On 7/10/19 11:01 PM, Connor Brewster wrote:
Hi David,
It's not clear to me what this option means in terms of what you're
proposing to implement and ship. @supports is a feature that web
developers can use -- and it should clearly match whether the
feature is supported. However, I think what you're suggesting here
is that you might ship the feature only when WebRender is enabled --
I think that's something that requires further discussion, given the
confusion it would cause in the web development world. It also
seems (?) like you're suggesting something else about limiting which
filters are usable to only those that have a GPU implementation in
WebRender -- but it's not clear to me if that's for backdrop-filter
only, or also for the filter property -- when WebRender is enabled.
The idea here is that @supports would reflect whether or not
backdrop-filter and WebRender are enabled. This would allow web
authors to add a fallback style if needed. I do agree that this would
cause some confusion and needs more discussion.
This seems pretty hard to do right / pretty awkward. @supports must
reflect whether the property parses. Not enabling the property if
webrender is not enabled seems hacky, but doable.
But if you have WebRender enabled and your GPU process crashes, going
all the way back to the style system to invalidate everything doesn't
seem trivial / worth the effort. It seems pretty hard actually.
In particular, right now we don't re-parse stylesheets when you toggle
prefs for example (you need to reload or such). But the properties keep
working. In this case the feature would stop working completely, while
you have declarations on the page that set it and can read it via
`cssText` (not via CSSOM anymore though, presumably), and existing
@supports rules would keep matching true.
-- Emilio
With regard to limiting the filters available for backdrop-filter, I was
trying to say that we would need to make sure that support is added to
WebRender for all currently unsupported filters. I do not think it would
be a good idea to ship backdrop-filter with only a subset of filters working.
Currently, the filter property will fallback to the software renderer if an
unsupported filter is encountered, this isn't an option for backdrop-filter if
it is not implemented in the other backends.
-Connor
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