#include "myscene.h"
#include <QPainter>

MyScene::MyScene(QObject *parent) : QGraphicsScene(parent)
{

}

void MyScene::drawBackground(QPainter *painter, const QRectF &rect)
{
    QGraphicsScene::drawBackground(painter, rect);

    // 设置画笔
    QPen pen(gridColor);
    pen.setWidth(1);
    painter->setPen(pen);

    // 计算网格线
    qreal left = int(rect.left()) - (int(rect.left()) % gridSize);
    qreal top = int(rect.top()) - (int(rect.top()) % gridSize);

    QVarLengthArray<QLineF, 100> lines;

    for (qreal x = left; x < rect.right(); x += gridSize) {
        lines.append(QLineF(x, rect.top(), x, rect.bottom()));
    }

    for (qreal y = top; y < rect.bottom(); y += gridSize) {
        lines.append(QLineF(rect.left(), y, rect.right(), y));
    }

    // 绘制网格
    painter->drawLines(lines.data(), lines.size());
}