Stephen J. Turnbull writes:
If you are communicating by cut and paste with applications that use
primary selection, then you can customize `interprogram-cut-function' to
nil, restoring the XEmacs version 20 behavior. How can you tell if a
program will support this? Motifly-correct programs require the
clipboard; you lose. For others, only by trying it. You usually don't
need to customize the complementary `interprogram-paste-function' to
nil; presumably you're willing to wait for a paste from another program
if delays only happen when you specifically request a paste.
I tried setting interprogram-cut-function to nil and leaving
interprogram-past-function alone, but that breaks C-y. XEmacs
signals "no selection: CLIPBOARD" and doesn't yank any text.
So this doc should be changed to recommend setting both variables
to nil. Tested against 21.4.8 and the latest 21.5 snapshot.