WindowSwitcher: avoid grabbing modal proxy multiple times (#2761)

Co-authored-by: Danielle Foré <danielle@elementary.io>

Author: lenemter

data/gala.metainfo.xml.in

@@ -42,6 +42,7 @@
         <issue url="https://github.com/elementary/gala/issues/2675">Blur behind modal shell protocol</issue>
         <issue url="https://github.com/elementary/gala/issues/2676">Window selection from dock overview doesn't focus the chosen window</issue>
         <issue url="https://github.com/elementary/gala/issues/2685">Move to new workspace on fullscreen not working</issue>
+        <issue url="https://github.com/elementary/gala/issues/2696">There is a transparent overlay window/object that prevents interaction with whatever is underneath it</issue>
         <issue url="https://github.com/elementary/dock/issues/537">Dock invisible</issue>
       </issues>
     </release>

src/Widgets/WindowSwitcher/WindowSwitcher.vala

@@ -20,7 +20,7 @@ public class Gala.WindowSwitcher : CanvasActor, GestureTarget, RootTarget {
 
     private GestureController gesture_controller;
     private int modifier_mask;
-    private Gala.ModalProxy modal_proxy = null;
+    private Gala.ModalProxy? modal_proxy;
     private Drawing.StyleManager style_manager;
     private Clutter.Actor container;
     private Gala.Text caption;
@@ -428,10 +428,13 @@ public class Gala.WindowSwitcher : CanvasActor, GestureTarget, RootTarget {
         }
 
         opened = show;
-        if (show) {
-            push_modal ();
-        } else {
+        if (show && modal_proxy == null) {
+            modal_proxy = wm.push_modal (get_stage (), true);
+            modal_proxy.allow_actions (SWITCH_WINDOWS | LOCATE_POINTER | MEDIA_KEYS);
+        } else if (modal_proxy != null) {
             wm.pop_modal (modal_proxy);
+            modal_proxy = null;
+
             get_stage ().set_key_focus (null);
         }
 
@@ -441,11 +444,6 @@ public class Gala.WindowSwitcher : CanvasActor, GestureTarget, RootTarget {
         restore_easing_state ();
     }
 
-    private void push_modal () {
-        modal_proxy = wm.push_modal (get_stage (), true);
-        modal_proxy.allow_actions (SWITCH_WINDOWS | LOCATE_POINTER | MEDIA_KEYS);
-    }
-
     private void close_switcher (uint32 time, bool cancel = false) {
         if (!opened) {
             return;