QPainterStateGuard Class
QPainterStateGuard 是一个 RAII 便利类，用于平衡调用 `QPainter::save()` 和 `QPainter::restore()`。更多内容...
| 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 |
- 所有成员列表（包括继承的成员）
- QPainterStateGuard 属于绘制类。
注意：该类中的所有函数均为可重入函数。
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
应在所有地方使用 QPainterStateGuard 来代替QPainter::save()，以确保在绘制例程结束时调用相应的QPainter::restore()，从而避免这两个函数之间的调用不平衡。
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)
若state 为InitialState::Save （这是默认值），则构建一个QPainterStateGuard，并在painter 上调用save()。当QPainterStateGuard被销毁时，restore()的调用次数将与save()的调用次数相同，以恢复QPainter 的状态。
[noexcept] QPainterStateGuard::QPainterStateGuard(QPainterStateGuard &&other)
从other 动态构造一个画家状态守护者。
[noexcept] QPainterStateGuard::~QPainterStateGuard()
销毁QPainterStateGuard 实例，并调用restore()的次数与调用save()的次数相同，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： 在调试版本中，如果计数器已归零，此 函数会触发断言。
void QPainterStateGuard::save()
调用QPainter::save()，并将内部的保存/恢复计数器加一。
[noexcept] void QPainterStateGuard::swap(QPainterStateGuard &other)
将 `other ` 与该绘图器状态守护器互换。此操作非常快速，且绝不会失败。
[noexcept] QPainterStateGuard &QPainterStateGuard::operator=(QPainterStateGuard &&other)
将other 赋值给此绘图状态守护变量。
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