Re: How to differ mouse click and drag?

"AliR \(VC++ MVP\)" <AliR@online.nospam>
Mon, 19 Mar 2007 22:26:59 GMT
truly awesomely bad. Is that a double negative?


"Joseph M. Newcomer" <> wrote in message

It is normal to see a bit of mouse movement after a click/ But this code
is truly
awesomely bad. You should not have any message loop inside the
LButtonDown handler!

On 19 Mar 2007 00:02:35 -0700, "vicky" <> wrote:

Hi All!

I am having a problem regarding mouse capture. I am capturing mouse
events in my LBUTTONDOWN Handler but i am unable to differ between
click (Mouse down and UP) and drag(Mouse down -> move -> up).
When i am expecting single click windows fires mouse move too. at
first time it runs fine but for subsequent clicks it gives me msg
"Mouse L-Button UP, After Mouse Move.".

What to do now?

Following is my code in which i am capturing mouse events on

void CMouseCaptureView::OnLButtonDown(UINT nFlags, CPoint point)

  CPoint pt;

Starting here and continuing to "end of for", DELETE ALL THIS CODE!

This code belongs in the OnMouseMove handler! And there should be no
WM_TIMER handler at

THis code is simply WRONG. The fact that you are switching the capture is
seriously bad.
The classic drag code looks like

void CMyClass::OnLButtonDown(...)

void CMyClass::OnMouseMove(...)
   if(GetCapture() != NULL)
      { /* dragging */
       ... drag logic here
      } /* dragging */

void CMyClass::OnLButtonUp(...)
   if(GetCapture() != NULL)

Whatever you do should fit the above paradigm. Nesting your own
GetMessage loop as you
have done would not make sense in raw Win32 programming, let alone in MFC.

Since you want to know if the mouse has been dragging longer than a
specific time, you can
just do a SetTimer() in the LButtonDown handler and issue notifications
when you get the
timer notification, providing you still have capture.

THis code is so remarkably convoluted I cannot even figure out what it is
trying to
accomplish. The spontaneous ReleaseCapture calls seem to indicate serious

Explain what this code is trying to accomplish. Then rewrite it so it
accomplishes it.
But the entire inner loop has to go.

  for (;;)

     MSG msg;

     CWnd *pwnd = AfxGetApp()->GetMainWnd();
     HWND hwnd = pwnd->GetSafeHwnd();


     case WM_MOUSEMOVE:
        RECT rc;
        bMove = TRUE;
        pt = msg.lParam ;
           if(hwnd != GetCapture()->GetSafeHwnd() )

     case WM_LBUTTONUP:

           bMove = FALSE;
           AfxMessageBox("Mouse L-Button UP, After Mouse Move.");
           AfxMessageBox("Mouse L-Button UP.");

     case WM_TIMER:

     }//End of switch

     // release the mouse (if we still own it)
     if (GetCapture() == this) ::ReleaseCapture();

  }//End of For

  CView::OnLButtonDown(nFlags, point);

Joseph M. Newcomer [MVP]
MVP Tips:

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