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) {
        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;
    }
  })();

  /* Catmull-rom spline stuffs. */
  /*
  function upsample(n, spline) {
    var polyline = [],
        len = spline.length,
        bx  = spline[0],
        by  = spline[1],
        cx  = spline[2],
        cy  = spline[3],
        dx  = spline[4],
        dy  = spline[5],
        i, j, ax, ay, px, qx, rx, sx, py, qy, ry, sy, t;

    for(i = 6; i !== spline.length; i += 2) {
      ax = bx;
      bx = cx;
      cx = dx;
      dx = spline[i    ];
      px = -0.5 * ax + 1.5 * bx - 1.5 * cx + 0.5 * dx;
      qx =        ax - 2.5 * bx + 2.0 * cx - 0.5 * dx;
      rx = -0.5 * ax            + 0.5 * cx           ;
      sx =                   bx                      ;

      ay = by;
      by = cy;
      cy = dy;
      dy = spline[i + 1];
      py = -0.5 * ay + 1.5 * by - 1.5 * cy + 0.5 * dy;
      qy =        ay - 2.5 * by + 2.0 * cy - 0.5 * dy;
      ry = -0.5 * ay            + 0.5 * cy           ;
      sy =                   by                      ;

      for(j = 0; j !== n; ++j) {
        t = j / n;

        polyline.push(
          ((px * t + qx) * t + rx) * t + sx,
          ((py * t + qy) * t + ry) * t + sy
        );
      }
    }

    polyline.push(
      px + qx + rx + sx,
      py + qy + ry + sy
    );

    return polyline;
  }

  function downsample(n, polyline) {
    var len = 0,
        i, dx, dy;

    for(i = 2; i !== polyline.length; i += 2) {
      dx = polyline[i    ] - polyline[i - 2];
      dy = polyline[i + 1] - polyline[i - 1];
      len += Math.sqrt(dx * dx + dy * dy);
    }

    len /= n;

    var small = [],
        target = len,
        min = 0,
        max, t;

    small.push(polyline[0], polyline[1]);

    for(i = 2; i !== polyline.length; i += 2) {
      dx = polyline[i    ] - polyline[i - 2];
      dy = polyline[i + 1] - polyline[i - 1];
      max = min + Math.sqrt(dx * dx + dy * dy);

      if(max > target) {
        t = (target - min) / (max - min);

        small.push(
          polyline[i - 2] + dx * t,
          polyline[i - 1] + dy * t
        );

        target += len;
      }

      min = max;
    }

    small.push(polyline[polyline.length - 2], polyline[polyline.length - 1]);

    return small;
  }
  */

  /* 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 * 0.5 - 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,
      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 = [
        downsample(63, upsample(8, [
          -1.00, -0.28,
          -0.75, -0.18,
          -0.50,  0.12,
          -0.20,  0.12,
          -0.04, -0.04,
          -0.07, -0.18,
          -0.19, -0.18,
          -0.23, -0.05,
          -0.12,  0.11,
           0.02,  0.16,
           0.20,  0.15,
           0.50,  0.07,
           0.75,  0.18,
           1.00,  0.28
        ])),
        downsample(31, upsample(16, [
          -1.00, -0.10,
          -0.75,  0.00,
          -0.50,  0.10,
          -0.25,  0.14,
           0.00,  0.10,
           0.25,  0.00,
           0.50, -0.10,
           0.75, -0.14,
           1.00, -0.10
        ]))
      ];
  */

  var WIND_PATHS = [
      [
        -0.75,
        -0.18,
        -0.7219,
        -0.1527,
        -0.6971,
        -0.1225,
        -0.6739,
        -0.091,
        -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,
        0.153,
        -0.3487,
        0.1526,
        -0.3095,
        0.1488,
        -0.2708,
        0.1421,
        -0.2319,
        0.1342,
        -0.1943,
        0.1217,
        -0.16,
        0.1025,
        -0.129,
        0.0785,
        -0.1012,
        0.0509,
        -0.0764,
        0.0206,
        -0.0547,
        -0.012,
        -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,
        -0.229,
        -0.1085,
        -0.2327,
        -0.0697,
        -0.224,
        -0.0317,
        -0.2064,
        0.0033,
        -0.1853,
        0.0362,
        -0.1613,
        0.0672,
        -0.135,
        0.0961,
        -0.1051,
        0.1213,
        -0.0706,
        0.1397,
        -0.0332,
        0.1512,
        0.0053,
        0.158,
        0.0442,
        0.1624,
        0.0833,
        0.1636,
        0.1224,
        0.1615,
        0.1613,
        0.1565,
        0.1999,
        0.15,
        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,
        0.089,
        0.6123,
        0.1055,
        0.6466,
        0.1244,
        0.6805,
        0.144,
        0.7147,
        0.163,
        0.75,
        0.18
      ],
      [
        -0.75,
        0.0,
        -0.7033,
        0.0195,
        -0.6569,
        0.0399,
        -0.6104,
        0.06,
        -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,
        -0.017,
        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,
        -0.113,
        0.5991,
        -0.124,
        0.6491,
        -0.1325,
        0.6994,
        -0.138,
        0.75,
        -0.14
      ]
    ],
    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 + 0.5) * 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 || el === undefined) 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() {
      if (this.interval) {
        cancelInterval(this.interval);
        this.interval = null;
      }
    }
  };

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