Revert "QQuickRectangle: Optimize setGradient"

This reverts commit 9709d04ba7787c853a1ddbeed0347eab27c0924f.

We changed this from using a signal for notification to using parenting. But
this cannot be done for two related reasons: the first:

    QtObject {
        property Gradient someGradient: Gradient {
            id: someGradient
        }
    }
    ...
    Rectangle {
        gradient: someGradient
    }

... should work, and no longer did, because the Gradient's parent was
the QtObject, not the Rectangle it was tied to. And secondly:

    Rectangle {
        id: rectOne
        gradient: Gradient {
            id: someGradient
        }
    }
    Rectangle {
        id: rectTwo
        gradient: someGradient
    }

... also didn't work anymore, as the Gradient was only notifying a
single Item about changes to it.

The easiest way to fix this is to just revert back to using a signal
connection.

This also caused problems in qtquickcontrols autotests.

Change-Id: Ic07dd02e9920596d0c047bfc23995b3be8c96c49
Task-number: QTBUG-60268
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

6 files changed, 133 insertions, 2 deletions

diff --git a/src/quick/items/qquickrectangle.cpp b/src/quick/items/qquickrectangle.cpp
index 0c532bcd4c..65284eb532 100644
--- a/src/quick/items/qquickrectangle.cpp
+++ b/src/quick/items/qquickrectangle.cpp
@@ -1,6 +1,5 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 Crimson AS <info@crimson.no>
 ** Copyright (C) 2016 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
@@ -270,9 +269,11 @@ QGradientStops QQuickGradient::gradientStops() const
 
 void QQuickGradient::doUpdate()
 {
-    static_cast<QQuickItem*>(parent())->update();
+    emit updated();
 }
 
+int QQuickRectanglePrivate::doUpdateSlotIdx = -1;
+
 /*!
     \qmltype Rectangle
     \instantiates QQuickRectangle
@@ -326,6 +327,11 @@ QQuickRectangle::QQuickRectangle(QQuickItem *parent)
     setFlag(ItemHasContents);
 }
 
+void QQuickRectangle::doUpdate()
+{
+    update();
+}
+
 /*!
     \qmlproperty bool QtQuick::Rectangle::antialiasing
 
@@ -390,7 +396,16 @@ 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();
 }
 
diff --git a/src/quick/items/qquickrectangle_p.h b/src/quick/items/qquickrectangle_p.h
index 627f778e44..724a06013c 100644
--- a/src/quick/items/qquickrectangle_p.h
+++ b/src/quick/items/qquickrectangle_p.h
@@ -129,6 +129,9 @@ public:
 
     QGradientStops gradientStops() const;
 
+Q_SIGNALS:
+    void updated();
+
 private:
     void doUpdate();
 
@@ -169,6 +172,9 @@ Q_SIGNALS:
 protected:
     QSGNode *updatePaintNode(QSGNode *, UpdatePaintNodeData *) Q_DECL_OVERRIDE;
 
+private Q_SLOTS:
+    void doUpdate();
+
 private:
     Q_DISABLE_COPY(QQuickRectangle)
     Q_DECLARE_PRIVATE(QQuickRectangle)
diff --git a/src/quick/items/qquickrectangle_p_p.h b/src/quick/items/qquickrectangle_p_p.h
index e771beec87..3c1aaf7661 100644
--- a/src/quick/items/qquickrectangle_p_p.h
+++ b/src/quick/items/qquickrectangle_p_p.h
@@ -76,6 +76,7 @@ public:
     QQuickGradient *gradient;
     QQuickPen *pen;
     qreal radius;
+    static int doUpdateSlotIdx;
 };
 
 QT_END_NAMESPACE
diff --git a/tests/auto/quick/qquickrectangle/data/gradient-multiple.qml b/tests/auto/quick/qquickrectangle/data/gradient-multiple.qml
new file mode 100644
index 0000000000..d58c857008
--- /dev/null
+++ b/tests/auto/quick/qquickrectangle/data/gradient-multiple.qml
@@ -0,0 +1,30 @@
+import QtQuick 2.0
+
+Item {
+    property alias firstRectangle: r1
+    property alias secondRectangle: r2
+    Rectangle {
+        id: r1
+        gradient: someObject.someGradient
+        anchors.fill: parent
+    }
+    Rectangle {
+        id: r2
+        gradient: someObject.someGradient
+        anchors.fill: parent
+    }
+
+    function changeGradient() {
+        firstStop.color = "red"
+        secondStop.color = "blue"
+    }
+
+    QtObject {
+        id: someObject
+        property Gradient someGradient: Gradient {
+            GradientStop { id: firstStop; position: 0.0; color: "gray" }
+            GradientStop { id: secondStop; position: 1.0; color: "white" }
+        }
+    }
+}
+
diff --git a/tests/auto/quick/qquickrectangle/data/gradient-separate.qml b/tests/auto/quick/qquickrectangle/data/gradient-separate.qml
new file mode 100644
index 0000000000..8ae3f3296b
--- /dev/null
+++ b/tests/auto/quick/qquickrectangle/data/gradient-separate.qml
@@ -0,0 +1,20 @@
+import QtQuick 2.0
+
+Rectangle {
+
+    function changeGradient() {
+        firstStop.color = "red"
+        secondStop.color = "blue"
+    }
+
+    QtObject {
+        id: someObject
+        property Gradient someGradient: Gradient {
+            GradientStop { id: firstStop; position: 0.0; color: "gray" }
+            GradientStop { id: secondStop; position: 1.0; color: "white" }
+        }
+    }
+
+    gradient: someObject.someGradient
+}
+
diff --git a/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp b/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp
index 65c7e387a0..0d79592e37 100644
--- a/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp
+++ b/tests/auto/quick/qquickrectangle/tst_qquickrectangle.cpp
@@ -32,6 +32,7 @@
 #include <QtQml/qqmlengine.h>
 #include <QtQml/qqmlcomponent.h>
 #include <QtQuick/qquickview.h>
+#include <private/qquickitem_p.h>
 #include <private/qquickrectangle_p.h>
 
 #include "../../shared/util.h"
@@ -46,6 +47,8 @@ private slots:
     void color();
     void gradient();
     void gradient_border();
+    void gradient_separate();
+    void gradient_multiple();
     void antialiasing();
 
 private:
@@ -111,6 +114,62 @@ void tst_qquickrectangle::gradient_border()
     QVERIFY(QTest::qWaitForWindowExposed(&view));
 }
 
+// A gradient not defined inline with the Rectangle using it should still change
+// that Rectangle.
+void tst_qquickrectangle::gradient_separate()
+{
+    QQuickView view;
+    view.setSource(testFileUrl("gradient-separate.qml"));
+    view.show();
+
+    QVERIFY(QTest::qWaitForWindowExposed(&view));
+
+    QQuickRectangle *rect = qobject_cast<QQuickRectangle*>(view.rootObject());
+    QVERIFY(rect);
+
+    // Start off clean
+    QQuickItemPrivate *rectPriv = QQuickItemPrivate::get(rect);
+    bool isDirty = rectPriv->dirtyAttributes & QQuickItemPrivate::Content;
+    QVERIFY(!isDirty);
+
+    QMetaObject::invokeMethod(rect, "changeGradient");
+
+    // Changing the gradient should have scheduled an update of the item.
+    isDirty = rectPriv->dirtyAttributes & QQuickItemPrivate::Content;
+    QVERIFY(isDirty);
+}
+
+// When a gradient is changed, every Rectangle connected to it must update.
+void tst_qquickrectangle::gradient_multiple()
+{
+    QQuickView view;
+    view.setSource(testFileUrl("gradient-multiple.qml"));
+    view.show();
+
+    QVERIFY(QTest::qWaitForWindowExposed(&view));
+
+    QQuickRectangle *firstRect = qobject_cast<QQuickRectangle*>(view.rootObject()->property("firstRectangle").value<QObject*>());
+    QQuickRectangle *secondRect = qobject_cast<QQuickRectangle*>(view.rootObject()->property("secondRectangle").value<QObject*>());
+    QVERIFY(firstRect);
+    QVERIFY(secondRect);
+
+    // Start off clean
+    QQuickItemPrivate *firstRectPriv = QQuickItemPrivate::get(firstRect);
+    QQuickItemPrivate *secondRectPriv = QQuickItemPrivate::get(secondRect);
+    bool firstIsDirty = firstRectPriv->dirtyAttributes & QQuickItemPrivate::Content;
+    bool secondIsDirty = secondRectPriv->dirtyAttributes & QQuickItemPrivate::Content;
+    QVERIFY(!firstIsDirty);
+    QVERIFY(!secondIsDirty);
+
+    QMetaObject::invokeMethod(view.rootObject(), "changeGradient");
+
+    // Changing the gradient should have scheduled an update of both items
+    firstIsDirty = firstRectPriv->dirtyAttributes & QQuickItemPrivate::Content;
+    secondIsDirty = secondRectPriv->dirtyAttributes & QQuickItemPrivate::Content;
+    QVERIFY(firstIsDirty);
+    QVERIFY(secondIsDirty);
+}
+
 void tst_qquickrectangle::antialiasing()
 {
     QQmlComponent component(&engine);