Rename expand to fixed and switch to bools

src/layout/fixed.rs

@@ -31,13 +31,8 @@ impl Layout for FixedNode {
             size = Size::new(width, width / aspect);
         }
 
-        let fill_if = |cond| if cond { Expand::Fill } else { Expand::Fit };
-        let expand = Spec::new(
-            fill_if(self.width.is_some()),
-            fill_if(self.height.is_some()),
-        );
-
-        let areas = Areas::once(size, full, expand).with_aspect(self.aspect);
+        let fixed = Spec::new(self.width.is_some(), self.height.is_some());
+        let areas = Areas::once(size, full, fixed).with_aspect(self.aspect);
         self.child.layout(ctx, &areas)
     }
 }

src/layout/frame.rs

@@ -18,6 +18,7 @@ pub struct Frame {
 impl Frame {
     /// Create a new, empty frame.
     pub fn new(size: Size, baseline: Length) -> Self {
+        assert!(size.is_finite());
         Self { size, baseline, elements: vec![] }
     }
 

src/layout/mod.rs

@@ -54,7 +54,11 @@ pub struct PageRun {
 impl PageRun {
     /// Layout the page run.
     pub fn layout(&self, ctx: &mut LayoutContext) -> Vec<Frame> {
-        let areas = Areas::repeat(self.size, Spec::uniform(Expand::Fill));
+        // When one of the lengths is infinite the page fits its content along
+        // that axis.
+        let Size { width, height } = self.size;
+        let fixed = Spec::new(width.is_finite(), height.is_finite());
+        let areas = Areas::repeat(self.size, fixed);
         self.child.layout(ctx, &areas)
     }
 }
@@ -146,12 +150,11 @@ pub struct Areas {
     pub backlog: Vec<Size>,
     /// The final area that is repeated when the backlog is empty.
     pub last: Option<Size>,
-    /// Whether the frames resulting from layouting into this areas should be
-    /// shrunk to fit their content or expanded to fill the area.
+    /// Whether the frames resulting from layouting into this areas should
+    /// expand to the fixed size defined by `current`.
     ///
-    /// This property is handled partially by the par layouter and fully by the
-    /// stack layouter.
-    pub expand: Spec<Expand>,
+    /// If this is false, the frame will shrink to fit its content.
+    pub fixed: Spec<bool>,
     /// The aspect ratio the resulting frame should respect.
     ///
     /// This property is only handled by the stack layouter.
@@ -159,26 +162,26 @@ pub struct Areas {
 }
 
 impl Areas {
-    /// Create a new sequence of areas that repeats `area` indefinitely.
-    pub fn repeat(size: Size, expand: Spec<Expand>) -> Self {
-        Self {
-            current: size,
-            full: size,
-            backlog: vec![],
-            last: Some(size),
-            expand,
-            aspect: None,
-        }
-    }
-
     /// Create a new length-1 sequence of areas with just one `area`.
-    pub fn once(size: Size, full: Size, expand: Spec<Expand>) -> Self {
+    pub fn once(size: Size, full: Size, fixed: Spec<bool>) -> Self {
         Self {
             current: size,
             full,
             backlog: vec![],
             last: None,
-            expand,
+            fixed,
+            aspect: None,
+        }
+    }
+
+    /// Create a new sequence of areas that repeats `area` indefinitely.
+    pub fn repeat(size: Size, fixed: Spec<bool>) -> Self {
+        Self {
+            current: size,
+            full: size,
+            backlog: vec![],
+            last: Some(size),
+            fixed,
             aspect: None,
         }
     }
@@ -199,7 +202,7 @@ impl Areas {
             full: f(self.full),
             backlog: self.backlog.iter().copied().map(|s| f(s)).collect(),
             last: self.last.map(f),
-            expand: self.expand,
+            fixed: self.fixed,
             aspect: self.aspect,
         }
     }
@@ -222,24 +225,3 @@ impl Areas {
             })
     }
 }
-
-/// Whether to expand or shrink a node along an axis.
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub enum Expand {
-    /// Fit the content.
-    Fit,
-    /// Fill the available space.
-    Fill,
-}
-
-impl Expand {
-    /// Resolve the expansion to either the `fit` or `fill` length.
-    ///
-    /// Prefers `fit` if `fill` is infinite.
-    pub fn resolve(self, fit: Length, fill: Length) -> Length {
-        match self {
-            Self::Fill if fill.is_finite() => fill,
-            _ => fit,
-        }
-    }
-}

src/layout/par.rs

@@ -301,8 +301,9 @@ impl<'a> LineStack<'a> {
     }
 
     fn finish_area(&mut self, ctx: &mut LayoutContext) {
-        let expand = self.areas.expand.horizontal;
-        self.size.width = expand.resolve(self.size.width, self.areas.full.width);
+        if self.areas.fixed.horizontal {
+            self.size.width = self.areas.current.width;
+        }
 
         let mut output = Frame::new(self.size, self.size.height);
         let mut first = true;

src/layout/stack.rs

@@ -104,12 +104,12 @@ impl StackLayouter {
 
     fn finish_area(&mut self) {
         let full_size = {
-            let Areas { current, full, expand, .. } = self.areas;
-            let used = self.size.switch(self.main).to_size();
+            let Areas { current, full, fixed, .. } = self.areas;
 
+            let used = self.size.switch(self.main).to_size();
             let mut size = Size::new(
-                expand.horizontal.resolve(used.width, full.width),
-                expand.vertical.resolve(used.height, full.height),
+                if fixed.horizontal { full.width } else { used.width },
+                if fixed.vertical { full.height } else { used.height },
             );
 
             if let Some(aspect) = self.areas.aspect {