GtkNotebook::set_show_border

void set_show_border(bool show_border);

Sets whether or not a beveled edge will be drawn around the notebook pages. If show_border is false the border will not be shown. Setting the border to be shown when the border is already showing or setting it to be hidden when the border is already hidden has no effect. This only has an effect when tabs are not shown.

See also: set_show_tabs()