How to change the background color of an OLE control in Visual C++

This article describes how to modify the background color of an OLE control that subclasses a Windows Control. Sample code for an Edit control is provided.

This article also applies to Button, Static, ListBox, and ComboBox controls.

For more information about the exact WM_CTLCOLORxxx message that is sent by each control, click the following article number to view the article in the Microsoft Knowledge Base: 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;
   	}
       }
   					

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