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From: Rodrigo Morales <moralesrodrigo1100@gmail.com>
To: help-gnu-emacs@gnu.org
Subject: How to get the current column regardless of the content of the current line?
Date: Thu, 15 Dec 2022 14:22:49 -0500	[thread overview]
Message-ID: <CAGxMbPY=sAFf3cOiwzSDr0Cw3M-MBF=bzzKCZs0CoGsFfLvQsw@mail.gmail.com> (raw)

Table of Contents
_________________

1. The context
2. The question
3. The current workaround
4. Additional information

1 The context
=============

  I'm aware that `current-column' returns the column of the cursor
  position. See two minimal working examples below.

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

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

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

  ,----
  | 6
  `----

  Sometimes, `current-column' considers one character as if it were
  two. In the minimal working example below, you can see that the line
  contains `你' (U+4F60) 3 times and `current-column' returns 6 when it
  is at the end of the line.

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

  ,----
  | 6
  `----

  In the minimal working example below, you can see that even though the
  line contains two characters, `current-column' returns `3'. This
  happens because, as shown in the previous example, `你' is counted as
  two characters by `current-column'.

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

  ,----
  | 3
  `----


2 The question
==============

  Which function could I use to obtain the column of the current
  position that would work for any line regardless of its content?


3 The current workaround
========================

  I have written the following function to get the results that I
  expect. However, I decided to open this thread just in case there's
  another (preferably, shorter or built-in) function that any of you
  might know.

  ,----
  | (defun my/current-column ()
  |   (save-excursion
  |     ;; Save the current point
  |     (let ((orig (point))
  |           (counter 0))
  |       (beginning-of-line)
  |       ;; Count the number of characters from the beginning of the line
  |       ;; to the previously stored point
  |       (while (and (<= (point) orig)
  |                   (not (eobp)))
  |         (setq counter (1+ counter))
  |         (forward-char))
  |       counter)))
  `----

  The following code blocks contains minimal working examples that show
  the results of this function.

  ,----
  | (with-temp-buffer
  |   (insert "你你你")
  |   (my/current-column))
  `----

  ,----
  | 3
  `----

  ,----
  | (with-temp-buffer
  |   (insert "a你")
  |   (my/current-column))
  `----

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


4 Additional information
========================

  I opened a thread in the bug-gnu-emacs mailing list, because I thought
  that there was a bug in `current-column', and Eli Zaretskii explained
  some details of this function. You can find the thread in this link at
  the archives:
  <https://lists.gnu.org/archive/html/bug-gnu-emacs/2022-12/msg01524.html>


             reply	other threads:[~2022-12-15 19:22 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-15 19:22 Rodrigo Morales [this message]
2022-12-15 21:37 ` How to get the current column regardless of the content of the current line? Gregory Heytings
2022-12-15 21:41   ` Gregory Heytings
2022-12-15 21:56     ` Stefan Monnier via Users list for the GNU Emacs text editor
2022-12-15 22:00       ` Emanuel Berg
2022-12-15 22:02       ` Gregory Heytings
2022-12-16  7:10         ` Eli Zaretskii
2022-12-16  8:52           ` Gregory Heytings
2022-12-16 21:43             ` Emanuel Berg
2022-12-16  3:28     ` Rodrigo Morales
2022-12-16  5:12 ` Jean Louis
2022-12-16 17:44   ` Rodrigo Morales
2022-12-17  4:07     ` Jean Louis
2022-12-17  5:11       ` Emanuel Berg
2022-12-17  5:53         ` Emanuel Berg

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