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Re: Use URL data: scheme in presentationUrl

From: Kostiainen, Anssi <anssi.kostiainen@intel.com>
Date: Fri, 10 Apr 2015 13:56:52 +0000
To: "Bassbouss, Louay" <louay.bassbouss@fokus.fraunhofer.de>
CC: "public-secondscreen@w3.org" <public-secondscreen@w3.org>
Message-ID: <8E5F7859-48D7-417D-967D-E676339ACC6D@intel.com>
Hi Louay, All,

> On 10 Apr 2015, at 11:25, Bassbouss, Louay <louay.bassbouss@fokus.fraunhofer.de> wrote:
> What do you thing about using “data:”  scheme in presentationUrls e.g. “data:text/html;charset=utf8;base64,<base64 encoded inline html content goes here>”? Example:
> var presentationUrl  = 
> “data:text/html;charset=utf8;base64,PGh0bWw+DQo8aGVhZD48dGl0bGU+VGVzdDwvdGl0bGU+PC9oZWFkPg0KPGJvZHk+DQo8aDE+UHJlc2VudGF0aW9uIEFQSSB3aXRoIGRhdGE6IHNjaGVtZTwvaDE+DQo8L2JvZHk+DQo8L2h0bWw+”;
> var session = navigator.presentation.startSession(presentationUrl );
> The following screenshot shows the output If you open the presentationUrl in browser (tested in chrome);

That is a good question.

Whatever we decide, we should specify the expected behaviour in order to allow the implementations to interoperate after we've figured out whether the API should work with data URIs.

I think there may be a disagreement among implementers whether data URIs are same-origin depending on where they're used (Worker, iframe, img, open()...). I think the closest existing API to startSession() where data URIs can be used is open().

I think the primary motivation for using data URIs has been performance. HTTP/1.x has known limitations in loading multiple resources concurrently, so inlining all the resources has improved the performance. Another use case I can think of is to be able to provide a single file that contains all the resources without the need to package multiple files together.

The base64 encoding is required for binary data only, so in this API we could use text/html to make the markup human-readable:

startSession('data:text/html,<!DOCTYPE html><html><body><p>Test</p></body></html>')

Louay, All - I think you should investigate this further and come up with a recommendation on how to proceed i.e. whether data URIs should be allowed or not, and how to spec that. Please feel free to open a GH issue for tracking this.


-Anssi (WG chair)

Received on Friday, 10 April 2015 13:57:26 UTC

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