The fall 2020 LaTeX release is available

This release introduces a number of important enhancements.

A general hook management system for LaTeX

Most LaTeX users and package writers will know the handful of hooks that LaTeX has been offering until now, the most important one perhaps being \AtBeginDocument. These are important hooks, but they are far too few so that in many cases package developers had to directly patch the internals of LaTeX. This resulted in many problems.

With the new hook management system, LaTeX will get many more hooks that package writers (and authors) can use to add code in a controlled and reliable way. New hooks have been added in a number of places by using the new system and more will follow over time. Available now are:

• Hooks to add code before and after environments (formerly offered through the etoolbox package);
• Hooks used when loading files, packages, or classes (similar to what the filehook package now provides);
• Hooks in the page-building process (e.g., functionality previously available through packages such as atbegshi or atveryend and a few others).

The important point here is not so much that the functionality of these packages has been integrated into the LaTeX kernel, but that the hook management system provides a single structured way for different packages to reliably add and order code. This will resolve many of the inter-package interoperability issues which formerly could be resolved (if at all) only by loading the packages in a specific order, or by the use of complex and fragile code inside the packages to account for various scenarios in user documents.

The hook management system is currently described in these three documents:

• texdoc lthooks — The description of the interfaces and the core hooks already added to the kernel.
• texdoc ltshipout — The documentation of the hooks available during the page production process.
• texdoc ltfilehook — hooks that can be used before or after a file gets loaded.

Providing xparse as part of the format

In the previous release we added the LaTeX3 programming layer to the LaTeX format to improve the loading speed when packages using expl3 are used. In this release we are now extending this support by integrating xparse so that the extended interface for defining document-level commands becomes available out of the box.

This enables users and most importantly package developers to easily define LaTeX commands with multiple optional arguments or other syntax features with ease. For details, check out the xparse documentation, e.g., via texdoc xparse.

Improving the font series handling

In the previous release we extended NFSS (the new font selection scheme) to better support modern fonts that offer different font faces, e.g., condensed, semi-bold, etc., and make them work seamlessly with each other. Experiences with the extended interface showed that for some use cases adequate support was still missing or that in special setups the algorithms sometimes selected a wrong font series value. These cases have now been resolved and additional support commands have been added. For example, with

\IfFontSeriesContextTF{〈context〉} {〈true code〉}{〈false code〉}

you can now define commands that behave differently depending on the current font series context. The 〈context〉 to check has to be specified as either bf or md. The command then chooses the 〈true code〉 or the 〈false code〉 based on where it is used (e.g., inside \textbf (or \bfseries) or not).

A large number of other enhancements and corrections

There are nearly fifty other enhancements and corrections that we documented in the ltnews article for this release (and a few very minor ones that only made it into the changes.txtfile) The most important ones from a user perspective are:

• Support for length expression in coordinates of picture commands as an alternative to decimal numbers denoting a multiple of \unitlength, e.g., \put(0,.2\textheight){...}
• New commands to make copies of robust commands (\let wouldn’t work for them)
• A new \ShowCommand command to display the full definition of a robust command (works also on other commands)

But read the whole ltnews article because there may be other gems that are useful for you.

Where to learn more …

The new features and most the important bug fixes made in this release are documented in “LaTeX2e News Issue 32”. This document can be found on the LaTeX2e news page where you will also find release information for earlier LaTeX releases.

Happy LaTeXing — Frank