Returns %TRUE if there is a transition animation running for the
current region (see gtk_style_context_push_animatable_region()).
If @progress is not %NULL, the animation progress will be returned
there, 0.0 means the state is closest to being unset, while 1.0 means
it’s closest to being set. This means transition animation will
run from 0 to 1 when @state is being set and from 1 to 0 when
it’s being unset.
Returns %TRUE if there is a transition animation running for the current region (see gtk_style_context_push_animatable_region()).
If @progress is not %NULL, the animation progress will be returned there, 0.0 means the state is closest to being unset, while 1.0 means it’s closest to being set. This means transition animation will run from 0 to 1 when @state is being set and from 1 to 0 when it’s being unset.