RE: Jonathan's concern: Zoom in responsive drops content

From: Alastair Campbell [mailto:acampbell@nomensa.com]
Sent: Wednesday, July 6, 2016 10:49 AM


The more I think about it, the more I see a dividing line between desktop & mobile devices.



I know there is a continuum of devices, but the way layout & sizing works is very different depending on the meta-vieewport setting.



When you create a site and set: <meta name="viewport" content="width=device-width">



Browsers divide into two groups: those that use the setting (generally mobile/tablet) and those that don’t (generally desktop).



1.      If a device uses the setting, any level of zoom causes horizontal scrolling. That is by definition as the browser starts by setting the layout to the width of the device. As it does not re-flow, any zoom causes scrolling.



2.      If a device does not use the setting and the screen is over 1000px wide, then 300% without scrolling is easy with media queries.



Therefore I think we will need a note or two on user-agents. Starter for 10:

[Jason] The specification which is intended to address the handling of layout on devices with different viewport sizes and orientations is CSS Device Adaptation Level 1:

https://www.w3.org/TR/css-device-adapt-1/


There is a note in the draft which requests implementation on both “mobile” and “desktop” versions of user agents. It is also made clear that this draft replaces <meta name=”viewport”>, which has apparently never been subject to standardization.



SC X.X.X If text is resized up to 300%* without assistive technology, the layout of the Web page ensures that it can be viewed in its entirety without bi-directional**scrolling, and without loss of content or functionality except for elements of the page where the spatial layout of the content is essential to its use.

Note: If a user-agent fits the layout to the viewport and does not provide a means of reflowing content, the author can ignore the requirement to prevent horizontal scrolling.



[Jason] What happens if (as you pointed out above) some user agents respect the author’s request and others don’t, especially if (as is usual), the author has no control over which user agent the user chooses to bring to the table? Perhaps what you mean is that the requirement is still satisfied if some user agents don’t honor the author’s style sheet or meta element.

Perhaps the right way to handle this would be to include <meta name=”viewport”>, or CSS Device Adaptation, in the set of technologies relied upon for purposes of conformance when the author makes a conformance claim. In that case I don’t think we would need to add a note to the success criterion, except perhaps an advisory comment about the technologies relied upon – and even that, arguably, could be added to the Understanding document or the techniques.



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