share BuildingSystem's free functions instead of copying them

Four of the five file-local helpers in BuildingSystem.cpp had duplicates
elsewhere: isAutoRecipeBuildingType and isBeltSubsystemType were re-spelled as
isAutoRecipeBuilding and isBeltLike in SelectedBuildingPanel.cpp, and
outputBodyTile was copied verbatim as portBodyTile in GameWorldView.cpp. Same
predicates, different names, so a change to one would silently not reach the
others.

The two BuildingType predicates move to BuildingType.h, which already hosts the
free functions over that enum and is already included by both lib and ui. The
port geometry moves to a new PortGeometry.h; inputBodyTile has no duplicate but
is outputBodyTile's counterpart and belongs beside it — the sim moves items
across the port edge and the renderer draws the virtual belt there, so the two
must agree on which tile a port owns.

inputLaneEntryFree stays file-local: single use, and tied to BeltItemSlot rather
than to building types or port geometry.

Verified the six moved bodies are character-identical to their originals.

Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YHcUerKAZKWNvSKJxYKbnG

src/lib/core/BuildingType.cpp

@@ -38,3 +38,17 @@ std::string buildingTypeId(BuildingType type)
     }
     return "";
 }
+
+bool isAutoRecipeBuildingType(BuildingType type)
+{
+    return type == BuildingType::Smelter
+        || type == BuildingType::ReprocessingPlant;
+}
+
+bool isBeltSubsystemType(BuildingType type)
+{
+    return type == BuildingType::Belt
+        || type == BuildingType::Splitter
+        || type == BuildingType::TunnelEntry
+        || type == BuildingType::TunnelExit;
+}

src/lib/core/BuildingType.h

@@ -29,3 +29,13 @@ std::optional<BuildingType> parseBuildingType(const std::string& id);
 
 // Canonical id string for a BuildingType. The inverse of parseBuildingType.
 std::string buildingTypeId(BuildingType type);
+
+// Smelter and Reprocessing Plant have no player-selected recipe
+// (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING). They auto-process whatever inputs
+// they receive, matching against every recipe of their building type.
+bool isAutoRecipeBuildingType(BuildingType type);
+
+// Belts, splitters, and tunnel ends keep their runtime data in the belt subsystem
+// rather than in the Building instance, so placing/removing them must register or
+// unregister a tile with BeltSystem.
+bool isBeltSubsystemType(BuildingType type);

src/lib/core/CMakeLists.txt

@@ -9,6 +9,7 @@ SET(HDRS
     ${CMAKE_CURRENT_SOURCE_DIR}/ItemType.h
     ${CMAKE_CURRENT_SOURCE_DIR}/Item.h
     ${CMAKE_CURRENT_SOURCE_DIR}/Port.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/PortGeometry.h
     ${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoiceOption.h
     ${CMAKE_CURRENT_SOURCE_DIR}/DisplayName.h
     ${CMAKE_CURRENT_SOURCE_DIR}/BeltDragPath.h

src/lib/core/PortGeometry.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <QPoint>
+
+#include "Rotation.h"
+
+// Geometry of a building's input/output ports. A Port names the tile *outside* the
+// building together with the direction items flow across it; these helpers give the
+// building body tile on the other side of that edge, which is where the virtual
+// input/output belt lives.
+//
+// Shared by the simulation (which moves items across the edge) and the renderer
+// (which draws the virtual belt), so the two cannot disagree about which tile a
+// port belongs to.
+
+// The building body tile that owns an output port, given the port's outside tile
+// (port.tile) and its facing direction. The virtual output belt occupies this tile
+// and flows toward port.tile (REQ-MAT-OUTPUT-EMERGE).
+inline QPoint outputBodyTile(QPoint portTile, Rotation direction)
+{
+    switch (direction)
+    {
+        case Rotation::East:  return portTile + QPoint(-1,  0);
+        case Rotation::West:  return portTile + QPoint( 1,  0);
+        case Rotation::North: return portTile + QPoint( 0,  1);
+        case Rotation::South: return portTile + QPoint( 0, -1);
+    }
+    return portTile;
+}
+
+// The building body tile an input port feeds into, given the port's outside belt
+// tile (port.tile) and its inward flow direction. The virtual input belt occupies
+// this tile and flows from the outer edge (progress 0.0) to the centre (0.5)
+// (REQ-MAT-INPUT-INTAKE).
+inline QPoint inputBodyTile(QPoint portTile, Rotation inwardDirection)
+{
+    switch (inwardDirection)
+    {
+        case Rotation::East:  return portTile + QPoint( 1,  0);
+        case Rotation::West:  return portTile + QPoint(-1,  0);
+        case Rotation::North: return portTile + QPoint( 0, -1);
+        case Rotation::South: return portTile + QPoint( 0,  1);
+    }
+    return portTile;
+}

src/lib/sim/BuildingSystem.cpp

@@ -6,63 +6,13 @@
 #include <random>
 #include <set>
 
+#include "PortGeometry.h"
 #include "StateChecksum.h"
 #include "SurfaceMask.h"
 #include "tracing.h"
 
 namespace
 {
-// Smelter and Reprocessing Plant have no player-selected recipe
-// (REQ-BLD-SMELTER, REQ-BLD-REPROCESSING). They auto-process whatever inputs
-// they receive, matching against every recipe of their building type.
-bool isAutoRecipeBuildingType(BuildingType type)
-{
-    return type == BuildingType::Smelter
-        || type == BuildingType::ReprocessingPlant;
-}
-
-// Belts, splitters, and tunnel ends keep their runtime data in the belt subsystem
-// rather than in the Building instance, so placing/removing them must register or
-// unregister a tile with BeltSystem.
-bool isBeltSubsystemType(BuildingType type)
-{
-    return type == BuildingType::Belt
-        || type == BuildingType::Splitter
-        || type == BuildingType::TunnelEntry
-        || type == BuildingType::TunnelExit;
-}
-
-// The building body tile that owns an output port, given the port's outside tile
-// (port.tile) and its facing direction. The virtual output belt occupies this tile
-// and flows toward port.tile (REQ-MAT-OUTPUT-EMERGE).
-QPoint outputBodyTile(QPoint portTile, Rotation direction)
-{
-    switch (direction)
-    {
-        case Rotation::East:  return portTile + QPoint(-1,  0);
-        case Rotation::West:  return portTile + QPoint( 1,  0);
-        case Rotation::North: return portTile + QPoint( 0,  1);
-        case Rotation::South: return portTile + QPoint( 0, -1);
-    }
-    return portTile;
-}
-
-// The building body tile an input port feeds into, given the port's outside belt
-// tile (port.tile) and its inward flow direction. The virtual input belt occupies
-// this tile and flows from the outer edge (progress 0.0) to the centre (0.5)
-// (REQ-MAT-INPUT-INTAKE).
-QPoint inputBodyTile(QPoint portTile, Rotation inwardDirection)
-{
-    switch (inwardDirection)
-    {
-        case Rotation::East:  return portTile + QPoint( 1,  0);
-        case Rotation::West:  return portTile + QPoint(-1,  0);
-        case Rotation::North: return portTile + QPoint( 0, -1);
-        case Rotation::South: return portTile + QPoint( 0,  1);
-    }
-    return portTile;
-}
-
 // An input belt accepts a new item at progress 0.0 only when it holds fewer than
 // three items and the entry slot is clear (nothing within a quarter tile of 0.0),
 // matching the belt packing used elsewhere (REQ-GW-BELT-CAPACITY).