The documentation said that you should return TRUE to mark that the action was handled, but the code did the reverse. Change the documentation to reflect what all the other gestures do. https://bugzilla.gnome.org/show_bug.cgi?id=689061
The parameter is now used to index the touch/mouse pointer tracked in the gesture array, rename accordingly and update the docs.
https://bugzilla.gnome.org/show_bug.cgi?id=678427