Widgets can add style classes to their context, which can be used to associate
different styles by class. The documentation for individual widgets lists
which style classes it uses itself, and which style classes may be added by
applications to affect their appearance.
Custom styling in UI libraries and applications
If you are developing a library with custom widgets that render differently
than standard components, you may need to add a gtk.style_provider.StyleProvider yourself
with the GTK_STYLE_PROVIDER_PRIORITY_FALLBACK priority, either a
gtk.css_provider.CssProvider or a custom object implementing the gtk.style_provider.StyleProvider
interface. This way themes may still attempt to style your UI elements in
a different way if needed so.
If you are using custom styling on an applications, you probably want then
to make your style information prevail to the theme’s, so you must use
a gtk.style_provider.StyleProvider with the GTK_STYLE_PROVIDER_PRIORITY_APPLICATION
priority, keep in mind that the user settings in
XDG_CONFIG_HOME/gtk-4.0/gtk.css will
still take precedence over your changes, as it uses the
GTK_STYLE_PROVIDER_PRIORITY_USER priority.
Deprecated: The relevant API has been moved to gtk.widget.Widget
where applicable; otherwise, there is no replacement for querying the
style machinery. Stylable UI elements should use widgets.
gtk.style_context.StyleContext stores styling information affecting a widget.
In order to construct the final style information, gtk.style_context.StyleContext queries information from all attached GtkStyleProviders. Style providers can be either attached explicitly to the context through gtk.style_context.StyleContext.addProvider, or to the display through gtk.style_context.StyleContext.addProviderForDisplay. The resulting style is a combination of all providers’ information in priority order.
For GTK widgets, any gtk.style_context.StyleContext returned by gtk.widget.Widget.getStyleContext will already have a gdk.display.Display and RTL/LTR information set. The style context will also be updated automatically if any of these settings change on the widget.
Style Classes
Widgets can add style classes to their context, which can be used to associate different styles by class. The documentation for individual widgets lists which style classes it uses itself, and which style classes may be added by applications to affect their appearance.
Custom styling in UI libraries and applications
If you are developing a library with custom widgets that render differently than standard components, you may need to add a gtk.style_provider.StyleProvider yourself with the GTK_STYLE_PROVIDER_PRIORITY_FALLBACK priority, either a gtk.css_provider.CssProvider or a custom object implementing the gtk.style_provider.StyleProvider interface. This way themes may still attempt to style your UI elements in a different way if needed so.
If you are using custom styling on an applications, you probably want then to make your style information prevail to the theme’s, so you must use a gtk.style_provider.StyleProvider with the GTK_STYLE_PROVIDER_PRIORITY_APPLICATION priority, keep in mind that the user settings in XDG_CONFIG_HOME/gtk-4.0/gtk.css will still take precedence over your changes, as it uses the GTK_STYLE_PROVIDER_PRIORITY_USER priority.