- From: Ian Jacobs <ij@w3.org>
- Date: Sun, 10 Sep 2000 20:01:57 -0400
- To: w3c-wai-ua@w3.org
Hello, Per my action item of the 7 September 2000 teleconference [1], here is a proposal for aligning the audio, video, and animation requirements of Guidelines 3 and 4 with the discussions during the last teleconference. This email is in five parts: background, summary of issues, proposals for guideline 3, proposals for guideline 4, and a proposed new checkpoint about accessible generated content. URIs are at the end of the email. The checkpoint numbers given here are those of the 1 September draft [2]. 1) BACKGROUND The previous time we had this discussion about Guidelines 3 and 4 was 27 July [3]. At that time, the Working Group adopted a proposal [4] that I will summarize here: 1) Guideline three is about configuration and global settings. 2) Guideline four is about element-level control. The adopted proposal argued that element-level control after a global "off" setting was unnecessary since the user had the necessary control per Guideline 4. However, at the previous teleconference, the Working group asserted otherwise. 2) SUMMARY OF DISCUSSION Our discussions have brought to light several ideas that were not addressed in the previous proposal: 2a) When there is a configuration not to render some author-supplied content, the user must be informed that this content is available but not rendered. 2b) Typically, the way that user agents indicate the absence of author-supplied content is with placeholders. 2c) These placeholders must be accessible. 2d) Element-level control is indeed required after a global configuration not to render some content type. One reason for this (forwarded by Denis Anson) is that N pieces of content rendered together may not be accessible, but each one may be accessible when retrieved individually. 2e) Automatic user agent behavior (in this case rendering content) may not be accessible and there needs to be a requirement to allow the user to control the behavior manually. We already have such requirements for form submission, page refreshes, focus changes, etc. It is natural to extend this reasoning to rendering: some content rendered automatically may be inaccessible, and and the Working Group has asked for a requirement that the user be able to access it on demand only. 3) PROPOSALS FOR GUIDELINE THREE Note: Checkpoints 4.5 and 4.6 combine audio, video, and animations. For consistency, I will combine some checkpoints of Guideline 3 similarly. There are no proposed changes to checkpoints 3.4, 3.7, and 3.8. 3a) Add a technique for all configuration checkpoints not to render some content that the user agent may choose not to download this content at all. This technique already appears in some of the current checkpoints. 3b) Background images (checkpoint 3.1): New: Allow the user to configure the user agent not to render background images. Allow configuration to notify the user when a background image is present but not rendered. Note: When background images are not rendered, user agents should render a solid background color. This checkpoint only requires control of background for "two-layered renderings", i.e., one rendered background (other than a solid color) with all other content rendered "above it". Comments: - Delete the following note since already in the guideline prose: "Background images may make it difficult or impossible to read superimposed text." 3c) Guideline 3 checkpoints about configuration of audio, video, and animated images (old checkpoints 3.2, 3.3, and 3.5) New: Allow the user to configure the user agent not to render audio, video, or animated images except on explicit request from the user. Allow a second configuration so that when this content is not rendered, the user agent renders a substitute placeholder in context. When placeholders are rendered, allow the user to activate each placeholder individually and replace it with the original author-supplied content. Note: This checkpoint applies to content rendered without any user interaction (including content rendered on load or as the result of a script) as well as content rendered as the result of user interaction that is not an explicit request (e.g., when the user activates a link). Activation of a placeholder is considered an explicit user request to render the original content. Refer also to checkpoints in Guideline 4 about control of audio, video, and animation. Comments: - Move the following note to the guideline prose: "Audio may interfere with other sources of sound such as the output of a speech synthesizer." 3d) Guideline 3 checkpoint about configuration of images (checkpoint 3.9). New: Same as previous checkpoint (3c) except that it's only about images and it's a priority 2 checkpoint. 3e) Guideline 3 checkpoint about configuration for scripts and applets (checkpoint 3.6). New: Allow the user to configure the user agent not to execute scripts or applets. Allow configuration to notify the user when scripts or applets are present but not executed. Note: This is particularly important for scripts that cause the screen to flicker, since people with photosensitive epilepsy can have seizures triggered by flickering or flashing, particularly in the 4 to 59 flashes per second (Hertz) range. Comment: - I'd also like to move the note after the checkpoint to the guideline prose or the techniques document. 3f) Allow the user to configure the user agent to render blinking images as motionless images. Comment: - Addition control of blinking is not required. Therefore, it is sufficient to stop the blinking and render a motionless image instead. 4) PROPOSALS FOR GUIDELINE FOUR Refer also to the previous proposal [5] for changes to checkpoints in Guideline 4. 4a) Allow the user to stop, pause, resume, fast advance, and fast reverse individual sources of audio, video, and animations that last three or more seconds at their default playback rate and that are not identified by the author as style. The user must be able to control each source recognized as distinct independently of others. [Priority 1]. Note: This checkpoint applies to content that is rendered automatically or on request from the user. Respect synchronization cues per checkpoint 2.4. The user agent may satisfy this checkpoint by allowing control of all audio, video, and animations. 4b) Allow the user to slow the presentation rate of individual sources of audio, video and animations that are not identified by the author as style. [Priority 1] Note: The user agent may satisfy this checkpoint by allowing the user to slow all audio, video, and animations. 4c) Allow the user to stop, pause, resume, fast advance, and fast reverse individual sources of audio, video, and animations not covered by checkpoint 4a [Priority 2]. 4d) Allow the user to slow the presentation rate of individual sources of audio, video, and animations not covered by checkpoint 4b [Priority 2]. 5) PROPOSAL FOR NEW CHECKPOINT ABOUT ACCESSIBLE GENERATED CONTENT In the 1 September Guidelines, checkpoint 2.7 (natural language) and checkpoint 2.5 (missing text equivalents) require the user agent to generate replacement content. The checkpoints above also include a requirement to generate placeholders (on configuration). I believe that the Working Group has, up to now, assumed that any content generated by the user agent in the following circumstances must be accessible. I propose to make this assumption explicit in the following checkpoint: <NEW> Ensure that any content (i.e., any part of the document object) generated by the user agent conforms to the Web Content Accessibility Guidelines 1.0 [WCAG10]. This checkpoint is Priority 1 for generated content that conforms Level A, Priority 2 for generated content that conforms at Level Double-A, and Priority 2 for generated content that conforms at Level Triple-A. Note: For example, if an image is used as a place holder, ensure that the image has a text equivalent per checkpoint 1.1 of WCAG 1.0. Generated content includes content that results from the repair of author-supplied content (e.g., as required by checkpoint 2.5), from a user configuration (e.g., refer to checkpoint 2.7 and checkpoints in Guideline 3). </NEW> Comments: - Checkpoint 1.3 of the ATAG 1.0 [6] reads: "Ensure that when the tool automatically generates markup it conforms to the W3C's Web Content Accessibility Guidelines 1.0 [WCAG10]." This ATAG checkpoint has a relative priority. Thank you, - Ian [1] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0362.html [2] http://www.w3.org/WAI/UA/WD-UAAG10-20000901/ [3] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0179.html [4] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0022.html [5] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000JulSep/0343.html [6] http://www.w3.org/TR/2000/REC-ATAG10-20000203/ -- Ian Jacobs (jacobs@w3.org) http://www.w3.org/People/Jacobs Tel: +1 831 457-2842 Cell: +1 917 450-8783
Received on Sunday, 10 September 2000 20:01:59 UTC