Zoom with mouse wheel

Author: morganchristiansson

CGame_Event.cpp

@@ -11,6 +11,41 @@
 #include "callbacks.h"
 #include "globals.h"
 
+namespace {
+bool tryZoom(int deltaTH, int deltaTW, int deltaInc, CMap* mapObj)
+{
+    if(!mapObj || !mapObj->getMap())
+        return false;
+    const int newInc = TRIANGLE_INCREASE + deltaInc;
+    if(newInc < 1 || newInc > 10)
+        return false;
+
+    callback::PleaseWait(INITIALIZING_CALL);
+    TRIANGLE_HEIGHT += deltaTH;
+    TRIANGLE_WIDTH += deltaTW;
+    TRIANGLE_INCREASE += deltaInc;
+    bobMAP* myMap = mapObj->getMap();
+    myMap->updateVertexCoords();
+    CSurface::get_nodeVectors(*myMap);
+    callback::PleaseWait(WINDOW_QUIT_MESSAGE);
+    return true;
+}
+
+void resetZoom(CMap* mapObj)
+{
+    if(!mapObj || !mapObj->getMap())
+        return;
+    callback::PleaseWait(INITIALIZING_CALL);
+    TRIANGLE_HEIGHT = 28;
+    TRIANGLE_WIDTH = 56;
+    TRIANGLE_INCREASE = 5;
+    bobMAP* myMap = mapObj->getMap();
+    myMap->updateVertexCoords();
+    CSurface::get_nodeVectors(*myMap);
+    callback::PleaseWait(WINDOW_QUIT_MESSAGE);
+}
+} // namespace
+
 void CGame::EventHandling(SDL_Event* Event)
 {
     switch(Event->type)
@@ -81,45 +116,13 @@ void CGame::EventHandling(SDL_Event* Event)
 #endif
                 // F5 - F7 is ZOOM, F5 = zoom in, F6 = normal view, F7 = zoom out
                 case SDLK_F5:
-                    if(TRIANGLE_INCREASE < 10 && MapObj->getMap())
-                    {
-                        callback::PleaseWait(INITIALIZING_CALL);
-                        TRIANGLE_HEIGHT += 5;
-                        TRIANGLE_WIDTH += 11;
-                        TRIANGLE_INCREASE += 1;
-                        bobMAP* myMap = MapObj->getMap();
-                        myMap->updateVertexCoords();
-                        CSurface::get_nodeVectors(*myMap);
-                        callback::PleaseWait(WINDOW_QUIT_MESSAGE);
-                    }
+                    tryZoom(5, 11, 1, MapObj);
                     break;
                 case SDLK_F6:
-                {
-                    if(MapObj->getMap())
-                    {
-                        callback::PleaseWait(INITIALIZING_CALL);
-                        TRIANGLE_HEIGHT = 28;
-                        TRIANGLE_WIDTH = 56;
-                        TRIANGLE_INCREASE = 5;
-                        bobMAP* myMap = MapObj->getMap();
-                        myMap->updateVertexCoords();
-                        CSurface::get_nodeVectors(*myMap);
-                        callback::PleaseWait(WINDOW_QUIT_MESSAGE);
-                    }
-                }
-                break;
+                    resetZoom(MapObj);
+                    break;
                 case SDLK_F7:
-                    if(TRIANGLE_INCREASE > 1 && MapObj->getMap())
-                    {
-                        callback::PleaseWait(INITIALIZING_CALL);
-                        TRIANGLE_HEIGHT -= 5;
-                        TRIANGLE_WIDTH -= 11;
-                        TRIANGLE_INCREASE -= 1;
-                        bobMAP* myMap = MapObj->getMap();
-                        myMap->updateVertexCoords();
-                        CSurface::get_nodeVectors(*myMap);
-                        callback::PleaseWait(WINDOW_QUIT_MESSAGE);
-                    }
+                    tryZoom(-5, -11, -1, MapObj);
                     break;
 
                 default: break;
@@ -381,6 +384,43 @@ void CGame::EventHandling(SDL_Event* Event)
             break;
         }
 
+        case SDL_MOUSEWHEEL:
+        {
+            if(!MapObj)
+                break;
+
+            int y = Event->wheel.y;
+            if(Event->wheel.direction == SDL_MOUSEWHEEL_FLIPPED)
+                y = -y;
+            if(y == 0)
+                break;
+
+            const int deltaTH = (y > 0) ? 5 : -5;
+            const int deltaTW = (y > 0) ? 11 : -11;
+            const int deltaInc = (y > 0) ? 1 : -1;
+
+            // Save values before zoom for cursor-centered adjustment
+            const float oldHeight = TRIANGLE_HEIGHT;
+            const float oldWidth = TRIANGLE_WIDTH;
+            const float mouseX = Cursor.pos.x;
+            const float mouseY = Cursor.pos.y;
+
+            if(!tryZoom(deltaTH, deltaTW, deltaInc, MapObj))
+                break;
+
+            // Keep the map point under the cursor stable after zoom
+            DisplayRectangle dr = MapObj->getDisplayRect();
+            const float ratioX = TRIANGLE_WIDTH / oldWidth;
+            const float ratioY = TRIANGLE_HEIGHT / oldHeight;
+            const auto size = dr.getSize();
+            dr.left = static_cast<Sint32>((dr.left + mouseX) * ratioX - mouseX);
+            dr.top = static_cast<Sint32>((dr.top + mouseY) * ratioY - mouseY);
+            dr.right = dr.left + size.x;
+            dr.bottom = dr.top + size.y;
+            MapObj->setDisplayRect(dr);
+            break;
+        }
+
         case SDL_WINDOWEVENT:
         {
             switch(Event->window.event)