How To Detect When the Cursor Leaves the Window (183107)

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Sample Code

   #if(_WIN32_WINNT < 0x0400)
   #define WM_MOUSELEAVE   WM_USER+2
   #define TME_LEAVE               1

   typedef struct tagTRACKMOUSEEVENT {
       DWORD cbSize;
       DWORD dwFlags;
       HWND  hwndTrack;
   } TRACKMOUSEEVENT, *LPTRACKMOUSEEVENT;

   VOID CALLBACK
   TrackMouseTimerProc(HWND hWnd,UINT uMsg,UINT idEvent,DWORD dwTime) {
      RECT rect;
      POINT pt;

      GetClientRect(hWnd,&rect);
      MapWindowPoints(hWnd,NULL,(LPPOINT)&rect,2);
      GetCursorPos(&pt);
      if (!PtInRect(&rect,pt) || (WindowFromPoint(pt) != hWnd)) {
         if (!KillTimer(hWnd,idEvent)) {
            // Error killing the timer!
         }

         PostMessage(hWnd,WM_MOUSELEAVE,0,0);
      }
   }

   BOOL
   TrackMouseEvent(LPTRACKMOUSEEVENT ptme) {
      OutputDebugString(TEXT("TrackMouseEvent\n"));

      if (!ptme || ptme->cbSize < sizeof(TRACKMOUSEEVENT)) {
         OutputDebugString(TEXT("TrackMouseEvent: invalid "
                                "TRACKMOUSEEVENT structure\n"));
         return FALSE;
      }

      if (!IsWindow(ptme->hwndTrack)) {
         OutputDebugString(
            TEXT("TrackMouseEvent: invalid hwndTrack\n"));
         return FALSE;
      }

      if (!(ptme->dwFlags & TME_LEAVE)) {
         OutputDebugString(TEXT("TrackMouseEvent: invalid dwFlags\n"));
         return FALSE;
      }

      return SetTimer(ptme->hwndTrack, ptme->dwFlags,
                      100,(TIMERPROC)TrackMouseTimerProc);
   }
   #endif

   LRESULT CALLBACK
   MainWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
      TRACKMOUSEEVENT tme;
      static BOOL fInWindow;
      static BOOL fInMenu;
      switch (uMsg) {
         case WM_CREATE:
            fInWindow = FALSE;
            fInMenu = FALSE;
            return 0;

         case WM_MOUSEMOVE:
            if (!fInWindow) {
               fInWindow = TRUE;
               tme.cbSize = sizeof(TRACKMOUSEEVENT);
               tme.dwFlags = TME_LEAVE;
               tme.hwndTrack = hWnd;
               if (!TrackMouseEvent(&tme)) {
                  MessageBox(hWnd,
                             TEXT("TrackMouseEvent Failed"),
                             TEXT("Mouse Leave"),MB_OK);
               }
            }
         break;

         case WM_MOUSELEAVE:
            fInWindow = FALSE;
            if (!fInMenu)
               MessageBox(hWnd,TEXT("Elvis has left the building"),
                          TEXT("Mouse Leave"),MB_OK);
            break;
         case WM_ENTERMENULOOP:
            fInMenu = TRUE;
            break;

         case WM_EXITMENULOOP:
            fInMenu = FALSE;
            break;

         default:
            return DefWindowProc(hWnd,uMsg,wParam,lParam);
      }
      return FALSE;
   }