Fix SpringAnimation in Behavior when current value is set.

Fixes regression introduced by d489f2f6549a86b3949004d1c8ec68487fc2adb7.
We now only avoid running the animation if the Behavior wasn't already
mid-animation. This ensure correct behavior for SpringAnimation, and
also correct state for 'running'.

Task-number: QTBUG-21549
Change-Id: I0f97813294cca22fb7a273e222fa0549c6de9ca7
Reviewed-by: Alan Alpert (Personal) <416365416c@gmail.com>

3 files changed, 119 insertions, 20 deletions

diff --git a/src/quick/util/qquickbehavior.cpp b/src/quick/util/qquickbehavior.cpp
index d649f9ff97..407b80915d 100644
--- a/src/quick/util/qquickbehavior.cpp
+++ b/src/quick/util/qquickbehavior.cpp
@@ -185,7 +185,8 @@ void QQuickBehavior::write(const QVariant &value)
         return;
     }
 
-    if (d->animation->isRunning() && value == d->targetValue)
+    bool behaviorActive = d->animation->isRunning();
+    if (behaviorActive && value == d->targetValue)
         return;
 
     d->targetValue = value;
@@ -201,7 +202,10 @@ void QQuickBehavior::write(const QVariant &value)
     // to the item, so we need to read the value after.
     const QVariant &currentValue = d->property.read();
 
-    if (d->targetValue == currentValue) {
+    // Don't unnecessarily wake up the animation system if no real animation
+    // is needed (value has not changed). If the Behavior was already
+    // running, let it continue as normal to ensure correct behavior and state.
+    if (!behaviorActive && d->targetValue == currentValue) {
         QQmlPropertyPrivate::write(d->property, value, QQmlPropertyPrivate::BypassInterceptor | QQmlPropertyPrivate::DontRemoveBinding);
         return;
     }
diff --git a/tests/auto/quick/qquickbehaviors/data/qtbug21549-2.qml b/tests/auto/quick/qquickbehaviors/data/qtbug21549-2.qml
new file mode 100644
index 0000000000..9cf22dc7a1
--- /dev/null
+++ b/tests/auto/quick/qquickbehaviors/data/qtbug21549-2.qml
@@ -0,0 +1,71 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
+**     of its contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.0
+
+Item {
+    width: 400; height: 400
+
+    property alias animRunning: springAnim.running
+
+    Rectangle {
+        objectName: "myRect"
+        color: "green"
+        width: 20; height: 20
+
+        property bool triggered: false
+
+        onXChanged: {
+            if (!triggered && x > 50 && x < 80) {
+                triggered = true
+                x = x //set same value
+            }
+        }
+
+        Behavior on x {
+            SpringAnimation {
+                id: springAnim
+                spring: 3
+                damping: 0.2
+                mass: .5
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickbehaviors/tst_qquickbehaviors.cpp b/tests/auto/quick/qquickbehaviors/tst_qquickbehaviors.cpp
index 8ec76c94e9..5deda2d96b 100644
--- a/tests/auto/quick/qquickbehaviors/tst_qquickbehaviors.cpp
+++ b/tests/auto/quick/qquickbehaviors/tst_qquickbehaviors.cpp
@@ -499,30 +499,54 @@ void tst_qquickbehaviors::multipleChangesToValueType()
 //QTBUG-21549
 void tst_qquickbehaviors::currentValue()
 {
-    QQmlEngine engine;
-    QQmlComponent c(&engine, testFileUrl("qtbug21549.qml"));
-    QQuickItem *item = qobject_cast<QQuickItem*>(c.create());
-    QVERIFY(item);
+    {
+        QQmlEngine engine;
+        QQmlComponent c(&engine, testFileUrl("qtbug21549.qml"));
+        QQuickItem *item = qobject_cast<QQuickItem*>(c.create());
+        QVERIFY(item);
 
-    QQuickRectangle *target = item->findChild<QQuickRectangle*>("myRect");
-    QVERIFY(target);
+        QQuickRectangle *target = item->findChild<QQuickRectangle*>("myRect");
+        QVERIFY(target);
 
-    QCOMPARE(target->x(), qreal(0));
+        QCOMPARE(target->x(), qreal(0));
 
-    target->setProperty("x", 50);
-    QCOMPARE(item->property("behaviorCount").toInt(), 1);
-    QCOMPARE(target->x(), qreal(50));
+        target->setProperty("x", 50);
+        QCOMPARE(item->property("behaviorCount").toInt(), 1);
+        QCOMPARE(target->x(), qreal(50));
 
-    target->setProperty("x", 50);
-    QCOMPARE(item->property("behaviorCount").toInt(), 1);
-    QCOMPARE(target->x(), qreal(50));
+        target->setProperty("x", 50);
+        QCOMPARE(item->property("behaviorCount").toInt(), 1);
+        QCOMPARE(target->x(), qreal(50));
 
-    target->setX(100);
-    target->setProperty("x", 100);
-    QCOMPARE(item->property("behaviorCount").toInt(), 1);
-    QCOMPARE(target->x(), qreal(100));
+        target->setX(100);
+        target->setProperty("x", 100);
+        QCOMPARE(item->property("behaviorCount").toInt(), 1);
+        QCOMPARE(target->x(), qreal(100));
+
+        delete item;
+    }
 
-    delete item;
+    {
+        QQmlEngine engine;
+        QQmlComponent c(&engine, testFileUrl("qtbug21549-2.qml"));
+        QQuickItem *item = qobject_cast<QQuickItem*>(c.create());
+        QVERIFY(item);
+
+        QQuickRectangle *target = item->findChild<QQuickRectangle*>("myRect");
+        QVERIFY(target);
+
+        QCOMPARE(target->x(), qreal(0));
+
+        target->setProperty("x", 100);
+
+        // the spring animation should smoothly transition to the new value triggered
+        // in the QML (which should be between 50 and 80);
+        QTRY_COMPARE(item->property("animRunning").toBool(), true);
+        QTRY_COMPARE(item->property("animRunning").toBool(), false);
+        QVERIFY(target->x() > qreal(50) && target->x() < qreal(80));
+
+        delete item;
+    }
 }
 
 QTEST_MAIN(tst_qquickbehaviors)