Hi,
I'm trying to make a simple function that draws a bitmap image to a window (effectively using a BitBlt call). This works fine, except that when the window is overlapped or moved so that the area where the image is is offscreen, the obscured parts of the image are removed and not redrawn.

Is there a way I can prevent Windows from destroying the data that's there (much like the AutoRedraw property in Visual Basic) or perhaps redraw selected regions of the image as opposed to the entire image (I tested that, it's sloooow )?