Intent to Remove: The <discard> element

[Fredrik Söderquist]

Primary eng (and PM) emails

f...@opera.com

Summary

The <discard> element is part of the SVG Animations (draft) specification. It provides a way to declaratively remove elements at a specific point in time and be a mechanism for streaming animations.

Motivation

The <discard> element is only implemented in Blink, is not used on the web and adds significant enough implementation complexity.

Interoperability and Compatibility Risk

The <discard> element is only implemented in Blink, and is thus not possible to use interoperably. For most use cases it can be replaced with a combination of animation of the 'display' property and a removal event handler.

Edge: Supported (not in EdgeHTML)

Firefox: Not supported

Safari: Not supported

Alternative implementation suggestion for web developers

For most cases a <discard> can be replaced by a <set> element animating the 'display' property. If removal is needed, the 'beginEvent' ('onbegin' attribute or other event handler) can be used (in contexts where scripts are allowed to run).

Usage information from UseCounter

SVGSMILDiscardElementParsed 0.014217%

SVGSMILDiscardElementTriggered <=0.000001%

The first is triggered by the element constructor while the second is triggered when the effect of the element is applied. Analysis of pages where the first one trigger showed thatthey all appeared to be using (various versions of) VelocityJS, which did an enumeration of properties named "SVG.*Element$" on window and creating such an element and enumerating some IDL attributes on it. SVGDiscardElement does not expose any IDL attributes of its own, so that in turn should be a no-op.

Entry on the feature dashboard

https://www.chromestatus.com/feature/4870172764536832

[Yoav Weiss]

LGTM1 to discard it

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[Chris Harrelson]

LGTM2

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[Daniel Bratell]

LGTM3

/Daniel

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