QQuickRectangle: Optimize setGradient

Similarly to the QQuickPen optimization, we can avoid a signal
connection by using the parent pointer of the QQuickGradient.

This improves qmlbench's delegates_rect_gradient.qml by ~6% for me:
    Before: 300.6  frames; using  samples; MedianAll=301; StdDev=4.61519, CoV=0.01535
    After: 320.4  frames; using  samples; MedianAll=321; StdDev=1.94936, CoV=0.00608414

Again, hopefully, the resulting lessening in allocations and improvement
in performance will help stabilize the benchmark a little on some
systems, as well as the improvement to performance and memory use.

Change-Id: Id8e0399f5a4a0ef55d7fc9b8f100af229f389ddd
Reviewed-by: Gunnar Sletta <gunnar@crimson.no>
Reviewed-by: Michael Brasser <michael.brasser@live.com>

1 files changed, 2 insertions, 17 deletions

diff --git a/src/quick/items/qquickrectangle.cpp b/src/quick/items/qquickrectangle.cpp
index 7d8e4de1c0..27086c889b 100644
--- a/src/quick/items/qquickrectangle.cpp
+++ b/src/quick/items/qquickrectangle.cpp
@@ -1,5 +1,6 @@
 /****************************************************************************
 **
+** Copyright (C) 2017 Crimson AS <info@crimson.no>
 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
@@ -269,11 +270,9 @@ QGradientStops QQuickGradient::gradientStops() const
 
 void QQuickGradient::doUpdate()
 {
-    emit updated();
+    static_cast<QQuickItem*>(parent())->update();
 }
 
-int QQuickRectanglePrivate::doUpdateSlotIdx = -1;
-
 /*!
     \qmltype Rectangle
     \instantiates QQuickRectangle
@@ -327,11 +326,6 @@ QQuickRectangle::QQuickRectangle(QQuickItem *parent)
     setFlag(ItemHasContents);
 }
 
-void QQuickRectangle::doUpdate()
-{
-    update();
-}
-
 /*!
     \qmlproperty bool QtQuick::Rectangle::antialiasing
 
@@ -396,16 +390,7 @@ void QQuickRectangle::setGradient(QQuickGradient *gradient)
     Q_D(QQuickRectangle);
     if (d->gradient == gradient)
         return;
-    static int updatedSignalIdx = -1;
-    if (updatedSignalIdx < 0)
-        updatedSignalIdx = QMetaMethod::fromSignal(&QQuickGradient::updated).methodIndex();
-    if (d->doUpdateSlotIdx < 0)
-        d->doUpdateSlotIdx = QQuickRectangle::staticMetaObject.indexOfSlot("doUpdate()");
-    if (d->gradient)
-        QMetaObject::disconnect(d->gradient, updatedSignalIdx, this, d->doUpdateSlotIdx);
     d->gradient = gradient;
-    if (d->gradient)
-        QMetaObject::connect(d->gradient, updatedSignalIdx, this, d->doUpdateSlotIdx);
     update();
 }