[gnome-shell] workspace: Update WorkspaceLayout workarea on changes

[Marge Bot <marge-bot src gnome org>]

commit 234024c4f4490b1cd8a3a0d797cb58fd013abd9f
Author: Sebastian Keller <skeller gnome org>
Date:   Tue Mar 16 21:26:33 2021 +0100

    workspace: Update WorkspaceLayout workarea on changes
    
    Previously the workarea was only set on construction and then never
    updated. As a result the preferred width and height as well as the
    allocation were based on an outdated workarea size when it changed after
    construction. This for example was happening during the startup
    animation, for which the WorkspaceLayout is constructed before the panel
    is shown. This caused the workspace in the overview to be slightly
    smaller when it is first shown and the overview closing animation to
    not expand the workspace to the correct size the first time it is
    closed.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3945
    Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3816
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1771>

 js/ui/workspace.js | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/workspace.js b/js/ui/workspace.js
index f8b0d40ed2..75efe4d992 100644
--- a/js/ui/workspace.js
+++ b/js/ui/workspace.js
@@ -413,9 +413,6 @@ var WorkspaceLayout = GObject.registerClass({
 
         this._metaWorkspace = metaWorkspace;
         this._monitorIndex = monitorIndex;
-        this._workarea = metaWorkspace
-            ? metaWorkspace.get_work_area_for_monitor(this._monitorIndex)
-            : Main.layoutManager.getWorkAreaForMonitor(this._monitorIndex);
         this._overviewAdjustment = overviewAdjustment;
 
         this._container = null;
@@ -435,6 +432,9 @@ var WorkspaceLayout = GObject.registerClass({
             this.syncOverlays();
             this.layout_changed();
         });
+
+        this._workarea = null;
+        this._workareasChangedId = 0;
     }
 
     _isBetterScaleAndSpace(oldScale, oldSpace, scale, space) {
@@ -563,8 +563,25 @@ var WorkspaceLayout = GObject.registerClass({
         return workarea;
     }
 
+    _syncWorkareaTracking() {
+        if (this._container) {
+            if (this._workAreaChangedId)
+                return;
+            this._workarea = Main.layoutManager.getWorkAreaForMonitor(this._monitorIndex);
+            this._workareasChangedId =
+                global.display.connect('workareas-changed', () => {
+                    this._workarea = Main.layoutManager.getWorkAreaForMonitor(this._monitorIndex);
+                    this.layout_changed();
+                });
+        } else if (this._workareasChangedId) {
+            global.display.disconnect(this._workareasChangedId);
+            this._workareasChangedId = 0;
+        }
+    }
+
     vfunc_set_container(container) {
         this._container = container;
+        this._syncWorkareaTracking();
         this._stateAdjustment.actor = container;
     }