Reduce style chain bloat

library/src/layout/mod.rs

@@ -33,7 +33,7 @@ use typst::frame::Frame;
 use typst::geom::*;
 use typst::model::{
     capability, Barrier, Content, Node, SequenceNode, Show, StyleChain, StyleEntry,
-    StyleMap, StyleVec, StyleVecBuilder, StyledNode, Target,
+    StyleVec, StyleVecBuilder, StyledNode, Target,
 };
 use typst::World;
 
@@ -253,8 +253,10 @@ struct Builder<'a> {
 struct Scratch<'a> {
     /// An arena where intermediate style chains are stored.
     styles: Arena<StyleChain<'a>>,
+    /// An arena for individual intermediate style entries.
+    entries: Arena<StyleEntry>,
     /// An arena where intermediate content resulting from show rules is stored.
-    templates: Arena<Content>,
+    content: Arena<Content>,
 }
 
 /// Determines whether a style could interrupt some composable structure.
@@ -305,7 +307,7 @@ impl<'a> Builder<'a> {
     ) -> SourceResult<()> {
         if let Some(text) = content.downcast::<TextNode>() {
             if let Some(realized) = styles.apply(self.world, Target::Text(&text.0))? {
-                let stored = self.scratch.templates.alloc(realized);
+                let stored = self.scratch.content.alloc(realized);
                 return self.accept(stored, styles);
             }
         } else if let Some(styled) = content.downcast::<StyledNode>() {
@@ -357,16 +359,18 @@ impl<'a> Builder<'a> {
         content: &'a Content,
         styles: StyleChain<'a>,
     ) -> SourceResult<bool> {
-        let Some(mut realized) = styles.apply(self.world, Target::Node(content))? else {
+        let barrier = StyleEntry::Barrier(Barrier::new(content.id()));
+        let styles = self
+            .scratch
+            .entries
+            .alloc(barrier)
+            .chain(self.scratch.styles.alloc(styles));
+
+        let Some(realized) = styles.apply(self.world, Target::Node(content))? else {
             return Ok(false);
         };
 
-        let mut map = StyleMap::new();
+        let stored = self.scratch.content.alloc(realized);
-        let barrier = Barrier::new(content.id());
-        map.push(StyleEntry::Barrier(barrier));
-        map.push(StyleEntry::Barrier(barrier));
-        realized = realized.styled_with_map(map);
-        let stored = self.scratch.templates.alloc(realized);
         self.accept(stored, styles)?;
 
         Ok(true)
@@ -680,7 +684,7 @@ impl<'a> ListBuilder<'a> {
             DESC | _ => ListNode::<DESC> { tight, attached, items }.pack(),
         };
 
-        let stored = parent.scratch.templates.alloc(content);
+        let stored = parent.scratch.content.alloc(content);
         parent.accept(stored, shared)?;
 
         for (content, styles) in self.staged {

library/src/text/mod.rs

@@ -25,7 +25,7 @@ use self::quotes::*;
 use crate::prelude::*;
 
 /// A single run of text with the same style.
-#[derive(Debug, Clone, Hash)]
+#[derive(Clone, Hash)]
 pub struct TextNode(pub EcoString);
 
 impl TextNode {
@@ -169,6 +169,12 @@ impl TextNode {
     }
 }
 
+impl Debug for TextNode {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "Text({:?})", self.0)
+    }
+}
+
 /// A lowercased font family like "arial".
 #[derive(Clone, Eq, PartialEq, Hash)]
 pub struct FontFamily(EcoString);

src/model/content.rs

@@ -115,10 +115,14 @@ impl Content {
     pub fn styled_with_entry(mut self, entry: StyleEntry) -> Self {
         if let Some(styled) = self.try_downcast_mut::<StyledNode>() {
             styled.map.apply(entry);
-            return self;
+            self
+        } else if let Some(styled) = self.downcast::<StyledNode>() {
+            let mut map = styled.map.clone();
+            map.apply(entry);
+            StyledNode { sub: styled.sub.clone(), map }.pack()
+        } else {
+            StyledNode { sub: self, map: entry.into() }.pack()
         }
-
-        StyledNode { sub: self, map: entry.into() }.pack()
     }
 
     /// Style this content with a full style map.

src/model/styles.rs

@@ -85,6 +85,15 @@ impl StyleMap {
     /// Like [`chain`](Self::chain) or [`apply_map`](Self::apply_map), but with
     /// only a entry.
     pub fn apply(&mut self, entry: StyleEntry) {
+        if let StyleEntry::Guard(a) = &entry {
+            if let [StyleEntry::Unguard(b), ..] = self.0.as_slice() {
+                if a == b {
+                    self.0.remove(0);
+                    return;
+                }
+            }
+        }
+
         self.0.insert(0, entry);
     }
 
@@ -124,7 +133,7 @@ impl From<StyleEntry> for StyleMap {
 
 impl Debug for StyleMap {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        for entry in self.0.iter().rev() {
+        for entry in self.0.iter() {
             writeln!(f, "{:?}", entry)?;
         }
         Ok(())
@@ -351,7 +360,7 @@ impl<'a> StyleChain<'a> {
 
 impl Debug for StyleChain<'_> {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        for entry in self.entries() {
+        for entry in self.entries().collect::<Vec<_>>().into_iter().rev() {
             writeln!(f, "{:?}", entry)?;
         }
         Ok(())

src/util/mod.rs

@@ -161,9 +161,13 @@ impl ReadableTypeId {
 impl Debug for ReadableTypeId {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         #[cfg(debug_assertions)]
-        f.pad(self.name)?;
+        if let Some(part) = self.name.split("::").last() {
+            f.pad(part)?;
+        }
+
         #[cfg(not(debug_assertions))]
         f.pad("ReadableTypeId")?;
+
         Ok(())
     }
 }