Should `\boldsymbol` be the style for bold italic?

[cesaryuan]

Hi, guys!

I would like to discuss with you the style issue of the \boldsymbol command.

Why is the command \boldsymbol considered EStyled TextBold instead of EStyled TextBoldItalic? The effect shown in this post https://tex.stackexchange.com/a/99286 suggests that \boldsymbol should have a completely different effect from \mathbf. However, in the HTML generated by pandoc, they appear the same. I personally believe that TextBoldItalic would be a more appropriate representation. If possible, I would be happy to submit a PR to change this. But I would like to discuss this with everyone.

texmath/src/Text/TeXMath/Readers/TeX/Commands.hs

Lines 45 to 50 in aee6b49

	, ("\\boldsymbol", EStyled TextBold)
	, ("\\bm", EStyled TextBold)
	, ("\\symbf", EStyled TextBold)
	, ("\\mathbold", EStyled TextBold)
	, ("\\pmb", EStyled TextBold)
	, ("\\mathbfup", EStyled TextBold)

texmath/src/Text/TeXMath/Readers/TeX/Commands.hs

Line 61 in aee6b49

, ("\\mathbfit", EStyled TextBoldItalic)

[jgm]

No, I don't think so. You can see that \boldsymbol behaves the same as \bm, and in both cases the capital Gamma is upright, not italic. b is italic, but that's just how it would render outside of \boldsymbol.

[cesaryuan]

What you said has some merit, but if we look at the HTML and Docs generated by converting the table in this figure using pandoc, we find there are significant differences from the figure.

[cesaryuan]

I created a PR #281 to apply different styles based on different characters.

Frankly, I'm not a user of programming languages like Haskell, so I'm not sure if the syntax style written here is correct, but I still wanted to provide a reference for everyone.

This is the effect of applying the modified texmath:

[jgm]

You are looking at HTML and Docx produced by pandoc. Is the figure image above from docx? For HTML, are you using MathJax or what method to render the math?

This could be an omml rendering issue; perhaps there's something we need to do to ensure that identifiers within a boldfaced section continue to be rendered in italics.

But I would think that MathJax ought to render things like TeX.

[cesaryuan]

But I would think that MathJax ought to render things like TeX

I looked at the source code of MathJax. They seem to be similar to the processing here in #281. They should apply different MathVariants according to different characters.

https://github.com/mathjax/MathJax-src/blob/27f3759ca09406cf939101e1c3127165bf2e1f6a/ts/input/tex/boldsymbol/BoldsymbolConfiguration.ts#L35-L43

This could be an omml rendering issue; perhaps there's something we need to do to ensure that identifiers within a boldfaced section continue to be rendered in italics.

I tend to think it is a parsing problem, because there is a difference between the MathML output by MathJax and the MathML output by Pandoc.

Docx (before apply PR #281)

Docx (after apply PR #281)

HTML mathml (before apply PR #281)

HTML mathml (after apply PR #281)

[jgm]

Can you display the difference in the MathJax-generated MathML vs pandoc-generated? (Not a picture, but the actual MathML XML code.)

[cesaryuan]

Can you display the difference in the MathJax-generated MathML vs pandoc-generated? (Not a picture, but the actual MathML XML code.)

MathJax-generated MathML

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi mathvariant="bold-italic">𝛼</mi>
    <mo mathvariant="bold">+</mo>
    <mi mathvariant="bold-italic">𝑏</mi>
  </mrow>
  <mo mathvariant="bold">=</mo>
  <mrow>
    <mi mathvariant="bold">Γ</mi>
    <mo mathvariant="bold">÷</mo>
    <mi mathvariant="bold-italic">𝐷</mi>
  </mrow>
</math>  

pandoc-generated

<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mi>𝛂</mi>
    <mo mathvariant="bold">+</mo>
    <mi>𝐛</mi>
    <mo mathvariant="bold">=</mo>
    <mi>𝚪</mi>
    <mo mathvariant="bold">÷</mo>
    <mi>𝐃</mi>
  </mrow>
</math>

[jgm]

Ah, now I see that this relates to our use of boldface unicode symbols.

This was originally introduced in 2012, because at the time anyway, few renderers could handle the mathvariant attribute. (I assume that has changed?)

See commit 3c746ad

The commit comment ends: "For MathML output, this should eventually become optional, or removed completely." And maybe this is that time. 2012 was a long time ago.

Also relevant: #205, which removed the mathvariant attributes we used to have.

[cesaryuan]

@jgm Thank you very much for your efforts!

However, I noticed that your changes seem to only be effective for MathML and not for the OMML writer. Can you reopen this issue?

E:/desktop/texmath $ echo '\boldsymbol{b}' | ".stack-work/install/68ece1cb/bin/texmath.exe" -f tex -t omml
<m:oMathPara>
  <m:oMathParaPr>
    <m:jc m:val="center" />
  </m:oMathParaPr>
  <m:oMath>
    <m:r>
      <m:rPr>
        <m:sty m:val="b" />
      </m:rPr>
      <m:t>b</m:t>
    </m:r>
  </m:oMath>
</m:oMathPara>

[jgm]

docx old:

docx new:

html + mathml old (safari):

html + mathml new:

[jgm]

Looks like we still need some work on the omml (docx) renderer side.

\boldmath was never supported, so I'm ignoring that.

Also, there is an odd difference between \mathbf and \boldsymbol; the former doesn't boldface alpha and makes letters upright. We don't currently respect that difference.

I'll reopen because of these remaining issues.