Source.addChildSource

Adds child_source to source as a "polled" source; when source is added to a #GMainContext, child_source will be automatically added with the same priority, when child_source is triggered, it will cause source to dispatch (in addition to calling its own callback), and when source is destroyed, it will destroy child_source as well. (source will also still be dispatched if its own prepare/check functions indicate that it is ready.)

If you don't need child_source to do anything on its own when it triggers, you can call [gobject.global.sourceSetDummyCallback] on it to set a callback that does nothing (except return true if appropriate).

source will hold a reference on child_source while child_source is attached to it.

This API is only intended to be used by implementations of #GSource. Do not call this API on a #GSource that you did not create.