Q133716: HOWTO: How to Detect Mouse Clicks on Client Area of MDI Frame Wi
Article: Q133716
Product(s): Microsoft C Compiler
Version(s): winnt:1.0,2.0,2.1,2.2,4.0,4.1,4.2
Operating System(s):
Keyword(s): kbcode kbMFC KbUIDesign kbVC100 kbVC200 kbGrpDSMFCATL
Last Modified: 06-MAY-2001
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 2.2, 4.0, 4.1
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2
- Microsoft Visual C++, 32-bit Professional Edition, version 4.2
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SUMMARY
=======
You can detect when a user clicks the mouse while the pointer is over the client
area of your main MDI frame window (the area of the client not covered by any
open MDI child windows). To do so, you must first subclass the MDIClient so you
can intercept the mouse messages being sent to it. This article shows by example
how to do it using MFC. You can extend the method outlined here to handle any
messages sent to the MDIClient.
MORE INFORMATION
================
To manage its MDI child windows, the CMDIFrameWnd class creates a window of the
class "mdiclient" to cover its entire client area (also referred to as the
Application Workspace). MFC stores a handle to this MDIClient window in a public
member variable, m_hWndMDIClient, of the CMDIFrameWnd class.
The MDIClient is a standard Windows window, not an MFC object. However,
subclassing it allows you to treat it just as you would any other CWnd, taking
advantage of standard MFC features like message maps. For example, you could use
this technique to provide a context menu when the user clicks the right mouse
button. Or, as the Windows 95 desktop does, you could use it to provide an easy
means of selecting a group of iconized MDI child windows, enclosing them within
a tracker rectangle as the user drags with the left mouse button button held
down.
Steps to Subclass the MDIClient
-------------------------------
Subclassing the MDIClient is actually quite easy as summarized in the following
three steps. For more detailed information about this process, please see the
following article in the Microsoft Knowledge Base:
Q129471 How to SubClass the MDIClient by Using MFC
1. Derive a class from CWnd, called CMyMDIClient for example, and add it to your
project. You can use ClassWizard to help you do this.
2. If you are creating a 16-bit application, you need to add a public function
called GetSuperWndProcAddr() to your new CMyMDIClient class. Do not do this
step when building applications with 32-bit versions of Visual C++.
WNDPROC* CMyMDIClient::GetSuperWndProcAddr()
{
static WNDPROC NEAR pfnSuper = NULL;
return &pfnSuper;
}
3. Include your class header file in MAINFRM.H. Embed a public member object of
your new class in your CMainFrame class, for example CMyMDIClient
m_MyMDIClient. If you have not already done so, override
CMDIFrameWnd::OnCreate(). In your CMainFrame::OnCreate(), first call the base
class implementation, CMDIFrameWnd::OnCreate(), which creates the MDIClient
window itself and stores the handle in m_hWndMDIClient. Then subclass that
window to your embedded member object:
int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
// Call the base class implementation to create the MDIClient
// window.
if (CMDIFrameWnd::OnCreate(lpCreateStruct) == -1)
return -1;
// Subclass the MDIClient window.
if (!m_MyMDIClient.SubclassWindow(m_hWndMDIClient))
{
TRACE ("Failed to subclass MDI client window\n");
return (-1);
}
...
}
Code Sample
-----------
Once you subclass the MDIClient in this way, you can add any needed message
handlers directly to your CMyMDIClient class. To illustrate, the following code
displays your application's File menu as a context menu when the user clicks the
MDIClient using the right mouse button.
void CMyMDIClient::OnRButtonDown(UINT nFlags, CPoint point)
{
POINT ScreenPoint = point;
CMenu* pMenuTrackPopup;
// Get a pointer to the app's File menu popup.
// AfxGetMainWnd() returns a pointer to the main frame window,
// GetMenu() returns a pointer to the main menu of the application,
// and GetSubMenu(0) retrieves the submenu at position 0 (here the
// File menu).
pMenuTrackPopup = ((AfxGetMainWnd())->GetMenu())->GetSubMenu(0);
// Convert the mouse point to screen coordinates since that is what
// TrackPopupMenu() expects.
ClientToScreen(&ScreenPoint);
// Draw and track the "floating" popup
pMenuTrackPopup->TrackPopupMenu(TPM_RIGHTBUTTON,
ScreenPoint.x, ScreenPoint.y,
AfxGetMainWnd(), // Use the 'this' pointer if you want
// commands to be handled in your
// CMyMDIClient class instead
NULL);
// NOTE: Do not destroy this menu here!
// Call the base class
CWnd::OnRButtonDown(nFlags, point);
}
Additional query words: kbinf 1.50 1.51 1.52 1.00 2.00 2.10 2.50 2.51 2.52 2.20 3.00 3.10 4.00 4.10 4.20
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Keywords : kbcode kbMFC KbUIDesign kbVC100 kbVC200 kbGrpDSMFCATL
Technology : kbAudDeveloper kbMFC
Version : winnt:1.0,2.0,2.1,2.2,4.0,4.1,4.2
Issue type : kbhowto
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