[gnome-shell/gnome-3-36] backgroundManager: Always emit 'loaded' signal

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 5f509855e24ba391c44f2af2a170e077aa0bc93f
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Jul 22 10:32:49 2020 +0000

    backgroundManager: Always emit 'loaded' signal
    
    As backgrounds are cached, it is possible that we never emit the
    'loaded' signal added in commit f386103bc1. We are relying on the
    signal though, so do the same as Background and emit the signal
    from an idle if the background was already loaded.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1371
    
    
    (cherry picked from commit 5c550daecb18fff1ef98a48374ceec71f270ce89)

 js/ui/background.js | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index 91e6be0f1d..d08e2ec363 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -758,11 +758,19 @@ var BackgroundManager = class BackgroundManager {
             this._updateBackgroundActor();
         });
 
-        let loadedSignalId = background.connect('loaded', () => {
-            background.disconnect(loadedSignalId);
-            loadedSignalId = null;
-            this.emit('loaded');
-        });
+        let loadedSignalId;
+        if (background.isLoaded) {
+            GLib.idle_add(GLib.PRIORITY_DEFAULT, () => {
+                this.emit('loaded');
+                return GLib.SOURCE_REMOVE;
+            });
+        } else {
+            loadedSignalId = background.connect('loaded', () => {
+                background.disconnect(loadedSignalId);
+                loadedSignalId = null;
+                this.emit('loaded');
+            });
+        }
 
         backgroundActor.connect('destroy', () => {
             if (changeSignalId)