protocol relative tile urls break file:// URLs

[pagameba]

In the developer's guide, we suggest to users that they can run the examples like this:

Then, either open one of the example html files from the examples directory directly in your browser, or start a simple web server, for example

The recent change to protocol relative urls in #1694, #1692, and #47 removes the ability to load HTML files with the file:// protocol. I suppose the easiest fix is to change that in the developer's guide, but I am not sure this is the best approach.

[elemoine]

+1 for changing the developer guide.

[twpayne]

Note that file:// URLs also don't play well with CORS, so I'm also +1 on changing the developer's guide.

[pagameba]

#1741 might be a good reason to reconsider protocol relative urls in some cases.

[twpayne]

There's an easy work-around for #1741 - see my comment in the issue.

[pagameba]

Should the developer's guide could be updated with this advice for those wishing or needing to use the file:// protocol then?

[twpayne]

It might make more sense to document it in the sources that use protocol-relative URLs.

[pagameba]

How about in both places? Individual sources that use protocol-less URLs by default can mention it and what to use if the page is loaded from file:// and the developer's guide could include a note like this:

If you are loading your page using the file:// protocol instead of via a web server then you may need to set the url property of your source to set the protocol, see API documentation for the source you are using for more details.

Question: would setting the protocol in the source avoid CORS issues, or is this something that would still be a problem?

[twpayne]

OK, makes sense.

As I understand it, CORS simply doesn't work over the file:// scheme.

[pagameba]

Okay, put another way, what won't work because of CORS issues when using the file:// protocol? My poor recollection is that it was something to do with WebGL but ...

[twpayne]

My understanding is that resources loaded from file:// do not have an origin set, and therefore cannot use CORS. I believe that this is related to security sandboxing, but do not know the full details.

[regevbr]

I overcame that issue by creating the following module - https://www.npmjs.com/package/cordova-network-interceptor which intercepts and fixes bad network requests caused by relative protocol used in scripts. Hope that helps!