How to get the current column regardless of the content of the current line?

[Rodrigo Morales]

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>