Android: Fix font merging

Our fallback fonts would contain a minimal list of hardcoded fallback
fonts, which is neither sufficient for displaying all text, nor
portable to different vendors which can supply different font sets.

[ChangeLog][Android] Fixed font merging problem which caused e.g.
missing glyphs for Arabic numerals.

Task-number: QTBUG-37738
Change-Id: Ic971343a1cd5610c79a81f6f6152c637937b5626
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>

2 files changed, 17 insertions, 4 deletions

diff --git a/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp b/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp
index 7f68b44ed8..7423e6c55a 100644
--- a/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp
+++ b/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp
@@ -60,7 +60,17 @@ void QAndroidPlatformFontDatabase::populateFontDatabase()
     QDir dir(fontpath, QLatin1String("*.ttf"));
     for (int i = 0; i < int(dir.count()); ++i) {
         const QByteArray file = QFile::encodeName(dir.absoluteFilePath(dir[i]));
-        addTTFile(QByteArray(), file);
+
+        QSupportedWritingSystems supportedWritingSystems;
+        QStringList families = addTTFile(QByteArray(), file, &supportedWritingSystems);
+
+        extern int qt_script_for_writing_system(QFontDatabase::WritingSystem writingSystem);
+        for (int i = 0; i < QFontDatabase::WritingSystemsCount; ++i) {
+            if (i == QFontDatabase::Any || supportedWritingSystems.supported(QFontDatabase::WritingSystem(i))) {
+                QChar::Script script = QChar::Script(qt_script_for_writing_system(QFontDatabase::WritingSystem(i)));
+                m_fallbacks[script] += families;
+            }
+        }
     }
 }
 
@@ -71,9 +81,9 @@ QStringList QAndroidPlatformFontDatabase::fallbacksForFamily(const QString &fami
 {
     Q_UNUSED(family);
     Q_UNUSED(style);
-    Q_UNUSED(script);
+
     if (styleHint == QFont::Monospace)
-        return QString(qgetenv("QT_ANDROID_FONTS_MONOSPACE")).split(";");
+        return QString(qgetenv("QT_ANDROID_FONTS_MONOSPACE")).split(";") + m_fallbacks[script];
 
-    return QString(qgetenv("QT_ANDROID_FONTS")).split(";");
+    return QString(qgetenv("QT_ANDROID_FONTS")).split(";") + m_fallbacks[script];
 }
diff --git a/src/plugins/platforms/android/qandroidplatformfontdatabase.h b/src/plugins/platforms/android/qandroidplatformfontdatabase.h
index 3cbfe95d36..cdd3cf1674 100644
--- a/src/plugins/platforms/android/qandroidplatformfontdatabase.h
+++ b/src/plugins/platforms/android/qandroidplatformfontdatabase.h
@@ -53,6 +53,9 @@ public:
                                            QFont::Style style,
                                            QFont::StyleHint styleHint,
                                            QChar::Script script) const;
+
+private:
+    QHash<QChar::Script, QStringList> m_fallbacks;
 };
 
 #endif // QANDROIDPLATFORMFONTDATABASE_H