Posted on 2001-07-19
Last Modified: 2013-12-03
Hi I wan't to make a function that is called when a mouse leaves a window, how is that done. I tryed to look at WM_MOUSELEAVE, how can I do it otherwise ?
Question by:win32
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Expert Comment

ID: 6297472
TrackMouseEvent & WM_MOUSELEAVE works fine but only on Win98 or later.

Alternatives are to:
a) use SetCapture()
   NOTE this has side effects for keyboard accelerators, see the remarks for SetCapture in the documentation.
b) periodically poll the cursor position with GetcursorPos()
c) use SetWindowsHookEx(WH_MOUSE) in a dll and intercept all mouse movements and implement your own versions of TrackMouseEvent & WM_MOUSELEAVE.

Which method you choose depends on your circumstances.
Ask if you need more info.

LVL 42

Accepted Solution

sedgwick earned 100 total points
ID: 6297498
u can use TrackMouseEvent for that:

add this class to the app file:
class CTrackMouseEvent : public tagTRACKMOUSEEVENT
     CTrackMouseEvent(CWnd* pWnd, DWORD dwFlags = TME_LEAVE, DWORD dwHoverTime = HOVER_DEFAULT)

          this->cbSize = sizeof(TRACKMOUSEEVENT);
          this->dwFlags = dwFlags;
          this->hwndTrack = pWnd->m_hWnd;
          this->dwHoverTime = dwHoverTime;

     BOOL Track()
          { return _TrackMouseEvent(this); }

void CMyView::OnMouseMove(UINT nFlags, CPoint point)
             TRACKMOUSEEVENT tme;
          tme.cbSize = sizeof(TRACKMOUSEEVENT);
          tme.dwFlags = TME_LEAVE;
          tme.hwndTrack = m_hWnd;
CView::OnMouseMove(nFlags, point);

in the message map add this line:

LRESULT CMyView::OnMouseLeave(WPARAM wParam, LPARAM lParam)

//do your code here....
    return TRUE;


Author Comment

ID: 6297680
Ok then, thanks..

1. I hold the mousecurser over my window
2. I popup another application ex. MS Paint, over my window. it cuvers my window, and my window can't be seen at all
3. I move the Mouse Curser away from the window, place it in the DownLeft corner of Win2000
4. I press ALT F4 to close paint

Now some Graph erros in my program occures because I use MouseMove to paint some graphics. Anyway so when the mouse leaves from my window the Graphics shall be ReDrawn()

Now that's why I need the MOUSELEAVE, but is this message send, when I move the mouse away in the way I just discribed ?

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Expert Comment

ID: 6297727
   "Now some Graph erros in my program occures"
...could you elaborate on that?

Anyway the best solution really depends upon exactly what you are doing in your mousemove code.
LVL 42

Expert Comment

ID: 6297933
if u wanna redraw your window after leaving the window use Invalidate();

or if u save the last position of the mouse u can use InvalidateRect()

Author Comment

ID: 6298417
sedqwick >> Where should i call the Invalidate function ?, and if I want can i catch it ?
LVL 42

Expert Comment

ID: 6298512
in OnMouseLeave(), if u wanna invalidate the window that u just left.

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