1 files changed, 31 insertions, 0 deletions
diff --git a/util/unicode/README b/util/unicode/README
index ca34266a36..e52f26175a 100644
--- a/util/unicode/README
+++ b/util/unicode/README
@@ -1 +1,32 @@
 Unicode is used to generate the unicode data in src/corelib/tools.
+
+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.)
+* 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. Hopefully that doesn't matter.
+* Assertions 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.
+* That may have updated qtbase/src/corelib/tools/qunicodetables.cpp;
+  if so the update matters; be sure to commit the changes to data/ at
+  the same time and update tools/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.
+
+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.