mark: fix handling of stroke: none

[NicoWeio]

The following minimal example results in an error:

#import "@preview/cetz:0.4.2": canvas, draw, matrix, vector

#set page(width: auto, height: auto, margin: .5cm)

#canvas({
  import draw: *

  mark((0, 0), 90deg, symbol: "circle", fill: blue, stroke: none)
})

expected color, gradient, tiling, or auto, found none

I found that this is because we do not actually pass stroke: none to std.curve in canvas.typ. Instead, util.resolve-stroke will create a dict with invalid (in Typst) values:

#let resolve-stroke(stroke) = {
  if stroke == none {
    return (paint: none, thickness: 0pt, join: none, cap: none, miter-limit: 4)
  }
  …

Within CeTZ, resolve-stroke is only used in the mark.typ file, so it should be safe to change its behavior.

I can think of many ways to solve this, but since my testing environment is broken right now, I just wanted to put this out for discussion.

[johannes-wolf]

Thank you for bringing this up. I've merged a different fix for this issue.