In addition, certain files will be read when GTK is initialized.
First, the file $XDG_CONFIG_HOME/gtk-4.0/gtk.css is loaded if it
exists. Then, GTK loads the first existing file among
XDG_DATA_HOME/themes/THEME/gtk-VERSION/gtk-VARIANT.css,
$HOME/.themes/THEME/gtk-VERSION/gtk-VARIANT.css,
$XDG_DATA_DIRS/themes/THEME/gtk-VERSION/gtk-VARIANT.css and
DATADIR/share/themes/THEME/gtk-VERSION/gtk-VARIANT.css,
where THEME is the name of the current theme (see the
property@Gtk.Settings:gtk-theme-name setting), VARIANT is the
variant to load (see the
property@Gtk.Settings:gtk-application-prefer-dark-theme setting),
DATADIR is the prefix configured when GTK was compiled (unless
overridden by the GTK_DATA_PREFIX environment variable), and
VERSION is the GTK version number. If no file is found for the
current version, GTK tries older versions all the way back to 4.0.
To track errors while loading CSS, connect to the
signal@Gtk.CssProvider::parsing-error signal.
gtk.css_provider.CssProvider is an object implementing the gtk.style_provider.StyleProvider interface for CSS.
It is able to parse CSS-like input in order to style widgets.
An application can make GTK parse a specific CSS style sheet by calling gtk.css_provider.CssProvider.loadFromFile or gtk.css_provider.CssProvider.loadFromResource
and adding the provider with gtk.style_context.StyleContext.addProvider or gtk.style_context.StyleContext.addProviderForDisplay.
In addition, certain files will be read when GTK is initialized. First, the file $XDG_CONFIG_HOME/gtk-4.0/gtk.css is loaded if it exists. Then, GTK loads the first existing file among XDG_DATA_HOME/themes/THEME/gtk-VERSION/gtk-VARIANT.css, $HOME/.themes/THEME/gtk-VERSION/gtk-VARIANT.css, $XDG_DATA_DIRS/themes/THEME/gtk-VERSION/gtk-VARIANT.css and DATADIR/share/themes/THEME/gtk-VERSION/gtk-VARIANT.css, where THEME is the name of the current theme (see the property@Gtk.Settings:gtk-theme-name setting), VARIANT is the variant to load (see the property@Gtk.Settings:gtk-application-prefer-dark-theme setting), DATADIR is the prefix configured when GTK was compiled (unless overridden by the GTK_DATA_PREFIX environment variable), and VERSION is the GTK version number. If no file is found for the current version, GTK tries older versions all the way back to 4.0.
To track errors while loading CSS, connect to the signal@Gtk.CssProvider::parsing-error signal.