Returns the relief style of @tool_item. See gtk_button_set_relief().
Custom subclasses of #GtkToolItem should call this function in the handler
of the #GtkToolItem::toolbar_reconfigured signal to find out the
relief style of buttons.
Return: a #GtkReliefStyle indicating the relief style used
for @tool_item.
Returns the relief style of @tool_item. See gtk_button_set_relief(). Custom subclasses of #GtkToolItem should call this function in the handler of the #GtkToolItem::toolbar_reconfigured signal to find out the relief style of buttons.
Return: a #GtkReliefStyle indicating the relief style used for @tool_item.