Just to update, tested this on Mac OS 10.12.6 using canary 63.0.3207.0. Navigating to http://output.jsbin.com/jahogej/2 on Mac and clicking the image doesn't do anything. Similar behavior is observed on 50.0.2624.0.

However the same URL when navigated on Mac Firefox, shows the page as expanded image.

oliverjash@: Could you please confirm if this works fine anywhere and the observations above is seen at your end as well?

Thank you!

 

Clicking the image mutates the `sizes` attribute, which (I believe) should create a new image request with updated client hints, but it does not. If you inspect the DOM before and after clicking the image, you will see this attribute change. You can also monitor network requests to see there is no new request.

Client hints are not supported in Firefox, so I would not expect this example to work at all there.

Thank you for providing more feedback. Adding requester "ajha@chromium.org" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

I suspect the issue is that the "sizes" attribute is defined to have no effect when srcset is not present. We can look at this, but it seems like it might be a spec problem.

I agree that your interpretation of what should happen is probably correct.

Just be clear I understand, as I am not familiar with this spec.

Is the following correct? In theory we should request a new image when the viewport changes or the width of the image changes. Since there is no explicit size for the image, we should be taking the intrinsic size from the "sizes" attribute. So when you change sizes we should re-request the image.

What happens if you give an explicit image width and change that?

I believe that to be correct. This already works when you provide a srcset, but not when using client hints.

If the image has an explicit width (e.g. a CSS width), the browser should still request an image with the size defined by `sizes`?

Assigning to igrigorik@, who presumably knows the spec.

I would expect that an explicit width change would result in a new request. My point is that a new request should probably be made when the display pixels changes (the destination rect for painting the picture).

Hmm, I think this may be a gray and unspecified area in the spec and implementation.

<img id="myImg" sizes="800px" src="https://assets.imgix.net/unsplash/bridge.jpg?ch=Width,DPR">

Per HTML spec, without srcset sizes is a no-op while, of course, with CH the idea is that you should be able to omit it. I have a feeling that we're short-circuiting the processing here.. without accounting for CH. 

Paging Yoav for sanity check.. :-)

The NextAction date has arrived: 2017-09-18