when displaying QQuickItem with custom QSGRenderNode,
the clip of parent flickable can't work as expected.

QQuickItem::clipRect():
flick inner: clipRect() is as expected
flick outer: clipRect() is keep same

when I try to use scissorRect when rendering:
flick inner: the scissorRect is keep same
flicking outer: scissorRect will change, but the value is not same as expected, it looks like is the intersect of two flickable rect in the whole window.

but the official control (blue plus button in the center of custom item) can be clipped as expected, so how to do like that in custom QSGRenderNode?

or some example code?