Tangent inconsistency for 0 length line

[Tetragramm]

The tangent coordinates give inconsistent results for certain situations.
See the code

#import "@preview/cetz:0.4.2"

#cetz.canvas(length:1cm, {
  import cetz.draw: *
  circle((2,2), radius: 2, name:"c")
  let a = "c.0deg"
  circle(a)
  line((a,-1cm,(element:"c", point:a, solution:1)),
    (a,5cm,(element:"c", point:a, solution:1))
  )
})

Which produces

Changing a to "c.10deg" produces

and "c.30deg" errors with Panicked with: "No tangent solution for element c and point \"c.30deg\""

While the panic is probably the "correct" solution, the result at "c.10deg" is maybe the most convenient for drawing things.

[johannes-wolf]

This is a precision problem of how cetz finds the border anchors: it casts a line in the direction and finds the intersection with the path. I am not sure how to handle this. We will run into precision problems with distance based path anchors on circles even if we handle circle paths with more precision.

I think the best option would be to move the whole "tangent" finding to a path based version that supports any shape and approximates the tangents via sampling + bisection.