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Merged
merged 1 commit into from
Nov 26, 2021
Merged

Share more code between hsl and hwb parsing. #293

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58 changes: 13 additions & 45 deletions src/color.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -564,8 +564,8 @@ where
{
let (red, green, blue, uses_commas) = match_ignore_ascii_case! { name,
"rgb" | "rgba" => parse_rgb_components_rgb(component_parser, arguments)?,
"hsl" | "hsla" => parse_rgb_components_hsl(component_parser, arguments)?,
"hwb" => parse_rgb_components_hwb(component_parser, arguments)?,
"hsl" | "hsla" => parse_hsl_hwb(component_parser, arguments, hsl_to_rgb)?,
"hwb" => parse_hsl_hwb(component_parser, arguments, hwb_to_rgb)?,
_ => return Err(arguments.new_unexpected_token_error(Token::Ident(name.to_owned().into()))),
};

Expand Down Expand Up @@ -624,10 +624,15 @@ where
Ok((red, green, blue, uses_commas))
}

/// Parses hsl and hbw syntax, which happens to be identical.
///
/// https://drafts.csswg.org/css-color/#the-hsl-notation
/// https://drafts.csswg.org/css-color/#the-hbw-notation
#[inline]
fn parse_rgb_components_hsl<'i, 't, ComponentParser>(
fn parse_hsl_hwb<'i, 't, ComponentParser>(
component_parser: &ComponentParser,
arguments: &mut Parser<'i, 't>,
to_rgb: impl FnOnce(f32, f32, f32) -> (f32, f32, f32),
) -> Result<(u8, u8, u8, bool), ParseError<'i, ComponentParser::Error>>
where
ComponentParser: ColorComponentParser<'i>,
Expand All @@ -641,54 +646,17 @@ where
let hue = hue_normalized_degrees / 360.;

// Saturation and lightness are clamped to 0% ... 100%
// https://drafts.csswg.org/css-color/#the-hsl-notation
let uses_commas = arguments.try_parse(|i| i.expect_comma()).is_ok();

let saturation = component_parser.parse_percentage(arguments)?;
let saturation = saturation.max(0.).min(1.);
let first_percentage = component_parser.parse_percentage(arguments)?.max(0.).min(1.);

if uses_commas {
arguments.expect_comma()?;
}

let lightness = component_parser.parse_percentage(arguments)?;
let lightness = lightness.max(0.).min(1.);

let (red, green, blue) = hsl_to_rgb(hue, saturation, lightness);
let red = clamp_unit_f32(red);
let green = clamp_unit_f32(green);
let blue = clamp_unit_f32(blue);
Ok((red, green, blue, uses_commas))
}

#[inline]
fn parse_rgb_components_hwb<'i, 't, ComponentParser>(
component_parser: &ComponentParser,
arguments: &mut Parser<'i, 't>,
) -> Result<(u8, u8, u8, bool), ParseError<'i, ComponentParser::Error>>
where
ComponentParser: ColorComponentParser<'i>,
{
let hue_degrees = component_parser.parse_angle_or_number(arguments)?.degrees();

// Subtract an integer before rounding, to avoid some rounding errors:
let hue_normalized_degrees = hue_degrees - 360. * (hue_degrees / 360.).floor();
let hue = hue_normalized_degrees / 360.;

let uses_commas = arguments.try_parse(|i| i.expect_comma()).is_ok();

let whiteness = component_parser.parse_percentage(arguments)?;
let whiteness = whiteness.max(0.).min(1.);

if uses_commas {
arguments.expect_comma()?;
}

let blackness = component_parser.parse_percentage(arguments)?;
let blackness = blackness.max(0.).min(1.);

let (red, green, blue) = hwb_to_rgb(hue, whiteness, blackness);
let second_percentage = component_parser.parse_percentage(arguments)?.max(0.).min(1.);

let (red, green, blue) = to_rgb(hue, first_percentage, second_percentage);
let red = clamp_unit_f32(red);
let green = clamp_unit_f32(green);
let blue = clamp_unit_f32(blue);
Expand All @@ -711,10 +679,10 @@ fn hwb_to_rgb(h: f32, w: f32, b: f32) -> (f32, f32, f32) {
(red, green, blue)
}

/// https://drafts.csswg.org/css-color/#hsl-color
/// except with h pre-multiplied by 3, to avoid some rounding errors.
#[inline]
fn hsl_to_rgb(hue: f32, saturation: f32, lightness: f32) -> (f32, f32, f32) {
// https://drafts.csswg.org/css-color/#hsl-color
// except with h pre-multiplied by 3, to avoid some rounding errors.
fn hue_to_rgb(m1: f32, m2: f32, mut h3: f32) -> f32 {
if h3 < 0. {
h3 += 3.
Expand Down