BT: Revert "Fixes: Don't fill the pixmap because we will copy the cache into it."

This reverts commit 0985805ab3c7de5b15c115a98afb15944b6d93b9.

The Elastic Nodes example shows a black background for the cache pixmap
if the call to fill isn't there. Alexis and I both agree that it makes
no sense that we fill the pixmap with transparent pixels instead of
just drawing with QPainter::CompositionMode_Source, but since this
regression was introduced after 4.5.0 was released we must revert before
we investigate further.

Reviewed-by: Alexis
(cherry picked from commit 183cb6052c45d7c83e36c78da4e2c59c768209c7)

1 files changed, 3 insertions, 1 deletions

diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 5cd69b3..0012d98 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4890,9 +4890,11 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
             if (newCacheIndent != deviceData->cacheIndent || deviceRect.size() != pix.size()) {
                 QPoint diff = newCacheIndent - deviceData->cacheIndent;
                 QPixmap newPix(deviceRect.size());
+                // ### Investigate removing this fill (test with Plasma and
+                // graphicssystem raster).
+                newPix.fill(Qt::transparent);
                 if (!pix.isNull()) {
                     QPainter newPixPainter(&newPix);
-                    newPixPainter.setCompositionMode(QPainter::CompositionMode_Source);
                     newPixPainter.drawPixmap(-diff, pix);
                     newPixPainter.end();
                 }