This function attaches the widget’s gtk.Style to the widget's gdk.Window It is a replacement for

|[ widget->style = gtk_style_attach (widget->style, widget->window);

and should only ever be called in a derived widget’s “realize”
implementation which does not chain up to its parent class'
“realize” implementation, because one of the parent classes
(finally [gtk.Widget.Widget|gtk.Widget]) would attach the style itself.

Deprecated: This step is unnecessary with [gtk.StyleContext.StyleContext|gtk.StyleContext]

Since: 2.20
class Widget