[mediaqueries-5] Retire the 'light-level' media feature

Closes #5359
Closes #1727

Author: frivoal

mediaqueries-5/Overview.bs

@@ -2272,88 +2272,6 @@ Video Display Resolution: the 'video-resolution' feature
 
 Environment Media Features
 
-
-Detecting the ambient light level: the 'light-level' feature
-
-	
-	Name: light-level
-	Value: dim | normal | washed
-	For: @media
-	Type: discrete
-	
-
-	The 'light-level' media feature is used to query about the ambient light-level in which the device is used,
-	to allow the author to adjust style of the document in response.
-	The following values are valid:
-
-	
-		dim
-		
-			The device is used in a dim environment,
-			where excessive contrast and brightness would be distracting or uncomfortable to the reader.
-			For example: night time, or a dimly illuminated indoor environment.
-
-		normal
-		
-			The device is used in a environment with a light level in the ideal range for the screen,
-			and which does not necessitate any particular adjustment.
-
-		washed
-		
-			The device is used in an exceptionally bright environment,
-			causing the screen to be washed out and difficult to read.
-			For example: bright daylight.
-	
-
-	User agents should set the thresholds between the three levels
-	in a way that takes into account the characteristics of the device.
-
-
-		Even though it is expected that User Agents will adjust the value of this media feature
-		based on ambient light sensors,
-		this specification intentionally refrains from defining the three levels in terms of a measurement in lux,
-		for several reasons:
-
-		
-			
-				Devices equipped with a light sensor usually adjust the brightness of the screen automatically.
-				Depending on the level of adjustment,
-				the thresholds for needing a low contrast or high contrast content may vary.
-
-			
-				Different screen technologies wash out at very different ambient light levels;
-				e-ink displays remain readable in bright daylight,
-				while liquid crystal displays do not.
-
-			
-				Many embedded light sensors are inaccurately calibrated,
-				making it difficult to establish useful thresholds valid across devices.
-		
-	
-
-	For accessibility purposes, user agents may offer manual controls
-	allowing the user to switch between the three levels of independently of the ambient light level,
-	as high contrast or low contrast styles may be more suitable for users with visual disabilities.
-
-	
-		Using this media feature for accessibility purposes overlaps a lot with the high-contrast media feature proposed by Microsoft.
-		Can we adjust this so that it covers all use cases for both,
-		or somehow modify them to work in an orthogonal, rather than overlapping, fashion?
-
-
-		
-		@media (light-level: normal) {
-			p { background: url("texture.jpg"); color: #333 }
-		}
-		@media (light-level: dim) {
-			p { background: #222; color: #ccc }
-		}
-		@media (light-level: washed) {
-			p { background: white; color: black; font-size: 2em; }
-		}
-		
-	
-
 
 Detecting the display technology: the 'environment-blending' feature
 
@@ -2959,6 +2877,51 @@ Detecting the desire for reduced data usage when loading a page: the 'prefers-re
 		
 	
 
+
+Automatic handling of User Preferences
+
+	User agents may have explicit settings allowing users to indicate their preferences
+	or may make the determination based on settings in the underlying operating system.
+	User agents may also automatically infer the preferences of the user
+	based on knowledge about the device, the environment, etc.
+	In such case, it is recommended that they also offer a way for users to opt out of
+	or override the automatically determined preferences.
+
+
+		In addition to allowing users to explicitly choose
+		between a preference for a ''prefers-color-scheme/light'' or ''prefers-color-scheme/dark'' color scheme,
+		a user agent could have a mode where the determination is automatically made based on the current time,
+		expressing a preference for ''prefers-color-scheme/dark'' between sunset and dawn.
+	
+
+
+		Depending on the type of display used,
+		changes in the ambient light level may make the reading experience difficult or uncomfortable.
+
+		For instance, liquid crystal displays can be washed out and very hard to read
+		in brightly lit environments.
+		A device with such a screen and with an ambient light sensor
+		could automatically switch 'prefers-contrast' to ''prefers-contrast/high''
+		when it detects conditions that would make the screen difficult to read.
+		A user agent on a device with an e-ink display
+		would not make the same adjustment,
+		as such displays remain readable in bright daylight.
+
+		In the opposite situation,
+		user agents running of device with a light-emitting screen (LCD, OLED, etc.)
+		and an ambient light sensor
+		could automatically switch 'prefers-contrast' to ''prefers-contrast/low''
+		and 'prefers-color-scheme' to ''prefers-color-scheme/dark''
+		when used in a dim environment
+		where excessive contrast and brightness would be distracting or uncomfortable to the reader.
+	
+
+
+		A user agent could automatically switch between ''prefers-reduced-data: no-preference'' and ''prefers-reduced-data/reduce''
+		depending on whether the network connection in use
+		allows for unlimited data or is on a metered plan.
+	
+
  commit commentsComments0 (0)  {"resolvedServerColorMode":"day"}





  



    
  

  

          
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