Add SmoothedFollow element to qml

The SmoothedFollow is the same as the old EaseFollow, so it's not an
animation, but its main use case is to be used as a property value
source to automatically follow the 'to' property, as in the example below.

Rectangle {
    color: "green"
    width: 60; height: 60;
    SmoothedFollow on x { to: rect1.x - 5; velocity: 200 }
    SmoothedFollow on y { to: rect1.y - 5; velocity: 200 }
}

This element shares the internal implementation with SmoothedAnimation,
both providing the same easing function, but with SmoothedFollow it's
easier to set a start value to animate intially and then start to follow,
while SmoothedAnimation is still convenient for using inside Behaviors
and Transitions.

Reviewed-by: Michael Brasser

4 files changed, 416 insertions, 0 deletions

diff --git a/src/declarative/util/qdeclarativesmoothedfollow.cpp b/src/declarative/util/qdeclarativesmoothedfollow.cpp
new file mode 100644
index 0000000..63c9618
--- /dev/null
+++ b/src/declarative/util/qdeclarativesmoothedfollow.cpp
@@ -0,0 +1,299 @@
+/****************************************************************************
+**
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qdeclarativesmoothedfollow_p.h"
+#include "qdeclarativesmoothedanimation_p_p.h"
+
+#include <private/qobject_p.h>
+#include <QtCore/qnumeric.h>
+
+#include "qdeclarativeglobal_p.h"
+
+
+QT_BEGIN_NAMESPACE
+
+class QDeclarativeSmoothedFollowPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QDeclarativeSmoothedFollow)
+public:
+    QDeclarativeSmoothedFollowPrivate();
+
+    bool enabled;
+    QSmoothedAnimation *anim;
+};
+
+/*!
+    \qmlclass SmoothedFollow QDeclarativeSmoothedFollow
+    \since 4.7
+    \inherits NumberAnimation
+    \brief The SmoothedFollow element allows a property to smoothly track a value.
+
+    The SmoothedFollow animates a property's value to a set target value
+    using an ease in/out quad easing curve.  If the animation is restarted
+    with a different target value, the easing curves used to animate to the old
+    and the new target values are smoothly spliced together to avoid any obvious
+    visual glitches by maintaining the current velocity.
+
+    The property animation is configured by setting the velocity at which the
+    animation should occur, or the duration that the animation should take.
+    If both a velocity and a duration are specified, the one that results in
+    the quickest animation is chosen for each change in the target value.
+
+    For example, animating from 0 to 800 will take 4 seconds if a velocity
+    of 200 is set, will take 8 seconds with a duration of 8000 set, and will
+    take 4 seconds with both a velocity of 200 and a duration of 8000 set.
+    Animating from 0 to 20000 will take 10 seconds if a velocity of 200 is set,
+    will take 8 seconds with a duration of 8000 set, and will take 8 seconds
+    with both a velocity of 200 and a duration of 8000 set.
+
+    The follow example shows one rectangle tracking the position of another.
+\code
+import Qt 4.6
+
+Rectangle {
+    width: 800; height: 600; color: "blue"
+
+    Rectangle {
+        color: "green"
+        width: 60; height: 60;
+        SmoothedFollow on x { to: rect1.x - 5; velocity: 200 }
+        SmoothedFollow on y { to: rect1.y - 5; velocity: 200 }
+    }
+
+    Rectangle {
+        id: rect1
+        color: "red"
+        width: 50; height: 50;
+    }
+
+    focus: true
+    Keys.onRightPressed: rect1.x = rect1.x + 100
+    Keys.onLeftPressed: rect1.x = rect1.x - 100
+    Keys.onUpPressed: rect1.y = rect1.y - 100
+    Keys.onDownPressed: rect1.y = rect1.y + 100
+}
+\endcode
+
+    The default velocity of SmoothedFollow is 200 units/second.  Note that if the range of the
+    value being animated is small, then the velocity will need to be adjusted
+    appropriately.  For example, the opacity of an item ranges from 0 - 1.0.
+    To enable a smooth animation in this range the velocity will need to be
+    set to a value such as 0.5 units/second.  Animating from 0 to 1.0 with a velocity
+    of 0.5 will take 2000 ms to complete.
+
+    \sa SpringFollow
+*/
+
+QDeclarativeSmoothedFollow::QDeclarativeSmoothedFollow(QObject *parent)
+    : QObject(*(new QDeclarativeSmoothedFollowPrivate), parent)
+{
+}
+
+QDeclarativeSmoothedFollow::~QDeclarativeSmoothedFollow()
+{
+}
+
+QDeclarativeSmoothedFollowPrivate::QDeclarativeSmoothedFollowPrivate()
+    : enabled(true), anim(new QSmoothedAnimation)
+{
+    Q_Q(QDeclarativeSmoothedFollow);
+    QDeclarative_setParent_noEvent(anim, q);
+}
+
+/*!
+    \qmlproperty enumeration SmoothedFollow::reversingMode
+
+    Sets how the SmoothedFollow behaves if an animation direction is reversed.
+
+    If reversing mode is \c Eased, the animation will smoothly decelerate, and
+    then reverse direction.  If the reversing mode is \c Immediate, the
+    animation will immediately begin accelerating in the reverse direction,
+    begining with a velocity of 0.  If the reversing mode is \c Sync, the
+    property is immediately set to the target value.
+*/
+QDeclarativeSmoothedFollow::ReversingMode QDeclarativeSmoothedFollow::reversingMode() const
+{
+    Q_D(const QDeclarativeSmoothedFollow);
+    return (ReversingMode) d->anim->reversingMode;
+}
+
+void QDeclarativeSmoothedFollow::setReversingMode(ReversingMode m)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+    if (d->anim->reversingMode == (QDeclarativeSmoothedAnimation::ReversingMode) m)
+        return;
+
+    d->anim->reversingMode = (QDeclarativeSmoothedAnimation::ReversingMode) m;
+    emit reversingModeChanged();
+}
+
+/*!
+    \qmlproperty int SmoothedFollow::duration
+
+    This property holds the animation duration, in msecs, used when tracking the source.
+
+    Setting this to -1 (the default) disables the duration value.
+*/
+int QDeclarativeSmoothedFollow::duration() const
+{
+    Q_D(const QDeclarativeSmoothedFollow);
+    return d->anim->userDuration;
+}
+
+void QDeclarativeSmoothedFollow::setDuration(int duration)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+    if (duration == d->anim->duration())
+        return;
+
+    d->anim->userDuration = duration;
+    emit durationChanged();
+}
+
+qreal QDeclarativeSmoothedFollow::velocity() const
+{
+    Q_D(const QDeclarativeSmoothedFollow);
+    return d->anim->velocity;
+}
+
+/*!
+    \qmlproperty qreal SmoothedFollow::velocity
+
+    This property holds the average velocity allowed when tracking the 'to' value.
+
+    The default velocity of SmoothedFollow is 200 units/second.
+
+    Setting this to -1 disables the velocity value.
+*/
+void QDeclarativeSmoothedFollow::setVelocity(qreal v)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+    if (d->anim->velocity == v)
+        return;
+
+    d->anim->velocity = v;
+    emit velocityChanged();
+}
+
+/*!
+    \qmlproperty qreal SmoothedFollow::maximumEasingTime
+
+    This property specifies the maximum time, in msecs, an "eases" during the follow should take.
+    Setting this property causes the velocity to "level out" after at a time.  Setting
+    a negative value reverts to the normal mode of easing over the entire animation
+    duration.
+
+    The default value is -1.
+*/
+int QDeclarativeSmoothedFollow::maximumEasingTime() const
+{
+    Q_D(const QDeclarativeSmoothedFollow);
+    return d->anim->maximumEasingTime;
+}
+
+void QDeclarativeSmoothedFollow::setMaximumEasingTime(int v)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+    d->anim->maximumEasingTime = v;
+    emit maximumEasingTimeChanged();
+}
+
+/*!
+    \qmlproperty real SmoothedFollow::to
+    This property holds the ending value.
+    If not set, then the value defined in the end state of the transition or Behavior.
+*/
+qreal QDeclarativeSmoothedFollow::to() const
+{
+    Q_D(const QDeclarativeSmoothedFollow);
+    return d->anim->to;
+}
+
+void QDeclarativeSmoothedFollow::setTo(qreal t)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+
+    if (qIsNaN(t))
+        return;
+
+    if (d->anim->to == t)
+        return;
+
+    d->anim->to = t;
+
+    if (d->enabled)
+        d->anim->restart();
+}
+
+/*!
+    \qmlproperty bool SmoothedFollow::enabled
+    This property whether this animation should automatically restart when
+    the 'to' property is upated.
+
+    The default value of this property is 'true'.
+*/
+bool QDeclarativeSmoothedFollow::enabled() const
+{
+    Q_D(const QDeclarativeSmoothedFollow);
+    return d->enabled;
+}
+
+void QDeclarativeSmoothedFollow::setEnabled(bool e)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+    if (d->enabled == e)
+        return;
+    d->enabled = e;
+
+    if (d->enabled)
+        d->anim->restart();
+    else
+        d->anim->stop();
+    emit enabledChanged();
+}
+
+void QDeclarativeSmoothedFollow::setTarget(const QDeclarativeProperty &t)
+{
+    Q_D(QDeclarativeSmoothedFollow);
+    d->anim->target = t;
+}
+
+QT_END_NAMESPACE
diff --git a/src/declarative/util/qdeclarativesmoothedfollow_p.h b/src/declarative/util/qdeclarativesmoothedfollow_p.h
new file mode 100644
index 0000000..d860052
--- /dev/null
+++ b/src/declarative/util/qdeclarativesmoothedfollow_p.h
@@ -0,0 +1,113 @@
+/****************************************************************************
+**
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QDECLARATIVESMOOTHEDFOLLOW_H
+#define QDECLARATIVESMOOTHEDFOLLOW_H
+
+#include <qdeclarative.h>
+#include <qdeclarativepropertyvaluesource.h>
+
+#include <QtCore/qobject.h>
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+QT_MODULE(Declarative)
+
+class QDeclarativeProperty;
+class QDeclarativeSmoothedFollowPrivate;
+class Q_DECLARATIVE_EXPORT QDeclarativeSmoothedFollow : public QObject,
+                                                        public QDeclarativePropertyValueSource
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QDeclarativeSmoothedFollow)
+    Q_INTERFACES(QDeclarativePropertyValueSource)
+    Q_ENUMS(ReversingMode)
+
+    Q_PROPERTY(qreal to READ to WRITE setTo NOTIFY toChanged)
+    Q_PROPERTY(qreal velocity READ velocity WRITE setVelocity NOTIFY velocityChanged)
+    Q_PROPERTY(int duration READ duration WRITE setDuration NOTIFY durationChanged)
+    Q_PROPERTY(ReversingMode reversingMode READ reversingMode WRITE setReversingMode NOTIFY reversingModeChanged)
+    Q_PROPERTY(qreal maximumEasingTime READ maximumEasingTime WRITE setMaximumEasingTime NOTIFY maximumEasingTimeChanged)
+    Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
+
+public:
+    enum ReversingMode { Eased, Immediate, Sync };
+
+    QDeclarativeSmoothedFollow(QObject *parent = 0);
+    ~QDeclarativeSmoothedFollow();
+
+    qreal to() const;
+    void setTo(qreal);
+
+    ReversingMode reversingMode() const;
+    void setReversingMode(ReversingMode);
+
+    int duration() const;
+    void setDuration(int);
+
+    qreal velocity() const;
+    void setVelocity(qreal);
+
+    int maximumEasingTime() const;
+    void setMaximumEasingTime(int);
+
+    bool enabled() const;
+    void setEnabled(bool);
+
+    virtual void setTarget(const QDeclarativeProperty &);
+
+Q_SIGNALS:
+    void velocityChanged();
+    void durationChanged();
+    void reversingModeChanged();
+    void maximumEasingTimeChanged();
+    void enabledChanged();
+};
+
+QT_END_NAMESPACE
+
+QML_DECLARE_TYPE(QDeclarativeSmoothedFollow);
+
+QT_END_HEADER
+
+#endif // QDECLARATIVESMOOTHEDFOLLOW_H
diff --git a/src/declarative/util/qdeclarativeutilmodule.cpp b/src/declarative/util/qdeclarativeutilmodule.cpp
index 218a90b..b9f1abb 100644
--- a/src/declarative/util/qdeclarativeutilmodule.cpp
+++ b/src/declarative/util/qdeclarativeutilmodule.cpp
@@ -46,6 +46,7 @@
 #include "private/qdeclarativebind_p.h"
 #include "private/qdeclarativeconnections_p.h"
 #include "private/qdeclarativesmoothedanimation_p.h"
+#include "private/qdeclarativesmoothedfollow_p.h"
 #include "private/qdeclarativefontloader_p.h"
 #include "private/qdeclarativelistaccessor_p.h"
 #include "private/qdeclarativelistmodel_p.h"
@@ -80,6 +81,7 @@ void QDeclarativeUtilModule::defineModule()
     qmlRegisterType<QDeclarativeColorAnimation>("Qt",4,6,"ColorAnimation");
     qmlRegisterType<QDeclarativeConnections>("Qt",4,6,"Connections");
     qmlRegisterType<QDeclarativeSmoothedAnimation>("Qt",4,6,"SmoothedAnimation");
+    qmlRegisterType<QDeclarativeSmoothedFollow>("Qt",4,6,"SmoothedFollow");
     qmlRegisterType<QDeclarativeFontLoader>("Qt",4,6,"FontLoader");
     qmlRegisterType<QDeclarativeListElement>("Qt",4,6,"ListElement");
     qmlRegisterType<QDeclarativeNumberAnimation>("Qt",4,6,"NumberAnimation");
diff --git a/src/declarative/util/util.pri b/src/declarative/util/util.pri
index 4163596..f20bba1 100644
--- a/src/declarative/util/util.pri
+++ b/src/declarative/util/util.pri
@@ -9,6 +9,7 @@ SOURCES += \
     $$PWD/qdeclarativesystempalette.cpp \
     $$PWD/qdeclarativespringfollow.cpp \
     $$PWD/qdeclarativesmoothedanimation.cpp \
+    $$PWD/qdeclarativesmoothedfollow.cpp \
     $$PWD/qdeclarativestate.cpp\
     $$PWD/qdeclarativetransitionmanager.cpp \
     $$PWD/qdeclarativestateoperations.cpp \
@@ -38,6 +39,7 @@ HEADERS += \
     $$PWD/qdeclarativesystempalette_p.h \
     $$PWD/qdeclarativespringfollow_p.h \
     $$PWD/qdeclarativesmoothedanimation_p.h \
+    $$PWD/qdeclarativesmoothedfollow_p.h \
     $$PWD/qdeclarativesmoothedanimation_p_p.h \
     $$PWD/qdeclarativestate_p.h\
     $$PWD/qdeclarativestateoperations_p.h \