[Linux] Read MPRIS PlaybackStatus without introspection

linux/media/mediacontroller.cpp

@@ -288,8 +288,7 @@ QStringList MediaController::getPlayingMediaPlayers()
       continue;
     }
 
-    QVariant playbackStatus = playerInterface.property("PlaybackStatus");
-    if (playbackStatus.isValid() && playbackStatus.toString() == "Playing")
+    if (PlayerStatusWatcher::playbackStatusOf(service) == "Playing")
     {
       playingServices << service;
       LOG_DEBUG("Found playing service: " << service);
@@ -373,9 +372,9 @@ void MediaController::pause()
       continue;
     }
 
-    QVariant playbackStatus = playerInterface.property("PlaybackStatus");
-    LOG_DEBUG("PlaybackStatus for " << service << ": " << playbackStatus.toString());
-    if (!playbackStatus.isValid() || playbackStatus.toString() != "Playing")
+    const QString playbackStatus = PlayerStatusWatcher::playbackStatusOf(service);
+    LOG_DEBUG("PlaybackStatus for " << service << ": " << playbackStatus);
+    if (playbackStatus != "Playing")
     {
       continue;
     }

linux/media/playerstatuswatcher.cpp

@@ -47,21 +47,35 @@ void PlayerStatusWatcher::onServiceOwnerChanged(const QString &name, const QStri
     }
 }
 
+QString PlayerStatusWatcher::playbackStatusOf(const QString &playerService)
+{
+    if (playerService.isEmpty()) {
+        return QString();
+    }
+
+    QDBusInterface props(playerService, "/org/mpris/MediaPlayer2",
+                         "org.freedesktop.DBus.Properties", QDBusConnection::sessionBus());
+    if (!props.isValid()) {
+        return QString();
+    }
+
+    QDBusReply<QVariant> reply = props.call("Get", "org.mpris.MediaPlayer2.Player", "PlaybackStatus");
+    if (!reply.isValid()) {
+        return QString();
+    }
+
+    return reply.value().toString();
+}
+
 QString PlayerStatusWatcher::getCurrentPlaybackStatus(const QString &playerService)
 {
     QDBusConnection bus = QDBusConnection::sessionBus();
     QStringList services = bus.interface()->registeredServiceNames().value();
 
     for (const QString &service : services) {
         if (service.startsWith("org.mpris.MediaPlayer2.")) {
-            QDBusInterface iface(service, "/org/mpris/MediaPlayer2",
-                               "org.mpris.MediaPlayer2.Player", bus);
-
-            if (iface.isValid()) {
-                QVariant status = iface.property("PlaybackStatus");
-                if (status.isValid() && status.toString() == "Playing") {
-                    return status.toString();
-                }
+            if (playbackStatusOf(service) == "Playing") {
+                return QStringLiteral("Playing");
             }
         }
     }

linux/media/playerstatuswatcher.h

@@ -9,6 +9,9 @@ class PlayerStatusWatcher : public QObject {
 public:
     explicit PlayerStatusWatcher(const QString &playerService, QObject *parent = nullptr);
     static QString getCurrentPlaybackStatus(const QString &playerService);
+    // Chromium serves an empty Introspect document, so the metaobject QDBusInterface builds
+    // from it has no PlaybackStatus and property() reads invalid on a player that is Playing.
+    static QString playbackStatusOf(const QString &playerService);
 
 signals:
     void playbackStatusChanged(const QString &status);