[gnome-shell/gnome-3-28] workspaceThumbnail: rebuild thumbnails if workareas size changed

[Marco Trevisan <marcotrevi src gnome org>]

commit a27be6a540e87641a56241b379af2f05ecab7763
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Fri Jan 19 16:39:13 2018 +0100

    workspaceThumbnail: rebuild thumbnails if workareas size changed
    
    https://bugzilla.gnome.org/show_bug.cgi?id=792687
    
    
    (cherry picked from commit c29bd46e7a7e37a83849df8b3186c84eb46679ac)

 js/ui/workspaceThumbnail.js | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)
---
diff --git a/js/ui/workspaceThumbnail.js b/js/ui/workspaceThumbnail.js
index a1b0d9236..78fac80dd 100644
--- a/js/ui/workspaceThumbnail.js
+++ b/js/ui/workspaceThumbnail.js
@@ -673,11 +673,7 @@ var ThumbnailsBox = new Lang.Class({
         this._settings.connect('changed::dynamic-workspaces',
             this._updateSwitcherVisibility.bind(this));
 
-        Main.layoutManager.connect('monitors-changed', () => {
-            this._destroyThumbnails();
-            if (Main.overview.visible)
-                this._createThumbnails();
-        });
+        Main.layoutManager.connect('monitors-changed', this._rebuildThumbnails.bind(this));
     },
 
     _updateSwitcherVisibility() {
@@ -870,6 +866,9 @@ var ThumbnailsBox = new Lang.Class({
             Main.overview.connect('windows-restacked',
                                   this._syncStacking.bind(this));
 
+        this._workareasChangedId =
+            global.screen.connect('workareas-changed', this._rebuildThumbnails.bind(this));
+
         this._targetScale = 0;
         this._scale = 0;
         this._pendingScaleUpdate = false;
@@ -899,12 +898,24 @@ var ThumbnailsBox = new Lang.Class({
             this._syncStackingId = 0;
         }
 
+        if (this._workareasChangedId > 0) {
+            global.screen.disconnect(this._workareasChangedId);
+            this._workareasChangedId = 0;
+        }
+
         for (let w = 0; w < this._thumbnails.length; w++)
             this._thumbnails[w].destroy();
         this._thumbnails = [];
         this._porthole = null;
     },
 
+    _rebuildThumbnails() {
+        this._destroyThumbnails();
+
+        if (Main.overview.visible)
+            this._createThumbnails();
+    },
+
     _workspacesChanged() {
         let validThumbnails =
             this._thumbnails.filter(t => t.state <= ThumbnailState.NORMAL);