Unicode characters in mathed

[Scott Kostyshak]

On Sat, Apr 01, 2023 at 03:09:58PM +0200, Jean-Marc Lasgouttes wrote:
> Hello,
> 
> A relative has been using LyX recently, and it is interesting to see how the
> use is different from what I would do.
> 
> In particular, instead of typing \neq in mathed, why not copy and paste a ≠
> from some PDF or HTML page?
> 
> When doing this, two things happen :
> 1/ on screen, there is no spacing around the ≠
> 2/ in LaTeX output, the character is exported as \neq and all is well
> 
> So how should I solve problem 1/ ? I see 3 solutions
> a/ replace ≠ with a \neq directly in the document at input time; we might
> not want to do that in case we eventually use unicode in math too
> b/ replace ≠ with a \neq on screen only
> c/ keep the ≠ on screen, but use the mathrel math class from \neq so that we
> have a good spacing
> 
> Then, I see that there are two ways of matching \neq to U+2260:
> i/ lib/unicodesymbol has a "mathcommand" entry for that (which is presumably
> used right now)
> ii/ lib/symbols also links these elements
> 
> Which one is more reliable for what I want to do?
> 
> My general problem is that, while I see what happens with \neq, I suspect
> that many weird things can happen with other characters.
> 
> Any advice?

Would another possibility be to prompt the user? I'm not sure what a friendly prompt would be though since many LyX users do not know what unicode is. I could try to work on some user-friendly text if we think a prompt would be reasonable. A prompt would be my ideal behavior though since I often paste unicode by mistake. This type of thing hits me from time to time, not with symbols that are obviously non-ascii like ≠ but more with double-quotes or things like that that I forget are often non-ascii.

If we do preserve the unicode ≠, I would personally prefer to have some sort of signal that it is unicode in the LyX display. Actually, that's how I have my text editor set up (see screenshot).

All that said, I understand that my personal preferences might not be best for the default behavior of LyX.

Scott
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