BoxAlign and Flow aliases ✏

18 files changed, 150 insertions, 124 deletions

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index e1fa8c1a..2cff835b 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -22,7 +22,7 @@ use fontdock::FontStyle;
 
 use crate::diag::Diag;
 use crate::diag::{Deco, Feedback, Pass};
-use crate::geom::{Align, Dir, Gen, Length, Linear, Relative, Sides, Size};
+use crate::geom::{BoxAlign, Flow, Gen, Length, Linear, Relative, Sides, Size};
 use crate::layout::{
     Document, Expansion, LayoutNode, Pad, Pages, Par, Softness, Spacing, Stack, Text,
 };
@@ -122,8 +122,8 @@ impl EvalContext {
         self.start_group(PageGroup {
             size: self.state.page.size,
             padding: self.state.page.margins(),
-            dirs: self.state.dirs,
-            aligns: self.state.aligns,
+            flow: self.state.flow,
+            align: self.state.align,
             hard,
         });
         self.start_par_group();
@@ -141,9 +141,9 @@ impl EvalContext {
                 child: LayoutNode::dynamic(Pad {
                     padding: group.padding,
                     child: LayoutNode::dynamic(Stack {
-                        dirs: group.dirs,
-                        aligns: group.aligns,
-                        expansion: Gen::new(Expansion::Fill, Expansion::Fill),
+                        flow: group.flow,
+                        align: group.align,
+                        expansion: Gen::uniform(Expansion::Fill),
                         children,
                     }),
                 }),
@@ -171,8 +171,8 @@ impl EvalContext {
     pub fn start_par_group(&mut self) {
         let em = self.state.font.font_size();
         self.start_group(ParGroup {
-            dirs: self.state.dirs,
-            aligns: self.state.aligns,
+            flow: self.state.flow,
+            align: self.state.align,
             line_spacing: self.state.par.line_spacing.resolve(em),
         });
     }
@@ -185,8 +185,8 @@ impl EvalContext {
             //        better.
             let cross_expansion = Expansion::fill_if(self.groups.len() <= 1);
             self.push(Par {
-                dirs: group.dirs,
-                aligns: group.aligns,
+                flow: group.flow,
+                align: group.align,
                 cross_expansion,
                 line_spacing: group.line_spacing,
                 children,
@@ -242,11 +242,11 @@ impl EvalContext {
 
         Text {
             text,
-            dir: self.state.dirs.cross,
+            align: self.state.align,
+            dir: self.state.flow.cross,
             font_size: self.state.font.font_size(),
             families: Rc::clone(&self.state.font.families),
             variant,
-            aligns: self.state.aligns,
         }
     }
 }
@@ -255,8 +255,8 @@ impl EvalContext {
 struct PageGroup {
     size: Size,
     padding: Sides<Linear>,
-    dirs: Gen<Dir>,
-    aligns: Gen<Align>,
+    flow: Flow,
+    align: BoxAlign,
     hard: bool,
 }
 
@@ -265,8 +265,8 @@ struct ContentGroup;
 
 /// A group for paragraphs.
 struct ParGroup {
-    dirs: Gen<Dir>,
-    aligns: Gen<Align>,
+    flow: Flow,
+    align: BoxAlign,
     line_spacing: Length,
 }
 
@@ -370,9 +370,9 @@ impl Eval for NodeRaw {
         }
 
         ctx.push(Stack {
-            dirs: ctx.state.dirs,
-            aligns: ctx.state.aligns,
-            expansion: Gen::new(Expansion::Fit, Expansion::Fit),
+            flow: ctx.state.flow,
+            align: ctx.state.align,
+            expansion: Gen::uniform(Expansion::Fit),
             children,
         });
 
diff --git a/src/eval/state.rs b/src/eval/state.rs
index 521e8c12..cb4a5eb9 100644
--- a/src/eval/state.rs
+++ b/src/eval/state.rs
@@ -5,7 +5,7 @@ use std::rc::Rc;
 use fontdock::{fallback, FallbackTree, FontStretch, FontStyle, FontVariant, FontWeight};
 
 use super::Scope;
-use crate::geom::{Align, Dir, Gen, Length, Linear, Relative, Sides, Size};
+use crate::geom::{Align, BoxAlign, Dir, Flow, Length, Linear, Relative, Sides, Size};
 use crate::paper::{Paper, PaperClass, PAPER_A4};
 
 /// The active evaluation state.
@@ -20,9 +20,9 @@ pub struct State {
     /// The font state.
     pub font: FontState,
     /// The active layouting directions.
-    pub dirs: Gen<Dir>,
-    /// The active alignments.
-    pub aligns: Gen<Align>,
+    pub flow: Flow,
+    /// The active box alignments.
+    pub align: BoxAlign,
 }
 
 impl Default for State {
@@ -32,8 +32,8 @@ impl Default for State {
             page: PageState::default(),
             par: ParState::default(),
             font: FontState::default(),
-            dirs: Gen::new(Dir::TTB, Dir::LTR),
-            aligns: Gen::new(Align::Start, Align::Start),
+            flow: Flow::new(Dir::TTB, Dir::LTR),
+            align: BoxAlign::new(Align::Start, Align::Start),
         }
     }
 }
diff --git a/src/geom/align.rs b/src/geom/align.rs
index 422624d8..7c4d965f 100644
--- a/src/geom/align.rs
+++ b/src/geom/align.rs
@@ -1,5 +1,8 @@
 use super::*;
 
+/// The alignment of a box in a container.
+pub type BoxAlign = Gen<Align>;
+
 /// Where to align something along a directed axis.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
 pub enum Align {
diff --git a/src/geom/dir.rs b/src/geom/dir.rs
index cfcb4c09..f7ffa3e2 100644
--- a/src/geom/dir.rs
+++ b/src/geom/dir.rs
@@ -1,5 +1,8 @@
 use super::*;
 
+/// The directions along which content flows in a container.
+pub type Flow = Gen<Dir>;
+
 /// The four directions into which content can be laid out.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum Dir {
diff --git a/src/geom/gen.rs b/src/geom/gen.rs
index d877713b..11b117ea 100644
--- a/src/geom/gen.rs
+++ b/src/geom/gen.rs
@@ -14,6 +14,14 @@ impl<T> Gen<T> {
     pub fn new(main: T, cross: T) -> Self {
         Self { main, cross }
     }
+
+    /// Create a new instance with two equal components.
+    pub fn uniform(value: T) -> Self
+    where
+        T: Clone,
+    {
+        Self { main: value.clone(), cross: value }
+    }
 }
 
 impl Gen<Length> {
@@ -42,8 +50,8 @@ impl<T> Get<GenAxis> for Gen<T> {
 impl<T> Switch for Gen<T> {
     type Other = Spec<T>;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
-        match dirs.main.axis() {
+    fn switch(self, flow: Flow) -> Self::Other {
+        match flow.main.axis() {
             SpecAxis::Horizontal => Spec::new(self.main, self.cross),
             SpecAxis::Vertical => Spec::new(self.cross, self.main),
         }
@@ -72,10 +80,10 @@ impl GenAxis {
 impl Switch for GenAxis {
     type Other = SpecAxis;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
+    fn switch(self, flow: Flow) -> Self::Other {
         match self {
-            Self::Main => dirs.main.axis(),
-            Self::Cross => dirs.cross.axis(),
+            Self::Main => flow.main.axis(),
+            Self::Cross => flow.cross.axis(),
         }
     }
 }
diff --git a/src/geom/mod.rs b/src/geom/mod.rs
index 9fdb2693..0589346e 100644
--- a/src/geom/mod.rs
+++ b/src/geom/mod.rs
@@ -48,6 +48,7 @@ pub trait Switch {
     /// The type of the other version.
     type Other;
 
-    /// The other version of this type based on the current directions.
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other;
+    /// The other version of this type based on the current layouting
+    /// directions.
+    fn switch(self, flow: Flow) -> Self::Other;
 }
diff --git a/src/geom/point.rs b/src/geom/point.rs
index 31b84d81..10ab2d3a 100644
--- a/src/geom/point.rs
+++ b/src/geom/point.rs
@@ -40,8 +40,8 @@ impl Get<SpecAxis> for Point {
 impl Switch for Point {
     type Other = Gen<Length>;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
-        match dirs.main.axis() {
+    fn switch(self, flow: Flow) -> Self::Other {
+        match flow.main.axis() {
             SpecAxis::Horizontal => Gen::new(self.x, self.y),
             SpecAxis::Vertical => Gen::new(self.y, self.x),
         }
diff --git a/src/geom/sides.rs b/src/geom/sides.rs
index 39487ff7..292f00c4 100644
--- a/src/geom/sides.rs
+++ b/src/geom/sides.rs
@@ -14,12 +14,12 @@ pub struct Sides<T> {
 }
 
 impl<T> Sides<T> {
-    /// Create a new box from four sizes.
+    /// Create a new instance from the four components.
     pub fn new(left: T, top: T, right: T, bottom: T) -> Self {
         Self { left, top, right, bottom }
     }
 
-    /// Create an instance with all four components set to the same `value`.
+    /// Create an instance with four equal components.
     pub fn uniform(value: T) -> Self
     where
         T: Clone,
diff --git a/src/geom/size.rs b/src/geom/size.rs
index 8a3951f7..0ad0e0f8 100644
--- a/src/geom/size.rs
+++ b/src/geom/size.rs
@@ -48,8 +48,8 @@ impl Get<SpecAxis> for Size {
 impl Switch for Size {
     type Other = Gen<Length>;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
-        match dirs.main.axis() {
+    fn switch(self, flow: Flow) -> Self::Other {
+        match flow.main.axis() {
             SpecAxis::Horizontal => Gen::new(self.width, self.height),
             SpecAxis::Vertical => Gen::new(self.height, self.width),
         }
diff --git a/src/geom/spec.rs b/src/geom/spec.rs
index 8a9519bc..f259ce25 100644
--- a/src/geom/spec.rs
+++ b/src/geom/spec.rs
@@ -14,6 +14,17 @@ impl<T> Spec<T> {
     pub fn new(horizontal: T, vertical: T) -> Self {
         Self { horizontal, vertical }
     }
+
+    /// Create a new instance with two equal components.
+    pub fn uniform(value: T) -> Self
+    where
+        T: Clone,
+    {
+        Self {
+            horizontal: value.clone(),
+            vertical: value,
+        }
+    }
 }
 
 impl Spec<Length> {
@@ -55,8 +66,8 @@ impl<T> Get<SpecAxis> for Spec<T> {
 impl<T> Switch for Spec<T> {
     type Other = Gen<T>;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
-        match dirs.main.axis() {
+    fn switch(self, flow: Flow) -> Self::Other {
+        match flow.main.axis() {
             SpecAxis::Horizontal => Gen::new(self.horizontal, self.vertical),
             SpecAxis::Vertical => Gen::new(self.vertical, self.horizontal),
         }
@@ -85,11 +96,11 @@ impl SpecAxis {
 impl Switch for SpecAxis {
     type Other = GenAxis;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
-        if self == dirs.main.axis() {
+    fn switch(self, flow: Flow) -> Self::Other {
+        if self == flow.main.axis() {
             GenAxis::Main
         } else {
-            debug_assert_eq!(self, dirs.cross.axis());
+            debug_assert_eq!(self, flow.cross.axis());
             GenAxis::Cross
         }
     }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 362e5a7f..4dd6184f 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -128,9 +128,9 @@ pub enum Layouted {
     /// Spacing that should be added to the parent.
     Spacing(Length),
     /// A layout that should be added to and aligned in the parent.
-    Layout(BoxLayout, Gen<Align>),
+    Layout(BoxLayout, BoxAlign),
     /// Multiple layouts.
-    Layouts(Vec<BoxLayout>, Gen<Align>),
+    Layouts(Vec<BoxLayout>, BoxAlign),
 }
 
 impl Layouted {
diff --git a/src/layout/par.rs b/src/layout/par.rs
index bd38442d..723f27cb 100644
--- a/src/layout/par.rs
+++ b/src/layout/par.rs
@@ -7,15 +7,15 @@ pub struct Par {
     ///
     /// The children are placed in lines along the `cross` direction. The lines
     /// are stacked along the `main` direction.
-    pub dirs: Gen<Dir>,
-    /// How to align this paragraph in _its_ parent.
-    pub aligns: Gen<Align>,
+    pub flow: Flow,
     /// Whether to expand the cross axis to fill the area or to fit the content.
     pub cross_expansion: Expansion,
     /// The spacing to insert after each line.
     pub line_spacing: Length,
     /// The nodes to be arranged in a paragraph.
     pub children: Vec<LayoutNode>,
+    /// How to align this paragraph in _its_ parent.
+    pub align: BoxAlign,
 }
 
 impl Layout for Par {
@@ -24,17 +24,17 @@ impl Layout for Par {
         for child in &self.children {
             match child.layout(ctx, &layouter.areas) {
                 Layouted::Spacing(spacing) => layouter.push_spacing(spacing),
-                Layouted::Layout(layout, aligns) => {
-                    layouter.push_layout(layout, aligns.cross)
+                Layouted::Layout(layout, align) => {
+                    layouter.push_layout(layout, align.cross)
                 }
-                Layouted::Layouts(layouts, aligns) => {
+                Layouted::Layouts(layouts, align) => {
                     for layout in layouts {
-                        layouter.push_layout(layout, aligns.cross);
+                        layouter.push_layout(layout, align.cross);
                     }
                 }
             }
         }
-        Layouted::Layouts(layouter.finish(), self.aligns)
+        Layouted::Layouts(layouter.finish(), self.align)
     }
 }
 
@@ -48,7 +48,7 @@ struct ParLayouter<'a> {
     par: &'a Par,
     main: SpecAxis,
     cross: SpecAxis,
-    dirs: Gen<Dir>,
+    flow: Flow,
     areas: Areas,
     finished: Vec<BoxLayout>,
     lines: Vec<(Length, BoxLayout, Align)>,
@@ -62,9 +62,9 @@ impl<'a> ParLayouter<'a> {
     fn new(par: &'a Par, areas: Areas) -> Self {
         Self {
             par,
-            main: par.dirs.main.axis(),
-            cross: par.dirs.cross.axis(),
-            dirs: par.dirs,
+            main: par.flow.main.axis(),
+            cross: par.flow.cross.axis(),
+            flow: par.flow,
             areas,
             finished: vec![],
             lines: vec![],
@@ -105,7 +105,7 @@ impl<'a> ParLayouter<'a> {
             }
         }
 
-        let size = layout.size.switch(self.dirs);
+        let size = layout.size.switch(self.flow);
         self.run.push((self.run_size.cross, layout, align));
 
         self.run_size.cross += size.cross;
@@ -119,13 +119,13 @@ impl<'a> ParLayouter<'a> {
             Expansion::Fit => self.run_size.cross,
         });
 
-        let mut output = BoxLayout::new(full_size.switch(self.dirs).to_size());
+        let mut output = BoxLayout::new(full_size.switch(self.flow).to_size());
 
         for (before, layout, align) in std::mem::take(&mut self.run) {
             let child_cross_size = layout.size.get(self.cross);
 
             // Position along the cross axis.
-            let cross = align.resolve(if self.dirs.cross.is_positive() {
+            let cross = align.resolve(if self.flow.cross.is_positive() {
                 let after_with_self = self.run_size.cross - before;
                 before .. full_size.cross - after_with_self
             } else {
@@ -134,7 +134,7 @@ impl<'a> ParLayouter<'a> {
                 full_size.cross - before_with_self .. after
             });
 
-            let pos = Gen::new(Length::ZERO, cross).switch(self.dirs).to_point();
+            let pos = Gen::new(Length::ZERO, cross).switch(self.flow).to_point();
             output.push_layout(pos, layout);
         }
 
@@ -151,26 +151,26 @@ impl<'a> ParLayouter<'a> {
 
     fn finish_area(&mut self) {
         let size = self.lines_size;
-        let mut output = BoxLayout::new(size.switch(self.dirs).to_size());
+        let mut output = BoxLayout::new(size.switch(self.flow).to_size());
 
         for (before, run, cross_align) in std::mem::take(&mut self.lines) {
-            let child_size = run.size.switch(self.dirs);
+            let child_size = run.size.switch(self.flow);
 
             // Position along the main axis.
-            let main = if self.dirs.main.is_positive() {
+            let main = if self.flow.main.is_positive() {
                 before
             } else {
                 size.main - (before + child_size.main)
             };
 
             // Align along the cross axis.
-            let cross = cross_align.resolve(if self.dirs.cross.is_positive() {
+            let cross = cross_align.resolve(if self.flow.cross.is_positive() {
                 Length::ZERO .. size.cross - child_size.cross
             } else {
                 size.cross - child_size.cross .. Length::ZERO
             });
 
-            let pos = Gen::new(main, cross).switch(self.dirs).to_point();
+            let pos = Gen::new(main, cross).switch(self.flow).to_point();
             output.push_layout(pos, run);
         }
 
diff --git a/src/layout/stack.rs b/src/layout/stack.rs
index 7e1bb2c5..9d2540e9 100644
--- a/src/layout/stack.rs
+++ b/src/layout/stack.rs
@@ -1,15 +1,15 @@
 use super::*;
 
-/// A node that stacks and aligns its children.
+/// A node that stacks and align its children.
 #[derive(Debug, Clone, PartialEq)]
 pub struct Stack {
     /// The `main` and `cross` directions of this stack.
     ///
     /// The children are stacked along the `main` direction. The `cross`
     /// direction is required for aligning the children.
-    pub dirs: Gen<Dir>,
+    pub flow: Flow,
     /// How to align this stack in _its_ parent.
-    pub aligns: Gen<Align>,
+    pub align: BoxAlign,
     /// Whether to expand the axes to fill the area or to fit the content.
     pub expansion: Gen<Expansion>,
     /// The nodes to be stacked.
@@ -22,15 +22,15 @@ impl Layout for Stack {
         for child in &self.children {
             match child.layout(ctx, &layouter.areas) {
                 Layouted::Spacing(spacing) => layouter.push_spacing(spacing),
-                Layouted::Layout(layout, aligns) => layouter.push_layout(layout, aligns),
-                Layouted::Layouts(layouts, aligns) => {
+                Layouted::Layout(layout, align) => layouter.push_layout(layout, align),
+                Layouted::Layouts(layouts, align) => {
                     for layout in layouts {
-                        layouter.push_layout(layout, aligns);
+                        layouter.push_layout(layout, align);
                     }
                 }
             }
         }
-        Layouted::Layouts(layouter.finish(), self.aligns)
+        Layouted::Layouts(layouter.finish(), self.align)
     }
 }
 
@@ -43,10 +43,10 @@ impl From<Stack> for LayoutNode {
 struct StackLayouter<'a> {
     stack: &'a Stack,
     main: SpecAxis,
-    dirs: Gen<Dir>,
+    flow: Flow,
     areas: Areas,
     finished: Vec<BoxLayout>,
-    layouts: Vec<(Length, BoxLayout, Gen<Align>)>,
+    layouts: Vec<(Length, BoxLayout, BoxAlign)>,
     used: Gen<Length>,
     ruler: Align,
 }
@@ -55,8 +55,8 @@ impl<'a> StackLayouter<'a> {
     fn new(stack: &'a Stack, areas: Areas) -> Self {
         Self {
             stack,
-            main: stack.dirs.main.axis(),
-            dirs: stack.dirs,
+            main: stack.flow.main.axis(),
+            flow: stack.flow,
             areas,
             finished: vec![],
             layouts: vec![],
@@ -72,8 +72,8 @@ impl<'a> StackLayouter<'a> {
         self.used.main += capped;
     }
 
-    fn push_layout(&mut self, layout: BoxLayout, aligns: Gen<Align>) {
-        if self.ruler > aligns.main {
+    fn push_layout(&mut self, layout: BoxLayout, align: BoxAlign) {
+        if self.ruler > align.main {
             self.finish_area();
         }
 
@@ -87,18 +87,18 @@ impl<'a> StackLayouter<'a> {
             }
         }
 
-        let size = layout.size.switch(self.dirs);
-        self.layouts.push((self.used.main, layout, aligns));
+        let size = layout.size.switch(self.flow);
+        self.layouts.push((self.used.main, layout, align));
 
         *self.areas.current.rem.get_mut(self.main) -= size.main;
         self.used.main += size.main;
         self.used.cross = self.used.cross.max(size.cross);
-        self.ruler = aligns.main;
+        self.ruler = align.main;
     }
 
     fn finish_area(&mut self) {
         let full_size = {
-            let full = self.areas.current.full.switch(self.dirs);
+            let full = self.areas.current.full.switch(self.flow);
             Gen::new(
                 match self.stack.expansion.main {
                     Expansion::Fill => full.main,
@@ -111,13 +111,13 @@ impl<'a> StackLayouter<'a> {
             )
         };
 
-        let mut output = BoxLayout::new(full_size.switch(self.dirs).to_size());
+        let mut output = BoxLayout::new(full_size.switch(self.flow).to_size());
 
-        for (before, layout, aligns) in std::mem::take(&mut self.layouts) {
-            let child_size = layout.size.switch(self.dirs);
+        for (before, layout, align) in std::mem::take(&mut self.layouts) {
+            let child_size = layout.size.switch(self.flow);
 
             // Align along the main axis.
-            let main = aligns.main.resolve(if self.dirs.main.is_positive() {
+            let main = align.main.resolve(if self.flow.main.is_positive() {
                 let after_with_self = self.used.main - before;
                 before .. full_size.main - after_with_self
             } else {
@@ -127,13 +127,13 @@ impl<'a> StackLayouter<'a> {
             });
 
             // Align along the cross axis.
-            let cross = aligns.cross.resolve(if self.dirs.cross.is_positive() {
+            let cross = align.cross.resolve(if self.flow.cross.is_positive() {
                 Length::ZERO .. full_size.cross - child_size.cross
             } else {
                 full_size.cross - child_size.cross .. Length::ZERO
             });
 
-            let pos = Gen::new(main, cross).switch(self.dirs).to_point();
+            let pos = Gen::new(main, cross).switch(self.flow).to_point();
             output.push_layout(pos, layout);
         }
 
diff --git a/src/layout/text.rs b/src/layout/text.rs
index 0ded4f9d..fc319fa5 100644
--- a/src/layout/text.rs
+++ b/src/layout/text.rs
@@ -11,16 +11,16 @@ use crate::shaping;
 pub struct Text {
     /// The text.
     pub text: String,
-    /// The font size.
-    pub font_size: Length,
+    /// How to align this text node in its parent.
+    pub align: BoxAlign,
     /// The text direction.
     pub dir: Dir,
+    /// The font size.
+    pub font_size: Length,
     /// The families used for font fallback.
     pub families: Rc<FallbackTree>,
     /// The font variant,
     pub variant: FontVariant,
-    /// How to align this text node in its parent.
-    pub aligns: Gen<Align>,
 }
 
 impl Layout for Text {
@@ -30,12 +30,12 @@ impl Layout for Text {
             shaping::shape(
                 &mut loader,
                 &self.text,
-                self.font_size,
                 self.dir,
+                self.font_size,
                 &self.families,
                 self.variant,
             ),
-            self.aligns,
+            self.align,
         )
     }
 }
diff --git a/src/library/align.rs b/src/library/align.rs
index 48475601..a54925f0 100644
--- a/src/library/align.rs
+++ b/src/library/align.rs
@@ -32,13 +32,13 @@ pub fn align(mut args: Args, ctx: &mut EvalContext) -> Value {
         .chain(hor.into_iter().map(|align| (Some(SpecAxis::Horizontal), align)))
         .chain(ver.into_iter().map(|align| (Some(SpecAxis::Vertical), align)));
 
-    let aligns = dedup_aligns(ctx, iter);
-    if aligns.main != ctx.state.aligns.main {
+    let align = dedup_aligns(ctx, iter);
+    if align.main != ctx.state.align.main {
         ctx.end_par_group();
         ctx.start_par_group();
     }
 
-    ctx.state.aligns = aligns;
+    ctx.state.align = align;
 
     if let Some(body) = body {
         body.eval(ctx);
@@ -52,17 +52,17 @@ pub fn align(mut args: Args, ctx: &mut EvalContext) -> Value {
 fn dedup_aligns(
     ctx: &mut EvalContext,
     iter: impl Iterator<Item = (Option<SpecAxis>, Spanned<AlignArg>)>,
-) -> Gen<Align> {
-    let mut aligns = ctx.state.aligns;
-    let mut had = Gen::new(false, false);
+) -> BoxAlign {
+    let mut alignments = ctx.state.align;
+    let mut had = Gen::uniform(false);
     let mut had_center = false;
 
     for (axis, Spanned { v: align, span }) in iter {
         // Check whether we know which axis this alignment belongs to.
         if let Some(axis) = axis {
             // We know the axis.
-            let gen_axis = axis.switch(ctx.state.dirs);
-            let gen_align = align.switch(ctx.state.dirs);
+            let gen_axis = axis.switch(ctx.state.flow);
+            let gen_align = align.switch(ctx.state.flow);
 
             if align.axis().map_or(false, |a| a != axis) {
                 ctx.diag(error!(
@@ -72,7 +72,7 @@ fn dedup_aligns(
             } else if had.get(gen_axis) {
                 ctx.diag(error!(span, "duplicate alignment for {} axis", axis));
             } else {
-                *aligns.get_mut(gen_axis) = gen_align;
+                *alignments.get_mut(gen_axis) = gen_align;
                 *had.get_mut(gen_axis) = true;
             }
         } else {
@@ -85,8 +85,8 @@ fn dedup_aligns(
             } else if had_center {
                 // Both this and the previous one are unspecified `center`
                 // alignments. Both axes should be centered.
-                aligns = Gen::new(Align::Center, Align::Center);
-                had = Gen::new(true, true);
+                alignments = BoxAlign::new(Align::Center, Align::Center);
+                had = Gen::uniform(true);
             } else {
                 had_center = true;
             }
@@ -96,10 +96,10 @@ fn dedup_aligns(
         // alignment.
         if had_center && (had.main || had.cross) {
             if had.main {
-                aligns.cross = Align::Center;
+                alignments.cross = Align::Center;
                 had.cross = true;
             } else {
-                aligns.main = Align::Center;
+                alignments.main = Align::Center;
                 had.main = true;
             }
             had_center = false;
@@ -109,10 +109,10 @@ fn dedup_aligns(
     // If center has not been flushed by now, it is the only argument and then
     // we default to applying it to the cross axis.
     if had_center {
-        aligns.cross = Align::Center;
+        alignments.cross = Align::Center;
     }
 
-    aligns
+    alignments
 }
 
 /// An alignment argument.
@@ -143,7 +143,7 @@ impl AlignArg {
 impl Switch for AlignArg {
     type Other = Align;
 
-    fn switch(self, dirs: Gen<Dir>) -> Self::Other {
+    fn switch(self, flow: Flow) -> Self::Other {
         let get = |dir: Dir, at_positive_start| {
             if dir.is_positive() == at_positive_start {
                 Align::Start
@@ -152,12 +152,12 @@ impl Switch for AlignArg {
             }
         };
 
-        let dirs = dirs.switch(dirs);
+        let flow = flow.switch(flow);
         match self {
-            Self::Left => get(dirs.horizontal, true),
-            Self::Right => get(dirs.horizontal, false),
-            Self::Top => get(dirs.vertical, true),
-            Self::Bottom => get(dirs.vertical, false),
+            Self::Left => get(flow.horizontal, true),
+            Self::Right => get(flow.horizontal, false),
+            Self::Top => get(flow.vertical, true),
+            Self::Bottom => get(flow.vertical, false),
             Self::Center => Align::Center,
         }
     }
diff --git a/src/library/boxed.rs b/src/library/boxed.rs
index 24880998..3d7214ae 100644
--- a/src/library/boxed.rs
+++ b/src/library/boxed.rs
@@ -15,8 +15,8 @@ pub fn boxed(mut args: Args, ctx: &mut EvalContext) -> Value {
     let height = args.get::<_, Linear>(ctx, "height");
     args.done(ctx);
 
-    let dirs = ctx.state.dirs;
-    let aligns = ctx.state.aligns;
+    let flow = ctx.state.flow;
+    let align = ctx.state.align;
 
     ctx.start_content_group();
     body.eval(ctx);
@@ -26,14 +26,14 @@ pub fn boxed(mut args: Args, ctx: &mut EvalContext) -> Value {
         width,
         height,
         child: LayoutNode::dynamic(Stack {
-            dirs,
-            children,
-            aligns,
+            flow,
+            align,
             expansion: Spec::new(
                 Expansion::fill_if(width.is_some()),
                 Expansion::fill_if(height.is_some()),
             )
-            .switch(dirs),
+            .switch(flow),
+            children,
         }),
     });
 
diff --git a/src/library/spacing.rs b/src/library/spacing.rs
index 44997739..d6d0d7b0 100644
--- a/src/library/spacing.rs
+++ b/src/library/spacing.rs
@@ -26,7 +26,7 @@ fn spacing(mut args: Args, ctx: &mut EvalContext, axis: SpecAxis) -> Value {
     if let Some(linear) = spacing {
         let amount = linear.resolve(ctx.state.font.font_size());
         let spacing = Spacing { amount, softness: Softness::Hard };
-        if ctx.state.dirs.main.axis() == axis {
+        if ctx.state.flow.main.axis() == axis {
             ctx.end_par_group();
             ctx.push(spacing);
             ctx.start_par_group();
diff --git a/src/shaping.rs b/src/shaping.rs
index a14c48a4..45ab6ff8 100644
--- a/src/shaping.rs
+++ b/src/shaping.rs
@@ -64,8 +64,8 @@ impl Debug for Shaped {
 pub fn shape(
     loader: &mut FontLoader,
     text: &str,
-    font_size: Length,
     dir: Dir,
+    font_size: Length,
     fallback: &FallbackTree,
     variant: FontVariant,
 ) -> BoxLayout {