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>

1 files changed, 160 insertions, 0 deletions

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