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stylo: Use gecko's font metrics

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Manish Goregaokar 2017-04-07 15:49:44 -07:00 • committed by Manish Goregaokar
parent 1154600dd4
commit 25667d0321
10 changed files with 72 additions and 58 deletions
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50
components/style/values/specified/length.rs
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@ -9,7 +9,7 @@
use app_units::Au;
use cssparser::{Parser, Token};
use euclid::size::Size2D;
use font_metrics::FontMetrics;
use font_metrics::FontMetricsQueryResult;
use parser::{Parse, ParserContext};
use std::{cmp, fmt, mem};
use std::ascii::AsciiExt;
@ -69,22 +69,17 @@ impl ToCss for FontRelativeLength {
}
impl FontRelativeLength {
/// Gets the first available font metrics from the current context's
/// font-family list.
pub fn find_first_available_font_metrics(context: &Context) -> Option<FontMetrics> {
use font_metrics::FontMetricsQueryResult::*;
for family in context.style().get_font().font_family_iter() {
if let Available(metrics) = context.font_metrics_provider.query(family.atom()) {
return metrics;
}
}
None
}
/// Computes the font-relative length. We use the use_inherited flag to
/// special-case the computation of font-size.
pub fn to_computed_value(&self, context: &Context, use_inherited: bool) -> Au {
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 = if use_inherited {
context.inherited_style().get_font().clone_font_size()
} else {
@ -95,33 +90,20 @@ impl FontRelativeLength {
match *self {
FontRelativeLength::Em(length) => reference_font_size.scale_by(length),
FontRelativeLength::Ex(length) => {
match Self::find_first_available_font_metrics(context) {
Some(metrics) => metrics.x_height,
match query_font_metrics(context, reference_font_size) {
FontMetricsQueryResult::Available(metrics) => metrics.x_height.scale_by(length),
// https://drafts.csswg.org/css-values/#ex
//
// In the cases where it is impossible or impractical to
// determine the x-height, a value of 0.5em must be
// assumed.
//
None => reference_font_size.scale_by(0.5 * length),
FontMetricsQueryResult::NotAvailable => reference_font_size.scale_by(0.5 * length),
}
},
FontRelativeLength::Ch(length) => {
let wm = context.style().writing_mode;
// TODO(emilio, #14144): Compute this properly once we support
// all the relevant writing-mode related properties, this should
// be equivalent to "is the text in the block direction?".
let vertical = wm.is_vertical();
match Self::find_first_available_font_metrics(context) {
Some(metrics) => {
if vertical {
metrics.zero_advance_measure.height
} else {
metrics.zero_advance_measure.width
}
}
match query_font_metrics(context, reference_font_size) {
FontMetricsQueryResult::Available(metrics) => metrics.zero_advance_measure.scale_by(length),
// https://drafts.csswg.org/css-values/#ch
//
// In the cases where it is impossible or impractical to
@ -132,8 +114,8 @@ impl FontRelativeLength {
// writing-mode is vertical-rl or vertical-lr and
// text-orientation is upright).
//
None => {
if vertical {
FontMetricsQueryResult::NotAvailable => {
if context.style().writing_mode.is_vertical() {
reference_font_size.scale_by(length)
} else {
reference_font_size.scale_by(0.5 * length)