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iOS: Fix fallback fonts on iOS 13+ 

Since iOS 13, the cascade list for the default UI font contains
meta-families for several writing systems, such as CJK. Since
these font families were never populated to the database, we ignored
them in Qt, and thus got missing glyphs for the characters in question.

The fix is to make sure these fonts are populated in the database.
It contains a partial backport of 922d195020,
which adds the qt_isFamilyPopulated() accessor to allow us to check
if the family has been populated in the font database. In Qt 5.14,
there is public API for this in QPlatformFontDatabase, so this is
a temporary resolution until then.

Fixes: QTBUG-77467
Change-Id: Ia9ebb8a19ad2367eb764ae1496a52966b465336b
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
bb10
Eskil Abrahamsen Blomfeldt 2019-09-25 15:11:29 +02:00
parent 947883141d
commit d5abda313d
2 changed files with 28 additions and 0 deletions
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7
src/gui/text/qfontdatabase.cpp
View File

@ -793,6 +793,13 @@ QString qt_resolveFontFamilyAlias(const QString &alias)
return alias;
}
Q_GUI_EXPORT bool qt_isFontFamilyPopulated(const QString &familyName)
{
QFontDatabasePrivate *d = privateDb();
QtFontFamily *f = d->family(familyName, QFontDatabasePrivate::RequestFamily);
return f != nullptr && f->populated;
}
/*!
Returns a list of alternative fonts for the specified \a family and
\a style and \a script using the \a styleHint given.

21
src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
View File

@ -454,6 +454,9 @@ static void addExtraFallbacks(QStringList *fallbackList)
#endif
}
// ### Replace this with QPlatformFontDatabase::isFamilyPopulated() in Qt 5.14
Q_GUI_EXPORT extern bool qt_isFontFamilyPopulated(const QString &familyName);
QStringList QCoreTextFontDatabase::fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script) const
{
Q_UNUSED(style);
@ -481,7 +484,25 @@ QStringList QCoreTextFontDatabase::fallbacksForFamily(const QString &family, QFo
fallbackList.append(QString::fromCFString(fallbackFamilyName));
}
// .Apple Symbols Fallback will be at the beginning of the list and we will
// detect that this has glyphs for Arabic and other writing systems.
// Since it is a symbol font, it should be the last resort, so that
// the proper fonts for these writing systems are preferred.
int symbolIndex = fallbackList.indexOf(QLatin1String(".Apple Symbols Fallback"));
if (symbolIndex >= 0)
fallbackList.move(symbolIndex, fallbackList.size() - 1);
addExtraFallbacks(&fallbackList);
// Since iOS 13, the cascade list may contain meta-fonts which have not been
// populated to the database, such as ".AppleJapaneseFont". It is important that we
// include this in the fallback list, in order to get fallback support for all
// languages
for (const QString &fallback : fallbackList) {
if (!qt_isFontFamilyPopulated(fallback))
const_cast<QCoreTextFontDatabase *>(this)->populateFamily(fallback);
}
extern QStringList qt_sort_families_by_writing_system(QChar::Script, const QStringList &);
fallbackList = qt_sort_families_by_writing_system(script, fallbackList);