Bug 1751217 Part 4: Make macOS declare video-dynamic-range: high with new-enough OS. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D141056

layout/style/nsMediaFeatures.cpp

@@ -292,11 +292,30 @@ StylePrefersContrast Gecko_MediaFeatures_PrefersContrast(
 }
 
 StyleDynamicRange Gecko_MediaFeatures_DynamicRange(const Document* aDocument) {
+  // Bug 1759772: Once HDR color is available, update each platform
+  // LookAndFeel implementation to return StyleDynamicRange::High when
+  // appropriate.
   return StyleDynamicRange::Standard;
 }
 
 StyleDynamicRange Gecko_MediaFeatures_VideoDynamicRange(
     const Document* aDocument) {
+  if (nsContentUtils::ShouldResistFingerprinting(aDocument)) {
+    return StyleDynamicRange::Standard;
+  }
+  // video-dynamic-range: high has 3 requirements:
+  // 1) high peak brightness
+  // 2) high contrast ratio
+  // 3) color depth > 24
+  // We check the color depth requirement before asking the LookAndFeel
+  // if it is HDR capable.
+  if (nsDeviceContext* dx = GetDeviceContextFor(aDocument)) {
+    if (dx->GetDepth() > 24 &&
+        LookAndFeel::GetInt(LookAndFeel::IntID::VideoDynamicRange)) {
+      return StyleDynamicRange::High;
+    }
+  }
+
   return StyleDynamicRange::Standard;
 }
 

widget/LookAndFeel.h

@@ -324,6 +324,15 @@ class LookAndFeel {
     /** GTK menu radius */
     GtkMenuRadius,
 
+    /**
+     * Corresponding to dynamic-range.
+     * https://drafts.csswg.org/mediaqueries-5/#dynamic-range
+     * 0: Standard
+     * 1: High
+     */
+    DynamicRange,
+    VideoDynamicRange,
+
     /*
      * Not an ID; used to define the range of valid IDs.  Must be last.
      */

widget/cocoa/nsLookAndFeel.mm

@@ -499,6 +499,8 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
     case IntID::UseAccessibilityTheme:
       aResult = NSWorkspace.sharedWorkspace.accessibilityDisplayShouldIncreaseContrast;
       break;
+    case IntID::VideoDynamicRange:
+      aResult = nsCocoaFeatures::OnHighSierraOrLater();
       break;
     default:
       aResult = 0;

widget/nsXPLookAndFeel.cpp

@@ -109,7 +109,7 @@ static EnumeratedCache<FontID, widget::LookAndFeelFont, FontID::End> sFontCache;
 //
 // This needs to be of the same length and in the same order as
 // LookAndFeel::IntID values.
-static const char sIntPrefs[][43] = {
+static const char sIntPrefs[][45] = {
     "ui.caretBlinkTime",
     "ui.caretBlinkCount",
     "ui.caretWidth",
@@ -176,6 +176,8 @@ static const char sIntPrefs[][43] = {
     "ui.touchDeviceSupportPresent",
     "ui.titlebarRadius",
     "ui.GtkMenuRadius",
+    "ui.dynamicRange",
+    "ui.videoDynamicRange",
 };
 
 static_assert(ArrayLength(sIntPrefs) == size_t(LookAndFeel::IntID::End),