Improve arc anchors

src/draw/shapes.typ

@@ -178,8 +178,8 @@
  return (ctx => {
  let style = styles.resolve(ctx.style, style, root: "arc")
  assert(style.mode in ("OPEN", "PIE", "CLOSE"))
- let (ctx, position) = coordinate.resolve(ctx, position)
- let (x, y, z) = position
+ let (ctx, arc-start) = coordinate.resolve(ctx, position)
+ let (x, y, z) = arc-start
  let (rx, ry) = util.resolve-radius(style.radius).map(util.resolve-number.with(ctx))
 
  let path = (drawable.arc(
@@ -203,22 +203,23 @@
  sector-center.at(1) + ry * calc.sin(stop-angle),
  z
  )
- let chord-center = vector.lerp(position, arc-end, 0.5)
+ let chord-center = vector.lerp(arc-start, arc-end, 0.5)
  let arc-center = (
  sector-center.first() + rx * calc.cos((stop-angle + start-angle)/2),
  sector-center.at(1) + ry * calc.sin((stop-angle + start-angle)/2),
  z
  )
 
  // center is calculated based on observations of tikz's circular sector and semi circle shapes.
- let center = if style.mode == "PIE" { 
- // A circular sector's anchor is placed half way between the sector-center and arc-center when the angle is 180deg. At 60deg it is placed 1/3 of the way between, this is mirrored at 300deg.
+ let center = if style.mode != "CLOSE" {
+ // A circular sector's center anchor is placed half way between the sector-center and arc-center when the angle is 180deg. At 60deg it is placed 1/3 of the way between, this is mirrored at 300deg.
  vector.lerp(
  arc-center, 
  sector-center,
  if (stop-angle + start-angle) > 180deg { (stop-angle + start-angle) } else { (stop-angle + start-angle) + 180deg } / 720deg
  )
  } else {
+ // A semi circle's center anchor is placed half way between the sector-center and arc-center, so that is always `center` when the arc is closed. Otherwise the point at which compass anchors are calculated from will be outside the lines.
  vector.lerp(
  arc-center,
  chord-center,
@@ -227,27 +228,31 @@
  }
 
  // compass anchors are placed on the shapes border in tikz so prototype version is setup for use here
- let border = anchor_.border.with(center, 2*rx, 2*ry, path + if style.mode == "OPEN" {
- (drawable.path(path-util.line-segment((position, arc-end))),)
- })
+ let border = anchor_.border.with(
+ center, 
+ 2*rx, 2*ry, 
+ path + if style.mode == "OPEN" {
+ (
+ drawable.path((
+ path-util.line-segment((position, sector-center)),
+ path-util.line-segment((sector-center, arc-end))
+ ))
+ ,)
+ }
+ )
 
  let (transform, anchors) = anchor_.setup(
  anchor => {
+ if anchor in anchor_.compass-angle {
+ return border(anchor_.compass-angle.at(anchor))
+ }
  (
  arc-start: position,
  origin: sector-center,
  arc-end: arc-end,
  arc-center: arc-center,
  chord-center: chord-center,
  center: center,
- north: border(90deg),
- north-east: border(45deg),
- east: border(0deg),
- south-east: border(-45deg),
- south: border(-90deg),
- south-west: border(-135deg),
- west: border(180deg),
- north-west: border(135deg)
  ).at(anchor)
  },
  (

tests/anchor/element-anchors/test.typ

@@ -18,8 +18,8 @@
  let (_, nv) = coordinate.resolve(ctx, n)
  let (x, y, ..) = nv
  let anchor = (
- (if y < 0 { "north" } else if y > 0 { "south" },) +
- (if x < 0 { "east" } else if x > 0 { "west" },)).filter(p => p != none).join("-")
+ (if y < 0 { "north" } else if y > 0 { "south" },) + (if x < 0 { "east" } else if x > 0 { "west" },)
+ ).filter(p => p != none).join("-")
  if anchor == none {
  anchor = "south"
  }
@@ -49,6 +49,11 @@
  display(arc, (0,0), start: 225deg, stop: 135deg, radius: 5, mode: "PIE")
 }))
 
+#box(stroke: 2pt + red, canvas(length: 1cm, {
+ import draw: *
+ display(arc, (0,0), start: 225deg, stop: 135deg, radius: 5, mode: "CLOSE")
+}))
+
 #box(stroke: 2pt + red, canvas(length: 1cm, {
  import draw: *
  display(line, (-1,0), (0,1), (1,0))