[texhax] TeX Queries (2): Artificial Break

Philip TAYLOR P.Taylor at rhul.ac.uk
Thu Jul 19 09:56:03 CEST 2012

Paul Isambert wrote:

> Paul Stanley <paulrichardstanley at gmail.com> a écrit:

>> let me get this right, there's no letter spacing applied in documents
>> compiled by the legacy Tex engine. does that mean the glyphs are
>> always adjacent and any gap between the characters is achieved by kerning?
> Exactly (except that kerning does not necessarily produce a gap; more
> often than not, it brings two glyphs closer to each other).

But may I clarify "always adjacent"; this does mean that there
is still space between the rightmost extreme of the left glyph
and the leftmost extreme of the right glyph, but this space is
entirely due to their side-bearings and no additional space is
introduced by TeX.

> No, precisely. TeX stacks lines as they go, like ragged bricks without
> mortar.

That might create the wrong impression : it is not like ragged bricks
without mortar -- rather, it is like consecutive rows of non-uniform
bricks, all bricks on a single row sharing a single baseline, but
with some descending below that baseline and with each brick
potentially having a different height to its neighbour (to a maximum
of sixteen heights in standard TeX, because of an "optimisation"
in the specification of TFM files).  But there /is/ mortar; however,
it is used only to pad out the less-tall bricks to the height of
the tallest, and to pad out those bricks that lack descenders to
the depth of the deepest descender (if any such is present).  The
top of the tallest brick in the row below will align vertically
with the bottom of the deepest brick in the row above

Philip Taylor

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