No more excessive region cloning

4 files changed, 33 insertions, 22 deletions

diff --git a/src/layout/incremental.rs b/src/layout/incremental.rs
index e5bad892..60486d2f 100644
--- a/src/layout/incremental.rs
+++ b/src/layout/incremental.rs
@@ -50,11 +50,11 @@ impl LayoutCache {
     pub fn get(
         &mut self,
         hash: u64,
-        regions: Regions,
+        regions: &Regions,
     ) -> Option<Vec<Constrained<Rc<Frame>>>> {
         let entries = self.frames.get_mut(&hash)?;
         for entry in entries {
-            if let Some(frames) = entry.check(regions.clone()) {
+            if let Some(frames) = entry.check(regions) {
                 return Some(frames);
             }
         }
@@ -136,9 +136,11 @@ impl FramesEntry {
 
     /// Checks if the cached frames are valid in the given regions and returns
     /// them if so.
-    pub fn check(&mut self, mut regions: Regions) -> Option<Vec<Constrained<Rc<Frame>>>> {
-        for (i, frame) in self.frames.iter().enumerate() {
-            if (i != 0 && !regions.next()) || !frame.constraints.check(&regions) {
+    pub fn check(&mut self, regions: &Regions) -> Option<Vec<Constrained<Rc<Frame>>>> {
+        let mut iter = regions.iter();
+        for frame in &self.frames {
+            let (current, base) = iter.next()?;
+            if !frame.constraints.check(current, base, regions.expand) {
                 return None;
             }
         }
@@ -175,11 +177,13 @@ impl FramesEntry {
     }
 }
 
-/// Carries an item that only applies to certain regions and the constraints
+/// Carries an item that is only valid in certain regions and the constraints
 /// that describe these regions.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub struct Constrained<T> {
+    /// The item that is only valid if the constraints are fullfilled.
     pub item: T,
+    /// Constraints on regions in which the item is valid.
     pub constraints: Constraints,
 }
 
@@ -218,16 +222,13 @@ impl Constraints {
         }
     }
 
-    #[cfg(feature = "layout-cache")]
-    fn check(&self, regions: &Regions) -> bool {
-        if self.expand != regions.expand {
-            return false;
-        }
-
-        let base = regions.base.to_spec();
-        let current = regions.current.to_spec();
-
-        current.eq_by(&self.min, |x, y| y.map_or(true, |y| x.fits(y)))
+    /// Check whether the constraints are fullfilled in a region with the given
+    /// properties.
+    pub fn check(&self, current: Size, base: Size, expand: Spec<bool>) -> bool {
+        let current = current.to_spec();
+        let base = base.to_spec();
+        self.expand == expand
+            && current.eq_by(&self.min, |x, y| y.map_or(true, |y| x.fits(y)))
             && current.eq_by(&self.max, |x, y| y.map_or(true, |y| x < &y))
             && current.eq_by(&self.exact, |x, y| y.map_or(true, |y| x.approx_eq(y)))
             && base.eq_by(&self.base, |x, y| y.map_or(true, |y| x.approx_eq(y)))
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 22e6e8c8..0f88d150 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -140,14 +140,21 @@ impl Regions {
         self.backlog.is_empty() && self.last.map_or(true, |size| self.current == size)
     }
 
+    /// An iterator that returns pairs of `(current, base)` that are equivalent
+    /// to what would be produced by calling [`next()`](Self::next) repeatedly
+    /// until all regions are exhausted.
+    pub fn iter(&self) -> impl Iterator<Item = (Size, Size)> + '_ {
+        let first = std::iter::once((self.current, self.base));
+        let backlog = self.backlog.iter().rev();
+        let last = self.last.iter().cycle();
+        first.chain(backlog.chain(last).map(|&s| (s, s)))
+    }
+
     /// Advance to the next region if there is any.
-    pub fn next(&mut self) -> bool {
+    pub fn next(&mut self) {
         if let Some(size) = self.backlog.pop().or(self.last) {
             self.current = size;
             self.base = size;
-            true
-        } else {
-            false
         }
     }
 
diff --git a/src/layout/tree.rs b/src/layout/tree.rs
index 77b01ad2..4b21e05c 100644
--- a/src/layout/tree.rs
+++ b/src/layout/tree.rs
@@ -86,7 +86,7 @@ impl Layout for LayoutNode {
         return self.node.layout(ctx, regions);
 
         #[cfg(feature = "layout-cache")]
-        ctx.layouts.get(self.hash, regions.clone()).unwrap_or_else(|| {
+        ctx.layouts.get(self.hash, regions).unwrap_or_else(|| {
             ctx.level += 1;
             let frames = self.node.layout(ctx, regions);
             ctx.level -= 1;
diff --git a/tests/typeset.rs b/tests/typeset.rs
index 59eb008f..3e83fcb5 100644
--- a/tests/typeset.rs
+++ b/tests/typeset.rs
@@ -16,12 +16,15 @@ use typst::eval::{eval, Scope, Value};
 use typst::exec::{exec, State};
 use typst::geom::{self, Length, PathElement, Point, Sides, Size};
 use typst::image::ImageId;
-use typst::layout::{layout, Element, Frame, Geometry, LayoutTree, Paint, Text};
+use typst::layout::{layout, Element, Frame, Geometry, Paint, Text};
 use typst::loading::{FileId, FsLoader};
 use typst::parse::{parse, LineMap, Scanner};
 use typst::syntax::{Location, Pos};
 use typst::Context;
 
+#[cfg(feature = "layout-cache")]
+use typst::layout::LayoutTree;
+
 const TYP_DIR: &str = "./typ";
 const REF_DIR: &str = "./ref";
 const PNG_DIR: &str = "./png";