Please see the jsfiddle
sample output:
offset based on svg x:12 y:34
mouse click based on screen x:22 y:38
mouse coord based on svg x:10 y:4
The above sample output is generated when I click on the rectangle on the top-left corner.
As far as I understood, getScreenCTM interface provides the transformation matrix for the element (svg here). I got it as the first line. Second line indicate the mouse coordinate based on the screen coordinate. When I apply the transformation matrix to the mouse click, I expect the point will be translated to svg coordinate. That value is the 3 rd line above. I am not sure that it is correct. The rectangle has a y coordinate 10, and the click event is only availbake within the rectangle. So how could the mouse coord based on svg go below 10??
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE HTML><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
</head>
<body>
<meta http-equiv="content-type" content="application/xhtml+xml; charset=utf-8" />
<h1>sdsd</h1>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" baseProfile="full" height="200">
<g fill="none" stroke="black" stroke-width="1" >
<!-- Draw the axes of the original coordinate system -->
<line x1="0" y1=".5" x2="400" y2=".5" />
<line x1=".5" y1="0" x2=".5" y2="150" />
</g>
<g >
<rect class="drag resize" x="10" y="10" width="100" height="50" fill="#c66" />
</g>
</svg>
<h2 id="op"></h2>
<script type="text/javascript" src="vb.js"></script>
</body>
</html>
var svg = document.getElementsByTagName('svg')[0];
var svgNS = svg.getAttribute('xmlns');
var pt = svg.createSVGPoint();
var el1 = document.getElementsByTagName('rect')[0];
var log_svgcursorPoint,
log_mouseclick,
log_mousecoord;
function svgcursorPoint(evt){
pt.x = evt.clientX; pt.y = evt.clientY;
var a = svg.getScreenCTM();
log_svgcursorPoint = "offset based on svg"+ " x:" + a.e +" y:" + a.f;
var b = a.inverse();
return pt.matrixTransform(b);
};
(function(el){
el.addEventListener('mousedown',function(e){
log_mouseclick = "mouse click based on screen"+ " x:" + e.clientX +" y:" + e.clientY ;
var svgmouse = svgcursorPoint(e);
log_mousecoord = "mouse coord based on svg"+ " x:" + svgmouse.x +" y:" +svgmouse.y;
document.getElementById('op').innerHTML = log_svgcursorPoint + "<br>" + log_mouseclick + "<br>" + log_mousecoord;
},false);
})(el1);
seems like a defect, depending on the browser zoom level. Raised an issue http://code.google.com/p/chromium/issues/detail?id=81995