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Extract page layout from flow layout (#4937)

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Laurenz 2024-09-11 18:46:33 +02:00 committed by GitHub
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7 changed files with 660 additions and 635 deletions
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71
crates/typst/src/layout/flow/mod.rs
View File

@ -3,7 +3,6 @@
//! - inside of a container, into a [`Frame`] or [`Fragment`]. //! - inside of a container, into a [`Frame`] or [`Fragment`].
mod collect; mod collect;
mod pages;
use std::collections::HashSet; use std::collections::HashSet;
use std::num::NonZeroUsize; use std::num::NonZeroUsize;
@ -12,7 +11,6 @@ use bumpalo::Bump;
use comemo::{Track, Tracked, TrackedMut}; use comemo::{Track, Tracked, TrackedMut};
use self::collect::{collect, BlockChild, Child, LineChild, PlacedChild}; use self::collect::{collect, BlockChild, Child, LineChild, PlacedChild};
use self::pages::layout_pages;
use crate::diag::{bail, At, SourceResult}; use crate::diag::{bail, At, SourceResult};
use crate::engine::{Engine, Route, Sink, Traced}; use crate::engine::{Engine, Route, Sink, Traced};
use crate::foundations::{ use crate::foundations::{
@ -27,8 +25,7 @@ use crate::layout::{
OuterHAlignment, Point, Region, Regions, Rel, Size, OuterHAlignment, Point, Region, Regions, Rel, Size,
}; };
use crate::model::{ use crate::model::{
Document, DocumentInfo, FootnoteElem, FootnoteEntry, ParLine, ParLineMarker, FootnoteElem, FootnoteEntry, ParLine, ParLineMarker, ParLineNumberingScope,
ParLineNumberingScope,
}; };
use crate::realize::{realize, Arenas, Pair, RealizationKind}; use crate::realize::{realize, Arenas, Pair, RealizationKind};
use crate::syntax::Span; use crate::syntax::Span;
@ -36,70 +33,6 @@ use crate::text::TextElem;
use crate::utils::{NonZeroExt, Numeric}; use crate::utils::{NonZeroExt, Numeric};
use crate::World; use crate::World;
/// Layout content into a document.
///
/// This first performs root-level realization and then lays out the resulting
/// elements. In contrast to [`layout_fragment`], this does not take regions
/// since the regions are defined by the page configuration in the content and
/// style chain.
#[typst_macros::time(name = "document")]
pub fn layout_document(
engine: &mut Engine,
content: &Content,
styles: StyleChain,
) -> SourceResult<Document> {
layout_document_impl(
engine.world,
engine.introspector,
engine.traced,
TrackedMut::reborrow_mut(&mut engine.sink),
engine.route.track(),
content,
styles,
)
}
/// The internal implementation of `layout_document`.
#[comemo::memoize]
fn layout_document_impl(
world: Tracked<dyn World + '_>,
introspector: Tracked<Introspector>,
traced: Tracked<Traced>,
sink: TrackedMut<Sink>,
route: Tracked<Route>,
content: &Content,
styles: StyleChain,
) -> SourceResult<Document> {
let mut locator = Locator::root().split();
let mut engine = Engine {
world,
introspector,
traced,
sink,
route: Route::extend(route).unnested(),
};
// Mark the external styles as "outside" so that they are valid at the page
// level.
let styles = styles.to_map().outside();
let styles = StyleChain::new(&styles);
let arenas = Arenas::default();
let mut info = DocumentInfo::default();
let mut children = realize(
RealizationKind::Root(&mut info),
&mut engine,
&mut locator,
&arenas,
content,
styles,
)?;
let pages = layout_pages(&mut engine, &mut children, locator, styles)?;
Ok(Document { pages, info, introspector: Introspector::default() })
}
/// Layout content into multiple regions. /// Layout content into multiple regions.
/// ///
/// When just layouting into a single region, prefer [`layout_frame`]. /// When just layouting into a single region, prefer [`layout_frame`].
@ -220,7 +153,7 @@ fn layout_fragment_impl(
/// Layout flow content. /// Layout flow content.
#[allow(clippy::too_many_arguments)] #[allow(clippy::too_many_arguments)]
fn layout_flow( pub(crate) fn layout_flow(
engine: &mut Engine, engine: &mut Engine,
bump: &Bump, bump: &Bump,
children: &[Pair], children: &[Pair],

566
crates/typst/src/layout/flow/pages.rs
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@ -1,566 +0,0 @@
use std::collections::HashSet;
use comemo::{Track, Tracked, TrackedMut};
use super::layout_flow;
use crate::diag::SourceResult;
use crate::engine::{Engine, Route, Sink, Traced};
use crate::foundations::{Content, NativeElement, Resolve, Smart, StyleChain, Styles};
use crate::introspection::{
Counter, CounterDisplayElem, CounterKey, Introspector, Locator, LocatorLink,
ManualPageCounter, SplitLocator, Tag, TagElem, TagKind,
};
use crate::layout::{
layout_frame, Abs, AlignElem, Alignment, Axes, Binding, ColumnsElem, Dir, Frame,
FrameItem, HAlignment, Length, OuterVAlignment, Page, PageElem, PagebreakElem, Paper,
Parity, Point, Region, Regions, Rel, Sides, Size, VAlignment,
};
use crate::model::Numbering;
use crate::realize::Pair;
use crate::syntax::Span;
use crate::text::TextElem;
use crate::utils::Numeric;
use crate::visualize::Paint;
use crate::World;
/// An item in page layout.
enum PageItem<'a> {
/// A page run containing content. All runs will be layouted in parallel.
Run(&'a [Pair<'a>], StyleChain<'a>, Locator<'a>),
/// Tags in between pages. These will be prepended to the first start of
/// the next page, or appended at the very end of the final page if there is
/// no next page.
Tags(&'a [Pair<'a>]),
/// An instruction to possibly add a page to bring the page number parity to
/// the desired state. Can only be done at the end, sequentially, because it
/// requires knowledge of the concrete page number.
Parity(Parity, StyleChain<'a>, Locator<'a>),
}
/// A mostly finished layout for one page. Needs only knowledge of its exact
/// page number to be finalized into a `Page`. (Because the margins can depend
/// on the page number.)
#[derive(Clone)]
struct LayoutedPage {
inner: Frame,
margin: Sides<Abs>,
binding: Binding,
two_sided: bool,
header: Option<Frame>,
footer: Option<Frame>,
background: Option<Frame>,
foreground: Option<Frame>,
fill: Smart<Option<Paint>>,
numbering: Option<Numbering>,
}
/// Layouts the document's pages.
pub fn layout_pages<'a>(
engine: &mut Engine,
children: &'a mut [Pair<'a>],
locator: SplitLocator<'a>,
styles: StyleChain<'a>,
) -> SourceResult<Vec<Page>> {
// Slice up the children into logical parts.
let items = collect_page_items(children, locator, styles);
// Layout the page runs in parallel.
let mut runs = engine.parallelize(
items.iter().filter_map(|item| match item {
PageItem::Run(children, initial, locator) => {
Some((children, initial, locator.relayout()))
}
_ => None,
}),
|engine, (children, initial, locator)| {
layout_page_run(engine, children, locator, *initial)
},
);
let mut pages = vec![];
let mut tags = vec![];
let mut counter = ManualPageCounter::new();
// Collect and finalize the runs, handling things like page parity and tags
// between pages.
for item in &items {
match item {
PageItem::Run(..) => {
let layouted = runs.next().unwrap()?;
for layouted in layouted {
let page = finalize_page(engine, &mut counter, &mut tags, layouted)?;
pages.push(page);
}
}
PageItem::Parity(parity, initial, locator) => {
if !parity.matches(pages.len()) {
continue;
}
let layouted = layout_blank_page(engine, locator.relayout(), *initial)?;
let page = finalize_page(engine, &mut counter, &mut tags, layouted)?;
pages.push(page);
}
PageItem::Tags(items) => {
tags.extend(
items
.iter()
.filter_map(|(c, _)| c.to_packed::<TagElem>())
.map(|elem| elem.tag.clone()),
);
}
}
}
// Add the remaining tags to the very end of the last page.
if !tags.is_empty() {
let last = pages.last_mut().unwrap();
let pos = Point::with_y(last.frame.height());
last.frame
.push_multiple(tags.into_iter().map(|tag| (pos, FrameItem::Tag(tag))));
}
Ok(pages)
}
/// Slices up the children into logical parts, processing styles and handling
/// things like tags and weak pagebreaks.
fn collect_page_items<'a>(
mut children: &'a mut [Pair<'a>],
mut locator: SplitLocator<'a>,
mut initial: StyleChain<'a>,
) -> Vec<PageItem<'a>> {
// The collected page-level items.
let mut items: Vec<PageItem<'a>> = vec![];
// When this is true, an empty page should be added to `pages` at the end.
let mut staged_empty_page = true;
// The `children` are a flat list of flow-level items and pagebreaks. This
// loops splits it up into pagebreaks and consecutive slices of
// non-pagebreaks. From these pieces, we build page items that we can then
// layout in parallel.
while let Some(&(elem, styles)) = children.first() {
if let Some(pagebreak) = elem.to_packed::<PagebreakElem>() {
// Add a blank page if we encounter a strong pagebreak and there was
// a staged empty page.
let strong = !pagebreak.weak(styles);
if strong && staged_empty_page {
let locator = locator.next(&elem.span());
items.push(PageItem::Run(&[], initial, locator));
}
// Add an instruction to adjust the page parity if requested.
if let Some(parity) = pagebreak.to(styles) {
let locator = locator.next(&elem.span());
items.push(PageItem::Parity(parity, styles, locator));
}
// The initial styles for the next page are ours unless this is a
// "boundary" pagebreak. Such a pagebreak is generated at the end of
// the scope of a page set rule to ensure a page boundary. It's
// styles correspond to the styles _before_ the page set rule, so we
// don't want to apply it to a potential empty page.
if !pagebreak.boundary(styles) {
initial = styles;
}
// Stage an empty page after a strong pagebreak.
staged_empty_page |= strong;
// Advance to the next child.
children = &mut children[1..];
} else {
// Find the end of the consecutive non-pagebreak run.
let end =
children.iter().take_while(|(c, _)| !c.is::<PagebreakElem>()).count();
// Migrate start tags without accompanying end tags from before a
// pagebreak to after it.
let end = migrate_unterminated_tags(children, end);
if end == 0 {
continue;
}
// Advance to the rest of the children.
let (group, rest) = children.split_at_mut(end);
children = rest;
// If all that is left now are tags, then we don't want to add a
// page just for them (since no group would have been detected in a
// tagless layout and tags should never affect the layout). For this
// reason, we remember them in a `PageItem::Tags` and later insert
// them at the _very start_ of the next page, even before the
// header.
//
// We don't do this if all that's left is end boundary pagebreaks
// and if an empty page is still staged, since then we can just
// conceptually replace that final page with us.
if group.iter().all(|(c, _)| c.is::<TagElem>())
&& !(staged_empty_page
&& children.iter().all(|&(c, s)| {
c.to_packed::<PagebreakElem>().is_some_and(|c| c.boundary(s))
}))
{
items.push(PageItem::Tags(group));
continue;
}
// Record a page run and then disregard a staged empty page because
// we have real content now.
let locator = locator.next(&elem.span());
items.push(PageItem::Run(group, initial, locator));
staged_empty_page = false;
}
}
// Flush a staged empty page.
if staged_empty_page {
items.push(PageItem::Run(&[], initial, locator.next(&())));
}
items
}
/// Migrates trailing start tags without accompanying end tags tags from before
/// a pagebreak to after it. Returns the position right after the last
/// non-migrated tag.
///
/// This is important because we want the positions of introspectible elements
/// that technically started before a pagebreak, but have no visible content
/// yet, to be after the pagebreak. A typical case where this happens is `show
/// heading: it => pagebreak() + it`.
fn migrate_unterminated_tags(children: &mut [Pair], mid: usize) -> usize {
// Compute the range from before the first trailing tag to after the last
// following pagebreak.
let (before, after) = children.split_at(mid);
let start = mid - before.iter().rev().take_while(|&(c, _)| c.is::<TagElem>()).count();
let end = mid + after.iter().take_while(|&(c, _)| c.is::<PagebreakElem>()).count();
// Determine the set of tag locations which we won't migrate (because they
// are terminated).
let excluded: HashSet<_> = children[start..mid]
.iter()
.filter_map(|(c, _)| c.to_packed::<TagElem>())
.filter(|elem| elem.tag.kind() == TagKind::End)
.map(|elem| elem.tag.location())
.collect();
// A key function that partitions the area of interest into three groups:
// Excluded tags (-1) | Pagebreaks (0) | Migrated tags (1).
let key = |(c, _): &Pair| match c.to_packed::<TagElem>() {
Some(elem) => {
if excluded.contains(&elem.tag.location()) {
-1
} else {
1
}
}
None => 0,
};
// Partition the children using a *stable* sort. While it would be possible
// to write a more efficient direct algorithm for this, the sort version is
// less likely to have bugs and this is absolutely not on a hot path.
children[start..end].sort_by_key(key);
// Compute the new end index, right before the pagebreaks.
start + children[start..end].iter().take_while(|pair| key(pair) == -1).count()
}
/// Layout a page run with uniform properties.
#[typst_macros::time(name = "page run")]
fn layout_page_run(
engine: &mut Engine,
children: &[Pair],
locator: Locator,
initial: StyleChain,
) -> SourceResult<Vec<LayoutedPage>> {
layout_page_run_impl(
engine.world,
engine.introspector,
engine.traced,
TrackedMut::reborrow_mut(&mut engine.sink),
engine.route.track(),
children,
locator.track(),
initial,
)
}
/// Layout a single page suitable for parity adjustment.
fn layout_blank_page(
engine: &mut Engine,
locator: Locator,
initial: StyleChain,
) -> SourceResult<LayoutedPage> {
let layouted = layout_page_run(engine, &[], locator, initial)?;
Ok(layouted.into_iter().next().unwrap())
}
/// The internal implementation of `layout_page_run`.
#[comemo::memoize]
#[allow(clippy::too_many_arguments)]
fn layout_page_run_impl(
world: Tracked<dyn World + '_>,
introspector: Tracked<Introspector>,
traced: Tracked<Traced>,
sink: TrackedMut<Sink>,
route: Tracked<Route>,
children: &[Pair],
locator: Tracked<Locator>,
initial: StyleChain,
) -> SourceResult<Vec<LayoutedPage>> {
let link = LocatorLink::new(locator);
let mut locator = Locator::link(&link).split();
let mut engine = Engine {
world,
introspector,
traced,
sink,
route: Route::extend(route),
};
// Determine the page-wide styles.
let styles = determine_page_styles(children, initial);
let styles = StyleChain::new(&styles);
// When one of the lengths is infinite the page fits its content along
// that axis.
let width = PageElem::width_in(styles).unwrap_or(Abs::inf());
let height = PageElem::height_in(styles).unwrap_or(Abs::inf());
let mut size = Size::new(width, height);
if PageElem::flipped_in(styles) {
std::mem::swap(&mut size.x, &mut size.y);
}
let mut min = width.min(height);
if !min.is_finite() {
min = Paper::A4.width();
}
// Determine the margins.
let default = Rel::<Length>::from((2.5 / 21.0) * min);
let margin = PageElem::margin_in(styles);
let two_sided = margin.two_sided.unwrap_or(false);
let margin = margin
.sides
.map(|side| side.and_then(Smart::custom).unwrap_or(default))
.resolve(styles)
.relative_to(size);
// Realize columns.
let area = size - margin.sum_by_axis();
let mut regions = Regions::repeat(area, area.map(Abs::is_finite));
regions.root = true;
let fill = PageElem::fill_in(styles);
let foreground = PageElem::foreground_in(styles);
let background = PageElem::background_in(styles);
let header_ascent = PageElem::header_ascent_in(styles).relative_to(margin.top);
let footer_descent = PageElem::footer_descent_in(styles).relative_to(margin.bottom);
let numbering = PageElem::numbering_in(styles);
let number_align = PageElem::number_align_in(styles);
let binding =
PageElem::binding_in(styles).unwrap_or_else(|| match TextElem::dir_in(styles) {
Dir::LTR => Binding::Left,
_ => Binding::Right,
});
// Construct the numbering (for header or footer).
let numbering_marginal = numbering.as_ref().map(|numbering| {
let both = match numbering {
Numbering::Pattern(pattern) => pattern.pieces() >= 2,
Numbering::Func(_) => true,
};
let mut counter = CounterDisplayElem::new(
Counter::new(CounterKey::Page),
Smart::Custom(numbering.clone()),
both,
)
.pack();
// We interpret the Y alignment as selecting header or footer
// and then ignore it for aligning the actual number.
if let Some(x) = number_align.x() {
counter = counter.aligned(x.into());
}
counter
});
let header = PageElem::header_in(styles);
let footer = PageElem::footer_in(styles);
let (header, footer) = if matches!(number_align.y(), Some(OuterVAlignment::Top)) {
(header.as_ref().unwrap_or(&numbering_marginal), footer.as_ref().unwrap_or(&None))
} else {
(header.as_ref().unwrap_or(&None), footer.as_ref().unwrap_or(&numbering_marginal))
};
// Layout the children.
let bump = bumpalo::Bump::new();
let fragment = layout_flow(
&mut engine,
&bump,
children,
&mut locator,
styles,
regions,
PageElem::columns_in(styles),
ColumnsElem::gutter_in(styles),
Span::detached(),
)?;
// Layouts a single marginal.
let mut layout_marginal = |content: &Option<Content>, area, align| {
let Some(content) = content else { return Ok(None) };
let aligned = content.clone().styled(AlignElem::set_alignment(align));
layout_frame(
&mut engine,
&aligned,
locator.next(&content.span()),
styles,
Region::new(area, Axes::splat(true)),
)
.map(Some)
};
// Layout marginals.
let mut layouted = Vec::with_capacity(fragment.len());
for inner in fragment {
let header_size = Size::new(inner.width(), margin.top - header_ascent);
let footer_size = Size::new(inner.width(), margin.bottom - footer_descent);
let full_size = inner.size() + margin.sum_by_axis();
let mid = HAlignment::Center + VAlignment::Horizon;
layouted.push(LayoutedPage {
inner,
fill: fill.clone(),
numbering: numbering.clone(),
header: layout_marginal(header, header_size, Alignment::BOTTOM)?,
footer: layout_marginal(footer, footer_size, Alignment::TOP)?,
background: layout_marginal(background, full_size, mid)?,
foreground: layout_marginal(foreground, full_size, mid)?,
margin,
binding,
two_sided,
});
}
Ok(layouted)
}
/// Determines the styles used for a page run itself and page-level content like
/// marginals and footnotes.
///
/// As a base, we collect the styles that are shared by all elements on the page
/// run. As a fallback if there are no elements, we use the styles active at the
/// pagebreak that introduced the page (at the very start, we use the default
/// styles). Then, to produce our page styles, we filter this list of styles
/// according to a few rules:
///
/// - Other styles are only kept if they are `outside && (initial || liftable)`.
/// - "Outside" means they were not produced within a show rule or that the
/// show rule "broke free" to the page level by emitting page styles.
/// - "Initial" means they were active at the pagebreak that introduced the
/// page. Since these are intuitively already active, they should be kept even
/// if not liftable. (E.g. `text(red, page(..)`) makes the footer red.)
/// - "Liftable" means they can be lifted to the page-level even though they
/// weren't yet active at the very beginning. Set rule styles are liftable as
/// opposed to direct constructor calls:
/// - For `set page(..); set text(red)` the red text is kept even though it
/// comes after the weak pagebreak from set page.
/// - For `set page(..); text(red)[..]` the red isn't kept because the
/// constructor styles are not liftable.
fn determine_page_styles(children: &[Pair], initial: StyleChain) -> Styles {
// Determine the shared styles (excluding tags).
let tagless = children.iter().filter(|(c, _)| !c.is::<TagElem>()).map(|&(_, s)| s);
let base = StyleChain::trunk(tagless).unwrap_or(initial).to_map();
// Determine the initial styles that are also shared by everything. We can't
// use `StyleChain::trunk` because it currently doesn't deal with partially
// shared links (where a subslice matches).
let trunk_len = initial
.to_map()
.as_slice()
.iter()
.zip(base.as_slice())
.take_while(|&(a, b)| a == b)
.count();
// Filter the base styles according to our rules.
base.into_iter()
.enumerate()
.filter(|(i, style)| {
let initial = *i < trunk_len;
style.outside() && (initial || style.liftable())
})
.map(|(_, style)| style)
.collect()
}
/// Piece together the inner page frame and the marginals. We can only do this
/// at the very end because inside/outside margins require knowledge of the
/// physical page number, which is unknown during parallel layout.
fn finalize_page(
engine: &mut Engine,
counter: &mut ManualPageCounter,
tags: &mut Vec<Tag>,
LayoutedPage {
inner,
mut margin,
binding,
two_sided,
header,
footer,
background,
foreground,
fill,
numbering,
}: LayoutedPage,
) -> SourceResult<Page> {
// If two sided, left becomes inside and right becomes outside.
// Thus, for left-bound pages, we want to swap on even pages and
// for right-bound pages, we want to swap on odd pages.
if two_sided && binding.swap(counter.physical()) {
std::mem::swap(&mut margin.left, &mut margin.right);
}
// Create a frame for the full page.
let mut frame = Frame::hard(inner.size() + margin.sum_by_axis());
// Add tags.
for tag in tags.drain(..) {
frame.push(Point::zero(), FrameItem::Tag(tag));
}
// Add the "before" marginals. The order in which we push things here is
// important as it affects the relative ordering of introspectible elements
// and thus how counters resolve.
if let Some(background) = background {
frame.push_frame(Point::zero(), background);
}
if let Some(header) = header {
frame.push_frame(Point::with_x(margin.left), header);
}
// Add the inner contents.
frame.push_frame(Point::new(margin.left, margin.top), inner);
// Add the "after" marginals.
if let Some(footer) = footer {
let y = frame.height() - footer.height();
frame.push_frame(Point::new(margin.left, y), footer);
}
if let Some(foreground) = foreground {
frame.push_frame(Point::zero(), foreground);
}
// Apply counter updates from within the page to the manual page counter.
counter.visit(engine, &frame)?;
// Get this page's number and then bump the counter for the next page.
let number = counter.logical();
counter.step();
Ok(Page { frame, fill, numbering, number })
}

2
crates/typst/src/layout/mod.rs
View File

@ -23,6 +23,7 @@ mod length;
mod measure_; mod measure_;
mod pad; mod pad;
mod page; mod page;
mod pages;
mod place; mod place;
mod point; mod point;
mod ratio; mod ratio;
@ -55,6 +56,7 @@ pub use self::length::*;
pub use self::measure_::*; pub use self::measure_::*;
pub use self::pad::*; pub use self::pad::*;
pub use self::page::*; pub use self::page::*;
pub use self::pages::*;
pub use self::place::*; pub use self::place::*;
pub use self::point::*; pub use self::point::*;
pub use self::ratio::*; pub use self::ratio::*;

164
crates/typst/src/layout/pages/collect.rs Normal file
View File

@ -0,0 +1,164 @@
use std::collections::HashSet;
use crate::foundations::StyleChain;
use crate::introspection::{Locator, SplitLocator, TagElem, TagKind};
use crate::layout::{PagebreakElem, Parity};
use crate::realize::Pair;
/// An item in page layout.
pub enum Item<'a> {
/// A page run containing content. All runs will be layouted in parallel.
Run(&'a [Pair<'a>], StyleChain<'a>, Locator<'a>),
/// Tags in between pages. These will be prepended to the first start of
/// the next page, or appended at the very end of the final page if there is
/// no next page.
Tags(&'a [Pair<'a>]),
/// An instruction to possibly add a page to bring the page number parity to
/// the desired state. Can only be done at the end, sequentially, because it
/// requires knowledge of the concrete page number.
Parity(Parity, StyleChain<'a>, Locator<'a>),
}
/// Slices up the children into logical parts, processing styles and handling
/// things like tags and weak pagebreaks.
pub fn collect<'a>(
mut children: &'a mut [Pair<'a>],
mut locator: SplitLocator<'a>,
mut initial: StyleChain<'a>,
) -> Vec<Item<'a>> {
// The collected page-level items.
let mut items: Vec<Item<'a>> = vec![];
// When this is true, an empty page should be added to `pages` at the end.
let mut staged_empty_page = true;
// The `children` are a flat list of flow-level items and pagebreaks. This
// loops splits it up into pagebreaks and consecutive slices of
// non-pagebreaks. From these pieces, we build page items that we can then
// layout in parallel.
while let Some(&(elem, styles)) = children.first() {
if let Some(pagebreak) = elem.to_packed::<PagebreakElem>() {
// Add a blank page if we encounter a strong pagebreak and there was
// a staged empty page.
let strong = !pagebreak.weak(styles);
if strong && staged_empty_page {
let locator = locator.next(&elem.span());
items.push(Item::Run(&[], initial, locator));
}
// Add an instruction to adjust the page parity if requested.
if let Some(parity) = pagebreak.to(styles) {
let locator = locator.next(&elem.span());
items.push(Item::Parity(parity, styles, locator));
}
// The initial styles for the next page are ours unless this is a
// "boundary" pagebreak. Such a pagebreak is generated at the end of
// the scope of a page set rule to ensure a page boundary. It's
// styles correspond to the styles _before_ the page set rule, so we
// don't want to apply it to a potential empty page.
if !pagebreak.boundary(styles) {
initial = styles;
}
// Stage an empty page after a strong pagebreak.
staged_empty_page |= strong;
// Advance to the next child.
children = &mut children[1..];
} else {
// Find the end of the consecutive non-pagebreak run.
let end =
children.iter().take_while(|(c, _)| !c.is::<PagebreakElem>()).count();
// Migrate start tags without accompanying end tags from before a
// pagebreak to after it.
let end = migrate_unterminated_tags(children, end);
if end == 0 {
continue;
}
// Advance to the rest of the children.
let (group, rest) = children.split_at_mut(end);
children = rest;
// If all that is left now are tags, then we don't want to add a
// page just for them (since no group would have been detected in a
// tagless layout and tags should never affect the layout). For this
// reason, we remember them in a `PageItem::Tags` and later insert
// them at the _very start_ of the next page, even before the
// header.
//
// We don't do this if all that's left is end boundary pagebreaks
// and if an empty page is still staged, since then we can just
// conceptually replace that final page with us.
if group.iter().all(|(c, _)| c.is::<TagElem>())
&& !(staged_empty_page
&& children.iter().all(|&(c, s)| {
c.to_packed::<PagebreakElem>().is_some_and(|c| c.boundary(s))
}))
{
items.push(Item::Tags(group));
continue;
}
// Record a page run and then disregard a staged empty page because
// we have real content now.
let locator = locator.next(&elem.span());
items.push(Item::Run(group, initial, locator));
staged_empty_page = false;
}
}
// Flush a staged empty page.
if staged_empty_page {
items.push(Item::Run(&[], initial, locator.next(&())));
}
items
}
/// Migrates trailing start tags without accompanying end tags tags from before
/// a pagebreak to after it. Returns the position right after the last
/// non-migrated tag.
///
/// This is important because we want the positions of introspectible elements
/// that technically started before a pagebreak, but have no visible content
/// yet, to be after the pagebreak. A typical case where this happens is `show
/// heading: it => pagebreak() + it`.
fn migrate_unterminated_tags(children: &mut [Pair], mid: usize) -> usize {
// Compute the range from before the first trailing tag to after the last
// following pagebreak.
let (before, after) = children.split_at(mid);
let start = mid - before.iter().rev().take_while(|&(c, _)| c.is::<TagElem>()).count();
let end = mid + after.iter().take_while(|&(c, _)| c.is::<PagebreakElem>()).count();
// Determine the set of tag locations which we won't migrate (because they
// are terminated).
let excluded: HashSet<_> = children[start..mid]
.iter()
.filter_map(|(c, _)| c.to_packed::<TagElem>())
.filter(|elem| elem.tag.kind() == TagKind::End)
.map(|elem| elem.tag.location())
.collect();
// A key function that partitions the area of interest into three groups:
// Excluded tags (-1) | Pagebreaks (0) | Migrated tags (1).
let key = |(c, _): &Pair| match c.to_packed::<TagElem>() {
Some(elem) => {
if excluded.contains(&elem.tag.location()) {
-1
} else {
1
}
}
None => 0,
};
// Partition the children using a *stable* sort. While it would be possible
// to write a more efficient direct algorithm for this, the sort version is
// less likely to have bugs and this is absolutely not on a hot path.
children[start..end].sort_by_key(key);
// Compute the new end index, right before the pagebreaks.
start + children[start..end].iter().take_while(|pair| key(pair) == -1).count()
}

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crates/typst/src/layout/pages/finalize.rs Normal file
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use super::LayoutedPage;
use crate::diag::SourceResult;
use crate::engine::Engine;
use crate::introspection::{ManualPageCounter, Tag};
use crate::layout::{Frame, FrameItem, Page, Point};
/// Piece together the inner page frame and the marginals. We can only do this
/// at the very end because inside/outside margins require knowledge of the
/// physical page number, which is unknown during parallel layout.
pub fn finalize(
engine: &mut Engine,
counter: &mut ManualPageCounter,
tags: &mut Vec<Tag>,
LayoutedPage {
inner,
mut margin,
binding,
two_sided,
header,
footer,
background,
foreground,
fill,
numbering,
}: LayoutedPage,
) -> SourceResult<Page> {
// If two sided, left becomes inside and right becomes outside.
// Thus, for left-bound pages, we want to swap on even pages and
// for right-bound pages, we want to swap on odd pages.
if two_sided && binding.swap(counter.physical()) {
std::mem::swap(&mut margin.left, &mut margin.right);
}
// Create a frame for the full page.
let mut frame = Frame::hard(inner.size() + margin.sum_by_axis());
// Add tags.
for tag in tags.drain(..) {
frame.push(Point::zero(), FrameItem::Tag(tag));
}
// Add the "before" marginals. The order in which we push things here is
// important as it affects the relative ordering of introspectible elements
// and thus how counters resolve.
if let Some(background) = background {
frame.push_frame(Point::zero(), background);
}
if let Some(header) = header {
frame.push_frame(Point::with_x(margin.left), header);
}
// Add the inner contents.
frame.push_frame(Point::new(margin.left, margin.top), inner);
// Add the "after" marginals.
if let Some(footer) = footer {
let y = frame.height() - footer.height();
frame.push_frame(Point::new(margin.left, y), footer);
}
if let Some(foreground) = foreground {
frame.push_frame(Point::zero(), foreground);
}
// Apply counter updates from within the page to the manual page counter.
counter.visit(engine, &frame)?;
// Get this page's number and then bump the counter for the next page.
let number = counter.logical();
counter.step();
Ok(Page { frame, fill, numbering, number })
}

152
crates/typst/src/layout/pages/mod.rs Normal file
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mod collect;
mod finalize;
mod run;
use comemo::{Tracked, TrackedMut};
use self::collect::{collect, Item};
use self::finalize::finalize;
use self::run::{layout_blank_page, layout_page_run, LayoutedPage};
use crate::diag::SourceResult;
use crate::engine::{Engine, Route, Sink, Traced};
use crate::foundations::{Content, StyleChain};
use crate::introspection::{
Introspector, Locator, ManualPageCounter, SplitLocator, TagElem,
};
use crate::layout::{FrameItem, Page, Point};
use crate::model::{Document, DocumentInfo};
use crate::realize::{realize, Arenas, Pair, RealizationKind};
use crate::World;
/// Layout content into a document.
///
/// This first performs root-level realization and then lays out the resulting
/// elements. In contrast to [`layout_fragment`](crate::layout::layout_fragment),
/// this does not take regions since the regions are defined by the page
/// configuration in the content and style chain.
#[typst_macros::time(name = "document")]
pub fn layout_document(
engine: &mut Engine,
content: &Content,
styles: StyleChain,
) -> SourceResult<Document> {
layout_document_impl(
engine.world,
engine.introspector,
engine.traced,
TrackedMut::reborrow_mut(&mut engine.sink),
engine.route.track(),
content,
styles,
)
}
/// The internal implementation of `layout_document`.
#[comemo::memoize]
fn layout_document_impl(
world: Tracked<dyn World + '_>,
introspector: Tracked<Introspector>,
traced: Tracked<Traced>,
sink: TrackedMut<Sink>,
route: Tracked<Route>,
content: &Content,
styles: StyleChain,
) -> SourceResult<Document> {
let mut locator = Locator::root().split();
let mut engine = Engine {
world,
introspector,
traced,
sink,
route: Route::extend(route).unnested(),
};
// Mark the external styles as "outside" so that they are valid at the page
// level.
let styles = styles.to_map().outside();
let styles = StyleChain::new(&styles);
let arenas = Arenas::default();
let mut info = DocumentInfo::default();
let mut children = realize(
RealizationKind::Root(&mut info),
&mut engine,
&mut locator,
&arenas,
content,
styles,
)?;
let pages = layout_pages(&mut engine, &mut children, locator, styles)?;
Ok(Document { pages, info, introspector: Introspector::default() })
}
/// Layouts the document's pages.
fn layout_pages<'a>(
engine: &mut Engine,
children: &'a mut [Pair<'a>],
locator: SplitLocator<'a>,
styles: StyleChain<'a>,
) -> SourceResult<Vec<Page>> {
// Slice up the children into logical parts.
let items = collect(children, locator, styles);
// Layout the page runs in parallel.
let mut runs = engine.parallelize(
items.iter().filter_map(|item| match item {
Item::Run(children, initial, locator) => {
Some((children, initial, locator.relayout()))
}
_ => None,
}),
|engine, (children, initial, locator)| {
layout_page_run(engine, children, locator, *initial)
},
);
let mut pages = vec![];
let mut tags = vec![];
let mut counter = ManualPageCounter::new();
// Collect and finalize the runs, handling things like page parity and tags
// between pages.
for item in &items {
match item {
Item::Run(..) => {
let layouted = runs.next().unwrap()?;
for layouted in layouted {
let page = finalize(engine, &mut counter, &mut tags, layouted)?;
pages.push(page);
}
}
Item::Parity(parity, initial, locator) => {
if !parity.matches(pages.len()) {
continue;
}
let layouted = layout_blank_page(engine, locator.relayout(), *initial)?;
let page = finalize(engine, &mut counter, &mut tags, layouted)?;
pages.push(page);
}
Item::Tags(items) => {
tags.extend(
items
.iter()
.filter_map(|(c, _)| c.to_packed::<TagElem>())
.map(|elem| elem.tag.clone()),
);
}
}
}
// Add the remaining tags to the very end of the last page.
if !tags.is_empty() {
let last = pages.last_mut().unwrap();
let pos = Point::with_y(last.frame.height());
last.frame
.push_multiple(tags.into_iter().map(|tag| (pos, FrameItem::Tag(tag))));
}
Ok(pages)
}

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crates/typst/src/layout/pages/run.rs Normal file
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use comemo::{Track, Tracked, TrackedMut};
use crate::diag::SourceResult;
use crate::engine::{Engine, Route, Sink, Traced};
use crate::foundations::{Content, NativeElement, Resolve, Smart, StyleChain, Styles};
use crate::introspection::{
Counter, CounterDisplayElem, CounterKey, Introspector, Locator, LocatorLink, TagElem,
};
use crate::layout::{
layout_flow, layout_frame, Abs, AlignElem, Alignment, Axes, Binding, ColumnsElem,
Dir, Frame, HAlignment, Length, OuterVAlignment, PageElem, Paper, Region, Regions,
Rel, Sides, Size, VAlignment,
};
use crate::model::Numbering;
use crate::realize::Pair;
use crate::syntax::Span;
use crate::text::TextElem;
use crate::utils::Numeric;
use crate::visualize::Paint;
use crate::World;
/// A mostly finished layout for one page. Needs only knowledge of its exact
/// page number to be finalized into a `Page`. (Because the margins can depend
/// on the page number.)
#[derive(Clone)]
pub struct LayoutedPage {
pub inner: Frame,
pub margin: Sides<Abs>,
pub binding: Binding,
pub two_sided: bool,
pub header: Option<Frame>,
pub footer: Option<Frame>,
pub background: Option<Frame>,
pub foreground: Option<Frame>,
pub fill: Smart<Option<Paint>>,
pub numbering: Option<Numbering>,
}
/// Layout a single page suitable for parity adjustment.
pub fn layout_blank_page(
engine: &mut Engine,
locator: Locator,
initial: StyleChain,
) -> SourceResult<LayoutedPage> {
let layouted = layout_page_run(engine, &[], locator, initial)?;
Ok(layouted.into_iter().next().unwrap())
}
/// Layout a page run with uniform properties.
#[typst_macros::time(name = "page run")]
pub fn layout_page_run(
engine: &mut Engine,
children: &[Pair],
locator: Locator,
initial: StyleChain,
) -> SourceResult<Vec<LayoutedPage>> {
layout_page_run_impl(
engine.world,
engine.introspector,
engine.traced,
TrackedMut::reborrow_mut(&mut engine.sink),
engine.route.track(),
children,
locator.track(),
initial,
)
}
/// The internal implementation of `layout_page_run`.
#[comemo::memoize]
#[allow(clippy::too_many_arguments)]
fn layout_page_run_impl(
world: Tracked<dyn World + '_>,
introspector: Tracked<Introspector>,
traced: Tracked<Traced>,
sink: TrackedMut<Sink>,
route: Tracked<Route>,
children: &[Pair],
locator: Tracked<Locator>,
initial: StyleChain,
) -> SourceResult<Vec<LayoutedPage>> {
let link = LocatorLink::new(locator);
let mut locator = Locator::link(&link).split();
let mut engine = Engine {
world,
introspector,
traced,
sink,
route: Route::extend(route),
};
// Determine the page-wide styles.
let styles = determine_page_styles(children, initial);
let styles = StyleChain::new(&styles);
// When one of the lengths is infinite the page fits its content along
// that axis.
let width = PageElem::width_in(styles).unwrap_or(Abs::inf());
let height = PageElem::height_in(styles).unwrap_or(Abs::inf());
let mut size = Size::new(width, height);
if PageElem::flipped_in(styles) {
std::mem::swap(&mut size.x, &mut size.y);
}
let mut min = width.min(height);
if !min.is_finite() {
min = Paper::A4.width();
}
// Determine the margins.
let default = Rel::<Length>::from((2.5 / 21.0) * min);
let margin = PageElem::margin_in(styles);
let two_sided = margin.two_sided.unwrap_or(false);
let margin = margin
.sides
.map(|side| side.and_then(Smart::custom).unwrap_or(default))
.resolve(styles)
.relative_to(size);
// Realize columns.
let area = size - margin.sum_by_axis();
let mut regions = Regions::repeat(area, area.map(Abs::is_finite));
regions.root = true;
let fill = PageElem::fill_in(styles);
let foreground = PageElem::foreground_in(styles);
let background = PageElem::background_in(styles);
let header_ascent = PageElem::header_ascent_in(styles).relative_to(margin.top);
let footer_descent = PageElem::footer_descent_in(styles).relative_to(margin.bottom);
let numbering = PageElem::numbering_in(styles);
let number_align = PageElem::number_align_in(styles);
let binding =
PageElem::binding_in(styles).unwrap_or_else(|| match TextElem::dir_in(styles) {
Dir::LTR => Binding::Left,
_ => Binding::Right,
});
// Construct the numbering (for header or footer).
let numbering_marginal = numbering.as_ref().map(|numbering| {
let both = match numbering {
Numbering::Pattern(pattern) => pattern.pieces() >= 2,
Numbering::Func(_) => true,
};
let mut counter = CounterDisplayElem::new(
Counter::new(CounterKey::Page),
Smart::Custom(numbering.clone()),
both,
)
.pack();
// We interpret the Y alignment as selecting header or footer
// and then ignore it for aligning the actual number.
if let Some(x) = number_align.x() {
counter = counter.aligned(x.into());
}
counter
});
let header = PageElem::header_in(styles);
let footer = PageElem::footer_in(styles);
let (header, footer) = if matches!(number_align.y(), Some(OuterVAlignment::Top)) {
(header.as_ref().unwrap_or(&numbering_marginal), footer.as_ref().unwrap_or(&None))
} else {
(header.as_ref().unwrap_or(&None), footer.as_ref().unwrap_or(&numbering_marginal))
};
// Layout the children.
let bump = bumpalo::Bump::new();
let fragment = layout_flow(
&mut engine,
&bump,
children,
&mut locator,
styles,
regions,
PageElem::columns_in(styles),
ColumnsElem::gutter_in(styles),
Span::detached(),
)?;
// Layouts a single marginal.
let mut layout_marginal = |content: &Option<Content>, area, align| {
let Some(content) = content else { return Ok(None) };
let aligned = content.clone().styled(AlignElem::set_alignment(align));
layout_frame(
&mut engine,
&aligned,
locator.next(&content.span()),
styles,
Region::new(area, Axes::splat(true)),
)
.map(Some)
};
// Layout marginals.
let mut layouted = Vec::with_capacity(fragment.len());
for inner in fragment {
let header_size = Size::new(inner.width(), margin.top - header_ascent);
let footer_size = Size::new(inner.width(), margin.bottom - footer_descent);
let full_size = inner.size() + margin.sum_by_axis();
let mid = HAlignment::Center + VAlignment::Horizon;
layouted.push(LayoutedPage {
inner,
fill: fill.clone(),
numbering: numbering.clone(),
header: layout_marginal(header, header_size, Alignment::BOTTOM)?,
footer: layout_marginal(footer, footer_size, Alignment::TOP)?,
background: layout_marginal(background, full_size, mid)?,
foreground: layout_marginal(foreground, full_size, mid)?,
margin,
binding,
two_sided,
});
}
Ok(layouted)
}
/// Determines the styles used for a page run itself and page-level content like
/// marginals and footnotes.
///
/// As a base, we collect the styles that are shared by all elements on the page
/// run. As a fallback if there are no elements, we use the styles active at the
/// pagebreak that introduced the page (at the very start, we use the default
/// styles). Then, to produce our page styles, we filter this list of styles
/// according to a few rules:
///
/// - Other styles are only kept if they are `outside && (initial || liftable)`.
/// - "Outside" means they were not produced within a show rule or that the
/// show rule "broke free" to the page level by emitting page styles.
/// - "Initial" means they were active at the pagebreak that introduced the
/// page. Since these are intuitively already active, they should be kept even
/// if not liftable. (E.g. `text(red, page(..)`) makes the footer red.)
/// - "Liftable" means they can be lifted to the page-level even though they
/// weren't yet active at the very beginning. Set rule styles are liftable as
/// opposed to direct constructor calls:
/// - For `set page(..); set text(red)` the red text is kept even though it
/// comes after the weak pagebreak from set page.
/// - For `set page(..); text(red)[..]` the red isn't kept because the
/// constructor styles are not liftable.
fn determine_page_styles(children: &[Pair], initial: StyleChain) -> Styles {
// Determine the shared styles (excluding tags).
let tagless = children.iter().filter(|(c, _)| !c.is::<TagElem>()).map(|&(_, s)| s);
let base = StyleChain::trunk(tagless).unwrap_or(initial).to_map();
// Determine the initial styles that are also shared by everything. We can't
// use `StyleChain::trunk` because it currently doesn't deal with partially
// shared links (where a subslice matches).
let trunk_len = initial
.to_map()
.as_slice()
.iter()
.zip(base.as_slice())
.take_while(|&(a, b)| a == b)
.count();
// Filter the base styles according to our rules.
base.into_iter()
.enumerate()
.filter(|(i, style)| {
let initial = *i < trunk_len;
style.outside() && (initial || style.liftable())
})
.map(|(_, style)| style)
.collect()
}