Qt按住Ctrl+滚动滚轮实现放大缩小

核心代码为

void Widget::wheelEvent(QWheelEvent *event)
{
    qDebug() << "wheel";
    if ( QApplication::keyboardModifiers () == Qt::ControlModifier)
     {
        if (event->delta() > 0) {
            zoomIn();
        } else {
            zoomOut();
        }
     }
}