[ddraw] asynchronous screen updates

[Lionel Ulmer]

> Then I would be drawing rectangles which are not ready for a redraw yet. Does 
> UnLock release only last lock or all locks on these old DX versions?

Well, you need to store the rectangle at Lock time but only draw it at
Unlock time. And I have no idea if any game ever does concurrent locks (so I
have no idea how concurrent lock work).

But anyway, with the update thread, there is no guarantee to not flush on
screen something that is not 'finished' (if the application locks rect A
then unlocks it then relocks the same rectangle A and the update thread
flushes on screen before the apps unlocks A, you will put on screen
unfinished stuff).

So setting the rectangle dirty on Lock is not going to give us that much
more garbage on screen than the usual stuff (and, moreover, this only is a
problem on Windowed applications or on non-double buffered games (which COMI
is the only example I know)).

      Lionel

-- 
		 Lionel Ulmer - http://www.bbrox.org/