'Any workaround to this Firefox bug? SVGElement.getScreenCTM incorrect when parent element has a transform

The Firefox bug in question is https://bugzilla.mozilla.org/show_bug.cgi?id=1610093

It's a long-standing issue whereby the getScreenCTM method of an SVG element returns incorrect values when a parent above the root SVG element has a transform applied.

The following snippet should show the black circle directly under the mouse pointer inside the red box. This works correctly in webkit/blink where the css transform on the parent is properly calculated. In Firefox this bug causes the black circle to be offset by the same values as the css transform on the parent div element.

I've avoided the issue up until now by ensuring there are no transforms further up the dom tree, but I'm now developing this as a component where I won't have control over the parent dom.

Does anyone know an easy workaround for getting a correct transform matrix?

const svgEl = document.querySelector(`svg#test-1`);
const circleEl = document.querySelector(`svg#test-1 circle`);

const handleMouseMove = (e) => {

  // transform screen to SVG coordinate space
  const mousePoint = svgEl.createSVGPoint();
  mousePoint.x = e.clientX;
  mousePoint.y = e.clientY;

  const mouseCoordsInCanvasSpace = mousePoint.matrixTransform(svgEl.getScreenCTM().inverse())
  // set circle to coords, should be mouse center in SVG coord space 
  circleEl.setAttributeNS(null, 'cx', mouseCoordsInCanvasSpace.x);
  circleEl.setAttributeNS(null, 'cy', mouseCoordsInCanvasSpace.y);
}

window.addEventListener('mousemove', handleMouseMove);

body{
  padding: 0px;
  margin: 0px;
}
svg {
  border: 2px solid red;
  margin-left: 0px;
}

<!DOCTYPE html>
<html>
<body>
  <div style="transform: translate(50px, 50px);">
    <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100" id="test-1"> 
      <circle r="10" />
    </svg>
  </div>
</body>
</html>

Solution 1:^[1]

That is an annoying bug! My suggestion is to use an <object> element. The source/data for the object should be the SVG.

In the following example I'm using a data URL as a data source for the <object>, so that we at least can see something here on ST. But I imagine that the SVG should be dynamic somehow. So, to make this work you will need to load the SVG as a source of a file (data="/file.svg"). If you do that you have access to the contentDocument property on <object> and in that way you have direct access to the DOM of the SVG from the "outside". It needs to run from a web server and on the same domain as well.

body{
  padding: 0px;
  margin: 0px;
}

object {
  border: 2px solid red;
  margin-left: 0px;
}

<div style="transform: translate(50px, 50px);">
  <object width="100" height="100" type="image/svg+xml" data="data:image/svg+xml;base64,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"></object>
</div>

Here is the SVG I use in the <object>:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
  <script type="text/javascript">
    <![CDATA[
    var circleEl;
    
    const handleMouseMove = e => {
      const mousePoint = new DOMPoint(e.clientX, e.clientY);  
      const mouseCoordsInCanvasSpace = mousePoint.matrixTransform(e.target.getScreenCTM().inverse());
      circleEl.setAttributeNS(null, 'cx', mouseCoordsInCanvasSpace.x);
      circleEl.setAttributeNS(null, 'cy', mouseCoordsInCanvasSpace.y);
    };

    document.addEventListener('DOMContentLoaded', e => {
      circleEl = document.getElementById('c1');
      document.addEventListener('mousemove', handleMouseMove);
    });
    ]]>
  </script>
  <circle id="c1" r="10" />
</svg>

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1

'Any workaround to this Firefox bug? SVGElement.getScreenCTM incorrect when parent element has a transform

Solution 1:[1]

Sources

Related Questions

Solution 1:^[1]