include/QtGui/qpainterstateguard.h

0001 // Copyright (C) 2024 Christian Ehrlicher <ch.ehrlicher@gmx.de>
0002 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
0003
0004 #ifndef QPAINTERSTATEGUARD_H
0005 #define QPAINTERSTATEGUARD_H
0006
0007 #include <QtCore/qtclasshelpermacros.h>
0008 #include <QtGui/qpainter.h>
0009
0010 QT_BEGIN_NAMESPACE
0011
0012 class QPainterStateGuard
0013 {
0014     Q_DISABLE_COPY(QPainterStateGuard)
0015 public:
0016     enum class InitialState : quint8 {
0017         Save,
0018         NoSave,
0019     };
0020
0021     QPainterStateGuard(QPainterStateGuard &&other) noexcept
0022         : m_painter(std::exchange(other.m_painter, nullptr))
0023         , m_level(std::exchange(other.m_level, 0))
0024     {}
0025     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QPainterStateGuard)
0026     void swap(QPainterStateGuard &other) noexcept
0027     {
0028         qt_ptr_swap(m_painter, other.m_painter);
0029         std::swap(m_level, other.m_level);
0030     }
0031
0032     Q_NODISCARD_CTOR
0033     explicit QPainterStateGuard(QPainter *painter, InitialState state = InitialState::Save)
0034         : m_painter(painter)
0035     {
0036         verifyPainter();
0037         if (state == InitialState::Save)
0038             save();
0039     }
0040
0041     ~QPainterStateGuard()
0042     {
0043         while (m_level > 0)
0044             restore();
0045     }
0046
0047     void save()
0048     {
0049         verifyPainter();
0050         m_painter->save();
0051         ++m_level;
0052     }
0053
0054     void restore()
0055     {
0056         verifyPainter();
0057         Q_ASSERT(m_level > 0);
0058         --m_level;
0059         m_painter->restore();
0060     }
0061
0062 private:
0063     void verifyPainter()
0064     {
0065         Q_ASSERT(m_painter);
0066     }
0067
0068     QPainter *m_painter;
0069     int m_level = 0;
0070 };
0071
0072 QT_END_NAMESPACE
0073
0074 #endif  // QPAINTERSTATEGUARD_H