QPainter.drawPolyline performance issue

In the context of the PythonQwt project, I'm implementing widgets for drawing curves efficiently in pure Python (+ NumPy +Qt). This is working quite well with PyQt4 and PyQt5. Lately, I've been trying to add support for PySide2.

While optimizing a function for creating efficiently a QPolygonF object from a NumPy array, I came accross a performance issue with the QPainter.drawPolyline drawing primitive (for 1e6 points).

You will find attached a test script showing those results on my machine:

• dt[PyQt5 v5.15.0] = 19 ms
• dt[PySide2 v5.15.0] = 1115 ms (i.e. approx. 60 times slower than PyQt5)

Test script requirements : QtPy, PyQt5 or PySide2, NumPy (the latter is only used for generating the huge amount of data which is injected into the QPolygonF object).