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[encrypted-media] Add explicit NOTE to authors that calling requestMediaKeySystemAccess() may lead to user agent UI and other effects

From: None via GitHub <sysbot+gh@w3.org>
Date: Thu, 05 Nov 2015 21:18:48 +0000
To: public-html-media@w3.org
Message-ID: <issues.opened-115376965-1446758324-sysbot+gh@w3.org>
ddorwin has just created a new issue for 
https://github.com/w3c/encrypted-media:

== Add explicit NOTE to authors that calling 
requestMediaKeySystemAccess() may lead to user agent UI and other 
effects ==
We have seen an instance of a third-party library calling 
`requestMediaKeySystemAccess()` with no apparent intent by the host 
site to actually use EME.

In addition to unnecessarily using resources, this may generate a user
 prompt, trigger download of a CDM, and/or cause other user-visible 
impacts on some implementations.

The algorithm and even some of the introductory text make it clear 
that user consent, prompting, etc. should be handled in this 
algorithm, but it might be worth explicitly noting this at the very 
top 
([here](https://w3c.github.io/encrypted-media/#navigator-extension-requestmediakeysystemaccess)
 or [here](requestMediaKeySystemAccess)). This may be especially 
important since `canPlayType()` MSE's and `isTypeSupported()` do not 
have such side effects.

The text might be something like:
>**NOTE**
>Calling this method may have **user-visible effects**, including 
requests for user consent. This method should only be called when when
 the author intends to create and use a `MediaKeys` object with the 
provided configuration.

See https://github.com/w3c/encrypted-media/issues/123
Received on Thursday, 5 November 2015 21:18:51 UTC

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