When you move a window redirected via the Composite extension, the entire window is reported as damaged. This happens because: compMoveWindow calls miMoveWindow calls compCopyWindow Which was apparently written for the resizing case not the moving case; in the case where cw->pOldPixmap is NULL, it falls through to the non-redirected case. Not immediately clear how to fix to; perhaps pScreen->CopyWindow needs to be temporarily redirected before calling miMoveWindow or something.
I did some experiments with removing the DamageDamageRegion call in compositeCopyWindow, and it doesn't quite work - the builtin compositor doesn't properly recompose the moved window onto the parent window. (I turned out not to have a working real kdrive based server on the system, so I was doing testing with Xfake and lightpipe redirecting the root window to my main display. So all testing results should be taken with a big grain of salt.) I'll attach a version of my patch where I tried calling DamageDamageRegion on the parent window... that didn't help, but perhaps is closer to the right fix.
Created attachment 1299 [details] [review] Non-working attempt at a fix
*** This bug has been marked as a duplicate of bug 5275 ***
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