Section references

3 files changed, 69 insertions, 15 deletions

diff --git a/src/model/content.rs b/src/model/content.rs
index 17fa786b..be737331 100644
--- a/src/model/content.rs
+++ b/src/model/content.rs
@@ -10,7 +10,7 @@ use once_cell::sync::Lazy;
 
 use super::{node, Guard, Recipe, Style, StyleMap};
 use crate::diag::{SourceResult, StrResult};
-use crate::eval::{cast_from_value, Args, FuncInfo, Str, Value, Vm};
+use crate::eval::{cast_from_value, Args, Cast, FuncInfo, Str, Value, Vm};
 use crate::syntax::Span;
 use crate::util::pretty_array_like;
 use crate::World;
@@ -27,7 +27,7 @@ pub struct Content {
 /// Modifiers that can be attached to content.
 #[derive(Debug, Clone, PartialEq, Hash)]
 enum Modifier {
-    Prepared,
+    Synthesized,
     Guard(Guard),
 }
 
@@ -59,6 +59,12 @@ impl Content {
         self.id
     }
 
+    /// Whether the content is empty.
+    pub fn is_empty(&self) -> bool {
+        self.to::<SequenceNode>()
+            .map_or(false, |seq| seq.children().is_empty())
+    }
+
     /// Whether the contained node is of type `T`.
     pub fn is<T>(&self) -> bool
     where
@@ -112,6 +118,21 @@ impl Content {
             .map(|(_, value)| value)
     }
 
+    /// Access a field on the content as a specified type.
+    #[track_caller]
+    pub fn cast_field<T: Cast>(&self, name: &str) -> Option<T> {
+        match self.field(name) {
+            Some(value) => Some(value.clone().cast().unwrap()),
+            None => None,
+        }
+    }
+
+    /// Expect a field on the content to exist as a specified type.
+    #[track_caller]
+    pub fn expect_field<T: Cast>(&self, name: &str) -> T {
+        self.cast_field(name).unwrap()
+    }
+
     /// List all fields on the content.
     pub fn fields(&self) -> &[(EcoString, Value)] {
         &self.fields
@@ -209,14 +230,14 @@ impl Content {
     }
 
     /// Mark this content as prepared.
-    pub fn prepared(mut self) -> Self {
-        self.modifiers.push(Modifier::Prepared);
+    pub fn synthesized(mut self) -> Self {
+        self.modifiers.push(Modifier::Synthesized);
         self
     }
 
     /// Whether this node was prepared.
-    pub fn is_prepared(&self) -> bool {
-        self.modifiers.contains(&Modifier::Prepared)
+    pub fn is_synthesized(&self) -> bool {
+        self.modifiers.contains(&Modifier::Synthesized)
     }
 
     /// Whether no show rule was executed for this node so far.
diff --git a/src/model/realize.rs b/src/model/realize.rs
index c4c67a4f..4685a605 100644
--- a/src/model/realize.rs
+++ b/src/model/realize.rs
@@ -3,7 +3,7 @@ use crate::diag::SourceResult;
 
 /// Whether the target is affected by show rules in the given style chain.
 pub fn applicable(target: &Content, styles: StyleChain) -> bool {
-    if target.can::<dyn Prepare>() && !target.is_prepared() {
+    if target.can::<dyn Synthesize>() && !target.is_synthesized() {
         return true;
     }
 
@@ -34,6 +34,18 @@ pub fn realize(
     // Find out how many recipes there are.
     let mut n = styles.recipes().count();
 
+    // Synthesize if not already happened for this node.
+    if target.can::<dyn Synthesize>() && !target.is_synthesized() {
+        return Ok(Some(
+            target
+                .clone()
+                .synthesized()
+                .with::<dyn Synthesize>()
+                .unwrap()
+                .synthesize(vt, styles),
+        ));
+    }
+
     // Find an applicable recipe.
     let mut realized = None;
     for recipe in styles.recipes() {
@@ -132,10 +144,10 @@ fn try_apply(
     }
 }
 
-/// Preparations before execution of any show rule.
-pub trait Prepare {
+/// Synthesize fields on a node. This happens before execution of any show rule.
+pub trait Synthesize {
     /// Prepare the node for show rule application.
-    fn prepare(&self, vt: &mut Vt, styles: StyleChain) -> SourceResult<Content>;
+    fn synthesize(&self, vt: &mut Vt, styles: StyleChain) -> Content;
 }
 
 /// The base recipe for a node.
diff --git a/src/model/typeset.rs b/src/model/typeset.rs
index 6361e6ce..377c7c76 100644
--- a/src/model/typeset.rs
+++ b/src/model/typeset.rs
@@ -77,6 +77,11 @@ impl<'a> Vt<'a> {
         self.provider.identify(hash128(key))
     }
 
+    /// Whether things are locatable already.
+    pub fn locatable(&self) -> bool {
+        self.introspector.init()
+    }
+
     /// Locate all metadata matches for the given selector.
     pub fn locate(&self, selector: Selector) -> Vec<(StableId, &Content)> {
         self.introspector.locate(selector)
@@ -115,6 +120,7 @@ impl StabilityProvider {
 /// Provides access to information about the document.
 #[doc(hidden)]
 pub struct Introspector {
+    init: bool,
     nodes: Vec<(StableId, Content)>,
     queries: RefCell<Vec<(Selector, u128)>>,
 }
@@ -122,7 +128,11 @@ pub struct Introspector {
 impl Introspector {
     /// Create a new introspector.
     fn new() -> Self {
-        Self { nodes: vec![], queries: RefCell::new(vec![]) }
+        Self {
+            init: false,
+            nodes: vec![],
+            queries: RefCell::new(vec![]),
+        }
     }
 
     /// Update the information given new frames and return whether we can stop
@@ -135,14 +145,20 @@ impl Introspector {
             self.extract(frame, page, Transform::identity());
         }
 
+        let was_init = std::mem::replace(&mut self.init, true);
         let queries = std::mem::take(&mut self.queries).into_inner();
-        for (selector, hash) in queries {
-            let nodes = self.locate_impl(&selector);
-            if hash128(&nodes) != hash {
+
+        for (selector, hash) in &queries {
+            let nodes = self.locate_impl(selector);
+            if hash128(&nodes) != *hash {
                 return false;
             }
         }
 
+        if !was_init && !queries.is_empty() {
+            return false;
+        }
+
         true
     }
 
@@ -161,7 +177,7 @@ impl Introspector {
                         let pos = pos.transform(ts);
                         let mut node = content.clone();
                         let loc = Location { page, pos };
-                        node.push_field("loc", loc);
+                        node.push_field("location", loc);
                         self.nodes.push((id, node));
                     }
                 }
@@ -173,6 +189,11 @@ impl Introspector {
 
 #[comemo::track]
 impl Introspector {
+    /// Whether this introspector is not yet initialized.
+    fn init(&self) -> bool {
+        self.init
+    }
+
     /// Locate all metadata matches for the given selector.
     fn locate(&self, selector: Selector) -> Vec<(StableId, &Content)> {
         let nodes = self.locate_impl(&selector);