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Synchronizing text

From: Werner Donné <werner.donne@re.be>
Date: Wed, 17 Aug 2005 14:37:52 +0200
Message-ID: <43032FA0.9040901@re.be>
To: xsl-editors@w3.org

Dear Editors,

It is not uncommon to have text synchronized across a document,
i.e. to make sure text lines on all pages, or all columns of a
page, start at a multiple of some fixed value. On a multi-column
page, for example, there would be no shift of the text lines
between two columns, as if a line runs through all columns
interleaved with gaps. The text can be temporarily desynchronized
because of other kinds of material such as images and tables. It
should, however, always fall back in synchronization, in this
use case that is.

This can be achieved by setting the "line-stacking-strategy" to
"line-height" and by calculating "space-before" and "space-after"
in such a way that the result after space resolution is always a
multiple of the line height. If the font size varies, for example
for titles, the combination of the text, "space-before" and
"space-after" should be a multiple of the line height.

There is, however, a problem with the material that may come
between paragraphs, especially when its exact height is not known.
In that case the desynchronization can't be compensated with the
"space-before" and "space-after" properties.

One solution is to add a new value to the "block-progression-dimension"
property, for example "round-to-line-height". This would behave as
"auto", except that the result is rounded up to the nearest
multiple of the line height if the "line-stacking-strategy" is set
to "line-height".

Another is to add a new value to the "line-stacking-strategy" property,
for example "synchronized". The behaviour would be the same as for
"line-height", except that text lines would always start at the
nearest multiple of the line height starting from the top edge of
the content rectangle of the "page-reference-area" (in lrtb writing
mode), after space resolution. This would make it much easier for
style sheet writers than the first solution.

Best regards,

Werner Donné  --  Re BVBA
Engelbeekstraat 8
B-3300 Tienen
tel: (+32) 486 425803	e-mail: werner.donne@re.be
Received on Wednesday, 17 August 2005 12:38:51 UTC

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