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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
//! Animation implementation for various font-related types.
use super::{Animate, Procedure, ToAnimatedZero};
use crate::values::computed::font::FontVariationSettings;
use crate::values::computed::Number;
use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
use crate::values::generics::font::{FontSettings as GenericFontSettings, FontTag, VariationValue};
/// <https://drafts.csswg.org/css-fonts-4/#font-variation-settings-def>
impl Animate for FontVariationSettings {
#[inline]
fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
FontSettingTagIter::new(self, other)?
.map(|r| r.and_then(|(st, ot)| st.animate(&ot, procedure)))
.collect::<Result<Vec<ComputedVariationValue>, ()>>()
.map(|v| GenericFontSettings(v.into_boxed_slice()))
}
}
impl ComputeSquaredDistance for FontVariationSettings {
#[inline]
fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
FontSettingTagIter::new(self, other)?
.map(|r| r.and_then(|(st, ot)| st.compute_squared_distance(&ot)))
.sum()
}
}
impl ToAnimatedZero for FontVariationSettings {
#[inline]
fn to_animated_zero(&self) -> Result<Self, ()> {
Err(())
}
}
type ComputedVariationValue = VariationValue<Number>;
// FIXME: Could do a rename, this is only used for font variations.
struct FontSettingTagIterState<'a> {
tags: Vec<&'a ComputedVariationValue>,
index: usize,
prev_tag: FontTag,
}
impl<'a> FontSettingTagIterState<'a> {
fn new(tags: Vec<&'a ComputedVariationValue>) -> FontSettingTagIterState<'a> {
FontSettingTagIterState {
index: tags.len(),
tags,
prev_tag: FontTag(0),
}
}
}
/// Iterator for font-variation-settings tag lists
///
/// [CSS fonts level 4](https://drafts.csswg.org/css-fonts-4/#descdef-font-face-font-variation-settings)
/// defines the animation of font-variation-settings as follows:
///
/// Two declarations of font-feature-settings[sic] can be animated between if
/// they are "like". "Like" declarations are ones where the same set of
/// properties appear (in any order). Because succesive[sic] duplicate
/// properties are applied instead of prior duplicate properties, two
/// declarations can be "like" even if they have differing number of
/// properties. If two declarations are "like" then animation occurs pairwise
/// between corresponding values in the declarations.
///
/// In other words if we have the following lists:
///
/// "wght" 1.4, "wdth" 5, "wght" 2
/// "wdth" 8, "wght" 4, "wdth" 10
///
/// We should animate between:
///
/// "wdth" 5, "wght" 2
/// "wght" 4, "wdth" 10
///
/// This iterator supports this by sorting the two lists, then iterating them in
/// reverse, and skipping entries with repeated tag names. It will return
/// Some(Err()) if it reaches the end of one list before the other, or if the
/// tag names do not match.
///
/// For the above example, this iterator would return:
///
/// Some(Ok("wght" 2, "wght" 4))
/// Some(Ok("wdth" 5, "wdth" 10))
/// None
///
struct FontSettingTagIter<'a> {
a_state: FontSettingTagIterState<'a>,
b_state: FontSettingTagIterState<'a>,
}
impl<'a> FontSettingTagIter<'a> {
fn new(
a_settings: &'a FontVariationSettings,
b_settings: &'a FontVariationSettings,
) -> Result<FontSettingTagIter<'a>, ()> {
if a_settings.0.is_empty() || b_settings.0.is_empty() {
return Err(());
}
fn as_new_sorted_tags(tags: &[ComputedVariationValue]) -> Vec<&ComputedVariationValue> {
use std::iter::FromIterator;
let mut sorted_tags = Vec::from_iter(tags.iter());
sorted_tags.sort_by_key(|k| k.tag.0);
sorted_tags
}
Ok(FontSettingTagIter {
a_state: FontSettingTagIterState::new(as_new_sorted_tags(&a_settings.0)),
b_state: FontSettingTagIterState::new(as_new_sorted_tags(&b_settings.0)),
})
}
fn next_tag(state: &mut FontSettingTagIterState<'a>) -> Option<&'a ComputedVariationValue> {
if state.index == 0 {
return None;
}
state.index -= 1;
let tag = state.tags[state.index];
if tag.tag == state.prev_tag {
FontSettingTagIter::next_tag(state)
} else {
state.prev_tag = tag.tag;
Some(tag)
}
}
}
impl<'a> Iterator for FontSettingTagIter<'a> {
type Item = Result<(&'a ComputedVariationValue, &'a ComputedVariationValue), ()>;
fn next(
&mut self,
) -> Option<Result<(&'a ComputedVariationValue, &'a ComputedVariationValue), ()>> {
match (
FontSettingTagIter::next_tag(&mut self.a_state),
FontSettingTagIter::next_tag(&mut self.b_state),
) {
(Some(at), Some(bt)) if at.tag == bt.tag => Some(Ok((at, bt))),
(None, None) => None,
_ => Some(Err(())), // Mismatch number of unique tags or tag names.
}
}
}
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