implement copy building settings with shift + click gesture

src/ui/GameWorldView.cpp

@@ -1617,6 +1617,8 @@ void GameWorldView::keyReleaseEvent(QKeyEvent* event)
     }
     if (event->key() == Qt::Key_A) { m_scrollLeft  = false; }
     if (event->key() == Qt::Key_D) { m_scrollRight = false; }
+    // Releasing Shift discards the copied building settings (REQ-BLD-COPY-CONFIG).
+    if (event->key() == Qt::Key_Shift) { m_copiedConfig.reset(); }
     QOpenGLWidget::keyReleaseEvent(event);
 }
 
@@ -1629,6 +1631,15 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
             if (m_builderType.has_value())        { exitBuilderMode(); }
             else if (m_blueprintMode.has_value()) { exitBlueprintMode(); }
             else if (m_demolishMode)              { toggleDemolishMode(); }
+            else if (event->modifiers() & Qt::ShiftModifier)
+            {
+                // Shift + right-click copies a building's settings, but only in the
+                // default selection mode (REQ-BLD-COPY-CONFIG).
+                const QPoint tile = widgetToTile(event->pos());
+                BuildingId id = buildingAtTile(tile);
+                if (id == kInvalidBuildingId) { id = siteAtTile(tile); }
+                if (id != kInvalidBuildingId) { copyConfigFrom(id); }
+            }
         }
         return;
     }
@@ -1663,6 +1674,20 @@ void GameWorldView::mousePressEvent(QMouseEvent* event)
     }
     else
     {
+        // Shift + left-click applies the copied settings to a same-type building
+        // (REQ-BLD-COPY-CONFIG). Consumes the click so it does not change the
+        // selection. Only active in the default selection mode.
+        if ((event->modifiers() & Qt::ShiftModifier) && m_copiedConfig.has_value())
+        {
+            BuildingId id = buildingAtTile(tile);
+            if (id == kInvalidBuildingId) { id = siteAtTile(tile); }
+            if (id != kInvalidBuildingId)
+            {
+                pasteConfigTo(id);
+                return;
+            }
+        }
+
         const QVector2D worldPos = widgetToWorld(event->pos());
         const entt::entity hitEntity = entityAtWorldPos(m_sim->admin(), worldPos);
 
@@ -1868,6 +1893,81 @@ void GameWorldView::rotateGhost(bool clockwise)
     }
 }
 
+void GameWorldView::copyConfigFrom(BuildingId id)
+{
+    const std::optional<BuildingConfig> config = readBuildingConfig(*m_sim, id);
+    if (!config.has_value()) { return; }
+
+    // Only cache when there is something to copy: a selected recipe / schematic
+    // (Miner, Assembler, Shipyard) or any Splitter (empty filters = accept-all).
+    // Building types with no settings (Smelter, Reprocessing Plant, Salvage Bay,
+    // belts / tunnels, HQ) leave any existing cache untouched (REQ-BLD-COPY-CONFIG).
+    if (!config->recipeId.has_value() && !config->isSplitter) { return; }
+
+    m_copiedConfig = config;
+}
+
+void GameWorldView::pasteConfigTo(BuildingId id)
+{
+    if (!m_copiedConfig.has_value()) { return; }
+
+    const std::optional<BuildingConfig> target = readBuildingConfig(*m_sim, id);
+    if (!target.has_value() || target->type != m_copiedConfig->type) { return; }
+
+    const BuildingConfig& source = *m_copiedConfig;
+
+    // The cached settings were valid on a same-type source building, so they are
+    // valid and available on the target: unlock state is global, so a selected
+    // recipe / schematic (REQ-LOCK-UI-RECIPE, REQ-LOCK-UI-SCHEMATIC) and splitter
+    // filter item types (REQ-LOCK-UI-SPLITTER) remain unlocked. Applying reuses the
+    // same configuration commands as the selected building panel, inheriting their
+    // buffer-clearing and mid-cycle-cancel semantics (REQ-MAT-INPUT-BUFFER,
+    // REQ-MAT-OUTPUT-BUFFER, REQ-BLD-SHIPYARD).
+    if (source.isSplitter)
+    {
+        // Operational splitters are configured by tile; sites by BuildingId
+        // (mirrors SelectedBuildingPanel::onSplitterFilterChanged).
+        if (const Building* building = m_sim->buildings().findBuilding(id))
+        {
+            std::shared_ptr<SetSplitterFiltersCommand> command =
+                std::make_shared<SetSplitterFiltersCommand>();
+            command->tile    = building->anchor;
+            command->filterA = source.splitterFilterA;
+            command->filterB = source.splitterFilterB;
+            enqueueCommand(command);
+        }
+        else
+        {
+            std::shared_ptr<SetSiteSplitterFiltersCommand> command =
+                std::make_shared<SetSiteSplitterFiltersCommand>();
+            command->id      = id;
+            command->filterA = source.splitterFilterA;
+            command->filterB = source.splitterFilterB;
+            enqueueCommand(command);
+        }
+        return;
+    }
+
+    if (source.recipeId.has_value())
+    {
+        std::shared_ptr<SetRecipeCommand> command = std::make_shared<SetRecipeCommand>();
+        command->id       = id;
+        command->recipeId = *source.recipeId;
+        enqueueCommand(command);
+    }
+
+    // For a shipyard the schematic (above) must be applied before its module
+    // layout, so both commands drain in order at the next tick boundary.
+    if (source.type == BuildingType::Shipyard && source.shipLayout.has_value())
+    {
+        std::shared_ptr<SetShipLayoutCommand> command =
+            std::make_shared<SetShipLayoutCommand>();
+        command->id     = id;
+        command->layout = *source.shipLayout;
+        enqueueCommand(command);
+    }
+}
+
 void GameWorldView::enterBuilderMode(BuildingType type)
 {
     m_builderType   = type;
@@ -1940,6 +2040,7 @@ void GameWorldView::resetForNewGame()
     EventManager::getInstance()->sendEventImmediately(
         std::make_shared<DemolishModeChangedEvent>(false));
     m_selectedBuildingIds.clear();
+    m_copiedConfig     = std::nullopt;
     m_boxSelecting     = false;
     m_scrollXTiles     = 0.0f;
     m_scrollLeft       = false;