Question

我正在尝试在QGraphicsScene子类的drawBackground（）函数中绘制背景网格：

void Scene::drawBackground(QPainter *painter, const QRectF &rect)
{
    const int gridSize = 50;

    const int realLeft = static_cast<int>(std::floor(rect.left()));
    const int realRight = static_cast<int>(std::ceil(rect.right()));
    const int realTop = static_cast<int>(std::floor(rect.top()));
    const int realBottom = static_cast<int>(std::ceil(rect.bottom()));

    // Draw grid.
    const int firstLeftGridLine = realLeft - (realLeft % gridSize);
    const int firstTopGridLine = realTop - (realTop % gridSize);

    QVarLengthArray<QLine, 100> lines;

    for (qreal x = firstLeftGridLine; x <= realRight; x += gridSize)
        lines.append(QLine(x, realTop, x, realBottom));
    for (qreal y = firstTopGridLine; y <= realBottom; y += gridSize)
        lines.append(QLine(realLeft, y, realRight, y));

    //painter->setRenderHint(QPainter::Antialiasing);
    painter->setPen(QPen(QColor(220, 220, 220), 0.0));
    painter->drawLines(lines.data(), lines.size());

    // Draw axes.
    painter->setPen(QPen(Qt::lightGray, 0.0));
    painter->drawLine(0, realTop, 0, realBottom);
    painter->drawLine(realLeft, 0, realRight, 0);
}

但是，除非我打开消除锯齿功能，否则移动项目有时会在网格中留下瑕疵（未绘制的区域）。当视图缩小一点时，它似乎主要发生在低缩放级别。我在这里做错了什么想法？

我真的不想打开抗锯齿，因为线条是严格水平和垂直的，我希望它们尽可能清晰。

任何帮助都很受欢迎，此致，猫王

Answer 1

听起来您需要使用不同的视口更新方法：

http://doc.qt.io/qt-5/qgraphicsview.html#viewportUpdateMode-prop

也许是后台缓存：

http://doc.qt.io/qt-5/qgraphicsview.html#cacheMode-prop

尝试在QGraphicsScene中绘制没有消除锯齿的背景网格时的工件

1 个答案: