[gnome-shell] appDisplay: Don't start animation from the 'paint' signal

[Florian Müllner <fmuellner src gnome org>]

commit 5c33fe4a0a4eb4ed8cc35ad65e3e4c65da93c790
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Mar 30 15:16:53 2020 +0200

    appDisplay: Don't start animation from the 'paint' signal
    
    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/2418
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1154

 js/ui/appDisplay.js | 44 ++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 4 deletions(-)
---
diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 4f3d88df54..2d57a6df26 100644
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -192,6 +192,9 @@ var BaseAppView = GObject.registerClass({
             this._items.set(icon.id, icon);
         });
 
+        this._animateLaterId = 0;
+        this._viewLoadedHandlerId = 0;
+        this._viewIsReady = true;
         this.emit('view-loaded');
     }
 
@@ -241,6 +244,18 @@ var BaseAppView = GObject.registerClass({
             Main.overview.dash.showAppsButton);
     }
 
+    _clearAnimateLater() {
+        if (this._animateLaterId) {
+            Meta.later_remove(this._animateLaterId);
+            this._animateLaterId = 0;
+        }
+        if (this._viewLoadedHandlerId) {
+            this.disconnect(this._viewLoadedHandlerId);
+            this._viewLoadedHandlerId = 0;
+        }
+        this._grid.opacity = 255;
+    }
+
     animate(animationDirection, onComplete) {
         if (onComplete) {
             let animationDoneId = this._grid.connect('animation-done', () => {
@@ -249,11 +264,28 @@ var BaseAppView = GObject.registerClass({
             });
         }
 
+        this._clearAnimateLater();
+
         if (animationDirection == IconGrid.AnimationDirection.IN) {
-            let id = this._grid.connect('paint', () => {
-                this._grid.disconnect(id);
-                this._doSpringAnimation(animationDirection);
-            });
+            const doSpringAnimationLater = laterType => {
+                this._animateLaterId = Meta.later_add(laterType,
+                    () => {
+                        this._animateLaterId = 0;
+                        this._doSpringAnimation(animationDirection);
+                        return GLib.SOURCE_REMOVE;
+                    });
+            };
+
+            if (this._viewIsReady) {
+                this._grid.opacity = 0;
+                doSpringAnimationLater(Meta.LaterType.IDLE);
+            } else {
+                this._viewLoadedHandlerId = this.connect('view-loaded',
+                    () => {
+                        this._clearAnimateLater();
+                        doSpringAnimationLater(Meta.LaterType.BEFORE_REDRAW);
+                    });
+            }
         } else {
             this._doSpringAnimation(animationDirection);
         }
@@ -375,15 +407,19 @@ var AllView = GObject.registerClass({
         this._lastOvershootY = -1;
         this._lastOvershootTimeoutId = 0;
 
+        this._viewIsReady = false;
+
         Main.overview.connect('hidden', () => this.goToPage(0));
 
         this._redisplayWorkId = Main.initializeDeferredWork(this, this._redisplay.bind(this));
 
         Shell.AppSystem.get_default().connect('installed-changed', () => {
+            this._viewIsReady = false;
             Main.queueDeferredWork(this._redisplayWorkId);
         });
         this._folderSettings = new Gio.Settings({ schema_id: 'org.gnome.desktop.app-folders' });
         this._folderSettings.connect('changed::folder-children', () => {
+            this._viewIsReady = false;
             Main.queueDeferredWork(this._redisplayWorkId);
         });