Spread in Drop Shadows

Hi! I have been looking for an answer in the community about the logic behind Spread in Drop Shadow. However, I have not found any answer for why Spread only is available when the frame or autolayout is “clip content” checked. I do not understand the logic to this requirement. It is just to know if I am using it in the best way. Thanks a lot for you help!

Spread is currently not possible for complex shapes. A frame without clip content would count as a complex shape since elements can stick out of its borders. Same happens if you have spread on a square, and then edit it in vector mode. You’ll get this message: