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Re: ACTION-258

From: Greg Lowney <gcl-0039@access-research.org>
Date: Wed, 16 Dec 2009 22:33:56 -0800
Message-ID: <4B29D0D4.4020402@access-research.org>
To: WAI-UA list <w3c-wai-ua@w3.org>
Thanks, Jim. Here are some thoughts in response.

1. Re the proposed 4.4.1, the document normally says "the user agent user interface" rather than just "the user interface" (even though I wish we could, as the longer version is pretty unwieldy).

2. A possible rewrite of the proposed Intent that could serve as an introduction to the 4.4.a and 4.4.b (and the proposed 4.4.c below):

"The intent of this Success Criterion is to guard against inducing seizures in individuals with photosensitive seizure disorders. Potentially harmful flashes occurs when there is a pair of significantly opposing changes in luminance (general flashing), or a transition to or from a saturated red occurs irrespective of luminance (red flashing). 

"In some cases the user agent may have total control over the rate at which content flashes, such as when rendering the HTML blink element and CSS text-decoration:blink. In other cases the user agent may have the ability to override flash rates specified by content authors. In both cases the user agent can limit the blink rates to rates and color combinations that are extremely unlikely to trigger seizures, either by relying on built-in limits chosen for safety or by giving the user control over the flash parameters."

3. Possible revisions to the examples:

Example for 4.4.a: When rendering HTML content that uses the blink element or the text-decoration:blink, the user agent flashes the content once per second (or any which is less than the three times per second rate at which the risk greatly increases).

Example for 4.4.b: When rendering HTML content that uses the blink element or the text-decoration:blink, the user agent flashes the content at a rate specified in the user preference settings. This allows the user to set it to a rate below their own sensitivity threshold.

4. Proposed additional 4.4.c (as we discussed on last week's conference call):

"Override flash rates: The user has the option to limit the flash rate for any recognized flashing content to less than 3 flashes in any one second. (AAA)

Example: If a Web technology allows the author to specify that an element is to flash at 4 times each second, and this flashing is rendered by the user agent, the user agent either limits the rate to be slower than 3 times per second, or allows the user to turn on such a limit, or allows the user to specify a limit of their own choosing."

	Thanks,
	Greg

-------- Original Message  --------
Subject: ACTION-258
From: Jim Allan <allanj@tsbvi.edu>
To: 'UAWG list' <w3c-wai-ua@w3.org>
Date: Wed, 16 Dec 2009 17:32:33 -0600

ACTION-258 - Rewrite 4.4.1 to include the user interface and default
presentation of recognized flashing Web content never violate and create
user has the option to...

Current: 
4.4.1 Below Threshold: The user interface never violates the general flash
or red flash thresholds.

Proposed: 
Three Flashes or Below Threshold: The user interface does not contain
anything that flashes more than three times in any one second period, or the
flash is below the general flash and red flash thresholds.

NEW #1:
4.4.a
The user agent defined flash rates are less than 3 times in any one second,
for all items for which the user agent has sole control of the rate.<Level
A) 

Intent: The intent of this Success Criterion is to guard against inducing
seizures in individuals with photosensitive seizure disorders. There are
HTML elements and CSS value that cause content to flash at an arbitrary
rate. This flashing rate is only controlled the browser. These elements are
not author configurable, nor does the user have any control of the flashing
rate. Potentially harmful flashes occurs when there is a pair of
significantly opposing changes in luminance (general flashing), or a
transition to or from a saturated red occurs irrespective of luminance (red
flashing). 

Examples:  HTML <blink>, CSS - text-decoration property - 'blink' value 

Resources: 
ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in
Television:
http://www.ofcom.org.uk/tv/ifi/guidance/legacy/vrs_code_notes/flsh_imgs/gn_f
lash.pdf

WCAG20 General Flash and red flash thresholds-
http://www.w3.org/TR/WCAG20/#general-thresholddef 

NEW #2:
4.4.b The user has the option to set flash rates for user agent defined
flash. (Level AAA)

Jim Allan, Accessibility Coordinator & Webmaster
Texas School for the Blind and Visually Impaired
1100 W. 45th St., Austin, Texas 78756
voice 512.206.9315    fax: 512.206.9264  http://www.tsbvi.edu/
"We shape our tools and thereafter our tools shape us." McLuhan, 1964
Received on Thursday, 17 December 2009 06:36:08 UTC

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