Remove width from backlog and last region

4 files changed, 70 insertions, 80 deletions

diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 147e8c9d..ebdfba0e 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -200,6 +200,7 @@ impl PackedNode {
 }
 
 impl Layout for PackedNode {
+    #[track_caller]
     fn layout(
         &self,
         ctx: &mut LayoutContext,
@@ -219,8 +220,12 @@ impl Layout for PackedNode {
             state.finish()
         };
 
+        // This is not written with `unwrap_or_else`, because then the
+        // #[track_caller] annotation doesn't work.
         #[cfg(feature = "layout-cache")]
-        ctx.layout_cache.get(hash, regions).unwrap_or_else(|| {
+        if let Some(frames) = ctx.layout_cache.get(hash, regions) {
+            frames
+        } else {
             ctx.level += 1;
             let frames = self.node.layout(ctx, regions, styles);
             ctx.level -= 1;
@@ -240,7 +245,7 @@ impl Layout for PackedNode {
 
             ctx.layout_cache.insert(hash, entry);
             frames
-        })
+        }
     }
 
     fn pack(self) -> PackedNode {
diff --git a/src/layout/regions.rs b/src/layout/regions.rs
index 66e6da17..3f8b6d25 100644
--- a/src/layout/regions.rs
+++ b/src/layout/regions.rs
@@ -7,10 +7,11 @@ pub struct Regions {
     pub current: Size,
     /// The base size for relative sizing.
     pub base: Size,
-    /// An iterator of followup regions.
-    pub backlog: std::vec::IntoIter<Size>,
-    /// The final region that is repeated once the backlog is drained.
-    pub last: Option<Size>,
+    /// The height of followup regions. The width is the same for all regions.
+    pub backlog: std::vec::IntoIter<Length>,
+    /// 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<Length>,
     /// Whether nodes should expand to fill the regions instead of shrinking to
     /// fit the content.
     pub expand: Spec<bool>,
@@ -34,19 +35,33 @@ impl Regions {
             current: size,
             base,
             backlog: vec![].into_iter(),
-            last: Some(size),
+            last: Some(size.y),
             expand,
         }
     }
 
     /// Create new regions where all sizes are mapped with `f`.
+    ///
+    /// 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
     where
         F: FnMut(Size) -> Size,
     {
-        let mut regions = self.clone();
-        regions.mutate(|s| *s = f(*s));
-        regions
+        let x = self.current.x;
+        Self {
+            current: f(self.current),
+            base: f(self.base),
+            backlog: self
+                .backlog
+                .as_slice()
+                .iter()
+                .map(|&y| f(Size::new(x, y)).y)
+                .collect::<Vec<_>>()
+                .into_iter(),
+            last: self.last.map(|y| f(Size::new(x, y)).y),
+            expand: self.expand,
+        }
     }
 
     /// Whether the current region is full and a region break is called for.
@@ -58,14 +73,15 @@ impl Regions {
     ///
     /// If this is true, calling `next()` will have no effect.
     pub fn in_last(&self) -> bool {
-        self.backlog.len() == 0 && self.last.map_or(true, |size| self.current == size)
+        self.backlog.len() == 0
+            && self.last.map_or(true, |height| self.current.y == height)
     }
 
     /// Advance to the next region if there is any.
     pub fn next(&mut self) {
-        if let Some(size) = self.backlog.next().or(self.last) {
-            self.current = size;
-            self.base = size;
+        if let Some(height) = self.backlog.next().or(self.last) {
+            self.current.y = height;
+            self.base.y = height;
         }
     }
 
@@ -76,17 +92,11 @@ impl Regions {
         let first = std::iter::once((self.current, self.base));
         let backlog = self.backlog.as_slice().iter();
         let last = self.last.iter().cycle();
-        first.chain(backlog.chain(last).map(|&s| (s, s)))
-    }
-
-    /// Mutate all contained sizes in place.
-    pub fn mutate<F>(&mut self, mut f: F)
-    where
-        F: FnMut(&mut Size),
-    {
-        f(&mut self.current);
-        f(&mut self.base);
-        self.last.as_mut().map(|x| f(x));
-        self.backlog.as_mut_slice().iter_mut().for_each(f);
+        first.chain(backlog.chain(last).map(|&height| {
+            (
+                Size::new(self.current.x, height),
+                Size::new(self.base.x, height),
+            )
+        }))
     }
 }
diff --git a/src/library/columns.rs b/src/library/columns.rs
index 149da755..5ea76973 100644
--- a/src/library/columns.rs
+++ b/src/library/columns.rs
@@ -38,63 +38,40 @@ impl Layout for ColumnsNode {
         regions: &Regions,
         styles: StyleChain,
     ) -> Vec<Constrained<Arc<Frame>>> {
-        let columns = self.columns.get();
-
         // Separating the infinite space into infinite columns does not make
-        // much sense. Note that this line assumes that no infinitely wide
-        // region will follow if the first region's width is finite.
+        // much sense.
         if regions.current.x.is_infinite() {
             return self.child.layout(ctx, regions, styles);
         }
 
-        // Gutter width for each region. (Can be different because the relative
-        // component is calculated seperately for each region.)
-        let mut gutters = vec![];
-
-        // Sizes of all columns resulting from `region.current`,
-        // `region.backlog` and `regions.last`.
-        let mut sizes = vec![];
-
-        for (current, base) in regions
-            .iter()
-            .take(1 + regions.backlog.len() + regions.last.iter().len())
-        {
-            let gutter = styles.get(Self::GUTTER).resolve(base.x);
-            let width = (current.x - gutter * (columns - 1) as f64) / columns as f64;
-            let size = Size::new(width, current.y);
-            gutters.push(gutter);
-            sizes.extend(std::iter::repeat(size).take(columns));
-        }
-
-        let first = sizes.remove(0);
-        let mut pod = Regions::one(
-            first,
-            Size::new(first.x, regions.base.y),
-            Spec::new(true, regions.expand.y),
-        );
-
-        // Retrieve elements for the last region from the vectors.
-        let last_gutter = regions.last.map(|_| {
-            let gutter = gutters.pop().unwrap();
-            let size = sizes.drain(sizes.len() - columns ..).next().unwrap();
-            pod.last = Some(size);
-            gutter
-        });
-
-        pod.backlog = sizes.into_iter();
-
-        let mut finished = vec![];
+        // Determine the width of the gutter and each column.
+        let columns = self.columns.get();
+        let gutter = styles.get(Self::GUTTER).resolve(regions.base.x);
+        let width = (regions.current.x - gutter * (columns - 1) as f64) / columns as f64;
+
+        // Create the pod regions.
+        let pod = Regions {
+            current: Size::new(width, regions.current.y),
+            base: Size::new(width, regions.base.y),
+            backlog: std::iter::once(&regions.current.y)
+                .chain(regions.backlog.as_slice())
+                .flat_map(|&height| std::iter::repeat(height).take(columns))
+                .skip(1)
+                .collect::<Vec<_>>()
+                .into_iter(),
+            last: regions.last,
+            expand: Spec::new(true, regions.expand.y),
+        };
+
+        // Layout the children.
         let mut frames = self.child.layout(ctx, &pod, styles).into_iter();
 
         let dir = styles.get(ParNode::DIR);
         let total_regions = (frames.len() as f32 / columns as f32).ceil() as usize;
+        let mut finished = vec![];
 
         // Stitch together the columns for each region.
-        for ((current, base), gutter) in regions
-            .iter()
-            .take(total_regions)
-            .zip(gutters.into_iter().chain(last_gutter.into_iter().cycle()))
-        {
+        for (current, base) in regions.iter().take(total_regions) {
             // The height should be the parent height if the node shall expand.
             // Otherwise its the maximum column height for the frame. In that
             // case, the frame is first created with zero height and then
diff --git a/src/library/grid.rs b/src/library/grid.rs
index c49ac84f..6a9b790a 100644
--- a/src/library/grid.rs
+++ b/src/library/grid.rs
@@ -386,9 +386,10 @@ impl<'a> GridLayouter<'a> {
         // Determine the size for each region of the row.
         for (x, &rcol) in self.rcols.iter().enumerate() {
             if let Some(node) = self.cell(x, y) {
-                // All widths should be `rcol` except the base for auto columns.
                 let mut pod = self.regions.clone();
-                pod.mutate(|size| size.x = rcol);
+                pod.current.x = rcol;
+
+                // All widths should be `rcol` except the base for auto columns.
                 if self.cols[x] == TrackSizing::Auto {
                     pod.base.x = self.regions.base.x;
                 }
@@ -513,18 +514,15 @@ impl<'a> GridLayouter<'a> {
         // Prepare regions.
         let size = Size::new(self.used.x, heights[0]);
         let mut pod = Regions::one(size, self.regions.base, Spec::splat(true));
-        pod.backlog = heights[1 ..]
-            .iter()
-            .map(|&h| Size::new(self.used.x, h))
-            .collect::<Vec<_>>()
-            .into_iter();
+        pod.backlog = heights[1 ..].to_vec().into_iter();
 
         // Layout the row.
         let mut pos = Point::zero();
         for (x, &rcol) in self.rcols.iter().enumerate() {
             if let Some(node) = self.cell(x, y) {
+                pod.current.x = rcol;
+
                 // All widths should be `rcol` except the base for auto columns.
-                pod.mutate(|size| size.x = rcol);
                 if self.cols[x] == TrackSizing::Auto {
                     pod.base.x = self.regions.base.x;
                 }