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>

1 files changed, 4 insertions, 0 deletions

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));
 }