path/point.ml


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type t =
  { p: Gg.v2
  ; size : float
  ; angle: float
  }

let empty =
  { p = Gg.V2.of_tuple (0., 0.)
  ; size = 0.
  ; angle = 0.
  }

let create x y =
  { p = Gg.V2.v x y
  ; size = 20.
  ; angle = Float.neg Gg.Float.pi_div_4
  }

let copy point p =
  { point with p }

let (+) p1 p2 =
  { p1 with p = Gg.V2.(+) p1.p p2 }

let get_coord { p; _ } = p

let get_coord'
  : t -> Gg.v2
  = fun t ->
    let open Gg.V2 in
    let trans = of_polar @@ v t.size t.angle in
    t.p + trans

module Repr = CanvaPrinter

type 'a repr =
  { back: ('a Repr.t -> 'a Repr.t)
  ; path: ('a Repr.t)
  ; last_point : t option
  }

let create_path
  : unit -> 'a repr
  = fun () ->
    { back = Repr.close
    ; path = Repr.create ()
    ; last_point = None
    }

(* Start a new path. *)
let start
  : t -> 'a repr -> 'a repr
  = fun t {back; path; _} ->
    let path = Repr.move_to (get_coord t) path in
    let line' = Repr.line_to (get_coord' t) in
    { back = (fun p -> back @@ line' p)
    ; path
    ; last_point = Some t
    }

let line_to
  : t -> 'a repr -> 'a repr
  = fun t {back; path; _} ->
    let line' = Repr.line_to (get_coord' t) in
    { back = (fun t -> back @@ line' t)
    ; path = Repr.line_to t.p path
    ; last_point = Some t
    }

let quadratic_to
  : t -> t -> t -> t -> 'a repr -> 'a repr
  = fun p0 ctrl0 ctrl1 p1 t ->

    let line' path =
      Repr.quadratic_to
        (get_coord' ctrl1)
        (get_coord' ctrl0)
        (get_coord' p0) path in

    let path = Repr.quadratic_to
        (get_coord ctrl0)
        (get_coord ctrl1)
        (get_coord p1)
        t.path in
    { back = (fun p -> t.back @@ line' p)
    ; path
    ; last_point = Some p1
    }

let stop
  : 'a repr -> 'a repr
  = fun {back; path; last_point} ->

    let path =
      match last_point with
      | Some point -> Repr.line_to (get_coord' point) path
      | None -> path in

    { back = (fun x -> x)
    ; path = back path
    ; last_point = None }

let get
  : 'a repr -> 'a Repr.t
  = fun {back; path; _} ->
    back path