Q148495: PRB: Tool Tips Stop Showing After WM_xBUTTONDOWN

Article: Q148495
Product(s): Microsoft C Compiler
Version(s): winnt:2.1,2.2,4.0,4.1
Operating System(s): 
Keyword(s): kbcode kbMFC kbToolTip KbUIDesign kbVC210 kbVC220 kbVC400 kbVC410 kbGrpDSMFCATL
Last Modified: 06-MAY-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), included with:
   - Microsoft Visual C++, 32-bit Editions, versions 2.1, 2.2, 4.0, 4.1 
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SYMPTOMS
========

If you hold a mouse button down while the pointer is over a tool and then move
the mouse off of the window that contains the tool before releasing the mouse
button, then tool tips will no longer be displayed for that tool until you click
it again.

CAUSE
=====

By design, the Tooltip control won't display tool tips while a mouse button is
down. This is correct behavior. However, the Tooltip control needs to see the
WM_xBUTTONUP message to know that the mouse button has been released and it is
okay to show tool tips again.

If the WM_xBUTTONDOWN message is sent to a Tooltip control and the corresponding
WM_xBUTTONUP message is not (as in the scenario outlined above), then the
Tooltip control will behave as if the mouse button is still down, so it will not
show any further tool tips.

NOTE: This won't be a problem if the window with the Tooltip control captures the
mouse using SetCapture() when it gets WM_xBUTTONDOWN and then releases it when
it gets WM_xBUTTONUP using ReleaseCapture().

RESOLUTION
==========

As previously explained, this behavior occurs because the WM_xBUTTONUP message
is not being relayed to the Tooltip control.

To work around this behavior, relay a fabricated WM_xBUTTONUP message when it is
known that a WM_xBUTTONDOWN message has been received but that a corresponding
WM_xBUTTONUP message was not received even though the button is no longer
pressed.

This case can be determined by examining the wParam that is sent in the
WM_MOUSEMOVE message. Tooltip messages are normally relayed from the owner
window's PreTranslateMessage() function, so the workaround can be implemented in
the PreTranslateMessage() function.

NOTE: You still won't see the tip when you first move the mouse pointer back over
the tool. This is expected behavior because it is the same behavior you get if
you move the mouse over a tool and single click on that tool; that is, no more
tool tips will appear until you move the mouse pointer off the tool and then
back onto the tool.

Sample Code
-----------

  // Add members to the class definition:

      class CMyWnd : public CSomeWnd
      {
          ...

      protected:
          BOOL m_bButtonDown;
          virtual BOOL PreTranslateMessage(MSG *pMsg);

          ...
      };

  // Initialize the m_bButtonDown to FALSE in the constructor:

  CMyWnd::CMyWnd()
  {
      m_bButtonDown=FALSE;

      ...
  }

  // Implement the PreTranslateMessage() function:

  BOOL CMyWnd::PreTranslateMessage(MSG *pMsg)
  {
    static MSG msgLButtonUp = { NULL,WM_LBUTTONUP,0,0,0,0 };

    switch(pMsg->message)
    {
      case WM_LBUTTONDOWN:
      case WM_RBUTTONDOWN:
      case WM_MBUTTONDOWN:
        m_bButtonDown=TRUE;
        m_ToolTip.RelayEvent(pMsg);
        break;

      case WM_LBUTTONUP:
      case WM_MBUTTONUP:
      case WM_RBUTTONUP:
        m_bButtonDown=FALSE;
        m_ToolTip.RelayEvent(pMsg);
        break;

      case WM_MOUSEMOVE:
        if( m_bButtonDown &&
          !(pMsg->wParam & MK_LBUTTON) &&
          !(pMsg->wParam & MK_MBUTTON) &&
          !(pMsg->wParam & MK_RBUTTON) )
        {
          m_ToolTip.RelayEvent(&msgLButtonUp);
          m_bButtonDown=FALSE;
        }
        m_ToolTip.RelayEvent(pMsg);
        break;
    }

    // Rest of PreTranslateMessage goes here
    return CWnd::PreTranslateMessage(pMsg);
  }

STATUS
======

This behavior is by design.

Additional query words: 2.10 2.20 3.10 3.20 4.00 4.10 CToolTipCtrl TTM_RELAYEVENT

======================================================================
Keywords          : kbcode kbMFC kbToolTip KbUIDesign kbVC210 kbVC220 kbVC400 kbVC410 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.1,2.2,4.0,4.1
Issue type        : kbprb

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