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

Author: https://github.com/tcl3
Commit: ebd802f6fc
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6593
Reviewed-by: https://github.com/gmta ✅

Libraries/LibGfx/Color.cpp

@@ -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:

Libraries/LibGfx/Color.h

@@ -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);

Libraries/LibWeb/CSS/Serialize.cpp

@@ -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;

Libraries/LibWeb/CSS/Serialize.h

@@ -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

Libraries/LibWeb/CSS/StyleValues/FilterValueListStyleValue.cpp

@@ -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);

Libraries/LibWeb/CSS/StyleValues/HSLColorStyleValue.cpp

@@ -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;
 

Libraries/LibWeb/CSS/StyleValues/HWBColorStyleValue.cpp

@@ -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);

Libraries/LibWeb/CSS/StyleValues/RGBColorStyleValue.cpp

@@ -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);