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row.rs
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row.rs
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use std::iter::once;
use unicode_math_class::MathClass;
use crate::foundations::{Resolve, StyleChain};
use crate::layout::{Abs, AlignElem, Em, FixedAlignment, Frame, FrameKind, Point, Size};
use crate::math::{
alignments, scaled_font_size, spacing, EquationElem, FrameFragment, MathContext,
MathFragment, MathParItem, MathSize,
};
use crate::model::ParElem;
use super::fragment::SpacingFragment;
pub const TIGHT_LEADING: Em = Em::new(0.25);
/// A linear collection of [`MathFragment`]s.
#[derive(Debug, Default, Clone)]
pub struct MathRun(Vec<MathFragment>);
impl MathRun {
/// Takes the given [`MathFragment`]s and do some basic processing.
pub fn new(fragments: Vec<MathFragment>) -> Self {
let iter = fragments.into_iter().peekable();
let mut last: Option<usize> = None;
let mut space: Option<MathFragment> = None;
let mut resolved: Vec<MathFragment> = vec![];
for mut fragment in iter {
match fragment {
// Keep space only if supported by spaced fragments.
MathFragment::Space(_) => {
if last.is_some() {
space = Some(fragment);
}
continue;
}
// Explicit spacing disables automatic spacing.
MathFragment::Spacing(_) => {
last = None;
space = None;
resolved.push(fragment);
continue;
}
// Alignment points are resolved later.
MathFragment::Align => {
resolved.push(fragment);
continue;
}
// New line, new things.
MathFragment::Linebreak => {
resolved.push(fragment);
space = None;
last = None;
continue;
}
_ => {}
}
// Convert variable operators into binary operators if something
// precedes them and they are not preceded by a operator or comparator.
if fragment.class() == MathClass::Vary
&& matches!(
last.map(|i| resolved[i].class()),
Some(
MathClass::Normal
| MathClass::Alphabetic
| MathClass::Closing
| MathClass::Fence
)
)
{
fragment.set_class(MathClass::Binary);
}
// Insert spacing between the last and this item.
if let Some(i) = last {
if let Some(s) = spacing(&resolved[i], space.take(), &fragment) {
resolved.insert(i + 1, s);
}
}
last = Some(resolved.len());
resolved.push(fragment);
}
Self(resolved)
}
pub fn iter(&self) -> std::slice::Iter<'_, MathFragment> {
self.0.iter()
}
/// Split by linebreaks, and copy [`MathFragment`]s into rows.
pub fn rows(&self) -> Vec<Self> {
self.0
.split(|frag| matches!(frag, MathFragment::Linebreak))
.map(|slice| Self(slice.to_vec()))
.collect()
}
pub fn row_count(&self) -> usize {
let mut count =
1 + self.0.iter().filter(|f| matches!(f, MathFragment::Linebreak)).count();
// A linebreak at the very end does not introduce an extra row.
if let Some(f) = self.0.last() {
if matches!(f, MathFragment::Linebreak) {
count -= 1
}
}
count
}
pub fn ascent(&self) -> Abs {
self.iter().map(MathFragment::ascent).max().unwrap_or_default()
}
pub fn descent(&self) -> Abs {
self.iter().map(MathFragment::descent).max().unwrap_or_default()
}
pub fn class(&self) -> MathClass {
// Predict the class of the output of 'into_fragment'
if self.0.len() == 1 {
self.0
.first()
.map(|fragment| fragment.class())
.unwrap_or(MathClass::Normal)
} else {
// FrameFragment::new() (inside 'into_fragment' in this branch) defaults
// to MathClass::Normal for its class.
MathClass::Normal
}
}
pub fn into_frame(self, ctx: &MathContext, styles: StyleChain) -> Frame {
if !self.is_multiline() {
self.into_line_frame(&[], AlignElem::alignment_in(styles).resolve(styles).x)
} else {
self.multiline_frame_builder(ctx, styles).build()
}
}
pub fn into_fragment(self, ctx: &MathContext, styles: StyleChain) -> MathFragment {
if self.0.len() == 1 {
self.0.into_iter().next().unwrap()
} else {
FrameFragment::new(ctx, styles, self.into_frame(ctx, styles)).into()
}
}
/// Returns a builder that lays out the [`MathFragment`]s into a possibly
/// multi-row [`Frame`]. The rows are aligned using the same set of alignment
/// points computed from them as a whole.
pub fn multiline_frame_builder(
self,
ctx: &MathContext,
styles: StyleChain,
) -> MathRunFrameBuilder {
let rows: Vec<_> = self.rows();
let row_count = rows.len();
let alignments = alignments(&rows);
let leading = if EquationElem::size_in(styles) >= MathSize::Text {
ParElem::leading_in(styles)
} else {
let font_size = scaled_font_size(ctx, styles);
TIGHT_LEADING.at(font_size)
};
let align = AlignElem::alignment_in(styles).resolve(styles).x;
let mut frames: Vec<(Frame, Point)> = vec![];
let mut size = Size::zero();
for (i, row) in rows.into_iter().enumerate() {
if i == row_count - 1 && row.0.is_empty() {
continue;
}
let sub = row.into_line_frame(&alignments.points, align);
if i > 0 {
size.y += leading;
}
let mut pos = Point::with_y(size.y);
if alignments.points.is_empty() {
pos.x = align.position(alignments.width - sub.width());
}
size.x.set_max(sub.width());
size.y += sub.height();
frames.push((sub, pos));
}
MathRunFrameBuilder { size, frames }
}
/// Lay out [`MathFragment`]s into a one-row [`Frame`], using the
/// caller-provided alignment points.
pub fn into_line_frame(self, points: &[Abs], align: FixedAlignment) -> Frame {
let ascent = self.ascent();
let mut frame = Frame::soft(Size::new(Abs::zero(), ascent + self.descent()));
frame.set_baseline(ascent);
let mut next_x = {
let mut widths = Vec::new();
if !points.is_empty() && align != FixedAlignment::Start {
let mut width = Abs::zero();
for fragment in self.iter() {
if matches!(fragment, MathFragment::Align) {
widths.push(width);
width = Abs::zero();
} else {
width += fragment.width();
}
}
widths.push(width);
}
let widths = widths;
let mut prev_points = once(Abs::zero()).chain(points.iter().copied());
let mut point_widths = points.iter().copied().zip(widths);
let mut alternator = LeftRightAlternator::Right;
move || match align {
FixedAlignment::Start => prev_points.next(),
FixedAlignment::End => {
point_widths.next().map(|(point, width)| point - width)
}
_ => point_widths
.next()
.zip(prev_points.next())
.zip(alternator.next())
.map(|(((point, width), prev_point), alternator)| match alternator {
LeftRightAlternator::Left => prev_point,
LeftRightAlternator::Right => point - width,
}),
}
};
let mut x = next_x().unwrap_or_default();
for fragment in self.0.into_iter() {
if matches!(fragment, MathFragment::Align) {
x = next_x().unwrap_or(x);
continue;
}
let y = ascent - fragment.ascent();
let pos = Point::new(x, y);
x += fragment.width();
frame.push_frame(pos, fragment.into_frame());
}
frame.size_mut().x = x;
frame
}
pub fn into_par_items(self) -> Vec<MathParItem> {
let mut items = vec![];
let mut x = Abs::zero();
let mut ascent = Abs::zero();
let mut descent = Abs::zero();
let mut frame = Frame::new(Size::zero(), FrameKind::Soft);
let mut empty = true;
let finalize_frame = |frame: &mut Frame, x, ascent, descent| {
frame.set_size(Size::new(x, ascent + descent));
frame.set_baseline(Abs::zero());
frame.translate(Point::with_y(ascent));
};
let mut space_is_visible = false;
let is_relation = |f: &MathFragment| matches!(f.class(), MathClass::Relation);
let is_space = |f: &MathFragment| {
matches!(f, MathFragment::Space(_) | MathFragment::Spacing(_))
};
let mut iter = self.0.into_iter().peekable();
while let Some(fragment) = iter.next() {
if space_is_visible {
match fragment {
MathFragment::Space(width)
| MathFragment::Spacing(SpacingFragment { width, .. }) => {
items.push(MathParItem::Space(width));
continue;
}
_ => {}
}
}
let class = fragment.class();
let y = fragment.ascent();
ascent.set_max(y);
descent.set_max(fragment.descent());
let pos = Point::new(x, -y);
x += fragment.width();
frame.push_frame(pos, fragment.into_frame());
empty = false;
if class == MathClass::Binary
|| (class == MathClass::Relation
&& !iter.peek().map(is_relation).unwrap_or_default())
{
let mut frame_prev = std::mem::replace(
&mut frame,
Frame::new(Size::zero(), FrameKind::Soft),
);
finalize_frame(&mut frame_prev, x, ascent, descent);
items.push(MathParItem::Frame(frame_prev));
empty = true;
x = Abs::zero();
ascent = Abs::zero();
descent = Abs::zero();
space_is_visible = true;
if let Some(f_next) = iter.peek() {
if !is_space(f_next) {
items.push(MathParItem::Space(Abs::zero()));
}
}
} else {
space_is_visible = false;
}
}
// Don't use `frame.is_empty()` because even an empty frame can
// contribute width (if it had hidden content).
if !empty {
finalize_frame(&mut frame, x, ascent, descent);
items.push(MathParItem::Frame(frame));
}
items
}
fn is_multiline(&self) -> bool {
self.iter().any(|frag| matches!(frag, MathFragment::Linebreak))
}
}
impl<T: Into<MathFragment>> From<T> for MathRun {
fn from(fragment: T) -> Self {
Self(vec![fragment.into()])
}
}
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
enum LeftRightAlternator {
Left,
Right,
}
impl Iterator for LeftRightAlternator {
type Item = LeftRightAlternator;
fn next(&mut self) -> Option<Self::Item> {
let r = Some(*self);
match self {
Self::Left => *self = Self::Right,
Self::Right => *self = Self::Left,
}
r
}
}
/// How the rows from the [`MathRun`] should be aligned and merged into a [`Frame`].
pub struct MathRunFrameBuilder {
/// The size of the resulting frame.
pub size: Size,
/// Sub frames for each row, and the positions where they should be pushed into
/// the resulting frame.
pub frames: Vec<(Frame, Point)>,
}
impl MathRunFrameBuilder {
/// Consumes the builder and returns a [`Frame`].
pub fn build(self) -> Frame {
let mut frame = Frame::soft(self.size);
for (sub, pos) in self.frames.into_iter() {
frame.push_frame(pos, sub);
}
frame
}
}