How do I know if my patch got applied, and if not, why not?

Uploaded patches will be moved to ftp://ftp.gtk.org/pub/gtk/patches where one of the GTK+ development team will pick them up. If applied, they will be moved to /pub/gtk/patches/old.

Patches that aren't applied, for whatever reason, are moved to /pub/gtk/patches/unapplied or /pub/gtk/patches/outdated. At this point you can ask on the gtk-list mailing list why your patch wasn't applied. There are many possible reasons why patches may not be applied, ranging from it doesn't apply cleanly, to it isn't right. Don't be put off if your patch didn't make it first time round.