minimum deployment target is 12.0, after upgrade to 13.0, it works.

it seems y-axis has flipped. 如果这个UIbezierPath创建时对称于y轴，再将其变换回来，则结果是正确的，此时UIbezierPath有正确的位置，且有正确的shader。 So weird, I don't know it's a feature or a bug. It may affects thounds of apps. Please check. Thank you!

for circle paths, besides the method mentioned above, 4pi angle rather than 2pi angle should alose be applied, a negative radius should also be applied. I don't know why. It's weird. It just makes no sense.

write a custom UIView on your own. that's what we have done...