元素在滚动时移动到错误的位置

我正在使用这个网站上的色轮选择器，遇到了一个问题。当我在色轮上方添加文本，然后向下滚动并更改色轮颜色时，色轮光标不包含在实际的圆中。（它在另一个地方制作了一个假想的圆圈，色轮光标被限制在那个假想的圆圈中。）

另一个可能与第一个问题有关的问题是，如果你在浏览器中放大，（在chrome:ctrl+中）色轮光标会像固定元素一样保持原位，它会跟随滚动。

如何使色轮光标始终位于圆圈中？

相关代码（JSFiddle中的210-211行）：

hsv_mapCursor.style.left = ((x * r + colorDiscRadius + doc.body.scrollLeft + doc.documentElement.scrollLeft) - 1) + 'px';
hsv_mapCursor.style.top = ((y * r + colorDiscRadius + doc.body.scrollTop + doc.documentElement.scrollTop) - 1) + 'px';

JSFiddle

var Tools = {}, // provides functions like addEvent, ... getOrigin, etc.
  startPoint,
  currentTarget,
  currentTargetHeight = 0;
/* ----------------------------------- */
/* --------- Tool Functions ---------- */
/* ----------------------------------- */
function getOrigin(elm) {
  var box = (elm.getBoundingClientRect) ? elm.getBoundingClientRect() : {
      top: 0,
      left: 0
    },
    doc = elm && elm.ownerDocument,
    body = doc.body,
    win = doc.defaultView || doc.parentWindow || window,
    docElem = doc.documentElement || body.parentNode,
    clientTop = docElem.clientTop || body.clientTop || 0, // border on html or body or both
    clientLeft = docElem.clientLeft || body.clientLeft || 0;
  return {
    left: box.left + (win.pageXOffset || docElem.scrollLeft) - clientLeft,
    top: box.top + (win.pageYOffset || docElem.scrollTop) - clientTop
  };
}
function addEvent(obj, type, func) {
  addEvent.cache = addEvent.cache ||  {
    _get: function(obj, type, func, checkOnly) {
      var cache = addEvent.cache[type] || [];
      for (var n = cache.length; n--;) {
        if (obj === cache[n].obj && '' + func === '' + cache[n].func) {
          func = cache[n].func;
          if (!checkOnly) {
            cache[n] = cache[n].obj = cache[n].func = null;
            cache.splice(n, 1);
          }
          return func;
        }
      }
    },
    _set: function(obj, type, func) {
      var cache = addEvent.cache[type] = addEvent.cache[type] || [];
      if (addEvent.cache._get(obj, type, func, true)) {
        return true;
      } else {
        cache.push({
          func: func,
          obj: obj
        });
      }
    }
  };
  if (!func.name && addEvent.cache._set(obj, type, func) || typeof func !== 'function') {
    return;
  }
  if (obj.addEventListener) obj.addEventListener(type, func, false);
  else obj.attachEvent('on' + type, func);
}
function removeEvent(obj, type, func) {
  if (typeof func !== 'function') return;
  if (!func.name) {
    func = addEvent.cache._get(obj, type, func) || func;
  }
  if (obj.removeEventListener) obj.removeEventListener(type, func, false);
  else obj.detachEvent('on' + type, func);
}
Tools.getOrigin = getOrigin;
Tools.addEvent = addEvent;
Tools.removeEvent = removeEvent;


/* ---------------------------------- */
/* ---- HSV-circle color picker ----- */
/* ---------------------------------- */
// Create HSV-circle Relavent Variables
var hsv_map = document.getElementById('hsv_map'),
  colorDiskWrapper = document.getElementById('colorDiskWrapper'),
  colorDisc = document.getElementById('surface'),
  hsv_mapCover = document.getElementById('cover'),
  hsv_mapCursor = document.getElementById('hsv-cursor'),
  luminenceBarWrapper = document.getElementById('luminenceBarWrapper'),
  hsv_barBGLayer = document.getElementById('bar-bg'),
  hsv_barWhiteLayer = document.getElementById('bar-white'),
  luminanceBar = document.getElementById('luminanceBar'),
  hsv_barcursor = document.getElementById('hsv-barcursor'),
  hsv_barCursors = document.getElementById('hsv-barcursors'),
  hsv_barCursorsCln = hsv_barCursors.className,
  luminanceBarContext = luminanceBar.getContext("2d"),
  colorDiscHeight = colorDisc.offsetHeight,
  colorDiscRadius = colorDisc.offsetHeight / 2;
// generic function for drawing a canvas disc
var drawDisk = function(ctx, coords, radius, steps, colorCallback) {
    var x = coords[0] || coords, // coordinate on x-axis
      y = coords[1] || coords, // coordinate on y-axis
      a = radius[0] || radius, // radius on x-axis
      b = radius[1] || radius, // radius on y-axis
      angle = 360,
      rotate = 0,
      coef = Math.PI / 180;
    ctx.save();
    ctx.translate(x - a, y - b);
    ctx.scale(a, b);
    steps = (angle / steps) || 360;
    for (; angle > 0; angle -= steps) {
      ctx.beginPath();
      if (steps !== 360) ctx.moveTo(1, 1); // stroke
      ctx.arc(1, 1, 1, (angle - (steps / 2) - 1) * coef, (angle + (steps / 2) + 1) * coef);
      if (colorCallback) {
        colorCallback(ctx, angle);
      } else {
        ctx.fillStyle = 'black';
        ctx.fill();
      }
    }
    ctx.restore();
  },
  drawCircle = function(ctx, coords, radius, color, width) { // uses drawDisk
    width = width || 1;
    radius = [
      (radius[0] || radius) - width / 2, (radius[1] || radius) - width / 2
    ];
    drawDisk(ctx, coords, radius, 1, function(ctx, angle) {
      ctx.restore();
      ctx.lineWidth = width;
      ctx.strokeStyle = color || '#000';
      ctx.stroke();
    });
  };
if (colorDisc.getContext) {
  drawDisk( // HSV color wheel with white center
    colorDisc.getContext("2d"), [colorDisc.width / 2, colorDisc.height / 2], [colorDisc.width / 2 - 1, colorDisc.height / 2 - 1],
    360,
    function(ctx, angle) {
      var gradient = ctx.createRadialGradient(1, 1, 1, 1, 1, 0);
      gradient.addColorStop(0, 'hsl(' + (360 - angle + 0) + ', 100%, 50%)');
      gradient.addColorStop(1, "#FFFFFF");
      ctx.fillStyle = gradient;
      ctx.fill();
    }
  );
  drawCircle( // gray border
    colorDisc.getContext("2d"), [colorDisc.width / 2, colorDisc.height / 2], [colorDisc.width / 2, colorDisc.height / 2],
    '#555',
    3
  );
}
// draw the luminanceBar bar
var gradient = luminanceBarContext.createLinearGradient(0, 0, 0, colorDiscHeight);
gradient.addColorStop(0, "transparent");
gradient.addColorStop(1, "black");
luminanceBarContext.fillStyle = gradient;
luminanceBarContext.fillRect(0, 0, luminanceBar.offsetWidth, colorDiscHeight);


// Manage Color Wheel Mouse Events
var renderHSVPicker = function(color) { // used in renderCallback of 'new ColorPicker'
  var pi2 = Math.PI * 2,
    x = Math.cos(pi2 - color.hsv.h * pi2),
    y = Math.sin(pi2 - color.hsv.h * pi2),
    r = color.hsv.s * colorDiscRadius;
  hsv_mapCover.style.opacity = 1 - color.hsv.v;
  // this is the faster version...
  hsv_barWhiteLayer.style.opacity = 1 - color.hsv.s;
  hsv_barBGLayer.style.backgroundColor = 'rgb(' +
    color.hueRGB.r + ',' +
    color.hueRGB.g + ',' +
    color.hueRGB.b + ')';
  var doc = window.document;
  hsv_mapCursor.style.left = ((x * r + colorDiscRadius + doc.body.scrollLeft + doc.documentElement.scrollLeft) - 1) + 'px';
  hsv_mapCursor.style.top = ((y * r + colorDiscRadius + doc.body.scrollTop + doc.documentElement.scrollTop) - 1) + 'px';
  hsv_mapCursor.style.borderColor = hsv_barcursor.style.borderColor = color.RGBLuminance > 0.22 ? 'black' : 'white';
  hsv_barcursor.style.top = (((1 - color.hsv.v) * colorDiscRadius * 2 + doc.body.scrollTop + doc.documentElement.scrollTop) + -7) + 'px';
};
var myColor = new Colors(),
  doRender = function(color) {
    renderHSVPicker(color);
  },
  renderTimer,
  // those functions are in case there is no ColorPicker but only Colors involved
  startRender = function(oneTime) {
    if (oneTime) { // only Colors is instanciated
      doRender(myColor.colors);
    } else {
      renderTimer = window.setInterval(
        function() {
          doRender(myColor.colors);
          // http://stackoverflow.com/questions/2940054/
        }, 13); // 1000 / 60); // ~16.666 -> 60Hz or 60fps
    }
  },
  stopRender = function() {
    window.clearInterval(renderTimer);
  };

// Create Event Functions
var hsvDown = function(e) { // mouseDown callback
    var target = e.target || e.srcElement;
    if (e.preventDefault) e.preventDefault();
    //currentTarget = target.id ? target : target.parentNode;
    if (target === hsv_mapCover || target === hsv_mapCursor || target === hsv_barcursor) {
      currentTarget = target.parentNode;
    } else if (target === hsv_barCursors) {
      currentTarget = target;
    } else {
      return;
    }
    startPoint = Tools.getOrigin(currentTarget);
    currentTargetHeight = currentTarget.offsetHeight; // as diameter of circle
    Tools.addEvent(window, 'mousemove', hsvMove);
    hsv_mapCover.style.cursor = hsv_mapCursor.style.cursor = 'none';
    hsvMove(e);
    startRender();
  },
  hsvMove = function(e) { // mouseMove callback
    var r, x, y, h, s;
    if (currentTarget === colorDiskWrapper) { // the circle
      r = currentTargetHeight / 2;
      x = e.clientX - startPoint.left - r;
      y = e.clientY - startPoint.top - r;
      h = 360 - ((Math.atan2(y, x) * 180 / Math.PI) + (y < 0 ? 360 : 0));
      s = (Math.sqrt((x * x) + (y * y)) / r) * 100;
      myColor.setColor({
        h: h,
        s: s
      }, 'hsv');
    } else if (currentTarget === hsv_barCursors) { // the luminanceBar
      myColor.setColor({
        v: (currentTargetHeight - (e.clientY - startPoint.top)) / currentTargetHeight * 100
      }, 'hsv');
    }
  };
// Initial Rendering
doRender(myColor.colors);
// Adde Events To Objects
Tools.addEvent(hsv_map, 'mousedown', hsvDown); // event delegation
Tools.addEvent(window, 'mouseup', function() {
  Tools.removeEvent(window, 'mousemove', hsvMove);
  hsv_mapCover.style.cursor = hsv_mapCursor.style.cursor = hsv_barCursors.style.cursor = 'pointer';
  stopRender();
});

#wrapper {
  width: 500px;
  height: 500px;
  background-color: pink;
}
#hsv_map {
  width: 540px;
  height: 500px;
  position: absolute;
}
#colorDiskWrapper {
  border-radius: 50%;
  position: relative;
  width: 500px;
}
#cover {
  background-color: black;
  border-radius: 50%;
  cursor: pointer;
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
}
#bar-bg,
#bar-white {
  position: absolute;
  right: 0;
  top: 0;
  width: 15px;
  height: 500px;
}
#bar-white {
  background-color: #fff;
}
#hsv-cursor {
  position: absolute;
  border: 2px solid #eee;
  border-radius: 50%;
  width: 9px;
  height: 9px;
  margin: -5px;
  cursor: pointer;
}
.no-cursor #hsv-cursor,
#hsv_map.no-cursor #cover {
  cursor: none;
  /* also works in IE8 */
  /*url(_blank.gif), url(_blank.png), url(_blank.cur), auto;*/
}
#luminanceBar {
  position: absolute;
  right: 0;
  top: 0;
}
#hsv-barcursors {
  position: absolute;
  right: -7.5px;
  width: 30px;
  top: 0;
  height: 500px;
  overflow: hidden;
  cursor: pointer;
}
#hsv-barcursor {
  position: absolute;
  right: 7.5px;
  width: 11px;
  height: 11px;
  border-radius: 50%;
  border: 2px solid black;
  margin-bottom: 5px;
}

<script src="https://rawgit.com/PitPik/colorPicker/master/colors.js"></script>
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<div id="wrapper">
  <div id="hsv_map">
    <div id="colorDiskWrapper">
      <canvas id="surface" width="500" height="500"></canvas>
      <div id="cover"></div>
      <div id="hsv-cursor"></div>
    </div>
    <div id="luminenceBarWrapper">
      <div id="bar-bg"></div>
      <div id="bar-white"></div>
      <canvas id="luminanceBar" width="15" height="500"></canvas>
      <div id="hsv-barcursors" id="hsv_cursors">
        <div id="hsv-barcursor"></div>
      </div>
    </div>
  </div>
</div>