Allow focusing a window via DesktopIntegration (#1817)

Co-authored-by: Leo <[email protected]>

src/DesktopIntegration.vala

@@ -100,6 +100,17 @@ public class Gala.DesktopIntegration : GLib.Object {
         return (owned) returned_windows;
     }
 
+    public void focus_window (uint64 uid) throws GLib.DBusError, GLib.IOError {
+        var apps = Gala.AppSystem.get_default ().get_running_apps ();
+        foreach (unowned var app in apps) {
+            foreach (weak Meta.Window window in app.get_windows ()) {
+                if (window.get_id () == uid) {
+                    window.activate (wm.get_display ().get_current_time ());
+                }
+            }
+        }
+    }
+
     public void show_windows_for (string app_id) throws IOError, DBusError {
         if (wm.window_overview == null) {
             throw new IOError.FAILED ("Window overview not provided by window manager");