Fixes/revert x11 popup changes

[kekekeks]

#14366 has basically broken popups and made them constrained to the window itself. This is a major breaking change for most of actual desktop apps, so it's getting reverted alongside with later positioning fix.

[kekekeks]

@marysaka I can't check with gamescope since it refuses to run properly on my hardware, but from your description it seems that it's ignoring override_redirect flag on XWayland windows, so I'd suggest to try setting WM_TRANSIENT_FOR hint for popups and see if it helps.

[marysaka]

@marysaka I can't check with gamescope since it refuses to run properly on my hardware, but from your description it seems that it's ignoring override_redirect flag on XWayland windows, so I'd suggest to try setting WM_TRANSIENT_FOR hint for popups and see if it helps.

I will try to give that a shot this week-end.

[marysaka]

@kekekeks WM_TRANSIENT_FOR hint doesn't change a thing, however I found part of the issue.

if _useRenderWindow is set to false, the rendering does work properly. Considering the comment attached on it, would it be acceptable to set it to false when using a popup because as far as I know popup cannot be resized?