Expose the target value in Behaviors

So that nested animation can use it.

Change-Id: Ief40cda1dfe1ad9a38cf0d18fbf34456dc36e2ee
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 26 insertions, 4 deletions

diff --git a/src/quick/util/qquickbehavior.cpp b/src/quick/util/qquickbehavior.cpp
index d024c0099b..76d464e7f8 100644
--- a/src/quick/util/qquickbehavior.cpp
+++ b/src/quick/util/qquickbehavior.cpp
@@ -171,9 +171,28 @@ void QQuickBehavior::setEnabled(bool enabled)
     emit enabledChanged();
 }
 
+/*!
+    \qmlproperty Variant QtQuick::Behavior::targetValue
+
+    This property holds the target value of the property being controlled by the Behavior.
+    This value is set by the Behavior before the animation is started.
+
+    \since QtQuick 2.13
+*/
+QVariant QQuickBehavior::targetValue() const
+{
+    Q_D(const QQuickBehavior);
+    return d->targetValue;
+}
+
 void QQuickBehavior::write(const QVariant &value)
 {
     Q_D(QQuickBehavior);
+    const bool targetValueHasChanged = d->targetValue != value;
+    if (targetValueHasChanged) {
+        d->targetValue = value;
+        emit targetValueChanged(); // emitting the signal here should allow
+    }                              // d->enabled to change if scripted by the user.
     bool bypass = !d->enabled || !d->finalized || QQmlEnginePrivate::designerMode();
     if (!bypass)
         qmlExecuteDeferred(this);
@@ -181,16 +200,13 @@ void QQuickBehavior::write(const QVariant &value)
         if (d->animationInstance)
             d->animationInstance->stop();
         QQmlPropertyPrivate::write(d->property, value, QQmlPropertyData::BypassInterceptor | QQmlPropertyData::DontRemoveBinding);
-        d->targetValue = value;
         return;
     }
 
     bool behaviorActive = d->animation->isRunning();
-    if (behaviorActive && value == d->targetValue)
+    if (behaviorActive && !targetValueHasChanged)
         return;
 
-    d->targetValue = value;
-
     if (d->animationInstance
             && (d->animationInstance->duration() != -1
                 || d->animationInstance->isRenderThreadProxy())
diff --git a/src/quick/util/qquickbehavior_p.h b/src/quick/util/qquickbehavior_p.h
index f939597d15..80a51d77af 100644
--- a/src/quick/util/qquickbehavior_p.h
+++ b/src/quick/util/qquickbehavior_p.h
@@ -69,6 +69,7 @@ class Q_QUICK_PRIVATE_EXPORT QQuickBehavior : public QObject, public QQmlPropert
     Q_CLASSINFO("DefaultProperty", "animation")
     Q_PROPERTY(QQuickAbstractAnimation *animation READ animation WRITE setAnimation)
     Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
+    Q_PROPERTY(QVariant targetValue READ targetValue NOTIFY targetValueChanged REVISION 13)
     Q_CLASSINFO("DeferredPropertyNames", "animation")
 
 public:
@@ -84,8 +85,11 @@ public:
     bool enabled() const;
     void setEnabled(bool enabled);
 
+    QVariant targetValue() const;
+
 Q_SIGNALS:
     void enabledChanged();
+    void targetValueChanged();
 
 private Q_SLOTS:
     void componentFinalized();
diff --git a/src/quick/util/qquickutilmodule.cpp b/src/quick/util/qquickutilmodule.cpp
index 31d4d4c437..5147ebc6f6 100644
--- a/src/quick/util/qquickutilmodule.cpp
+++ b/src/quick/util/qquickutilmodule.cpp
@@ -135,4 +135,6 @@ void QQuickUtilModule::defineModule()
 
     qmlRegisterUncreatableType<QQuickAbstractAnimation, 12>("QtQuick", 2, 12, "Animation",
         QQuickAbstractAnimation::tr("Animation is an abstract class"));
+    // 5.13
+    qmlRegisterType<QQuickBehavior, 13>("QtQuick", 2, 13, "Behavior");
 }