backgroundApps: Track apps instead of instances

The background apps menu currently tracks instances rather than
apps. That matches the behavior of `flatpak ps` and can be useful,
for example when one particular instance runs out of control.

But as we don't include any information that allows to actually
distinguish between instances, multiple instances appear simply
as duplicated app entries.

Given that a menu is too limited for detailed information, stop
representing individual instances, and track apps instead.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6654

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2790>

js/ui/status/backgroundApps.js

@@ -24,9 +24,6 @@ var BackgroundAppMenuItem = GObject.registerClass({
         'app': GObject.ParamSpec.object('app', '', '',
             GObject.ParamFlags.READWRITE,
             Shell.App),
-        'instance': GObject.ParamSpec.int64('instance', '', '',
-            GObject.ParamFlags.READWRITE,
-            -1, GLib.MAXINT64_BIGINT, -1),
         'message': GObject.ParamSpec.string('message', '', '',
             GObject.ParamFlags.READWRITE,
             null),
@@ -36,16 +33,13 @@ var BackgroundAppMenuItem = GObject.registerClass({
         const message = params.message;
         delete params.message;
 
-        const instance = params.instance;
-        delete params.instance;
-
         super._init(app.get_name(), app.get_icon(), {
             activate: false,
             reactive: false,
             ...params,
         });
 
-        this.set({message, instance});
+        this.set({message});
 
         this.add_style_class_name('background-app-item');
         this.label.add_style_class_name('title');
@@ -134,7 +128,7 @@ var BackgroundAppMenuItem = GObject.registerClass({
                 null);
         } catch (_error) {
             try {
-                Util.trySpawn(['flatpak', 'kill', this.instance]);
+                Util.trySpawn(['flatpak', 'kill', appId]);
             } catch (pidError) {
                 logError(pidError, 'Failed to kill application');
             }
@@ -213,7 +207,35 @@ class BackgroundAppsToggle extends QuickToggle {
 
         const {BackgroundApps: backgroundApps} = this._proxy;
 
-        const nBackgroundApps = backgroundApps?.length ?? 0;
+        this._appsSection.removeAll();
+
+        const items = new Map();
+        (backgroundApps ?? [])
+            .map(backgroundApp => {
+                const appId = backgroundApp.app_id.deepUnpack();
+                const app = this._appSystem.lookup_app(`${appId}.desktop`);
+                const message = backgroundApp.message?.deepUnpack();
+
+                return {app, message};
+            })
+            .sort((a, b) => {
+                return a.app.get_name().localeCompare(b.app.get_name());
+            })
+            .forEach(backgroundApp => {
+                const {app, message} = backgroundApp;
+
+                let item = items.get(app);
+                if (!item) {
+                    item = new BackgroundAppMenuItem(app);
+                    items.set(app, item);
+                    this._appsSection.addMenuItem(item);
+                }
+
+                if (message)
+                    item.set({message});
+            });
+
+        const nBackgroundApps = items.size;
         this.title = nBackgroundApps === 0
             ? _('No Background Apps')
             : ngettext(
@@ -221,31 +243,6 @@ class BackgroundAppsToggle extends QuickToggle {
                 '%d Background Apps',
                 nBackgroundApps).format(nBackgroundApps);
         this._listTitle.visible = nBackgroundApps > 0;
-
-        this._appsSection.removeAll();
-
-        if (!backgroundApps)
-            return;
-
-        backgroundApps
-            .map(backgroundApp => {
-                const appId = backgroundApp.app_id.deepUnpack();
-                const app = this._appSystem.lookup_app(`${appId}.desktop`);
-                const message = backgroundApp.message?.deepUnpack();
-                const instance = backgroundApp.instance.deepUnpack();
-
-                return {app, message, instance};
-            })
-            .sort((a, b) => {
-                return a.app.get_name().localeCompare(b.app.get_name());
-            })
-            .forEach(backgroundApp => {
-                const {app, message, instance} = backgroundApp;
-
-                const item = new BackgroundAppMenuItem(app,
-                    {instance, message});
-                this._appsSection.addMenuItem(item);
-            });
     }
 
     vfunc_clicked() {