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
  // D3 Word Cloud Implementation by Eric Coopey: http://bl.ocks.org/ericcoopey/6382449
  (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;
      }
  
      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);
  