QPaintEngine_raster does not take care of scaling if Pen has dashArray / dashOffset

This code gives a bad representation of the intended Curve:

QPainter p(this);
p.setRenderHint(QPainter::Antialiasing, true);

QPen pe(Qt::red);
pe.setWidth(5);
QVector<qreal> v;
v << 20;
v << 20;
			
pe.setDashPattern(v);
pe.setDashOffset(i/10.0f);

p.setPen(pe);

QPainterPath path;
path.moveTo(0,20);
path.cubicTo(0, 0, 20, 0, 30, 20);
p.scale(width()/40, width()/40);

p.drawPath(path);

You can see that it draws Lines instead of a curve. This comes from QBezier::toPolygon not taking into account the current scaling of the matrix. It assumes that the control point coordinates map directly to pixels which is not the case.

I fixed it in QBezier / QDashStroker / QPaintEngineEx by forwarding the scale factor and dividing "flatness/scale" in Qbezier.cpp:248:

if (d < (flatness/_scaleMax)*l || b == beziers + 31) {

This works but is not perfect, finding the right scaleMax is non obvious.

Cheers,
Marcus