Locate me!

5 files changed, 195 insertions, 16 deletions

diff --git a/src/model/content.rs b/src/model/content.rs
index c09979d5..effe84ae 100644
--- a/src/model/content.rs
+++ b/src/model/content.rs
@@ -7,8 +7,8 @@ use std::ops::{Add, AddAssign};
 use typed_arena::Arena;
 
 use super::{
-    Barrier, CollapsingBuilder, Interruption, Key, Layout, LayoutNode, Property, Show,
-    ShowNode, StyleEntry, StyleMap, StyleVecBuilder, Target,
+    Barrier, CollapsingBuilder, Interruption, Key, Layout, LayoutNode, LocateNode,
+    Property, Show, ShowNode, StyleEntry, StyleMap, StyleVecBuilder, Target,
 };
 use crate::diag::StrResult;
 use crate::library::layout::{FlowChild, FlowNode, PageNode, PlaceNode, Spacing};
@@ -20,7 +20,35 @@ use crate::library::text::{
 use crate::util::EcoString;
 
 /// Layout content into a collection of pages.
+///
+/// Relayouts until all pinned locations are converged.
 pub fn layout(ctx: &mut Context, content: &Content) -> TypResult<Vec<Arc<Frame>>> {
+    let mut pass = 0;
+    let mut frames;
+
+    loop {
+        let prev = ctx.pins.clone();
+        let result = layout_once(ctx, content);
+        ctx.pins.reset();
+        frames = result?;
+        pass += 1;
+
+        ctx.pins.locate(&frames);
+
+        let count = ctx.pins.len();
+        let resolved = ctx.pins.resolved(&prev);
+
+        // Quit if we're done or if we've had five passes.
+        if resolved == count || pass >= 5 {
+            break;
+        }
+    }
+
+    Ok(frames)
+}
+
+/// Layout content into a collection of pages once.
+fn layout_once(ctx: &mut Context, content: &Content) -> TypResult<Vec<Arc<Frame>>> {
     let copy = ctx.config.styles.clone();
     let styles = StyleChain::with_root(&copy);
     let scratch = Scratch::default();
@@ -88,6 +116,10 @@ pub enum Content {
     /// A node that can be realized with styles, optionally with attached
     /// properties.
     Show(ShowNode, Option<Dict>),
+    /// A node that can be realized with its location on the page.
+    Locate(LocateNode),
+    /// A pin identified by index.
+    Pin(usize),
     /// Content with attached styles.
     Styled(Arc<(Self, StyleMap)>),
     /// A sequence of multiple nodes.
@@ -272,6 +304,8 @@ impl Debug for Content {
             Self::Pagebreak { weak } => write!(f, "Pagebreak({weak})"),
             Self::Page(page) => page.fmt(f),
             Self::Show(node, _) => node.fmt(f),
+            Self::Locate(node) => node.fmt(f),
+            Self::Pin(idx) => write!(f, "Pin({idx})"),
             Self::Styled(styled) => {
                 let (sub, map) = styled.as_ref();
                 map.fmt(f)?;
@@ -388,6 +422,7 @@ impl<'a, 'ctx> Builder<'a, 'ctx> {
             }
 
             Content::Show(node, _) => return self.show(node, styles),
+            Content::Locate(node) => return self.locate(node, styles),
             Content::Styled(styled) => return self.styled(styled, styles),
             Content::Sequence(seq) => return self.sequence(seq, styles),
 
@@ -436,6 +471,12 @@ impl<'a, 'ctx> Builder<'a, 'ctx> {
         Ok(())
     }
 
+    fn locate(&mut self, node: &LocateNode, styles: StyleChain<'a>) -> TypResult<()> {
+        let realized = node.realize(self.ctx)?;
+        let stored = self.scratch.templates.alloc(realized);
+        self.accept(stored, styles)
+    }
+
     fn styled(
         &mut self,
         (content, map): &'a (Content, StyleMap),
@@ -641,6 +682,9 @@ impl<'a> ParBuilder<'a> {
             Content::Inline(node) => {
                 self.0.supportive(ParChild::Node(node.clone()), styles);
             }
+            &Content::Pin(idx) => {
+                self.0.ignorant(ParChild::Pin(idx), styles);
+            }
             _ => return false,
         }
 
@@ -660,7 +704,7 @@ impl<'a> ParBuilder<'a> {
             && children
                 .items()
                 .find_map(|child| match child {
-                    ParChild::Spacing(_) => None,
+                    ParChild::Spacing(_) | ParChild::Pin(_) => None,
                     ParChild::Text(_) | ParChild::Quote { .. } => Some(true),
                     ParChild::Node(_) => Some(false),
                 })
diff --git a/src/model/layout.rs b/src/model/layout.rs
index 6dfbcb90..49720be4 100644
--- a/src/model/layout.rs
+++ b/src/model/layout.rs
@@ -221,13 +221,19 @@ impl Layout for LayoutNode {
         regions: &Regions,
         styles: StyleChain,
     ) -> TypResult<Vec<Arc<Frame>>> {
-        crate::memo::memoized(
-            (self, ctx, regions, styles),
+        let (result, cursor) = crate::memo::memoized(
+            (self, &mut *ctx, regions, styles),
             |(node, ctx, regions, styles)| {
                 let entry = StyleEntry::Barrier(Barrier::new(node.id()));
-                node.0.layout(ctx, regions, entry.chain(&styles))
+                let result = node.0.layout(ctx, regions, entry.chain(&styles));
+                (result, ctx.pins.cursor())
             },
-        )
+        );
+
+        // Replay the side effect in case of caching. This should currently be
+        // more or less the only relevant side effect on the context.
+        ctx.pins.jump(cursor);
+        result
     }
 
     fn pack(self) -> LayoutNode {
diff --git a/src/model/locate.rs b/src/model/locate.rs
new file mode 100644
index 00000000..9b0d13e7
--- /dev/null
+++ b/src/model/locate.rs
@@ -0,0 +1,125 @@
+use std::sync::Arc;
+
+use super::Content;
+use crate::diag::TypResult;
+use crate::eval::{Args, Func, Value};
+use crate::frame::{Element, Frame};
+use crate::geom::{Point, Transform};
+use crate::syntax::Spanned;
+use crate::Context;
+
+/// A node that can realize itself with its own location.
+#[derive(Debug, Clone, PartialEq, Hash)]
+pub struct LocateNode(Spanned<Func>);
+
+impl LocateNode {
+    /// Create a new locate node.
+    pub fn new(recipe: Spanned<Func>) -> Self {
+        Self(recipe)
+    }
+
+    /// Realize the node.
+    pub fn realize(&self, ctx: &mut Context) -> TypResult<Content> {
+        let idx = ctx.pins.cursor();
+        let location = ctx.pins.next();
+        let dict = dict! {
+            "page" => Value::Int(location.page as i64),
+            "x" => Value::Length(location.pos.x.into()),
+            "y" => Value::Length(location.pos.y.into()),
+        };
+
+        let args = Args::new(self.0.span, [Value::Dict(dict)]);
+        Ok(Content::Pin(idx) + self.0.v.call_detached(ctx, args)?.display())
+    }
+}
+
+/// Manages ordered pins.
+#[derive(Debug, Clone, PartialEq, Hash)]
+pub struct PinBoard {
+    /// All currently pinned locations.
+    pins: Vec<Location>,
+    /// The index of the next pin in order.
+    cursor: usize,
+}
+
+impl PinBoard {
+    /// Create an empty pin board.
+    pub fn new() -> Self {
+        Self { pins: vec![], cursor: 0 }
+    }
+
+    /// The number of pins on the board.
+    pub fn len(&self) -> usize {
+        self.pins.len()
+    }
+
+    /// How many pins are resolved in comparison to an earlier snapshot.
+    pub fn resolved(&self, prev: &Self) -> usize {
+        self.pins.iter().zip(&prev.pins).filter(|(a, b)| a == b).count()
+    }
+
+    /// Access the next pin location.
+    pub fn next(&mut self) -> Location {
+        let cursor = self.cursor;
+        self.jump(self.cursor + 1);
+        self.pins[cursor]
+    }
+
+    /// The current cursor.
+    pub fn cursor(&self) -> usize {
+        self.cursor
+    }
+
+    /// Set the current cursor.
+    pub fn jump(&mut self, cursor: usize) {
+        if cursor >= self.pins.len() {
+            let loc = self.pins.last().copied().unwrap_or_default();
+            self.pins.resize(cursor + 1, loc);
+        }
+        self.cursor = cursor;
+    }
+
+    /// Reset the cursor and remove all unused pins.
+    pub fn reset(&mut self) {
+        self.pins.truncate(self.cursor);
+        self.cursor = 0;
+    }
+
+    /// Locate all pins in the frames.
+    pub fn locate(&mut self, frames: &[Arc<Frame>]) {
+        for (i, frame) in frames.iter().enumerate() {
+            self.locate_impl(1 + i, frame, Transform::identity());
+        }
+    }
+
+    /// Locate all pins in a frame.
+    fn locate_impl(&mut self, page: usize, frame: &Frame, ts: Transform) {
+        for &(pos, ref element) in &frame.elements {
+            match element {
+                Element::Group(group) => {
+                    let ts = ts
+                        .pre_concat(Transform::translate(pos.x, pos.y))
+                        .pre_concat(group.transform);
+                    self.locate_impl(page, &group.frame, ts);
+                }
+
+                Element::Pin(idx) => {
+                    let pin = &mut self.pins[*idx];
+                    pin.page = page;
+                    pin.pos = pos.transform(ts);
+                }
+
+                _ => {}
+            }
+        }
+    }
+}
+
+/// A physical location in a document.
+#[derive(Debug, Default, Copy, Clone, PartialEq, Hash)]
+pub struct Location {
+    /// The page, starting at 1.
+    pub page: usize,
+    /// The exact coordinates on the page (from the top left, as usual).
+    pub pos: Point,
+}
diff --git a/src/model/mod.rs b/src/model/mod.rs
index 5c8b82c0..379b633f 100644
--- a/src/model/mod.rs
+++ b/src/model/mod.rs
@@ -5,6 +5,7 @@ mod styles;
 mod collapse;
 mod content;
 mod layout;
+mod locate;
 mod property;
 mod recipe;
 mod show;
@@ -12,6 +13,7 @@ mod show;
 pub use collapse::*;
 pub use content::*;
 pub use layout::*;
+pub use locate::*;
 pub use property::*;
 pub use recipe::*;
 pub use show::*;
diff --git a/src/model/recipe.rs b/src/model/recipe.rs
index e4417adf..6261e704 100644
--- a/src/model/recipe.rs
+++ b/src/model/recipe.rs
@@ -4,7 +4,7 @@ use super::{Content, Interruption, NodeId, Show, ShowNode, StyleChain, StyleEntr
 use crate::diag::TypResult;
 use crate::eval::{Args, Func, Regex, Value};
 use crate::library::structure::{EnumNode, ListNode};
-use crate::syntax::Span;
+use crate::syntax::Spanned;
 use crate::Context;
 
 /// A show rule recipe.
@@ -13,9 +13,7 @@ pub struct Recipe {
     /// The patterns to customize.
     pub pattern: Pattern,
     /// The function that defines the recipe.
-    pub func: Func,
-    /// The span to report all erros with.
-    pub span: Span,
+    pub func: Spanned<Func>,
 }
 
 impl Recipe {
@@ -81,13 +79,13 @@ impl Recipe {
     where
         F: FnOnce() -> Value,
     {
-        let args = if self.func.argc() == Some(0) {
-            Args::new(self.span, [])
+        let args = if self.func.v.argc() == Some(0) {
+            Args::new(self.func.span, [])
         } else {
-            Args::new(self.span, [arg()])
+            Args::new(self.func.span, [arg()])
         };
 
-        Ok(self.func.call_detached(ctx, args)?.display())
+        Ok(self.func.v.call_detached(ctx, args)?.display())
     }
 
     /// What kind of structure the property interrupts.
@@ -104,7 +102,11 @@ impl Recipe {
 
 impl Debug for Recipe {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "Recipe matching {:?} from {:?}", self.pattern, self.span)
+        write!(
+            f,
+            "Recipe matching {:?} from {:?}",
+            self.pattern, self.func.span
+        )
     }
 }