Use GtkStateFlags instead of sealed GtkButton fields
Use GtkStateFlags instead of sealed GtkButton fields

GTK_STATE_FLAG_ACTIVE means that the button is pressed, and
GTK_STATE_FLAG_PRELIGHT that pointer is over it.

https://bugzilla.gnome.org/show_bug.cgi?id=627455

GNOME/gnome-panel,GNOME/gnome-panel