How to style GtkButton with CSS

1. create
2. create the
3. create
4. load css data with
5. create
GtkBoxto add widgets to window;
2. create the
GtkButtonand add to the layout box with
GtkBox::pack_start;
3. create
GtkCssProvider;
4. load css data with
GtkCssProvider::load_from_data;
5. create
GtkStyleContextand add provider to the screen, to css be accessible for all widgets;