appswitcher: Fix Alt+Shift+Tab (13717)

- Update _show and _keyReleaseEvent to detect 'backward' keybindings.

- Adjust _currentIndex calculation to decrement for Alt+Shift+Tab.

Author: ArqamQazi

js/ui/appSwitcher/appSwitcher.js

@@ -341,8 +341,13 @@ AppSwitcher.prototype = {
         let state = mods & this._modifierMask;
 
         if (state == 0) {
-            if (this._initialDelayTimeoutId !== 0)
-                this._currentIndex = (this._currentIndex + 1) % this._windows.length;
+            if (this._initialDelayTimeoutId !== 0) {
+                let name = this._binding ? this._binding.get_name() : '';
+                if (name.includes('backward'))
+                    this._currentIndex = (this._currentIndex - 1 + this._windows.length) % this._windows.length;
+                else
+                    this._currentIndex = (this._currentIndex + 1) % this._windows.length;
+            }
             this._activateSelected();
         }
 

js/ui/appSwitcher/classicSwitcher.js

@@ -142,7 +142,12 @@ ClassicSwitcher.prototype = {
 
         this.actor.opacity = 255;
         this._initialDelayTimeoutId = 0;
-        this._next();
+
+        let name = this._binding ? this._binding.get_name() : '';
+        if (name.includes('backward'))
+            this._previous();
+        else
+            this._next();
     },
 
     _hide: function() {