RE: Clarification on what to do when zooming or resizing

Perfect, I think it would be great to standardize these behaviors at some point, but I can understand leaving this out at level 1 since this seems to address the main pain-points of responsive images for devs and doesn't necessarily effect functionality.

Thanks for your time and the quick response,
Greg

From: Yoav Weiss [mailto:yoav@yoav.ws]
Sent: Wednesday, April 9, 2014 2:26 PM
To: Greg Whitworth
Cc: Tab Atkins Jr.; public-respimg@w3.org
Subject: Re: Clarification on what to do when zooming or resizing

Hey Greg,

If the media change is only enough so that it would impact which image the browser would choose inside a single source-set<http://picture.responsiveimages.org/#source-set> (e.g. example 7<http://picture.responsiveimages.org/#examples>), that is entirely UA defined. Personally, I think these images should be downloaded as extremely low priority, unless there are indications that the user prefers to save on bandwidth (user preference, data roaming, battery status, etc).
If the media change impacts the source selection algorithm<http://picture.responsiveimages.org/#select-image-source>, then the UA should (but doesn't have to) download the new image. The UA can probably do that in intervals, to save on re-layouts and intermediate downloads in case that the user is resizing their browser window.
Regarding zoom, that depends on what kind of zoom and how zoom impact the viewport dimensions and DPR (unfortunately that's not something everyone agrees on :/). I don't know what IE does in that aspect.

>From a user's perspective, images in a single source-set are the same image in varying qualities. If the browser decides to avoid the download, the user may see quality differences, but the image would still be the same.
Images in different source-sets are supposed to be differently "art-directed", so providing the user with the wrong image may break the page's layout or make the image unusable.

I hope that makes it clearer. Feel free to ping me if you have any more questions.

Cheers :)
Yoav


On Wed, Apr 9, 2014 at 11:00 PM, Greg Whitworth <gwhit@microsoft.com<mailto:gwhit@microsoft.com>> wrote:
Hey guys,

I don't see anywhere that instructs what a UA should do in the event a user zooms or resizes the browser (sorry if I missed it). Should the UA kick of a new download for the image that matches the new dimensions, or should we only do this at certain times?

Thanks,
Greg