HTML5 and global accessibility settings

Hello! I've added the following to the wiki at http://www.w3.org/WAI/UA/work/wiki/HTML5_review_by_UAWG_notes#Global_accessibility_settings


    Global accessibility settings

*Issue:* Should the HTML5 spec define a standard, platform-independent way for content to query the user agent's accessibility settings, and by extension platform settings that are known to the user agent? Are there any equivalents today?

*Use case:* All major operating systems support a "high contrast" mode that tells software the user wants high contrast between foreground and background. Yev turns on this option, and in his browser he loads a web-based flow chart editor that displays all its document content in an HTML5 canvas element. The flow chart editor wants to detect when the user has high contrast mode turned on so it can adjust its graphical display appropriately. Because it's designed to run on any browser and any operating system, it needs a platform-independent means of querying this setting.

*Use case:* Kevin has turned on the "Show Extra Keyboard Help" option in the Windows Control Panel, which tells all software that he wants any and all options that enhance keyboard access to be automatically enabled. His web browser responds to this setting by, for example, always displaying the underlined access keys in menu and control labels. He would like web pages and web apps to also respond to this setting, even if they're creating custom controls.