Copyable regions

library/src/basics/list.rs

@@ -81,7 +81,7 @@ impl<const L: ListKind> Layout for ListNode<L> {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut cells = vec![];
         let mut number = NonZeroUsize::new(1).unwrap();

library/src/basics/table.rs

@@ -55,7 +55,7 @@ impl Layout for TableNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let fill = styles.get(Self::FILL);
         let stroke = styles.get(Self::STROKE).map(PartialStroke::unwrap_or_default);

library/src/layout/align.rs

@@ -31,7 +31,7 @@ impl Layout for AlignNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         // The child only needs to expand along an axis if there's no alignment.
         let mut pod = regions.clone();
@@ -44,7 +44,7 @@ impl Layout for AlignNode {
         }
 
         // Layout the child.
-        let mut fragment = self.child.layout(vt, styles.chain(&map), &pod)?;
+        let mut fragment = self.child.layout(vt, styles.chain(&map), pod)?;
         for (region, frame) in regions.iter().zip(&mut fragment) {
             // Align in the target size. The target size depends on whether we
             // should expand.

library/src/layout/columns.rs

@@ -31,7 +31,7 @@ impl Layout for ColumnsNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         // Separating the infinite space into infinite columns does not make
         // much sense.
@@ -44,21 +44,23 @@ impl Layout for ColumnsNode {
         let gutter = styles.get(Self::GUTTER).relative_to(regions.base.x);
         let width = (regions.first.x - gutter * (columns - 1) as f64) / columns as f64;
 
+        let backlog: Vec<_> = std::iter::once(&regions.first.y)
+            .chain(regions.backlog)
+            .flat_map(|&height| std::iter::repeat(height).take(columns))
+            .skip(1)
+            .collect();
+
         // Create the pod regions.
         let pod = Regions {
             first: Size::new(width, regions.first.y),
             base: Size::new(width, regions.base.y),
-            backlog: std::iter::once(&regions.first.y)
+            backlog: &backlog,
-                .chain(regions.backlog.as_slice())
-                .flat_map(|&height| std::iter::repeat(height).take(columns))
-                .skip(1)
-                .collect(),
             last: regions.last,
             expand: Axes::new(true, regions.expand.y),
         };
 
         // Layout the children.
-        let mut frames = self.child.layout(vt, styles, &pod)?.into_iter();
+        let mut frames = self.child.layout(vt, styles, pod)?.into_iter();
         let mut finished = vec![];
 
         let dir = styles.get(TextNode::DIR);

library/src/layout/container.rs

@@ -25,7 +25,7 @@ impl Layout for BoxNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         // The "pod" is the region into which the child will be layouted.
         let pod = {
@@ -47,7 +47,7 @@ impl Layout for BoxNode {
         };
 
         // Layout the child.
-        let mut frame = self.child.layout(vt, styles, &pod)?.into_frame();
+        let mut frame = self.child.layout(vt, styles, pod)?.into_frame();
 
         // Ensure frame size matches regions size if expansion is on.
         let target = regions.expand.select(regions.first, frame.size());
@@ -97,7 +97,7 @@ impl Layout for BlockNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         self.0.layout(vt, styles, regions)
     }

library/src/layout/flow.rs

@@ -22,7 +22,7 @@ impl Layout for FlowNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut layouter = FlowLayouter::new(regions, self.1);
 
@@ -55,11 +55,11 @@ impl Debug for FlowNode {
 }
 
 /// Performs flow layout.
-struct FlowLayouter {
+struct FlowLayouter<'a> {
     /// Whether this is a root page-level flow.
     root: bool,
     /// The regions to layout children into.
-    regions: Regions,
+    regions: Regions<'a>,
     /// Whether the flow should expand to fill the region.
     expand: Axes<bool>,
     /// The full size of `regions.size` that was available before we started
@@ -88,14 +88,13 @@ enum FlowItem {
     Placed(Frame),
 }
 
-impl FlowLayouter {
+impl<'a> FlowLayouter<'a> {
     /// Create a new flow layouter.
-    fn new(regions: &Regions, root: bool) -> Self {
+    fn new(mut regions: Regions<'a>, root: bool) -> Self {
         let expand = regions.expand;
         let full = regions.first;
 
         // Disable vertical expansion for children.
-        let mut regions = regions.clone();
         regions.expand.y = false;
 
         Self {
@@ -166,7 +165,7 @@ impl FlowLayouter {
         // aligned later.
         if let Some(placed) = block.to::<PlaceNode>() {
             if placed.out_of_flow() {
-                let frame = block.layout(vt, styles, &self.regions)?.into_frame();
+                let frame = block.layout(vt, styles, self.regions)?.into_frame();
                 self.layout_item(FlowItem::Placed(frame));
                 return Ok(());
             }
@@ -187,7 +186,7 @@ impl FlowLayouter {
 
         // Layout the block itself.
         let sticky = styles.get(BlockNode::STICKY);
-        let fragment = block.layout(vt, styles, &self.regions)?;
+        let fragment = block.layout(vt, styles, self.regions)?;
         for frame in fragment {
             self.layout_item(FlowItem::Frame(frame, aligns, sticky));
         }

library/src/layout/grid.rs

@@ -38,7 +38,7 @@ impl Layout for GridNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         // Prepare grid layout by unifying content and gutter tracks.
         let layouter = GridLayouter::new(
@@ -120,7 +120,7 @@ struct GridLayouter<'a, 'v> {
     /// The row tracks including gutter tracks.
     rows: Vec<TrackSizing>,
     /// The regions to layout children into.
-    regions: Regions,
+    regions: Regions<'a>,
     /// The inherited styles.
     styles: StyleChain<'a>,
     /// Resolved column sizes.
@@ -156,7 +156,7 @@ impl<'a, 'v> GridLayouter<'a, 'v> {
         tracks: Axes<&[TrackSizing]>,
         gutter: Axes<&[TrackSizing]>,
         cells: &'a [Content],
-        regions: &Regions,
+        regions: Regions<'a>,
         styles: StyleChain<'a>,
     ) -> Self {
         let mut cols = vec![];
@@ -318,7 +318,7 @@ impl<'a, 'v> GridLayouter<'a, 'v> {
                             v.resolve(self.styles).relative_to(self.regions.base.y);
                     }
 
-                    let frame = cell.layout(self.vt, self.styles, &pod)?.into_frame();
+                    let frame = cell.layout(self.vt, self.styles, pod)?.into_frame();
                     resolved.set_max(frame.width());
                 }
             }
@@ -395,7 +395,7 @@ impl<'a, 'v> GridLayouter<'a, 'v> {
                 }
 
                 let mut sizes = cell
-                    .layout(self.vt, self.styles, &pod)?
+                    .layout(self.vt, self.styles, pod)?
                     .into_iter()
                     .map(|frame| frame.height());
 
@@ -483,7 +483,7 @@ impl<'a, 'v> GridLayouter<'a, 'v> {
                     .select(self.regions.base, size);
 
                 let pod = Regions::one(size, base, Axes::splat(true));
-                let frame = cell.layout(self.vt, self.styles, &pod)?.into_frame();
+                let frame = cell.layout(self.vt, self.styles, pod)?.into_frame();
                 output.push_frame(pos, frame);
             }
 
@@ -504,7 +504,7 @@ impl<'a, 'v> GridLayouter<'a, 'v> {
         // Prepare regions.
         let size = Size::new(self.used.x, heights[0]);
         let mut pod = Regions::one(size, self.regions.base, Axes::splat(true));
-        pod.backlog = heights[1..].to_vec();
+        pod.backlog = &heights[1..];
 
         // Layout the row.
         let mut pos = Point::zero();
@@ -519,7 +519,7 @@ impl<'a, 'v> GridLayouter<'a, 'v> {
                 }
 
                 // Push the layouted frames into the individual output frames.
-                let fragment = cell.layout(self.vt, self.styles, &pod)?;
+                let fragment = cell.layout(self.vt, self.styles, pod)?;
                 for (output, frame) in outputs.iter_mut().zip(fragment) {
                     output.push_frame(pos, frame);
                 }

library/src/layout/hide.rs

@@ -16,7 +16,7 @@ impl Layout for HideNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut fragment = self.0.layout(vt, styles, regions)?;
         for frame in &mut fragment {

library/src/layout/mod.rs

@@ -90,7 +90,7 @@ pub trait Layout {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment>;
 }
 
@@ -99,7 +99,7 @@ impl Layout for Content {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         #[comemo::memoize]
         fn cached(
@@ -108,7 +108,7 @@ impl Layout for Content {
             provider: TrackedMut<StabilityProvider>,
             introspector: Tracked<Introspector>,
             styles: StyleChain,
-            regions: &Regions,
+            regions: Regions,
         ) -> SourceResult<Fragment> {
             let mut vt = Vt { world, provider, introspector };
             let scratch = Scratch::default();
@@ -137,14 +137,14 @@ impl Layout for Content {
 pub trait Inline: Layout {}
 
 /// A sequence of regions to layout into.
-#[derive(Debug, Clone, Hash)]
+#[derive(Debug, Copy, Clone, Hash)]
-pub struct Regions {
+pub struct Regions<'a> {
     /// The (remaining) size of the first region.
     pub first: Size,
     /// The base size for relative sizing.
     pub base: Size,
     /// The height of followup regions. The width is the same for all regions.
-    pub backlog: Vec<Abs>,
+    pub backlog: &'a [Abs],
     /// The height of the final region that is repeated once the backlog is
     /// drained. The width is the same for all regions.
     pub last: Option<Abs>,
@@ -153,13 +153,13 @@ pub struct Regions {
     pub expand: Axes<bool>,
 }
 
-impl Regions {
+impl<'a> Regions<'a> {
     /// Create a new region sequence with exactly one region.
     pub fn one(size: Size, base: Size, expand: Axes<bool>) -> Self {
         Self {
             first: size,
             base,
-            backlog: vec![],
+            backlog: &[],
             last: None,
             expand,
         }
@@ -170,7 +170,7 @@ impl Regions {
         Self {
             first: size,
             base,
-            backlog: vec![],
+            backlog: &[],
             last: Some(size.y),
             expand,
         }
@@ -180,15 +180,17 @@ impl Regions {
     ///
     /// Note that since all regions must have the same width, the width returned
     /// by `f` is ignored for the backlog and the final region.
-    pub fn map<F>(&self, mut f: F) -> Self
+    pub fn map<'v, F>(&self, backlog: &'v mut Vec<Abs>, mut f: F) -> Regions<'v>
     where
         F: FnMut(Size) -> Size,
     {
         let x = self.first.x;
-        Self {
+        backlog.clear();
+        backlog.extend(self.backlog.iter().map(|&y| f(Size::new(x, y)).y));
+        Regions {
             first: f(self.first),
             base: f(self.base),
-            backlog: self.backlog.iter().map(|&y| f(Size::new(x, y)).y).collect(),
+            backlog,
             last: self.last.map(|y| f(Size::new(x, y)).y),
             expand: self.expand,
         }
@@ -208,8 +210,13 @@ impl Regions {
 
     /// Advance to the next region if there is any.
     pub fn next(&mut self) {
-        if let Some(height) = (!self.backlog.is_empty())
+        if let Some(height) = self
-            .then(|| self.backlog.remove(0))
+            .backlog
+            .split_first()
+            .map(|(first, tail)| {
+                self.backlog = tail;
+                *first
+            })
             .or(self.last)
         {
             self.first.y = height;

library/src/layout/pad.rs

@@ -30,12 +30,14 @@ impl Layout for PadNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
+        let mut backlog = vec![];
+
         // Layout child into padded regions.
         let padding = self.padding.resolve(styles);
-        let pod = regions.map(|size| shrink(size, padding));
+        let pod = regions.map(&mut backlog, |size| shrink(size, padding));
-        let mut fragment = self.child.layout(vt, styles, &pod)?;
+        let mut fragment = self.child.layout(vt, styles, pod)?;
 
         for frame in &mut fragment {
             // Apply the padding inversely such that the grown size padded

library/src/layout/page.rs

@@ -97,7 +97,7 @@ impl PageNode {
 
         // Layout the child.
         let regions = Regions::repeat(size, size, size.map(Abs::is_finite));
-        let mut fragment = child.layout(vt, styles, &regions)?;
+        let mut fragment = child.layout(vt, styles, regions)?;
 
         let header = styles.get(Self::HEADER);
         let footer = styles.get(Self::FOOTER);
@@ -118,7 +118,7 @@ impl PageNode {
             ] {
                 if let Some(content) = marginal.resolve(vt, page)? {
                     let pod = Regions::one(area, area, Axes::splat(true));
-                    let sub = content.layout(vt, styles, &pod)?.into_frame();
+                    let sub = content.layout(vt, styles, pod)?.into_frame();
                     if std::ptr::eq(marginal, background) {
                         frame.prepend_frame(pos, sub);
                     } else {

library/src/layout/par.rs

@@ -538,7 +538,7 @@ fn prepare<'a>(
                 } else {
                     let size = Size::new(width, base.y);
                     let pod = Regions::one(size, base, Axes::splat(false));
-                    let mut frame = inline.layout(vt, styles, &pod)?.into_frame();
+                    let mut frame = inline.layout(vt, styles, pod)?.into_frame();
                     frame.translate(Point::with_y(styles.get(TextNode::BASELINE)));
                     items.push(Item::Frame(frame));
                 }
@@ -1125,7 +1125,7 @@ fn commit(
                 let fill = Fr::one().share(fr, remaining);
                 let size = Size::new(fill, base.y);
                 let pod = Regions::one(size, base, Axes::new(false, false));
-                let frame = repeat.layout(vt, *styles, &pod)?.into_frame();
+                let frame = repeat.layout(vt, *styles, pod)?.into_frame();
                 let width = frame.width();
                 let count = (fill / width).floor();
                 let remaining = fill % width;

library/src/layout/place.rs

@@ -21,7 +21,7 @@ impl Layout for PlaceNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let out_of_flow = self.out_of_flow();
 
@@ -33,7 +33,7 @@ impl Layout for PlaceNode {
             Regions::one(regions.base, regions.base, expand)
         };
 
-        let mut frame = self.0.layout(vt, styles, &pod)?.into_frame();
+        let mut frame = self.0.layout(vt, styles, pod)?.into_frame();
 
         // If expansion is off, zero all sizes so that we don't take up any
         // space in our parent. Otherwise, respect the expand settings.

library/src/layout/repeat.rs

@@ -16,7 +16,7 @@ impl Layout for RepeatNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         self.0.layout(vt, styles, regions)
     }

library/src/layout/stack.rs

@@ -31,7 +31,7 @@ impl Layout for StackNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut layouter = StackLayouter::new(self.dir, regions, styles);
 
@@ -94,7 +94,7 @@ struct StackLayouter<'a> {
     /// The axis of the stacking direction.
     axis: Axis,
     /// The regions to layout children into.
-    regions: Regions,
+    regions: Regions<'a>,
     /// The inherited styles.
     styles: StyleChain<'a>,
     /// Whether the stack itself should expand to fill the region.
@@ -124,7 +124,7 @@ enum StackItem {
 
 impl<'a> StackLayouter<'a> {
     /// Create a new stack layouter.
-    fn new(dir: Dir, regions: &Regions, styles: StyleChain<'a>) -> Self {
+    fn new(dir: Dir, regions: Regions<'a>, styles: StyleChain<'a>) -> Self {
         let axis = dir.axis();
         let expand = regions.expand;
         let full = regions.first;
@@ -195,7 +195,7 @@ impl<'a> StackLayouter<'a> {
                 self.dir.start().into()
             });
 
-        let fragment = block.layout(vt, styles, &self.regions)?;
+        let fragment = block.layout(vt, styles, self.regions)?;
         let len = fragment.len();
         for (i, frame) in fragment.into_iter().enumerate() {
             // Grow our size, shrink the region and save the frame for later.

library/src/layout/transform.rs

@@ -29,7 +29,7 @@ impl Layout for MoveNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut fragment = self.child.layout(vt, styles, regions)?;
         for frame in &mut fragment {
@@ -87,7 +87,7 @@ impl<const T: TransformKind> Layout for TransformNode<T> {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut fragment = self.child.layout(vt, styles, regions)?;
         for frame in &mut fragment {

library/src/math/mod.rs

@@ -57,7 +57,7 @@ impl Layout for MathNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        _: &Regions,
+        _: Regions,
     ) -> SourceResult<Fragment> {
         let mut t = Texifier::new(styles);
         self.texify(&mut t)?;

library/src/shared/ext.rs

@@ -114,7 +114,7 @@ impl Layout for FillNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut fragment = self.child.layout(vt, styles, regions)?;
         for frame in &mut fragment {
@@ -142,7 +142,7 @@ impl Layout for StrokeNode {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut fragment = self.child.layout(vt, styles, regions)?;
         for frame in &mut fragment {

library/src/visualize/image.rs

@@ -41,14 +41,14 @@ impl Layout for ImageNode {
         &self,
         _: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let pxw = self.0.width() as f64;
         let pxh = self.0.height() as f64;
         let px_ratio = pxw / pxh;
 
         // Find out whether the image is wider or taller than the target size.
-        let &Regions { first, expand, .. } = regions;
+        let Regions { first, expand, .. } = regions;
         let region_ratio = first.x / first.y;
         let wide = px_ratio > region_ratio;
 

library/src/visualize/line.rs

@@ -41,7 +41,7 @@ impl Layout for LineNode {
         &self,
         _: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let stroke = styles.get(Self::STROKE).unwrap_or_default();
 

library/src/visualize/shape.rs

@@ -76,7 +76,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
         &self,
         vt: &mut Vt,
         styles: StyleChain,
-        regions: &Regions,
+        regions: Regions,
     ) -> SourceResult<Fragment> {
         let mut frame;
         if let Some(child) = &self.0 {
@@ -89,7 +89,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
             let child = child.clone().padded(inset.map(|side| side.map(Length::from)));
 
             let mut pod = Regions::one(regions.first, regions.base, regions.expand);
-            frame = child.layout(vt, styles, &pod)?.into_frame();
+            frame = child.layout(vt, styles, pod)?.into_frame();
 
             // Relayout with full expansion into square region to make sure
             // the result is really a square or circle.
@@ -105,7 +105,7 @@ impl<const S: ShapeKind> Layout for ShapeNode<S> {
 
                 pod.first = Size::splat(length);
                 pod.expand = Axes::splat(true);
-                frame = child.layout(vt, styles, &pod)?.into_frame();
+                frame = child.layout(vt, styles, pod)?.into_frame();
             }
         } else {
             // The default size that a shape takes on if it has no child and