workspace-indicator: Use overlap to determine preview visibility

In order to better reflect the actual workspace, show any preview
that is at least partially located on the monitor, not only those
that have the major part on that monitor.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/142>

(cherry picked from commit 50d3ee5703)

extensions/workspace-indicator/extension.js

@@ -32,13 +32,12 @@ class WindowPreview extends St.Button {
         this._sizeChangedId = this._window.connect('size-changed',
             () => this.queue_relayout());
         this._positionChangedId = this._window.connect('position-changed',
-            () => this.queue_relayout());
+            () => {
+                this._updateVisible();
+                this.queue_relayout();
+            });
         this._minimizedChangedId = this._window.connect('notify::minimized',
             this._updateVisible.bind(this));
-        this._monitorEnteredId = global.display.connect('window-entered-monitor',
-            this._updateVisible.bind(this));
-        this._monitorLeftId = global.display.connect('window-left-monitor',
-            this._updateVisible.bind(this));
 
         this._focusChangedId = global.display.connect('notify::focus-window',
             this._onFocusChanged.bind(this));
@@ -54,8 +53,6 @@ class WindowPreview extends St.Button {
         this._window.disconnect(this._sizeChangedId);
         this._window.disconnect(this._positionChangedId);
         this._window.disconnect(this._minimizedChangedId);
-        global.display.disconnect(this._monitorEnteredId);
-        global.display.disconnect(this._monitorLeftId);
         global.display.disconnect(this._focusChangedId);
     }
 
@@ -67,8 +64,9 @@ class WindowPreview extends St.Button {
     }
 
     _updateVisible() {
-        let monitor = Main.layoutManager.findIndexForActor(this);
-        this.visible = monitor === this._window.get_monitor() &&
+        const monitor = Main.layoutManager.findIndexForActor(this);
+        const workArea = Main.layoutManager.getWorkAreaForMonitor(monitor);
+        this.visible = this._window.get_frame_rect().overlap(workArea) &&
             this._window.window_type !== Meta.WindowType.DESKTOP &&
             this._window.showing_on_its_workspace();
     }