Qt双缓冲绘图

双缓冲绘图,就是在其它地方把图画好,然后,再paintEvent里复制过来

头文件

class titleButton  :public QPushButton
{
    Q_OBJECT

#define MY_DEBUG_SWITCH == 1

public:
    explicit titleButton(QWidget *parent = nullptr,const titleButtonType& panitFunc = titleButtonType::unknown);
    ~titleButton();

private:
    void paintEvent(QPaintEvent *) override;
    QImage* hoverImage = nullptr;
};

源文件

titleButton::titleButton(QWidget *parent):
    QPushButton(parent)
    
auto f = [](QImage* im, QPen pen){
    QPainter p(im);
    p.begin(im);
    p.setRenderHint(QPainter::Antialiasing, true);
    //p.fillRect(rect(),QColor(48,48,56));
    
    p.setPen(pen);
    p.drawRect(5, 7, 9, 9);
    p.drawLine(8, 4, 16, 4);
    p.drawLine(17, 4, 17, 12);
    //
    p.end();
    };
   hoverImage = new QImage(size(), QImage::Format_ARGB32_Premultiplied);
         memset(hoverImage->bits(), 0x00, hoverImage->sizeInBytes());
   QPen hoverPen(QColor(255, 92, 56),2);
         f(hoverImage,hoverPen);
}
void titleButton::paintEvent(QPaintEvent *)
{

#if MY_DEBUG_SWITCH == 1
    // 记录开始时间
    auto start = std::chrono::system_clock::now();
    // 做一些工作
#endif

    QPainter widgetPainter(this);
    widgetPainter.drawImage(0, 0, *hoverImage);

#if MY_DEBUG_SWITCH == 1
    // 记录结束时间
    auto end = std::chrono::system_clock::now();
    std::chrono::duration<double> diff = end-start;//milliseconds|毫秒 ---- microseconds|纳秒
    qDebug()<< " ints : " << std::chrono::duration_cast<std::chrono::microseconds>(diff).count() << " mics\n";
#endif

}