The "Private Use Area" are subsets of Unicode which are not
considered regular characters, but reserved for fonts to provide
custom glyphs.
If these were used and the main font did not have support for them,
we would look them up in other fonts and sometimes display an
arbitrary selection of glyphs, based on whatever existed on the
platform. This is unexpected and different from how native apps
work on Windows, for instance.
[ChangeLog][QtGui][Text] Font merging (automatic assignment of
alternative fonts) is no longer applied for characters in the
Private Use Areas of Unicode.
Pick-to: 6.5
Fixes: QTBUG-110502
Change-Id: Id2c63786aafda59bf170e0d7263eb78a391fe46d
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
fc33fea999