gboolean gtk_style_context_state_is_running ( GtkStyleContext* context, GtkStateType state, gdouble* progress )
TRUE if there is a transition animation running for the
current region (see gtk_style_context_push_animatable_region()).
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.
This function always returns
A widget state.
Return location for the transition progress.
The argument will be set by the function.