Added metaDataChanged(key,value) signal to metadata controls.

It may be more efficient and convenient for application to use this
signal instead of metaDataChanged().

metaDataChanged() signal is emitted for compatibility,
backends should emit both signals.

Signal added QMetadataReader/WritterControl,
QMediaObject and QMediaRecorder.

Change-Id: I5ca34a40e64b22034e6fde8cd7f9735cc3f72c68
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/gstreamer/mediacapture/qgstreamercapturemetadatacontrol.cpp

@@ -149,6 +149,7 @@ void QGstreamerCaptureMetaDataControl::setMetaData(const QString &key, const QVa
             m_values.insert(QByteArray::fromRawData(name, qstrlen(name)), value);
 
             emit QMetaDataWriterControl::metaDataChanged();
+            emit QMetaDataWriterControl::metaDataChanged(key, value);
             emit metaDataChanged(m_values);
 
             return;

src/plugins/gstreamer/mediaplayer/qgstreamermetadataprovider.cpp

@@ -126,6 +126,11 @@ QGstreamerMetaDataProvider::QGstreamerMetaDataProvider(QGstreamerPlayerSession *
     :QMetaDataReaderControl(parent), m_session(session)
 {
     connect(m_session, SIGNAL(tagsChanged()), SLOT(updateTags()));
+
+    const int count = sizeof(qt_gstreamerMetaDataKeys) / sizeof(QGstreamerMetaDataKeyLookup);
+    for (int i = 0; i < count; ++i) {
+        m_keysMap[QByteArray(qt_gstreamerMetaDataKeys[i].token)] = qt_gstreamerMetaDataKeys[i].key;
+    }
 }
 
 QGstreamerMetaDataProvider::~QGstreamerMetaDataProvider()
@@ -144,39 +149,41 @@ bool QGstreamerMetaDataProvider::isWritable() const
 
 QVariant QGstreamerMetaDataProvider::metaData(const QString &key) const
 {
-    static const int count = sizeof(qt_gstreamerMetaDataKeys) / sizeof(QGstreamerMetaDataKeyLookup);
-
-    for (int i = 0; i < count; ++i) {
-        if (qt_gstreamerMetaDataKeys[i].key == key) {
-            return m_session->tags().value(QByteArray(qt_gstreamerMetaDataKeys[i].token));
-        }
-    }
-    return QVariant();
+    return m_tags.value(key);
 }
 
 QStringList QGstreamerMetaDataProvider::availableMetaData() const
 {
-    static QMap<QByteArray, QString> keysMap;
-    if (keysMap.isEmpty()) {
-        const int count = sizeof(qt_gstreamerMetaDataKeys) / sizeof(QGstreamerMetaDataKeyLookup);
-        for (int i = 0; i < count; ++i) {
-            keysMap[QByteArray(qt_gstreamerMetaDataKeys[i].token)] = qt_gstreamerMetaDataKeys[i].key;
-        }
-    }
-
-    QStringList res;
-    foreach (const QByteArray &key, m_session->tags().keys()) {
-        QString tag = keysMap.value(key);
-        if (!tag.isEmpty())
-            res.append(tag);
-    }
-
-    return res;
+    return m_tags.keys();
 }
 
 void QGstreamerMetaDataProvider::updateTags()
 {
-    emit metaDataChanged();
+    QVariantMap oldTags = m_tags;
+    m_tags.clear();
+
+    QSet<QString> allTags = QSet<QString>::fromList(m_tags.keys());
+
+    QMapIterator<QByteArray ,QVariant> i(m_session->tags());
+    while (i.hasNext()) {
+         i.next();
+         //use gstreamer native keys for elements not in m_keysMap
+         QString key = m_keysMap.value(i.key(), i.key());
+         m_tags[key] = i.value();
+         allTags.insert(i.key());
+    }
+
+    bool changed = false;
+    foreach (const QString &key, allTags) {
+        const QVariant value = m_tags.value(key);
+        if (value != oldTags.value(key)) {
+            changed = true;
+            emit metaDataChanged(key, value);
+        }
+    }
+
+    if (changed)
+        emit metaDataChanged();
 }
 
 QT_END_NAMESPACE

src/plugins/gstreamer/mediaplayer/qgstreamermetadataprovider.h

@@ -66,6 +66,8 @@ private slots:
 
 private:
     QGstreamerPlayerSession *m_session;
+    QVariantMap m_tags;
+    QMap<QByteArray, QString> m_keysMap;
 };
 
 QT_END_NAMESPACE