GNU bug report logs - #60094
current-column returns an incorrect number of columns for some characters

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Stefan Kangas <stefankangas <at> gmail.com>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#60094: closed (current-column returns an incorrect number of
 columns for some characters)
Date: Mon, 04 Sep 2023 21:12:02 +0000

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Your message dated Mon, 4 Sep 2023 14:11:42 -0700
with message-id <CADwFkmndDTDDO0wVTht_q7vXgvAkVqiE_5r9aNL2aRH7RL28XQ <at> mail.gmail.com>
and subject line Re: bug#60094: current-column returns an incorrect number of columns for some characters
has caused the debbugs.gnu.org bug report #60094,
regarding current-column returns an incorrect number of columns for some characters
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
60094: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=60094
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Contact help-debbugs <at> gnu.org with problems

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From: Rodrigo Morales <moralesrodrigo1100 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: current-column returns an incorrect number of columns for some
 characters
Date: Thu, 15 Dec 2022 11:40:55 -0500

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TL; DR: `current-column' returns `2' when the cursor is in the first
column and the line contains a single emoji or a Chinese character. The
expected value is `1' as happens when the line contains `a' or even the
highest defined codepoint in Unicode: `U+10FFFD'.

In the minimal working example below, you can see that `current-columns'
returns `1' when the line contains the character `a' and the cursor is
located after it.

,----
| cat ~/e/main.el
`----

,----
| (with-temp-buffer
|   (insert "a")
|   (end-of-line)
|   (princ (current-column)))
`----

,----
| emacs -Q --batch -l ~/e/main.el
`----

,----
| 1
`----

In the minimal working example below, you can see that `current-columns'
returns `1' when the line contains the character `􏿽' (highest defined
codepoint in Unicode, U+10FFFD) and the cursor is located after it.

,----
| cat ~/e/main.el
`----

,----
| (with-temp-buffer
|   (insert "􏿽")
|   (end-of-line)
|   (princ (current-column)))
`----

,----
| emacs -Q --batch -l ~/e/main.el
`----

,----
| 1
`----

In the minimal working example below, you can see that `current-columns'
returns `2' when the line contains an emoji and the cursor is located
after it.

,----
| cat ~/e/main.el
`----

,----
| (with-temp-buffer
|   (insert "👋")
|   (end-of-line)
|   (princ (current-column)))
`----

,----
| emacs -Q --batch -l ~/e/main.el
`----

,----
| 2
`----

In the minimal working example below, you can see that `current-columns'
returns `2' when the line contains a Chinese character and the cursor is
located after it.

,----
| cat ~/e/main.el
`----

,----
| (with-temp-buffer
|   (insert "你")
|   (end-of-line)
|   (princ (current-column)))
`----

,----
| emacs -Q --batch -l ~/e/main.el
`----

,----
| 2
`----

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From: Stefan Kangas <stefankangas <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 60094-done <at> debbugs.gnu.org, Rodrigo Morales <moralesrodrigo1100 <at> gmail.com>
Subject: Re: bug#60094: current-column returns an incorrect number of columns
 for some characters
Date: Mon, 4 Sep 2023 14:11:42 -0700

Eli Zaretskii <eliz <at> gnu.org> writes:

> tags 60094 notabug
> thanks
[...]
> So there's no bug here: Emacs does what it's supposed to do.  The doc
> string of current-column says:
>
>   This is calculated by adding together the widths of all the displayed
>   representations of the character between the start of the previous line
>   and point (e.g., control characters will have a width of 2 or 4, tabs
>   will have a variable width).
>
> Note the "displayed representations" part.

Thanks, I'm therefore closing this bug report.

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