Media features use cases for personalization

This page collects use cases for media features used for personalization of web pages. These are supposed to justify a new set of media features as proposed by CSS media queries level 5. References:

Proposed media features

Feel free to extend the following table with use cases. For more detailed use cases, you may create new subpages.

Media feature	Values	Use case	Operating systems setting
captionsEnabled	true, false	A video player in a webpage would automatically play captions.	Most operating systems have a setting for this
audioDescriptionEnabled	true, false	A video player in a webpage would automatically enable audio descriptions. If the player does not support this, an alternative video (with Audio description) would be loaded.	-
signLanguageEnabled	true, false	An alternative video (in sign language) would be loaded.	-
signLanguage	language tag conforming to IETF BCP 47	A sign language video in the user's preferred language is chosen, if available.	-
pictogramsEnabled	true, false	A web page would would automatically add pictograms to support people with a reading disability or a general cognitive disability.	-
displaySkiplinks	always, onfocus, never	A skip-link would be automatically shown or suppressed.	-
tableOfContents	true, false	At the beginning of a page, a table of contents is shown as an additional means of navigation.	-
sessionTimeout	integer (seconds)	Determines how many seconds a user can remain inactive before a session times out. People with certain specific disabilities need longer session timeouts. This would serve a need in WCAG 2, SC 2.2.1 Timing Adjustable (A).	-
selfVoicingEnabled	true, false	Determines whether a Web application's self-voicing feature should be enabled.	-
(new media feature)	(values)	(use case)	(OS setting)
(new media feature)	(values)	(use case)	(OS setting)
(new media feature)	(values)	(use case)	(OS setting)

Other use cases that would replace the need for a user style sheet

The following proposed "parameters" would require that a web author can reference their values in their code (e.g. CSS) rather than just switching based on their values.

foregroundColor, backgroundColor (CSS color value). For many people, high contrast is not an optimal font change. Some people use color to minimize the impact of permanent floaters or scotomas (scars). Most users do not know how to create and enable a user style sheet in their browser.
fontSize (integer). Not uniform, different sizes for different usage. SC 1.4.10 is a partial fix, but it is very useful to enlarge different elements by different factors. 1.4.10 only enables one zoom. Word wrapping is always essential.
fontFamily. This is useful because different fonts have different critical print sizes. Sometimes if you cannot enlarge enough a font family shift will give you the edge you need.
viewportWidth. Many people have a limited visual field. Rather than zooming to 320px width, they required reducing the viewport width to 320px. So, reduced width with normal font size is used.
Layout. Users often need a new layout that does not look like the author's layout, but still keeps the reading order. This is a readjustment of visual layout similar to but not the same as the readjustment required for screen reader reading. Turning of positioning is very important. This has gotten a log harder with grids etc.