[svgwg] Defining Viewport-percentage lengths for SVG Elements in CSS sizing properties (#1019)

goldenboy777 has just created a new issue for https://github.com/w3c/svgwg:

== Defining Viewport-percentage lengths for SVG Elements in CSS sizing properties ==
In SVG, width and height being presentation attributes can take several types of CSS values, one of these types of values include viewport-percentage units like **vw,vh,vmax,vmin** etc.
But for viewport-percentage units, the ambiguity of resolution is because certain SVG elements creates their own viewport so which viewport to select for resolution is not very clear in any spec, furthermore [css spec](https://www.w3.org/TR/css-values-4/#viewport-relative-lengths) says that viewport percent lengths should be resolved against [ICB](https://www.w3.org/TR/CSS2/visudet.html#containing-block-details), but the definition of ICB is ambiguous for SVG elements as they generally don't generate CSS box model.
Many popular browsers like Chromium, Safari, Firefox already has a defined/similar implementation of resolving viewport-percentage units for SVG elements. If possible, we want that already implemented behaviour to be clearly specified in a spec.

For example, **Chromium, for SVG elements resolves the viewport-percentage units against the ICB if available otherwise against the browser's viewport**
We would like other browser vender's opinions on the same, as to what should go in the spec.

Please view or discuss this issue at https://github.com/w3c/svgwg/issues/1019 using your GitHub account


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Received on Thursday, 2 October 2025 12:05:10 UTC