Strangeness with fringe arrows.

[Luc Teirlinck]

I personally enable indicate-empty-lines (to the left) and up and down
arrows to the right (but no top or bottom indicators at all, so they
will not accidentally hide the arrows).  This might seem strange, but
after playing around with this stuff to test my defcustom and other
things, I have gotten convinced that this is the most logical thing to do.

But some strange things happen.  After a while, I get fake extra
arrows which keep hanging around, even after I switch buffers, until I
do C-l.

Do `emacs -q -nbc'.  (The -nbc is probably not necessary, but it is
necessary for me.)

Do:

M-: (setq scroll-conservatively 1000)

M-x customize-group RET fringe

Either do

M-: (setq indicate-buffer-boundaries '((up . left))) 

or:

click on the indicate-buffer-boundaries [Value Menu], select
"Pick your own design" and click on "Up arrow", which enables the up
arrow to the left.  Set for current session.

Overscroll the Custom buffer completely by going to end-of-buffer and
doing M-0 C-l.  Move back using repeated C-p.  When you hit the
beginning of the buffer, you now have an up arrow in the _second_ line.
This "fake" arrow just keeps hanging around, even as you switch
buffers, kill buffers, whatever.  Only C-l and a very few other things
makes it disappear.  If you switch to a buffer that really needs an up
arrow, you get two up arrows.

This procedure only produces fake arrows in certain types of buffers,
like Custom buffers.  I have not the slightest idea what distinguishes
these buffers from other buffers.

Sincerely,

Luc.