unicode-width-workaround: Working around the bad Unicode character widths

In cli: Helpers for Developing Command Line Interfaces

Working around the bad Unicode character widths

Description

R 3.6.2 and also the coming 3.6.3 and 4.0.0 versions use the Unicode 8 standard to calculate the display width of Unicode characters. Unfortunately the widths of most emojis are incorrect in this standard, and width 1 is reported instead of the correct 2 value.

Details

cli implements a workaround for this. The package contains a table that contains all Unicode ranges that have wide characters (display width 2).

On first use of one of the workaround wrappers (in ansi_nchar(), etc.) we check what the current version of R thinks about the width of these characters, and then create a regex that matches the ones that R is wrong about (re_bad_char_width).

Then we use this regex to duplicate all of the problematic characters in the input string to the wrapper function, before calling the real string manipulation function (nchar(), strwrap()) etc. At end we undo the duplication before we return the result.

This workaround is fine for nchar() and strwrap(), and consequently ansi_align() and ansi_strtrim() as well.

The rest of the ⁠ansi_*()⁠ functions work on characters, and do not deal with character width.

cli documentation built on June 22, 2024, 10:57 a.m.