Intent to Deprecate: SVGZoomEvent

[David Vest]

Primary eng (and PM) emails

da...@opera.com

Summary

Deprecate the SVGZoomEvent interface and the corresponding onzoom attribute. Show deprecation message to the user when creating the event or when setting up an event handler using onzoom="..." on <svg:svg>. Ideally remove the event later if usage is low enough.

Motivation

SVGZoomEvent doesn't work at all in Blink. It can be created and hooked up using onzoom="..." but it is never fired by the browser.

It has been removed from the SVG 2.0 specification:

https://github.com/w3c/svgwg/issues/21

Compatibility Risk

A httparchive search has been conducted:

https://code.google.com/p/chromium/issues/detail?id=367890#c11

indicating very low usage. From the search it looks likely that the event is possible to remove and unlikely that the deprecation will spam the console.

The interface has been around in WebKit and Blink for a long time. Originates in:

https://bugs.webkit.org/show_bug.cgi?id=10826

Alternative implementation suggestion for web developers

None

Usage information from UseCounter

There is no use counter yet.

OWP launch tracking bug

No OWP launch tracking bug but there is:

https://code.google.com/p/chromium/issues/detail?id=367890

Entry on the feature dashboard

https://www.chromestatus.com/feature/5760883808534528

Requesting approval to remove too?

No. The plan is to show deprecation message and count in M50 and do removal in M51.

[Philip Jägenstedt]

Because it's so unlikely that usage is anything other than ~0, I think it's fine to speculative include the removal milestone in the deprecation message, and go ahead with the removal as soon as the use counter has reached stable. However, a use counter added now will only reach stable in April, after the M51 branch point, so I think the target will have to be M52.

(No LGTMs required.)

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[Rick Byers]

Given that this API has never worked in blink, it should be very unlikely that removing it will break anything.  Still, best to be safe with a deprecation period and use counter.  Deprecating now with a plan to remove in either 51 or 52 is fine with me.

Thanks!

   Rick

[David Vest]

I agree, very unlikely to break anything. There is a CL[1] for just
ripping off the band-aid, but further discussions around creating
instances using document.createEvent('SVGZoomEvent') and such led me
to select the safer path here, since we're hardly in any rush.

[1] https://codereview.chromium.org/1676493002/