text: // Word cloud layout by Jason Davies, http://www.jasondavies.com/word-cloud/
  // Algorithm due to Jonathan Feinberg, http://static.mrfeinberg.com/bv_ch03.pdf
  (function(exports) {
    function cloud() {
      var size = [256, 256],
          text = cloudText,
          font = cloudFont,
          fontSize = cloudFontSize,
          fontStyle = cloudFontNormal,
          fontWeight = cloudFontNormal,
          rotate = cloudRotate,
          padding = cloudPadding,
          spiral = archimedeanSpiral,
          words = [],
          timeInterval = Infinity,
          event = d3.dispatch("word", "end"),
          timer = null,
          cloud = {};
  
      cloud.start = function() {
        var board = zeroArray((size[0] >> 5) * size[1]),
            bounds = null,
            n = words.length,
            i = -1,
            tags = [],
            data = words.map(function(d, i) {
              d.text = text.call(this, d, i);
              d.font = font.call(this, d, i);
              d.style = fontStyle.call(this, d, i);
              d.weight = fontWeight.call(this, d, i);
              d.rotate = rotate.call(this, d, i);
              d.size = ~~fontSize.call(this, d, i);
              d.padding = padding.call(this, d, i);
              return d;
            }).sort(function(a, b) { return b.size - a.size; });
  
        if (timer) clearInterval(timer);
        timer = setInterval(step, 0);
        step();
  
        return cloud;
  
        function step() {
          var start = +new Date,
              d;
          while (+new Date - start < timeInterval && ++i < n && timer) {
            d = data[i];
            d.x = (size[0] * (Math.random() + .5)) >> 1;
            d.y = (size[1] * (Math.random() + .5)) >> 1;
            cloudSprite(d, data, i);
            if (d.hasText && place(board, d, bounds)) {
              tags.push(d);
              event.word(d);
              if (bounds) cloudBounds(bounds, d);
              else bounds = [{x: d.x + d.x0, y: d.y + d.y0}, {x: d.x + d.x1, y: d.y + d.y1}];
              // Temporary hack
              d.x -= size[0] >> 1;
              d.y -= size[1] >> 1;
            }
          }
          if (i >= n) {
            cloud.stop();
            event.end(tags, bounds);
          }
        }
      }
  
      cloud.stop = function() {
        if (timer) {
          clearInterval(timer);
          timer = null;
        }
        return cloud;
      };
  
      cloud.timeInterval = function(x) {
        if (!arguments.length) return timeInterval;
        timeInterval = x == null ? Infinity : x;
        return cloud;
      };
  
      function place(board, tag, bounds) {
        var perimeter = [{x: 0, y: 0}, {x: size[0], y: size[1]}],
            startX = tag.x,
            startY = tag.y,
            maxDelta = Math.sqrt(size[0] * size[0] + size[1] * size[1]),
            s = spiral(size),
            dt = Math.random() < .5 ? 1 : -1,
            t = -dt,
            dxdy,
            dx,
            dy;
  
        while (dxdy = s(t += dt)) {
          dx = ~~dxdy[0];
          dy = ~~dxdy[1];
  
          if (Math.min(dx, dy) > maxDelta) break;
  
          tag.x = startX + dx;
          tag.y = startY + dy;
  
          if (tag.x + tag.x0 < 0 || tag.y + tag.y0 < 0 ||
              tag.x + tag.x1 > size[0] || tag.y + tag.y1 > size[1]) continue;
          // TODO only check for collisions within current bounds.
          if (!bounds || !cloudCollide(tag, board, size[0])) {
            if (!bounds || collideRects(tag, bounds)) {
              var sprite = tag.sprite,
                  w = tag.width >> 5,
                  sw = size[0] >> 5,
                  lx = tag.x - (w << 4),
                  sx = lx & 0x7f,
                  msx = 32 - sx,
                  h = tag.y1 - tag.y0,
                  x = (tag.y + tag.y0) * sw + (lx >> 5),
                  last;
              for (var j = 0; j < h; j++) {
                last = 0;
                for (var i = 0; i <= w; i++) {
                  board[x + i] |= (last << msx) | (i < w ? (last = sprite[j * w + i]) >>> sx : 0);
                }
                x += sw;
              }
              delete tag.sprite;
              return true;
            }
          }
        }
        return false;
      }
  
      cloud.words = function(x) {
        if (!arguments.length) return words;
        words = x;
        return cloud;
      };
  
      cloud.size = function(x) {
        if (!arguments.length) return size;
        size = [+x[0], +x[1]];
        return cloud;
      };
  
      cloud.font = function(x) {
        if (!arguments.length) return font;
        font = d3.functor(x);
        return cloud;
      };
  
      cloud.fontStyle = function(x) {
        if (!arguments.length) return fontStyle;
        fontStyle = d3.functor(x);
        return cloud;
      };
  
      cloud.fontWeight = function(x) {
        if (!arguments.length) return fontWeight;
        fontWeight = d3.functor(x);
        return cloud;
      };
  
      cloud.rotate = function(x) {
        if (!arguments.length) return rotate;
        rotate = d3.functor(x);
        return cloud;
      };
  
      cloud.text = function(x) {
        if (!arguments.length) return text;
        text = d3.functor(x);
        return cloud;
      };
  
      cloud.spiral = function(x) {
        if (!arguments.length) return spiral;
        spiral = spirals[x + ""] || x;
        return cloud;
      };
  
      cloud.fontSize = function(x) {
        if (!arguments.length) return fontSize;
        fontSize = d3.functor(x);
        return cloud;
      };
  
      cloud.padding = function(x) {
        if (!arguments.length) return padding;
        padding = d3.functor(x);
        return cloud;
      };
  
      return d3.rebind(cloud, event, "on");
    }
  
    function cloudText(d) {
      return d.text;
    }
  
    function cloudFont() {
      return "serif";
    }
  
    function cloudFontNormal() {
      return "normal";
    }
  
    function cloudFontSize(d) {
      return Math.sqrt(d.value);
    }
  
    function cloudRotate() {
      //return (~~(Math.random() * 6) - 3) * 30;
      return 0;
    }
  
    function cloudPadding() {
      return 1;
    }
  
    // Fetches a monochrome sprite bitmap for the specified text.
    // Load in batches for speed.
    function cloudSprite(d, data, di) {
      if (d.sprite) return;
      c.clearRect(0, 0, (cw << 5) / ratio, ch / ratio);
      var x = 0,
          y = 0,
          maxh = 0,
          n = data.length;
      --di;
      while (++di < n) {
        d = data[di];
        c.save();
        c.font = d.style + " " + d.weight + " " + ~~((d.size + 1) / ratio) + "px " + d.font;
        var w = c.measureText(d.text + "m").width * ratio,
            h = d.size << 1;
        if (d.rotate) {
          var sr = Math.sin(d.rotate * cloudRadians),
              cr = Math.cos(d.rotate * cloudRadians),
              wcr = w * cr,
              wsr = w * sr,
              hcr = h * cr,
              hsr = h * sr;
          w = (Math.max(Math.abs(wcr + hsr), Math.abs(wcr - hsr)) + 0x1f) >> 5 << 5;
          h = ~~Math.max(Math.abs(wsr + hcr), Math.abs(wsr - hcr));
        } else {
          w = (w + 0x1f) >> 5 << 5;
        }
        if (h > maxh) maxh = h;
        if (x + w >= (cw << 5)) {
          x = 0;
          y += maxh;
          maxh = 0;
        }
        if (y + h >= ch) break;
        c.translate((x + (w >> 1)) / ratio, (y + (h >> 1)) / ratio);
        if (d.rotate) c.rotate(d.rotate * cloudRadians);
        c.fillText(d.text, 0, 0);
        if (d.padding) c.lineWidth = 2 * d.padding, c.strokeText(d.text, 0, 0);
        c.restore();
        d.width = w;
        d.height = h;
        d.xoff = x;
        d.yoff = y;
        d.x1 = w >> 1;
        d.y1 = h >> 1;
        d.x0 = -d.x1;
        d.y0 = -d.y1;
        d.hasText = true;
        x += w;
      }
      var pixels = c.getImageData(0, 0, (cw << 5) / ratio, ch / ratio).data,
          sprite = [];
      while (--di >= 0) {
        d = data[di];
        if (!d.hasText) continue;
        var w = d.width,
            w32 = w >> 5,
            h = d.y1 - d.y0;
        // Zero the buffer
        for (var i = 0; i < h * w32; i++) sprite[i] = 0;
        x = d.xoff;
        if (x == null) return;
        y = d.yoff;
        var seen = 0,
            seenRow = -1;
        for (var j = 0; j < h; j++) {
          for (var i = 0; i < w; i++) {
            var k = w32 * j + (i >> 5),
                m = pixels[((y + j) * (cw << 5) + (x + i)) << 2] ? 1 << (31 - (i % 32)) : 0;
            sprite[k] |= m;
            seen |= m;
          }
          if (seen) seenRow = j;
          else {
            d.y0++;
            h--;
            j--;
            y++;
          }
        }
        d.y1 = d.y0 + seenRow;
        d.sprite = sprite.slice(0, (d.y1 - d.y0) * w32);
      }
    }
  
    // Use mask-based collision detection.
    function cloudCollide(tag, board, sw) {
      sw >>= 5;
      var sprite = tag.sprite,
          w = tag.width >> 5,
          lx = tag.x - (w << 4),
          sx = lx & 0x7f,
          msx = 32 - sx,
          h = tag.y1 - tag.y0,
          x = (tag.y + tag.y0) * sw + (lx >> 5),
          last;
      for (var j = 0; j < h; j++) {
        last = 0;
        for (var i = 0; i <= w; i++) {
          if (((last << msx) | (i < w ? (last = sprite[j * w + i]) >>> sx : 0))
              & board[x + i]) return true;
        }
        x += sw;
      }
      return false;
    }
  
    function cloudBounds(bounds, d) {
      var b0 = bounds[0],
          b1 = bounds[1];
      if (d.x + d.x0 < b0.x) b0.x = d.x + d.x0;
      if (d.y + d.y0 < b0.y) b0.y = d.y + d.y0;
      if (d.x + d.x1 > b1.x) b1.x = d.x + d.x1;
      if (d.y + d.y1 > b1.y) b1.y = d.y + d.y1;
    }
  
    function collideRects(a, b) {
      return a.x + a.x1 > b[0].x && a.x + a.x0 < b[1].x && a.y + a.y1 > b[0].y && a.y + a.y0 < b[1].y;
    }
  
    function archimedeanSpiral(size) {
      var e = size[0] / size[1];
      return function(t) {
        return [e * (t *= .1) * Math.cos(t), t * Math.sin(t)];
      };
    }
  
    function rectangularSpiral(size) {
      var dy = 4,
          dx = dy * size[0] / size[1],
          x = 0,
          y = 0;
      return function(t) {
        var sign = t < 0 ? -1 : 1;
        // See triangular numbers: T_n = n * (n + 1) / 2.
        switch ((Math.sqrt(1 + 4 * sign * t) - sign) & 3) {
          case 0:  x += dx; break;
          case 1:  y += dy; break;
          case 2:  x -= dx; break;
          default: y -= dy; break;
        }
        return [x, y];
      };
    }
  
    // TODO reuse arrays?
    function zeroArray(n) {
      var a = [],
          i = -1;
      while (++i < n) a[i] = 0;
      return a;
    }
  
    var cloudRadians = Math.PI / 180,
        cw = 1 << 11 >> 5,
        ch = 1 << 11,
        canvas,
        ratio = 1;
  
    if (typeof document !== "undefined") {
      canvas = document.createElement("canvas");
      canvas.width = 1;
      canvas.height = 1;
      ratio = Math.sqrt(canvas.getContext("2d").getImageData(0, 0, 1, 1).data.length >> 2);
      canvas.width = (cw << 5) / ratio;
      canvas.height = ch / ratio;
    } else {
      // node-canvas support
      var Canvas = require("canvas");
      canvas = new Canvas(cw << 5, ch);
    }
  
    var c = canvas.getContext("2d"),
        spirals = {
          archimedean: archimedeanSpiral,
          rectangular: rectangularSpiral
        };
    c.fillStyle = c.strokeStyle = "red";
    c.textAlign = "center";
  
    exports.cloud = cloud;
  })(typeof exports === "undefined" ? d3.layout || (d3.layout = {}) : exports);
  