style: Implement accent-color in nsNativeBasicTheme

This is a new addition for CSS UI Level 4:

  https://drafts.csswg.org/css-ui-4/#widget-accent

I want to provide feedback on some spec issues, and thought it was a
kinda neat thing to prototype (it also makes testing contrast and such
with random GTK themes easier).

For now enable for Nightly only.

Differential Revision: https://phabricator.services.mozilla.com/D112312

components/style/properties/longhands/inherited_ui.mako.rs

@@ -73,13 +73,26 @@ ${helpers.single_keyword(
 
 ${helpers.predefined_type(
     "caret-color",
+    "color::CaretColor",
+    "generics::color::CaretColor::auto()",
+    engines="gecko",
+    spec="https://drafts.csswg.org/css-ui/#caret-color",
+    animation_value_type="CaretColor",
+    boxed=True,
+    ignored_when_colors_disabled=True,
+)}
+
+${helpers.predefined_type(
+    "accent-color",
     "ColorOrAuto",
     "generics::color::ColorOrAuto::Auto",
     engines="gecko",
-    spec="https://drafts.csswg.org/css-ui/#caret-color",
-    animation_value_type="AnimatedCaretColor",
+    spec="https://drafts.csswg.org/css-ui-4/#widget-accent",
+    gecko_pref="layout.css.accent-color.enabled",
+    animation_value_type="ColorOrAuto",
     boxed=True,
     ignored_when_colors_disabled=True,
+    has_effect_on_gecko_scrollbars=False,
 )}
 
 ${helpers.predefined_type(

components/style/values/computed/color.rs

@@ -6,7 +6,7 @@
 
 use crate::values::animated::color::RGBA as AnimatedRGBA;
 use crate::values::animated::ToAnimatedValue;
-use crate::values::generics::color::{Color as GenericColor, ColorOrAuto as GenericColorOrAuto};
+use crate::values::generics::color::{GenericColor, GenericColorOrAuto, GenericCaretColor};
 use cssparser::{Color as CSSParserColor, RGBA};
 use std::fmt;
 use style_traits::{CssWriter, ToCss};
@@ -112,3 +112,6 @@ impl ToAnimatedValue for RGBA {
 
 /// auto | <color>
 pub type ColorOrAuto = GenericColorOrAuto<Color>;
+
+/// caret-color
+pub type CaretColor = GenericCaretColor<Color>;

components/style/values/generics/color.rs

@@ -96,6 +96,7 @@ impl<RGBA> From<RGBA> for Color<RGBA> {
     ToAnimatedValue,
     ToAnimatedZero,
     ToComputedValue,
+    ToResolvedValue,
     ToCss,
     ToShmem,
 )]
@@ -108,3 +109,32 @@ pub enum GenericColorOrAuto<C> {
 }
 
 pub use self::GenericColorOrAuto as ColorOrAuto;
+
+/// Caret color is effectively a ColorOrAuto, but resolves `auto` to
+/// currentColor.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericCaretColor<C>(pub GenericColorOrAuto<C>);
+
+impl<C> GenericCaretColor<C> {
+    /// Returns the `auto` value.
+    pub fn auto() -> Self {
+        GenericCaretColor(GenericColorOrAuto::Auto)
+    }
+}
+
+pub use self::GenericCaretColor as CaretColor;

components/style/values/resolved/color.rs

@@ -6,7 +6,7 @@
 
 use super::{Context, ToResolvedValue};
 
-use crate::values::computed;
+use crate::values::computed::color as computed;
 use crate::values::generics::color as generics;
 
 impl ToResolvedValue for computed::Color {
@@ -24,14 +24,14 @@ impl ToResolvedValue for computed::Color {
     }
 }
 
-impl ToResolvedValue for computed::ColorOrAuto {
+impl ToResolvedValue for computed::CaretColor {
     // A resolved caret-color value is an rgba color, with auto resolving to
     // currentcolor.
     type ResolvedValue = cssparser::RGBA;
 
     #[inline]
     fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
-        let color = match self {
+        let color = match self.0 {
             generics::ColorOrAuto::Color(color) => color,
             generics::ColorOrAuto::Auto => generics::Color::currentcolor(),
         };
@@ -40,6 +40,6 @@ impl ToResolvedValue for computed::ColorOrAuto {
 
     #[inline]
     fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
-        generics::ColorOrAuto::Color(computed::Color::from_resolved_value(resolved))
+        generics::CaretColor(generics::ColorOrAuto::Color(computed::Color::from_resolved_value(resolved)))
     }
 }

components/style/values/specified/color.rs

@@ -9,7 +9,7 @@ use super::AllowQuirks;
 use crate::gecko_bindings::structs::nscolor;
 use crate::parser::{Parse, ParserContext};
 use crate::values::computed::{Color as ComputedColor, Context, ToComputedValue};
-use crate::values::generics::color::ColorOrAuto as GenericColorOrAuto;
+use crate::values::generics::color::{GenericColorOrAuto, GenericCaretColor};
 use crate::values::specified::calc::CalcNode;
 use crate::values::specified::Percentage;
 use cssparser::{AngleOrNumber, Color as CSSParserColor, Parser, Token, RGBA};
@@ -808,3 +808,15 @@ impl Parse for ColorPropertyValue {
 
 /// auto | <color>
 pub type ColorOrAuto = GenericColorOrAuto<Color>;
+
+/// caret-color
+pub type CaretColor = GenericCaretColor<Color>;
+
+impl Parse for CaretColor {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        ColorOrAuto::parse(context, input).map(GenericCaretColor)
+    }
+}