[gnome-shell] windowManager: Show window resizing clone on "size-changed"

[Florian Müllner <fmuellner src gnome org>]

commit da05c85f3c8e76e3bef2984c6a68dddf45010951
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Fri Feb 28 16:43:48 2020 +0100

    windowManager: Show window resizing clone on "size-changed"
    
    When a window is being resized by the compositor, with Wayland the
    compositor first asks the window to change its size and emits the
    "size-change" signal, and then emits the "size-changed" signal after
    the window acknowledges the new size. To show a fancy resize animation,
    gnome-shell creates a "screenshot" of the resizing window on the
    "size-change" signal, and later animates that "screenshot" to the new
    window size on the "size-changed" signal.
    
    Now if a client is not responding to our requests asking it to change
    its size, we get a "size-change" signal and start showing the
    window-clone, but never a "size-changed" signal, animating and hiding
    the clone again. This causes a so called "ghost window" that is shown
    above everything else and never disappears again.
    
    To fix that, start showing the window clone once we get the
    "size-changed" signal instead of the "size-change" signal. This makes
    sure the window actually updates its size and the clone is going to be
    hidden again.
    
    Fixes https://gitlab.gnome.org/GNOME/mutter/issues/1078
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/1055

 js/ui/windowManager.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/js/ui/windowManager.js b/js/ui/windowManager.js
index 075fbb15bb..53f1845615 100644
--- a/js/ui/windowManager.js
+++ b/js/ui/windowManager.js
@@ -1259,7 +1259,6 @@ var WindowManager = class {
         actorClone.set_offscreen_redirect(Clutter.OffscreenRedirect.ALWAYS);
         actorClone.set_position(oldFrameRect.x, oldFrameRect.y);
         actorClone.set_size(oldFrameRect.width, oldFrameRect.height);
-        Main.uiGroup.add_actor(actorClone);
 
         if (this._clearAnimationInfo(actor))
             this._shellwm.completed_size_change(actor);
@@ -1290,6 +1289,8 @@ var WindowManager = class {
         this._resizePending.delete(actor);
         this._resizing.add(actor);
 
+        Main.uiGroup.add_child(actorClone);
+
         // Now scale and fade out the clone
         actorClone.ease({
             x: targetRect.x,