Bug 1643656 - Remove prefers-color-scheme: no-preference. r=gl,remote-protocol-reviewers,hiro,whimboo

It was removed from the spec.

Differential Revision: https://phabricator.services.mozilla.com/D78834

devtools/client/inspector/rules/constants.js

@@ -10,4 +10,4 @@
 exports.ELEMENT_STYLE = 100;
 
 // An array of the possible color schemes that can be emulated.
-exports.COLOR_SCHEMES = [null, "dark", "light", "no-preference"];
+exports.COLOR_SCHEMES = [null, "dark", "light"];

devtools/client/themes/rules.css

@@ -775,10 +775,6 @@
   fill: #bbb;
 }
 
-#color-scheme-simulation-toggle[state="no-preference"]::before {
-  fill-opacity: 0.5;
-}
-
 .flash-out {
   transition: background 1s;
 }

devtools/server/actors/emulation/content-viewer.js

@@ -83,10 +83,6 @@ const ContentViewerActor = protocol.ActorClassWithSpec(contentViewerSpec, {
       case "dark":
         internalColorScheme = Ci.nsIContentViewer.PREFERS_COLOR_SCHEME_DARK;
         break;
-      case "no-preference":
-        internalColorScheme =
-          Ci.nsIContentViewer.PREFERS_COLOR_SCHEME_NO_PREFERENCE;
-        break;
       default:
         internalColorScheme = Ci.nsIContentViewer.PREFERS_COLOR_SCHEME_NONE;
     }

docshell/base/nsIContentViewer.idl

@@ -328,7 +328,6 @@ interface nsIContentViewer : nsISupports
   cenum PrefersColorScheme : 8 {
     PREFERS_COLOR_SCHEME_LIGHT,
     PREFERS_COLOR_SCHEME_DARK,
-    PREFERS_COLOR_SCHEME_NO_PREFERENCE,
     PREFERS_COLOR_SCHEME_NONE, /* This clears the override. */
   };
 

dom/base/Document.cpp

@@ -16432,20 +16432,9 @@ StylePrefersColorScheme Document::PrefersColorScheme(
     }
   }
 
-  // If LookAndFeel::IntID::SystemUsesDarkTheme fails then return 2
-  // (no-preference)
-  switch (LookAndFeel::GetInt(LookAndFeel::IntID::SystemUsesDarkTheme, 2)) {
-    case 0:
-      return StylePrefersColorScheme::Light;
-    case 1:
-      return StylePrefersColorScheme::Dark;
-    case 2:
-      return StylePrefersColorScheme::NoPreference;
-    default:
-      // This only occurs if the user has set the ui.systemUsesDarkTheme pref to
-      // an invalid value.
-      return StylePrefersColorScheme::Light;
-  }
+  const bool dark =
+      !!LookAndFeel::GetInt(LookAndFeel::IntID::SystemUsesDarkTheme, 0);
+  return dark ? StylePrefersColorScheme::Dark : StylePrefersColorScheme::Light;
 }
 
 // static

layout/base/nsDocumentViewer.cpp

@@ -2743,8 +2743,6 @@ nsDocumentViewer::EmulatePrefersColorScheme(PrefersColorScheme aScheme) {
         return Some(StylePrefersColorScheme::Light);
       case PREFERS_COLOR_SCHEME_DARK:
         return Some(StylePrefersColorScheme::Dark);
-      case PREFERS_COLOR_SCHEME_NO_PREFERENCE:
-        return Some(StylePrefersColorScheme::NoPreference);
       case PREFERS_COLOR_SCHEME_NONE:
         return Nothing();
       default:

layout/base/tests/test_emulate_color_scheme.html

@@ -10,9 +10,6 @@
 @media (prefers-color-scheme: dark) {
   #test { color: rgb(0, 2, 0); }
 }
-@media (prefers-color-scheme: no-preference) {
-  #test { color: rgb(0, 3, 0); }
-}
 </style>
 <div id="test"></div>
 <script>
@@ -36,9 +33,6 @@ function colorId() {
   cv.emulatePrefersColorScheme(cv.PREFERS_COLOR_SCHEME_DARK);
   is(colorId(), 2, "Dark emulation works");
 
-  cv.emulatePrefersColorScheme(cv.PREFERS_COLOR_SCHEME_NO_PREFERENCE);
-  is(colorId(), 3, "No preference emulation works");
-
   cv.emulatePrefersColorScheme(cv.PREFERS_COLOR_SCHEME_NONE);
   is(colorId(), originalColor, "Clearing the override works");
 }

layout/reftests/css-mediaqueries/mq_prefers_color_scheme_dark.html

@@ -14,9 +14,6 @@ div {
 @media (prefers-color-scheme: light) {
   div { background-color: red; }
 }
-@media (prefers-color-scheme: no-preference) {
-  div { background-color: red; }
-}
 </style>
 <div></div>
 </html>

layout/reftests/css-mediaqueries/mq_prefers_color_scheme_light.html

@@ -14,9 +14,6 @@ div {
 @media (prefers-color-scheme: dark) {
   div { background-color: red; }
 }
-@media (prefers-color-scheme: no-preference) {
-  div { background-color: red; }
-}
 </style>
 <div></div>
 </html>

layout/reftests/css-mediaqueries/mq_prefers_color_scheme_no_preference.html

@@ -1,22 +0,0 @@
-<!doctype html>
-<meta charset="utf-8">
-<html>
-<title>prefers-color-scheme: no-preference</title>
-<style>
-div {
-  width: 100px;
-  height: 100px;
-}
-
-@media (prefers-color-scheme: no-preference) {
-  div { background-color: green; }
-}
-@media (prefers-color-scheme: light) {
-  div { background-color: red; }
-}
-@media (prefers-color-scheme: dark) {
-  div { background-color: red; }
-}
-</style>
-<div></div>
-</html>

layout/reftests/css-mediaqueries/mq_prefers_color_scheme_print.html

@@ -14,9 +14,6 @@ div {
 @media (prefers-color-scheme: dark) {
   div { background-color: red; }
 }
-@media (prefers-color-scheme: no-preference) {
-  div { background-color: red; }
-}
 </style>
 <div></div>
 </html>

layout/reftests/css-mediaqueries/reftest.list

@@ -32,4 +32,3 @@ test-pref(privacy.resistFingerprinting,true) == mq_prefers_color_scheme_light.ht
 == mq_prefers_color_scheme_print.html greenbox-print.html
 test-pref(ui.systemUsesDarkTheme,0) == mq_prefers_color_scheme_light.html greenbox.html
 test-pref(ui.systemUsesDarkTheme,1) == mq_prefers_color_scheme_dark.html greenbox.html
-test-pref(ui.systemUsesDarkTheme,2) == mq_prefers_color_scheme_no_preference.html greenbox.html

modules/libpref/init/StaticPrefList.yaml

@@ -5611,6 +5611,15 @@
   mirror: always
   rust: true
 
+# Whether the `no-preference` value for `prefers-color-scheme` is parsed.
+#
+# It never matches regardless.
+- name: layout.css.prefers-color-scheme-no-preference.enabled
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+  rust: true
+
 # Whether the `:focus-visible` pseudo-class is enabled.
 #
 # TODO: There are various ambiguities in the spec about this, so we shouldn't

remote/test/puppeteer/docs/api.md

@@ -1341,8 +1341,6 @@ await page.evaluate(() => matchMedia('(prefers-color-scheme: dark)').matches);
 // → true
 await page.evaluate(() => matchMedia('(prefers-color-scheme: light)').matches);
 // → false
-await page.evaluate(() => matchMedia('(prefers-color-scheme: no-preference)').matches);
-// → false
 
 await page.emulateMediaFeatures([{ name: 'prefers-reduced-motion', value: 'reduce' }]);
 await page.evaluate(() => matchMedia('(prefers-reduced-motion: reduce)').matches);
@@ -1358,8 +1356,6 @@ await page.evaluate(() => matchMedia('(prefers-color-scheme: dark)').matches);
 // → true
 await page.evaluate(() => matchMedia('(prefers-color-scheme: light)').matches);
 // → false
-await page.evaluate(() => matchMedia('(prefers-color-scheme: no-preference)').matches);
-// → false
 await page.evaluate(() => matchMedia('(prefers-reduced-motion: reduce)').matches);
 // → true
 await page.evaluate(() => matchMedia('(prefers-reduced-motion: no-preference)').matches);

remote/test/puppeteer/test/emulation.spec.js

@@ -246,11 +246,6 @@ describe('Emulation', () => {
           () => matchMedia('(prefers-color-scheme: dark)').matches
         )
       ).toBe(false);
-      expect(
-        await page.evaluate(
-          () => matchMedia('(prefers-color-scheme: no-preference)').matches
-        )
-      ).toBe(false);
       await page.emulateMediaFeatures([
         { name: 'prefers-color-scheme', value: 'dark' },
       ]);
@@ -264,11 +259,6 @@ describe('Emulation', () => {
           () => matchMedia('(prefers-color-scheme: light)').matches
         )
       ).toBe(false);
-      expect(
-        await page.evaluate(
-          () => matchMedia('(prefers-color-scheme: no-preference)').matches
-        )
-      ).toBe(false);
       await page.emulateMediaFeatures([
         { name: 'prefers-reduced-motion', value: 'reduce' },
         { name: 'prefers-color-scheme', value: 'light' },
@@ -293,11 +283,6 @@ describe('Emulation', () => {
           () => matchMedia('(prefers-color-scheme: dark)').matches
         )
       ).toBe(false);
-      expect(
-        await page.evaluate(
-          () => matchMedia('(prefers-color-scheme: no-preference)').matches
-        )
-      ).toBe(false);
     });
     it('should throw in case of bad argument', async () => {
       const { page } = getTestState();

servo/components/style/gecko/media_features.rs

@@ -278,6 +278,10 @@ enum PrefersReducedMotion {
     Reduce,
 }
 
+fn color_scheme_no_preference_enabled(_: &crate::parser::ParserContext) -> bool {
+    static_prefs::pref!("layout.css.prefers-color-scheme-no-preference.enabled")
+}
+
 /// Values for the prefers-color-scheme media feature.
 #[derive(Clone, Copy, Debug, FromPrimitive, Parse, PartialEq, ToCss)]
 #[repr(u8)]
@@ -285,6 +289,7 @@ enum PrefersReducedMotion {
 pub enum PrefersColorScheme {
     Light,
     Dark,
+    #[parse(condition = "color_scheme_no_preference_enabled")]
     NoPreference,
 }
 

testing/web-platform/meta/css/mediaqueries/prefers-color-scheme.html.ini

@@ -1,11 +0,0 @@
-[prefers-color-scheme.html]
-  [Should not be parseable in JS: '(prefers-color-scheme: no-preference)']
-    expected: FAIL
-
-  [Check that prefer-color-scheme evaluates to true in the boolean context]
-    expected:
-      if (os == "win") and (processor == "x86_64"): FAIL
-
-  [Should not be parseable in a CSS stylesheet: '(prefers-color-scheme: no-preference)']
-    expected: FAIL
-