I wanna draw any window surface without window-type limitation.
So far, using PrintWindow API seems to be a good choice, but I never
successfully invoke it. Always return false. I totally don't know why.
Sigh...

WM_PAINT? Some controls never response to her. :-(

Bitblt? This most straightfoward method can't meet a window which is
invisible, covered....

Is there some common approach to achieve this.

thx in advance