Provide the compositor with popover origin position
In GTK 3, popovers animated when they opened and closed. In GTK 4, this animated transition is no longer visible.
It seems that this is due to popovers becoming windows in GTK 4, which means that the compositor needs to do the animating. In order for the shell to do this, it will need to know the origin position of the popover, so it knows what the direction of the animation should be.
gnome-shell#4580 is for the shell part of this.