Fix `\mathit` font and italic correction and add `\mathnormal` #1700

ylemkimon · 2018-09-05T09:04:27Z

Fixes #584 and fixes #1250.

KaTeX uses the same font (Math-Italic, Computer Modern Math Italic[cmmi], class mathit for alphabets and Main-Regular, Computer Modern Roman[cmr] for digits) for math atoms outside font commands (default) and in \mathit.

However, \mathit in LaTeX uses text italic font (Main-Italic, Computer Modern Text Italic[cmti], class mainit) for both alphabets and digits, which has narrow widths (spacing) and no italic correction, same as \textit. This PR changes \mathit font to Main-Italic and remove its italic correction. (0d52009) This also fixes old font command \it, as it uses mathit class.

\DeclareMathAlphabet{\mathit}{OT1}{cmr}{m}{it}

(Green is LaTeX, red is KaTeX, aligned manually. The spacing around accent character seems to be still wrong but is in the right direction, I'll open an issue after this is merged. Wrong accent position is tracked by #1099, incorrect spacing around dotless i by #354, and \KaTeX mismatch by #1703)

Also, I've renamed the name mathit to mathdefault and mainit to mathit to avoid confusion. (f354da8) We should consider changing the font name.

Furthermore, I've added \mathnormal, which is similar to default math font but uses old style (Caligraphic) font for digits and math italic (Math-Italic) font for uppercase Greek alphabets as well as other letters that is in math italic font. (702c454)

(Green is LaTeX, red is KaTeX, incorrect spacing around dotless i is tracked by #354 and \KaTeX mismatch by #1703)

codecov · 2018-09-05T15:49:10Z

Codecov Report

Merging #1700 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1700      +/-   ##
==========================================
+ Coverage   93.88%   93.89%   +<.01%     
==========================================
  Files          78       78              
  Lines        4564     4569       +5     
  Branches      802      805       +3     
==========================================
+ Hits         4285     4290       +5     
  Misses        246      246              
  Partials       33       33

Flag	Coverage Δ
#screenshotter	`88.76% <100%> (+0.01%)`	⬆️
#test	`85.24% <56.25%> (-0.08%)`	⬇️

Impacted Files	Coverage Δ
src/wide-character.js	`72.22% <ø> (ø)`	⬆️
src/functions/font.js	`95.83% <ø> (ø)`	⬆️
src/buildCommon.js	`98.44% <100%> (+0.03%)`	⬆️
src/buildMathML.js	`98.73% <100%> (ø)`	⬆️

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ylemkimon · 2018-09-06T13:10:42Z

src/buildMathML.js

@@ -85,7 +85,7 @@ export const getVariant = function(
    }

    const font = options.font;
-    if (!font) {
+    if (!font || font === "mathnormal") {


I'm not sure what variant \mathnormal should use, but as it acts similar to the default math font, I used null (none).

That should be fine.

kevinbarabash · 2018-09-22T23:15:03Z

src/buildCommon.js

            fontName = fontData.fontName;
            fontClasses = [fontData.fontClass];
+        } else if (utils.contains(mathitLetters, text)) {
+            fontName = "Main-Italic";
+            fontClasses = ["mathit"];


This feels redundant. Shouldn't the mathdefault call below take care of this case?

kevinbarabash · 2018-09-22T23:15:11Z

src/buildCommon.js

@@ -72,7 +72,7 @@ const makeSymbol = function(
    let symbolNode;
    if (metrics) {
        let italic = metrics.italic;
-        if (mode === "text") {
+        if (mode === "text" || (options && options.font === "mathit")) {
            italic = 0;


Interesting. The combining of text glyphs we do should have a similar affect, shouldn't it. I guess it still keeps the italic value from the last glyph so it still changing the spacing at the boundaries between font types whereas this won't.

@kevinbarabash Should we remove mode === "text"?

Would this change affect the screenshots? I'm not exactly sure where we use .italic, as we don't support \/ (but maybe we should). We probably use it in accent placement, so removing mode === "text" might improve (or worsen) accents.

Not sure, but it's something we could investigate.

kevinbarabash · 2018-09-22T23:16:05Z

src/buildCommon.js

            fontClass: "mathit",
        };
+    } else if (/[0-9]/.test(value.charAt(0))) {


It'd be nice to have some helper functions for some of these tests, maybe isLatinLetter, isNumber, etc.

Even better (faster) would be to use hasOwnProperty on an object with the appropriate keys. We should replace all/most uses of utils.contains with this. But not necessarily for this PR.

That's clever. We'd want to construct the object programmatically at load time though.

kevinbarabash · 2018-09-22T23:17:06Z

src/buildCommon.js

@@ -705,11 +734,17 @@ const fontMap: {[string]: {| variant: FontVariant, fontName: string |}} = {
        variant: "italic",
        fontName: "Main-Italic",
    },
+    "mathit": {
+        variant: "italic",
+        fontName: "Main-Italic",


What were you thinking in terms of renaming fonts?

kevinbarabash

LGTM. Thanks for the PR.

edemaine · 2018-10-02T14:18:24Z

docs/supported.md

+|$\text{Ab0}$ `\text{Ab0}`      |$\bm{Ab}$ `\bm{Ab}`            |$\frak{Ab0}$ `\frak{Ab0}`
+|$\mathsf{Ab0}$ `\mathsf{Ab0}`  |$\mathtt{Ab0}$ `\mathtt{Ab0}`  |$\mathfrak{Ab0}$ `\mathfrak{Ab0}`
+|$\textsf{Ab0}$ `\textsf{Ab0}`  |$\texttt{Ab0}$ `\texttt{Ab0}`  |$\mathcal{AB0}$ `\mathcal{AB0}`
+|$\sf Ab0$ `\sf Ab0`            |$\tt Ab0$ `\tt Ab0`            |$\mathscr{AB}$ `\mathscr{AB}`


Any guesses why I'm not seeing these changes on https://deploy-preview-1700--katex.netlify.com/docs/supported.html ? Is there something wrong with our Netlify builds?

@edemaine It's because versioned docs are not updated. You can check them in https://deploy-preview-1700--katex.netlify.com/docs/next/supported.html.

Of course! Thanks.

Now I see a bug, though: the 0 in \mathnormal his rendering in the incorrect font.

According to inspect, it's rendering with the HTML <span class="mord mathcal">0</span> whereas the letters are rendering as e.g. <span class="mord mathdefault">A</span>.

Oops, I guess that's exactly what LaTeX does. Sorry, \mathnormal does not do what I thought it did!

\mathnormal{Ab0}\mathit{Ab0}

~~I do get the feeling that there's too much space after the A in all other KaTeX examples (\mathit, \mathrm, \textrm, \mathbf, ...) though...~~

Comparing more with LaTeX, everything seems like a good match. Which your texcmp outputs confirm. 😄

I do remain confused about what the initial/default mode of LaTeX is. I thought it was \mathnormal, but that differs on numerals. Is there a name for it?

\mathdefault? I don't even though if that's a thing or not, but there must be some way of getting back to that mode from inside of \mathnormal.

ylemkimon · 2018-10-10T07:54:06Z

I'll merge this PR, as I'm planning to completely refactor font generation and selection.

kevinbarabash · 2018-10-13T01:51:51Z

@ylemkimon what kinds of changes are you planning?

Refer to KaTeX/KaTeX#1700 for additional details.

ylemkimon requested a review from edemaine September 5, 2018 09:04

ylemkimon changed the title ~~Fix \mathit spacing (italic correction)~~ [WIP] Fix \mathit spacing (italic correction) Sep 5, 2018

ylemkimon removed the request for review from edemaine September 5, 2018 14:28

ylemkimon closed this Sep 5, 2018

ylemkimon reopened this Sep 5, 2018

ylemkimon requested a review from edemaine September 5, 2018 15:50

ylemkimon changed the title ~~[WIP] Fix \mathit spacing (italic correction)~~ Fix \mathit spacing and italic correction Sep 6, 2018

ylemkimon changed the title ~~Fix \mathit spacing and italic correction~~ Fix \mathit font and italic correction Sep 6, 2018

ylemkimon added 2 commits September 6, 2018 14:04

Fix \mathit font (Math-Italic -> Main-Italic) and italic correction

0d52009

Rename mathit to mathdefault and mainit to mathit

f354da8

ylemkimon changed the title ~~Fix \mathit font and italic correction~~ Fix \mathit font and italic correction and add \mathnormal Sep 6, 2018

Add \mathnormal

702c454

ylemkimon commented Sep 6, 2018

View reviewed changes

ylemkimon added the GH Review: review-needed label Sep 6, 2018

ylemkimon requested a review from kevinbarabash September 6, 2018 13:27

ylemkimon added this to the Version 0.10.0 milestone Sep 6, 2018

Merge branch 'master' into mathit

ebb2ee9

kevinbarabash reviewed Sep 22, 2018

View reviewed changes

kevinbarabash approved these changes Sep 22, 2018

View reviewed changes

Merge branch 'master' into mathit

2c6f43f

edemaine reviewed Oct 2, 2018

View reviewed changes

Merge branch 'master' into mathit

a9fdd2a

ylemkimon merged commit ba8e224 into KaTeX:master Oct 10, 2018

maxlazio pushed a commit to gitlabhq/gitlabhq that referenced this pull request Jan 21, 2019

Update spec/features/markdown/math_spec.rb

a763d5f

Refer to KaTeX/KaTeX#1700 for additional details.

tigefa4u pushed a commit to tigefa4u/gitlabhq that referenced this pull request Jan 25, 2019

Update spec/features/markdown/math_spec.rb

e651036

Refer to KaTeX/KaTeX#1700 for additional details.

tigefa4u pushed a commit to tigefa4u/gitlabhq that referenced this pull request Jan 30, 2019

Update spec/features/markdown/math_spec.rb

5b8c9f6

Refer to KaTeX/KaTeX#1700 for additional details.

ylemkimon deleted the mathit branch March 21, 2019 14:28

snyk-bot mentioned this pull request Feb 23, 2020

[Snyk] Upgrade katex from 0.9.0 to 0.11.1 saurabharch/Rocket.Chat#1

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Fix `\mathit` font and italic correction and add `\mathnormal` #1700

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Fix \mathit font and italic correction and add \mathnormal #1700

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Fix `\mathit` font and italic correction and add `\mathnormal` #1700

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