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(ns canvas-fn.core
(:require [clojure.browser.event :as event]
[domina :as dom]
[canvas-fn.canvas :as canv]
[canvas-fn.util :as util]
[canvas-fn.vectors :as v]))
;; Reference to the canvas element
(def canvas (dom/by-id "draw-canvas"))
(def info (dom/by-id "info"))
(def attractor-acceleration 0.04)
(def max-velocity 2)
#_(event/listen canvas "click" #_(dom/set-text! info (str "clicked..,,." (.-pageX %) )))
;; Data to be drawn
(defonce model (atom {:attractor {:pos [225 225]}
:balls (for [n (range 1 30)]
{:pos [(* n 40) (* n 10)] :velocity [0 0.3] :acceleration [0 0]})}))
;; Interaction handling
;; Compute the position relative to the canvas element and take scrolling into account
(defn move-attractor-to-mouse [event]
(let [canvas-x (- (+ (.-clientX event) (.-scrollX js/window)) (.-offsetLeft canvas))
canvas-y (- (+ (.-clientY event) (.-scrollY js/window)) (.-offsetTop canvas))]
(swap! model #(assoc-in % [:attractor :pos] [canvas-x canvas-y]))))
(event/listen canvas "click" move-attractor-to-mouse)
;; Rendering
(defn draw-circle-large [canvas pos]
(canv/draw-circle canvas pos 20 (str "rgb(200,80,80)") (str "rgb(140,140,140)")))
(defn draw-circle [canvas pos]
(canv/draw-circle canvas pos 10 (str "rgb(50,50,50)") (str "rgb(140,140,140)")))
(defn render [canvas model]
"Clears canvas and draws the model"
(canv/init-canvas canvas)
(doseq [ball (:balls model)]
(draw-circle canvas (:pos ball)))
(draw-circle-large canvas (:pos (:attractor model)))))
(defn accelerate-entities [entities]
(for [entity entities]
(assoc entity :velocity (->
(v/vplus (:velocity entity) (:acceleration entity))
(v/vlimit max-velocity)))))
(defn move-entities [entities]
(for [entity entities]
(assoc entity :pos (v/vplus (:pos entity) (:velocity entity)))))
(defn calculate-attraction-force [ball attractor]
(let [force-direction (v/vsub (:pos attractor) (:pos ball))
normalized (v/vnormalize force-direction)
with-strength (v/vmult normalized attractor-acceleration)]
(defn apply-attract-force [balls attractor]
(for [ball balls]
(assoc ball :acceleration (calculate-attraction-force ball attractor))))
(defn accelerate-balls [model]
(update-in model [:balls] accelerate-entities))
(defn attract-balls [model]
(update-in model [:balls] apply-attract-force (:attractor model)))
(defn move-balls [model]
(update-in model [:balls] move-entities))
(defn update-model [model]
"Updates the model"
(-> model
(defn main []
(swap! model update-model)
(render canvas @model)))
(defn animate []
"Main loop"
(canv/animate animate)
(util/log "Start animations")
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