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-rw-r--r--crates/typst-layout/src/flow/compose.rs38
1 files changed, 33 insertions, 5 deletions
diff --git a/crates/typst-layout/src/flow/compose.rs b/crates/typst-layout/src/flow/compose.rs
index 32645675..3cf66f9e 100644
--- a/crates/typst-layout/src/flow/compose.rs
+++ b/crates/typst-layout/src/flow/compose.rs
@@ -15,7 +15,7 @@ use typst_library::model::{
FootnoteElem, FootnoteEntry, LineNumberingScope, Numbering, ParLineMarker,
};
use typst_syntax::Span;
-use typst_utils::NonZeroExt;
+use typst_utils::{NonZeroExt, Numeric};
use super::{distribute, Config, FlowResult, LineNumberConfig, PlacedChild, Stop, Work};
@@ -374,7 +374,11 @@ impl<'a, 'b> Composer<'a, 'b, '_, '_> {
let mut relayout = false;
let mut regions = *regions;
- let mut migratable = migratable && !breakable && regions.may_progress();
+
+ // The first footnote's origin frame should be migratable if the region
+ // may progress (already checked by the footnote function) and if the
+ // origin frame isn't breakable (checked here).
+ let mut migratable = migratable && !breakable;
for (y, elem) in notes {
// The amount of space used by the in-flow content that contains the
@@ -464,11 +468,35 @@ impl<'a, 'b> Composer<'a, 'b, '_, '_> {
// If the first frame is empty, then none of its content fit. If
// possible, we then migrate the origin frame to the next region to
// uphold the footnote invariant (that marker and entry are on the same
- // page). If not, we just queue the footnote for the next page.
+ // page). If not, we just queue the footnote for the next page, but
+ // only if that would actually make a difference (that is, if the
+ // footnote isn't alone in the page after not fitting in any previous
+ // pages, as it probably won't ever fit then).
+ //
+ // Note that a non-zero flow need also indicates that queueing would
+ // make a difference, because the flow need is subtracted from the
+ // available height in the entry's pod even if what caused that need
+ // wasn't considered for the input `regions`. For example, floats just
+ // pass the `regions` they received along to their footnotes, which
+ // don't take into account the space occupied by the floats themselves,
+ // but they do indicate their footnotes have a non-zero flow need, so
+ // queueing them can matter as, in the following pages, the flow need
+ // will be set to zero and the footnote will be alone in the page.
+ // Then, `may_progress()` will also be false (this time, correctly) and
+ // the footnote is laid out, as queueing wouldn't improve the lack of
+ // space anymore and would result in an infinite loop.
+ //
+ // However, it is worth noting that migration does take into account
+ // the original region, before inserting what prompted the flow need.
+ // Logically, if moving the original frame can't improve the lack of
+ // space, then migration should be inhibited. The space occupied by the
+ // original frame is not relevant for that check. Therefore,
+ // `regions.may_progress()` must still be checked separately for
+ // migration, regardless of the presence of flow need.
if first.is_empty() && exist_non_empty_frame {
- if migratable {
+ if migratable && regions.may_progress() {
return Err(Stop::Finish(false));
- } else {
+ } else if regions.may_progress() || !flow_need.is_zero() {
self.footnote_queue.push(elem);
return Ok(());
}