Q148242: HOWTO: Handle OCM_CTLCOLORxxx Reflected Messages

Article: Q148242
Product(s): Microsoft C Compiler
Version(s): 4.0,4.1,4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbcode kbole kbActiveX kbCOMt kbCtrl kbMFC kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 kbGr
Last Modified: 12-JUN-2002

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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 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
   - Microsoft Visual C++.NET (2002) 
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SUMMARY
=======

This article shows you how to change the background color of an OLE control that
subclasses a Windows Control, with sample code for an Edit control.

This article should apply to Button, Static, ListBox, and ComboBox controls as
well.

MORE INFORMATION
================

Please refer to the following article in the Microsoft Knowledge Base:

  Q130952 WM_CTLCOLORxxx Message Changes for Windows 95

for more about the exact WM_CTLCOLORxxx message sent by each control. If a
control sends the WM_CTLCOLORSTATIC, you have to handle the OCM_CTLCOLORSTATIC
message in the OCX and so on.

To change the background color of an OLE Control that subclasses an Edit Control,
you must handle the OCM_CTLCOLOREDIT(32-bit) messages. These messages are
intercepted by the "reflector window" (created for an OLE control that
subclasses a Windows control) that reflects them back to the OLE control itself.
In response to these reflected messages, you must set the background color (and
optionally the foreground color) and return a handle to a brush initialized with
the background color.

Step-by-Step Example
--------------------

1. Generate an MFC ActiveX Control Wizard Application, and select the option
  that allows you to subclass an Edit control.

2. To handle an OCM_CTLCOLOREDIT reflected window message, declare the following
  handler function in the .h file of your control's class:

  LRESULT OnOcmCtlColor(WPARAM wParam, LPARAM lParam);

3. In the .cpp file of your control's class, add an ON_MESSAGE entry to the
  message map:

  ON_MESSAGE(OCM_CTLCOLOREDIT, OnOcmCtlColor)

4. Declare CBrush* m_pBackBrush in your control's .h file.

5. Set m_pBackBrush to NULL in the constructor.

6. Release the GDI object and delete the brush object in the control destructor:

  CEdtclrCtrl::~CEdtclrCtrl()
      {
         if(m_pBackBrush!=NULL)
  	{
             m_pBackBrush->DeleteObject();
             delete m_pBackBrush;
  	}
      }

REFERENCES
==========

Refer to technical article [ASCII 147]TN062: Message Reflection for Windows
Controls[ASCII 148] and the article [ASCII 147]ActiveX Controls: Sub-classing a
Windows Control in Visual C++ Programmer's Guide.[ASCII 148]

Additional query words: list box combo

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Keywords          : kbcode kbole kbActiveX kbCOMt kbCtrl kbMFC kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : :4.0,4.1,4.2,5.0,6.0
Issue type        : kbhowto

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