Files
odfstudio/schema
László Németh f83a04c510 tdf#167648 cui offapi xmloff sw: add DTP-feature maximum letter spacing
Add new paragraph justification option "Maximum letter spacing"
to distribute letters on (part of) the available blank area of the
justified line instead of overstretching word spacing, like DTP
software do.

This improves typography a lot, allowing typesetting visually better
i.e. more readable paragraphs, minimizing or removing rivers and
too big word spacing (which was common in columns or text without
hyphenation).

* Add spin box to Alignment in paragraph formatting dialog window,
  (also add spin boxes for future Minimum and the alternative
  percent-based Desired letter spacing, see CharKerning);

  For example (only ASCII visualization!), 100% maximum letter
  spacing adds a space character-width blank space between the
  characters, including the original space:

  0%:

  Lorem          ipsum
  pellentesque dolores
  vitae.

  100%:

  L o r e m  i p s u m
  pellentesque dolores
  vitae.

  Normal value: 3%-5% (or more for very narrow columns), which means
  e.g. 1-2 twips (twip = 1/20 pt) letter spacing in a ~12 pt text.

  Note: resolution of the custom letter spacing is only 1 twip yet.

* Store properties in paragraph model:

  css::style::ParagraphProperties::ParaPropLetterSpacingMaximum

  css::style::ParagraphProperties::ParaPropLetterSpacingMinimum

  Note: desired letter spacing is already supported by ODF/UNO,
  see css::style::CharacterProperties::CharKerning.

* Implement visual layout of maximum letter spacing.

  Note: after the last character of the line, there is an
  unwanted letter-spacing, yet (which is visible only with
  big letter-spacing values).

* Add ODF import/export (loext:letter-spacing-maximum and
  loext:letter-spacing-minimum)

* Add ODF unit test.

Note: hyphenated lines and lines with multiple portions do not
yet use custom letter spacing, yet.

Change-Id: Ieac9f21631b90ae46bed4501f12da0d15ed84d63
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/188653
Tested-by: László Németh <nemeth@numbertext.org>
Tested-by: Jenkins
Reviewed-by: László Németh <nemeth@numbertext.org>
2025-08-01 11:51:04 +02:00
..
…

Schemas for Validating ODF Files

Schemas that can be used for validating ODF files

subdirs:

  • mathml2: W3C MathML 2.0 XML Schema (needed for Math embedded objects)
  • odf1.0, odf1.1, odf1.2: official OASIS RelaxNG schemas
  • odf1.3: current OASIS draft ODF 1.3 RelaxNG schema
  • libreoffice: draft ODF schema, with additional LO extensions

The extension schema in libreoffice/ is used by all unit tests if --with-export-validation is given, which is the default.

Notably this means that if you add a new feature to the ODF filters and you add the required unit test for the new feature, then most likely the test will fail with a complaint from the validator; in this case the schema needs to be updated to contain the new elements and attributes.

The extension schema uses the RelaxNG "include" feature to refer to the ODF schema; this means that it only contains those parts of the schema that actually need to be changed - this works well in many cases because the ODF schema is quite well structured with many named patterns, but unfortunately there are a few places where that isn't the case and large chunks needed to be copied to override them.

In the easy case, to add an attribute you just want to search for the corresponding element, which will have a "foo-attlist" named pattern, and then add another attribute like this:

<rng:define name="draw-enhanced-geometry-attlist" combine="interleave"> rng:optional <rng:attribute name="drawooo:sub-view-size"> <rng:ref name="string"/> </rng:attribute> </rng:optional> </rng:define>

Currently only the features that are actually exported in the unit tests have been added to the schema; there is still some work to do here to add everything; the crashtesting script also does ODF validation of all files and now also uses the custom schema.

Unfortunately it turned out that there are a lot of extensions already for which no proposal exists [1], and in many cases not even an entry on the Wiki [2], so clearly something like this extension schema is needed.

[1] git grep TODO schema/libreoffice

[2] https://wiki.documentfoundation.org/Development/ODF_Implementer_Notes/List_of_LibreOffice_ODF_Extensions