Re: Testability of Animation from interactions Issue 18

Patrick H. Lauke schrieb am 14.01.2017 18:29:

> On 14/01/2017 16:11, Detlev Fischer wrote:
>> Good point. That parallax scroll would be too specific for an SC is
>> true - one could extend the requirement to any user-initiated
>> animation that affects the entire viewport (or a large part of it)
> 
> So just the whole viewport, and not "1/3 of the viewport"? 
> https://github.com/w3c/wcag21/issues/18#issuecomment-272346989

I think merely from a testing standpoint, the easiest would be to say "at least 1/2 of the viewport". That would be easy to establish visually im most cases
Depending on the type of animation it might still need a reference viewport size (such as 1280 x 768px) at which the SC is found to fail if animation indeed affects only part of the viewport. 

>> whether it is nauseous shifts, swirls, wobbles, colour changes or
>> some other brainchild of the inventive front end designer. My attempt
>> would be to set this class of animation apart from another class
>> focussing on specific 'elements' (changing shape or position when
>> focussed or moved, disappearing in an inverted Aladdin's lamp fashion
>> in some location, etc). That might alleviate the need to talk about
>> the size of the area affected,
> 
> Though you're talking about the entire viewport, so you ARE specifying a 
> size.
> 
>>  which in the absence of further
>> information on the  nature of the movement seems inconclusive.
> 
> But agree, would like to see some empirical evidence of different types 
> of animations and how they can be disruptive/problematic.

Even if we get empirical evidence, types of animation can be so different that we will never be able to drwaw the line would qualify as problematic from a user perspective. Take two hypothetical cases:

(1) As the user moves the mouse, vivid pumping bubbles appear and disappear around it (I hope no one will get the idea to actually build this). The total surface area of animation at any time is well below 1/3 of the viewport, but the animation is highly disruptive and irritating.

(2) A script changes the background of the page slowly and almost imperceptively from a light grey to a light greyish mint tone then to a pale tea tint and back to light grey. Contrast to text is always OK. There IS an animation, it affects the entire viewport, but some might not even notice it and few would find it disruptive. 

Going for 'percentage of viewport affected' alone to make this SC "objectively, replicably testable" we would fail to take into account the actual disruptive quality of the animation.

Having said that, I fear that any attempt to nail down further criteria beyond 'percentage of viewport affected' will be hard to interpret in testing (especially as many aspects of moving content will be difficult to measure) and probably miss all sorts of real life  instances because they will often not fall neatly under what we meant to capture.

So homing in on parallax (maybe describing it in a more abstract fashion, e.g. "presence of miore than one layer moving at different speed or/and in different direction) would at least nail down *some issues* that we know are problematic. The alternative might be to say "Sorry, nice SC, but unfortunately not testable".

Detlev

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> Patrick H. Lauke
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Received on Monday, 16 January 2017 09:38:17 UTC