target.building || m_lastRecipeId.empty())
     {
         return info;
     }
 
-    const RecipeDef* recipe = getContext().config->recipes.findRecipeDef(
-        target.building->production->recipeId, target.type);
+    const RecipeDef* recipe =
+        getContext().config->recipes.findRecipeDef(m_lastRecipeId, target.type);
     if (!recipe)
     {
         return info;

src/ui/selection/AutoProductionContent.h

@@ -1,12 +1,14 @@
 #pragma once
 
+#include <string>
+
 #include "BufferedBuildingContent.h"
 #include "SelectionContentFactory.h"
 
 // The card for a Smelter or a Reprocessing Plant (REQ-UI-SELECTION-CONTENT). Both
 // auto-process whatever they receive and have no player-facing recipe selection
 // (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING), so the card has no configuration group at
-// all; its cycle is whichever recipe is currently in production.
+// all; its cycle is whichever recipe is in production, or the last one that was.
 class AutoProductionContent : public BufferedBuildingContent
 {
     Q_OBJECT
@@ -17,4 +19,11 @@ public:
 
 protected:
     CycleInfo getCycleInfo(const BuildingTarget& target) const override;
+
+private:
+    // The recipe last seen in production, which keeps describing the cycle while the
+    // building sits between cycles (REQ-UI-RECIPE-SUMMARY). Mutable because it is a
+    // record of what getCycleInfo() has observed rather than state of its own: the card
+    // shows the same thing whether or not it has been asked before.
+    mutable std::string m_lastRecipeId;
 };

src/ui/selection/BarRow.cpp

@@ -50,9 +50,14 @@ public:
 protected:
     void paintEvent(QPaintEvent* /*event*/) override
     {
+        // The active group is asked for by name rather than taken from the current one,
+        // which follows the window's focus: the inactive group's highlight is close
+        // enough to the card's background that the bar reads as gone whenever the game
+        // is tabbed away from or a modal dialog holds focus -- exactly when a player
+        // watching a build finish is most likely to be looking at it.
         const QColor fill = m_fillColor.isValid()
             ? m_fillColor
-            : palette().color(QPalette::Highlight);
+            : palette().color(QPalette::Active, QPalette::Highlight);
 
         QColor track = fill;
         track.setAlpha(kTrackAlpha);

src/ui/selection/BufferSection.cpp

@@ -1,103 +0,0 @@
-#include "BufferSection.h"
-
-#include <vector>
-
-#include <QVBoxLayout>
-
-#include "Building.h"
-#include "DisplayName.h"
-#include "ItemChipRow.h"
-#include "SectionBox.h"
-
-namespace
-{
-
-int findPerCycle(const std::map<std::string, int>& perCycle, const std::string& itemId)
-{
-    const std::map<std::string, int>::const_iterator it = perCycle.find(itemId);
-    return (it != perCycle.end()) ? it->second : 0;
-}
-
-}  // namespace
-
-
-BufferSection::BufferSection(const SelectionContext& context, QWidget* parent)
-    : QWidget(parent)
-{
-    QVBoxLayout* layout = new QVBoxLayout(this);
-    layout->setContentsMargins(0, 0, 0, 0);
-    layout->setSpacing(6);
-
-    m_inputSection = new SectionBox(tr("Input buffers"), this);
-    m_inputChips   = new ItemChipRow(context.itemIcons, m_inputSection);
-    m_inputSection->getContentLayout()->addWidget(m_inputChips);
-
-    m_outputSection = new SectionBox(tr("Output buffer"), this);
-    m_outputChips   = new ItemChipRow(context.itemIcons, m_outputSection);
-    m_outputSection->getContentLayout()->addWidget(m_outputChips);
-
-    layout->addWidget(m_inputSection);
-    layout->addWidget(m_outputSection);
-}
-
-void BufferSection::setBuffers(const Building& building,
-                               const std::map<std::string, int>& perCycleInputs,
-                               const std::map<std::string, int>& perCycleOutputs)
-{
-    std::vector<ItemChipRow::Entry> inputs;
-    for (const std::pair<const ItemType, int>& entry : building.inputBuffer.counts)
-    {
-        ItemChipRow::Entry chip;
-        chip.itemId    = entry.first.id;
-        chip.countText = QString::number(entry.second);
-
-        const int perCycle = findPerCycle(perCycleInputs, entry.first.id);
-        if (perCycle > 0)
-        {
-            chip.subLine = tr("/ %1 per cycle").arg(perCycle);
-        }
-        inputs.push_back(chip);
-    }
-
-    // Output-side items are the buffered ones plus those still emerging onto the output
-    // belts: an emerging item still belongs to the output buffer (REQ-MAT-OUTPUT-EMERGE),
-    // so leaving it out would make it vanish from the panel while it animates.
-    std::map<std::string, int> outputCounts;
-    for (const Item& item : building.outputBuffer.items)
-    {
-        outputCounts[item.type.id]++;
-    }
-    for (const std::vector<BeltItemSlot>& lane : building.emergingItems)
-    {
-        for (const BeltItemSlot& slot : lane)
-        {
-            outputCounts[slot.item.type.id]++;
-        }
-    }
-    // A configured building lists everything its cycle produces, so an output the player
-    // is waiting for reads as 0 rather than being absent.
-    for (const std::pair<const std::string, int>& entry : perCycleOutputs)
-    {
-        outputCounts.emplace(entry.first, 0);
-    }
-
-    std::vector<ItemChipRow::Entry> outputs;
-    for (const std::pair<const std::string, int>& entry : outputCounts)
-    {
-        ItemChipRow::Entry chip;
-        chip.itemId = entry.first;
-        // Counted against the buffer's capacity, which is what production stops at
-        // (REQ-MAT-OUTPUT-BUFFER).
-        chip.countText = building.outputBuffer.capacity > 0
-            ? tr("%1 / %2").arg(entry.second).arg(building.outputBuffer.capacity)
-            : QString::number(entry.second);
-        chip.subLine = QString::fromStdString(toDisplayName(entry.first));
-        outputs.push_back(chip);
-    }
-
-    m_inputChips->setEntries(inputs);
-    m_outputChips->setEntries(outputs);
-    m_inputSection->setVisible(!inputs.empty());
-    m_outputSection->setVisible(!outputs.empty());
-    setVisible(!inputs.empty() || !outputs.empty());
-}

src/ui/selection/BufferSection.h

@@ -1,39 +0,0 @@
-#pragma once
-
-#include <map>
-#include <string>
-
-#include <QWidget>
-
-#include "SelectionContext.h"
-
-struct Building;
-class ItemChipRow;
-class SectionBox;
-
-// The input and output buffer contents of one building, each a captioned section of item
-// chips (REQ-UI-SINGLE-SELECTION).
-//
-// Counting what is in the buffers is the same for every building type, so it happens
-// here; what a cycle consumes and produces is not, so the owning content supplies those
-// per-cycle amounts. An item with no entry in the maps is shown without a denominator,
-// and a section holding nothing is not shown at all.
-class BufferSection : public QWidget
-{
-    Q_OBJECT
-
-public:
-    explicit BufferSection(const SelectionContext& context, QWidget* parent = nullptr);
-
-    // perCycleInputs and perCycleOutputs map an item id to the amount one production
-    // cycle consumes or produces. Both may be empty, for a building that runs no cycle.
-    void setBuffers(const Building& building,
-                    const std::map<std::string, int>& perCycleInputs,
-                    const std::map<std::string, int>& perCycleOutputs);
-
-private:
-    SectionBox*  m_inputSection;
-    ItemChipRow* m_inputChips;
-    SectionBox*  m_outputSection;
-    ItemChipRow* m_outputChips;
-};

src/ui/selection/BufferedBuildingContent.cpp

@@ -1,15 +1,17 @@
 #include "BufferedBuildingContent.h"
 
-#include <vector>
+#include <map>
+#include <set>
 
 #include <QVBoxLayout>
 
 #include "Building.h"
-#include "BufferSection.h"
 #include "BuildingTarget.h"
+#include "DisplayName.h"
 #include "FactoryQueries.h"
 #include "ProductionSection.h"
 #include "RecipeSummaryRow.h"
+#include "SectionBox.h"
 #include "SelectionNames.h"
 #include "Simulation.h"
 
@@ -27,6 +29,33 @@ std::vector<RecipeSummaryRow::Amount> toAmounts(const std::map<std::string, int>
     return amounts;
 }
 
+// Every item one side of the card should list: what the buffer holds, what a cycle
+// moves, and what the building handles at all. A building's buffers can carry items it
+// is not currently making anything of, and an auto-recipe building between cycles names
+// nothing at all, so the three sources are unioned rather than one being picked.
+std::set<std::string> collectItemIds(const std::map<std::string, int>& buffered,
+                                     const std::map<std::string, int>& perCycle,
+                                     const std::vector<std::string>& handled)
+{
+    std::set<std::string> itemIds;
+    for (const std::pair<const std::string, int>& entry : buffered)
+    {
+        itemIds.insert(entry.first);
+    }
+    for (const std::pair<const std::string, int>& entry : perCycle)
+    {
+        itemIds.insert(entry.first);
+    }
+    itemIds.insert(handled.begin(), handled.end());
+    return itemIds;
+}
+
+int lookUp(const std::map<std::string, int>& map, const std::string& key)
+{
+    const std::map<std::string, int>::const_iterator it = map.find(key);
+    return (it != map.end()) ? it->second : 0;
+}
+
 }  // namespace
 
 
@@ -40,10 +69,21 @@ BufferedBuildingContent::BufferedBuildingContent(const SelectionContext& context
     m_recipeSummary = new RecipeSummaryRow(context.itemIcons, this);
     getConfigurationLayout()->addWidget(m_recipeSummary);
 
-    m_buffers = new BufferSection(context, this);
+    m_inputSection = new SectionBox(tr("Input buffers"), this);
+    m_inputChips   = new ItemChipRow(context.itemIcons, m_inputSection);
+    m_inputSection->getContentLayout()->addWidget(m_inputChips);
+
     m_production = new ProductionSection(this);
-    getRuntimeLayout()->addWidget(m_buffers);
+
+    m_outputSection = new SectionBox(tr("Output buffer"), this);
+    m_outputChips   = new ItemChipRow(context.itemIcons, m_outputSection);
+    m_outputSection->getContentLayout()->addWidget(m_outputChips);
+
+    // In the direction the materials flow: what goes in, what is being made of it, what
+    // has come out (REQ-UI-SINGLE-SELECTION, REQ-UI-PRODUCTION-PROGRESS).
+    getRuntimeLayout()->addWidget(m_inputSection);
     getRuntimeLayout()->addWidget(m_production);
+    getRuntimeLayout()->addWidget(m_outputSection);
 }
 
 void BufferedBuildingContent::refreshConfiguration()
@@ -77,8 +117,93 @@ void BufferedBuildingContent::refreshRuntime()
     setProductionStatusSlot(*target.building);
 
     const CycleInfo cycle = getCycleInfo(target);
-    m_buffers->setBuffers(*target.building, cycle.perCycleInputs, cycle.perCycleOutputs);
+
+    const std::vector<ItemChipRow::Entry> inputs =
+        buildInputEntries(*target.building, cycle);
+    const std::vector<ItemChipRow::Entry> outputs =
+        buildOutputEntries(*target.building, cycle);
+
+    m_inputChips->setEntries(inputs);
+    m_outputChips->setEntries(outputs);
+    m_inputSection->setVisible(!inputs.empty());
+    m_outputSection->setVisible(!outputs.empty());
+
     m_production->setProduction(cycle.runsProduction, *target.building,
                                 cycle.durationSeconds,
                                 getContext().sim->getCurrentTick());
 }
+
+std::vector<ItemChipRow::Entry> BufferedBuildingContent::buildInputEntries(
+    const Building& building, const CycleInfo& cycle) const
+{
+    std::map<std::string, int> buffered;
+    for (const std::pair<const ItemType, int>& entry : building.inputBuffer.counts)
+    {
+        buffered[entry.first.id] = entry.second;
+    }
+
+    std::vector<ItemChipRow::Entry> entries;
+    for (const std::string& itemId :
+         collectItemIds(buffered, cycle.perCycleInputs, cycle.handledInputs))
+    {
+        // An auto-recipe building's buffers are sized over every recipe of its type,
+        // including recipes still locked, so those entries are left out here
+        // (REQ-UI-SINGLE-SELECTION, REQ-LOCK-UI-RECIPE).
+        if (!getContext().sim->isItemUnlocked(itemId)) { continue; }
+
+        ItemChipRow::Entry chip;
+        chip.itemId    = itemId;
+        chip.countText = QString::number(lookUp(buffered, itemId));
+
+        const int perCycle = lookUp(cycle.perCycleInputs, itemId);
+        if (perCycle > 0)
+        {
+            chip.subLine = tr("/ %1 per cycle").arg(perCycle);
+        }
+        else
+        {
+            chip.subLine = QString::fromStdString(toDisplayName(itemId));
+        }
+        entries.push_back(chip);
+    }
+    return entries;
+}
+
+std::vector<ItemChipRow::Entry> BufferedBuildingContent::buildOutputEntries(
+    const Building& building, const CycleInfo& cycle) const
+{
+    // The buffered items plus those still emerging onto the output belts: an emerging
+    // item still belongs to the output buffer (REQ-MAT-OUTPUT-EMERGE), so leaving it out
+    // would make it vanish from the panel while it animates.
+    std::map<std::string, int> buffered;
+    for (const Item& item : building.outputBuffer.items)
+    {
+        buffered[item.type.id]++;
+    }
+    for (const std::vector<BeltItemSlot>& lane : building.emergingItems)
+    {
+        for (const BeltItemSlot& slot : lane)
+        {
+            buffered[slot.item.type.id]++;
+        }
+    }
+
+    std::vector<ItemChipRow::Entry> entries;
+    for (const std::string& itemId :
+         collectItemIds(buffered, cycle.perCycleOutputs, cycle.handledOutputs))
+    {
+        if (!getContext().sim->isItemUnlocked(itemId)) { continue; }
+
+        ItemChipRow::Entry chip;
+        chip.itemId = itemId;
+        // Counted against the buffer's capacity, which is what production stops at
+        // (REQ-MAT-OUTPUT-BUFFER).
+        chip.countText = building.outputBuffer.capacity > 0
+            ? tr("%1 / %2").arg(lookUp(buffered, itemId))
+                           .arg(building.outputBuffer.capacity)
+            : QString::number(lookUp(buffered, itemId));
+        chip.subLine = QString::fromStdString(toDisplayName(itemId));
+        entries.push_back(chip);
+    }
+    return entries;
+}

src/ui/selection/BufferedBuildingContent.h

@@ -2,20 +2,23 @@
 
 #include <map>
 #include <string>
+#include <vector>
 
 #include "BuildingId.h"
+#include "ItemChipRow.h"
 #include "SelectionContent.h"
 
+struct Building;
 struct BuildingTarget;
-class BufferSection;
 class ProductionSection;
 class RecipeSummaryRow;
+class SectionBox;
 
 // Shared body of the four cards that show one building with buffers -- the Miner and
 // Assembler, the Smelter and Reprocessing Plant, the Shipyard, and the Salvage Bay
-// (REQ-UI-SELECTION-CONTENT). All four show the same header identity and status, recipe
-// summary, buffer contents and production progress; they differ only in what one
-// production cycle costs and how long it takes, which is what the subclass supplies.
+// (REQ-UI-SELECTION-CONTENT). All four show the same header status, recipe summary,
+// buffer contents and production progress; they differ only in what one production cycle
+// costs and how long it takes, which is what the subclass supplies.
 //
 // This is implementation sharing, not a catalog entry: every concrete subclass is one
 // row of the content catalog.
@@ -29,12 +32,21 @@ protected:
     {
         std::map<std::string, int> perCycleInputs;
         std::map<std::string, int> perCycleOutputs;
+
+        // Items the card lists whether or not they are currently in the buffers, for a
+        // building whose recipe is implicit and so has nothing to name while it sits
+        // between cycles (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING). They carry no
+        // per-cycle denominator, since no one recipe is in force.
+        std::vector<std::string> handledInputs;
+        std::vector<std::string> handledOutputs;
+
         // False when the building produces nothing at all (the Salvage Bay,
         // REQ-BLD-SALVAGE-BAY) or has no recipe or schematic selected yet: the
         // production section is then not shown (REQ-UI-PRODUCTION-PROGRESS).
         bool runsProduction = false;
-        // 0 while an auto-recipe building sits between cycles, when no single recipe
-        // names a cycle time; the progress line then reads "idle".
+        // 0 only when no recipe describes the cycle at all -- an auto-recipe building
+        // that has yet to run one (REQ-UI-RECIPE-SUMMARY). The progress line reads
+        // "idle" whenever no cycle is actually running, whatever this says.
         double durationSeconds = 0.0;
     };
 
@@ -55,8 +67,20 @@ private:
     void refreshConfiguration() override;
     void refreshRuntime() override;
 
+    std::vector<ItemChipRow::Entry> buildInputEntries(const Building& building,
+                                                      const CycleInfo& cycle) const;
+    std::vector<ItemChipRow::Entry> buildOutputEntries(const Building& building,
+                                                       const CycleInfo& cycle) const;
+
     BuildingId m_id;
+
     RecipeSummaryRow* m_recipeSummary;
-    BufferSection*     m_buffers;
+
+    // Input buffers, production progress, output buffer -- in that order, so the card
+    // reads the way the materials flow (REQ-UI-SINGLE-SELECTION).
+    SectionBox*        m_inputSection;
+    ItemChipRow*       m_inputChips;
     ProductionSection* m_production;
+    SectionBox*        m_outputSection;
+    ItemChipRow*       m_outputChips;
 };

src/ui/selection/CMakeLists.txt

@@ -15,7 +15,6 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemChip.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemChipRow.h
     ${CMAKE_CURRENT_SOURCE_DIR}/RecipeSummaryRow.h
-    ${CMAKE_CURRENT_SOURCE_DIR}/BufferSection.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ProductionSection.h
     ${CMAKE_CURRENT_SOURCE_DIR}/RecipeSelectionControl.h
     ${CMAKE_CURRENT_SOURCE_DIR}/ClearBeltControl.h
@@ -51,7 +50,6 @@ SET(SRCS
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemChip.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemChipRow.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/RecipeSummaryRow.cpp
-    ${CMAKE_CURRENT_SOURCE_DIR}/BufferSection.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ProductionSection.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/RecipeSelectionControl.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/ClearBeltControl.cpp

src/ui/selection/HqContent.cpp

@@ -20,14 +20,15 @@ HqContent::HqContent(const SelectionContext& context, const SelectionRequest& re
     // (REQ-BLD-DECONSTRUCT), so it is never a construction site.
     : SelectionContent(context, std::nullopt, parent)
 {
+    m_hpBar = new BarRow(tr("HP"), this);
+
     m_stockSection = new SectionBox(tr("Building blocks"), this);
     m_stockChips   = new ItemChipRow(context.itemIcons, m_stockSection);
     m_stockSection->getContentLayout()->addWidget(m_stockChips);
 
-    m_hpBar = new BarRow(tr("HP"), this);
-
-    getRuntimeLayout()->addWidget(m_stockSection);
+    // HP first, as on every card that has it (REQ-UI-SELECTION-CARD, REQ-UI-HQ-PANEL).
     getRuntimeLayout()->addWidget(m_hpBar);
+    getRuntimeLayout()->addWidget(m_stockSection);
 
     setBuildingIdentity(BuildingType::Hq, getBuildingTypeName(BuildingType::Hq));
 }

src/ui/selection/ItemChipRow.cpp

@@ -73,6 +73,11 @@ void ItemChipRow::rebuildChips(const std::vector<Entry>& entries)
         ItemChip* chip = new ItemChip(icon, this);
         m_layout->addWidget(chip, static_cast<int>(index) / kChipsPerRow,
                             static_cast<int>(index) % kChipsPerRow);
+        // Shown right away, because the panel measures itself as soon as this returns. A
+        // widget created under an already-visible parent starts hidden, and a layout
+        // treats a hidden item as empty, so an unshown chip would add nothing to the
+        // size hint and the panel would be fitted to a buffer section that looks empty.
+        chip->show();
         m_chips.push_back(chip);
     }
 }

src/ui/selection/RecipeSummaryRow.cpp

@@ -13,6 +13,18 @@ namespace
 // Size the item icons are drawn at on the summary line, in device-independent pixels.
 const int kSummaryIconSizePx = 14;
 
+// Adds a freshly built label to the summary and shows it.
+//
+// The show is what makes it count: a widget created under an already-visible parent
+// starts hidden, and a layout treats a hidden item as empty, so an unshown label would
+// add nothing to the size hint the panel measures itself against as soon as this
+// returns.
+void addAndShow(QHBoxLayout* layout, QLabel* label)
+{
+    layout->addWidget(label);
+    label->show();
+}
+
 }  // namespace
 
 
@@ -71,14 +83,14 @@ void RecipeSummaryRow::rebuild(const std::vector<Amount>& inputs,
     if (!inputs.empty())
     {
         const QChar rightArrow(0x2192);  // U+2192 RIGHTWARDS ARROW
-        m_layout->addWidget(new QLabel(QString(rightArrow), this));
+        addAndShow(m_layout, new QLabel(QString(rightArrow), this));
     }
     addAmounts(outputs);
 
     if (durationSeconds > 0.0)
     {
         const QChar middleDot(0x00B7);  // U+00B7 MIDDLE DOT
-        m_layout->addWidget(new QLabel(
+        addAndShow(m_layout, new QLabel(
             QStringLiteral("%1 %2").arg(middleDot).arg(
                 tr("%1 s").arg(durationSeconds, 0, 'f', 1)), this));
     }
@@ -96,13 +108,13 @@ void RecipeSummaryRow::addAmounts(const std::vector<Amount>& amounts)
             QLabel* iconLabel = new QLabel(this);
             iconLabel->setPixmap(
                 m_itemIcons->getPixmap(entry.itemId, kSummaryIconSizePx));
-            m_layout->addWidget(iconLabel);
+            addAndShow(m_layout, iconLabel);
         }
         else
         {
-            m_layout->addWidget(
+            addAndShow(m_layout,
                        new QLabel(QString::fromStdString(entry.itemId), this));
         }
-        m_layout->addWidget(new QLabel(QString::number(entry.amount), this));
+        addAndShow(m_layout, new QLabel(QString::number(entry.amount), this));
     }
 }

src/ui/selection/SelectionContent.cpp

@@ -32,6 +32,38 @@ const int kSymbolSizePx = 20;
 const int kCardSpacingPx   = 6;
 const int kHeaderSpacingPx = 6;
 
+// The Salvage Bay has no recipe and no cycle: its two states say whether it is holding
+// scrap, not whether it is producing (REQ-BLD-SALVAGE-BAY, REQ-UI-SELECTION-STATUS).
+QString getStatusCaption(ProductionStatus status, bool isSalvageBay)
+{
+    switch (status)
+    {
+        case ProductionStatus::Unconfigured: return QObject::tr("no recipe");
+        case ProductionStatus::Producing:
+            return isSalvageBay ? QObject::tr("holding scrap")
+                                : QObject::tr("producing");
+        case ProductionStatus::Starved:
+            return isSalvageBay ? QObject::tr("empty") : QObject::tr("missing input");
+        case ProductionStatus::Blocked:      return QObject::tr("output full");
+    }
+    return QString();
+}
+
+// Every caption the status slot can end up showing for this building, so the header can
+// keep its width as the state changes rather than the panel jumping with it.
+QStringList getAllStatusCaptions(bool isSalvageBay)
+{
+    QStringList captions;
+    for (ProductionStatus status : { ProductionStatus::Unconfigured,
+                                     ProductionStatus::Producing,
+                                     ProductionStatus::Starved,
+                                     ProductionStatus::Blocked })
+    {
+        captions << getStatusCaption(status, isSalvageBay);
+    }
+    return captions;
+}
+
 }  // namespace
 
 
@@ -96,7 +128,10 @@ SelectionContent::SelectionContent(const SelectionContext& context,
         m_constructionSection->getContentLayout()->addWidget(m_constructionBar);
         m_constructionSection->getContentLayout()->addWidget(
             new EmptyNote(tr("No buffers until built"), m_constructionSection));
-        cardLayout->addWidget(m_constructionSection);
+        // Directly below the header rather than where the runtime group sits, so how far
+        // along the site is reads before what it is configured to become
+        // (REQ-UI-SELECTION-CARD).
+        cardLayout->insertWidget(1, m_constructionSection);
 
         setSlot(QColor(), tr("constructing"));
     }
@@ -165,25 +200,26 @@ void SelectionContent::setProductionStatusSlot(const Building& building)
         return;
     }
 
-    const StatusLightVisuals& colors = m_context.visuals->statusLight;
-    // The Salvage Bay has no recipe and no cycle: its two states say whether it is
-    // holding scrap, not whether it is producing (REQ-BLD-SALVAGE-BAY).
     const bool isSalvageBay = (building.type == BuildingType::SalvageBay);
+    // Room for every caption this building can show, so the panel keeps its width as the
+    // building's state changes rather than jumping with it.
+    reserveSlotFor(getAllStatusCaptions(isSalvageBay));
+
+    const StatusLightVisuals& colors = m_context.visuals->statusLight;
+    QColor dotColor;
     switch (*status)
     {
-        case ProductionStatus::Unconfigured:
-            setSlot(colors.grey, tr("no recipe"));
-            break;
-        case ProductionStatus::Producing:
-            setSlot(colors.green, isSalvageBay ? tr("holding scrap") : tr("producing"));
-            break;
-        case ProductionStatus::Starved:
-            setSlot(colors.red, isSalvageBay ? tr("empty") : tr("missing input"));
-            break;
-        case ProductionStatus::Blocked:
-            setSlot(colors.yellow, tr("output full"));
-            break;
+        case ProductionStatus::Unconfigured: dotColor = colors.grey;   break;
+        case ProductionStatus::Producing:    dotColor = colors.green;  break;
+        case ProductionStatus::Starved:      dotColor = colors.red;    break;
+        case ProductionStatus::Blocked:      dotColor = colors.yellow; break;
     }
+    setSlot(dotColor, getStatusCaption(*status, isSalvageBay));
+}
+
+void SelectionContent::reserveSlotFor(const QStringList& captions)
+{
+    m_statusPill->reserveFor(captions);
 }
 
 void SelectionContent::refreshConstruction()

src/ui/selection/SelectionContent.h

@@ -5,6 +5,7 @@
 #include <QColor>
 #include <QPixmap>
 #include <QString>
+#include <QStringList>
 #include <QWidget>
 
 #include "BuildingId.h"
@@ -79,6 +80,11 @@ protected:
     void setCountSlot(int count);
     void clearSlot();
 
+    // Reserves header room for the widest caption the slot will ever show. The panel is
+    // sized to its card (REQ-UI-SELECTION-PANEL), so without this it changes width every
+    // time the caption does -- and a card whose chips wrap changes height with it.
+    void reserveSlotFor(const QStringList& captions);
+
     // Fills the right slot from the building's production status, mapped to the same
     // colors and states the world's status light uses (REQ-UI-SELECTION-STATUS). Leaves
     // the slot empty for a type that has no status light.

src/ui/selection/SelectionNames.cpp

@@ -33,3 +33,16 @@ QString getBehaviorLabel(BehaviorKind kind)
     }
     return QString();
 }
+
+QStringList getAllBehaviorLabels()
+{
+    QStringList labels;
+    for (BehaviorKind kind : { BehaviorKind::Retreat, BehaviorKind::Attack,
+                               BehaviorKind::SalvageScrap, BehaviorKind::Repair,
+                               BehaviorKind::Rally, BehaviorKind::Standby,
+                               BehaviorKind::Advance })
+    {
+        labels << getBehaviorLabel(kind);
+    }
+    return labels;
+}

src/ui/selection/SelectionNames.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <QString>
+#include <QStringList>
 
 #include "BehaviorKind.h"
 #include "BuildingType.h"
@@ -13,3 +14,8 @@ QString getBuildingTypeName(BuildingType type);
 // Name of the behavior currently governing a ship, for the ship card's header slot
 // (REQ-UI-SHIP-BEHAVIOR). Empty when no behavior has won yet, which shows no slot.
 QString getBehaviorLabel(BehaviorKind kind);
+
+// Every name getBehaviorLabel can return. A ship's behavior changes as it fights, so the
+// header reserves room for the widest of these rather than letting the panel change
+// width each time (REQ-UI-SELECTION-PANEL).
+QStringList getAllBehaviorLabels();

src/ui/selection/ShipContent.cpp

@@ -21,6 +21,10 @@ ShipContent::ShipContent(const SelectionContext& context,
     m_statsPanel = new ShipStatsPanel(context.config, this);
     getRuntimeLayout()->addWidget(m_statsPanel);
 
+    // A ship's behavior changes as it fights, so the header holds room for the longest
+    // name rather than the panel resizing under the player each time it does.
+    reserveSlotFor(getAllBehaviorLabels());
+
     EntityAdmin& admin = context.sim->getAdmin();
     if (admin.isValid(m_entity) && admin.hasAll<ShipIdentityComponent>(m_entity))
     {

src/ui/selection/StatusPill.cpp

@@ -1,5 +1,6 @@
 #include "StatusPill.h"
 
+#include <QFontMetrics>
 #include <QGuiApplication>
 #include <QHBoxLayout>
 #include <QLabel>
@@ -49,6 +50,23 @@ StatusPill::StatusPill(QWidget* parent)
     hide();
 }
 
+void StatusPill::reserveFor(const QStringList& captions)
+{
+    if (captions == m_reservedFor)
+    {
+        return;
+    }
+    m_reservedFor = captions;
+
+    const QFontMetrics metrics(m_captionLabel->font());
+    int widestPx = 0;
+    for (const QString& caption : captions)
+    {
+        widestPx = qMax(widestPx, metrics.horizontalAdvance(caption));
+    }
+    m_captionLabel->setMinimumWidth(widestPx);
+}
+
 void StatusPill::setStatus(const QColor& dotColor, const QColor& outlineColor,
                            const QString& caption)
 {

src/ui/selection/StatusPill.h

@@ -2,6 +2,7 @@
 
 #include <QColor>
 #include <QString>
+#include <QStringList>
 #include <QWidget>
 
 class QLabel;
@@ -23,7 +24,16 @@ public:
     void setStatus(const QColor& dotColor, const QColor& outlineColor,
                    const QString& caption);
 
+    // Reserves room for the widest of the captions this pill can show, so the header --
+    // and with it the panel, which is sized to its content (REQ-UI-SELECTION-PANEL) --
+    // keeps its width as the caption changes. Without it the whole panel jumps every
+    // time a building's status does, and a card whose chips wrap changes height with it.
+    void reserveFor(const QStringList& captions);
+
 private:
     QLabel* m_dotLabel;
     QLabel* m_captionLabel;
+    // What the width is currently reserved for, so re-reserving the same set on every
+    // refresh costs nothing.
+    QStringList m_reservedFor;
 };