Auto merge of #84 - servo:clamp_, r=SimonSapin

Clamp rgb values to [0,1]

#83 plus a code comment linking to discussion.

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Author: bors-servo

src/color.rs

@@ -314,9 +314,13 @@ fn parse_color_function(name: &str, arguments: &mut Parser) -> Result<Color, ()>
         _ => return Err(())
     };
 
-    let red: f32;
-    let green: f32;
-    let blue: f32;
+    fn clamp(val: f32) -> f32 {
+        val.max(0.).min(1.)
+    }
+
+    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()) {
@@ -336,13 +340,23 @@ fn parse_color_function(name: &str, arguments: &mut Parser) -> Result<Color, ()>
             }
             _ => 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 = (try!(arguments.expect_percentage())).max(0.).min(1.);
+        let saturation = clamp(try!(arguments.expect_percentage()));
         try!(arguments.expect_comma());
-        let lightness = (try!(arguments.expect_percentage())).max(0.).min(1.);
+        let lightness = clamp(try!(arguments.expect_percentage()));
 
         // https://drafts.csswg.org/css-color/#hsl-color
         fn hue_to_rgb(m1: f32, m2: f32, mut h: f32) -> f32 {
@@ -364,7 +378,7 @@ fn parse_color_function(name: &str, arguments: &mut Parser) -> Result<Color, ()>
 
     let alpha = if has_alpha {
         try!(arguments.expect_comma());
-        (try!(arguments.expect_number())).max(0.).min(1.)
+        clamp(try!(arguments.expect_number()))
     } else {
         1.
     };

src/css-parsing-tests/color3.json

@@ -46,7 +46,7 @@
 "rgb(0,51,255)", [0, 0.2, 1, 1],
 "rgb(0\t,  51 ,255)", [0, 0.2, 1, 1],
 "rgb(/* R */0, /* G */51, /* B */255)", [0, 0.2, 1, 1],
-"rgb(-51, 306, 0)", [-0.2, 1.2, 0, 1],
+"rgb(-51, 306, 0)", [0, 1, 0, 1],
 
 "rgb(42%, 3%, 50%)", [0.42, 0.03, 0.5, 1],
 "RGB(100%, 100%, 100%)", [1, 1, 1, 1],
@@ -55,7 +55,7 @@
 "rgb(10%,20%,30%)", [0.1, 0.2, 0.3, 1],
 "rgb(10%\t,  20% ,30%)", [0.1, 0.2, 0.3, 1],
 "rgb(/* R */ 10%, /* G */ 20%, /* B */ 30%)", [0.1, 0.2, 0.3, 1],
-"rgb(-12%, 110%, 1400%)", [-0.12, 1.1, 14, 1],
+"rgb(-12%, 110%, 1400%)", [0, 1, 1, 1],
 
 "rgb(10%, 50%, 0)", null,
 "rgb(255, 50%, 0%)", null,