style: Handle keywords for color values.

Bug: 1434130
Reviewed-by: emilio
MozReview-Commit-ID: 5GvIHSeQuCX

components/style/values/specified/color.rs

@@ -14,7 +14,7 @@ use parser::{Parse, ParserContext};
 use properties::longhands::system_colors::SystemColor;
 use std::fmt::{self, Write};
 use std::io::Write as IoWrite;
-use style_traits::{CssType, CssWriter, ParseError, StyleParseErrorKind};
+use style_traits::{CssType, CssWriter, KeywordsCollectFn, ParseError, StyleParseErrorKind};
 use style_traits::{SpecifiedValueInfo, ToCss, ValueParseErrorKind};
 use super::AllowQuirks;
 use values::computed::{Color as ComputedColor, Context, ToComputedValue};
@@ -429,6 +429,15 @@ impl From<Color> for RGBAColor {
 
 impl SpecifiedValueInfo for Color {
     const SUPPORTED_TYPES: u8 = CssType::COLOR;
+
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        // We are not going to insert all the color names here. Caller and
+        // devtools should take care of them. XXX Actually, transparent
+        // should probably be handled that way as well.
+        // XXX `currentColor` should really be `currentcolor`. But let's
+        // keep it consistent with the old system for now.
+        f(&["rgb", "rgba", "hsl", "hsla", "currentColor", "transparent"]);
+    }
 }
 
 /// Specified value for the "color" property, which resolves the `currentcolor`

ports/geckolib/glue.rs

@@ -1012,9 +1012,18 @@ pub unsafe extern "C" fn Servo_Property_GetCSSValuesForProperty(
     let mut values = BTreeSet::<&'static str>::new();
     prop_id.collect_property_completion_keywords(&mut |list| values.extend(list.iter()));
 
+    let mut extras = vec![];
+    if values.contains("transparent") {
+        // This is a special value devtools use to avoid inserting the
+        // long list of color keywords. We need to prepend it to values.
+        extras.push("COLOR");
+    }
+
     let result = result.as_mut().unwrap();
-    bindings::Gecko_ResizeTArrayForStrings(result, values.len() as u32);
-    for (src, dest) in values.iter().zip(result.iter_mut()) {
+    let len = extras.len() + values.len();
+    bindings::Gecko_ResizeTArrayForStrings(result, len as u32);
+
+    for (src, dest) in extras.iter().chain(values.iter()).zip(result.iter_mut()) {
         dest.write_str(src).unwrap();
     }
 }