path: root/src/gui/painting/qplatformbackingstore.h
diff options
authorLaszlo Agocs <>2014-08-13 10:05:52 +0200
committerJørgen Lind <>2014-08-13 16:14:19 +0200
commit5621a7c5014ac337d41a00ca8f53f172bd17b792 (patch)
tree9dd679d1ea0319c989377a0e940b152e0a169350 /src/gui/painting/qplatformbackingstore.h
parent6c3c1a4cb8e4973b8e603edfbe608e1b1587f3f2 (diff)
Fix composition for windows with alpha
While we will cover the entire surface with our textured quads, the clear is still necessary in order to make top-levels with TranslucentBackground render correctly: We don't want to blend transparent areas with undefined content that is in the surface's framebuffer. Blending is problematic for alpha values. We now prevent the blended alpha from being written out. This ensures that in examples like qquickviewcomparison, where the backingstore image contains an alpha of 0.5 while the QQuickWidget texture 1.0, the result is still an alpha value of 1.0 in the final image. Writing out an alpha of 0.5 would break on systems where windows get an alpha buffer by default. hellogl2 can now take a --transparent parameter which makes the QOpenGLWidget being cleared to transparent in order to verify it works in combination with Qt::WA_TranslucentBackground. The swapped red and blue problem is also corrected. RGBA8888 does not need swizzling. The only format that needs this is RGB32. Task-number: QTBUG-40716 Change-Id: I54a9fd3a91a1b59575b38cdb908835315514e40f Reviewed-by: Jørgen Lind <>
Diffstat (limited to 'src/gui/painting/qplatformbackingstore.h')
1 files changed, 4 insertions, 2 deletions
diff --git a/src/gui/painting/qplatformbackingstore.h b/src/gui/painting/qplatformbackingstore.h
index fe0f460ed9..2c183f6d6f 100644
--- a/src/gui/painting/qplatformbackingstore.h
+++ b/src/gui/painting/qplatformbackingstore.h
@@ -110,9 +110,11 @@ public:
// offset is the (child) window's offset in relation to the window surface.
virtual void flush(QWindow *window, const QRegion &region, const QPoint &offset) = 0;
#ifndef QT_NO_OPENGL
- virtual void composeAndFlush(QWindow *window, const QRegion &region, const QPoint &offset, QPlatformTextureList *textures, QOpenGLContext *context);
+ virtual void composeAndFlush(QWindow *window, const QRegion &region, const QPoint &offset,
+ QPlatformTextureList *textures, QOpenGLContext *context,
+ bool translucentBackground);
virtual QImage toImage() const;
- virtual GLuint toTexture(const QRegion &dirtyRegion, QSize *textureSize) const;
+ virtual GLuint toTexture(const QRegion &dirtyRegion, QSize *textureSize, bool *needsSwizzle) const;
virtual void resize(const QSize &size, const QRegion &staticContents) = 0;