bug#19553: 25.0.50; vertical-motion returns erroneous positive value

bug#19553: 25.0.50; vertical-motion returns erroneous positive value

[Dmitry Gutov]

1. Create an empty buffer.

2. Create an overlay at the end of it with a tricky after-string:

(setq my-ov (make-overlay (point-max) (point-max) nil t t))
(overlay-put my-ov 'after-string "~\n~\n~")

3. Move point to the end of the buffer (it will be rendered after the
display string; not sure if it's a bug).

4. Evaluate (vertical-motion 1). Point won't move (it has nowhere to
go), but the function call with return 2. Repeat indefinitely.

It's apparently an old bug, but it's been reported in
https://github.com/company-mode/company-mode/issues/274 two days ago,
because it causes an error in company-mode's popup rendering code when
used together with a new-ish package.

(I think I have a workaround, though, if this only happens at eob).

In GNU Emacs 25.0.50.25 (x86_64-unknown-linux-gnu, GTK+ Version 3.12.2)
 of 2015-01-05 on axl
Repository revision: 1ac42bca8886267dac029a2f19df1a43313e0d95
Windowing system distributor `The X.Org Foundation', version 11.0.11601901
System Description:	Ubuntu 14.10

bug#19553: 25.0.50; vertical-motion returns erroneous positive value

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Sat, 10 Jan 2015 09:21:12 +0300
> 
> 1. Create an empty buffer.
> 
> 2. Create an overlay at the end of it with a tricky after-string:
> 
> (setq my-ov (make-overlay (point-max) (point-max) nil t t))
> (overlay-put my-ov 'after-string "~\n~\n~")
> 
> 3. Move point to the end of the buffer (it will be rendered after the
> display string; not sure if it's a bug).
> 
> 4. Evaluate (vertical-motion 1). Point won't move (it has nowhere to
> go), but the function call with return 2. Repeat indefinitely.
> 
> It's apparently an old bug, but it's been reported in
> https://github.com/company-mode/company-mode/issues/274 two days ago,
> because it causes an error in company-mode's popup rendering code when
> used together with a new-ish package.

Fixed in commit b544ab5 on the emacs-24 branch.

Thanks.

bug#19553: 25.0.50; vertical-motion returns erroneous positive value

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Sat, 10 Jan 2015 09:21:12 +0300
> 
> 1. Create an empty buffer.
> 
> 2. Create an overlay at the end of it with a tricky after-string:
> 
> (setq my-ov (make-overlay (point-max) (point-max) nil t t))
> (overlay-put my-ov 'after-string "~\n~\n~")
> 
> 3. Move point to the end of the buffer (it will be rendered after the
> display string; not sure if it's a bug).

Sorry, forgot to answer that question: no, it's not a bug.  We always
display the cursor _after_ overlay strings.

bug#19553: 25.0.50; vertical-motion returns erroneous positive value

[Dmitry Gutov]

Version: 24.5

On 01/10/2015 04:06 PM, Eli Zaretskii wrote:

> Fixed in commit b544ab5 on the emacs-24 branch.

Thanks!

bug#19553: 25.0.50; vertical-motion returns erroneous positive value

[Stefan Monnier]

> Sorry, forgot to answer that question: no, it's not a bug.  We always
> display the cursor _after_ overlay strings.

"Always" of course can be overruled using the `cursor' text-property on
the after-string.


        Stefan