[Graphics View] QGraphicsItem绕中心旋转

以QGraphicsRectItem为例，需要让显示的矩形绕矩形中心旋转，需要用到setTransformOriginPoint以及setRotation函数。
代码如下：

#include "widget.h"
#include "ui_widget.h"
#include <QGraphicsScene>
#include <QGraphicsRectItem>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);


    QGraphicsScene *scene = new QGraphicsScene;
    //-2是为了不显示scrollbar
    scene->setSceneRect(0, 0, ui->view->width()-2, ui->view->height()-2);
    ui->view->setScene(scene);
    for(int i=0; i<4; i++)
    {
        QGraphicsRectItem *item = new QGraphicsRectItem;
        item->setPen(QPen(QColor("red")));
        item->setPos(QPointF(scene->width()/2, scene->height()/2));
        item->setRect(0, 0, scene->width()/4, scene->width()/4);
        scene->addItem(item);
    }

    int i=0;
    for(auto &item : scene->items())
    {
        auto rect = item->boundingRect();
        item->setTransformOriginPoint(QPointF(rect.x(), rect.y())+QPointF(rect.width()/2, rect.height()/2));
        item->setRotation(i++*15);
    }

}

Widget::~Widget()
{
    delete ui;
}

效果图：

image.png