[gnome-shell/gnome-3-38] environment: Handle @content for property transitions

[Florian Müllner <fmuellner src gnome org>]

commit f231efe01582997c6beb44e53b6bef240f940afb
Author: Andre Moreira Magalhaes <andre endlessm com>
Date:   Wed Oct 7 23:21:04 2020 +0000

    environment: Handle @content for property transitions
    
    When using `Actor.ease_property` if the property starts with '@' and the
    duration of the transition is zero (which may happen if the actor is not
    mapped even if a non-zero duration was passed to `ease_property`), the
    impl will try getting the actual target object where the property should
    be set.
    
    This works fine for most cases but it currently throws an error when
    passing '@content.*' properties. Fix this by handling '@content' as
    a property of `actor.content` (used by MetaBackgroundActor when
    showing the overview).
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1461
    
    
    (cherry picked from commit cc9f66d78463b69840958d1997800a7a72b0ceb0)

 js/ui/environment.js | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/js/ui/environment.js b/js/ui/environment.js
index af0300dc78..e777d653ad 100644
--- a/js/ui/environment.js
+++ b/js/ui/environment.js
@@ -97,6 +97,8 @@ function _getPropertyTarget(actor, propName) {
         return [actor.get_action(name), prop];
     case '@constraints':
         return [actor.get_constraint(name), prop];
+    case '@content':
+        return [actor.content, name];
     case '@effects':
         return [actor.get_effect(name), prop];
     }