Adds a style class to widget.
After calling this function, the widget’s style will match for css_class, according to CSS matching rules.
Use gtk.widget.Widget.removeCssClass to remove the style again.
The style class to add to widget, without the leading '.' used for notation of style classes
Adds a style class to widget.
After calling this function, the widget’s style will match for css_class, according to CSS matching rules.
Use gtk.widget.Widget.removeCssClass to remove the style again.