qt5base-lts/util/unicode
Edward Welbourne a111dd26b1 Document the indexing used in the Unicode tables
Make clear why we don't need to assert against out-of-bounda accesses
in the generated code, provided the code point is within its bound,
(Using one table's early entries as indices into later in the same
table at which to look up indices into another table made it a little
hard to work out what was going on, especially as nothing told me
about the early / late distinction. Record what I discovered, to save
the next person to stumble into this some confusion.)

Change-Id: I8e5771a7f3d70c1911aeae1b0cabe5c47bc7e9c7
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
2020-08-20 09:02:00 +02:00
..
data Update UCD to Revision 26 2020-03-14 11:26:59 +01:00
x11 Initial import from the monolithic Qt. 2011-04-27 12:05:43 +02:00
.gitattributes Initial import from the monolithic Qt. 2011-04-27 12:05:43 +02:00
main.cpp Document the indexing used in the Unicode tables 2020-08-20 09:02:00 +02:00
README Update UCD to Revision 26 2020-03-14 11:26:59 +01:00
unicode.pro Initial import from the monolithic Qt. 2011-04-27 12:05:43 +02:00
writingSystems.sh Updated license headers 2016-01-21 18:55:18 +00:00

Unicode is used to generate the unicode data in src/corelib/text/.

To update:
* Find the data (UAX #44, UCD; not the XML version) at
  ftp://www.unicode.org/Public/zipped/$Version/
* Unpack the zip file; for each file in data/, replace with the new
  version; find the *BreakProperty.txt in auxiliary/. (These last are
  only in the zip, not in the web-space's unpacked versions.)
* In tst_QTextBoundaryFinder's data/ sub-directory, update its files
  from the auxiliary/ sub-directory of the UCD data.
* If needed, add an entry to enum QChar::UnicodeVersion for the new
  Unicode version
* In that case, also update main.cpp's initAgeMap and DATA_VERSION_S*
  to match
* Build this project. Its binary, unicode, ignores command-line
  options and assumes it is being run from this directory. When run,
  it produces lots of output. If it gets as far as updating
  qunicodetables.cpp the output hopefully doesn't matter.
* It'll end prematurely with a qFatal() message if it needs updates,
  either in main.cpp or in QChar:
  * "unassigned or unhandled age value:" initAgeMap() and
    QChar::UnicodeVersion;
  * "Unhandled script property value:" initScriptMap(), QChar::Script,
    qharfbuzzng.cpp's _qtscript_to_hbscript[] array and
    qfontconfigdatabase.cpp's specialLanguages.
  * "unassigned word break class:" enum WordBreakClass,
    word_break_class_string and initWordBreak();
* Assertions or other qFatal()s may trigger: if so, study code and
  understand what's more complicated about this update; talk to folk
  named in the git logs, maybe push a WIP to gerrit to solicit
  advice. Some bit-field may need to be expanded, for example. In some
  cases QChar may need additions to some of its enums.
* Build with the modified code, fix any compilation issues, make check
  in suitable directories, including tst_QTextBoundaryFinder.
* That may have updated qtbase/src/corelib/text/qunicodetables.cpp; if
  so the update matters; be sure to commit the changes to data/ at the
  same time and update text/qt_attribution.json to match; use the UCD
  Revision number, rather than the Unicode standard number, as the
  Version, for all that qunicodetables.cpp uses the latter (see the
  'UAX #44, UCD' page linked from https://www.unicode.org/ucd/ for the
  table with this).
* If there are enum additions in qchar.h (public API), be sure to also
  update the documentation in qchar.cpp for each affected enum,
  respecting the existing ordering.
* If you don't normally build in the source tree, remember to delete
  qtbase/.qmake.stash while you're cleaning up.

The script writingSystems.sh generates a list of writing systems,
ostensibly as a the basis for updating QFontDatabase::WritingSystem
enum; however, the Release 20 output of it contains many more writing
systems than are present in that enum, suggesting it has not been run
in a very long time. Further research needed.