Find closest point by name

CHANGES.md

@@ -29,7 +29,7 @@ package called `cetz-plot`.
   depth ordering and face culling of drawables. Ordering is enabled by default.
 - Closed `line` and `merge-path` elements now have a `"centroid"` anchor that
   is the calculated centroid of the (non self-intersecting!) shape.
-- Added `closest-point` for creating an anchor at the closest point between a
+- Added `find-closest-point` for creating an anchor at the closest point between a
   reference point and one or more elements.
 
 ## Marks

src/bezier.typ

@@ -586,8 +586,14 @@
   return pts
 }
 
-/// Find the closest point on a bezier to a given point
-/// by using a binary search along the curve.
+/// Find the closest point on a bezier to a given point.
+///
+/// - pt (vector): Reference point to find the closest point to
+/// - s (vector): Bezier start
+/// - e (vector): Bezier end
+/// - c1 (vector): Bezier control point 1
+/// - c2 (vector): Bezier control point 2
+/// - max-recursion (int): Max recursion depth
 #let cubic-closest-point(pt, s, e, c1, c2, max-recursion: 1) = {
   let probe(low, high, depth) = {
     let min = calc.inf

src/draw.typ

@@ -1,4 +1,4 @@
-#import "draw/grouping.typ": intersections, group, scope, anchor, copy-anchors, place-anchors, set-ctx, get-ctx, for-each-anchor, on-layer, place-marks, hide, floating, closest-point
+#import "draw/grouping.typ": intersections, group, scope, anchor, copy-anchors, place-anchors, set-ctx, get-ctx, for-each-anchor, on-layer, place-marks, hide, floating, find-closest-point
 #import "draw/transformations.typ": set-transform, rotate, translate, scale, set-origin, move-to, set-viewport
 #import "draw/styling.typ": set-style, fill, stroke
 #import "draw/shapes.typ": circle, circle-through, arc, arc-through, mark, line, grid, content, rect, bezier, bezier-through, catmull, hobby, merge-path

src/draw/grouping.typ

@@ -195,24 +195,33 @@
 /// creates an anchor. Transformations insides the body are scoped and do
 /// not get applied outsides.
 ///
-/// - name (string): Anchor name.
+/// - name (str): Anchor name.
 /// - reference-point (coordinate): Coordinate to find the closest point to.
-/// - body (element): One or more elements to consider. A least one is required. A function that accepts `ctx` and returns elements is also accepted.
-#let closest-point(name, reference-point, body) = {
+/// - body (element,str): One or more elements to consider. A least one is required. A function that accepts `ctx` and returns elements is also accepted. If a string is passed, the existing named element is used.
+#let find-closest-point(name, reference-point, body) = {
   import "/src/bezier.typ": cubic-closest-point
 
   assert(type(name) == str,
     message: "Anchor name must be of type string, got " + repr(name))
+  assert(type(body) in (array, function, str),
+    message: "Expected body to be a list of elements, a callback or an elements name")
   coordinate.resolve-system(reference-point)
 
   return (ctx => {
     let (_, pt) = coordinate.resolve(ctx, reference-point)
     pt = util.apply-transform(ctx.transform, pt)
 
-    let group-ctx = ctx
-    group-ctx.groups.push(())
-    let (ctx: group-ctx, drawables, bounds) = process.many(group-ctx, util.resolve-body(ctx, body))
-    ctx.nodes += group-ctx.nodes
+    let (sub-ctx, drawables, output-drawables) = if type(body) == str {
+      let node = ctx.nodes.at(body)
+      (ctx, node.drawables, false)
+    } else {
+      let group-ctx = ctx
+      group-ctx.groups.push(())
+      let node = process.many(group-ctx, util.resolve-body(ctx, body))
+      (node.ctx, node.drawables, true)
+    }
+
+    ctx.nodes += sub-ctx.nodes
 
     let min = calc.inf
     let min-pt = none
@@ -269,8 +278,7 @@
       ctx: ctx,
       name: name,
       anchors: anchors,
-      drawables: drawables,
-      bounds: bounds
+      drawables: if output-drawables { drawables } else { () },
     )
   },)
 }

tests/closest-point/test.typ

@@ -0,0 +1,36 @@
+#set page(width: auto, height: auto)
+#import "/tests/helper.typ": *
+
+#test-case({
+  import cetz.draw: *
+
+  group(name: "g", {
+    rotate(10deg)
+    rect((-1, -1), (1, 1), radius: .45)
+  })
+
+  for i in range(0, 360, step: 10) {
+    let pt = (i * 1deg,  2)
+
+    find-closest-point("test", pt, {
+      rotate(10deg)
+      hide(rect((-1, -1), (1, 1), radius: .45))
+    })
+
+    line(pt, "test")
+    circle(pt, radius: .1, fill: blue)
+  }
+})
+
+#test-case({
+  import cetz.draw: *
+
+  group(name: "g", {
+    rotate(10deg)
+    rect((-1, -1), (1, 1), radius: .45)
+  })
+
+  let pt = (2, 2)
+  find-closest-point("test", pt, "g")
+  line("test", pt)
+})