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I don't really know if this is the right place to ask this, but why can you sometimes draw with windows on Windows XP, and what causes it? You know when your machine lags, and all of a sudden, when you move a window, it leaves behind a trail? that's what I mean.

tauon
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1 Answers1

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This is actually more suited to the Retro Computing Stack Exchange (given the age of XP), but I'll answer it anyway.

Windows XP (and earlier NT versions, NT 3.5, 4.0, 2000) had a bug in which the order of moving the window and restoring the background in the old windows position could sometimes get out of sync. Especially if you moved the windows faster than the system could render screen-updates. Which wasn't that hard to do on a relatively slow video card or if the computer was lagging due to heavy CPU load (as you noticed already).

This caused to the background being restored BEFORE (in stead of after) the last render of the window in the old position.
So after the background restore the last render of the window would overwrite the just restored background. And the Windows display-manager would only restore background once, so you where left with a trail of window-edges left behind.

If I recall correctly this got fixed with the Windows XP Media-centre Edition in 2002 and for regular XP with Service-Pack 2, which brought most updates from Media-centre to the regular XP. (XP with SP2 and the separate Media-centre appliciation where together functionaly equivalent to XP Media-Centre Edition.)
Server 2003 was based on the same core as XP Media-Centre, so it never had the bug either.

Tonny
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