skycons.js

(function(global) {
  "use strict";

  /* Set up a RequestAnimationFrame shim so we can animate efficiently FOR
   * GREAT JUSTICE. */
  var requestInterval, cancelInterval;

  (function() {
    var raf = global.requestAnimationFrame       ||
              global.webkitRequestAnimationFrame ||
              global.mozRequestAnimationFrame    ||
              global.oRequestAnimationFrame      ||
              global.msRequestAnimationFrame     ,
        caf = global.cancelAnimationFrame        ||
              global.webkitCancelAnimationFrame  ||
              global.mozCancelAnimationFrame     ||
              global.oCancelAnimationFrame       ||
              global.msCancelAnimationFrame      ;

    if(raf && caf) {
      requestInterval = function(fn, delay) {
        var handle = {value: null};

        function loop() {
          handle.value = raf(loop);
          fn();
        }

        loop();
        return handle;
      };

      cancelInterval = function(handle) {
        caf(handle.value);
      };
    }

    else {
      requestInterval = setInterval;
      cancelInterval = clearInterval;
    }
  }());


  /* Define skycon things. */
  /* FIXME: I'm *really really* sorry that this code is so gross. Really, I am.
   * I'll try to clean it up eventually! Promise! */
  var KEYFRAME = 500,
      STROKE = 0.08,
      TAU = 2.0 * Math.PI,
      TWO_OVER_SQRT_2 = 2.0 / Math.sqrt(2);

  function circle(ctx, x, y, r) {
    ctx.beginPath();
    ctx.arc(x, y, r, 0, TAU, false);
    ctx.fill();
  }

  function line(ctx, ax, ay, bx, by) {
    ctx.beginPath();
    ctx.moveTo(ax, ay);
    ctx.lineTo(bx, by);
    ctx.stroke();
  }

  function puff(ctx, t, cx, cy, rx, ry, rmin, rmax) {
    var c = Math.cos(t * TAU),
        s = Math.sin(t * TAU);

    rmax -= rmin;

    circle(
      ctx,
      cx - s * rx,
      cy + c * ry + rmax * 0.5,
      rmin + (1 - c * 0.5) * rmax
    );
  }

  function puffs(ctx, t, cx, cy, rx, ry, rmin, rmax) {
    var i;

    for(i = 5; i--; )
      puff(ctx, t + i / 5, cx, cy, rx, ry, rmin, rmax);
  }

  function cloud(ctx, t, cx, cy, cw, s, color) {
    t /= 30000;

    var a = cw * 0.21,
        b = cw * 0.12,
        c = cw * 0.24,
        d = cw * 0.28;

    ctx.fillStyle = color;
    puffs(ctx, t, cx, cy, a, b, c, d);

    ctx.globalCompositeOperation = 'destination-out';
    puffs(ctx, t, cx, cy, a, b, c - s, d - s);
    ctx.globalCompositeOperation = 'source-over';
  }

  function sun(ctx, t, cx, cy, cw, s, color) {
    t /= 120000;

    var a = cw * 0.25 - s * 0.5,
        b = cw * 0.32 + s * 0.5,
        c = cw * 0.50 - s * 0.5,
        i, p, cos, sin;

    ctx.strokeStyle = color;
    ctx.lineWidth = s;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    ctx.beginPath();
    ctx.arc(cx, cy, a, 0, TAU, false);
    ctx.stroke();

    for(i = 8; i--; ) {
      p = (t + i / 8) * TAU;
      cos = Math.cos(p);
      sin = Math.sin(p);
      line(ctx, cx + cos * b, cy + sin * b, cx + cos * c, cy + sin * c);
    }
  }

  function moon(ctx, t, cx, cy, cw, s, color) {
    t /= 15000;

    var a = cw * 0.29 - s * 0.5,
        b = cw * 0.05,
        c = Math.cos(t * TAU),
        p = c * TAU / -16;

    ctx.strokeStyle = color;
    ctx.lineWidth = s;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    cx += c * b;

    ctx.beginPath();
    ctx.arc(cx, cy, a, p + TAU / 8, p + TAU * 7 / 8, false);
    ctx.arc(cx + Math.cos(p) * a * TWO_OVER_SQRT_2, cy + Math.sin(p) * a * TWO_OVER_SQRT_2, a, p + TAU * 5 / 8, p + TAU * 3 / 8, true);
    ctx.closePath();
    ctx.stroke();
  }

  function rain(ctx, t, cx, cy, cw, s, color) {
    t /= 1350;

    var a = cw * 0.16,
        b = TAU * 11 / 12,
        c = TAU *  7 / 12,
        i, p, x, y;

    ctx.fillStyle = color;

    for(i = 4; i--; ) {
      p = (t + i / 4) % 1;
      x = cx + ((i - 1.5) / 1.5) * (i === 1 || i === 2 ? -1 : 1) * a;
      y = cy + p * p * cw;
      ctx.beginPath();
      ctx.moveTo(x, y - s * 1.5);
      ctx.arc(x, y, s * 0.75, b, c, false);
      ctx.fill();
    }
  }

  function sleet(ctx, t, cx, cy, cw, s, color) {
    t /= 750;

    var a = cw * 0.1875,
        b = TAU * 11 / 12,
        c = TAU *  7 / 12,
        i, p, x, y;

    ctx.strokeStyle = color;
    ctx.lineWidth = s * 0.5;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    for(i = 4; i--; ) {
      p = (t + i / 4) % 1;
      x = Math.floor(cx + ((i - 1.5) / 1.5) * (i === 1 || i === 2 ? -1 : 1) * a) + 0.5;
      y = cy + p * cw;
      line(ctx, x, y - s * 1.5, x, y + s * 1.5);
    }
  }

  function snow(ctx, t, cx, cy, cw, s, color) {
    t /= 3000;

    var a  = cw * 0.16,
        b  = s * 0.75,
        u  = t * TAU * 0.7,
        ux = Math.cos(u) * b,
        uy = Math.sin(u) * b,
        v  = u + TAU / 3,
        vx = Math.cos(v) * b,
        vy = Math.sin(v) * b,
        w  = u + TAU * 2 / 3,
        wx = Math.cos(w) * b,
        wy = Math.sin(w) * b,
        i, p, x, y;

    ctx.strokeStyle = color;
    ctx.lineWidth = s * 0.5;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    for(i = 4; i--; ) {
      p = (t + i / 4) % 1;
      x = cx + Math.sin((p + i / 4) * TAU) * a;
      y = cy + p * cw;

      line(ctx, x - ux, y - uy, x + ux, y + uy);
      line(ctx, x - vx, y - vy, x + vx, y + vy);
      line(ctx, x - wx, y - wy, x + wx, y + wy);
    }
  }

  function fogbank(ctx, t, cx, cy, cw, s, color) {
    t /= 30000;

    var a = cw * 0.21,
        b = cw * 0.06,
        c = cw * 0.21,
        d = cw * 0.28;

    ctx.fillStyle = color;
    puffs(ctx, t, cx, cy, a, b, c, d);

    ctx.globalCompositeOperation = 'destination-out';
    puffs(ctx, t, cx, cy, a, b, c - s, d - s);
    ctx.globalCompositeOperation = 'source-over';
  }

  var WIND_PATHS = [
        [
          -0.7500, -0.1800, -0.7219, -0.1527, -0.6971, -0.1225,
          -0.6739, -0.0910, -0.6516, -0.0588, -0.6298, -0.0262,
          -0.6083,  0.0065, -0.5868,  0.0396, -0.5643,  0.0731,
          -0.5372,  0.1041, -0.5033,  0.1259, -0.4662,  0.1406,
          -0.4275,  0.1493, -0.3881,  0.1530, -0.3487,  0.1526,
          -0.3095,  0.1488, -0.2708,  0.1421, -0.2319,  0.1342,
          -0.1943,  0.1217, -0.1600,  0.1025, -0.1290,  0.0785,
          -0.1012,  0.0509, -0.0764,  0.0206, -0.0547, -0.0120,
          -0.0378, -0.0472, -0.0324, -0.0857, -0.0389, -0.1241,
          -0.0546, -0.1599, -0.0814, -0.1876, -0.1193, -0.1964,
          -0.1582, -0.1935, -0.1931, -0.1769, -0.2157, -0.1453,
          -0.2290, -0.1085, -0.2327, -0.0697, -0.2240, -0.0317,
          -0.2064,  0.0033, -0.1853,  0.0362, -0.1613,  0.0672,
          -0.1350,  0.0961, -0.1051,  0.1213, -0.0706,  0.1397,
          -0.0332,  0.1512,  0.0053,  0.1580,  0.0442,  0.1624,
           0.0833,  0.1636,  0.1224,  0.1615,  0.1613,  0.1565,
           0.1999,  0.1500,  0.2378,  0.1402,  0.2749,  0.1279,
           0.3118,  0.1147,  0.3487,  0.1015,  0.3858,  0.0892,
           0.4236,  0.0787,  0.4621,  0.0715,  0.5012,  0.0702,
           0.5398,  0.0766,  0.5768,  0.0890,  0.6123,  0.1055,
           0.6466,  0.1244,  0.6805,  0.1440,  0.7147,  0.1630,
           0.7500,  0.1800
        ],
        [
          -0.7500,  0.0000, -0.7033,  0.0195, -0.6569,  0.0399,
          -0.6104,  0.0600, -0.5634,  0.0789, -0.5155,  0.0954,
          -0.4667,  0.1089, -0.4174,  0.1206, -0.3676,  0.1299,
          -0.3174,  0.1365, -0.2669,  0.1398, -0.2162,  0.1391,
          -0.1658,  0.1347, -0.1157,  0.1271, -0.0661,  0.1169,
          -0.0170,  0.1046,  0.0316,  0.0903,  0.0791,  0.0728,
           0.1259,  0.0534,  0.1723,  0.0331,  0.2188,  0.0129,
           0.2656, -0.0064,  0.3122, -0.0263,  0.3586, -0.0466,
           0.4052, -0.0665,  0.4525, -0.0847,  0.5007, -0.1002,
           0.5497, -0.1130,  0.5991, -0.1240,  0.6491, -0.1325,
           0.6994, -0.1380,  0.7500, -0.1400
        ]
      ],
      WIND_OFFSETS = [
        {start: 0.36, end: 0.11},
        {start: 0.56, end: 0.16}
      ];

  function leaf(ctx, t, x, y, cw, s, color) {
    var a = cw / 8,
        b = a / 3,
        c = 2 * b,
        d = (t % 1) * TAU,
        e = Math.cos(d),
        f = Math.sin(d);

    ctx.fillStyle = color;
    ctx.strokeStyle = color;
    ctx.lineWidth = s;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    ctx.beginPath();
    ctx.arc(x        , y        , a, d          , d + Math.PI, false);
    ctx.arc(x - b * e, y - b * f, c, d + Math.PI, d          , false);
    ctx.arc(x + c * e, y + c * f, b, d + Math.PI, d          , true );
    ctx.globalCompositeOperation = 'destination-out';
    ctx.fill();
    ctx.globalCompositeOperation = 'source-over';
    ctx.stroke();
  }

  function swoosh(ctx, t, cx, cy, cw, s, index, total, color) {
    t /= 2500;

    var path = WIND_PATHS[index],
        a = (t + index - WIND_OFFSETS[index].start) % total,
        c = (t + index - WIND_OFFSETS[index].end  ) % total,
        e = (t + index                            ) % total,
        b, d, f, i;

    ctx.strokeStyle = color;
    ctx.lineWidth = s;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    if(a < 1) {
      ctx.beginPath();

      a *= path.length / 2 - 1;
      b  = Math.floor(a);
      a -= b;
      b *= 2;
      b += 2;

      ctx.moveTo(
        cx + (path[b - 2] * (1 - a) + path[b    ] * a) * cw,
        cy + (path[b - 1] * (1 - a) + path[b + 1] * a) * cw
      );

      if(c < 1) {
        c *= path.length / 2 - 1;
        d  = Math.floor(c);
        c -= d;
        d *= 2;
        d += 2;

        for(i = b; i !== d; i += 2)
          ctx.lineTo(cx + path[i] * cw, cy + path[i + 1] * cw);

        ctx.lineTo(
          cx + (path[d - 2] * (1 - c) + path[d    ] * c) * cw,
          cy + (path[d - 1] * (1 - c) + path[d + 1] * c) * cw
        );
      }

      else
        for(i = b; i !== path.length; i += 2)
          ctx.lineTo(cx + path[i] * cw, cy + path[i + 1] * cw);

      ctx.stroke();
    }

    else if(c < 1) {
      ctx.beginPath();

      c *= path.length / 2 - 1;
      d  = Math.floor(c);
      c -= d;
      d *= 2;
      d += 2;

      ctx.moveTo(cx + path[0] * cw, cy + path[1] * cw);

      for(i = 2; i !== d; i += 2)
        ctx.lineTo(cx + path[i] * cw, cy + path[i + 1] * cw);

      ctx.lineTo(
        cx + (path[d - 2] * (1 - c) + path[d    ] * c) * cw,
        cy + (path[d - 1] * (1 - c) + path[d + 1] * c) * cw
      );

      ctx.stroke();
    }

    if(e < 1) {
      e *= path.length / 2 - 1;
      f  = Math.floor(e);
      e -= f;
      f *= 2;
      f += 2;

      leaf(
        ctx,
        t,
        cx + (path[f - 2] * (1 - e) + path[f    ] * e) * cw,
        cy + (path[f - 1] * (1 - e) + path[f + 1] * e) * cw,
        cw,
        s,
        color
      );
    }
  }

  var Skycons = function(opts) {
        this.list        = [];
        this.interval    = null;
        this.color       = opts && opts.color ? opts.color : "black";
        this.resizeClear = !!(opts && opts.resizeClear);
      };

  Skycons.CLEAR_DAY = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    sun(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, color);
  };

  Skycons.CLEAR_NIGHT = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    moon(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, color);
  };

  Skycons.PARTLY_CLOUDY_DAY = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    sun(ctx, t, w * 0.625, h * 0.375, s * 0.75, s * STROKE, color);
    cloud(ctx, t, w * 0.375, h * 0.625, s * 0.75, s * STROKE, color);
  };

  Skycons.PARTLY_CLOUDY_NIGHT = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    moon(ctx, t, w * 0.667, h * 0.375, s * 0.75, s * STROKE, color);
    cloud(ctx, t, w * 0.375, h * 0.625, s * 0.75, s * STROKE, color);
  };

  Skycons.CLOUDY = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    cloud(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, color);
  };

  Skycons.RAIN = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    rain(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
    cloud(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
  };

  Skycons.SLEET = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    sleet(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
    cloud(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
  };

  Skycons.SNOW = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    snow(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
    cloud(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
  };

  Skycons.WIND = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h);

    swoosh(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, 0, 2, color);
    swoosh(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, 1, 2, color);
  };

  Skycons.FOG = function(ctx, t, color) {
    var w = ctx.canvas.width,
        h = ctx.canvas.height,
        s = Math.min(w, h),
        k = s * STROKE;

    fogbank(ctx, t, w * 0.5, h * 0.32, s * 0.75, k, color);

    t /= 5000;

    var a = Math.cos((t       ) * TAU) * s * 0.02,
        b = Math.cos((t + 0.25) * TAU) * s * 0.02,
        c = Math.cos((t + 0.50) * TAU) * s * 0.02,
        d = Math.cos((t + 0.75) * TAU) * s * 0.02,
        n = h * 0.936,
        e = Math.floor(n - k * 0.5) + 0.5,
        f = Math.floor(n - k * 2.5) + 0.5;

    ctx.strokeStyle = color;
    ctx.lineWidth = k;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";

    line(ctx, a + w * 0.2 + k * 0.5, e, b + w * 0.8 - k * 0.5, e);
    line(ctx, c + w * 0.2 + k * 0.5, f, d + w * 0.8 - k * 0.5, f);
  };

  Skycons.prototype = {
    _determineDrawingFunction: function(draw) {
      if(typeof draw === "string")
        draw = Skycons[draw.toUpperCase().replace(/-/g, "_")] || null;

      return draw;
    },
    add: function(el, draw) {
      var obj;

      if(typeof el === "string")
        el = document.getElementById(el);

      // Does nothing if canvas name doesn't exists
      if(el === null)
        return;

      draw = this._determineDrawingFunction(draw);

      // Does nothing if the draw function isn't actually a function
      if(typeof draw !== "function")
        return;

      obj = {
        element: el,
        context: el.getContext("2d"),
        drawing: draw
      };

      this.list.push(obj);
      this.draw(obj, KEYFRAME);
    },
    set: function(el, draw) {
      var i;

      if(typeof el === "string")
        el = document.getElementById(el);

      for(i = this.list.length; i--; )
        if(this.list[i].element === el) {
          this.list[i].drawing = this._determineDrawingFunction(draw);
          this.draw(this.list[i], KEYFRAME);
          return;
        }

      this.add(el, draw);
    },
    remove: function(el) {
      var i;

      if(typeof el === "string")
        el = document.getElementById(el);

      for(i = this.list.length; i--; )
        if(this.list[i].element === el) {
          this.list.splice(i, 1);
          return;
        }
    },
    draw: function(obj, time) {
      var canvas = obj.context.canvas;

      if(this.resizeClear)
        canvas.width = canvas.width;

      else
        obj.context.clearRect(0, 0, canvas.width, canvas.height);

      obj.drawing(obj.context, time, this.color);
    },
    play: function() {
      var self = this;

      this.pause();
      this.interval = requestInterval(function() {
        var now = Date.now(),
            i;

        for(i = self.list.length; i--; )
          self.draw(self.list[i], now);
      }, 1000 / 60);
    },
    pause: function() {
      var i;

      if(this.interval) {
        cancelInterval(this.interval);
        this.interval = null;
      }
    }
  };

  global.Skycons = Skycons;
}(this));