Starting the animation from the actor 'paint' signal has various
unwanted consequences, such as sometimes trigger a
clutter_actor_queue_relayout() during the paint phase. One unwanted
consequence was that an offscreen actor effect was disabled during
painting, meaning the effect would begin being active, but later during
the post-paint processing being disabled. The caused said effect to push
an offscreen framebuffer to the paint context, but then just destroy it
instead of popping it. When this happened, we'd end up trying to operate
on a framebuffer that may had been finalized, or not, depending on the
garbage collector. Sometimes, for some users, this caused a segmentation
fault when trying to pop a matrix from the framebuffer matrix stack.
Deal with this more properly, by using the 'view-loaded' signal to wait
with animation until the view is loaded, as well as using MetaLater to
schedule the start of the animation.
For when a view was signalled to be ready, we're in a state where we can
start animation before the next frame as the layout is ready, but when
not, we have to add back the "hack" where we must wait for one frame for
the target icon positions to be up to date. Do this by adding a
MetaLater IDLE callback that starts the animation *after* the next
frame. This also needs the old 'opacity = 0' work around to not show an
incorrect first frame.
Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2418https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1154
5c33fe4a0a