Make QSGLayer::grab work correctly in software renderer

Fix three separate issues:
1. It was possible that the QSGSoftwarePixmapRenderer's
   background image's rectangle was set to a non-normalized
   rectangle. That would have led to the damage area detection
   creating an empty QRegion for the damage area and
   QQuickItem::grabToImage would grab an empty image.
2. The QSGSoftwarePixmapRenderer was rendering the image vertically
   mirrored compared to what its equivalent in the OpenGL backend
   was doing. Therefore QSGLayer::grab was vertically mirrored, too,
   so QQuickItem::grabToImage would grab a mirrored image, too.
   Additionally QSGSoftwareInternalImageNode (used by
   QQuickShaderEffectSource) now has to mirror its internal texture
   if that one is a QSGSoftwareLayer.
3. QSGSoftwareInternalImageNode (used by QQuickShaderEffectSource)
   was not updating correctly when mirroring (with the fix for 2
   also in case of a QSGSoftwareLayer as texture).

Related to QTBUG-63185 and QTBUG-65975.

Change-Id: I0d0ead7fb1c839a8ff427ff7881d8a881e538409
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/quick/scenegraph/adaptations/software/qsgsoftwarepixmaprenderer.cpp b/src/quick/scenegraph/adaptations/software/qsgsoftwarepixmaprenderer.cpp
index 303f98c801..bb4afc8301 100644
--- a/src/quick/scenegraph/adaptations/software/qsgsoftwarepixmaprenderer.cpp
+++ b/src/quick/scenegraph/adaptations/software/qsgsoftwarepixmaprenderer.cpp
@@ -79,7 +79,7 @@ void QSGSoftwarePixmapRenderer::render(QPaintDevice *target)
     QElapsedTimer renderTimer;
 
     // Setup background item
-    setBackgroundRect(m_projectionRect);
+    setBackgroundRect(m_projectionRect.normalized());
     setBackgroundColor(clearColor());
 
     renderTimer.start();