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I am working on a site that gradually changes opacity on page text from 0 at the bottom of the viewer to fully visible by the time the user scroll has positioned the text mid-view. The text is able to be read by a screen reader. It also would meet contrast requirements once it reaches full opacity. Can anyone tell me if this violates WCAG 2.0 standards?

Jason
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Sincerely, this is a very good question.

There is visible text on screen which is not readable and this requires the user to scroll in order to give it full opacity.

From a "visually" point of view, this is not choking. Despite that you are reducing vertical readable area, as long as you can zoom up to 200%, and still read upper lines, this might be acceptable depending on the size of the occulted area from a WCAG view...

The fact that this text is readable by a screenreader is a good point among a lot of accessibility considerations.

If you consider some visual or mental disabilities, this might be hard to understand. For instance, an old person with a glaucoma can not perceive that the effect of gradual change of opacity is not something caused by the disease. Requiring the text they read to be at the centre of the screen is not something evident. Do we move a book from up to down each time we read a line of it?

This also requires more scrolling, so it will ask more physical efforts to read. One click is not very much effort for many people, but clicking on the small arrow of a scrollbar is fairly hard for the elder generation (not everyone uses keyboard).

TL;DR: This might be considered valid from a WCAG point of view, but this does not help ergonomics

Adam
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I think that this would violate the Contrast (1.4.3) criterion on the WCAG 2.0. Your text provides sighted users with a visual cue that color-blind users may not be able to see. It's possible that the text may be unperceivable to color-blind users until the minimum contrast requirement is reached.

The only exceptions to the color contrast criterion are if your text is incidental (i.e. decorative or invisible to users in general). I don't think this text could be considered incidental, however, since it sounds like it is the body content of the page and it remains (at least to some degree) visible to fully sighted users without requiring them to scroll through the content.

JoPinsy
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  • Thanks for the link. In reviewing the section about providing sufficient technique http://www.w3.org/TR/2015/NOTE-WCAG20-TECHS-20150226/G174, it looks like by providing control to achieve sufficient contrast, it would be compliant. I am now thinking that scrolling would do that, and if in-page links take users to the content, it could be targeted in such a way to be shown with full contrast if arriving via the link. – Jason Nov 12 '15 at 19:35
  • That's a very good point. I believe you are correct; I'd assumed that this technique implied that all the content had to be visible at once, but it seems like it is not specific in that regard. If you have a mechanism that allows the content to be shown in its entirety with conforming contrast, then all of your bases should be covered. – JoPinsy Nov 12 '15 at 20:49