1/****************************************************************************
2**
3** Copyright (C) 2016 The Qt Company Ltd.
4** Contact: https://www.qt.io/licensing/
5**
6** This file is part of the examples of the Qt Toolkit.
7**
8** $QT_BEGIN_LICENSE:BSD$
9** Commercial License Usage
10** Licensees holding valid commercial Qt licenses may use this file in
11** accordance with the commercial license agreement provided with the
12** Software or, alternatively, in accordance with the terms contained in
13** a written agreement between you and The Qt Company. For licensing terms
14** and conditions see https://www.qt.io/terms-conditions. For further
15** information use the contact form at https://www.qt.io/contact-us.
16**
17** BSD License Usage
18** Alternatively, you may use this file under the terms of the BSD license
19** as follows:
20**
21** "Redistribution and use in source and binary forms, with or without
22** modification, are permitted provided that the following conditions are
23** met:
24** * Redistributions of source code must retain the above copyright
25** notice, this list of conditions and the following disclaimer.
26** * Redistributions in binary form must reproduce the above copyright
27** notice, this list of conditions and the following disclaimer in
28** the documentation and/or other materials provided with the
29** distribution.
30** * Neither the name of The Qt Company Ltd nor the names of its
31** contributors may be used to endorse or promote products derived
32** from this software without specific prior written permission.
33**
34**
35** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
36** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
37** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
38** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
39** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
41** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
42** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
43** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
44** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
45** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
46**
47** $QT_END_LICENSE$
48**
49****************************************************************************/
50
51#include "diagramscene.h"
52#include "diagramitem.h"
53
54#include <QGraphicsSceneMouseEvent>
55
56DiagramScene::DiagramScene(QObject *parent)
57 : QGraphicsScene(parent)
58{}
59
60void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
61{
62 QPointF mousePos(event->buttonDownScenePos(button: Qt::LeftButton).x(),
63 event->buttonDownScenePos(button: Qt::LeftButton).y());
64 const QList<QGraphicsItem *> itemList = items(pos: mousePos);
65 movingItem = itemList.isEmpty() ? nullptr : itemList.first();
66
67 if (movingItem != nullptr && event->button() == Qt::LeftButton)
68 oldPos = movingItem->pos();
69
70 clearSelection();
71 QGraphicsScene::mousePressEvent(event);
72}
73
74void DiagramScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
75{
76 if (movingItem != nullptr && event->button() == Qt::LeftButton) {
77 if (oldPos != movingItem->pos())
78 emit itemMoved(movedItem: qgraphicsitem_cast<DiagramItem *>(item: movingItem),
79 movedFromPosition: oldPos);
80 movingItem = nullptr;
81 }
82 QGraphicsScene::mouseReleaseEvent(event);
83}
84

source code of qtbase/examples/widgets/tools/undoframework/diagramscene.cpp