DirectWrite: Implement transforms for grayscale aa

When cleartype rendering was turned off, transforms would be
badly broken with the DirectWrite engine because we did not
implement the appropriate code path there. In Qt 5.6, this
would become especially visible, since DirectWrite is always
used when high-dpi scaling is enabled.

[ChangeLog][Windows][DirectWrite] Added transformation
support to DirectWrite engine when using grayscale antialiasing.

Task-number: QTBUG-49562
Change-Id: Ic5f7dd5b020a85ed1b6473c511a67cdb5ed5cedb
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.h b/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.h
index da772469e9..cee8691d69 100644
--- a/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.h
+++ b/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.h
@@ -86,6 +86,7 @@ public:
     bool supportsSubPixelPositions() const;
 
     QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition);
+    QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t);
     QImage alphaRGBMapForGlyph(glyph_t t, QFixed subPixelPosition, const QTransform &xform);
 
     QFontEngine *cloneWithSize(qreal pixelSize) const;