Added SDL_WINDOWEVENT_HIT_TEST.

This lets windows know when they are dropping a mouse event because their
hit test reported something other than SDL_HITTEST_NORMAL. It lets them know
exactly where in the event queue this happened.

This patch is based on work in Unreal Engine 4's fork of SDL,
compliments of Epic Games.

include/SDL_video.h

@@ -160,8 +160,8 @@ typedef enum
     SDL_WINDOWEVENT_LEAVE,          /**< Window has lost mouse focus */
     SDL_WINDOWEVENT_FOCUS_GAINED,   /**< Window has gained keyboard focus */
     SDL_WINDOWEVENT_FOCUS_LOST,     /**< Window has lost keyboard focus */
-    SDL_WINDOWEVENT_CLOSE           /**< The window manager requests that the
-                                         window be closed */
+    SDL_WINDOWEVENT_CLOSE,          /**< The window manager requests that the window be closed */
+    SDL_WINDOWEVENT_HIT_TEST        /** Window had a hit test that wasn't SDL_HITTEST_NORMAL. */
 } SDL_WindowEventID;
 
 /**

src/video/cocoa/SDL_cocoawindow.m

@@ -852,6 +852,7 @@ SetWindowStyle(SDL_Window * window, unsigned int style)
     }
 
     if ([self processHitTest:theEvent]) {
+        SDL_SendWindowEvent(_data->window, SDL_WINDOWEVENT_HIT_TEST, 0, 0);
         return;  /* dragging, drop event. */
     }
 
@@ -894,6 +895,7 @@ SetWindowStyle(SDL_Window * window, unsigned int style)
     int button;
 
     if ([self processHitTest:theEvent]) {
+        SDL_SendWindowEvent(_data->window, SDL_WINDOWEVENT_HIT_TEST, 0, 0);
         return;  /* stopped dragging, drop event. */
     }
 
@@ -937,6 +939,7 @@ SetWindowStyle(SDL_Window * window, unsigned int style)
     int x, y;
 
     if ([self processHitTest:theEvent]) {
+        SDL_SendWindowEvent(window, SDL_WINDOWEVENT_HIT_TEST, 0, 0);
         return;  /* dragging, drop event. */
     }
 

src/video/windows/SDL_windowsevents.c

@@ -928,15 +928,17 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
                     const SDL_Point point = { (int) winpoint.x, (int) winpoint.y };
                     const SDL_HitTestResult rc = window->hit_test(window, &point, window->hit_test_data);
                     switch (rc) {
-                        case SDL_HITTEST_DRAGGABLE: return HTCAPTION;
-                        case SDL_HITTEST_RESIZE_TOPLEFT: return HTTOPLEFT;
-                        case SDL_HITTEST_RESIZE_TOP: return HTTOP;
-                        case SDL_HITTEST_RESIZE_TOPRIGHT: return HTTOPRIGHT;
-                        case SDL_HITTEST_RESIZE_RIGHT: return HTRIGHT;
-                        case SDL_HITTEST_RESIZE_BOTTOMRIGHT: return HTBOTTOMRIGHT;
-                        case SDL_HITTEST_RESIZE_BOTTOM: return HTBOTTOM;
-                        case SDL_HITTEST_RESIZE_BOTTOMLEFT: return HTBOTTOMLEFT;
-                        case SDL_HITTEST_RESIZE_LEFT: return HTLEFT;
+                        #define POST_HIT_TEST(ret) { SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_HIT_TEST, 0, 0); return ret; }
+                        case SDL_HITTEST_DRAGGABLE: POST_HIT_TEST(HTCAPTION);
+                        case SDL_HITTEST_RESIZE_TOPLEFT: POST_HIT_TEST(HTTOPLEFT);
+                        case SDL_HITTEST_RESIZE_TOP: POST_HIT_TEST(HTTOP);
+                        case SDL_HITTEST_RESIZE_TOPRIGHT: POST_HIT_TEST(HTTOPRIGHT);
+                        case SDL_HITTEST_RESIZE_RIGHT: POST_HIT_TEST(HTRIGHT);
+                        case SDL_HITTEST_RESIZE_BOTTOMRIGHT: POST_HIT_TEST(HTBOTTOMRIGHT);
+                        case SDL_HITTEST_RESIZE_BOTTOM: POST_HIT_TEST(HTBOTTOM);
+                        case SDL_HITTEST_RESIZE_BOTTOMLEFT: POST_HIT_TEST(HTBOTTOMLEFT);
+                        case SDL_HITTEST_RESIZE_LEFT: POST_HIT_TEST(HTLEFT);
+                        #undef POST_HIT_TEST
                         case SDL_HITTEST_NORMAL: return HTCLIENT;
                     }
                 }

src/video/x11/SDL_x11events.c

@@ -1011,6 +1011,7 @@ X11_DispatchEvent(_THIS)
                 int button = xevent.xbutton.button;
                 if(button == Button1) {
                     if (ProcessHitTest(_this, data, &xevent)) {
+                        SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_HIT_TEST, 0, 0);
                         break;  /* don't pass this event on to app. */
                     }
                 }