xdg-shell: Add callbacks for app-id and title changes

Otherwise there's no good way to track this.

src/wayland/shell/xdg/handlers/surface/toplevel.rs

@@ -51,15 +51,35 @@ where
             }
             xdg_toplevel::Request::SetTitle { title } => {
                 // Title is not double buffered, we can set it directly
-                with_surface_toplevel_role_data(toplevel, |data| {
-                    data.title = Some(title);
+                let changed = with_surface_toplevel_role_data(toplevel, |role| {
+                    if role.title.as_ref() != Some(&title) {
+                        role.title = Some(title);
+                        true
+                    } else {
+                        false
+                    }
                 });
+
+                if changed {
+                    let handle = make_toplevel_handle(toplevel);
+                    XdgShellHandler::title_changed(state, handle);
+                }
             }
             xdg_toplevel::Request::SetAppId { app_id } => {
                 // AppId is not double buffered, we can set it directly
-                with_surface_toplevel_role_data(toplevel, |role| {
-                    role.app_id = Some(app_id);
+                let changed = with_surface_toplevel_role_data(toplevel, |role| {
+                    if role.app_id.as_ref() != Some(&app_id) {
+                        role.app_id = Some(app_id);
+                        true
+                    } else {
+                        false
+                    }
                 });
+
+                if changed {
+                    let handle = make_toplevel_handle(toplevel);
+                    XdgShellHandler::app_id_changed(state, handle);
+                }
             }
             xdg_toplevel::Request::ShowWindowMenu { seat, serial, x, y } => {
                 // This has to be handled by the compositor

src/wayland/shell/xdg/mod.rs

@@ -1157,6 +1157,12 @@ pub trait XdgShellHandler {
 
     /// A popup surface was destroyed.
     fn popup_destroyed(&mut self, surface: PopupSurface) {}
+
+    /// The toplevel surface set a different app id.
+    fn app_id_changed(&mut self, surface: ToplevelSurface) {}
+
+    /// The toplevel surface set a different title.
+    fn title_changed(&mut self, surface: ToplevelSurface) {}
 }
 
 /// Shell global state