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QPainterStateGuard Class

QPainterStateGuard 是一个 RAII 方便类，用于平衡QPainter::save() 和QPainter::restore() 调用。更多

头文件： #include <QPainterStateGuard>
CMake： find_package(Qt6 REQUIRED COMPONENTS Gui)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake： QT += gui
自Qt 6.9

注意：该类中的所有函数都是可重入的。

公共函数

QPainterStateGuard(QPainter *painter, QPainterStateGuard::InitialState state = InitialState::Save)
QPainterStateGuard(QPainterStateGuard &&other)
~QPainterStateGuard()
void restore()
void save()
void swap(QPainterStateGuard &other)
QPainterStateGuard &operator=(QPainterStateGuard &&other)

详细说明

QPainterStateGuard 在任何地方都应作为QPainter::save() 的替代函数使用，以确保在完成绘制例程后调用相应的QPainter::restore() 以避免这两个函数之间的不平衡调用。

使用QPainter::save()/QPainter::restore() 的示例：

void MyWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(Qt::red);
    if (drawText) {
        painter.save();
        painter.setPen(Qt::blue);
        painter.setFont(QFont("Arial", 30));
        painter.drawText(rect(), Qt::AlignCenter, "Qt");
        painter.restore();  // don't forget to restore previous painter state
    }
    painter.drawLine(line);
}

使用 QPainterStateGuard 的示例：

void MyGuardWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(Qt::red);
    if (drawText) {
        QPainterStateGuard guard(&painter)
        painter.setPen(Qt::blue);
        painter.setFont(QFont("Arial", 30));
        painter.drawText(rect(), Qt::AlignCenter, "Qt");
    }
    painter.drawLine(line);
}

另请参阅 QPainter 。

成员函数文档

[explicit] QPainterStateGuard::QPainterStateGuard(QPainter *painter, QPainterStateGuard::InitialState state = InitialState::Save)

构造一个 QPainterStateGuard，如果state 是InitialState::Save （默认情况），则在painter 上调用save() 。当 QPainterStateGuard 被销毁时，调用restore() 的次数与调用save() 的次数相同，以恢复QPainter 的状态。

[noexcept] QPainterStateGuard::QPainterStateGuard(QPainterStateGuard &&other)

移动-从other 中构建一个画家国家卫队。

[noexcept] QPainterStateGuard::~QPainterStateGuard()

销毁QPainterStateGuard 实例，并像调用save() 那样频繁调用restore() 以恢复QPainter 的状态。

void QPainterStateGuard::restore()

如果内部保存/恢复计数器大于零，则调用QPainter::restore() 。

注意： 如果计数器已经归零，该函数会在调试构建时断言。

void QPainterStateGuard::save()

调用QPainter::save() 并将内部保存/恢复计数器增加一个。

[noexcept] void QPainterStateGuard::swap(QPainterStateGuard &other)

将other 与该画家的国家卫队对调。这一操作非常快速，而且从未出现过故障。

[noexcept] QPainterStateGuard &QPainterStateGuard::operator=(QPainterStateGuard &&other)

移动-将other 指派给该画家的国家卫队。

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