You may want an action to happen at a specific moment in the timeline. Instead of polling with clutter_timeline_get_progress() you should instead use timeline markers. Timeline markers can be added with the clutter_timeline_add_marker_at_time() function. Handle the marker-reached signal to start the appropriate action at that moment, after checking the provided marker name. To handle only the signal only for a particular marker, you may connect to the marker-reached::my_marker signal, where my-marker is the name of your marker.

You can also use markers to navigate through the timeline using the clutter_timeline_advance_to_marker() function.