# What’s New in MathJax v3.2¶

Version 3.2 includes a number of new features, as well as bug fixes for several issues with version 3.1. The new features are described below.

See also the release notes for the list of bugs that have been fixed in version 3.2.

## Lazy Typesetting¶

Although MathJax version 3 is already an order of magnitude faster than version 2, with version 3.2 we offer a new extension that is designed to make pages with large numbers of equations perform even better. It implements a “lazy typesetting” approach that only typesets an expression when it comes into view, which means that expressions will not be typeset when they are not visible. Your readers will not have to wait for the entire document to typeset, which can speed up their initial view of the page. Furthermore, any expressions that are never seen will not be typeset. This also helps with the situation where you may link to a particular location in your page (via a URL with a hash); in version 2, typesetting the material above that point can cause the browser to change the scroll position, and so the user may not end up at the proper location in the page. With the lazy extension, the material above that point is not typeset until the user scrolls upwards, and so there is no position change.

Lazy typesetting works best with SVG output, but changes (discussed below) with the way the CommonHTML output handles its stylesheet updates make the CHTML output nearly as fast. With TeX input, the lazy extension makes sure that previous expressions are processed by TeX (though not output to the page) so that any macro definitions or automatic equation numbers are in place when the visible expressions are processed. Currently, documents that contain \ref or \eqref links may not yet work properly, since target equations may not have been typeset, and so the link location may not be marked in the document. In particular, forward references are unlikely to work, and backward references will work only if the target expression has already been typeset. We hope to improve this situation in a future release.

See the Lazy Typesetting documentation for information on how to configure MathJax to use this new feature.

## CSS Updates¶

MathJax’s CHTML output handles the characters that appear in the math on the page by storing information about their bounding boxes and text content in a CSS stylesheet. When additional math is typeset, this stylesheet may need to be updated, and in previous versions, MathJax would replace the entire stylesheet with a new one. This can cause visual flashing, and can be expensive as the browser must re-evaluate all the rules and apply them again. In version 3.2, the CHTML output now adds rules to the stylesheet individually, so the older rules are not replaced, and only the new rules must be evaluated and applied. This makes updates must faster, and is of particular benefit to the lazy-typesetting extension described above, as the page can be updated many times as equations scroll into view. This change makes the CHTML output work almost as smoothly as SVG output with the lazy extension.

## New TeX Packages¶

Version 3.2 includes nine new TeX extension packages:

• cases — provides environments for individually numbered cases.
• centernot — implements a centered not command (and a non-standard centerOver that places one symbol centered on top of another).
• colortbl — provides macros for coloring cells of an array or alignment.
• empheq — an environment for placing material to the left or right of an alignment that has individual equation numbers.
• gensymb — provides macros for some specific units.
• mathtools — offers a range of macros and environments for advanced mathematical typesetting.
• setoptions — provides the ability to change some TeX input jax options from within an expression (e.g., to change the tag side).
• textcomp — provides a range of macros for specifying various text characters.
• upgreek — provides macros for upright Greek characters.

These are all included in the components that end in -full (and include the TeX input jax), and you can load individual ones as you would other tex packages. Note, however, that none of these are autoloaded, though you can configure the autoload extension to do so, if you wish. See the autoload documentation for details.

In addition to these new packages, some of the older packages have been updated:

• The ams package now includes flalign, xalign, and xxalign environments. In addition, the multline extension has been made more compatible with actual LaTeX. In the past, multline was set to be 85% of the container width, but now it is set to 100%, but with a 1em indent on both sides; when there is a tag, the indent on the tag side is increased by the width of the tag, as is the case in LaTeX. The width was stored in the multlineWidth configuration option in the tex configuration block. That has now been moved to the ams block in the tex configuration, and there is a new multlineIndent value. These are set to 100% and 1em respectively. To obtain the old behavior, set them to 85% and 0. Currently, if multlineWidth is found in the main tex option block, it will be moved to the ams block, but that backward-compatibility code will be removed in a future release.
• The physics package now implements all macros, even those that are not officially documented, but are nevertheless available in LaTeX. In addition, it now implements the italicdiff and arrowdel options.
• The following macros have been added to the indicated package:
• \overunderset (ams) — a combination of \overset and \underset.
• \stackbin (ams) — similar to \stackrel but produces a symbol with the spacing of a binary operator.
• \nonscript (base) — apply the following spacing only when in display and text styles.
• \boxed (base) — puts a frame around an expression.
• \framebox (base) — puts a frame around a text argument.
• \ip, \Bqty, \qsince, \Residue (physics) — originally missing from the physics package.

## MathML Extensions¶

The MML3 extension from version 2 has been ported to version 3 and is available to be included when you load the MathML input jax. This extension implements the MathML3 elementary math tags (like <mstack> and <mlongdiv>) using an XSLT transform to convert these tags into other presentation MathML tags that MathJax has implemented. This does a reasonable job for some constructs, and a poorer job for others, but it does make it possible to process elementary math within MathJax v3. This is an experimental extension as a stop-gap measure until these tags are fully implemented within core MathJax.

See the Experimental mml3 extension documentation for information on how to configure MathJax to use this new feature.

## Explorer Update¶

The Speech-Rule Engine (SRE) that underlies MathJax’s assistive technology support has been updated to the most recent version (3.3.3). This includes support for the Hindi language, so that the expression explorer can generate speech in Hindi (as well as its other languages: English, French, German, Italian, Spanish, together with Braille support in Nemeth).

See the SRE release notes for details.

This release also ports the remaining missing features for the explorer to v3. This includes summarising expressions and navigation of tabular expressions, like matrices or equation systems. See the keyboard command documentation for details.

## Other New Features¶

In addition to the major features listed above, there are some minor new features as well:

• Packages can now be specified for the textmacros extension to the TeX input jax. This allows you to configure additional macros that can be processed within text mode. See the textmacros documentation for details.
• Processing of raw Unicode characters in TeX input has been improved. In the past, nearly all non-ASCII characters would be placed within an <mo> element, which is not always the best tag to use. In version 3.2, processing of raw Unicode characters is more nuanced, so that letters are placed in <mi> elements and other symbols in <mo>. For example, a literal Greek alpha (U+03B1) will produce <mi>&#x03B1;</mi> (which is what is generated by \alpha) rather than <mo>&#x03B1;</mo> as in earlier versions. This should provide better results, though perhaps still not perfect in all cases.
• In the past, errors in the MathJax configuration options (such as an unknown option) would produce a fatal error and MathJax would not run. In version 3.2, such errors now produce non-fatal warnings instead, and MathJax will continue to process the remaining options (and then typeset the page). This means that changes to the options (like those described in the breaking changes section below) will not cause your pages to fail outright (though the old options will have no effect). You can configure MathJax to make such errors fatal again, if you wish, and you can provide a function that will be called when there is an option error so that you can more easily trap such errors and handle them yourself. See the Startup Options for more details.
• The component loader uses a set of filters to convert a component specification (like [tex]/physics) to the full URL for loading the extension. In the past, it was difficult to hook into that filtering mechanism, but in version 3.2, you can now configure additional filters for the loader. See the Loader Options documentation for more details.

## Breaking Changes in this Release¶

Some of the changes made to the options to accommodate the updated speech-rule engine are potentially breaking changes, in that the previous options (enrichSpeech, a11y.locale, a11y.speechRules) are no longer valid options. Version 3.1.4 includes code to transfer the old options to their new locations, but that code has been removed in version 3.2. As errors in options are no longer fatal (unless you configure them to be), this change will no longer cause MathJax to fail, but will cause warning messages in the browser console, so look there for such error reports.

Similarly, the code that automatically renames the older TeX package names to their current all-lower-case versions (e.g., configMacros to configmacros and colorV2 to colorv2) has been removed from version 3.2. If you are using old package names, you will need to update your configuration. This applies to \require{} macros that refer to the older names as well as their names in the loader section, the tex.packages array, and the tex.autoload block.

Version 3.2 removes the matchFontHeight option for the SVG output jax, since it only applies to the CommonHTML output, but was previously allowed in the svg configuration block, while doing nothing.

Version 3.2 removes of the toArray() method from the LinkedList class (and its subclasses), so any custom code that uses that should switch to using Array.from(...) around the list instead.

Finally, the Box.ts and CssStyles.ts (and their associated .js files) have been moved from the output directories to the util directory. Compatibility files were placed in the original locations so that older code would continue to work, but these have been removed in v3.2, so you should modify any custom code that loads these files to obtain them from the util directory instead.