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style: Make the Gecko font-size calc() code do what it means to do.

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It makes no sense to pass a custom base size of zero in presence of rem, ex, or
ch units.

Bug: 1431031
Reviewed-by: Manishearth
MozReview-Commit-ID: 7ZZwRzQKREX
This commit is contained in:
Emilio Cobos Álvarez 2018-01-17 17:20:20 +01:00
parent aee0d694cc
commit 212b2f56c7
No known key found for this signature in database
GPG key ID: 056B727BB9C1027C
3 changed files with 61 additions and 29 deletions
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53
components/style/values/specified/length.rs
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@ -71,11 +71,17 @@ pub enum FontRelativeLength {
/// A source to resolve font-relative units against
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum FontBaseSize {
/// Use the font-size of the current element
/// Use the font-size of the current element.
CurrentStyle,
/// Use the inherited font-size
/// Use the inherited font-size.
InheritedStyle,
/// Use a custom base size
/// Use the inherited font-size, but strip em units.
///
/// FIXME(emilio): This is very complex, and should go away.
InheritedStyleButStripEmUnits,
/// Use a custom base size.
///
/// FIXME(emilio): This is very dubious, and only used for MathML.
Custom(Au),
}
@ -85,6 +91,7 @@ impl FontBaseSize {
match *self {
FontBaseSize::Custom(size) => size,
FontBaseSize::CurrentStyle => context.style().get_font().clone_font_size().size(),
FontBaseSize::InheritedStyleButStripEmUnits |
FontBaseSize::InheritedStyle => context.style().get_parent_font().clone_font_size().size(),
}
}
@ -99,36 +106,48 @@ impl FontRelativeLength {
CSSPixelLength::new(pixel)
}
/// Return reference font size. We use the base_size flag to pass a different size
/// for computing font-size and unconstrained font-size.
/// This returns a pair, the first one is the reference font size, and the second one is the
/// unpacked relative length.
/// Return reference font size.
///
/// We use the base_size flag to pass a different size for computing
/// font-size and unconstrained font-size.
///
/// This returns a pair, the first one is the reference font size, and the
/// second one is the unpacked relative length.
fn reference_font_size_and_length(
&self,
context: &Context,
base_size: FontBaseSize,
) -> (Au, CSSFloat) {
fn query_font_metrics(context: &Context, reference_font_size: Au) -> FontMetricsQueryResult {
context.font_metrics_provider.query(context.style().get_font(),
reference_font_size,
context.style().writing_mode,
context.in_media_query,
context.device())
fn query_font_metrics(
context: &Context,
reference_font_size: Au,
) -> FontMetricsQueryResult {
context.font_metrics_provider.query(
context.style().get_font(),
reference_font_size,
context.style().writing_mode,
context.in_media_query,
context.device(),
)
}
let reference_font_size = base_size.resolve(context);
match *self {
FontRelativeLength::Em(length) => {
if context.for_non_inherited_property.is_some() {
if matches!(base_size, FontBaseSize::CurrentStyle) {
if base_size == FontBaseSize::CurrentStyle {
context.rule_cache_conditions.borrow_mut()
.set_font_size_dependency(
reference_font_size.into()
);
}
}
(reference_font_size, length)
if base_size == FontBaseSize::InheritedStyleButStripEmUnits {
(Au(0), length)
} else {
(reference_font_size, length)
}
},
FontRelativeLength::Ex(length) => {
if context.for_non_inherited_property.is_some() {
@ -182,7 +201,7 @@ impl FontRelativeLength {
// https://drafts.csswg.org/css-values/#rem:
//
// When specified on the font-size property of the root
// element, the rem units refer to the property’s initial
// element, the rem units refer to the property's initial
// value.
//
let reference_size = if context.is_root_element || context.in_media_query {