The keyword-argument drawing API

raylib's C functions are positional and often long: DrawText(text, x, y, fontSize, color), DrawRectangle(x, y, width, height, color). Bound literally, example code becomes a wall of bare numbers where the fifth argument's meaning is anyone's guess. This repo keeps the raw binds positional (they mirror C) and layers an ergonomic keyword-argument API on top, so example call sites read as self-describing.

Two layers, one boundary

The FFI boundary stays a faithful, positional mirror of the C signature — that's the contract with the library and the thing to check against raylib.h:

;; src/net/b12n/raylib_jlt/raylib.clj — the FFI boundary (positional, mirrors C)
(ffi/defcfn draw-text      "DrawText"      [:string :int :int :int :uint] :void)
(ffi/defcfn draw-rectangle "DrawRectangle" [:int :int :int :int :uint] :void)
(ffi/defcfn draw-circle    "DrawCircle"    [:int :int :float :uint] :void)

On top sits a thin wrapper per call that names the arguments and supplies defaults:

(defn text!
  "DrawText. :x :y :size :color."
  [s & {:keys [x y size color] :or {x 0 y 0 size 20 color BLACK}}]
  (draw-text s x y size color))

(defn rect!
  "DrawRectangle. :x :y :width :height :color."
  [& {:keys [x y width height color] :or {x 0 y 0 width 10 height 10 color BLACK}}]
  (draw-rectangle x y width height color))

(defn circle!
  "DrawCircle. :x :y :radius :color."
  [& {:keys [x y radius color] :or {x 0 y 0 radius 10 color BLACK}}]
  (draw-circle x y (double radius) color))

The wrappers also absorb small coercions the raw bind is strict about — e.g. circle! calls (double radius) so a caller can pass an int radius without a type error at the :float boundary.

The payoff at the call site (net.b12n.raylib-jlt.core):

(rl/text! "Congrats! You created your first window!"
          :x 190 :y 200 :size 20 :color rl/LIGHTGRAY)
;; vs. the positional (draw-text "…" 190 200 20 rl/LIGHTGRAY)

The ! suffix marks these as side-effecting calls. Sixteen wrappers exist, in three groups:

  • Window + 2D primitives, straight over a scalar bind — window!, text!, fps!, rect!, rect-lines!, rect-gradient!, circle!, circle-lines!, ellipse!, line!, pixel!.
  • 2D shapes rlgl has to draw — sector!, ring!, line-ex!. Their raylib originals (DrawCircleSector, DrawRing, DrawLineEx) take a Vector2 by value and are unbindable, so these emit triangles instead. Same keyword-arg surface; see rlgl-immediate-mode.md.
  • 3D — cube! and sphere!, likewise rlgl vertex streams standing in for the by-value-Vector3 DrawCube / DrawSphere.

(rl-color! and maybe-screenshot! also end in ! but are not part of this wrapper layer — one unpacks a Color for rlgl, the other is smoke-test plumbing.)

The style convention: >3 arguments → keyword args

The rule the whole suite follows:

A function with more than three arguments takes keyword args (or groups scalars into vectors to get to ≤3). Raw ffi/defcfn binds stay positional because they mirror C; recursive math kernels may stay positional with grouped-vector args.

DrawText has five arguments → text! is keyword. cube! would have a long positional list (pos, size, color) → keyword args, and pos/size are themselves grouped [x y z] vectors so each stays one argument:

(defn cube! [& {:keys [pos size color] :or {pos [0.0 0.0 0.0] size 1.0 color BLACK}}]
  …)

(rl/cube! :pos [x 0 z] :size 0.8 :color rl/BLUE)

The camera wrappers take a single map argument for the same reason — a Camera2D has six scalars, well past three:

(rl/with-camera-2d {:offset-x 400 :offset-y 225 :target-x px :target-y py :zoom 1.5}
  (fn [] …))

Why not just bind everything keyword?

Because the FFI boundary should stay a 1:1, positional mirror of the C signature — that's what you diff against the header when a call misbehaves, and what keeps the "is this binding correct?" question answerable. Keyword ergonomics are a caller concern, so they live in a caller-facing layer above the boundary, never in the ffi/defcfn itself. Same reason rgba (packing) and rl-color! (unpacking) wrap the raw :uint/rlColor4ub binds rather than replacing them.

See also