Problem

When drawing a rectangle with a line width of 1px on a QPainter with antialiasing enabled results in slightly transparent corners regardless of what JoinStyle is set. The same can be observed for polylines and QPainterPaths

def paintEvent(self, event):
    with QPainter(self) as p:
        p.setRenderHint(QPainter.Antialiasing, True)

        p.fillRect(self.rect(), QColor('black'))
        p.setBrush(Qt.NoBrush)

        # 1px width border, corner is partially transparent
        p.setPen(QPen(QColor("orange"), 1, cap=Qt.SquareCap, join=Qt.MiterJoin))
        p.drawRect(QRectF(10.5, 10.5, 50., 25.))

        # 3px width border, corner is crisp
        p.setPen(QPen(QColor("orange"), 3, cap=Qt.SquareCap, join=Qt.MiterJoin))
        p.drawRect(QRectF(15.5, 15.5, 50., 25.))

produces this output:

Question

Is there a way to get crisp corners for a 1px wide pen that also work for partially transparent lines and arbitrary QPainterPaths?

Solution tried so far

• Drawing each line individually:
  Works fine, but there are artifacts with partially transparent lines because the overlap at the corners.

• Drawing each line individually, but shifting start of each line by 1:
  Solves issue with partially transparent lines right angles, but not other angles or curves.

• Temporarily disabling antialiasing:
  Diagonal lines and curved become jagged.