Using dotted QPainterPath in QGLWidget leads to very high memory consumption

[Lodorot]

Hello,

using QGraphicPathItems within a QGraphicsView with QGLWidget viewport I came across a strange memory consumption problem. It only happens when using a QGLWidget viewport and a DotLine or DashLine pen.

Here is a short code snipped:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QGraphicsView * view = this->findChild<QGraphicsView*>();
    view->setScene(new QGraphicsScene());
    view->setViewport(new QGLWidget());
 
    QGraphicsPathItem * pathItem = new QGraphicsPathItem();
    pathItem->setPen(QPen(Qt::black, 1.0, Qt::DotLine));
    view->scene()->addItem(pathItem);
 
    double i = 1000000.0;
    QPainterPath path;
    path.lineTo(i, -i);
    path.lineTo(-i, i);
    pathItem->setPath(path);
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QGraphicsView * view = this->findChild<QGraphicsView*>();
    view->setScene(new QGraphicsScene());
    view->setViewport(new QGLWidget());

    QGraphicsPathItem * pathItem = new QGraphicsPathItem();
    pathItem->setPen(QPen(Qt::black, 1.0, Qt::DotLine));
    view->scene()->addItem(pathItem);

    double i = 1000000.0;
    QPainterPath path;
    path.lineTo(i, -i);
    path.lineTo(-i, i);
    pathItem->setPath(path);
}

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I tried several configurations with and without QGLWidget, with and without a solid line.

Here are the memory consumption results:

QGLWidget, SolidLine, i = 1000000.0 : 19,3 MB
QGLWidget, SolidLine, i = 5000000.0 : 19,3 MB

no QGLWidget, DotLine, i = 1000000.0 : 13,4 MB
no QGLWidget, DotLine, i = 5000000.0 : 13,4 MB

QGLWidget, DotLine, i = 1000000.0 : 395 MB
QGLWidget, DotLine, i = 5000000.0 : 1,73 GB


Any I ideas how to handle this problem or what I can do to still use dotted paths within a QGLWidget viewport?


Thanks

Lodorot