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LibWeb+LibGfx: Move CSS sRGB color serialization function to LibGfx

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Tim Ledbetter 2025-10-26 16:48:02 +00:00 committed by Jelle Raaijmakers
parent 633fc45e0f
commit ebd802f6fc
8 changed files with 74 additions and 73 deletions
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67
Libraries/LibGfx/Color.cpp
View File

@ -25,6 +25,73 @@
namespace Gfx {
namespace {
char nth_digit(u32 value, u8 digit)
{
// This helper is used to format integers.
// nth_digit(745, 1) -> '5'
// nth_digit(745, 2) -> '4'
// nth_digit(745, 3) -> '7'
VERIFY(value < 1000);
VERIFY(digit <= 3);
VERIFY(digit > 0);
while (digit > 1) {
value /= 10;
digit--;
}
return '0' + value % 10;
}
Array<char, 4> format_to_8bit_compatible(u8 value)
{
// This function formats to the shortest string that roundtrips at 8 bits.
// As an example:
// 127 / 255 = 0.498 ± 0.001
// 128 / 255 = 0.502 ± 0.001
// But round(.5 * 255) == 128, so this function returns (note that it's only the fractional part):
// 127 -> "498"
// 128 -> "5"
u32 const three_digits = (value * 1000u + 127) / 255;
u32 const rounded_to_two_digits = (three_digits + 5) / 10 * 10;
if ((rounded_to_two_digits * 255 / 100 + 5) / 10 != value)
return { nth_digit(three_digits, 3), nth_digit(three_digits, 2), nth_digit(three_digits, 1), '\0' };
u32 const rounded_to_one_digit = (three_digits + 50) / 100 * 100;
if ((rounded_to_one_digit * 255 / 100 + 5) / 10 != value)
return { nth_digit(rounded_to_two_digits, 3), nth_digit(rounded_to_two_digits, 2), '\0', '\0' };
return { nth_digit(rounded_to_one_digit, 3), '\0', '\0', '\0' };
}
}
// https://www.w3.org/TR/css-color-4/#serializing-sRGB-values
void Color::serialize_a_srgb_value(StringBuilder& builder) const
{
// The serialized form is derived from the computed value and thus, uses either the rgb() or rgba() form
// (depending on whether the alpha is exactly 1, or not), with lowercase letters for the function name.
// NOTE: Since we use Gfx::Color, having an "alpha of 1" means its value is 255.
if (alpha() == 0)
builder.appendff("rgba({}, {}, {}, 0)", red(), green(), blue());
else if (alpha() == 255)
builder.appendff("rgb({}, {}, {})", red(), green(), blue());
else
builder.appendff("rgba({}, {}, {}, 0.{})", red(), green(), blue(), format_to_8bit_compatible(alpha()).data());
}
String Color::serialize_a_srgb_value() const
{
StringBuilder builder;
serialize_a_srgb_value(builder);
return builder.to_string_without_validation();
}
String Color::to_string(HTMLCompatibleSerialization html_compatible_serialization) const
{
// If the following conditions are all true:

3
Libraries/LibGfx/Color.h
View File

@ -502,6 +502,9 @@ public:
String to_string_without_alpha() const;
Utf16String to_utf16_string_without_alpha() const;
void serialize_a_srgb_value(StringBuilder&) const;
String serialize_a_srgb_value() const;
ByteString to_byte_string() const;
ByteString to_byte_string_without_alpha() const;
static Optional<Color> from_string(StringView);

67
Libraries/LibWeb/CSS/Serialize.cpp
View File

@ -127,66 +127,6 @@ void serialize_unicode_ranges(StringBuilder& builder, Vector<Gfx::UnicodeRange>
});
}
namespace {
char nth_digit(u32 value, u8 digit)
{
// This helper is used to format integers.
// nth_digit(745, 1) -> '5'
// nth_digit(745, 2) -> '4'
// nth_digit(745, 3) -> '7'
VERIFY(value < 1000);
VERIFY(digit <= 3);
VERIFY(digit > 0);
while (digit > 1) {
value /= 10;
digit--;
}
return '0' + value % 10;
}
Array<char, 4> format_to_8bit_compatible(u8 value)
{
// This function formats to the shortest string that roundtrips at 8 bits.
// As an example:
// 127 / 255 = 0.498 ± 0.001
// 128 / 255 = 0.502 ± 0.001
// But round(.5 * 255) == 128, so this function returns (note that it's only the fractional part):
// 127 -> "498"
// 128 -> "5"
u32 const three_digits = (value * 1000u + 127) / 255;
u32 const rounded_to_two_digits = (three_digits + 5) / 10 * 10;
if ((rounded_to_two_digits * 255 / 100 + 5) / 10 != value)
return { nth_digit(three_digits, 3), nth_digit(three_digits, 2), nth_digit(three_digits, 1), '\0' };
u32 const rounded_to_one_digit = (three_digits + 50) / 100 * 100;
if ((rounded_to_one_digit * 255 / 100 + 5) / 10 != value)
return { nth_digit(rounded_to_two_digits, 3), nth_digit(rounded_to_two_digits, 2), '\0', '\0' };
return { nth_digit(rounded_to_one_digit, 3), '\0', '\0', '\0' };
}
}
// https://www.w3.org/TR/css-color-4/#serializing-sRGB-values
void serialize_a_srgb_value(StringBuilder& builder, Color color)
{
// The serialized form is derived from the computed value and thus, uses either the rgb() or rgba() form
// (depending on whether the alpha is exactly 1, or not), with lowercase letters for the function name.
// NOTE: Since we use Gfx::Color, having an "alpha of 1" means its value is 255.
if (color.alpha() == 0)
builder.appendff("rgba({}, {}, {}, 0)", color.red(), color.green(), color.blue());
else if (color.alpha() == 255)
builder.appendff("rgb({}, {}, {})", color.red(), color.green(), color.blue());
else
builder.appendff("rgba({}, {}, {}, 0.{})", color.red(), color.green(), color.blue(), format_to_8bit_compatible(color.alpha()).data());
}
// https://drafts.csswg.org/cssom/#serialize-a-css-value
void serialize_a_number(StringBuilder& builder, double value)
{
@ -218,13 +158,6 @@ String serialize_a_url(StringView url)
return builder.to_string_without_validation();
}
String serialize_a_srgb_value(Color color)
{
StringBuilder builder;
serialize_a_srgb_value(builder, color);
return builder.to_string_without_validation();
}
String serialize_a_number(double value)
{
StringBuilder builder;

2
Libraries/LibWeb/CSS/Serialize.h
View File

@ -23,13 +23,11 @@ WEB_API void serialize_an_identifier(StringBuilder&, StringView ident);
void serialize_a_string(StringBuilder&, StringView string);
WEB_API void serialize_a_url(StringBuilder&, StringView url);
void serialize_unicode_ranges(StringBuilder&, Vector<Gfx::UnicodeRange> const& unicode_ranges);
void serialize_a_srgb_value(StringBuilder&, Color color);
void serialize_a_number(StringBuilder&, double value);
String serialize_an_identifier(StringView ident);
String serialize_a_string(StringView string);
String serialize_a_url(StringView url);
String serialize_a_srgb_value(Color color);
String serialize_a_number(double value);
// https://www.w3.org/TR/cssom/#serialize-a-comma-separated-list

2
Libraries/LibWeb/CSS/StyleValues/FilterValueListStyleValue.cpp
View File

@ -57,7 +57,7 @@ String FilterValueListStyleValue::to_string(SerializationMode mode) const
[&](FilterOperation::DropShadow const& drop_shadow) {
builder.append("drop-shadow("sv);
if (drop_shadow.color.has_value()) {
serialize_a_srgb_value(builder, *drop_shadow.color);
drop_shadow.color->serialize_a_srgb_value(builder);
builder.append(' ');
}
builder.appendff("{} {}", drop_shadow.offset_x, drop_shadow.offset_y);

2
Libraries/LibWeb/CSS/StyleValues/HSLColorStyleValue.cpp
View File

@ -40,7 +40,7 @@ bool HSLColorStyleValue::equals(StyleValue const& other) const
String HSLColorStyleValue::to_string(SerializationMode mode) const
{
if (auto color = to_color({}); color.has_value())
return serialize_a_srgb_value(color.value());
return color->serialize_a_srgb_value();
StringBuilder builder;

2
Libraries/LibWeb/CSS/StyleValues/HWBColorStyleValue.cpp
View File

@ -53,7 +53,7 @@ bool HWBColorStyleValue::equals(StyleValue const& other) const
String HWBColorStyleValue::to_string(SerializationMode mode) const
{
if (auto color = to_color({}); color.has_value())
return serialize_a_srgb_value(color.value());
return color->serialize_a_srgb_value();
StringBuilder builder;
builder.append("hwb("sv);

2
Libraries/LibWeb/CSS/StyleValues/RGBColorStyleValue.cpp
View File

@ -90,7 +90,7 @@ String RGBColorStyleValue::to_string(SerializationMode mode) const
return m_properties.name.value().to_string().to_ascii_lowercase();
if (auto color = to_color({}); color.has_value())
return serialize_a_srgb_value(color.value());
return color->serialize_a_srgb_value();
StringBuilder builder;
builder.append("rgb("sv);