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ensure short-lived headers also replace predecessors

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Even if they don't repeat, they should cause previous headers to stop repeating.
This commit is contained in:
PgBiel 2025-05-20 21:57:34 -03:00
parent 302e93fb4b
commit 6e6f21f78b
3 changed files with 104 additions and 63 deletions
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114
crates/typst-layout/src/grid/repeated.rs
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@ -49,6 +49,33 @@ impl<'a> GridLayouter<'a> {
self.upcoming_headers = new_upcoming_headers;
*consecutive_header_count = 0;
let [first_header, ..] = consecutive_headers else {
self.flush_orphans();
return Ok(());
};
// Assuming non-conflicting headers sorted by increasing y, this must
// be the header with the lowest level (sorted by increasing levels).
let first_level = first_header.level;
// Stop repeating conflicting headers, even if the new headers are
// short-lived or won't repeat.
//
// If we go to a new region before the new headers fit alongside their
// children (or in general, for short-lived), the old headers should
// not be displayed anymore.
let first_conflicting_pos =
self.repeating_headers.partition_point(|h| h.level < first_level);
self.repeating_headers.truncate(first_conflicting_pos);
// Ensure upcoming rows won't see that these headers will occupy any
// space in future regions anymore.
for removed_height in
self.current.repeating_header_heights.drain(first_conflicting_pos..)
{
self.current.repeating_header_height -= removed_height;
}
// Layout short-lived headers immediately.
if consecutive_headers.last().is_some_and(|h| h.short_lived) {
// No chance of orphans as we're immediately placing conflicting
@ -63,11 +90,32 @@ impl<'a> GridLayouter<'a> {
// header of the same or lower level, such that they never actually get
// to repeat.
self.layout_new_headers(consecutive_headers, true, engine)?;
Ok(())
} else {
self.layout_new_pending_headers(consecutive_headers, engine)
// Let's try to place pending headers at least once.
// This might be a waste as we could generate an orphan and thus have
// to try to place old and new headers all over again, but that happens
// for every new region anyway, so it's rather unavoidable.
let snapshot_created =
self.layout_new_headers(consecutive_headers, false, engine)?;
// Queue the new headers for layout. They will remain in this
// vector due to orphan prevention.
//
// After the first subsequent row is laid out, move to repeating, as
// it's then confirmed the headers won't be moved due to orphan
// prevention anymore.
self.pending_headers = consecutive_headers;
if !snapshot_created {
// Region probably couldn't progress.
//
// Mark new pending headers as final and ensure there isn't a
// snapshot.
self.flush_orphans();
}
}
Ok(())
}
/// Lays out rows belonging to a header, returning the calculated header
@ -100,66 +148,6 @@ impl<'a> GridLayouter<'a> {
Ok(header_height)
}
/// Queues new pending headers for layout. Headers remain pending until
/// they are successfully laid out in some page once. Then, they will be
/// moved to `repeating_headers`, at which point it is safe to stop them
/// from repeating at any time.
fn layout_new_pending_headers(
&mut self,
headers: &'a [Repeatable<Header>],
engine: &mut Engine,
) -> SourceResult<()> {
let [first_header, ..] = headers else {
return Ok(());
};
// Should be impossible to have two consecutive chunks of pending
// headers since they are always as long as possible, only being
// interrupted by direct conflict between consecutive headers, in which
// case we flush pending headers immediately.
assert!(self.pending_headers.is_empty());
// Assuming non-conflicting headers sorted by increasing y, this must
// be the header with the lowest level (sorted by increasing levels).
let first_level = first_header.level;
// Stop repeating conflicting headers.
// If we go to a new region before the pending headers fit alongside
// their children, the old headers should not be displayed anymore.
let first_conflicting_pos =
self.repeating_headers.partition_point(|h| h.level < first_level);
self.repeating_headers.truncate(first_conflicting_pos);
// Ensure upcoming rows won't see that these headers will occupy any
// space in future regions anymore.
for removed_height in
self.current.repeating_header_heights.drain(first_conflicting_pos..)
{
self.current.repeating_header_height -= removed_height;
}
// Let's try to place them at least once.
// This might be a waste as we could generate an orphan and thus have
// to try to place old and new headers all over again, but that happens
// for every new region anyway, so it's rather unavoidable.
let snapshot_created = self.layout_new_headers(headers, false, engine)?;
// After the first subsequent row is laid out, move to repeating, as
// it's then confirmed the headers won't be moved due to orphan
// prevention anymore.
self.pending_headers = headers;
if !snapshot_created {
// Region probably couldn't progress.
//
// Mark new pending headers as final and ensure there isn't a
// snapshot.
self.flush_orphans();
}
Ok(())
}
/// This function should be called each time an additional row has been
/// laid out in a region to indicate that orphan prevention has succeeded.
///

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tests/ref/grid-subheaders-repeat-short-lived-also-replaces.png Normal file
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53
tests/suite/layout/grid/subheaders.typ
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@ -389,6 +389,59 @@
..([z],) * 10,
)
--- grid-subheaders-repeat-short-lived-also-replaces ---
// Short-lived subheaders must still replace their conflicting predecessors.
#set page(height: 8em)
#grid(
// This has to go
grid.header(
[a],
level: 3,
),
[w],
grid.header(
level: 2,
[b]
),
grid.header(
level: 2,
[c]
),
grid.header(
level: 2,
[d]
),
grid.header(
level: 2,
[e]
),
grid.header(
level: 2,
[f]
),
grid.header(
level: 2,
[g]
),
grid.header(
level: 2,
[h]
),
grid.header(
level: 2,
[i]
),
grid.header(
level: 2,
[j]
),
grid.header(
level: 3,
[k]
),
..([z],) * 10,
)
--- grid-subheaders-multi-page-row ---
#set page(height: 8em)
#grid(