color_edit_widget->set_has_opacity_control(true);
color_edit_widget->signal_color_changed().connect(sigc::mem_fun(*this,
&studio::Dialog_Color::on_color_changed));
color_edit_widget->set_has_opacity_control(true);
color_edit_widget->signal_color_changed().connect(sigc::mem_fun(*this,
&studio::Dialog_Color::on_color_changed));