Printing areas with semi transparency results in incorrectly printed lines

The example below demonstrates the problem on MacOSX and Windows. The output of the PDF generator is correct. On Windows, the grid-lines are not dotted, and thinner within the bounding rectangle of the semi-transparent polygon. On MacOSX the grid-lines are never dotted, but thicker in the area of the bouding rectangle. Removing the polygon or giving it a fully opaque color prints the grid lines consistently on both Mac and Windows, but still not dotted on Mac OSX.

#include <QtGui>
#include <QtCore>

int main(int argc, char* argv[])
{
QApplication app(argc, argv);
QGraphicsScene scene;
QGraphicsView view;
view.setScene(&scene);

QPen solid(Qt::black);
solid.setWidth(1.0);
QPen pointLine(Qt::black);
pointLine.setWidth(0.0);
pointLine.setStyle(Qt::DotLine);
scene.addRect(0, 0, 400, 400, solid);
scene.addLine(0, 80, 400, 80, pointLine);
scene.addLine(0, 160, 400, 160, pointLine);
scene.addLine(0, 240, 400, 240, pointLine);
scene.addLine(0, 320, 400, 320, pointLine);
scene.addLine(80, 00, 80, 400, pointLine);
scene.addLine(160, 00, 160, 400, pointLine);
scene.addLine(240, 00, 240, 400, pointLine);
scene.addLine(320, 00, 320, 400, pointLine);
QVector<QPointF> polygonPoints = QVector<QPointF>() << QPointF(40, 40)
<< QPointF(120,360) << QPointF(280,360);
QColor polygonFillColor = Qt::red;
polygonFillColor.setAlpha(30);
QPen polygonPen(Qt::red);
polygonPen.setWidth(1.0);
QPolygonF polygon(polygonPoints);
QBrush polygonBrush(polygonFillColor);
scene.addPolygon(polygon, polygonPen, polygonBrush);

view.show();

QRectF bounds = scene.itemsBoundingRect();

{ QPrinter pdfPrinter(QPrinter::HighResolution); pdfPrinter.setOutputFormat(QPrinter::PdfFormat); pdfPrinter.setOutputFileName("output.pdf"); QRectF pdfTargetRect; pdfTargetRect.setSize(bounds.size() * pdfPrinter.resolution() / 100); QPainter pdfPainter(&pdfPrinter); scene.render(&pdfPainter, pdfTargetRect, bounds); }

QPrinter printer(QPrinter::HighResolution);
QPrintDialog printDlg(&printer, &view);
if (printDlg.exec())

{ QRectF targetRect; targetRect.setSize(bounds.size() * printer.resolution() / 100); qDebug() << printer.logicalDpiX() << printer.logicalDpiY(); qDebug() << printer.physicalDpiX() << printer.physicalDpiY(); QPainter painter(&printer); scene.render(&painter, targetRect, bounds); }

return app.exec();
}