The style_set signal is emitted when a new style has been set on a widget.
Use the GtkWidget::style-updated signal
Note that style-modifying functions like modify_base also cause this signal to be emitted.
Note that this signal is emitted for changes to the deprecated Style. To track changes to the
GtkStyleContext associated with a widget, use the GtkWidget::style-updated signal.
| previous_style |
the previous style, or null if the widget just got its initial style |