GTK+ "sdl|system" message

[Александър Шопов <ash contact bg>]

There is a message in gtk+ po-file:
#: ../gdk/directfb/gdkdisplay-directfb.c:55
msgid "sdl|system"

Is this a non migrated context, thus I should translate only "system" or
is this the whole message and what does it mean then?

Kind regards:
al_shopov