Introduce PinchHandler

Similar to PinchArea but with improvements:
- Allows rotating and scaling about an arbitrary point rather than the center
- It's possible to require more than 2 fingers.  E.g. maybe you use
  3 fingers to manage a window, 2 fingers to manipulate content inside.
  This could be achieved with two independent PinchHandlers.

Change-Id: Ifd40cfee115d7bc298378b26a58318bea40a8230
Reviewed-by: Jan Arve Sæther <jan-arve.saether@theqtcompany.com>

7 files changed, 431 insertions, 1 deletions

diff --git a/src/quick/handlers/handlers.pri b/src/quick/handlers/handlers.pri
index 3d7e656071..f32f330d4e 100644
--- a/src/quick/handlers/handlers.pri
+++ b/src/quick/handlers/handlers.pri
@@ -3,6 +3,7 @@ HEADERS += \
     $$PWD/qquickpointerhandler_p.h \
     $$PWD/qquickpointerdevicehandler_p.h \
     $$PWD/qquickmultipointerhandler_p.h \
+    $$PWD/qquickpinchhandler_p.h \
     $$PWD/qquickpointersinglehandler_p.h \
     $$PWD/qquickhandlersmodule_p.h \
     $$PWD/qquickpointerdevicehandler_p.h \
@@ -13,5 +14,6 @@ SOURCES += \
     $$PWD/qquickpointerhandler.cpp \
     $$PWD/qquickpointerdevicehandler.cpp \
     $$PWD/qquickmultipointerhandler.cpp \
+    $$PWD/qquickpinchhandler.cpp \
     $$PWD/qquickpointersinglehandler.cpp \
     $$PWD/qquickhandlersmodule.cpp \
diff --git a/src/quick/handlers/qquickhandlersmodule.cpp b/src/quick/handlers/qquickhandlersmodule.cpp
index 398ca0484f..97d6f1d499 100644
--- a/src/quick/handlers/qquickhandlersmodule.cpp
+++ b/src/quick/handlers/qquickhandlersmodule.cpp
@@ -40,6 +40,7 @@
 #include "qquickhandlersmodule_p.h"
 #include "qquickpointerhandler_p.h"
 #include "qquickdraghandler_p.h"
+#include "qquickpinchhandler_p.h"
 
 static void initResources()
 {
@@ -78,6 +79,7 @@ static void qt_quickhandlers_defineModule(const char *uri, int major, int minor)
     qmlRegisterType<QQuickDragHandler>(uri,major,minor,"DragHandler");
     qmlRegisterUncreatableType<QQuickDragAxis>(uri, major, minor, "DragAxis",
         QQuickDragHandler::tr("DragAxis is only available as a grouped property of DragHandler"));
+    qmlRegisterType<QQuickPinchHandler>(uri,major,minor,"PinchHandler");
 }
 
 void QQuickHandlersModule::defineModule()
diff --git a/src/quick/handlers/qquickpinchhandler.cpp b/src/quick/handlers/qquickpinchhandler.cpp
new file mode 100644
index 0000000000..ddec7eee87
--- /dev/null
+++ b/src/quick/handlers/qquickpinchhandler.cpp
@@ -0,0 +1,201 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qquickpinchhandler_p.h"
+#include <QtQuick/qquickwindow.h>
+#include <private/qsgadaptationlayer_p.h>
+#include <private/qquickitem_p.h>
+#include <private/qguiapplication_p.h>
+#include <private/qquickwindow_p.h>
+#include <QEvent>
+#include <QMouseEvent>
+#include <QDebug>
+#include <qpa/qplatformnativeinterface.h>
+
+QT_BEGIN_NAMESPACE
+
+Q_LOGGING_CATEGORY(lcPinchHandler, "qt.quick.handler.pinch")
+
+/*!
+    \qmltype PinchHandler
+    \instantiates QQuickPinchHandler
+    \inqmlmodule QtQuick
+    \ingroup qtquick-handlers
+    \brief Handler for pinch gestures
+
+    PinchHandler is a handler that is used to interactively rotate and zoom an Item.
+*/
+
+QQuickPinchHandler::QQuickPinchHandler(QObject *parent)
+    : QQuickMultiPointerHandler(parent, 2)
+    , m_startScale(1)
+    , m_startRotation(0)
+    , m_minimumScale(-qInf())
+    , m_maximumScale(qInf())
+    , m_minimumRotation(-qInf())
+    , m_maximumRotation(qInf())
+    , m_pinchOrigin(PinchCenter)
+{
+    connect(this, &QQuickPinchHandler::activeChanged, this, &QQuickPinchHandler::onActiveChanged);
+    connect(this, &QQuickPinchHandler::targetChanged, this, &QQuickPinchHandler::onTargetChanged);
+}
+
+QQuickPinchHandler::~QQuickPinchHandler()
+{
+}
+
+void QQuickPinchHandler::setMinimumScale(qreal minimumScale)
+{
+    if (m_minimumScale == minimumScale)
+        return;
+
+    m_minimumScale = minimumScale;
+    emit minimumScaleChanged();
+}
+
+void QQuickPinchHandler::setMaximumScale(qreal maximumScale)
+{
+    if (m_maximumScale == maximumScale)
+        return;
+
+    m_maximumScale = maximumScale;
+    emit maximumScaleChanged();
+}
+
+void QQuickPinchHandler::setMinimumRotation(qreal minimumRotation)
+{
+    if (m_minimumRotation == minimumRotation)
+        return;
+
+    m_minimumRotation = minimumRotation;
+    emit minimumRotationChanged();
+}
+
+void QQuickPinchHandler::setMaximumRotation(qreal maximumRotation)
+{
+    if (m_maximumRotation == maximumRotation)
+        return;
+
+    m_maximumRotation = maximumRotation;
+    emit maximumRotationChanged();
+}
+
+void QQuickPinchHandler::setPinchOrigin(QQuickPinchHandler::PinchOrigin pinchOrigin)
+{
+    if (m_pinchOrigin == pinchOrigin)
+        return;
+
+    m_pinchOrigin = pinchOrigin;
+    emit pinchOriginChanged();
+}
+
+/*!
+    \qmlproperty QQuickPinchHandler::minimumTouchPoints
+
+    The pinch begins when this number of fingers are pressed.
+    Until then, PinchHandler tracks the positions of any pressed fingers,
+    but if it's an insufficient number, it does not scale or rotate
+    its \l target, and the \l active property will remain false.
+*/
+
+/*!
+    \qmlproperty QQuickPinchHandler::active
+*/
+
+void QQuickPinchHandler::onActiveChanged()
+{
+    if (active()) {
+        m_startScale = m_scaleTransform.xScale(); // TODO incompatible with independent x/y scaling
+        m_startRotation = m_rotationTransform.angle();
+        qCInfo(lcPinchHandler) << "activated with starting scale" << m_startScale << "rotation" << m_startRotation;
+        grabPoints(m_currentPoints);
+    }
+}
+
+void QQuickPinchHandler::onTargetChanged()
+{
+    if (target()) {
+        // TODO if m_target was previously set differently,
+        // does prepending to the new target remove it from the old one?
+        // If not, should we fix that there, or here?
+        m_scaleTransform.prependToItem(target());
+        m_rotationTransform.prependToItem(target());
+    }
+}
+
+void QQuickPinchHandler::handlePointerEventImpl(QQuickPointerEvent *event)
+{
+    Q_UNUSED(event)
+
+    if (Q_UNLIKELY(lcPinchHandler().isDebugEnabled())) {
+        for (QQuickEventPoint *point : qAsConst(m_currentPoints))
+            qCDebug(lcPinchHandler) << point->state() << point->sceneGrabPos() << "->" << point->scenePos();
+    }
+
+    // TODO check m_pinchOrigin: right now it acts like it's set to PinchCenter
+    QPointF startCentroid = startingCentroid();
+    QPointF centroid = touchPointCentroid();
+    QVector3D origin(centroid);
+
+    qreal startDist = averageStartingDistance(startCentroid);
+    qreal dist = averageTouchPointDistance(centroid);
+    qreal zoom = dist / startDist;
+
+    qreal newScale = qBound(m_minimumScale, zoom * m_startScale, m_maximumScale);
+    m_scaleTransform.setOrigin(origin);
+    // TODO optionally allow separate x and y scaling?
+    m_scaleTransform.setXScale(newScale);
+    m_scaleTransform.setYScale(newScale);
+
+    qreal startAngle = averageStartingAngle(startCentroid);
+    qreal angle = averageTouchPointAngle(centroid);
+    qreal angleDelta = startAngle - angle;
+    m_rotationTransform.setOrigin(origin);
+    m_rotationTransform.setAngle(qMin(m_maximumRotation, qMax(m_minimumRotation, m_startRotation + angleDelta)));
+
+    // TODO some translation inadvertently happens; try to hold the chosen pinch origin in place
+
+    qCDebug(lcPinchHandler) << "startCentroid" << startCentroid << "centroid"  << centroid << "dist" << dist << "starting dist" << startDist
+                            << "zoom" << zoom << "startScale" << m_startScale << "startAngle" << startAngle << "angle" << angle
+                            << "scale" << scale() << "rotation" << rotation();
+
+    emit updated();
+}
+
+QT_END_NAMESPACE
diff --git a/src/quick/handlers/qquickpinchhandler_p.h b/src/quick/handlers/qquickpinchhandler_p.h
new file mode 100644
index 0000000000..0a66d5e02e
--- /dev/null
+++ b/src/quick/handlers/qquickpinchhandler_p.h
@@ -0,0 +1,131 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQUICKPINCHHANDLER_H
+#define QQUICKPINCHHANDLER_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qquickitem.h"
+#include "qevent.h"
+#include "qquickmultipointerhandler_p.h"
+#include <private/qquicktranslate_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_AUTOTEST_EXPORT QQuickPinchHandler : public QQuickMultiPointerHandler
+{
+    Q_OBJECT
+    Q_PROPERTY(qreal minimumScale READ minimumScale WRITE setMinimumScale NOTIFY minimumScaleChanged)
+    Q_PROPERTY(qreal maximumScale READ maximumScale WRITE setMaximumScale NOTIFY maximumScaleChanged)
+    Q_PROPERTY(qreal minimumRotation READ minimumRotation WRITE setMinimumRotation NOTIFY minimumRotationChanged)
+    Q_PROPERTY(qreal maximumRotation READ maximumRotation WRITE setMaximumRotation NOTIFY maximumRotationChanged)
+    Q_PROPERTY(PinchOrigin pinchOrigin READ pinchOrigin WRITE setPinchOrigin NOTIFY pinchOriginChanged)
+    Q_PROPERTY(QPointF center READ center NOTIFY updated)
+    Q_PROPERTY(qreal scale READ scale NOTIFY updated)
+    Q_PROPERTY(qreal rotation READ rotation NOTIFY updated)
+
+public:
+    enum PinchOrigin {
+        FirstPoint, PinchCenter, TargetCenter
+    };
+    Q_ENUM(PinchOrigin)
+
+    QQuickPinchHandler(QObject *parent = 0);
+    ~QQuickPinchHandler();
+
+    qreal minimumScale() const { return m_minimumScale; }
+    void setMinimumScale(qreal minimumScale);
+
+    qreal maximumScale() const { return m_maximumScale; }
+    void setMaximumScale(qreal maximumScale);
+
+    qreal minimumRotation() const { return m_minimumRotation; }
+    void setMinimumRotation(qreal minimumRotation);
+
+    qreal maximumRotation() const { return m_maximumRotation; }
+    void setMaximumRotation(qreal maximumRotation);
+
+    PinchOrigin pinchOrigin() const { return m_pinchOrigin; }
+    void setPinchOrigin(PinchOrigin pinchOrigin);
+
+    QPointF center() const { return m_scaleTransform.origin().toPointF(); }
+    qreal scale() const { return m_scaleTransform.xScale(); }
+    qreal rotation() const { return m_rotationTransform.angle(); }
+
+signals:
+    void requiredPointCountChanged();
+    void minimumScaleChanged();
+    void maximumScaleChanged();
+    void minimumRotationChanged();
+    void maximumRotationChanged();
+    void pinchOriginChanged();
+    void updated();
+
+protected:
+    void onActiveChanged();
+    void onTargetChanged();
+    void handlePointerEventImpl(QQuickPointerEvent *event) override;
+
+private:
+    qreal m_startScale;
+    qreal m_startRotation;
+    qreal m_minimumScale;
+    qreal m_maximumScale;
+    qreal m_minimumRotation;
+    qreal m_maximumRotation;
+    PinchOrigin m_pinchOrigin;
+    QQuickScale m_scaleTransform;
+    QQuickRotation m_rotationTransform;
+};
+
+QT_END_NAMESPACE
+
+QML_DECLARE_TYPE(QQuickPinchHandler)
+
+#endif // QQUICKPINCHHANDLER_H
diff --git a/tests/manual/pointer/main.qml b/tests/manual/pointer/main.qml
index efe603c57f..45a339b302 100644
--- a/tests/manual/pointer/main.qml
+++ b/tests/manual/pointer/main.qml
@@ -52,6 +52,7 @@ Window {
         Component.onCompleted: {
             addExample("joystick", "DragHandler: move one item inside another with any pointing device", Qt.resolvedUrl("joystick.qml"))
             addExample("mixer", "mixing console", Qt.resolvedUrl("mixer.qml"))
+            addExample("pinch", "PinchHandler: scale, rotate and drag", Qt.resolvedUrl("pinchHandler.qml"))
         }
     }
 }
diff --git a/tests/manual/pointer/pinchHandler.qml b/tests/manual/pointer/pinchHandler.qml
new file mode 100644
index 0000000000..e4482a249d
--- /dev/null
+++ b/tests/manual/pointer/pinchHandler.qml
@@ -0,0 +1,93 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the manual tests 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 The Qt Company Ltd 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 2.8
+import Qt.labs.handlers 1.0
+
+Rectangle {
+    id: root
+    width: 1024; height: 600
+    color: "black"
+
+    Rectangle {
+        width: 400
+        height: 300
+        color: "lightsteelblue"
+        antialiasing: true
+
+        Text {
+            anchors.centerIn: parent
+            text: "Pinch with 2 fingers to scale & rotate\nDrag with 1 finger\ncurrent rotation " + pinch2.rotation.toFixed(1)
+        }
+
+        DragHandler { objectName: "DragHandler" }
+
+        PinchHandler {
+            id: pinch2
+            objectName: "2-finger pinch"
+            minimumRotation: -45
+            maximumRotation: 45
+            minimumScale: 0.1
+            maximumScale: 10
+            pointDistanceThreshold: 150
+        }
+    }
+
+    Rectangle {
+        x: 512
+        width: 400
+        height: 300
+        color: "wheat"
+        antialiasing: true
+
+        Text {
+            anchors.centerIn: parent
+            text: "Pinch with 3 fingers to scale & rotate\ncurrent rotation " + pinch3.rotation.toFixed(1)
+        }
+
+        PinchHandler {
+            id: pinch3
+            objectName: "3-finger pinch"
+            requiredPointCount: 3
+            minimumScale: 0.1
+            maximumScale: 10
+        }
+    }
+}
diff --git a/tests/manual/pointer/qml.qrc b/tests/manual/pointer/qml.qrc
index b802a73f08..dac6b08b12 100644
--- a/tests/manual/pointer/qml.qrc
+++ b/tests/manual/pointer/qml.qrc
@@ -2,8 +2,8 @@
     <qresource prefix="/">
         <file>main.qml</file>
         <file>joystick.qml</file>
-        <file>main.qml</file>
         <file>mixer.qml</file>
+        <file>pinchHandler.qml</file>
         <file>content/Slider.qml</file>
         <file>resources/mixer-knob.png</file>
         <file>resources/redball.png</file>