Support loading variable fonts as application fonts in Freetype

When loading the fonts, we go through all the named instances
and register these as subfamilies. In addition to exposing these
variants by style name, we also register them with the according
weights, italic style and stretch. This adds a field to FontFile
to allow piping the instance index through to when we instantiate
the face.

[ChangeLog][Fonts] Added support for selecting named instances in
variable application fonts when using the Freetype backend.

Task-number: QTBUG-108624
Change-Id: I57ef6b4802756dd408c3aae1f8a6c792a89bee6a
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 47 insertions, 0 deletions

diff --git a/tests/auto/gui/text/qfontdatabase/tst_qfontdatabase.cpp b/tests/auto/gui/text/qfontdatabase/tst_qfontdatabase.cpp
index 172cb2480b..81c402cd89 100644
--- a/tests/auto/gui/text/qfontdatabase/tst_qfontdatabase.cpp
+++ b/tests/auto/gui/text/qfontdatabase/tst_qfontdatabase.cpp
@@ -61,6 +61,8 @@ private slots:
 
     void stretchRespected();
 
+    void variableFont();
+
 #ifdef Q_OS_WIN
     void findCourier();
 #endif
@@ -70,6 +72,7 @@ private:
     QString m_testFont;
     QString m_testFontCondensed;
     QString m_testFontItalic;
+    QString m_testFontVariable;
 };
 
 tst_QFontDatabase::tst_QFontDatabase()
@@ -82,10 +85,12 @@ void tst_QFontDatabase::initTestCase()
     m_testFont = QFINDTESTDATA("testfont.ttf");
     m_testFontCondensed = QFINDTESTDATA("testfont_condensed.ttf");
     m_testFontItalic = QFINDTESTDATA("testfont_italic.ttf");
+    m_testFontVariable = QFINDTESTDATA("testfont_variable.ttf");
     QVERIFY(!m_ledFont.isEmpty());
     QVERIFY(!m_testFont.isEmpty());
     QVERIFY(!m_testFontCondensed.isEmpty());
     QVERIFY(!m_testFontItalic.isEmpty());
+    QVERIFY(!m_testFontVariable.isEmpty());
 }
 
 void tst_QFontDatabase::styles_data()
@@ -505,5 +510,47 @@ void tst_QFontDatabase::findCourier()
 }
 #endif
 
+void tst_QFontDatabase::variableFont()
+{
+    {
+        QFont f;
+        f.setStyleStrategy(QFont::NoFontMerging);
+        QFontPrivate *font_d = QFontPrivate::get(f);
+        if (!font_d->engineForScript(QChar::Script_Common)->supportsVariableApplicationFonts())
+            QSKIP("Variable application fonts only supported on Freetype currently");
+    }
+
+    int id = QFontDatabase::addApplicationFont(m_testFontVariable);
+    if (id == -1)
+        QSKIP("Skip the test since app fonts are not supported on this system");
+
+    QString family = QFontDatabase::applicationFontFamilies(id).first();
+    {
+        QFont font(family);
+        QCOMPARE(QFontInfo(font).styleName(), u"Regular"_s);
+        QCOMPARE(QFontInfo(font).weight(), QFont::Normal);
+    }
+
+    {
+        QFont font(family);
+        font.setWeight(QFont::ExtraBold);
+        QCOMPARE(QFontInfo(font).styleName(), u"QtExtraBold"_s);
+        QCOMPARE(QFontInfo(font).weight(), QFont::ExtraBold);
+    }
+
+    {
+        QFont regularFont(family);
+        QFont extraBoldFont(family);
+        extraBoldFont.setStyleName(u"QtExtraBold"_s);
+
+        QFontMetricsF regularFm(regularFont);
+        QFontMetricsF extraBoldFm(extraBoldFont);
+
+        QVERIFY(regularFm.horizontalAdvance(QLatin1Char('1')) < extraBoldFm.horizontalAdvance(QLatin1Char('1')));
+    }
+
+    QFontDatabase::removeApplicationFont(id);
+}
+
 QTEST_MAIN(tst_QFontDatabase)
 #include "tst_qfontdatabase.moc"