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Re: Any official clarification on Text-only zoom and RWD?

for

From: Jonathan Avila
Date: Feb 29, 2016 10:28AM

> I'd be careful with the terminology, the browser does not 'change the width of the window', although I think I know what you mean.

What I meant was the window.innerWidth property changes when you zoom. It's equivalent to resizing the window with the caveat below.

> Think of zoom as basically increasing the CSS pixels, so if the browser
(inner) window is 1000px wide, and you zoom to 200%, the window will show 500px of the content.

The innerWidth will change AND the window.devicePixelRatio will also increase. This will cause the text size to increase even when a breakpoint has not been reached. So browser zoom such as the zoom in Chrome causes both a scale change and inner width change that in my opinion could cause unexpected issues in between breakpoints. That's why you'd need to test for zoom even when responsive design is used. You can see this by simply resizing your window and the innerWidth will change but the devicePixelRatio will not.

> Also, I think the wording of the current success criteria would still make that a fail, if you zoom in and the text doesn't increase in size, that's a fail.

Agreed.

>> I totally support text resize without zoom and believe it is a user
>> requirement and need.

> I am still not convinced, it is one of my questions to the Low Vision Task Force [3].

What I meant was I totally support and see the need for zoom without horizontal scrolling. It doesn't matter to me how it's done either through zoom or text resize -- as long as the text can be resized without horizontal scrolling. I think we agree on that.

Jonathan

Jonathan Avila
Chief Accessibility Officer
SSB BART Group
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703.637.8957 (o)
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-----Original Message-----
From: WebAIM-Forum [mailto: <EMAIL REMOVED> ] On Behalf Of Alastair Campbell
Sent: Thursday, February 25, 2016 6:52 AM
To: WebAIM Discussion List
Subject: Re: [WebAIM] Any official clarification on Text-only zoom and RWD?

Jonathan Avila wrote:

> On the desktop at least zooming in the browser changes the width of
> the window and increases the scale.


I'd be careful with the terminology, the browser does not 'change the width of the window', although I think I know what you mean.

Think of zoom as basically increasing the CSS pixels, so if the browser
(inner) window is 1000px wide, and you zoom to 200%, the window will show 500px of the content.

If the site is responsive (or even just 'liquid', percentage based) and there are media queries to adapt to the change, you will not get horizontal scrolling.

> In theory a developer could use fixed font sizes at different break
points or do something that caused the text to change but not actually reach 200% at 200 percent zoom.

Possible but unusual. A developer could specify that text is 20px when the window is 1000px wide, and 10px when the window is 500px wide. However, that would look odd to most people as devices use a relative (physical) size for pixels anyway, so 16px on desktop (at the assumed viewing
distance) should look the same as 16px on a mobile [1].

Also, I think the wording of the current success criteria would still make that a fail, if you zoom in and the text doesn't increase in size, that's a fail.


As an aside on a mobile browser where you can pinch zoom (when not blocked
> by the site or forced by the browser ) the ability to resize text
> alone is restricted to certain browsers or sites that use the system
> fonts that support the text size settings on the platform. So g142
> allows mobile sites to meet the success criteria on small screens
> where text resize alone migh be more difficult.
>

I agree that zooming and/or text sizing on mobile is a real problem [2].
There is more than one solution though, I used to have a feed-reader which would allow you to pinch-zoom on a responsive layout past it's maximum, without causing horizontal scrolling. It just kept everything in one column and within the window-width.



> I totally support text resize without zoom and believe it is a user
> requirement and need.
>

I am still not convinced, it is one of my questions to the Low Vision Task Force [3].

I understand when a site is not responsive zoom causes horizontal scrolling, but if:
- The site is responsive, so you don't get horizontal scrolling.
- It doesn't reduce content or functionality when zoomed.
- You are on a desktop style browser (as far as zoom is concerned)

What does text-sizing help with that zoom doesn't?

Cheers,

-Alastair


1] https://alastairc.ac/2013/02/how-to-hold-your-ipad/
2] https://alastairc.ac/2015/10/zoom-for-fixed-and-responsive-sites/
3]
https://lists.w3.org/Archives/Public/public-low-vision-a11y-tf/2016Feb/0042.html