float the selection panel over the game world instead of a side column

src/ui/SelectionPanel.h

@@ -0,0 +1,151 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <QPoint>
+#include <QRect>
+#include <QWidget>
+
+#include "BeltSystem.h"
+#include "Building.h"
+#include "BuildingId.h"
+#include "EntitySelectionChangedEvent.h"
+#include "EventHandler.h"
+#include "GameConfig.h"
+#include "PlayerCommandsAppliedEvent.h"
+#include "RecipesConfig.h"
+#include "DebrisSelectionChangedEvent.h"
+#include "SelectionChangedEvent.h"
+#include "ShipLayout.h"
+#include "ShipsConfig.h"
+#include "Tick.h"
+#include "TickAdvancedEvent.h"
+
+class Simulation;
+class FieldSelectionPanel;
+class ShipLayoutPreview;
+class QLabel;
+class QListWidget;
+class QPushButton;
+class QScrollArea;
+class QVBoxLayout;
+
+// Shows the current selection. The building category (buildings and construction sites)
+// is rendered by this panel itself; the field category (ships, defence stations, debris)
+// is rendered by the embedded FieldSelectionPanel.
+//
+// The two categories are mutually exclusive (REQ-UI-SELECTION-CATEGORIES) and this panel
+// is the sole arbiter of which one owns the content: it listens to all three selection
+// events, forwards the field ones to the child panel, and drops the losing category's
+// content. Neither panel touches the other's widgets.
+//
+// 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 content, anchors to the right edge of
+// the band its owner hands it, and hides itself entirely while nothing is selected
+// (REQ-UI-EMPTY-SELECTION).
+class SelectionPanel : public QWidget,
+                       public CombinedEventHandler<TickAdvancedEvent,
+                                                   PlayerCommandsAppliedEvent,
+                                                   EntitySelectionChangedEvent,
+                                                   SelectionChangedEvent,
+                                                   DebrisSelectionChangedEvent>
+{
+    Q_OBJECT
+
+public:
+    SelectionPanel(Simulation* sim, const GameConfig* config,
+                   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);
+
+private:
+    void handleEvent(std::shared_ptr<const TickAdvancedEvent> event) override;
+    void handleEvent(std::shared_ptr<const PlayerCommandsAppliedEvent> event) override;
+    void handleEvent(std::shared_ptr<const EntitySelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
+    void handleEvent(std::shared_ptr<const DebrisSelectionChangedEvent> event) override;
+
+private slots:
+    void onSelectRecipeClicked();
+    void onClearBelt();
+    void onSplitterFilterChanged();
+
+private:
+    // Why the selection display is being refreshed. A periodic tick only needs a
+    // lightweight content update (e.g. a construction site's progress label),
+    // whereas an applied player command may have changed the configuration and
+    // needs a full structural rebuild.
+    enum class RefreshReason
+    {
+        PeriodicTick,
+        CommandApplied
+    };
+
+    void onSelectionChanged(const std::vector<BuildingId>& ids);
+    // Gives the panel to the field category once it has anything selected.
+    void yieldToFieldSelection();
+    // Shows the panel while either category has a selection and hides it otherwise
+    // (REQ-UI-EMPTY-SELECTION), re-fitting it to its current content while it is shown.
+    // Every path that changes the content ends here, because the content is what sizes
+    // the panel.
+    void updateVisibility();
+    // Re-fits the panel to its content within the anchored band.
+    void refit();
+    void refreshSelectionDisplay(RefreshReason reason);
+    void rebuild();
+    void hideAllWidgets();
+    void buildEmpty();
+    void buildSingle(BuildingId id);
+    void buildMulti(const std::vector<BuildingId>& ids);
+    void refreshBuffers(const Building* b);
+    void refreshSiteProgress(const ConstructionSite* s);
+    void updateShipyardLayoutWidgets(BuildingType type,
+                                     const std::string& recipeId,
+                                     const std::optional<ShipLayoutConfig>& shipLayout);
+    void buildSplitterFilters(const std::optional<BeltSystem::SplitterInfo>& info);
+    const RecipeDef* findRecipe(const Building* b) const;
+    const ShipDef*   findShipDef(const std::string& id) const;
+    std::vector<std::string> getAllItemIds() const;
+
+    Simulation*        m_sim;
+    const GameConfig*  m_config;
+    std::vector<BuildingId> m_selectedBuildingIds;
+
+    // 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;
+
+    // Scrolls the content once it outgrows the band (REQ-UI-SELECTION-PANEL). All the
+    // content widgets below are children of m_content, not of the panel itself.
+    QScrollArea* m_scrollArea;
+    QWidget*     m_content;
+
+    QVBoxLayout* m_layout;
+    QLabel*      m_titleLabel;
+    QPushButton* m_recipeSelectButton;
+    QPushButton* m_clearBeltBtn;
+    QLabel*      m_filterALabel;
+    QListWidget* m_filterAList;
+    QLabel*      m_filterBLabel;
+    QListWidget* m_filterBList;
+    QLabel*      m_buffersLabel;
+
+    ShipLayoutPreview* m_layoutPreview;
+    QPushButton*       m_configureLayoutBtn;
+
+    std::optional<BuildingId> m_singleBuildingId;
+    bool         m_singleIsSite = false;  // selected single entity is a construction site
+    QPoint       m_splitterTile;
+    std::string  m_currentRecipeId;
+
+    // Renders the field selection (actors + debris) below the building content
+    // (REQ-UI-FIELD-MULTI-SELECTION). Hides itself while nothing field-side is selected.
+    FieldSelectionPanel* m_fieldSelectionPanel;
+};