On Sunday, May 13, 2012 at 5:47 PM, Anant Narayanan wrote:
Interested to see what could be listed here… this is the area of greatest
interop concern, IMO (hopefully it won't be needed at all, as it's only
really useful on extension/proprietary platforms).
Examples include touch, webgl, indexeddb. You're right that it's
possible to use this for proprietary extensions; but there are use cases
for standard web features. The idea is to let the store and runtime have
some control over not allowing the user to purchase/install/launch an
app that is known not to work on their current device.
For instance, if I am browsing for apps on my phone that doesn't support
WebGL, the Mozilla App Marketplace won't let me install any apps that
have that feature listed in required_features. Likewise, the runtime may
prevent launching apps that are known to be incompatible with the
current UA, quire similar to screen_size.
I think this will quickly become unmanageable. It means you need to take the
current web as it is today, freeze it, and then start hiding all future
functionality that can only be enabled through this list (and the list of
things you need to enable grows forever or you end up having to enable
unexpected things, which then may cause security issues that the developer was
not expecting). Hence, features like this should only be used for things that
are sure not to be part of the Web Platform.
This also goes against the trend of responsive design: it means that I can't
make an app that both uses WebGL and falls back to legacy tech because the
store will refuse to install it on my non-webGL-phone. So as a developer, I
would need to release two versions of the same app.
In Widgets, we overcame this issue by allowing features to be declared as
optional. However, some did try to do what you are proposing (e.g., WAC): they
tried to disable Geolocation and only enable it through a feature… this became
a huge issue for implementers (you can't disable it in an Android Webview,
hence you can't implement these requirements using a Webview on Android or
possibly on iOS).
I would say this only be used for proprietary hooks, as is currently done with
Chrome extensions (or with opera extension in the XML equivalent). Features
have a role, but not for enabling/disabling bit of the Web Platform.
--
Marcos Caceres
