This is useful for autoplay for example. With autoplay, it is necessary to
wait until the scene graph is fully set up. This signal is emitted once the
QML item node is ready. So, inside a connected slot, the pipeline's state
can be set to PLAYING to automatically start playback as soon as the QML
script is loaded.
https://bugzilla.gnome.org/show_bug.cgi?id=786246
QML can destroy the video widget at any time, leaving
us with a dangling pointer. Use a lock and a proxy
object to cope with that, and block in the widget
destructor if there are ongoing calls into the widget.
Very much in the same spirit as the Gtk GL sink
Two things are provided
1. A QQuickItem subclass that renders out RGBA filled GstGLMemory
buffers that is instantiated from qml.
2. A sink element that will push buffers into (1)
To use
1. Declare the GstGLVideoItem in qml with an appropriate
objectName property set.
2. Get the aforementioned GstGLVideoItem from qml using something like
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
QObject *rootObject = engine.rootObjects().first();
QQuickItem *videoItem = rootObject->findChild<QQuickItem *> ("videoItem");
3. Set the videoItem on the sink
https://bugzilla.gnome.org/show_bug.cgi?id=752185
