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: Rodrigo Morales <moralesrodrigo1100 <at> gmail.com>
Subject: bug#60094: closed (Re: bug#60094: 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 bug report

#60094: current-column returns an incorrect number of columns for some characters

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 60094 <at> debbugs.gnu.org.

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

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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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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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