[webkit-dev] On web-exposing features disabled at runtime

Maciej Stachowiak mjs at apple.com
Mon Feb 10 12:55:37 PST 2014

On Feb 10, 2014, at 10:40 AM, Sergio Villar Senin <svillar at igalia.com> wrote:

> Hi folks,
> I'm sending this to the list because it might affect different
> components inside the project.
> So as smfr correctly reported here[1] for all those features that don't
> have a feature flag (like grid layout) we're web-exposing the CSS
> properties of the feature even if it's disabled at runtime (we're
> exposing them as well for features enabled at build time but disabled at
> runtime).
> If I am not wrong, we just disable the parsing of those properties that
> are not runtime enabled, but the properties are exposed anyway,
> something easy to check doing for example:
> Object.getOwnPropertyDescriptor(document.body.style, property-name).
> The question is whether this is an acceptable behavior or not, and how
> to fix it in case we don't like it. I guess it's safe to conclude that
> it isn't something that we want in general, as it might confuse web
> authors (they see the how properties are available but do nothing).
> Regarding how to fix it, I guess the idea is to do something similar to
> what Eric did in Blink last year[2], i.e., filtering out the list of
> properties that are runtime disabled.

It's not a good behavior, in my opinion. I am not an expert on the CSS parser, but I think we should hide the CSS interface for runtime-disabled features. That would allow us to consider runtime disabling instead of prefixing as a tool for early testing in more cases.

 - Maciej

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