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ACTION-720: Ensure disabling images gets in 2.11 (Provide control of content that may reduce accessibility)

From: Greg Lowney <gcl-0039@access-research.org>
Date: Thu, 13 Dec 2012 02:40:50 -0800
Message-ID: <50C9B0B2.8090805@access-research.org>
To: WAI-UA list <w3c-wai-ua@w3.org>
Before I start, note that the Intent paragraph and Examples in the current draft for 1.1.1 (Render Alternative Content) are actually about 1.3.1.d (Highlight Items: item with alternative content). I've added a new, more appropriate Intent paragraph for 1.1.1 below, but we need to write more examples. Also, in the first example that *was* listed for 1.1.1 I recommend putting the final sentence in parentheses so it does not confuse the user, who may well wonder what it has to do with 1.3.1, when in fact it's merely about how a separate SC interacts with the technique described in the example.

Also note that below I change most reference to "alternative content" to "alternative content or placeholders". That's because the glossary is a little vague on whether placeholder are examples of alternative content. All the example of "alternative content" are author-provided, while "placeholders" are described as being repair content generated by the user agent. The latter are not explicitly said to be included in "alternative content", but are said to be in the "alternative content stack", which clearly indicates (correctly, I think) that they can often be useful and should be treated as alternative content, especially when the author hasn't provided any themselves.

That being said, here are some thoughts and proposed wording changes rendering or hiding of images, and access to their alternative content. Feel free to disagree or disregard if you think it's too late, or just wrong, but I do think the current SC are not really, properly addressing what they should. In the end I'm just replacing one SC (2.11.1) with another (a new 1.1.x), and clarifying a few others.

The current image-related success criteria can be summarized as:
o    1.1.1 at Level A lets the user replace selected non-text elements with their choice of available alternative content;
o    1.1.2 at Level AA lets the user specify one type of alternative content that, if present, will be displayed with or replace (user agent's choice) all corresponding non-text content;
o    1.1.4 at Level AAA lets the user specify a cascade of alternative content types for 1.1.2;
o    2.11.1 at Level A lets the user toggle display of background images (whether they are replaced by anything is up to the user agent, and there is no requirement on access to any alternative content for them).

The proposal below would result in the summary of image-related success criteria becoming summarized as:
o    1.1.1 at Level A lets the user replace selected non-text elements with their choice of available alternative content or placeholder;
o    1.1.x at Level A would let the user have all recognized non-text content replaced by alternative content or placeholders (user agent's choice, although at Level AA 1.1.2 would let the user specify one preferred type, and at Level AAA 1.1.4 would let the user specify a cascade of types);
o    1.1.2 at Level AA would modify 1.1.x to let the user specify one type of alternative content or placeholder that, if available, will replace all corresponding non-text content (as before, having no effect on content elements for which the author has not provided the specified type of alternative content);
o    1.1.4 at Level AAA would modify 1.1.x to let the user specify a cascade of alternative content and placeholder types;
o    (2.11.1, Background Image Toggle, can be deleted, as it is now subsumed into 1.1.x.)

Here is proposed wording, with changes enclosed by asterisks, deletions enclosed by square brackets, and aside comments in curly braces:

Modify 1.1.1 to read: Render Alternative Content: For any content element, the user can choose to render any types of *recognized* alternative content *or placeholder* that are present. (Level A)

{We could replace the word "render" with "replace that element with", making replace the required default and supplement being an optional extra, or we could continue leaving the minimum choice up to the developer, even though in some cases that would force the user to temporarily turn off all images just to work around one image that is posing difficulties for them.}

{Question: do we need to restrict this to visual elements, or is it reasonable to expect the user agent to provide alternative UI for, as an example, getting recognized information about an audio file being played?}

Add *Note: It is recommended that the user agent allow the user to choose whether the alternative content replaces or supplements the original content element.*

Add *Intent for 1.1.1: Some users with disabilities may find specific images, videos, or other content elements unusable or painful, or that such elements make the page difficult to use because of their size. In these cases they need the ability to either hide the element when it is painful or makes the page difficult to view, and/or get access to alternative content that will be more usable for them than the original element. Users with some disabilities may find a specific content element causes them physical pain (e.g. an image with high contrast) or distress (e.g. an image that triggers post traumatic stress disorder), or that the element's size may make the page difficult to use (because of difficulty scrolling, or shifting gaze, or moving the pointer more than a certain distance). In these cases the user needs to be able to hide that element or replace it with alternative content or a placeholder. Other users may find specific elements are simply unusable (e.g. an image 
that is too low contrast for the user's vision). In these cases the user needs to be able to access author-provided alternative content (e.g. Alt text or Longdesc) or the very minimum a placeholder (e.g. filename).*

Add *Note: If the user cannot directly select or choose the element in order to perform commands upon it (e.g. if the browser does not support clicking on HTML background images or moving focus to them with the keyboard), the user agent must provide an alternative user interface for this feature.*

Add to Examples for 1.1.1: *Rodney has low vision and finds some images on a web page are painful to look at. He can hide foreground images by right-clicking on them or pressing the Tab key to move focus to them, and then choosing a command from the element's context menu. However, the browser does not let him right-click or navigate to the background image. Therefore it provides a user preference setting to hide all background images or to hide the background image on the current site.*

Add *1.1.x Replace Non-Text Content: The user can have all recognized non-text content replaced by alternative content or placeholders. (Level A).*

Add *Note: At Level A, the user agent can choose which type of alternative content or placeholder is used to replace the non-text content. However, at Level AA success criterion 1.1.2 will require that the user be allowed to specify one format or placeholder that will be used, and at Level AAA success criterion 1.1.4 will require the user be allowed to specify a cascade order of formats to be rendered.*

Add: *Intent for 1.1.x: Users may wish to hide images for a number of different reasons. Some users with cognitive disabilities may wish to hide images in order to avoid those that would be severely distracting. Some users with visual disabilities may wish to hide images in order to avoid those that are painful (such as those with high contrast). Other users may wish to replace images with alternative content because they are unlikely to be able to visually discern, understand, or otherwise benefit from the images. Some users with impaired motion or dexterity may wish to replace images with smaller alternative content to reduce the amount of scrolling they have to do, while some users with attention deficit disorder may wish to do the same thing in order to keep as much information visible on the screen as possible.*

To the Wiki add *Implementation Examples for 1.1.x: The Blackberry browser, Chrome, Firefox, IE, Opera, and Safari all provide this option; I have not found a browser that does not.*

Modify 1.1.2 to read: 1.1.2 Configurable Alternative Content Defaults: For each type of non-text content, the user can specify a type of alternative content *or placeholder* that, if present, will be rendered by default. (Level AA)

Add *Note: Success criterion 1.1.2 adds additional required options to success criterion 1.1.x Replace Non-Text Content.*

{I would actually support removing 1.1.2 because it is all but useless: the user has to guess which format will be available for the images he or she wants to replace, and for all other images it doesn't help at all. It's as broken as only requiring the use be able to choose one image format to affect (e.g. JPEG, or PNG, or TIFF, etc.) while all other are ignored, or only replacing images whose filenames--arbitrarily assigned by the author--start with a specified letter.}

Modify 1.1.4 slightly to read: Default Rendering of Alternative Content (Enhanced): For each type of non-text content, the user can specify the cascade order in which to render different types of alternative content *or placeholders* when preferred types are not present. (Level AAA)

Add *Note: Success criterion 1.1.4 adds additional required options to success criterion 1.1.x Replace Non-Text Content.*

Delete [2.11.1 Background Image Toggle: The user can have all recognized background images shown or hidden. (Level A)] {It is subsumed into 1.1.x.}

     Thanks,
     Greg
Received on Thursday, 13 December 2012 10:41:24 GMT

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