Graphics View Optimization: Use a simple style option by default.

QStyleOptionGraphicsItem extends QStyleOption with three values:
1) matrix, 2) levelOfDetail, 3) exposedRect, and they all
involve expensive QTranform operations when calculated. We
pass style option(s) to drawItems() and paint(), but the
extended values are usually not in use. We can therefore gain
quite some nice speedup by making them opt-in with the
QGraphicsItem::ItemUsesExtendedStyleOption flag.

Additionally, QStyleOptionGraphicsItem::levelOfDetail has been
obsoleted, and a new function QStyleOptionGraphicsItem::
levelOfDetailFromTransform(const QTransform &) has been added.

Me and Andreas don't consider this change to be too controversial
even though it changes the behavior.

Auto tests still pass.

Reviewed-by: Andreas

1 files changed, 1 insertions, 0 deletions

diff --git a/src/gui/styles/qstyleoption.h b/src/gui/styles/qstyleoption.h
index 5759a05..eb05324 100644
--- a/src/gui/styles/qstyleoption.h
+++ b/src/gui/styles/qstyleoption.h
@@ -856,6 +856,7 @@ public:
 
     QStyleOptionGraphicsItem();
     QStyleOptionGraphicsItem(const QStyleOptionGraphicsItem &other) : QStyleOption(Version, Type) { *this = other; }
+    static qreal levelOfDetailFromTransform(const QTransform &worldTransform);
 protected:
     QStyleOptionGraphicsItem(int version);
 };