F4 latches the side panel away, and holding Space slides it away

src/rwe/LoadingScene.cpp

@@ -472,6 +472,8 @@ namespace rwe
         sounds.okToBuild = lookUpSound("OKTOBUILD");
         sounds.notOkToBuild = lookUpSound("NOTOKTOBUILD");
         sounds.selectMultipleUnits = lookUpSound("SelectMultipleUnits");
+        sounds.panel = lookUpSound("Panel");
+        sounds.options = lookUpSound("Options");
 
         auto consoleFont = sceneContext.textureService->getFont("fonts/CONSOLE.FNT");
         // The original loads exactly two in-game fonts (0x42A320): COMIX for

src/rwe/game/GameScene.cpp

@@ -342,6 +342,7 @@ namespace rwe
         }
 
         updateMusic();
+        updatePanelSlide();
 
         // Pause halts simulation tick dispatch by not advancing the
         // scaled-time accumulator. Speed scales the accumulator using
@@ -415,7 +416,7 @@ namespace rwe
                 // convert that to the world, then set the camera's position to there
                 // (clamped to map bounds)
 
-                auto minimapToWorld = minimapToWorldMatrix(simulation.terrain, minimapRect);
+                auto minimapToWorld = minimapToWorldMatrix(simulation.terrain, slidMinimapRect());
                 auto mousePos = getMousePosition();
                 auto worldPos = minimapToWorld * Vector3f(static_cast<float>(mousePos.x) + 0.5f, static_cast<float>(mousePos.y) + 0.5, 0.0f);
 

src/rwe/game/GameScene.h

@@ -298,6 +298,22 @@ namespace rwe
         bool leftShiftDown{false};
         bool rightShiftDown{false};
 
+        /**
+         * The side panel's slide, 0 with the panel in place and
+         * PanelSlideExtent with it slid off the left edge. F4 latches it
+         * away; holding Space slides it away while the key is down and the
+         * cursor is not on the panel itself. The original's updater
+         * (0x4948E0, TOTALA-EXE.md "the panel-slide updater") moves it a
+         * quarter of the remaining distance a frame and never less than a
+         * pixel, plays the Panel sound as it leaves an end and Options as it
+         * arrives at one, and 125 is the panel's width less its border.
+         * Presentation only: the world viewport grows under it.
+         */
+        static constexpr int PanelSlideExtent = 125;
+        int panelSlide{0};
+        bool panelSlideLatched{false};
+        bool spaceDown{false};
+
         struct CameraControlStateFree
         {
         };
@@ -845,6 +861,11 @@ namespace rwe
         void addBattlePoints(int points);
         void updateMusic();
 
+        /** Steps the side panel's slide one frame; see panelSlide. */
+        void updatePanelSlide();
+        /** The minimap's rectangle where it is drawn this frame, slid with the panel. */
+        Rectangle2f slidMinimapRect() const;
+
         /** What size the world render textures were made at, so a window resize remakes them. */
         std::pair<unsigned int, unsigned int> worldRenderTextureSize{0, 0};
 

src/rwe/game/GameScene_commands.cpp

@@ -106,7 +106,7 @@ namespace rwe
     bool GameScene::isCursorOverMinimap() const
     {
         auto mousePos = getMousePosition();
-        return minimapRect.contains(mousePos.x, mousePos.y);
+        return slidMinimapRect().contains(mousePos.x, mousePos.y);
     }
 
     bool GameScene::isCursorOverWorld() const

src/rwe/game/GameScene_input.cpp

@@ -113,6 +113,19 @@ namespace rwe
         {
             showDebugWindow = !showDebugWindow;
         }
+        else if (keysym.key == SDLK_F4)
+        {
+            // Toggles bit 7 of the display-options word (0x49639D), the one
+            // bit of it with no registry name: the side panel slides away
+            // and stays away until the next press. See panelSlide.
+            panelSlideLatched = !panelSlideLatched;
+        }
+        else if (keysym.key == SDLK_SPACE)
+        {
+            // Polled, not dispatched, in the original (0x494942): while it
+            // is held the panel slides away, and back when it is let go.
+            spaceDown = true;
+        }
         else if (keysym.key == SDLK_F1)
         {
             helpVisible = !helpVisible;
@@ -425,6 +438,70 @@ namespace rwe
         {
             rightShiftDown = false;
         }
+        else if (keysym.key == SDLK_SPACE)
+        {
+            spaceDown = false;
+        }
+    }
+
+    void GameScene::updatePanelSlide()
+    {
+        // 0x4948E0. With the F4 bit set the position runs to the extent;
+        // with it clear it runs to zero, unless Space is held and the cursor
+        // is not on the panel's own gadget, which runs it to the extent
+        // again. Each frame moves a quarter of what is left, never less
+        // than a pixel, so the panel starts fast and eases in.
+        auto mouse = getMousePosition();
+        auto overPanel = mouse.x >= 0 && mouse.x < GuiSizeLeft - panelSlide;
+        auto wantHidden = panelSlideLatched || (spaceDown && !overPanel);
+
+        auto before = panelSlide;
+        if (wantHidden && panelSlide < PanelSlideExtent)
+        {
+            if (panelSlide == 0 && sounds.panel)
+            {
+                playUiSound(*sounds.panel);
+            }
+            panelSlide += std::max(1, (PanelSlideExtent - panelSlide) / 4);
+            if (panelSlide >= PanelSlideExtent)
+            {
+                panelSlide = PanelSlideExtent;
+                if (sounds.options)
+                {
+                    playUiSound(*sounds.options);
+                }
+            }
+        }
+        else if (!wantHidden && panelSlide > 0)
+        {
+            if (panelSlide == PanelSlideExtent && sounds.panel)
+            {
+                playUiSound(*sounds.panel);
+            }
+            panelSlide -= std::max(1, panelSlide / 4);
+            if (panelSlide <= 0)
+            {
+                panelSlide = 0;
+                if (sounds.options)
+                {
+                    playUiSound(*sounds.options);
+                }
+            }
+        }
+
+        if (panelSlide != before && guiVisible)
+        {
+            worldViewport.setInset(GuiSizeLeft - panelSlide, GuiSizeTop, GuiSizeRight, GuiSizeBottom);
+        }
+        if (currentPanel)
+        {
+            currentPanel->setPosition(-panelSlide, currentPanel->getY());
+        }
+    }
+
+    Rectangle2f GameScene::slidMinimapRect() const
+    {
+        return Rectangle2f::fromTopLeft(minimapRect.left() - static_cast<float>(panelSlide), minimapRect.top(), minimapRect.width(), minimapRect.height());
     }
 
     void GameScene::onMouseDown(MouseButtonEvent event)

src/rwe/game/GameScene_render.cpp

@@ -528,15 +528,16 @@ namespace rwe
 
     void GameScene::renderMinimap()
     {
+        auto minimapDrawRect = slidMinimapRect();
         // draw minimap
-        chromeUiRenderService.drawSpriteAbs(minimapRect, *minimap);
+        chromeUiRenderService.drawSpriteAbs(minimapDrawRect, *minimap);
         if (fogSprite)
         {
-            chromeUiRenderService.drawSpriteAbs(minimapRect, *fogSprite);
+            chromeUiRenderService.drawSpriteAbs(minimapDrawRect, *fogSprite);
         }
 
         auto cameraInverse = computeInverseViewProjectionMatrix(worldCameraState, worldViewport.width(), worldViewport.height());
-        auto worldToMinimap = worldToMinimapMatrix(simulation.terrain, minimapRect);
+        auto worldToMinimap = worldToMinimapMatrix(simulation.terrain, minimapDrawRect);
 
         // draw minimap dots
         for (const auto& [unitId, unit] : simulation.units)
@@ -743,7 +744,7 @@ namespace rwe
                 }
 
                 chromeUiRenderService.drawLines(
-                    buildMinimapRing(Vector2f(centre.x, centre.y), radius, minimapRect, false, 0),
+                    buildMinimapRing(Vector2f(centre.x, centre.y), radius, slidMinimapRect(), false, 0),
                     color);
             }
         }
@@ -804,7 +805,7 @@ namespace rwe
             auto parity = dashed && ((sceneTime.value / minimapBlinkTicks) % 2 == 1) ? 1 : 0;
 
             chromeUiRenderService.drawLines(
-                buildMinimapRing(Vector2f(centre.x, centre.y), radius, minimapRect, dashed, parity),
+                buildMinimapRing(Vector2f(centre.x, centre.y), radius, slidMinimapRect(), dashed, parity),
                 Color(255, 255, 255));
         }
     }

src/rwe/game/InGameSoundsInfo.h

@@ -21,5 +21,8 @@ namespace rwe
         std::optional<AudioService::SoundHandle> notOkToBuild;
 
         std::optional<AudioService::SoundHandle> selectMultipleUnits;
+        /** The side panel leaving an end of its slide, and arriving at one. */
+        std::optional<AudioService::SoundHandle> panel;
+        std::optional<AudioService::SoundHandle> options;
     };
 }

src/rwe/ui/UiComponent.h

@@ -68,6 +68,13 @@ namespace rwe
         int getX() { return posX; }
         int getY() { return posY; }
 
+        /** Moves the component; a panel's children move with it, drawn and hit-tested alike. */
+        void setPosition(int x, int y)
+        {
+            posX = x;
+            posY = y;
+        }
+
         virtual void mouseDown(MouseButtonEvent /*event*/) {}
 
         virtual void mouseUp(MouseButtonEvent /*event*/) {}