Fix panic due to bad alignments in stack function

src/eval/ops.rs

@@ -181,13 +181,13 @@ pub fn div(lhs: Value, rhs: Value) -> StrResult<Value> {
         (Relative(a), Float(b)) => Relative(a / b),
         (Relative(a), Relative(b)) => Float(a / b),
 
+        (Linear(a), Int(b)) => Linear(a / b as f64),
+        (Linear(a), Float(b)) => Linear(a / b),
+
         (Fractional(a), Int(b)) => Fractional(a / b as f64),
         (Fractional(a), Float(b)) => Fractional(a / b),
         (Fractional(a), Fractional(b)) => Float(a / b),
 
-        (Linear(a), Int(b)) => Linear(a / b as f64),
-        (Linear(a), Float(b)) => Linear(a / b),
-
         (a, b) => mismatch!("cannot divide {} by {}", a, b),
     })
 }

src/layout/par.rs

@@ -96,9 +96,9 @@ impl From<ParNode> for LayoutNode {
 impl Debug for ParChild {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
-            ParChild::Spacing(v) => write!(f, "Spacing({:?})", v),
-            ParChild::Text(text, ..) => write!(f, "Text({:?})", text),
-            ParChild::Any(node, ..) => f.debug_tuple("Any").field(node).finish(),
+            Self::Spacing(v) => write!(f, "Spacing({:?})", v),
+            Self::Text(text, ..) => write!(f, "Text({:?})", text),
+            Self::Any(node, ..) => node.fmt(f),
         }
     }
 }

src/layout/stack.rs

@@ -1,3 +1,5 @@
+use std::fmt::{self, Debug, Formatter};
+
 use super::*;
 
 /// A node that stacks its children.
@@ -14,7 +16,6 @@ pub struct StackNode {
 }
 
 /// A child of a stack node.
-#[derive(Debug)]
 #[cfg_attr(feature = "layout-cache", derive(Hash))]
 pub enum StackChild {
     /// Spacing between other nodes.
@@ -39,6 +40,15 @@ impl From<StackNode> for LayoutNode {
     }
 }
 
+impl Debug for StackChild {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Self::Spacing(v) => write!(f, "Spacing({:?})", v),
+            Self::Any(node, _) => node.fmt(f),
+        }
+    }
+}
+
 /// Performs stack layout.
 struct StackLayouter<'a> {
     /// The stack node to layout.

src/library/layout.rs

@@ -192,11 +192,6 @@ pub fn stack(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
     let children: Vec<Template> = args.all().collect();
 
     Ok(Value::Template(Template::from_block(move |state| {
-        let children = children
-            .iter()
-            .map(|child| StackChild::Any(child.to_stack(state).into(), state.aligns))
-            .collect();
-
         let mut dirs = Gen::new(None, dir).unwrap_or(state.dirs);
 
         // If the directions become aligned, fix up the inline direction since
@@ -205,6 +200,19 @@ pub fn stack(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
             dirs.inline = state.dirs.block;
         }
 
+        // Use the current alignments for all children, but take care to apply
+        // them to the correct axes (by swapping them if the stack axes are
+        // different from the state axes).
+        let mut aligns = state.aligns;
+        if dirs.block.axis() == state.dirs.inline.axis() {
+            aligns = Gen::new(aligns.block, aligns.inline);
+        }
+
+        let children = children
+            .iter()
+            .map(|child| StackChild::Any(child.to_stack(state).into(), aligns))
+            .collect();
+
         StackNode { dirs, children }
     })))
 }
@@ -233,9 +241,6 @@ pub fn grid(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
     );
 
     Ok(Value::Template(Template::from_block(move |state| {
-        let children =
-            children.iter().map(|child| child.to_stack(&state).into()).collect();
-
         // If the directions become aligned, try to fix up the direction which
         // is not user-defined.
         let mut dirs = Gen::new(column_dir, row_dir).unwrap_or(state.dirs);
@@ -253,6 +258,9 @@ pub fn grid(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
             };
         }
 
+        let children =
+            children.iter().map(|child| child.to_stack(&state).into()).collect();
+
         GridNode {
             dirs,
             tracks: tracks.clone(),

tests/typ/layout/stack.typ

@@ -1,18 +1,32 @@
 // Test stack layouts.
 
 ---
-#let rect(width, fill) = rect(width: width, height: 1cm, fill: fill)
-#stack(
-  rect(2cm, rgb("2a631a")),
-  rect(3cm, forest),
-  rect(1cm, conifer),
+// Test stacks with different directions.
+#let widths = (
+  30pt, 20pt, 40pt, 15pt,
+  30pt, 50%, 20pt, 100%,
 )
 
+#let shaded = {
+  let v = 0
+  let next() = { v += 0.1; rgb(v, v, v) }
+  w => rect(width: w, height: 10pt, fill: next())
+}
+
+#let items = for w in widths { (shaded(w),) }
+
+#align(right)
+#page(width: 50pt, margins: 0pt)
+#stack(dir: btt, ..items)
+#pagebreak()
+
+// Currently stack works like flexbox apparently.
+#stack(dir: ltr, ..items)
+
 ---
 // Test overflowing stack.
-
-#let rect(width, fill) = rect(width: 1cm, height: 0.4cm, fill: fill)
-#box(height: 0.5cm, stack(
-  rect(3cm, forest),
-  rect(1cm, conifer),
+#page(width: 50pt, height: 30pt, margins: 0pt)
+#box(stack(
+  rect(width: 40pt, height: 20pt, fill: conifer),
+  rect(width: 30pt, height: 13pt, fill: forest),
 ))