style: Add an internal -moz-system-color() function to expose both light and dark system colors

Differential Revision: https://phabricator.services.mozilla.com/D117416

components/style/values/specified/color.rs

@@ -131,6 +131,20 @@ impl ToCss for ColorMix {
     }
 }
 
+/// The color scheme for a specific system color.
+#[cfg(feature = "gecko")]
+#[derive(Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, ToCss, ToShmem)]
+#[repr(u8)]
+pub enum SystemColorScheme {
+    /// The default color-scheme for the document.
+    #[css(skip)]
+    Default,
+    /// A light color scheme.
+    Light,
+    /// A dark color scheme.
+    Dark,
+}
+
 /// Specified color value
 #[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
 pub enum Color {
@@ -145,9 +159,10 @@ pub enum Color {
     },
     /// A complex color value from computed value
     Complex(ComputedColor),
-    /// A system color
+    /// Either a system color, or a `-moz-system-color(<system-color>, light|dark)`
+    /// function which allows chrome code to choose between color schemes.
     #[cfg(feature = "gecko")]
-    System(SystemColor),
+    System(SystemColor, SystemColorScheme),
     /// A color mix.
     ColorMix(Box<ColorMix>),
     /// Quirksmode-only rule for inheriting color from the body
@@ -390,7 +405,7 @@ pub enum SystemColor {
 #[cfg(feature = "gecko")]
 impl SystemColor {
     #[inline]
-    fn compute(&self, cx: &Context) -> ComputedColor {
+    fn compute(&self, cx: &Context, scheme: SystemColorScheme) -> ComputedColor {
         use crate::gecko_bindings::bindings;
 
         let prefs = cx.device().pref_sheet_prefs();
@@ -403,7 +418,7 @@ impl SystemColor {
             SystemColor::Visitedtext => prefs.mVisitedLinkColor,
 
             _ => unsafe {
-                bindings::Gecko_GetLookAndFeelSystemColor(*self as i32, cx.device().document())
+                bindings::Gecko_GetLookAndFeelSystemColor(*self as i32, cx.device().document(), scheme)
             },
         })
     }
@@ -479,6 +494,20 @@ impl<'a, 'b: 'a, 'i: 'a> ::cssparser::ColorComponentParser<'i> for ColorComponen
     }
 }
 
+fn parse_moz_system_color<'i, 't>(
+    context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+) -> Result<(SystemColor, SystemColorScheme), ParseError<'i>> {
+    debug_assert!(context.chrome_rules_enabled());
+    input.expect_function_matching("-moz-system-color")?;
+    input.parse_nested_block(|input| {
+        let color = SystemColor::parse(context, input)?;
+        input.expect_comma()?;
+        let scheme = SystemColorScheme::parse(input)?;
+        Ok((color, scheme))
+    })
+}
+
 impl Parse for Color {
     fn parse<'i, 't>(
         context: &ParserContext,
@@ -504,7 +533,13 @@ impl Parse for Color {
                 #[cfg(feature = "gecko")]
                 {
                     if let Ok(system) = input.try_parse(|i| SystemColor::parse(context, i)) {
-                        return Ok(Color::System(system));
+                        return Ok(Color::System(system, SystemColorScheme::Default));
+                    }
+
+                    if context.chrome_rules_enabled() {
+                        if let Ok((color, scheme)) = input.try_parse(|i| parse_moz_system_color(context, i)) {
+                            return Ok(Color::System(color, scheme));
+                        }
                     }
                 }
 
@@ -543,7 +578,17 @@ impl ToCss for Color {
             Color::Complex(_) => Ok(()),
             Color::ColorMix(ref mix) => mix.to_css(dest),
             #[cfg(feature = "gecko")]
-            Color::System(system) => system.to_css(dest),
+            Color::System(system, scheme) => {
+                if scheme == SystemColorScheme::Default {
+                    system.to_css(dest)
+                } else {
+                    dest.write_str("-moz-system-color(")?;
+                    system.to_css(dest)?;
+                    dest.write_str(", ")?;
+                    scheme.to_css(dest)?;
+                    dest.write_char(')')
+                }
+            }
             #[cfg(feature = "gecko")]
             Color::InheritFromBodyQuirk => Ok(()),
         }
@@ -709,7 +754,7 @@ impl Color {
                 ))
             },
             #[cfg(feature = "gecko")]
-            Color::System(system) => system.compute(context?),
+            Color::System(system, scheme) => system.compute(context?, scheme),
             #[cfg(feature = "gecko")]
             Color::InheritFromBodyQuirk => ComputedColor::rgba(context?.device().body_text_color()),
         })