Re: invisible

[Stephen Berman <Stephen.Berman@gmx.net>]

On Sat, 28 Feb 2004 20:24:44 -0600 (CST) Luc Teirlinck
<teirllm@dms.auburn.edu> wrote: 

> ===File ~/invlines==========================================
> line1
> line2
> line3
> line4
> line5
> line6
> line7
> ============================================================
>
> No trailing whitespace but with final newline.
>
> Visit using emacs -q
>
> (put-text-property 6 7 `invisible t)
> (put-text-property 12 13 `invisible t)
> (put-text-property 18 19 `invisible t)
> (put-text-property 24 25 `invisible t)
> (put-text-property 30 31 `invisible t)
>
> Result:
>
> line1line2line3line4line5line6
> line7
>
> line-move-ignore-invisible is now nil.
>
> With point at beginning of buffer keep doing C-n.  Everything goes at
> expected.  We arrive at the end of the buffer, the newline after line7.
>
> C-p beginning of line7. OK.
> C-p beginning of line6.  OK.
> C-p beginning of line4.  Why did we skip line5?
> C-p beginning of line2.  Skipped line3.

This behavior still exists in GNU Emacs 23.0.50.4 (i686-pc-linux-gnu,
GTK+ Version 2.12.0) of 2007-11-09 on escher.[1]  In addition, starting
with the cursor at (point-min), the line number indicator in the mode
line displays L1, and it continues to display L1 as you advance either
by C-n or by C-f until it reaches the `l' of `line7', then it changes to
L7.  From there if you type C-b moving point to just after `6', the mode
line displays L6.  Now continuing backwards either by C-p or C-b the
mode line usually continues to display L6, even at (point-min).  Typing
C-b again here then changes the display to L1.

Steve Berman

Footnotes: 
[1] But the behavior seems to be unstable: sometimes line2 is skipped
advancing by C-n, sometimes line6 is skipped receding by C-p (then the
mode line displays L5 and doesn't change as you continue to
(point-min)).