How to draw in the nonclient area?

Question

I'd like to be able to do some drawing to the right of the menu bar, in the nonclient area of a window.

Is this possible, using C++ / MFC?

Answer 1

Charlie hit on the answer with WM_NCPAINT . If you're using MFC, the code would look something like this:

// in the message map
ON_WM_NCPAINT()

// ...

void CMainFrame::OnNcPaint()
{
   // still want the menu to be drawn, so trigger default handler first
   Default();

   // get menu bar bounds
   MENUBARINFO menuInfo = {sizeof(MENUBARINFO)};
   if ( GetMenuBarInfo(OBJID_MENU, 0, &menuInfo) )
   {
      CRect windowBounds;
      GetWindowRect(&windowBounds);
      CRect menuBounds(menuInfo.rcBar);
      menuBounds.OffsetRect(-windowBounds.TopLeft());

      // horrible, horrible icon-drawing code. Don't use this. Seriously.
      CWindowDC dc(this);
      HICON appIcon = (HICON)::LoadImage(AfxGetResourceHandle(), MAKEINTRESOURCE(IDR_MAINFRAME), IMAGE_ICON, 16, 16, LR_DEFAULTCOLOR);
      ::DrawIconEx(dc, menuBounds.right-18, menuBounds.top+2, appIcon, 0,0, 0, NULL, DI_NORMAL);
      ::DestroyIcon(appIcon);
   }
}

Answer 2

为了在非客户区域绘制，您需要获得“窗口”DC（而不是“客户端”DC），并在“窗口”DC中绘制。

Answer 3

You should try handling WM_NCPAINT. This is similar to a normal WM_PAINT message, but deals with the entire window, rather than just the client area. The MSDN documents on WM_NCPAINT provide the following sample code:

case WM_NCPAINT:
{
 HDC hdc;
 hdc = GetDCEx(hwnd, (HRGN)wParam, DCX_WINDOW|DCX_INTERSECTRGN);
 // Paint into this DC
 ReleaseDC(hwnd, hdc);
}

This code is intended to be used in the message loop of your applicaton, which is canonically organized using a large 'switch' statement.

As noted in the MFC example from Shog, make sure to call the default version, which in this example would mean a call to DefWindowProc.

Answer 4

If you just want something in the menu bar, maybe it is easier/cleaner to add it as a right-aligned menu item. This way it'll also work with different Windows themes, etc.