From fc5858c98256b32eca798a0df1bf96f426416bd2 Mon Sep 17 00:00:00 2001
From: Laurenz <laurmaedje@gmail.com>
Date: Tue, 8 Oct 2024 15:13:14 +0200
Subject: [PATCH] Allow sticky blocks to be breakable (#5161)

---
 crates/typst/src/layout/container.rs       |   2 --
 crates/typst/src/layout/flow/collect.rs    |   4 +++-
 crates/typst/src/layout/flow/distribute.rs |   8 ++++----
 tests/ref/block-sticky-breakable.png       | Bin 0 -> 405 bytes
 tests/suite/layout/container.typ           |   6 ++++++
 5 files changed, 13 insertions(+), 7 deletions(-)
 create mode 100644 tests/ref/block-sticky-breakable.png

diff --git a/crates/typst/src/layout/container.rs b/crates/typst/src/layout/container.rs
index 996ef6c99..9fdef0be4 100644
--- a/crates/typst/src/layout/container.rs
+++ b/crates/typst/src/layout/container.rs
@@ -422,8 +422,6 @@ pub struct BlockElem {
     /// This is, by default, set on heading blocks to prevent orphaned headings
     /// at the bottom of the page.
     ///
-    /// Marking a block as sticky makes it unbreakable.
-    ///
     /// ```example
     /// >>> #set page(height: 140pt)
     /// // Disable stickiness of headings.
diff --git a/crates/typst/src/layout/flow/collect.rs b/crates/typst/src/layout/flow/collect.rs
index 9fc64f067..a477c3347 100644
--- a/crates/typst/src/layout/flow/collect.rs
+++ b/crates/typst/src/layout/flow/collect.rs
@@ -189,7 +189,7 @@ impl<'a> Collector<'a, '_, '_> {
 
         self.output.push(spacing(elem.above(styles)));
 
-        if !breakable || sticky || fr.is_some() {
+        if !breakable || fr.is_some() {
             self.output.push(Child::Single(self.boxed(SingleChild {
                 align,
                 sticky,
@@ -203,6 +203,7 @@ impl<'a> Collector<'a, '_, '_> {
             let alone = self.children.len() == 1;
             self.output.push(Child::Multi(self.boxed(MultiChild {
                 align,
+                sticky,
                 alone,
                 elem,
                 styles,
@@ -375,6 +376,7 @@ fn layout_single_impl(
 #[derive(Debug)]
 pub struct MultiChild<'a> {
     pub align: Axes<FixedAlignment>,
+    pub sticky: bool,
     alone: bool,
     elem: &'a Packed<BlockElem>,
     styles: StyleChain<'a>,
diff --git a/crates/typst/src/layout/flow/distribute.rs b/crates/typst/src/layout/flow/distribute.rs
index 65516ccd8..a30b71bac 100644
--- a/crates/typst/src/layout/flow/distribute.rs
+++ b/crates/typst/src/layout/flow/distribute.rs
@@ -247,7 +247,7 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
 
         // Lay out the block.
         let (frame, spill) = multi.layout(self.composer.engine, self.regions)?;
-        self.frame(frame, multi.align, false, true)?;
+        self.frame(frame, multi.align, multi.sticky, true)?;
 
         // If the block didn't fully fit into the current region, save it into
         // the `spill` and finish the region.
@@ -292,9 +292,9 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
         breakable: bool,
     ) -> FlowResult<()> {
         if sticky {
-            // If the frame is sticky and we haven't remember a preceding sticky
-            // element, make a checkpoint which we can restore should we end on
-            // this sticky element.
+            // If the frame is sticky and we haven't remembered a preceding
+            // sticky element, make a checkpoint which we can restore should we
+            // end on this sticky element.
             if self.stickable && self.sticky.is_none() {
                 self.sticky = Some(self.snapshot());
             }
diff --git a/tests/ref/block-sticky-breakable.png b/tests/ref/block-sticky-breakable.png
new file mode 100644
index 0000000000000000000000000000000000000000..91287a7e67a25882fb9b7957b026a60404d5aa09
GIT binary patch
literal 405
zcmeAS@N?(olHy`uVBq!ia0vp^6+m3c0VEi%2k%<Vz`z*e>EaktaqI1scx~rGnd2XA
z87dj{1jNgZ%I+?Dd+z9|Q+u7Pe+KJKxiaarC*SNT^{bOz&rapm^-AxxTDomg(POX6
ze5tNH&ueTrUe|2<RWtv<>ih45-wSw%3+Y5`cyR21awy*$pP4cik<!Z!ynAx>0W-6o
z*!!T<EI*RPe!Tk6DR(cXs4!VZL!pWFzx+0(-`UrBBy20>792=?Uow@cJla^e^i+4_
z4^GB!)(nq(7}ArY-KTSPBphsF<rV{40A{2eT66grP#`b&huKEqc$EWJSFlU4RMd($
z_&4+>Upn@ZRp^hD=AqL+4<4?#ZEXA=q@TB8?ZUTHznC++=}+kYC-lIe;U%}wo{0(v
zi+?^y+|OMhrJ6IRcd1dDFQXvHA8Bo;`ySgEJqU_^STm1NnP<IIqc#6=d(DFR(^pU4
xCzaRAaDV&sQ_1=)H#X+(UQomdbX&pagY}9FFJ^9S|C9p?Z%<c0mvv4FO#t52u3P{B

literal 0
HcmV?d00001

diff --git a/tests/suite/layout/container.typ b/tests/suite/layout/container.typ
index d054175a2..e13679675 100644
--- a/tests/suite/layout/container.typ
+++ b/tests/suite/layout/container.typ
@@ -180,6 +180,12 @@ A
 #colbreak()
 C
 
+--- block-sticky-breakable ---
+// Ensure that sticky blocks are still breakable.
+#set page(height: 60pt)
+#block(sticky: true, lines(4))
+E
+
 --- box-clip-rect ---
 // Test box clipping with a rectangle
 Hello #box(width: 1em, height: 1em, clip: false)[#rect(width: 3em, height: 3em, fill: red)]