Avoiding Trouble with Mouse Capture

Figure 2: Using WM_CANCELMODE to avoid problems

   case WM_LBUTTONDOWN:
        SetCapture(hwnd);
        bDragging = TRUE;
        // perform initializations (e.g. allocate memory)
        return(0);
   case WM_MOUSEMOVE:
        if (bDragging)
           DoDragStuff();
        return(0);
   case WM_LBUTTONUP:
        if (bDragging) {
           ReleaseCapture();
           bDragging = FALSE;
           // complete the drag operation
           // clean up (e.g. free memory)
        }
        return(0);
   case WM_CANCELMODE:
        if (bDragging) {
           bDragging = FALSE;
           // cancel the drag operation
           // clean up (e.g. free memory)
        }
        return(DefWindowProc(hwnd, uMsg, wParam, lParam));