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style: Document the font_metrics module.

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Emilio Cobos Álvarez 2016-12-31 15:08:53 +01:00
parent 858ee1f1ec
commit 68476df18e
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1 changed files with 12 additions and 3 deletions
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15
components/style/font_metrics.rs
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@ -2,6 +2,10 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! Access to font metrics from the style system.
#![deny(missing_docs)]
use Atom;
use app_units::Au;
use euclid::Size2D;
@ -11,13 +15,19 @@ use std::fmt;
/// value of certain CSS units like `ex`.
#[derive(Debug, PartialEq, Clone)]
pub struct FontMetrics {
/// The x-height of the font.
pub x_height: Au,
/// The zero advance.
pub zero_advance_measure: Size2D<Au>,
}
/// The result for querying font metrics for a given font family.
#[derive(Debug, PartialEq, Clone)]
pub enum FontMetricsQueryResult {
/// The font is available, but we may or may not have found any font metrics
/// for it.
Available(Option<FontMetrics>),
/// The font is not available.
NotAvailable,
}
@ -26,9 +36,8 @@ pub trait FontMetricsProvider: Send + Sync + fmt::Debug {
/// Obtain the metrics for given font family.
///
/// TODO: We could make this take the full list, I guess, and save a few
/// virtual calls.
///
/// This is not too common in practice though.
/// virtual calls in the case we are repeatedly unable to find font metrics?
/// That is not too common in practice though.
fn query(&self, _font_name: &Atom) -> FontMetricsQueryResult {
FontMetricsQueryResult::NotAvailable
}