msdn—chm版vcc++Theframeworkcallsthismemberfunctionwhenthenonclientareaneedstobepainted.Thedefaultimplementationpaintsthewindowframe.Anapplicationcanoverridethiscallandpaintitsowncustomwindowframe.Theclippingregionisalwaysrectangular,eveniftheshapeoftheframeisaltered.