html2canvas/src/Support.js

_html2canvas.Util.Support = function (options, doc) {

  function supportSVGRendering() {
    var img = new Image(),
    canvas = doc.createElement("canvas"),
    ctx = (canvas.getContext === undefined) ? false : canvas.getContext("2d");
    if (ctx === false) {
      return false;
    }
    canvas.width = canvas.height = 10;
    img.src = [
    "data:image/svg+xml,",
    "<svg xmlns='http://www.w3.org/2000/svg' width='10' height='10'>",
    "<foreignObject width='10' height='10'>",
    "<div xmlns='http://www.w3.org/1999/xhtml' style='width:10;height:10;'>",
    "sup",
    "</div>",
    "</foreignObject>",
    "</svg>"
    ].join("");
    try {
      ctx.drawImage(img, 0, 0);
      canvas.toDataURL();
    } catch(e) {
      return false;
    }
    _html2canvas.Util.log('html2canvas: Parse: SVG powered rendering available');
    return true;
  }

  // Test whether we can use ranges to measure bounding boxes
  // Opera doesn't provide valid bounds.height/bottom even though it supports the method.

  function supportRangeBounds() {
    var r, testElement, rangeBounds, rangeHeight, support = false;

    if (doc.createRange) {
      r = doc.createRange();
      if (r.getBoundingClientRect) {
        testElement = doc.createElement('boundtest');
        testElement.style.height = "123px";
        testElement.style.display = "block";
        doc.body.appendChild(testElement);

        r.selectNode(testElement);
        rangeBounds = r.getBoundingClientRect();
        rangeHeight = rangeBounds.height;

        if (rangeHeight === 123) {
          support = true;
        }
        doc.body.removeChild(testElement);
      }
    }

    return support;
  }

  return {
    rangeBounds: supportRangeBounds(),
    svgRendering: options.svgRendering && supportSVGRendering()
  };
};