Invalidating non-client areas

I've a window which has custom border/caption, in order to do that I handle WM_NCPAINT message. My caption has two backgrounds a brighter one for the active window, and a darker one for the background window.

But under some circumstances, for example when the window loses/gain focus, my caption is not updated so I en开发者_如何学God with the wrong background.

Until now I've handled WM_NCACTIVATE, and send a RedrawWindow(hwnd, NULL, NULL, RDW_FRAME|RDW_INVALIDATE), but this causes the whole window to repaint. Do you have any advice about this?

Overriding non-client area is always fraught with peril. It seems the Window manager makes a lot of assumptions for optimization. Clearly it can be done, see Office, but it might take a lot of experimentation.

Just an idea. Call RedrawWindow twice, once to invalidate the non-client area then again to validate the client area.

RedrawWindow(hwnd, NULL, NULL, RDW_FRAME | RDW_INVALIDATE);
RedrawWindow(hwnd, NULL, NULL, RDW_NOFRAME | RDW_VALIDATE);

Another idea is to try to paint just the frame immediately, without invalidating anything:

RedrawWindow(hwnd, NULL, NULL, RDW_FRAME | RDW_UPDATENOW | RDW_NOCHILDREN);

Yet another idea is to specify an empty RECT or HREGION in the 2nd or 3rd parameters. It might not invalidate the client area that way.

Actually, this does the trick:

SetWindowPos(hwnd, 0, 0, 0, 0, 0,
    SWP_DRAWFRAME|SWP_NOMOVE|SWP_NOSIZE|SWP_NOACTIVATE|SWP_NOZORDER);