[webkit-dev] Removing support for CSS regions

Ryosuke Niwa rniwa at webkit.org
Tue Aug 15 11:44:15 PDT 2017

On Tue, Aug 15, 2017 at 10:56 AM, Geoffrey Garen <ggaren at apple.com> wrote:
> Given my concern is the compatibility, not the maintenance cost, what
> is the evidence that nobody is relying on this feature?
> It’s difficult to prove a negative. Impossible, in fact.
> Can anyone present evidence of a major client of CSS regions?
> If not, I think that lack of evidence — in combination with the lack of
> support for CSS regions in other browsers — is the best we’ll be able to do
> to know that the feature can be removed.
> Disabling at runtime might give us a little more information, but we don’t
> have a huge beta population and app developers don’t test against trunk
> WebKit, so it’s not that much information. Also, adding runtime
> enable/disable checks for a fundamental layout feature moves in the opposite
> direction of the goal, which is to simplify the code.
> Maybe a compromise path is to disable parsing of CSS regions at compile
> time, but leave all the code in place, and then remove all the code after a
> Safari Technology Preview ships without incident. Would you feel better
> about that than just removing CSS regions right away?

Sure. Disabling the feature for a few STP releases would be a great
start. Meanwhile we can reach out to folks who maintain iBooks, etc...
to figure out if there's any epub content that relies on CSS regions,

- R. Niwa

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