epg-context-set-progress-callback
epg-context-set-progress-callback is a compiled Lisp function in `epg.el
'.
(epg-context-set-progress-callback CONTEXT PROGRESS-CALLBACK)
Set the function which handles progress update.
PROGRESS-CALLBACK is either a function, or a cons-cell whose
car is a function and cdr is a callback data.
The function gets six arguments: the context, the operation
description, the character to display a progress unit, the
current amount done, the total amount to be done, and the
callback data (if any).