kwin resizes hidden windows most of the time. I see the existing flaky markers triggered on Windows 11 occasionally. This MR makes the ddraw-d3d9 tests run reliably on kwin (I tested version 5.27.7) in Xephyr and a real display.
This makes the !WS_VISIBLE tests fairly weak since we ignore the random failures we get on Windows and Wine.
According to https://marc.info/?l=wine-patches&m=141642450913299&w=2 , the mail to wine-patches behind commit f4d520d6e2, which added this test, those tests intended to cover some differences between d3d9 and d3d9ex, not a specific game behavior. I vaguely remember that I did run into something that needed this behavior, but I can't find out any more what this might have been. The memory of those 9 year old patches is getting blurry.