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

Sergio Villar Senin svillar at igalia.com
Mon Feb 10 10:40:09 PST 2014

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

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.



[1] https://bugs.webkit.org/show_bug.cgi?id=128271
[2] https://codereview.chromium.org/14324009

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