Called by the framework when it needs to obtain a bitmap for live preview of the MDI child.
This parameter is TRUE if the bitmap is requested for the MDI child, which is currently active and the main window is not minimized. The default processing in this case takes a snapshot of the main window.
Specifies the location of the bitmap in the main (top level) window client coordinates. This point should be provided by the callee.
If processed, returns a handle to a valid 32bpp bitmap, otherwise NULL.
Override this method in a derived class and return a valid 32bpp bitmap for live preview of MDI child. This method is called only when the MDI child is displayed on Windows 7 taskbar tabs. If you return NULL, MFC calls the default handlers and obtains bitmaps using PrintClient or PrintWindow.