CSS in-/re-validations are significantly slower
One very big pain point in master right now is that CSS invalidations, or rather re-validations, are very slow. The amount of CSS nodes should not have increased a lot from gtk3, but we do a lot more CSS state changes, specifically when hovering widgets we didn't "hover" before like GtkWindow
itself or GtkListBox
. We also pushed focus management to CSS which means switching the focus widget will invalidate CSS nodes. And it's noticeably slow.
This was already a problem in gtk3 when doing the backdrop transition, but now we basically have it everywhere.