/*
 Automatic, anti-aliased rounded corners.
 
 By Steven Wittens
 Based on http://pro.html.it/esempio/nifty/
 
 Note: there is a bug in the pixel coverage calculation for the first pixel in a horizontal run.
 It is now set to 0, which isn't that noticable.
*/

function NiftyCheck() {
  if(!document.getElementById || !document.createElement) {
    return false;
  }
  var b = navigator.userAgent.toLowerCase();
  if (b.indexOf("msie 5") > 0 && b.indexOf("opera") == -1) {
    return false;
  }
  return true;
}

function Rounded(selector, bk, color, sizex, sizey) {
  var i;
  var v = getElementsBySelector(selector);
  var l = v.length;
  for (i = 0; i < l; i++) {
    AddTop(v[i], bk, color, sizex, sizey);
    AddBottom(v[i], bk, color, sizex, sizey);
  }
}

Math.sqr = function (x) {
  return x*x;
};

function Blend(a, b, alpha) {
  var ca = Array(
    parseInt('0x' + a.substring(1, 3)), 
    parseInt('0x' + a.substring(3, 5)), 
    parseInt('0x' + a.substring(5, 7))
  );
  var cb = Array(
    parseInt('0x' + b.substring(1, 3)), 
    parseInt('0x' + b.substring(3, 5)), 
    parseInt('0x' + b.substring(5, 7))
  );
  return '#' + Math.round(ca[0] + (cb[0] - ca[0])*alpha).toString(16)
             + Math.round(ca[1] + (cb[1] - ca[1])*alpha).toString(16)
             + Math.round(ca[2] + (cb[2] - ca[2])*alpha).toString(16);
}

function AddTop(el, bk, color, sizex, sizey) {
  var i, j;
  var d = document.createElement("div");
  d.style.backgroundColor = bk;
  d.className = "rounded";
  var lastarc = 0;
  for (i = 1; i <= sizey; i++) {
    var coverage, arc2, arc3;
    // Find intersection of arc with bottom of pixel row
    arc = Math.sqrt(1.0 - Math.sqr(1.0 - i / sizey)) * sizex;
    // Calculate how many pixels are bg, fg and blended.
    var n_bg = sizex - Math.ceil(arc);
    var n_fg = Math.floor(lastarc);
    var n_aa = sizex - n_bg - n_fg;
    // Create pixel row wrapper
    var x = document.createElement("div");
    var y = d;
    x.style.margin = "0px " + n_bg +"px";
    // Make a wrapper per anti-aliased pixel (at least one)
    for (j = 1; j <= n_aa; j++) {
      // Calculate coverage per pixel
      // (approximates circle by a line within the pixel)
      if (j == 1) {
        if (j == n_aa) {
          // Single pixel
          coverage = ((arc + lastarc) * .5) - n_fg;
        }
        else {
          // First in a run
          arc2 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j + 1) / sizex)) * sizey;
          coverage = (arc2 - (sizey - i)) * (arc - n_fg - n_aa + 1) * .5;
          // Coverage is incorrect. Why?
          coverage = 0;
        }
      }
      else if (j == n_aa) {
        // Last in a run
        arc2 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j + 1) / sizex)) * sizey;
        coverage = 1.0 - (1.0 - (arc2 - (sizey - i))) * (1.0 - (lastarc - n_fg)) * .5;
      }
      else {
        // Middle of a run
        arc3 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j) / sizex)) * sizey;
        arc2 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j + 1) / sizex)) * sizey;
        coverage = ((arc2 + arc3) * .5) - (sizey - i);
      }
      
      x.style.backgroundColor = Blend(bk, color, coverage);
      y.appendChild(x);
      y = x;
      var x = document.createElement("div");
      x.style.margin = "0px 1px";
    }
    x.style.backgroundColor = color;
    y.appendChild(x);
    lastarc = arc;
  }
  el.insertBefore(d, el.firstChild);
}

function AddBottom(el, bk, color, sizex, sizey) {
  var i, j;
  var d = document.createElement("div");
  d.className = "rounded";
  d.style.backgroundColor = bk;
  var lastarc = 0;
  for (i = 1; i <= sizey; i++) {
    var coverage, arc2, arc3;
    // Find intersection of arc with bottom of pixel row
    arc = Math.sqrt(1.0 - Math.sqr(1.0 - i / sizey)) * sizex;
    // Calculate how many pixels are bg, fg and blended.
    var n_bg = sizex - Math.ceil(arc);
    var n_fg = Math.floor(lastarc);
    var n_aa = sizex - n_bg - n_fg;
    // Create pixel row wrapper
    var x = document.createElement("div");
    var y = d;
    x.style.margin = "0px " + n_bg + "px";
    // Make a wrapper per anti-aliased pixel (at least one)
    for (j = 1; j <= n_aa; j++) {
      // Calculate coverage per pixel
      // (approximates circle by a line within the pixel)
      if (j == 1) {
        if (j == n_aa) {
          // Single pixel
          coverage = ((arc + lastarc) * .5) - n_fg;
        }
        else {
          // First in a run
          arc2 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j + 1) / sizex)) * sizey;
          coverage = (arc2 - (sizey - i)) * (arc - n_fg - n_aa + 1) * .5;
          // Coverage is incorrect. Why?
          coverage = 0;
        }
      }
      else if (j == n_aa) {
        // Last in a run
        arc2 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j + 1) / sizex)) * sizey;
        coverage = 1.0 - (1.0 - (arc2 - (sizey - i))) * (1.0 - (lastarc - n_fg)) * .5;
      }
      else {
        // Middle of a run
        arc3 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j) / sizex)) * sizey;
        arc2 = Math.sqrt(1.0 - Math.sqr((sizex - n_bg - j + 1) / sizex)) * sizey;
        coverage = ((arc2 + arc3) * .5) - (sizey - i);
      }
      
      x.style.backgroundColor = Blend(bk, color, coverage);
      y.insertBefore(x, y.firstChild);
      y = x;
      var x = document.createElement("div");
      x.style.margin = "0px 1px";
    }
    x.style.backgroundColor = color;
    y.insertBefore(x, y.firstChild);
    lastarc = arc;
  }
  el.appendChild(d);
}

function getElementsBySelector(selector) {
  var i;
  var s = [];
  var selid = "";
  var selclass = "";
  var tag = selector;
  var objlist = [];
  if (selector.indexOf(" ") > 0) {  //descendant selector like "tag#id tag"
    s = selector.split(" ");
    var fs = s[0].split("#");
    if (fs.length == 1) {
      return objlist;
    }
    return document.getElementById(fs[1]).getElementsByTagName(s[1]);
  }
  if (selector.indexOf("#") > 0) { //id selector like "tag#id"
    s = selector.split("#");
    tag = s[0];
    selid = s[1];
  }
  if (selid != "") {
    objlist.push(document.getElementById(selid));
    return objlist;
  }
  if (selector.indexOf(".") > 0) {  //class selector like "tag.class"
    s = selector.split(".");
    tag = s[0];
    selclass = s[1];
  }
  var v = document.getElementsByTagName(tag);  // tag selector like "tag"
  if (selclass == "") {
    return v;
  }
  for (i = 0; i < v.length; i++) {
    if (v[i].className == selclass) {
      objlist.push(v[i]);
    }
  }
  return objlist;
}