style: Parse the legacy bgcolor attribute per the HTML5 specification.

Additionally, this patch cleans up some miscellaneous formatting issues.

components/util/Cargo.toml

@@ -7,6 +7,9 @@ authors = ["The Servo Project Developers"]
 name = "util"
 path = "lib.rs"
 
+[dependencies.cssparser]
+git = "https://github.com/servo/rust-cssparser"
+
 [dependencies.geom]
 git = "https://github.com/servo/rust-geom"
 

components/util/lib.rs

@@ -13,6 +13,7 @@ extern crate log;
 
 extern crate alloc;
 extern crate collections;
+extern crate cssparser;
 extern crate geom;
 extern crate getopts;
 extern crate layers;

components/util/str.rs

@@ -4,6 +4,8 @@
 
 use geometry::Au;
 
+use cssparser::{mod, RGBAColor};
+use std::ascii::AsciiExt;
 use std::from_str::FromStr;
 use std::iter::Filter;
 use std::str::{CharEq, CharSplits};
@@ -184,6 +186,137 @@ pub fn parse_length(mut value: &str) -> LengthOrPercentageOrAuto {
     }
 }
 
+/// A "simple color" per HTML5 § 2.4.6.
+#[deriving(Show)]
+pub struct SimpleColor {
+    /// The red component of the color, [0, 255].
+    pub red: u8,
+    /// The green component of the color, [0, 255].
+    pub green: u8,
+    /// The blue component of the color, [0, 255].
+    pub blue: u8,
+}
+
+/// Parses a legacy color per HTML5 § 2.4.6. If unparseable, `Err` is returned.
+pub fn parse_legacy_color(mut input: &str) -> Result<SimpleColor,()> {
+    // Steps 1 and 2.
+    if input.len() == 0 {
+        return Err(())
+    }
+
+    // Step 3.
+    input = input.trim_left_chars(Whitespace).trim_right_chars(Whitespace);
+
+    // Step 4.
+    if input.eq_ignore_ascii_case("transparent") {
+        return Err(())
+    }
+
+    // Step 5.
+    match cssparser::parse_color_keyword(input) {
+        Ok(RGBAColor(rgba)) => {
+            return Ok(SimpleColor {
+                red: (rgba.red * 255.0) as u8,
+                green: (rgba.green * 255.0) as u8,
+                blue: (rgba.blue * 255.0) as u8,
+            })
+        }
+        _ => {}
+    }
+
+    // Step 6.
+    if input.len() == 4 {
+        match (input.char_at(0),
+               hex(input.char_at(1)),
+               hex(input.char_at(2)),
+               hex(input.char_at(3))) {
+            ('#', Ok(r), Ok(g), Ok(b)) => {
+                return Ok(SimpleColor {
+                    red: r * 17,
+                    green: g * 17,
+                    blue: b * 17,
+                })
+            }
+            _ => {}
+        }
+    }
+
+    // Step 7.
+    let mut new_input = String::new();
+    for ch in input.chars() {
+        if ch as u32 > 0xffff {
+            new_input.push_str("00")
+        } else {
+            new_input.push(ch)
+        }
+    }
+    let mut input = new_input.as_slice();
+
+    // Step 8.
+    if input.len() > 128 {
+        input = input.slice_to(128)
+    }
+
+    // Step 9.
+    if input.char_at(0) == '#' {
+        input = input.slice_from(1)
+    }
+
+    // Step 10.
+    let mut new_input = Vec::new();
+    for ch in input.chars() {
+        if hex(ch).is_ok() {
+            new_input.push(ch as u8)
+        } else {
+            new_input.push(b'0')
+        }
+    }
+    let mut input = new_input;
+
+    // Step 11.
+    while input.len() == 0 || (input.len() % 3) != 0 {
+        input.push(b'0')
+    }
+
+    // Step 12.
+    let mut length = input.len() / 3;
+    let (mut red, mut green, mut blue) = (input.slice_to(length),
+                                          input.slice(length, length * 2),
+                                          input.slice_from(length * 2));
+
+    // Step 13.
+    if length > 8 {
+        red = red.slice_from(length - 8);
+        green = green.slice_from(length - 8);
+        blue = blue.slice_from(length - 8);
+        length = 8
+    }
+
+    // Step 14.
+    while length > 2 && red[0] == b'0' && green[0] == b'0' && blue[0] == b'0' {
+        red = red.slice_from(1);
+        green = green.slice_from(1);
+        blue = blue.slice_from(1);
+        length -= 1
+    }
+
+    // Steps 15-20.
+    return Ok(SimpleColor {
+        red: (hex(red[0] as char).unwrap() << 4) | hex(red[1] as char).unwrap(),
+        green: (hex(green[0] as char).unwrap() << 4) | hex(green[1] as char).unwrap(),
+        blue: (hex(blue[0] as char).unwrap() << 4) | hex(blue[1] as char).unwrap(),
+    });
+
+    fn hex(ch: char) -> Result<u8,()> {
+        match ch {
+            '0'...'9' => Ok((ch as u8) - b'0'),
+            'a'...'f' => Ok((ch as u8) - b'a' + 10),
+            'A'...'F' => Ok((ch as u8) - b'A' + 10),
+            _ => Err(()),
+        }
+    }
+}
+
 
 #[deriving(Clone, Eq, PartialEq, Hash, Show)]
 pub struct LowercaseString {