Commit: runtime(doc): make :h virtcol() more accurate

[Christian Brabandt]

runtime(doc): make :h virtcol() more accurate

Commit: https://github.com/vim/vim/commit/014c731fa50c28c94d56545938b6a05a86234c30
Author: zeertzjq <zeer...@outlook.com>
Date: Wed Oct 1 18:30:38 2025 +0000

runtime(doc): make :h virtcol() more accurate

The current description (especially the "unlimited width" part) is
inaccurate in several ways:
- The size of virtual text can depend on window width. In particular,
the size of "above" virtual text can be equal to window width.
- A double-width character that doesn't fit adds 1 to the virtual column
of the following characters.
- The size of 'showbreak' and 'breakindent' is counted.

related: #5713
closes: #18447

Signed-off-by: zeertzjq <zeer...@outlook.com>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 13e73add6..46450685a 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1,4 +1,4 @@
-*builtin.txt* For Vim version 9.1. Last change: 2025 Sep 29
+*builtin.txt* For Vim version 9.1. Last change: 2025 Oct 01


VIM REFERENCE MANUAL by Bram Moolenaar
@@ -12346,9 +12346,9 @@ values({dict}) *values()*

virtcol({expr} [, {list} [, {winid}]]) *virtcol()*
The result is a Number, which is the screen column of the file
- position given with {expr}. That is, the last screen position
- occupied by the character at that position, when the screen
- would be of unlimited width. When there is a <Tab> at the
+ position given with {expr}. That is, the total number of
+ screen cells occupied by the part of the line until the end of
+ the character at that position. When there is a <Tab> at the
position, the returned Number will be the column at the end of
the <Tab>. For example, for a <Tab> in column 1, with 'ts'
set to 8, it returns 8. |conceal| is ignored.