Padding fails at arbitrary point for some polygons

[huberf]

I have a relatively simple polygon shown in this plot:

It has slightly angled corners, but no self-intersection, concavity or other odd behavior. When I add padding of 4.8 it succeeds (and is now a simple polygon with 4 sides) but when this increase to 4.9 or higher it fails. However, if I add 4 padding and then add 1 padding to the created polygon, it works and appears to correctly create a polygon with an effective padding of 5.

Here is the code to reproduce:

let Offset = require('polygon-offset')
let offset = new Offset()
let a = [[0.5298861641722039,723.3616754870759],[87.9120549728682,723.0000176351272],[87.91417247478793,722.0000198770368],[89.4375266032173,2.590654049084369],[88.02779525598075,2.0021133264491264],[2.6958948009635018,2.0310984560503553],[2.0250343895624585,3.3632278972327185],[2.022957794804972,4.363225741107499],[0.5298861641722039,723.3616754870759]]
offset.data(a).padding(4.8) // works
offset.data(a).padding(4.9) // fails

The logging specifies that it has switched to brute force at 4.9, and then either fails with:

Or it returns 2 polygons (which does not make sense as this is perfectly convex polygon).

I have experienced the issue of the algorithm incorrectly returning 2 polygons instead of one with other point sets, but this was the simplest polygon yet that still ran into issues with the polygon.

Thank you!

[whucj]

I have the same problem.

[w8r]

Thanks a lot! The issue here is with the underlying polygon clipping algorithm. I will check it there.

[whucj]

Thanks a lot! The issue here is with the underlying polygon clipping algorithm. I will check it there.

Thanks.
By debugging the code, it is found that the problem is the union method !