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LibWeb: Add cap and rcap Length units

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As noted, the ascent of the font is not the best heuristic for this, but
it is one that's listed as OK to use by the spec:

> In the cases where it is impossible or impractical to determine the
  cap-height, the font’s ascent must be used.
This commit is contained in:
Sam Atkins 2023-04-28 17:10:30 +01:00 • committed by Andreas Kling
parent a8e0fa403a
commit 03ed37eb14
Notes: sideshowbarker 2024-07-16 23:23:26 +09:00
2 changed files with 20 additions and 0 deletions
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15
Userland/Libraries/LibWeb/CSS/Length.cpp
View file

@ -21,6 +21,9 @@ namespace Web::CSS {
Length::FontMetrics::FontMetrics(CSSPixels font_size, Gfx::FontPixelMetrics const& pixel_metrics, CSSPixels line_height)
: font_size(font_size)
, x_height(pixel_metrics.x_height)
// FIXME: This is only approximately the cap height. The spec suggests measuring the "O" glyph:
// https://www.w3.org/TR/css-values-4/#cap
, cap_height(pixel_metrics.ascent)
, zero_advance(pixel_metrics.advance_of_ascii_zero + pixel_metrics.glyph_spacing)
, line_height(line_height)
{
@ -78,6 +81,10 @@ CSSPixels Length::relative_length_to_px(CSSPixelRect const& viewport_rect, FontM
return m_value * font_metrics.x_height;
case Type::Rex:
return m_value * root_font_metrics.x_height;
case Type::Cap:
return m_value * font_metrics.cap_height;
case Type::Rcap:
return m_value * root_font_metrics.cap_height;
case Type::Ch:
return m_value * font_metrics.zero_advance;
case Type::Rch:
@ -143,6 +150,10 @@ char const* Length::unit_name() const
return "ex";
case Type::Rex:
return "rex";
case Type::Cap:
return "cap";
case Type::Rcap:
return "rcap";
case Type::Ch:
return "ch";
case Type::Rch:
@ -189,6 +200,10 @@ Optional<Length::Type> Length::unit_from_name(StringView name)
return Length::Type::Ex;
} else if (name.equals_ignoring_ascii_case("rex"sv)) {
return Length::Type::Rex;
} else if (name.equals_ignoring_ascii_case("cap"sv)) {
return Length::Type::Cap;
} else if (name.equals_ignoring_ascii_case("rcap"sv)) {
return Length::Type::Rcap;
} else if (name.equals_ignoring_ascii_case("ch"sv)) {
return Length::Type::Ch;
} else if (name.equals_ignoring_ascii_case("rch"sv)) {

5
Userland/Libraries/LibWeb/CSS/Length.h
View file

@ -22,6 +22,8 @@ public:
Rem,
Ex,
Rex,
Cap,
Rcap,
Ch,
Rch,
Lh,
@ -51,6 +53,7 @@ public:
CSSPixels font_size;
CSSPixels x_height;
CSSPixels cap_height;
CSSPixels zero_advance;
CSSPixels line_height;
};
@ -87,6 +90,8 @@ public:
|| m_type == Type::Rem
|| m_type == Type::Ex
|| m_type == Type::Rex
|| m_type == Type::Cap
|| m_type == Type::Rcap
|| m_type == Type::Ch
|| m_type == Type::Rch
|| m_type == Type::Lh