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@ZachMassia ZachMassia/pong.cljs Secret
Created Mar 4, 2014

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(ns pong.core
(:require-macros [cljs.core.async.macros :refer [go]]
[dommy.macros :refer [sel1]])
(:require [big-bang.core :refer [big-bang!]]
[big-bang.events.browser :refer [client-coords]]
[monet.canvas :as canvas]
[dommy.core :as dommy]))
(enable-console-print!)
;; Globals ----------------------------------------------------------
(def canvas-size {:w 646 :h 400})
(def paddle-offset 12)
(def paddle-size {:w (* 0.05 (:w canvas-size))
:h (* 0.3 (:h canvas-size))})
(def ball-size (* 0.04 (:w canvas-size)))
(def init-paddle-y
"Start the paddles centered vertically."
(let [scr-half-y (/ (:h canvas-size) 2)
paddle-half-y (/ (:h paddle-size) 2)]
(- scr-half-y paddle-half-y)))
(def colours {:bg "#699D32"
:paddle "#2A7E77"
:ball "#281B50"})
;; ==================================================================
;; Helper fns -------------------------------------------------------
(defn init-canvas
"Sets the canvas size and returns a 2D context."
[canvas {:keys [w h]}]
(-> canvas
(dommy/set-attr! :width w :height h)
(canvas/get-context "2d")))
(defn draw-rect [colour ctx dim]
(-> ctx
(canvas/fill-style colour)
(canvas/fill-rect dim)))
(defn create-paddle [update-fn [x y]]
(canvas/entity {:x x
:y y
:w (:w paddle-size)
:h (:h paddle-size)}
update-fn
(partial draw-rect (:paddle colours))))
(defn center-ball [{:keys [h w] :as ball} {canvas-w :w canvas-h :h}]
(-> ball
(assoc :x (- (/ canvas-w 2) (/ w 2)))
(assoc :y (- (/ canvas-h 2) (/ h 2)))))
(defn client->canvas-coords
"Transforms mouse coords from client space to canvas space.
Does not perform bounds checking."
[canvas [x y]]
(let [rect (.getBoundingClientRect canvas)
left (.-left rect)
top (.-top rect)]
[(- x left) (- y top)]))
(defn clamp [x min-val max-val]
(max min-val (min max-val x)))
;; ==================================================================
;; Entities ---------------------------------------------------------
(def background
(canvas/entity {:x 0
:y 0
:w (:w canvas-size)
:h (:h canvas-size)}
nil
(partial draw-rect (:bg colours))))
(def ball
(let [ball-dim {:x 0
:y 0
:w ball-size
:h ball-size}]
(canvas/entity (center-ball ball-dim canvas-size)
nil
(partial draw-rect (:ball colours)))))
(defn update-player-paddle
"Center the paddle on the mouse. Also clamp the paddle y to the canvas."
[event world-state ent]
(let [mouse-y (second (:mouse-coords world-state))
paddle-h (get-in ent [:value :h])
paddle-hh (/ paddle-h 2)
new-y (- mouse-y paddle-hh)]
(assoc-in ent [:value :y] (clamp new-y 0 (- (:h canvas-size) paddle-h)))))
(def player-paddle
(create-paddle update-player-paddle
[(- (- (:w canvas-size) (:w paddle-size))
paddle-offset)
init-paddle-y]))
(def ai-paddle
(create-paddle nil [paddle-offset init-paddle-y]))
;; ==================================================================
(defn update-state
"Update each entity if it has an update fn."
[event world-state]
(update-in world-state [:entities]
#(mapv (fn [ent]
(if-let [update (:update ent)]
(update event world-state ent)
ent))
%)))
(defn update-mouse-coords
"Update the mouse coords when a mouse-move event happens on the canvas."
[canvas event world-state]
(assoc world-state
:mouse-coords (client->canvas-coords canvas (client-coords event))))
(defn render-scene
"Loop over the entities calling each ones draw fn."
[ctx world-state]
(doseq [ent (:entities world-state)]
(let [{:keys [value draw]} ent]
(try
(draw ctx value)
(catch js/Error e
(println e))))))
(defn ^:export init
"The main entry point for the game. The big-bang process is launched from here."
[]
(let [canvas (sel1 :#pong-canvas)
ctx (init-canvas canvas canvas-size)]
(go
(big-bang!
:initial-state {:entities [background player-paddle ai-paddle ball]
:mouse-coords [0 0]}
:on-tick update-state
:on-mousemove (partial update-mouse-coords canvas)
:event-target canvas
:to-draw (partial render-scene ctx)))))
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