OS X/iOS: Fix stretched font rendering

Setting the stretch of a QFont did not work correctly on OS X or
iOS.

Two things are needed to make it work: First of all, we need to
properly set the transform when creating the CTFont.

In addition, we need to manually scale the advances, as
CTRunGetPositions() does not do this for us. On OS X 10.6, however,
there was a regression and CTRunGetPositions() would return scaled
positions, so we exclude the step to scale the advances on this
particular version.

This is an adaptation of bc25cfdd65452efa226cbd544c9ae9803eb6748a
in Qt 4.

[ChangeLog][QtGui][OS X/iOS] Fixed a bug when rendering fonts that
were set to be stretched.

Task-number: QTBUG-43801
Change-Id: I4902a9f5e29299761e3c2c5c6d6d80ee1dea1a25
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>

2 files changed, 13 insertions, 1 deletions

diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index d156124b98..8f60847250 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -1237,6 +1237,15 @@ int QTextEngine::shapeTextWithHarfbuzzNG(const QScriptItem &si, const ushort *st
         }
 
 #ifdef Q_OS_MAC
+        // CTRunGetPosition has a bug which applies matrix on 10.6, so we disable
+        // scaling the advances for this particular version
+        if (actualFontEngine->fontDef.stretch != 100
+                && QSysInfo::MacintoshVersion != QSysInfo::MV_10_6) {
+            QFixed stretch = QFixed(actualFontEngine->fontDef.stretch) / QFixed(100);
+            for (uint i = 0; i < num_glyphs; ++i)
+                g.advances[i] *= stretch;
+        }
+
         if (actualFontEngine->fontDef.styleStrategy & QFont::ForceIntegerMetrics) {
             for (uint i = 0; i < num_glyphs; ++i)
                 g.advances[i] = g.advances[i].round();
diff --git a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
index 5a6c5de0b4..fe408305e0 100644
--- a/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
+++ b/src/platformsupport/fontdatabases/mac/qcoretextfontdatabase.mm
@@ -370,6 +370,8 @@ void QCoreTextFontDatabase::releaseHandle(void *handle)
     CFRelease(CTFontDescriptorRef(handle));
 }
 
+extern CGAffineTransform qt_transform_from_fontdef(const QFontDef &fontDef);
+
 QFontEngine *QCoreTextFontDatabase::fontEngine(const QFontDef &f, void *usrPtr)
 {
     qreal scaledPointSize = f.pixelSize;
@@ -384,7 +386,8 @@ QFontEngine *QCoreTextFontDatabase::fontEngine(const QFontDef &f, void *usrPtr)
         scaledPointSize = f.pointSize;
 
     CTFontDescriptorRef descriptor = (CTFontDescriptorRef) usrPtr;
-    CTFontRef font = CTFontCreateWithFontDescriptor(descriptor, scaledPointSize, NULL);
+    CGAffineTransform matrix = qt_transform_from_fontdef(f);
+    CTFontRef font = CTFontCreateWithFontDescriptor(descriptor, scaledPointSize, &matrix);
     if (font) {
         QFontEngine *engine = new QCoreTextFontEngine(font, f);
         engine->fontDef = f;