About effective text length measuring for PowerShell

[lewis-yeung]

The current (*color.Ansi).MeasureText method uses utf8.RuneCountInString to measure the effective text length, it calculates in unit of Unicode characters instead of cells on terminal screen, which will cause tooltips or any right-aligned segments in PowerShell to be displayed incorrectly (typically a line break) when the text includes wide characters (e.g., CJK characters) or something like backspaces (mostly act as part of a trick to tweak the rendering results). See the screenshot below:

Should we find a better way to handle this?

[JanDeDobbeleer]

Up for a good suggestion. It's a tricky thing and requires skills/knowledge I don't possess yet. Might need to have a read about the topic.

[lewis-yeung]

Yeah, that needs hard work but is worth trying. Besides, to find a proper solution can involve several topics: character width difference between specific fonts, the way the console/terminal handles tabs (\t), emoji rendering width, etc. Now I'm trying to dive into it. 😆

[JanDeDobbeleer]

@lewis-yeung keep me in the loop. It's been on my list for quite a while 😃

[lewis-yeung]

Ah oh, sorry that I forgot the prerequisite "in PowerShell". As we know, zsh has a native right prompt support ($RPROMPT) so OMP doesn't have to deal with this case for a tooltip. Maybe we can find out how zsh implements it exactly and try to make an implementation in Go or PowerShell.

[JanDeDobbeleer]

@lewis-yeung that's shell functionality, not something we need to do. PSReadLine is who you need to talk to for that one.

[lewis-yeung]

Aha, you are quite right! I almost forgot that it would make things more and more hacky. 😆

[lewis-yeung]

@JanDeDobbeleer Now I come back to this topic again. I just found that go-runewidth handles most of the wide characters (especially CJK) properly. Although this is not an absolute perfect solution (e.g., the width of a flag emoji cannot be measured correctly for the time being), it does much better than utf8.RuneCountInString. I'm ready to submit a PR.

[JanDeDobbeleer]

@lewis-yeung that would be perfect! That way I don't have to implement custom logic for it.