Issue 18 "Animation from interactions" Status Report

Abstract:

This document provides a status report on the "Animation from interactions" Success Criterion (SC) - GitHub Issue 18 - to the WCAG Working Group, January 17, 2017.

The SC is about extending 2.2.2 "Pause, stop hide" to cover another scenario: when a person unexpectedly initiates an animation such as in parallax scrolling. Parallax scrolling involves a background moving at a different speed than foreground content, creating a special effect as a person scrolls down a page. It can trigger nausea and migraines in people with vestibular disorders. Minimal research has been conducted.

The proposed SC text currently is: "For significant animation triggered by a user action that is not an essential part of the action, there is a mechanism for the user to pause, stop or hide the animation whilst still performing the same action." It is fairly generic so it could also include zoom-in effects, slides, horizontal motion, and rotating motion etc. The proposed SC text seems to have consensus from people participating in the discussion.

Overlap with COGA Issue #6 personalization was briefly discussed. Any SC which could be addressed by personalization will overlap with #6, but this one could be avoided by not using animation or be addressed by using a technique other than personalization.

The main area of refinement is testability (size and duration) for incorporating into the "significant animation" definition.

Size

The original SC set size at 1/3 of the view of a "web page". It was pointed out that would be difficult to test. A web page could be 500 ‘pages’ long. Nothing would be 1/3 of it. "Visual field on the screen" as in current WCAG 2.0 definition seems to means the overall size of the screen. So it was suggested to use "viewport " rather than "web page". It was pointed out that "viewport" can be consistently queried and tested (though in context of responsive design, it would need to be tested for each breakpoint/common device screen resolution).

According to Nat Astor, whole-screen motion is the biggest issue, tiny animations are not an issue. 1/3 of the viewport is the point where it can trigger an issue for him.

It was suggested to not use size for testing but to use a class of animation i.e. specific 'elements' changing shape or position when focused or moved etc. It was argued that not specifying a size would in effect be specifying a the entire page as the size.

One proposal is to use "1/2 of the viewport" as that would be easier to test than 1/3.

Duration

Parallax usually lasts as long as you scroll so there is no pre-set upper limit. The duration is the lower limit - not the upper limit like the current animation SC 2.2.2.

Nat Astor has explained that he uses a 'long blink' to cope with auto-scrolls and similar whole-page movement that he isn't controlling. The original 1 second duration came from there. His follow up indicates a although he prefers less (1 second), a longer time might be ok. But we lack wide scale research.

Setting the threshold to 3 seconds allows for most CSS transitions and will save testing time

The latest proposal is to add an "OR" to the duration: "the animation takes more than 1 second or is synchronized with a user action.

For parallax scrolling the animation is continuous for the duration of the interaction. In theory, it can be stopped/last a lot less than 3 seconds purely by virtue of the user stopping to scroll.

Definition

The following definition seems to be developing consensus from people participating in Issue 18. The fraction just needs to be agreed.

Significant animation
animation which continues for more than 3 seconds and affects more than insert fraction [1/2 or 1/3?] of the viewport.

Comments

A Comments page provides relevant input details. (The email thread on WCAG mailing list veered off topic on occasion.)