Before this commit, when a normal window is raised, xwayland thought it's
above always-on-top (AOT) windows even though it's actually below AOT
windows in the scene. This means mouse scroll events may be unexpectedly
sent to normal windows below AOT windows even when the cursor is hovering
over a AOT window.
So this commit fixes it by notifying the correct stacking order (where AOT
windows are placed above normal windows) to xwayland every time the
stacking order is updated.
Other benefits of this commit are:
- It makes the code more readable and predictable by aggregating logic
about stacking order management in xwayland (e.g. shaded windows or
windows in other workspaces should be notified to xwayland as being
placed at the bottom).
- As server->last_raised_view is removed in the previous commit, we were
notifying the stacking order to xwayland every time a window with dialog
windows is clicked (not when clicking a topmost window without dialogs,
due to some optimization in wlroots). This commit fixes this by caching
the window stacking order in xwayland_view->stacking_order and notifying
it to xwayland only when it's updated.
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