Bus.poll

Poll the bus for messages. Will block while waiting for messages to come. You can specify a maximum time to poll with the @timeout parameter. If @timeout is negative, this function will block indefinitely.

All messages not in @events will be popped off the bus and will be ignored. It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the @events mask

Because poll is implemented using the "message" signal enabled by gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message" signal to be emitted for every message that poll sees. Thus a "message" signal handler will see the same messages that this function sees -- neither will steal messages from the other.

This function will run a main loop from the default main context when polling.

You should never use this function, since it is pure evil. This is especially true for GUI applications based on Gtk+ or Qt, but also for any other non-trivial application that uses the GLib main loop. As this function runs a GLib main loop, any callback attached to the default GLib main context may be invoked. This could be timeouts, GUI events, I/O events etc.; even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks may do things you do not expect, e.g. destroy the main application window or some other resource; change other application state; display a dialog and run another main loop until the user clicks it away. In short, using this function may add a lot of complexity to your code through unexpected re-entrancy and unexpected changes to your application's state.

For 0 timeouts use gst_bus_pop_filtered() instead of this function; for other short timeouts use gst_bus_timed_pop_filtered(); everything else is better handled by setting up an asynchronous bus watch and doing things from there.