Re: vertical-motion bug

[Chong Yidong]

Richard Stallman <address@hidden> writes:

>       M-<
>       M-: (insert (propertize "a" 'display "a\nb\nc\n")) RET
>       M-<
>       C-n (or M-: (vertical-motion 1))
>
>     Result: point moves down three lines.  The expected behavior, based on
>     the `vertical-motion' docstring, is to move just one line.
>
> There is no way to move down just one line, since no buffer
> position corresponds to that screen position.  Emacs can either
> move three lines or not move.  So I think its actual behavior
> is the best possible thing it could do.

Sorry, I gave a bad test case.  Try this:

  M-:  (let ((pos (point-min)))
         (dotimes (i 10) (insert "a"))
         (while (< pos (point-max))
           (put-text-property pos (1+ pos) 'display (propertize "a\n"))
           (setq pos (1+ pos))))

This puts a display property on each of the characters in the buffer,
so there is a valid buffer position.  C-n and C-p skip past all of
them.