What’s new in babel 24.6

2024-06-02

Improved transforms

A more refined control on the horizontal list, including line breaking, requires not only spaces and penalties, but also kerns and non-discardable items. In order to deal with rules for scripts like the CJK family, now transforms can insert \kern’s and \novrule’s (an alternative in luatex to empty \hbox’es). The new keys are kern and norule. The first one takes a numerical argument, with the width in em units, while the second takes three arguments with the width, height and depth of the empty (invisible) rule to be added, again in em units.

With the following declaration, the quotation mark is made halfwidth, while the period is made halfwidth only at the end of a line (which means 。“ takes 1.5 em if in the same line):

\babelprehyphenation{chinese}{ 。“ }{
  {},
  { insert, kern= -.5 },
  { insert, penalty = 0 },
  { insert, kern = .5 },
  { insert, norule = -.5 0 0 },
  {}
}

In some cases (particularly if the last replacement can be applied to the last node in the list), you may need to insert a node after the next one. A new key after, similar to insert, does the job. For example, with:

\babelprehyphenation{english}{ d }{
  { insert, space = .5 0 0, step = 1 },
  { after, space = .5 0 0 },
  {},
}

(\mbox{end}) prints ‘(en d )’. (The step is necessary to avoid an infinite loop.)

In addition, a new key, tentative, incomplete and, admittedly, not very useful in its current state, is node, which inserts an empty node with the given type and, if provided after a space, subtype (0 by default). Use names, not values (see the luatex manual). An example with subtype is node = hlist cell.

A bug in step (which was sometimes ignored) has been fixed.