Introduce DragHandler

A handler for dragging Items around by touch or mouse.

Change-Id: Id83fea568095eb6374f3f1abc6f550d81f3731df
Reviewed-by: Jan Arve Sæther <jan-arve.saether@theqtcompany.com>

4 files changed, 298 insertions, 0 deletions

diff --git a/src/quick/handlers/handlers.pri b/src/quick/handlers/handlers.pri
index c91b259107..c337253759 100644
--- a/src/quick/handlers/handlers.pri
+++ b/src/quick/handlers/handlers.pri
@@ -1,10 +1,14 @@
 HEADERS += \
+    $$PWD/qquickdraghandler_p.h \
     $$PWD/qquickpointerhandler_p.h \
     $$PWD/qquickpointerdevicehandler_p.h \
     $$PWD/qquickpointersinglehandler_p.h \
     $$PWD/qquickhandlersmodule_p.h \
+    $$PWD/qquickpointerdevicehandler_p.h \
+    $$PWD/qquickhandlersmodule_p.h \
 
 SOURCES += \
+    $$PWD/qquickdraghandler.cpp \
     $$PWD/qquickpointerhandler.cpp \
     $$PWD/qquickpointerdevicehandler.cpp \
     $$PWD/qquickpointersinglehandler.cpp \
diff --git a/src/quick/handlers/qquickdraghandler.cpp b/src/quick/handlers/qquickdraghandler.cpp
new file mode 100644
index 0000000000..e812b76399
--- /dev/null
+++ b/src/quick/handlers/qquickdraghandler.cpp
@@ -0,0 +1,160 @@
+/****************************************************************************
+**
+** 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 "qquickdraghandler_p.h"
+#include <private/qquickwindow_p.h>
+#include <QDebug>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \qmltype DragHandler
+    \instantiates QQuickDragHandler
+    \inqmlmodule QtQuick
+    \ingroup qtquick-handlers
+    \brief Handler for dragging
+
+    DragHandler is a handler that is used to interactively move an Item.
+
+    At this time, drag-and-drop is not yet supported.
+
+    \sa Drag, MouseArea
+*/
+
+QQuickDragHandler::QQuickDragHandler(QObject *parent)
+    : QQuickPointerSingleHandler(parent)
+    , m_dragging(false)
+{
+}
+
+QQuickDragHandler::~QQuickDragHandler()
+{
+}
+
+void QQuickDragHandler::handleEventPoint(QQuickEventPoint *point)
+{
+    // If there's no target or the target has no parent, we shouldn't be dragging
+    if (!target() || !target()->parentItem())
+        return;
+    point->setAccepted();
+    switch (point->state()) {
+    case QQuickEventPoint::Pressed:
+        m_startPos = target()->mapToScene(QPointF());
+        break;
+    case QQuickEventPoint::Updated: {
+        QPointF delta = point->scenePos() - point->scenePressPos();
+        if (!m_xAxis.enabled())
+            delta.setX(0);
+        if (!m_yAxis.enabled())
+            delta.setY(0);
+        if (m_dragging) {
+            QPointF pos = target()->parentItem()->mapFromScene(m_startPos) + delta;
+            enforceAxisConstraints(&pos);
+            target()->setPosition(pos);
+        } else if ((m_xAxis.enabled() && QQuickWindowPrivate::dragOverThreshold(delta.x(), Qt::XAxis, point)) ||
+                   (m_yAxis.enabled() && QQuickWindowPrivate::dragOverThreshold(delta.y(), Qt::YAxis, point))) {
+            m_dragging = true;
+            emit draggingChanged();
+        }
+    } break;
+    case QQuickEventPoint::Released:
+        if (m_dragging) {
+            m_dragging = false;
+            emit draggingChanged();
+        }
+        break;
+    default:
+        break;
+    }
+}
+
+void QQuickDragHandler::enforceConstraints()
+{
+    if (!target() || !target()->parentItem())
+        return;
+    QPointF pos = target()->position();
+    QPointF copy(pos);
+    enforceAxisConstraints(&pos);
+    if (pos != copy)
+        target()->setPosition(pos);
+}
+
+void QQuickDragHandler::enforceAxisConstraints(QPointF *localPos)
+{
+    if (m_xAxis.enabled())
+        localPos->setX(qBound(m_xAxis.minimum(), localPos->x(), m_xAxis.maximum()));
+    if (m_yAxis.enabled())
+        localPos->setY(qBound(m_yAxis.minimum(), localPos->y(), m_yAxis.maximum()));
+}
+
+QQuickDragAxis::QQuickDragAxis()
+  : m_minimum(-DBL_MAX)
+  , m_maximum(DBL_MAX)
+  , m_enabled(true)
+{
+}
+
+void QQuickDragAxis::setMinimum(qreal minimum)
+{
+    if (m_minimum == minimum)
+        return;
+
+    m_minimum = minimum;
+    emit minimumChanged();
+}
+
+void QQuickDragAxis::setMaximum(qreal maximum)
+{
+    if (m_maximum == maximum)
+        return;
+
+    m_maximum = maximum;
+    emit maximumChanged();
+}
+
+void QQuickDragAxis::setEnabled(bool enabled)
+{
+    if (m_enabled == enabled)
+        return;
+
+    m_enabled = enabled;
+    emit enabledChanged();
+}
+
+QT_END_NAMESPACE
diff --git a/src/quick/handlers/qquickdraghandler_p.h b/src/quick/handlers/qquickdraghandler_p.h
new file mode 100644
index 0000000000..0ce03c2c4c
--- /dev/null
+++ b/src/quick/handlers/qquickdraghandler_p.h
@@ -0,0 +1,130 @@
+/****************************************************************************
+**
+** 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 QQUICKDRAGHANDLER_H
+#define QQUICKDRAGHANDLER_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 "qquickpointersinglehandler_p.h"
+
+QT_BEGIN_NAMESPACE
+
+class Q_AUTOTEST_EXPORT QQuickDragAxis : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(qreal minimum READ minimum WRITE setMinimum NOTIFY minimumChanged)
+    Q_PROPERTY(qreal maximum READ maximum WRITE setMaximum NOTIFY maximumChanged)
+    Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
+
+public:
+    QQuickDragAxis();
+
+    qreal minimum() const { return m_minimum; }
+    void setMinimum(qreal minimum);
+
+    qreal maximum() const { return m_maximum; }
+    void setMaximum(qreal maximum);
+
+    bool enabled() const { return m_enabled; }
+    void setEnabled(bool enabled);
+
+signals:
+    void minimumChanged();
+    void maximumChanged();
+    void enabledChanged();
+
+private:
+    qreal m_minimum;
+    qreal m_maximum;
+    bool m_enabled;
+};
+
+class Q_AUTOTEST_EXPORT QQuickDragHandler : public QQuickPointerSingleHandler
+{
+    Q_OBJECT
+    Q_PROPERTY(QQuickDragAxis * xAxis READ xAxis CONSTANT)
+    Q_PROPERTY(QQuickDragAxis * yAxis READ yAxis CONSTANT)
+    Q_PROPERTY(bool dragging READ dragging NOTIFY draggingChanged)
+
+public:
+    QQuickDragHandler(QObject *parent = 0);
+    ~QQuickDragHandler();
+
+    void handleEventPoint(QQuickEventPoint *point) Q_DECL_OVERRIDE;
+
+    QQuickDragAxis *xAxis() { return &m_xAxis; }
+    QQuickDragAxis *yAxis() { return &m_yAxis; }
+
+    bool dragging() const { return m_dragging; }
+
+    Q_INVOKABLE void enforceConstraints();
+
+Q_SIGNALS:
+//    void gestureStarted(QQuickGestureEvent *gesture);
+    void draggingChanged();
+
+private:
+    void ungrab();
+    void enforceAxisConstraints(QPointF *localPos);
+
+private:
+    bool m_dragging;
+    QPointF m_startPos;
+    QQuickDragAxis m_xAxis;
+    QQuickDragAxis m_yAxis;
+
+    friend class QQuickDragAxis;
+};
+
+QT_END_NAMESPACE
+
+QML_DECLARE_TYPE(QQuickDragHandler)
+QML_DECLARE_TYPE(QQuickDragAxis)
+
+#endif // QQUICKDRAGHANDLER_H
diff --git a/src/quick/handlers/qquickhandlersmodule.cpp b/src/quick/handlers/qquickhandlersmodule.cpp
index dd50c367ec..398ca0484f 100644
--- a/src/quick/handlers/qquickhandlersmodule.cpp
+++ b/src/quick/handlers/qquickhandlersmodule.cpp
@@ -39,6 +39,7 @@
 
 #include "qquickhandlersmodule_p.h"
 #include "qquickpointerhandler_p.h"
+#include "qquickdraghandler_p.h"
 
 static void initResources()
 {
@@ -74,6 +75,9 @@ static void qt_quickhandlers_defineModule(const char *uri, int major, int minor)
         QQuickPointerHandler::tr("PointerUniqueId is only available as a property of PointerEvent"));
 
     qmlRegisterType<QQuickPointerHandler>(uri,major,minor,"PointerHandler");
+    qmlRegisterType<QQuickDragHandler>(uri,major,minor,"DragHandler");
+    qmlRegisterUncreatableType<QQuickDragAxis>(uri, major, minor, "DragAxis",
+        QQuickDragHandler::tr("DragAxis is only available as a grouped property of DragHandler"));
 }
 
 void QQuickHandlersModule::defineModule()