Re: Overlays disappearing during line-by-line scrolling

[Ralf Angeli]

* Kim F. Storm (2005-06-27) writes:

> However, when I try it with the code above, it beeps in line-move-1
> when I move backwards with C-p (for every 4th C-p or so).  This is
> because (one of the instances of) the following code is triggered.
>
>                 (unless noerror
>                   (signal (if (< arg 0)
>                               'beginning-of-buffer
>                             'end-of-buffer)
>                           nil)))
>
> But I don't see how (bobp) would normally return true in the middle of
> a buffer.  Can anybody see why?

AFAICS it's rather the following code which produces the beeps:

                  (and (not done) (not line-done)
                       (zerop (vertical-motion -1))
                       (if (not noerror)
                           (signal 'beginning-of-buffer nil)
                         (setq done t))))

The beeps occur when `C-p' moves over an overlay in the testcase.
When this happens, (vertical-motion -1) returns 0 even though it moves
point up one screen line.  So it could be a problem in
`vertical-motion'.

-- 
Ralf