Merge 23ef479a730057529773eb8190805e5c48169a84 into 9b09146a6b5e936966ed7ee73bce9dd2df3810ae

crates/typst-layout/src/flow/collect.rs

@@ -14,7 +14,7 @@ use typst_library::introspection::{
 use typst_library::layout::{
     Abs, AlignElem, Alignment, Axes, BlockElem, ColbreakElem, FixedAlignment, FlushElem,
     Fr, Fragment, Frame, PagebreakElem, PlaceElem, PlacementScope, Ratio, Region,
-    Regions, Rel, Size, Sizing, Spacing, VElem,
+    Regions, Rel, Size, Sizing, Spacing, Sticky, VElem,
 };
 use typst_library::model::ParElem;
 use typst_library::routines::{Pair, Routines};
@@ -375,7 +375,7 @@ pub struct LineChild {
 #[derive(Debug)]
 pub struct SingleChild<'a> {
     pub align: Axes<FixedAlignment>,
-    pub sticky: bool,
+    pub sticky: Option<Sticky>,
     pub alone: bool,
     pub fr: Option<Fr>,
     elem: &'a Packed<BlockElem>,
@@ -441,7 +441,7 @@ fn layout_single_impl(
 #[derive(Debug)]
 pub struct MultiChild<'a> {
     pub align: Axes<FixedAlignment>,
-    pub sticky: bool,
+    pub sticky: Option<Sticky>,
     alone: bool,
     elem: &'a Packed<BlockElem>,
     styles: StyleChain<'a>,

crates/typst-layout/src/flow/distribute.rs

@@ -1,6 +1,7 @@
 use typst_library::introspection::Tag;
 use typst_library::layout::{
     Abs, Axes, FixedAlignment, Fr, Frame, FrameItem, Point, Region, Regions, Rel, Size,
+    Sticky,
 };
 use typst_utils::Numeric;
 
@@ -244,7 +245,7 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
             return Err(Stop::Finish(false));
         }
 
-        self.frame(line.frame.clone(), line.align, false, false)
+        self.frame(line.frame.clone(), line.align, None, false)
     }
 
     /// Processes an unbreakable block.
@@ -307,7 +308,7 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
         // Lay out the spilled remains.
         let align = spill.align();
         let (frame, spill) = spill.layout(self.composer.engine, self.regions)?;
-        self.frame(frame, align, false, true)?;
+        self.frame(frame, align, None, true)?;
 
         // If there's still more, save it into the `spill` and finish the
         // region.
@@ -324,10 +325,28 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
         &mut self,
         frame: Frame,
         align: Axes<FixedAlignment>,
-        sticky: bool,
+        sticky: Option<Sticky>,
         breakable: bool,
     ) -> FlowResult<()> {
-        if sticky {
+        // Check if the successor frame has sticky: above
+        let has_sticky_successor = self
+            .composer
+            .work
+            .children
+            .iter()
+            .skip(1)
+            .find_map(|child| match child {
+                Child::Single(single) => Some(
+                    single.sticky.as_ref().map(|s| s.is_sticky_above()).unwrap_or(false),
+                ),
+                Child::Multi(multi) => Some(
+                    multi.sticky.as_ref().map(|s| s.is_sticky_above()).unwrap_or(false),
+                ),
+                _ => None,
+            })
+            .unwrap_or(false);
+
+        let mut stick_to_successor = || {
             // 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.
@@ -350,12 +369,22 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
             {
                 self.sticky = Some(self.snapshot());
             }
-        } else if !frame.is_empty() {
-            // If the frame isn't sticky, we can forget a previous snapshot. We
-            // interrupt a group of sticky blocks, if there was one, so we reset
-            // the saved stickable check for the next group of sticky blocks.
-            self.sticky = None;
-            self.stickable = None;
+        };
+
+        match sticky {
+            Some(Sticky::Below) => {
+                stick_to_successor();
+            }
+            _ if has_sticky_successor => {
+                stick_to_successor();
+            }
+            _ => {
+                // Only clear the snapshot if this frame isn't empty
+                if !frame.is_empty() {
+                    self.sticky = None;
+                    self.stickable = None;
+                }
+            }
         }
 
         // Handle footnotes.
@@ -443,7 +472,13 @@ impl<'a, 'b> Distributor<'a, 'b, '_, '_, '_> {
             // the flow, restore the saved checkpoint to move the sticky
             // suffix to the next region.
             if let Some(snapshot) = self.sticky.take() {
-                self.restore(snapshot)
+                // Only restore snapshot if there's no spill
+                // If a sticky breakable element can be spilled to the following page,
+                // it's fine to put some of it on this page, since the next page will still
+                // have the next element on the same page as *some* of the spilled content.
+                if self.composer.work.spill.is_none() {
+                    self.restore(snapshot)
+                }
             }
         }
 

crates/typst-library/src/layout/container.rs

@@ -1,7 +1,7 @@
 use crate::diag::{bail, SourceResult};
 use crate::engine::Engine;
 use crate::foundations::{
-    cast, elem, Args, AutoValue, Construct, Content, NativeElement, Packed, Smart,
+    cast, elem, Args, AutoValue, Cast, Construct, Content, NativeElement, Packed, Smart,
     StyleChain, Value,
 };
 use crate::introspection::Locator;
@@ -179,6 +179,27 @@ pub enum InlineItem {
     Frame(Frame),
 }
 
+/// Defines how a block sticks to adjacent content.
+#[derive(Debug, Cast, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum Sticky {
+    /// Block sticks to the content below it.
+    Below,
+    /// Makes the block above stick to this block.
+    Above,
+    /// Makes the block above and below stick to this block.
+    Both,
+}
+
+impl Sticky {
+    pub fn is_sticky_above(self) -> bool {
+        matches!(self, Self::Above | Self::Both)
+    }
+
+    pub fn is_sticky_below(self) -> bool {
+        matches!(self, Self::Below | Self::Both)
+    }
+}
+
 /// A block-level container.
 ///
 /// Such a container can be used to separate content, size it, and give it a
@@ -338,23 +359,29 @@ pub struct BlockElem {
     #[default(false)]
     pub clip: bool,
 
-    /// Whether this block must stick to the following one, with no break in
-    /// between.
+    /// If and how this block must stick to the blocks surrounding it, with no
+    /// break in between.
     ///
-    /// This is, by default, set on heading blocks to prevent orphaned headings
-    /// at the bottom of the page.
+    /// This is, by default, set to "below" on heading blocks to prevent
+    /// orphaned headings at the bottom of the page.
     ///
     /// ```example
     /// >>> #set page(height: 140pt)
     /// // Disable stickiness of headings.
-    /// #show heading: set block(sticky: false)
+    /// #show heading: set block(sticky: none)
     /// #lorem(20)
     ///
     /// = Chapter
     /// #lorem(10)
+    ///
+    /// #table(
+    /// columns: 2,
+    /// [A], [B],
+    /// [C], [D],
+    /// )
+    /// #block(sticky: "above")[The above table shows that...]
     /// ```
-    #[default(false)]
-    pub sticky: bool,
+    pub sticky: Option<Sticky>,
 
     /// The contents of the block.
     #[positional]

crates/typst-library/src/model/heading.rs

@@ -13,7 +13,9 @@ use crate::html::{attr, tag, HtmlElem};
 use crate::introspection::{
     Count, Counter, CounterUpdate, Locatable, Locator, LocatorLink,
 };
-use crate::layout::{Abs, Axes, BlockBody, BlockElem, Em, HElem, Length, Region, Sides};
+use crate::layout::{
+    Abs, Axes, BlockBody, BlockElem, Em, HElem, Length, Region, Sides, Sticky,
+};
 use crate::model::{Numbering, Outlinable, Refable, Supplement};
 use crate::text::{FontWeight, LocalName, SpaceElem, TextElem, TextSize};
 
@@ -323,7 +325,7 @@ impl ShowSet for Packed<HeadingElem> {
         out.set(TextElem::set_weight(FontWeight::BOLD));
         out.set(BlockElem::set_above(Smart::Custom(above.into())));
         out.set(BlockElem::set_below(Smart::Custom(below.into())));
-        out.set(BlockElem::set_sticky(true));
+        out.set(BlockElem::set_sticky(Some(Sticky::Below)));
         out
     }
 }

tests/suite/layout/container.typ

@@ -155,17 +155,17 @@ Paragraph
 --- block-sticky ---
 #set page(height: 100pt)
 #lines(3)
-#block(sticky: true)[D]
-#block(sticky: true)[E]
+#block(sticky: "below")[D]
+#block(sticky: "below")[E]
 F
 
 --- block-sticky-alone ---
 #set page(height: 50pt)
-#block(sticky: true)[A]
+#block(sticky: "below")[A]
 
 --- block-sticky-many ---
 #set page(height: 80pt)
-#set block(sticky: true)
+#set block(breakable: false, sticky: "below")
 #block[A]
 #block[B]
 #block[C]
@@ -176,16 +176,22 @@ E
 
 --- block-sticky-colbreak ---
 A
-#block(sticky: true)[B]
+#block(sticky: "below")[B]
 #colbreak()
 C
 
 --- block-sticky-breakable ---
 // Ensure that sticky blocks are still breakable.
 #set page(height: 60pt)
-#block(sticky: true, lines(4))
+#block(sticky: "below", lines(4))
 E
 
+--- block-sticky-above ---
+#set page(height: 50pt)
+#block(height: 15pt)[A]
+#block(height: 5pt, breakable: false)[B]
+#block(height: 5pt, sticky: "above")[C]
+
 --- box-clip-rect ---
 // Test box clipping with a rectangle
 Hello #box(width: 1em, height: 1em, clip: false)[#rect(width: 3em, height: 3em, fill: red)]
@@ -291,7 +297,7 @@ Paragraph
 #set page(height: 3cm)
 #v(1.6cm)
 #block(height: 2cm, breakable: true)[
-  #block(sticky: true)[*A*]
+  #block(sticky: "below")[*A*]
 
   b
 ]
@@ -300,7 +306,7 @@ Paragraph
 #set page(height: 3cm)
 #v(2cm)
 
-#block(sticky: true)[*A*]
+#block(sticky: "below")[*A*]
 
 b
 
@@ -308,7 +314,7 @@ b
 #set page(height: 3cm)
 #v(2cm, weak: true)
 
-#block(sticky: true)[*A*]
+#block(sticky: "below")[*A*]
 
 b