Dynamic labels

7 files changed, 54 insertions, 17 deletions

diff --git a/src/model/cast.rs b/src/model/cast.rs
index d5b4893d..0e7739ac 100644
--- a/src/model/cast.rs
+++ b/src/model/cast.rs
@@ -183,8 +183,9 @@ dynamic! {
 
 dynamic! {
     Selector: "selector",
-    Value::Func(func) => Self::Node(func.node()?, None),
     Value::Str(text) => Self::text(&text),
+    Value::Label(label) => Self::Label(label),
+    Value::Func(func) => Self::Node(func.node()?, None),
     @regex: Regex => Self::Regex(regex.clone()),
 }
 
diff --git a/src/model/content.rs b/src/model/content.rs
index 0faf76cb..a7161798 100644
--- a/src/model/content.rs
+++ b/src/model/content.rs
@@ -21,7 +21,7 @@ pub struct Content {
     obj: Arc<dyn Bounds>,
     guards: Vec<Guard>,
     span: Option<Span>,
-    label: Option<EcoString>,
+    label: Option<Label>,
 }
 
 impl Content {
@@ -54,7 +54,7 @@ impl Content {
     }
 
     /// Attach a label to the content.
-    pub fn labelled(mut self, label: EcoString) -> Self {
+    pub fn labelled(mut self, label: Label) -> Self {
         self.label = Some(label);
         self
     }
@@ -131,7 +131,7 @@ impl Content {
     }
 
     /// The content's label.
-    pub fn label(&self) -> Option<&EcoString> {
+    pub fn label(&self) -> Option<&Label> {
         self.label.as_ref()
     }
 
@@ -139,7 +139,7 @@ impl Content {
     pub fn field(&self, name: &str) -> Option<Value> {
         if name == "label" {
             return Some(match &self.label {
-                Some(label) => Value::Str(label.clone().into()),
+                Some(label) => Value::Label(label.clone()),
                 None => Value::None,
             });
         }
@@ -335,6 +335,16 @@ impl Debug for SequenceNode {
     }
 }
 
+/// A label for a node.
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Label(pub EcoString);
+
+impl Debug for Label {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "<{}>", self.0)
+    }
+}
+
 /// A constructable, stylable content node.
 pub trait Node: 'static + Capable {
     /// Pack a node into type-erased content.
diff --git a/src/model/eval.rs b/src/model/eval.rs
index 9ed6195e..6c21a666 100644
--- a/src/model/eval.rs
+++ b/src/model/eval.rs
@@ -8,7 +8,7 @@ use comemo::{Track, Tracked};
 use unicode_segmentation::UnicodeSegmentation;
 
 use super::{
-    methods, ops, Arg, Args, Array, CapturesVisitor, Closure, Content, Dict, Func,
+    methods, ops, Arg, Args, Array, CapturesVisitor, Closure, Content, Dict, Func, Label,
     LangItems, Recipe, Scope, Scopes, Selector, StyleMap, Transform, Value,
 };
 use crate::diag::{
@@ -231,11 +231,16 @@ fn eval_markup(
                 let tail = eval_markup(vm, nodes)?;
                 seq.push(tail.styled_with_recipe(vm.world, recipe)?)
             }
-            ast::MarkupNode::Label(label) => {
-                if let Some(node) = seq.iter_mut().rev().find(|node| node.labellable()) {
-                    *node = mem::take(node).labelled(label.get().clone());
+            ast::MarkupNode::Expr(expr) => match expr.eval(vm)? {
+                Value::Label(label) => {
+                    if let Some(node) =
+                        seq.iter_mut().rev().find(|node| node.labellable())
+                    {
+                        *node = mem::take(node).labelled(label);
+                    }
                 }
-            }
+                value => seq.push(value.display().spanned(expr.span())),
+            },
             _ => seq.push(node.eval(vm)?),
         }
 
@@ -274,9 +279,8 @@ impl Eval for ast::MarkupNode {
             Self::List(v) => v.eval(vm)?,
             Self::Enum(v) => v.eval(vm)?,
             Self::Desc(v) => v.eval(vm)?,
-            Self::Label(_) => unimplemented!("handled above"),
             Self::Ref(v) => v.eval(vm)?,
-            Self::Expr(v) => v.eval(vm)?.display(),
+            Self::Expr(_) => unimplemented!("handled above"),
         }
         .spanned(self.span()))
     }
@@ -527,6 +531,7 @@ impl Eval for ast::Lit {
                 Unit::Percent => Ratio::new(v / 100.0).into(),
             },
             ast::LitKind::Str(v) => Value::Str(v.into()),
+            ast::LitKind::Label(v) => Value::Label(Label(v)),
         })
     }
 }
diff --git a/src/model/ops.rs b/src/model/ops.rs
index 0110fb96..9a731d65 100644
--- a/src/model/ops.rs
+++ b/src/model/ops.rs
@@ -307,6 +307,7 @@ pub fn equal(lhs: &Value, rhs: &Value) -> bool {
         (Fraction(a), Fraction(b)) => a == b,
         (Color(a), Color(b)) => a == b,
         (Str(a), Str(b)) => a == b,
+        (Label(a), Label(b)) => a == b,
         (Content(a), Content(b)) => a == b,
         (Array(a), Array(b)) => a == b,
         (Dict(a), Dict(b)) => a == b,
diff --git a/src/model/realize.rs b/src/model/realize.rs
index d63c1aac..9d7c4aec 100644
--- a/src/model/realize.rs
+++ b/src/model/realize.rs
@@ -78,6 +78,14 @@ fn try_apply(
             recipe.apply(world, target.clone().guarded(guard)).map(Some)
         }
 
+        Some(Selector::Label(label)) => {
+            if target.label() != Some(label) {
+                return Ok(None);
+            }
+
+            recipe.apply(world, target.clone().guarded(guard)).map(Some)
+        }
+
         Some(Selector::Regex(regex)) => {
             let Some(text) = item!(text_str)(&target) else {
                 return Ok(None);
diff --git a/src/model/styles.rs b/src/model/styles.rs
index 966a57ec..f3cfb648 100644
--- a/src/model/styles.rs
+++ b/src/model/styles.rs
@@ -7,7 +7,7 @@ use std::sync::Arc;
 
 use comemo::{Prehashed, Tracked};
 
-use super::{Args, Content, Dict, Func, NodeId, Regex, Smart, Value};
+use super::{Args, Content, Dict, Func, Label, NodeId, Regex, Smart, Value};
 use crate::diag::{SourceResult, Trace, Tracepoint};
 use crate::geom::{
     Abs, Align, Axes, Corners, Em, GenAlign, Length, Numeric, PartialStroke, Rel, Sides,
@@ -354,7 +354,9 @@ pub enum Selector {
     /// If there is a dictionary, only nodes with the fields from the
     /// dictionary match.
     Node(NodeId, Option<Dict>),
-    /// Matches text through a regular expression.
+    /// Matches nodes with a specific label.
+    Label(Label),
+    /// Matches text nodes through a regular expression.
     Regex(Regex),
 }
 
@@ -368,13 +370,17 @@ impl Selector {
     pub fn matches(&self, target: &Content) -> bool {
         match self {
             Self::Node(id, dict) => {
-                *id == target.id()
+                target.id() == *id
                     && dict
                         .iter()
                         .flat_map(|dict| dict.iter())
                         .all(|(name, value)| target.field(name).as_ref() == Some(value))
             }
-            Self::Regex(_) => target.id() == item!(text_id),
+            Self::Label(label) => target.label() == Some(label),
+            Self::Regex(regex) => {
+                target.id() == item!(text_id)
+                    && item!(text_str)(target).map_or(false, |text| regex.is_match(text))
+            }
         }
     }
 }
diff --git a/src/model/value.rs b/src/model/value.rs
index aec68ca1..043fde34 100644
--- a/src/model/value.rs
+++ b/src/model/value.rs
@@ -6,7 +6,7 @@ use std::sync::Arc;
 
 use siphasher::sip128::{Hasher128, SipHasher};
 
-use super::{format_str, ops, Args, Array, Cast, Content, Dict, Func, Str};
+use super::{format_str, ops, Args, Array, Cast, Content, Dict, Func, Label, Str};
 use crate::diag::StrResult;
 use crate::geom::{Abs, Angle, Color, Em, Fr, Length, Ratio, Rel, RgbaColor};
 use crate::util::{format_eco, EcoString};
@@ -38,6 +38,8 @@ pub enum Value {
     Color(Color),
     /// A string: `"string"`.
     Str(Str),
+    /// A label: `<intro>`.
+    Label(Label),
     /// A content value: `[*Hi* there]`.
     Content(Content),
     /// An array of values: `(1, "hi", 12cm)`.
@@ -76,6 +78,7 @@ impl Value {
             Self::Fraction(_) => Fr::TYPE_NAME,
             Self::Color(_) => Color::TYPE_NAME,
             Self::Str(_) => Str::TYPE_NAME,
+            Self::Label(_) => Label::TYPE_NAME,
             Self::Content(_) => Content::TYPE_NAME,
             Self::Array(_) => Array::TYPE_NAME,
             Self::Dict(_) => Dict::TYPE_NAME,
@@ -130,6 +133,7 @@ impl Debug for Value {
             Self::Fraction(v) => Debug::fmt(v, f),
             Self::Color(v) => Debug::fmt(v, f),
             Self::Str(v) => Debug::fmt(v, f),
+            Self::Label(v) => Debug::fmt(v, f),
             Self::Content(_) => f.pad("[...]"),
             Self::Array(v) => Debug::fmt(v, f),
             Self::Dict(v) => Debug::fmt(v, f),
@@ -168,6 +172,7 @@ impl Hash for Value {
             Self::Fraction(v) => v.hash(state),
             Self::Color(v) => v.hash(state),
             Self::Str(v) => v.hash(state),
+            Self::Label(v) => v.hash(state),
             Self::Content(v) => v.hash(state),
             Self::Array(v) => v.hash(state),
             Self::Dict(v) => v.hash(state),
@@ -373,6 +378,7 @@ primitive! { Rel<Length>:  "relative length",
 primitive! { Fr: "fraction", Fraction }
 primitive! { Color: "color", Color }
 primitive! { Str: "string", Str }
+primitive! { Label: "label", Label }
 primitive! { Content: "content",
     Content,
     None => Content::empty(),