BUG: WebBrowser in MFC Does Not Repaint After showModalDialog

MORE INFORMATION

To reproduce this behavior, follow these steps:

1. Create an MFC application that hosts the WebBrowser control.
2. Using your MFC application, navigate to a Web page that calls the showModalDialog() function. Here is an example of how this is done:

   <SCRIPT LANGUAGE="VBScript">
      Sub Btn_onClick
         showModalDialog "test.htm"
      End Sub
   </SCRIPT>
   
   <BUTTON ID="Btn">Open a New Window</BUTTON>
   						

3. Close the modal dialog box.

After closing the dialog box, a white patch remains where the dialog box once was displayed. You can remove this white patch by performing an action that causes the client area to be repainted, such as minimizing and restoring the application.

When MFC hosts a control, it subclasses that control and passes certain messages to the control. This is the case for the WM_ERASEBKGND message.

When you close the dialog box that was created with showModalDialog(), MFC calls the windows procedure of the WebBrowser control and passes the WM_ERASEBKGND message. In this case, the WebBrowser control does not repaint itself.

In order to stop this problem from happening, you must prevent this message from being sent to the WebBrowser control. To do this, just handle the WM_ERASEBKGND message in your CView-derived class. Then, in your message handler, return without calling the base class version of the handler function.

Here is the MFC code that demonstrates how this should be done:

BOOL CWBView::OnEraseBkgnd(CDC* pDC)
{
   return FALSE;
}