title: SVGPanZoom discards original viewBox
body: <p>I am using SVGPanZoom to manage the zooming of an SVG image in my hybrid Android (for all intents and purposes the same behavior as in Chrome) app.  While zooming works well I have found a strange issue.  My original inline SVG element goes like this</p>
  
  <pre><code> &lt;svg id='puzzle' viewBox='0 0 1600 770' preserveAspectRatio='none'
    width='100vw' height='85.5vh' fill-rule='evenodd' clip-rule='evenodd' 
    stroke-linejoin='round' stroke-miterlimit='1.414' 
    xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http:// 
    www.w3.org/1999/xlink'&gt;
  </code></pre>
  
  <p>Initially this SVG element is empty and gets populated programmatically from JavaScript at run time after which I initiate SVGPanZoom as follows</p>
  
  <pre><code>var panZoom = svgPanZoom('#puzzle', 
  {panEnabled:false,controlIconsEnabled:false,
  zoomEnabled:true,dblClickZoomEnabled:true,onZoom:postZoom});
  
  panZoom.refreshRate = 10;
  panZoom.zoomScaleSensitivity = 0.02;
  </code></pre>
  
  <p>The problem I have run into is this - I want my SVG image to fill the available area, <code>100vw x 85.5vh</code>completely to do which I instruct it via the <code>preserveAspectRatio="none"</code>attribute above along with the <code>viewBox="0 0 1600 770" attribute.  I have found that this works - so long as I don't use SVGPanZoom. As soon as I initiate panZoom the</code>zoomBox`attribute gets stripped out and I end up with an image that does not quite behave in terms of its default stretching/filling behavior.</p>
  
  <p>SVGPanZoom is widely used so I assume that this behavior is down to me not quite setting it up properly.  Dipping into the code I have found SVGPanZoom creates a <code>cacheViewBox</code>and then proceeds to remove the original zoomBox attribute.</p>
  
  <p>Which is fine if after that zooming works and the original behavior of the application does not change which is not what I find.  What am I doing wrong here?</p>