This makes it easier to implement the theme switching
in widget-factory, since we don't have a variant setting.
xml += '''
<file>theme/Empty/gtk.css</file>
+
<file>theme/Default/gtk.css</file>
+ <file alias='theme/Default-dark/gtk.css'>theme/Default/gtk-dark.css</file>
+ <file alias='theme/Default-hc/gtk.css'>theme/Default/gtk-hc.css</file>
+ <file alias='theme/Default-hc-dark/gtk.css'>theme/Default/gtk-hc-dark.css</file>
+
<file>theme/Default/gtk-light.css</file>
<file>theme/Default/gtk-dark.css</file>
<file>theme/Default/gtk-hc.css</file>