direct2d: Work around ClearType rendering bug in translucent mode

This switches the font rendering to use gray scale antialiasing when in
translucent rendering mode. It does so by adding a flags argument to the
paint engine, allowing for future expansion in communicating render hints
from the device to the engine.

Task-number: QTBUG-41002
Change-Id: I0265154716a12060e851b603a109e9c693f5e843
Reviewed-by: Louai Al-Khanji <louai.al-khanji@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

7 files changed, 36 insertions, 15 deletions

diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.cpp b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.cpp
index f5f4923b2f..4bbe74b642 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.cpp
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.cpp
@@ -53,8 +53,9 @@ QT_BEGIN_NAMESPACE
 class QWindowsDirect2DPaintDevicePrivate
 {
 public:
-    QWindowsDirect2DPaintDevicePrivate(QWindowsDirect2DBitmap *bitmap, QInternal::PaintDeviceFlags f)
-        : engine(new QWindowsDirect2DPaintEngine(bitmap))
+    QWindowsDirect2DPaintDevicePrivate(QWindowsDirect2DBitmap *bitmap, QInternal::PaintDeviceFlags f,
+                                       QWindowsDirect2DPaintEngine::Flags paintFlags)
+        : engine(new QWindowsDirect2DPaintEngine(bitmap, paintFlags))
         , bitmap(bitmap)
         , flags(f)
     {}
@@ -64,8 +65,9 @@ public:
     QInternal::PaintDeviceFlags flags;
 };
 
-QWindowsDirect2DPaintDevice::QWindowsDirect2DPaintDevice(QWindowsDirect2DBitmap *bitmap, QInternal::PaintDeviceFlags flags)
-    : d_ptr(new QWindowsDirect2DPaintDevicePrivate(bitmap, flags))
+QWindowsDirect2DPaintDevice::QWindowsDirect2DPaintDevice(QWindowsDirect2DBitmap *bitmap, QInternal::PaintDeviceFlags flags,
+                                                         QWindowsDirect2DPaintEngine::Flags paintFlags)
+    : d_ptr(new QWindowsDirect2DPaintDevicePrivate(bitmap, flags, paintFlags))
 {
 }
 
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.h b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.h
index c9d8607497..33cc536b6d 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.h
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintdevice.h
@@ -44,6 +44,7 @@
 
 #include <QtCore/QScopedPointer>
 #include <QtGui/QPaintDevice>
+#include "qwindowsdirect2dpaintengine.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -55,7 +56,8 @@ class QWindowsDirect2DPaintDevice : public QPaintDevice
     Q_DECLARE_PRIVATE(QWindowsDirect2DPaintDevice)
 
 public:
-    QWindowsDirect2DPaintDevice(QWindowsDirect2DBitmap *bitmap, QInternal::PaintDeviceFlags flags);
+    QWindowsDirect2DPaintDevice(QWindowsDirect2DBitmap *bitmap, QInternal::PaintDeviceFlags flags,
+                                QWindowsDirect2DPaintEngine::Flags paintFlags = QWindowsDirect2DPaintEngine::NoFlag);
     QPaintEngine *paintEngine() const Q_DECL_OVERRIDE;
     int devType() const Q_DECL_OVERRIDE;
 
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
index a4e75f6571..1d28befe41 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.cpp
@@ -233,9 +233,10 @@ class QWindowsDirect2DPaintEnginePrivate : public QPaintEngineExPrivate
 {
     Q_DECLARE_PUBLIC(QWindowsDirect2DPaintEngine)
 public:
-    QWindowsDirect2DPaintEnginePrivate(QWindowsDirect2DBitmap *bm)
+    QWindowsDirect2DPaintEnginePrivate(QWindowsDirect2DBitmap *bm, QWindowsDirect2DPaintEngine::Flags flags)
         : bitmap(bm)
         , clipFlags(0)
+        , flags(flags)
     {
         pen.reset();
         brush.reset();
@@ -247,6 +248,7 @@ public:
 
     unsigned int clipFlags;
     QStack<ClipType> pushedClips;
+    QWindowsDirect2DPaintEngine::Flags flags;
 
     QPointF currentBrushOrigin;
 
@@ -868,8 +870,9 @@ public:
 
         const bool antiAlias = bool((q->state()->renderHints & QPainter::TextAntialiasing)
                                     && !(fontDef.styleStrategy & QFont::NoAntialias));
-        dc()->SetTextAntialiasMode(antiAlias ? D2D1_TEXT_ANTIALIAS_MODE_CLEARTYPE
-                                             : D2D1_TEXT_ANTIALIAS_MODE_ALIASED);
+        const D2D1_TEXT_ANTIALIAS_MODE antialiasMode = (flags & QWindowsDirect2DPaintEngine::UseGrayscaleAntialiasing)
+                ? D2D1_TEXT_ANTIALIAS_MODE_GRAYSCALE : D2D1_TEXT_ANTIALIAS_MODE_CLEARTYPE;
+        dc()->SetTextAntialiasMode(antiAlias ? antialiasMode : D2D1_TEXT_ANTIALIAS_MODE_ALIASED);
 
         dc()->DrawGlyphRun(pos,
                            &glyphRun,
@@ -913,8 +916,8 @@ public:
     }
 };
 
-QWindowsDirect2DPaintEngine::QWindowsDirect2DPaintEngine(QWindowsDirect2DBitmap *bitmap)
-    : QPaintEngineEx(*(new QWindowsDirect2DPaintEnginePrivate(bitmap)))
+QWindowsDirect2DPaintEngine::QWindowsDirect2DPaintEngine(QWindowsDirect2DBitmap *bitmap, Flags flags)
+    : QPaintEngineEx(*(new QWindowsDirect2DPaintEnginePrivate(bitmap, flags)))
 {
     QPaintEngine::PaintEngineFeatures unsupported =
             // As of 1.1 Direct2D does not natively support complex composition modes
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.h b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.h
index 1469d32876..4ed817b75f 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.h
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dpaintengine.h
@@ -59,7 +59,13 @@ class QWindowsDirect2DPaintEngine : public QPaintEngineEx
     Q_DECLARE_PRIVATE(QWindowsDirect2DPaintEngine)
 
 public:
-    QWindowsDirect2DPaintEngine(QWindowsDirect2DBitmap *bitmap);
+    enum Flag {
+        NoFlag = 0,
+        UseGrayscaleAntialiasing = 1,
+    };
+    Q_DECLARE_FLAGS(Flags, Flag)
+
+    QWindowsDirect2DPaintEngine(QWindowsDirect2DBitmap *bitmap, Flags flags);
 
     bool begin(QPaintDevice *pdev) Q_DECL_OVERRIDE;
     bool end() Q_DECL_OVERRIDE;
@@ -119,6 +125,7 @@ private:
     void adjustForAliasing(QRectF *rect);
     void adjustForAliasing(QPointF *point);
 };
+Q_DECLARE_OPERATORS_FOR_FLAGS(QWindowsDirect2DPaintEngine::Flags)
 
 QT_END_NAMESPACE
 
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.cpp b/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.cpp
index d9f7c595ca..88b440f857 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.cpp
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.cpp
@@ -62,10 +62,11 @@ public:
         , devicePixelRatio(1.0)
     {}
 
-    QWindowsDirect2DPlatformPixmapPrivate(QWindowsDirect2DBitmap *bitmap)
+    QWindowsDirect2DPlatformPixmapPrivate(QWindowsDirect2DBitmap *bitmap,
+                                          QWindowsDirect2DPaintEngine::Flags flags)
         : owns_bitmap(false)
         , bitmap(bitmap)
-        , device(new QWindowsDirect2DPaintDevice(bitmap, QInternal::Pixmap))
+        , device(new QWindowsDirect2DPaintDevice(bitmap, QInternal::Pixmap, flags))
         , devicePixelRatio(1.0)
     {}
 
@@ -91,9 +92,10 @@ QWindowsDirect2DPlatformPixmap::QWindowsDirect2DPlatformPixmap(PixelType pixelTy
 }
 
 QWindowsDirect2DPlatformPixmap::QWindowsDirect2DPlatformPixmap(QPlatformPixmap::PixelType pixelType,
+                                                               QWindowsDirect2DPaintEngine::Flags flags,
                                                                QWindowsDirect2DBitmap *bitmap)
     : QPlatformPixmap(pixelType, Direct2DClass)
-    , d_ptr(new QWindowsDirect2DPlatformPixmapPrivate(bitmap))
+    , d_ptr(new QWindowsDirect2DPlatformPixmapPrivate(bitmap, flags))
 {
     setSerialNumber(qt_d2dpixmap_serno++);
 
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.h b/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.h
index 702ef7af92..69243abb1d 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.h
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dplatformpixmap.h
@@ -42,6 +42,7 @@
 #ifndef QWINDOWSDIRECT2DPLATFORMPIXMAP_H
 #define QWINDOWSDIRECT2DPLATFORMPIXMAP_H
 
+#include "qwindowsdirect2dpaintengine.h"
 #include <QtGui/qpa/qplatformpixmap.h>
 #include <QtCore/QScopedPointer>
 
@@ -57,7 +58,7 @@ public:
     QWindowsDirect2DPlatformPixmap(PixelType pixelType);
 
     // We do NOT take ownership of the bitmap through this constructor!
-    QWindowsDirect2DPlatformPixmap(PixelType pixelType, QWindowsDirect2DBitmap *bitmap);
+    QWindowsDirect2DPlatformPixmap(PixelType pixelType, QWindowsDirect2DPaintEngine::Flags flags, QWindowsDirect2DBitmap *bitmap);
     ~QWindowsDirect2DPlatformPixmap();
 
     void resize(int width, int height) Q_DECL_OVERRIDE;
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2dwindow.cpp b/src/plugins/platforms/direct2d/qwindowsdirect2dwindow.cpp
index 37987931b3..f739493c1a 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2dwindow.cpp
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2dwindow.cpp
@@ -308,7 +308,11 @@ void QWindowsDirect2DWindow::setupBitmap()
 
     m_bitmap.reset(new QWindowsDirect2DBitmap(backBufferBitmap.Get(), m_deviceContext.Get()));
 
+    QWindowsDirect2DPaintEngine::Flags flags = QWindowsDirect2DPaintEngine::NoFlag;
+    if (!m_directRendering)
+        flags |= QWindowsDirect2DPaintEngine::UseGrayscaleAntialiasing;
     QWindowsDirect2DPlatformPixmap *pp = new QWindowsDirect2DPlatformPixmap(QPlatformPixmap::PixmapType,
+                                                                            flags,
                                                                             m_bitmap.data());
     m_pixmap.reset(new QPixmap(pp));
 }