coordinate: Add register function

Author: johannes-wolf

src/coordinate.typ

@@ -322,11 +322,10 @@
 /// - update (bool): Update the context's last position
 /// -> array
 #let resolve(ctx, ..coordinates, update: true) = {
-  let resolver = ()
-  if type(ctx.resolve-coordinate) == array {
-    resolver += ctx.resolve-coordinate
-  } else if type(ctx.resolve-coordinate) == function {
-    resolver.push(ctx.resolve-coordinate)
+  let resolver = if type(ctx.resolve-coordinate) == array {
+    ctx.resolve-coordinate
+  } else {
+    ()
   }
 
   let result = ()

src/draw.typ

@@ -3,4 +3,4 @@
 #import "draw/styling.typ": set-style, fill, stroke, register-mark
 #import "draw/shapes.typ": circle, circle-through, arc, arc-through, mark, line, grid, content, rect, bezier, bezier-through, catmull, hobby, merge-path, polygon, multi-path
 #import "draw/projection.typ": ortho, on-xy, on-xz, on-yz
-#import "draw/util.typ": assert-version
+#import "draw/util.typ": assert-version, register-coordinate-resolver

src/draw/util.typ

@@ -18,3 +18,41 @@
     return (ctx: ctx)
   },)
 }
+
+/// Push a custom coordinate resolve function to the list of coordinate
+/// resolvers. This resolver is scoped to the current context scope!
+///
+/// A coordinate resolver must be a function of the format `(context, coordinate) => coordinate`. And must _always_ return a valid coordinate or panic, in case of an error.
+///
+/// If multiple resolvers are registered, coordinates get passed through all
+/// resolvers in reverse registering order. All coordinates get paased to cetz'
+/// default coordinate resolvers.
+///
+/// ```typc example
+/// register-coordinate-resolver((ctx, c) => {
+///   if type(c) == dictionary and "log" in c {
+///     c = c.log.map(n => calc.log(n, base: 10))
+///   }
+///   return c
+/// })
+///
+/// circle((log: (10, 0)), radius: .25)
+/// circle((log: (100, 0)), radius: .25)
+/// circle((log: (1000, 0)), radius: .25)
+/// ```
+///
+/// - resolver (function): The resolver function, taking a context and a single coordinate and returning a single coordinate
+#let register-coordinate-resolver(resolver) = {
+  assert.eq(type(resolver), function,
+    message: "Coordinate resolver must be of type function (ctx, coordinate) => coordinate.")
+
+  return (ctx => {
+    if type(ctx.resolve-coordinate) == array {
+      ctx.resolve-coordinate.push(resolver)
+    } else {
+      ctx.resolve-coordinate = (resolver,)
+    }
+
+    return (ctx: ctx)
+  },)
+}

tests/coordinate/custom/test.typ

@@ -15,10 +15,7 @@
     return coordinate
   }
 
-  set-ctx(ctx => {
-    ctx.resolve-coordinate = log-resolver
-    return ctx
-  })
+  register-coordinate-resolver(log-resolver)
 
   set-style(circle: (radius: .1))
   for i in (.1, 1, 10, 100, 1000, 10000) {