bug#60048: 30.0.50; Freeze when next-line on details in Completions list

bug#60048: 30.0.50; Freeze when next-line on details in Completions list

[Gabriel]

Description:

Emacs freeze when the command `previous-line-completion' or
`next-line-completion' are executed in Completions list and the cursor
is positioned at some details (the prefix and suffix annotations).  The
steps below `describe-face', but I could reproduce with other details in
Completions list, for example, using `completions-detailed` set to t and
`describe-function'.

Steps:

1) emacs -Q (master "85108d541217f0333860c4f86c3b16b4349f85a4")

2) M-x describe-face

3) Switch to Completions list: M-v (`switch-to-completions')

4) Scroll up: C-v (`scroll-up-command')

5) Go to next completion line: <down> (`next-line-completion')

Result: Emacs freeze (user have to C-g to unfreeze).

The problem is caused by the cursor position, the freeze only happens
when cursor in on SAMPLE.  Can also be reproduced with M-b, which will
move the cursor from the completion line to SAMPLE.  The freeze does not
happen with <left> or <right> commands (`previous-completion' and
`next-completion').

---
Gabriel

bug#60048: 30.0.50; Freeze when next-line on details in Completions list

[Juri Linkov]

> Emacs freeze when the command `previous-line-completion' or
> `next-line-completion' are executed in Completions list and the cursor
> is positioned at some details (the prefix and suffix annotations).

Thanks for the bug report.  When the cursor is on a prefix or a suffix,
where in your opinion typing <down> should go?  Do you expect that
it should search for the completion candidate from the left
or from the right side after moving to the next line if it
can't see the completion candidate already near point?

bug#60048: 30.0.50; Freeze when next-line on details in Completions list

[Gabriel]

Juri Linkov <juri@linkov.net> writes:

>> Emacs freeze when the command `previous-line-completion' or
>> `next-line-completion' are executed in Completions list and the cursor
>> is positioned at some details (the prefix and suffix annotations).
>
> Thanks for the bug report.  When the cursor is on a prefix or a suffix,
> where in your opinion typing <down> should go?  Do you expect that
> it should search for the completion candidate from the left
> or from the right side after moving to the next line if it
> can't see the completion candidate already near point?

Hi Juri,

Regarding your question, if I understood it correctly, I expect <down>
to have the exactly same behavior regardless of the cursor position,
i.e., to move to next completion line, no matter if cursor is on a
prefix, a suffix or on a completion candidate.  The same is true for
<up>.  The <left> and <right> seems to be working as expected.

---
Gabriel

bug#60048: 30.0.50; Freeze when next-line on details in Completions list

[Juri Linkov]

close 60048 29.0.60
thanks

>>> Emacs freeze when the command `previous-line-completion' or
>>> `next-line-completion' are executed in Completions list and the cursor
>>> is positioned at some details (the prefix and suffix annotations).
>>
>> Thanks for the bug report.  When the cursor is on a prefix or a suffix,
>> where in your opinion typing <down> should go?  Do you expect that
>> it should search for the completion candidate from the left
>> or from the right side after moving to the next line if it
>> can't see the completion candidate already near point?
>
> Regarding your question, if I understood it correctly, I expect <down>
> to have the exactly same behavior regardless of the cursor position,
> i.e., to move to next completion line, no matter if cursor is on a
> prefix, a suffix or on a completion candidate.  The same is true for
> <up>.  The <left> and <right> seems to be working as expected.

Thanks, now fixed by removing commands added recently before feature freeze.
They could be re-added later in master.