style: CSS support for the font-palette property

This is just the CSS parsing, not yet connected to the rendering back-end.

Differential Revision: https://phabricator.services.mozilla.com/D157957

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

@@ -206,6 +206,18 @@ ${helpers.single_keyword_system(
     spec="https://www.w3.org/TR/css-fonts-4/#font-optical-sizing-def",
 )}
 
+${helpers.predefined_type(
+    "font-palette",
+    "FontPalette",
+    engines="gecko",
+    initial_value="computed::FontPalette::normal()",
+    initial_specified_value="specified::FontPalette::normal()",
+    animation_value_type="discrete",
+    gecko_pref="layout.css.font-palette.enabled",
+    has_effect_on_gecko_scrollbars=False,
+    spec="https://drafts.csswg.org/css-fonts/#font-palette-prop",
+)}
+
 ${helpers.predefined_type(
     "-x-lang",
     "XLang",

components/style/properties/shorthands/font.mako.rs

@@ -27,6 +27,7 @@
         ${'font-language-override' if engine == 'gecko' else ''}
         ${'font-feature-settings' if engine == 'gecko' else ''}
         ${'font-variation-settings' if engine == 'gecko' else ''}
+        ${'font-palette' if engine == 'gecko' else ''}
     "
     derive_value_info="False"
     spec="https://drafts.csswg.org/css-fonts-3/#propdef-font"
@@ -37,7 +38,7 @@
     use crate::properties::longhands::font_variant_caps;
     use crate::values::specified::text::LineHeight;
     use crate::values::specified::FontSize;
-    use crate::values::specified::font::{FontStretch, FontStretchKeyword};
+    use crate::values::specified::font::{FontPalette, FontStretch, FontStretchKeyword};
     #[cfg(feature = "gecko")]
     use crate::values::specified::font::SystemFont;
 
@@ -46,7 +47,8 @@
                                 variant_alternates variant_east_asian \
                                 variant_ligatures variant_numeric \
                                 variant_position feature_settings \
-                                variation_settings optical_sizing".split()
+                                variation_settings optical_sizing \
+                                palette".split()
     %>
     % if engine == "gecko":
         % for prop in gecko_sub_properties:
@@ -75,8 +77,9 @@
                              ${name}: ${name}::SpecifiedValue::system_font(sys),
                          % endif
                      % endfor
-                     // line-height is just reset to initial
+                     // line-height and palette are just reset to initial
                      line_height: LineHeight::normal(),
+                     font_palette: FontPalette::normal(),
                  })
             }
         % endif
@@ -186,9 +189,14 @@
                     return Ok(());
                 }
             }
+            if let Some(v) = self.font_palette {
+                if v != &font_palette::get_initial_specified_value() {
+                    return Ok(());
+                }
+            }
 
             % for name in gecko_sub_properties:
-            % if name != "optical_sizing" and name != "variation_settings":
+            % if name != "optical_sizing" and name != "variation_settings" and name != "palette":
             if self.font_${name} != &font_${name}::get_initial_specified_value() {
                 return Ok(());
             }
@@ -251,7 +259,7 @@
             let mut all = true;
 
             % for prop in SYSTEM_FONT_LONGHANDS:
-            % if prop == "font_optical_sizing" or prop == "font_variation_settings":
+            % if prop == "font_optical_sizing" or prop == "font_variation_settings" or prop == "font_palette":
             if let Some(value) = self.${prop} {
             % else:
             {

components/style/values/computed/font.rs

@@ -24,6 +24,7 @@ use std::fmt::{self, Write};
 use style_traits::{CssWriter, ParseError, ToCss};
 
 pub use crate::values::computed::Length as MozScriptMinSize;
+pub use crate::values::specified::font::FontPalette;
 pub use crate::values::specified::font::{FontSynthesis, MozScriptSizeMultiplier};
 pub use crate::values::specified::font::{XLang, XTextZoom};
 pub use crate::values::specified::Integer as SpecifiedInteger;

components/style/values/computed/mod.rs

@@ -63,7 +63,7 @@ pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset, C
 pub use self::easing::TimingFunction;
 pub use self::effects::{BoxShadow, Filter, SimpleShadow};
 pub use self::flex::FlexBasis;
-pub use self::font::{FontFamily, FontLanguageOverride, FontStyle};
+pub use self::font::{FontFamily, FontLanguageOverride, FontStyle, FontPalette};
 pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumeric};
 pub use self::font::{FontSize, FontSizeAdjust, FontStretch, FontSynthesis};
 pub use self::font::{FontVariantAlternates, FontWeight};

components/style/values/specified/font.rs

@@ -20,7 +20,7 @@ use crate::values::generics::NonNegative;
 use crate::values::specified::length::{FontBaseSize, PX_PER_PT};
 use crate::values::specified::{AllowQuirks, Angle, Integer, LengthPercentage};
 use crate::values::specified::{NoCalcLength, NonNegativeNumber, NonNegativePercentage, Number};
-use crate::values::CustomIdent;
+use crate::values::{CustomIdent, SelectorParseErrorKind, serialize_atom_identifier};
 use crate::Atom;
 use cssparser::{Parser, Token};
 #[cfg(feature = "gecko")]
@@ -743,7 +743,7 @@ impl Parse for FontSizeAdjust {
                 "ic-height" if basis_enabled => GenericFontSizeAdjust::IcHeight,
                 // Unknown (or disabled) keyword.
                 _ => return Err(location.new_custom_error(
-                    ::selectors::parser::SelectorParseErrorKind::UnexpectedIdent(ident)
+                    SelectorParseErrorKind::UnexpectedIdent(ident)
                 )),
             };
             let value = NonNegativeNumber::parse(context, input)?;
@@ -1991,7 +1991,6 @@ impl Parse for FontSynthesis {
         _: &ParserContext,
         input: &mut Parser<'i, 't>,
     ) -> Result<FontSynthesis, ParseError<'i>> {
-        use crate::values::SelectorParseErrorKind;
         let mut result = Self::none();
         while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
             match_ignore_ascii_case! { &ident,
@@ -2162,6 +2161,59 @@ impl Parse for FontLanguageOverride {
     }
 }
 
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// Allows authors to choose a palette from those supported by a color font
+/// (and potentially @font-palette-values overrides).
+pub struct FontPalette(Atom);
+
+#[allow(missing_docs)]
+impl FontPalette {
+    pub fn normal() -> Self { Self(atom!("normal")) }
+    pub fn light() -> Self { Self(atom!("light")) }
+    pub fn dark() -> Self { Self(atom!("dark")) }
+}
+
+impl Parse for FontPalette {
+    /// normal | light | dark | dashed-ident
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontPalette, ParseError<'i>> {
+        let location = input.current_source_location();
+        let ident = input.expect_ident()?;
+        match_ignore_ascii_case! { &ident,
+            "normal" => Ok(Self::normal()),
+            "light" => Ok(Self::light()),
+            "dark" => Ok(Self::dark()),
+            _ => if ident.starts_with("--") {
+                Ok(Self(Atom::from(ident.as_ref())))
+            } else {
+                Err(location.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())))
+            },
+        }
+    }
+}
+
+impl ToCss for FontPalette {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        serialize_atom_identifier(&self.0, dest)
+    }
+}
+
 /// This property provides low-level control over OpenType or TrueType font
 /// variations.
 pub type SpecifiedFontVariationSettings = FontSettings<VariationValue<Number>>;

components/style/values/specified/mod.rs

@@ -51,7 +51,7 @@ pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset, C
 pub use self::easing::TimingFunction;
 pub use self::effects::{BoxShadow, Filter, SimpleShadow};
 pub use self::flex::FlexBasis;
-pub use self::font::{FontFamily, FontLanguageOverride, FontStyle};
+pub use self::font::{FontFamily, FontLanguageOverride, FontStyle, FontPalette};
 pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumeric};
 pub use self::font::{FontSize, FontSizeAdjust, FontSizeKeyword, FontStretch, FontSynthesis};
 pub use self::font::{FontVariantAlternates, FontWeight};