Intent to Remove: Case-insensitive matching for usemap attribute

[TAMURA, Kent]

Contact emails

tk...@chromium.org

Spec

https://html.spec.whatwg.org/multipage/infrastructure.html#rules-for-parsing-a-hash-name-reference

Summary

"Compatibility caseless" had been applied to usemap attribute matching. The specification was updated so that case-sensitive matching is applied. https://github.com/whatwg/html/commit/6acdb2122298d2bb7bb839c0a61b4e1f9b0f9bc9

For example,

<img usemap="#map1">  <map name="MAP1">...</map>  won't work.

Motivation

"Compatibility caseless" matching is very complicated, and there were no browsers implementing it correctly.  UseCounter proved such complicated algorithm was unnecessary, and even ASCII case-insensitive matching is unnecessary.

Interoperability risk

Firefox: No public signals

Edge: No public signals

Safari: No public signals

Web developers: No signals

Blink will be the first engine to implement the new behavior.  However, web-platform-tests already has automated tests for the new behavior.

Compatibility risk

Low.

According to UseCounters, 0.0002% [1] + [2] of page views will break.

[1] https://www.chromestatus.com/metrics/feature/timeline/popularity/1511

[2] https://www.chromestatus.com/metrics/feature/timeline/popularity/1512

Ongoing technical constraints

None.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux,

Chrome OS, Android, and Android WebView)?

Yes.

OWP launch tracking bug

http://crbug.com/659464

Link to entry on the Chrome Platform Status

https://www.chromestatus.com/features/5760965337415680

Requesting approval to ship?

Yes.

--

TAMURA Kent
Software Engineer, Google

[Chris Harrelson]

LGTM1

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[Rick Byers]

LGTM2

But given that we're first and usage is non-zero, can we have a deprecation message for at least a milestone?

[TAMURA, Kent]

ok, let's have a deprecation period.

[Philip Jägenstedt]

IIUC, no browser already does case-sensitive matching (in HTML documents) here, is that right? https://github.com/whatwg/html/pull/1941#issuecomment-255784034 lists the bugs that were filed, can you write on all three that this is happening in Blink and that if that makes them nervous, now is the time to say so?

LGTM3, and again I think we should be very quick to revert if there are regressions.

LGTM1

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