Advanced MFC Programming

Chapter 13. Adding Special Features to Application
Also, when WM_SETTEXT or WM_SYSCOMMAND messages are received, the caption needs to be updated. So
within the two message handlers, message WM_NCPAINT is sent to the mainframe window:
LONG CMainFrame::OnSetText(WPARAM wParam, LPARAM lParam)
{
SendMessage(WM_NCPAINT, 0, 0);
return (LRESULT)TRUE;
}
void CMainFrame::OnSysCommand(UINT nID, LPARAM lParam)
{
CFrameWnd::OnSysCommand(nID, lParam);
if(::IsWindow(GetSafeHwnd()))SendMessage(WM_NCPAINT, 0, 0);
}
Figure 13-5 shows the result of the above implementation.
Figure 13-5. Customized caption bar
13.6 Irregular Shape Window
Theoretically speaking, all windows created in Windows system must be rectangular. This satisfies
our needs most of the time. However, sometimes it would be more preferable to let windows have irregular
shapes. For example, in multimedia type applications, sometimes we need to implement a special elliptical
(or more complex shape) “callout” window with a pointer pointing to an object, with the explanation of the
object displayed within the ellipse. The user may feel free to resize or move this window, and edit the text
within it (Figure 13-6).
Problem
Figure 13-6. Irregular shape window
To implement such type of window, we can let the application paint only within the elliptical area and
leave the rest area unchanged.
However, this will cause problem when the user moves or resizes the window. Although only the
elliptical area is painted, the window is essentially rectangular. By default, the portion not covered by the
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