Root svg transform inconsistent with Chromium/Firefox/Inkscape

[reznakt]

I have found that resvg renders this SVG inconsistently with Chromium/Firefox/Inkscape:

<svg xmlns="http://www.w3.org/2000/svg" height="1000" transform="scale(.5)" viewBox="5 5 100 100" width="1000">
  <g>
    <circle cx="10" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <circle cx="20" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <line stroke="black" stroke-width=".1" x1="10" x2="20" y1="10" y2="10"/>
  </g>
</svg>

Here's a comparison of the output of Firefox/Chromium/Inkscape (left) and resvg (right):

I suspect the culprit here is probably the transform on the root SVG coupled with viewBox. I believe the support for transform on the svg element was added in SVG 2 and there have been inconsistencies among implementations in the past (see f.e. https://lists.w3.org/Archives/Public/www-svg/2015May/0024.html).

The output of resvg seems to be equivalent to rendering the following SVG with f.e. Firefox:

<svg xmlns="http://www.w3.org/2000/svg" height="1000" viewBox="5 5 100 100" width="1000">
  <g transform="scale(.5)">
    <circle cx="10" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <circle cx="20" cy="10" r="3" stroke="black" stroke-width=".1"/>
    <line stroke="black" stroke-width=".1" x1="10" x2="20" y1="10" y2="10"/>
  </g>
</svg>

Might be related to #874.

[RazrFalcon]

Hm... interesting. I does seems like this behavior was changed in SVG 2.

The main issue with SVG 2 is that there is no changelog. No one knows what was actually changed in SVG 2.

Seems like SVG 2 mentions root transform here: https://www.w3.org/TR/SVG2/coords.html#TransformProperty We should update our SVG 2 changelog as well.

[yisibl]

Chrome has just implemented “the transform property on the svg element.” https://chromium-review.googlesource.com/c/chromium/src/+/6435957

It needs to be turned on: chrome://flags/#enable-experimental-web-platform-features

This feature enables the application of transformation properties—such as scaling, rotation, translation, and skewing—directly to the