Add a comment on clamping rgb() and rgba() colors.

src/color.rs

@@ -318,32 +318,41 @@ fn parse_color_function(name: &str, arguments: &mut Parser) -> Result<Color, ()>
         val.max(0.).min(1.)
     }
 
-    let red: f32;
-    let green: f32;
-    let blue: f32;
+    let mut red: f32;
+    let mut green: f32;
+    let mut blue: f32;
     if is_rgb {
         // Either integers or percentages, but all the same type.
         match try!(arguments.next()) {
             Token::Number(ref v) if v.int_value.is_some() => {
-
-                red = clamp(v.value / 255.);
+                red = v.value / 255.;
                 try!(arguments.expect_comma());
-                green = clamp(try!(arguments.expect_integer()) as f32 / 255.);
+                green = try!(arguments.expect_integer()) as f32 / 255.;
                 try!(arguments.expect_comma());
-                blue = clamp(try!(arguments.expect_integer()) as f32 / 255.);
+                blue = try!(arguments.expect_integer()) as f32 / 255.;
             }
             Token::Percentage(ref v) => {
-                red = clamp(v.unit_value);
+                red = v.unit_value;
                 try!(arguments.expect_comma());
-                green = clamp(try!(arguments.expect_percentage()));
+                green = try!(arguments.expect_percentage());
                 try!(arguments.expect_comma());
-                blue = clamp(try!(arguments.expect_percentage()));
+                blue = try!(arguments.expect_percentage());
             }
             _ => return Err(())
         };
+        // The spec says to clamp to the device gamut which may be wider than 0% ... 100%,
+        // but moz2d doesn’t seem to have any support for this, so let’s not bother.
+        // https://drafts.csswg.org/css-color/#rgb-functions
+        // https://github.com/servo/rust-cssparser/issues/76
+        red = clamp(red);
+        green = clamp(green);
+        blue = clamp(blue);
     } else {
         let hue = try!(arguments.expect_number()) / 360.;
         let hue = hue - hue.floor();
+        // Saturation and lightness are clamped to 0% ... 100%
+        // regardless of device gamut:
+        // https://drafts.csswg.org/css-color/#the-hsl-notation
         try!(arguments.expect_comma());
         let saturation = clamp(try!(arguments.expect_percentage()));
         try!(arguments.expect_comma());