Gtk.Gradient
GtkGradient is a boxed type that represents a gradient. It is the result of parsing a <link linkend="gtkcssprovider-gradients">gradient expression</link>. To obtain the gradient represented by a GtkGradient, it has to be resolved with Gtk.resolve, which replaces all symbolic color references by the colors they refer to (in a given context) and constructs a #cairo_pattern_t value.
It is not normally necessary to deal directly with #GtkGradients, since they are mostly used behind the scenes by Gtk.StyleContext and Gtk.CssProvider.
Gtk.Gradient is deprecated. It was used internally by GTK's CSS engine to represent gradients. As its handling is not conforming to modern web standards, it is not used anymore. If you want to use gradients in your own code, please use Cairo directly.