Window management in DOS...

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I'm writing a library in Assembley that manages windows

in DOS, like Turbo Vision. The only problem that I'm

having is redrawing a window that was underneath

another window when the window is moved or closed so

it's no longer over it. I've thought of 2 solutions for

the problem:

1) Every time a window is created store all of the

video memory of everything underneath the new

window before I draw it on the screen. I want to

avoid this because it will take up a lot of memory

very fast, especially if it's in a graphics mode,

and not text.

2) Every time a window is moved or closed call a

function to redraw the region of the window that

needs to be redrawn.

Does anyone have proven methods of doing what I want

to do here? Or possibly some examples of source code

for such?