Fix false-positive "GStreamer Not Found" warning in Preferences

The Preferences window's availability probe (added to surface missing
GStreamer deps in-UI) reused loadGstreamerModules(), which also checks
for Cogl. Cogl is Mutter's private library — its typelib is only
reachable from inside the actual gnome-shell process (which gets a
private GI search path), never from the separate, plain-GTK4
Preferences process. So the check always failed there with "Requiring
Cogl ... not found" even when live wallpapers were working correctly
in the real shell process, as confirmed by a user report where the
extension's own log showed live wallpaper playback starting cleanly
while Preferences simultaneously claimed GStreamer was missing.

Split into loadGstreamerModules() (Gst+GstApp+Cogl, used only by
liveWallpaper.js in the shell process) and a new lighter
checkGstreamerBaseAvailable() (Gst+GstApp only) for prefs.js, with a
note in the UI that a clean check there isn't a full guarantee since
the private half can't be verified from that process.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019RDqbdjsiisSU7CbQke4g8

lib/gstreamerAvailability.js

@@ -1,14 +1,16 @@
 /**
  * Loads the GObject-Introspection bindings the live wallpaper feature needs
  * (Gst, GstApp for the appsink signals, Cogl for uploading decoded frames)
- * and initializes GStreamer. Shared by extension.js (to actually run the
+ * and initializes GStreamer. Used by liveWallpaper.js, which only ever runs
- * pipeline) and prefs.js (to tell the user up front why the feature is
+ * inside the gnome-shell process itself.
- * greyed out), since either process may be missing the system packages
- * that provide these typelibs.
  *
- * Throws with a descriptive message on failure; never caches a *failure*,
+ * Cogl is Mutter's *private* library: its typelib is only reachable from
- * since the user may install the missing packages and reopen preferences
+ * gnome-shell's own process (which gets a private search path), never from
- * without restarting the shell.
+ * an ordinary GTK application. Do NOT reuse this for a diagnostic check in
+ * prefs.js — that runs in a separate, plain GTK4 process where importing
+ * Cogl will *always* fail regardless of whether live wallpapers actually
+ * work, producing a false "not found" report. Use
+ * checkGstreamerBaseAvailable() there instead.
  */
 export async function loadGstreamerModules() {
     const [{default: Gst}, , {default: Cogl}] = await Promise.all([
@@ -23,6 +25,23 @@ export async function loadGstreamerModules() {
     return {Gst, Cogl};
 }
 
+/**
+ * Lighter check for prefs.js: confirms the system-wide GStreamer packages
+ * (Gst core + the "app" plugin providing GstApp) are installed, without
+ * touching Cogl. This can't fully confirm live wallpapers will work (that
+ * also needs Cogl, only checkable from inside gnome-shell itself), but a
+ * failure here is a genuine, actionable problem, unlike a Cogl probe.
+ */
+export async function checkGstreamerBaseAvailable() {
+    const [{default: Gst}] = await Promise.all([
+        import('gi://Gst?version=1.0'),
+        import('gi://GstApp?version=1.0'),
+    ]);
+
+    if (!Gst.is_initialized())
+        Gst.init(null);
+}
+
 export const GSTREAMER_INSTALL_HINT =
     'Install GStreamer’s "base" and "good" plugin sets (with their GObject-Introspection data), ' +
     'which provide playback and GIF decoding:\n' +

prefs.js

@@ -6,12 +6,12 @@ import Gdk from 'gi://Gdk';
 import {ExtensionPreferences, gettext as _} from 'resource:///org/gnome/Shell/Extensions/js/extensions/prefs.js';
 
 import {SettingsKey} from './lib/settingsKeys.js';
-import {loadGstreamerModules, GSTREAMER_INSTALL_HINT} from './lib/gstreamerAvailability.js';
+import {checkGstreamerBaseAvailable, GSTREAMER_INSTALL_HINT} from './lib/gstreamerAvailability.js';
 
 export default class BenthicBloomPreferences extends ExtensionPreferences {
     async fillPreferencesWindow(window) {
         const settings = this.getSettings();
-        const gstreamerError = await loadGstreamerModules().then(() => null, e => e.message ?? String(e));
+        const gstreamerError = await checkGstreamerBaseAvailable().then(() => null, e => e.message ?? String(e));
 
         window.set_default_size(640, 720);
         window.add(this._buildGeneralPage(settings));
@@ -192,7 +192,9 @@ export default class BenthicBloomPreferences extends ExtensionPreferences {
             description: _(
                 'Play a looping video or animated GIF as your desktop background instead of a static image. ' +
                 'Requires GStreamer (with its "good" and "base" plugin sets, which provide GIF decoding) ' +
-                'to be installed on your system.'),
+                'to be installed on your system. Note: this page can only detect GStreamer being ' +
+                'completely missing — the rendering path it also needs is private to gnome-shell and can’t ' +
+                'be checked from here, so the absence of a warning below isn’t a full guarantee.'),
         });
         page.add(group);
         group.add(this._switchRow(