add FieldSelectionPanel for extracting the ships/stations/debris selection

src/ui/SelectedBuildingPanel.h

@@ -7,12 +7,9 @@
 #include <QPoint>
 #include <QWidget>
 
-#include "entt/entity/entity.hpp"
-
 #include "BeltSystem.h"
 #include "Building.h"
 #include "BuildingId.h"
-#include "DebugDrawToggledEvent.h"
 #include "EntitySelectionChangedEvent.h"
 #include "EventHandler.h"
 #include "GameConfig.h"
@@ -26,20 +23,27 @@
 #include "TickAdvancedEvent.h"
 
 class Simulation;
+class FieldSelectionPanel;
 class ShipLayoutPreview;
-class ShipStatsPanel;
 class QLabel;
 class QListWidget;
 class QPushButton;
 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.
 class SelectedBuildingPanel : public QWidget,
                                public CombinedEventHandler<TickAdvancedEvent,
                                                            PlayerCommandsAppliedEvent,
                                                            EntitySelectionChangedEvent,
                                                            SelectionChangedEvent,
-                                                           DebrisSelectionChangedEvent,
-                                                           DebugDrawToggledEvent>
+                                                           DebrisSelectionChangedEvent>
 {
     Q_OBJECT
 
@@ -54,7 +58,6 @@ private:
     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;
-    void handleEvent(std::shared_ptr<const DebugDrawToggledEvent> event) override;
 
 private slots:
     void onSelectRecipeClicked();
@@ -73,17 +76,14 @@ private:
     };
 
     void onSelectionChanged(const std::vector<BuildingId>& ids);
+    // Gives the panel to the field category once it has anything selected.
+    void yieldToFieldSelection();
     void refreshSelectionDisplay(RefreshReason reason);
     void rebuild();
     void hideAllWidgets();
-    void clearContent();
     void buildEmpty();
     void buildSingle(BuildingId id);
     void buildMulti(const std::vector<BuildingId>& ids);
-    // Summed remaining scrap across the selected debris (REQ-UI-DEBRIS-PANEL).
-    int selectedDebrisScrapTotal() const;
-    // "Scrap x N" line for the multi-object summary (REQ-UI-FIELD-MULTI-SELECTION).
-    QString scrapTotalText() const;
     void refreshBuffers(const Building* b);
     void refreshSiteProgress(const ConstructionSite* s);
     void updateShipyardLayoutWidgets(BuildingType type,
@@ -116,28 +116,7 @@ private:
     QPoint       m_splitterTile;
     std::string  m_currentRecipeId;
 
-    bool m_debugDraw = false;
-    // The selected ships/defence stations. Shares the "field" selection category with
-    // debris (m_selectedDebris): both can be non-empty at once (REQ-UI-SELECTION-CATEGORIES).
-    std::vector<entt::entity> m_selectedEntities;
-    ShipStatsPanel* m_entityStatsPanel;
-    QLabel*         m_entityTitleLabel;
-    QLabel*         m_stationStatsLabel;
-    QLabel*         m_entitySummaryLabel;
-
-    std::vector<entt::entity> m_selectedDebris;
-    // Shows the debris "Scrap" stat row (single selection) — the scrap total for the
-    // multi-object summary lives in m_entitySummaryLabel instead.
-    QLabel*                   m_scrapLabel;
-
-    // Renders the combined field selection (actors + debris): a single-object stats panel
-    // (ship, station, or debris) or a multi-object count summary that appends the debris
-    // count and scrap total when debris is also selected (REQ-UI-FIELD-MULTI-SELECTION).
-    void buildFieldSelection();
-    void buildEntityShip(entt::entity entity);
-    void buildEntityStation(entt::entity entity);
-    void buildEntitySummary();
-    void buildDebrisSingle();
-    void refreshEntityStats();
-    void clearEntityDisplay();
+    // 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;
 };