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style: Add support for the 'ic' font-relative unit

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This is a "simplified" implementation of 'ic', similar to what Safari Preview
currently supports: it only considers the advance of U+6C34 if found in the
first available font, and otherwise falls back to the default of 1em.

(The spec allows for this "in cases where it is impossible or impractical to
determine the ideographic advance measure".)

Differential Revision: https://phabricator.services.mozilla.com/D132818
This commit is contained in:
Jonathan Kew 2023-06-06 16:46:36 +02:00 • committed by Oriol Brufau
parent 9430287183
commit 26c10339e3
4 changed files with 30 additions and 2 deletions
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27
components/style/values/specified/length.rs
View file

@ -59,6 +59,9 @@ pub enum FontRelativeLength {
/// A "cap" value: https://drafts.csswg.org/css-values/#cap
#[css(dimension)]
Cap(CSSFloat),
/// An "ic" value: https://drafts.csswg.org/css-values/#ic
#[css(dimension)]
Ic(CSSFloat),
/// A "rem" value: https://drafts.csswg.org/css-values/#rem
#[css(dimension)]
Rem(CSSFloat),
@ -93,6 +96,7 @@ impl FontRelativeLength {
FontRelativeLength::Ex(v) |
FontRelativeLength::Ch(v) |
FontRelativeLength::Cap(v) |
FontRelativeLength::Ic(v) |
FontRelativeLength::Rem(v) => v == 0.,
}
}
@ -103,6 +107,7 @@ impl FontRelativeLength {
FontRelativeLength::Ex(v) |
FontRelativeLength::Ch(v) |
FontRelativeLength::Cap(v) |
FontRelativeLength::Ic(v) |
FontRelativeLength::Rem(v) => v < 0.,
}
}
@ -119,12 +124,13 @@ impl FontRelativeLength {
(&Ex(one), &Ex(other)) => Ex(one + other),
(&Ch(one), &Ch(other)) => Ch(one + other),
(&Cap(one), &Cap(other)) => Cap(one + other),
(&Ic(one), &Ic(other)) => Ic(one + other),
(&Rem(one), &Rem(other)) => Rem(one + other),
// See https://github.com/rust-lang/rust/issues/68867. rustc isn't
// able to figure it own on its own so we help.
_ => unsafe {
match *self {
Em(..) | Ex(..) | Ch(..) | Cap(..) | Rem(..) => {},
Em(..) | Ex(..) | Ch(..) | Cap(..) | Ic(..) | Rem(..) => {},
}
debug_unreachable!("Forgot to handle unit in try_sum()")
},
@ -237,6 +243,20 @@ impl FontRelativeLength {
});
(reference_size, length)
},
FontRelativeLength::Ic(length) => {
let metrics =
query_font_metrics(context, base_size, FontMetricsOrientation::MatchContextPreferVertical);
let reference_size = metrics.ic_width.unwrap_or_else(|| {
// https://drafts.csswg.org/css-values/#ic
//
// In the cases where it is impossible or impractical to
// determine the ideographic advance measure, it must be
// assumed to be 1em.
//
reference_font_size
});
(reference_size, length)
},
FontRelativeLength::Rem(length) => {
// https://drafts.csswg.org/css-values/#rem:
//
@ -549,6 +569,7 @@ impl NoCalcLength {
"ex" => NoCalcLength::FontRelative(FontRelativeLength::Ex(value)),
"ch" => NoCalcLength::FontRelative(FontRelativeLength::Ch(value)),
"cap" => NoCalcLength::FontRelative(FontRelativeLength::Cap(value)),
"ic" => NoCalcLength::FontRelative(FontRelativeLength::Ic(value)),
"rem" => NoCalcLength::FontRelative(FontRelativeLength::Rem(value)),
// viewport percentages
"vw" if !context.in_page_rule() => {
@ -709,12 +730,13 @@ impl PartialOrd for FontRelativeLength {
(&Ex(ref one), &Ex(ref other)) => one.partial_cmp(other),
(&Ch(ref one), &Ch(ref other)) => one.partial_cmp(other),
(&Cap(ref one), &Cap(ref other)) => one.partial_cmp(other),
(&Ic(ref one), &Ic(ref other)) => one.partial_cmp(other),
(&Rem(ref one), &Rem(ref other)) => one.partial_cmp(other),
// See https://github.com/rust-lang/rust/issues/68867. rustc isn't
// able to figure it own on its own so we help.
_ => unsafe {
match *self {
Em(..) | Ex(..) | Ch(..) | Cap(..) | Rem(..) => {},
Em(..) | Ex(..) | Ch(..) | Cap(..) | Ic(..) | Rem(..) => {},
}
debug_unreachable!("Forgot an arm in partial_cmp?")
},
@ -732,6 +754,7 @@ impl Mul<CSSFloat> for FontRelativeLength {
FontRelativeLength::Ex(v) => FontRelativeLength::Ex(v * scalar),
FontRelativeLength::Ch(v) => FontRelativeLength::Ch(v * scalar),
FontRelativeLength::Cap(v) => FontRelativeLength::Cap(v * scalar),
FontRelativeLength::Ic(v) => FontRelativeLength::Ic(v * scalar),
FontRelativeLength::Rem(v) => FontRelativeLength::Rem(v * scalar),
}
}