QWidget: set brushOrigin in paintBackground() only when really needed

When painting the background for a QAbstractScrollArea, the brushOrigin
was calculated for every brush type although it was not needed. Since
this can be very time consuming (e.g for a QTreeView with non-uniform
row sizes) it should be avoided when possible.
Therefore check if the brush is a texture and skip the calculation if
it is not the case. Also do not restore the old brushOrigin since the
painter is not used at all afterwards.

Task-number: QTBUG-61763
Change-Id: I66cbe1b796cb5cad4c78e656fb86d199d8e4bde9
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index 20c4a682ed..c8eaabf8e2 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -400,6 +400,7 @@ public:
 
     void setUpdatesEnabled_helper(bool );
 
+    bool updateBrushOrigin(QPainter *, const QBrush &brush) const;
     void paintBackground(QPainter *, const QRegion &, int flags = DrawAsRoot) const;
     bool isAboutToShow() const;
     QRegion prepareToRender(const QRegion &region, QWidget::RenderFlags renderFlags);