Re: [whatwg] Canvas and color colorspaces (was: WebGL and ImageBitmaps)
What if we could just declare the colour-space that content uses, and allow the browser to make a best-effort translation if the current display uses a different colour-space? This way, we don't need to expose colour profiles or other fingerprinting details to JavaScript code. That code can just declare that it uses Adobe sRGB (which might be the default if not specified?), and the browser can apply a transform as needed depending on the hardware. The declaration could be a MIME-type parameter, for visual content delivered via HTTP, or there could be a Canvas attribute or constructor option. /shrug
[whatwg] APIs to interrogate default outgoing HTTP headers, i.e. Accept-Encoding
I posted this at http://discourse.wicg.io/ a long time ago and forgot to email the list about it, so here goes... ## original post There's currently no good way to determine whether or not a browser / environment supports GZIP-deflated content entirely from the front-end. Servers can interrogate the Accept-Encoding header when they receive the request, but client-side JavaScript cannot see this value at all. This is important when using a CDN that doesn't facilitate selection of appropriately deflated content (e.g. AWS CloudFront). I've had projects where the initial HTML content is dynamically generated only so that the server can pass the Accept-Encoding header back to the client. That way, the client can adjust the other URLs it uses to pick pre-GZIPed files, e.g. blah.js.gz instead of blah.js all the time. I was initially thinking that navigator.acceptEncoding could just be specified to contain the default outgoing value of this header, but it occurred to me that there are probably other headers where this is handy. Should this be a function such as XMLHttpRequest.getDefaultRequestHeaders()? Should all such headers just dangle from the navigator object as in my previous example? ## summary of responses http://discourse.wicg.io/users/stuartpb seemed interested at the time. - it's probably more appropriate to store them in navigator instead of XMLHttpRequest - it's probably a good idea to discuss this with the Fetch specification people - for security reasons, certain headers (e.g. Cookies) should not be available this way
Re: [whatwg] APIs to interrogate default outgoing HTTP headers, i.e. Accept-Encoding
On Tue, 11 Aug 2015 at 08:31 Nils Dagsson Moskopp n...@dieweltistgarnichtso.net wrote: I do not understand that use case. It reads incredibly convoluted to me. The UA controls the transport anyway – it should not make any practical difference to a script how the data is transmitted. My use case is centred around trying to optimise network usage when requesting content from AWS CloudFront backed by S3. I 100% agree with you that this should not be a script's problem. However, it is. When the server (CloudFront in this case) has raw and GZIP'ed copies of content, and no automatic server-side selection between the two, the only way to optimise network usage is for the script to make this determination. Unfortunately, there is no way to gain access to the default Accept Encoding header from JavaScript, which is necessary to figure out whether to download raw of GZIP'ed content. So we currently do more hoop-jumping by serving a dynamic initial HTML, where the server constructing it can reflect the UA's Accept Encoding header back to the client in a generated script tag. It's yucky. Beyond our own need for access to the Accept Encoding header, there may be other use cases that are supported by providing access to other headers. Btw, why can AWS CloudFront not into compressed content? http://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/ServingCompressedFiles.html CloudFront doesn't compress the files itself Amazon S3 doesn't compress files automatically AWS CloudFront will do the right thing if it is backed by a Custom Origin that honours the Accept Encoding header (not S3). We have repeatedly requested improvements from AWS, and they are likely on the way, but we have many hoops to jump until then. When last I checked, many sites using AWS CloudFront and S3, including the first-party AWS Console itself, do not serve GZIP'ed resources, which is sub-optimal. -- Nils Dagsson Moskopp // erlehmann http://dieweltistgarnichtso.net
