void adw_leaflet_set_visible_child ( AdwLeaflet* self, GtkWidget* visible_child )
Sets the widget currently visible when the leaflet is folded.
The transition is determined by
AdwLeaflet:child-transition-params. The transition can be cancelled
by the user, in which case visible child will change back to the previously
The new child.
The data is owned by the caller of the method.