Add \jot lineskip to aligned environment, switch contents to displaystyle, and add gathered #725

edemaine · 2017-06-10T18:07:25Z

AMS environments aligned and gathered (not yet implemented in KaTeX, see #682) use \openup\jot to increase \baselineskip by \jot (which defaults to 3pt, see #687 for overriding). This lineskip in turns defines \strutbox in the array environment, which then gets scaled by \arraystretch. (As reported in #686, which this PR fixes.)

I've added a rowsAreLines option to array objects in the parse tree that encourages the outputter (here, buildHTML) to add \jot (currently hard-coded to 3pt, see #687) to each line. This seemed simpler than e.g. manually putting the equivalent of 3pt in the environment definition, and will be useful when we implement gathered in #682.

texcmp Aligned before this change:

texcmp Aligned after this change:

Note that other environments like array remain unaffected, as they were already correct (vertically anyway):

edemaine · 2017-06-10T18:24:31Z

While I'm here, I tweaked the definition of the aligned environment to put all contents in \displaystyle. This feature was pointed out by @arnog in #682, and I confirmed that it's the case in LaTeX. For example, $\begin{aligned} \frac{x}{y} \end{aligned}$ now uses a display fraction, as it does in LaTeX.

I'm going to add the gathered environment next, to this PR, as it's almost trivial at this point.

edemaine · 2017-06-10T19:42:07Z

I added the gathered environment, fixing #682. The test case (with \begin{gathered} on the left and \begin{array}{c} on the right) renders pretty well, but not quite as perfectly:

Let me know if you can see where the extra vertical space is coming from in LaTeX... The difference is the \frac in the cell -- both gathered and aligned behave the same in terms of vertical spacing (in both KaTeX and LaTeX). Anyway, the new spacing is far better than current KaTeX.

kevinbarabash · 2017-06-10T20:08:44Z

src/buildHTML.js

@@ -592,6 +592,9 @@ groupTypes.array = function(group, options) {

    // Vertical spacing
    const baselineskip = 12 * pt; // see size10.clo
+    // Default \jot from ltmath.dtx
+    // TODO(edemaine): allow overriding \jot via \setlength (#687)


kevinbarabash · 2017-06-10T20:12:40Z

@edemaine can you rebase and re-run make screenshot now that #718 has been merged?

kevinbarabash · 2017-06-10T20:13:08Z

whoops... I only meant to "comment" not "close and comment".

kevinbarabash · 2017-06-10T20:15:08Z

src/environments.js

    };
-    res = parseArray(context.parser, res);
+    res = parseArray(context.parser, res, "display");


Is the aligned environment also supposed to be in \displaystyle only?

Yes, I checked in LaTeX, and $\begin{aligned} \frac{x}{y} \end{aligned}$ renders a display fraction.

kevinbarabash · 2017-06-10T20:17:54Z

src/environments.js

+    // Count number of columns = maximum number of cells in each row.
+    // At the same time, prepend empty group {} at beginning of every second
+    // cell in each row (starting with second cell) so that operators become
+    // binary.


This is so that operators at the start of cell will have the proper spacing around them. What about operators at the end of a cell, or does that not happen in practice?

I just added documentation here, because it took me a long time to figure out why the existing code was adding empty groups. I checked and this is indeed how it's implemented in amsmath, specifically in \start@aligned. I'll add a note this effect.

kevinbarabash · 2017-06-10T20:23:29Z

src/buildHTML.js

+        // In AMS multiline environments such as aligned and gathered, rows
+        // correspond to lines that have additional \jot added to the
+        // \baselineskip via \openup.
+        if (group.value.rowsAreLines) {


The naming of this variable is confusing to me. Aren't rows already lines? This just adds more space between the rows/lines. Maybe change this to addJotBetweenRows.

Agreed, that is confusing. Renamed to addJot, which seems clear enough (as \jot is an interline spacing).

edemaine · 2017-06-10T20:40:55Z

Comments addressed in 3c00b27 . Thanks for the review!

kevinbarabash · 2017-06-10T20:53:03Z

@edemaine did you rebase and run make screenshots? I would've expected the LimitControls screenshots to change, see https://github.com/Khan/KaTeX/pull/718/files#diff-e55441e2f8a6090eac1fdb9e12ed86ed.

edemaine · 2017-06-10T20:58:58Z

@kevinbarabash Yes, I rebased. Almost no screenshot tests involve aligned or gathered environments --
just the old Aligned test (modified in this PR) and the new Gathered test (new to this PR). Is there a reason LimitControls should have changed that I'm missing?

kevinbarabash · 2017-06-10T21:08:50Z

@edemaine sorry... I wasn't looking at things carefully. I was comparing the ascent of glyphs when I should've been looking at the baselines. Also, for some reason I thought this was a diff that was opened before the #718, but it was actually only opened a few hours ago.

kevinbarabash · 2017-06-10T21:11:06Z

Thanks for the PR. Awesome to see how quickly new environments can be added.

…quals Fix KaTeX#657 (modulo KaTeX#725)

Fix KaTeX#725.

…quals Fix KaTeX#657 (modulo KaTeX#725)

…quals (#727) Fix #657 (modulo #725)

edemaine force-pushed the jot branch 2 times, most recently from 0ef1ded to 0c9a561 Compare June 10, 2017 19:34

edemaine force-pushed the jot branch from 0c9a561 to 966091c Compare June 10, 2017 19:42

edemaine changed the title ~~Add \jot lineskip to aligned environment. Fix #686~~ Add \jot lineskip to aligned environment, switch contents to displaystyle, and add gathered Jun 10, 2017

This was referenced Jun 10, 2017

Spacing between rows of an aligned environment too tight #686

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Need gathered environment #682

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kevinbarabash reviewed Jun 10, 2017

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kevinbarabash closed this Jun 10, 2017

kevinbarabash reopened this Jun 10, 2017

edemaine added 3 commits June 10, 2017 16:15

Add \jot to gap between lines in aligned environment. Fix KaTeX#686

5359f35

Bug fix in aligned: Contents are displaystyle

800f671

Add gathered environment

f949f55

edemaine force-pushed the jot branch from 966091c to f949f55 Compare June 10, 2017 20:15

kevinbarabash requested changes Jun 10, 2017

View reviewed changes

Implement comments

3c00b27

edemaine force-pushed the jot branch from 5df43a3 to 3c00b27 Compare June 10, 2017 20:40

edemaine mentioned this pull request Jun 10, 2017

Feature request: support \colonequals or similar #657

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kevinbarabash approved these changes Jun 10, 2017

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kevinbarabash merged commit 06d6c96 into KaTeX:master Jun 10, 2017

edemaine added a commit to edemaine/KaTeX that referenced this pull request Jun 10, 2017

Implement \coloneqq, \colonequals, etc. based on mathtools and colone…

8ffd498

…quals Fix KaTeX#657 (modulo KaTeX#725)

edemaine added a commit to edemaine/KaTeX that referenced this pull request Jun 10, 2017

Implement \coloneqq, \colonequals, etc. based on mathtools and colone…

66687c4

…quals Fix KaTeX#657 (modulo KaTeX#725)

kohler added a commit to kohler/KaTeX that referenced this pull request Jun 29, 2017

Vertically center single-character \mathop.

a1a1e02

Fix KaTeX#725.

edemaine added a commit to edemaine/KaTeX that referenced this pull request Jun 30, 2017

Implement \coloneqq, \colonequals, etc. based on mathtools and colone…

2ffb7f6

…quals Fix KaTeX#657 (modulo KaTeX#725)

edemaine added a commit to edemaine/KaTeX that referenced this pull request Jun 30, 2017

Implement \coloneqq, \colonequals, etc. based on mathtools and colone…

642b66e

…quals Fix KaTeX#657 (modulo KaTeX#725)

kevinbarabash pushed a commit that referenced this pull request Jun 30, 2017

Implement \coloneqq, \colonequals, etc. based on mathtools and colone…

0edd3d1

…quals (#727) Fix #657 (modulo #725)

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Add \jot lineskip to aligned environment, switch contents to displaystyle, and add gathered #725

Add \jot lineskip to aligned environment, switch contents to displaystyle, and add gathered #725

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Add \jot lineskip to aligned environment, switch contents to displaystyle, and add gathered #725

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