I am trying to remove the border completely. This is the code I have attempted:
GtkCssProvider *provider = gtk_css_provider_new ();
gtk_css_provider_load_from_data (GTK_CSS_PROVIDER (provider),
"entry, .entry, GtkEntry { border-width:0px ; }",
-1, NULL);
GdkDisplay *display = gdk_display_get_default ();
GdkScreen *screen = gdk_display_get_default_screen (display);
gtk_style_context_add_provider_for_screen (screen, GTK_STYLE_PROVIDER
(provider), GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);