Re: Problems with whole buffer Custom functions.

["Richard M. Stallman" <rms@gnu.org>]

    Now change the face of `show-paren-match' to "turquoise" and that of
    `show-paren-mismatch' to "purple" and do C-_ twice again.  This time
    both modifications are undone.  Hence whether a modification can be
    undone may depend on whether this or another modification is the first
    editing change for a specific option.

Maybe the undo command needs to specialize to
the changes for the specific item.  Something like undo-in-region.

    The reason for this is that editing also changes some magic text from
    "STANDARD." to "EDITED, shown value does not take effect until you set
    or save it.".  This modification is, however, not recorded in
    `buffer-undo-list' and the buffer position recorded before editing
    started becomes invalid with respect to the actual buffer contents.

I guess the code that does these changes
ought to update the positions in the undo list also.