Progressing stack layouter 🚊

14 files changed, 250 insertions, 324 deletions

diff --git a/src/func/mod.rs b/src/func/mod.rs
index 53cfece0..c8cf23c6 100644
--- a/src/func/mod.rs
+++ b/src/func/mod.rs
@@ -14,7 +14,7 @@ pub mod prelude {
     pub use crate::func::{Scope, ParseFunc, LayoutFunc, Command, Commands};
     pub use crate::layout::{
         layout_tree, Layout, MultiLayout,
-        LayoutContext, LayoutSpace, LayoutSpaces,
+        LayoutContext, LayoutSpace, LayoutSpaces, LayoutExpansion,
         LayoutAxes, Axis, GenericAxisKind, SpecificAxisKind,
         LayoutAlignment, Alignment,
         SpacingKind, LayoutResult,
diff --git a/src/layout/actions.rs b/src/layout/actions.rs
index 01abc0ba..b0d2c21d 100644
--- a/src/layout/actions.rs
+++ b/src/layout/actions.rs
@@ -68,8 +68,8 @@ impl LayoutActions {
     pub fn new() -> LayoutActions {
         LayoutActions {
             actions: vec![],
-            origin: Size2D::zero(),
-            active_font: (std::usize::MAX, Size::zero()),
+            origin: Size2D::ZERO,
+            active_font: (std::usize::MAX, Size::ZERO),
             next_pos: None,
             next_font: None,
         }
diff --git a/src/layout/flex.rs b/src/layout/flex.rs
index d984860a..fc1a09c0 100644
--- a/src/layout/flex.rs
+++ b/src/layout/flex.rs
@@ -33,7 +33,7 @@ impl FlexLine {
         FlexLine {
             usable,
             actions: LayoutActions::new(),
-            combined_dimensions: Size2D::zero(),
+            combined_dimensions: Size2D::ZERO,
         }
     }
 }
@@ -51,7 +51,7 @@ impl PartialLine {
         PartialLine {
             usable,
             content: vec![],
-            dimensions: Size2D::zero(),
+            dimensions: Size2D::ZERO,
             space: LastSpacing::Hard,
         }
     }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index c34d881e..d6bb0d6d 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -1,7 +1,6 @@
 //! The core layouting engine.
 
 use std::io::{self, Write};
-
 use smallvec::SmallVec;
 
 use toddle::query::{FontClass, SharedFontLoader};
@@ -91,7 +90,7 @@ pub struct LayoutSpace {
     /// Whether to expand the dimensions of the resulting layout to the full
     /// dimensions of this space or to shrink them to fit the content for the
     /// horizontal and vertical axis.
-    pub expand: (bool, bool),
+    pub expand: LayoutExpansion,
 }
 
 impl LayoutSpace {
@@ -110,12 +109,25 @@ impl LayoutSpace {
     pub fn usable_space(&self) -> LayoutSpace {
         LayoutSpace {
             dimensions: self.usable(),
-            padding: SizeBox::zero(),
-            expand: (false, false),
+            padding: SizeBox::ZERO,
+            expand: LayoutExpansion::new(false, false),
         }
     }
 }
 
+/// Whether to fit to content or expand to the space's size.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub struct LayoutExpansion {
+    pub horizontal: bool,
+    pub vertical: bool,
+}
+
+impl LayoutExpansion {
+    pub fn new(horizontal: bool, vertical: bool) -> LayoutExpansion {
+        LayoutExpansion { horizontal, vertical }
+    }
+}
+
 /// The axes along which the content is laid out.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct LayoutAxes {
@@ -132,28 +144,8 @@ impl LayoutAxes {
         LayoutAxes { primary, secondary }
     }
 
-    /// Returns the generalized version of a `Size2D` dependent on
-    /// the layouting axes, that is:
-    /// - The x coordinate describes the primary axis instead of the horizontal one.
-    /// - The y coordinate describes the secondary axis instead of the vertical one.
-    pub fn generalize(&self, size: Size2D) -> Size2D {
-        if self.primary.is_horizontal() {
-            size
-        } else {
-            Size2D { x: size.y, y: size.x }
-        }
-    }
-
-    /// Returns the specialized version of this generalized Size2D.
-    /// (Inverse to `generalized`).
-    pub fn specialize(&self, size: Size2D) -> Size2D {
-        // In fact, generalized is its own inverse. For reasons of clarity
-        // at the call site, we still have this second function.
-        self.generalize(size)
-    }
-
     /// Return the specified generic axis.
-    pub fn get_generic(&self, axis: GenericAxisKind) -> Axis {
+    pub fn generic(&self, axis: GenericAxisKind) -> Axis {
         match axis {
             GenericAxisKind::Primary => self.primary,
             GenericAxisKind::Secondary => self.secondary,
@@ -161,8 +153,8 @@ impl LayoutAxes {
     }
 
     /// Return the specified specific axis.
-    pub fn get_specific(&self, axis: SpecificAxisKind) -> Axis {
-        self.get_generic(axis.generic(*self))
+    pub fn specific(&self, axis: SpecificAxisKind) -> Axis {
+        self.generic(axis.generic(*self))
     }
 
     /// Returns the generic axis kind which is the horizontal axis.
@@ -222,6 +214,15 @@ impl LayoutAxes {
     }
 }
 
+impl Default for LayoutAxes {
+    fn default() -> LayoutAxes {
+        LayoutAxes {
+            primary: Axis::LeftToRight,
+            secondary: Axis::TopToBottom,
+        }
+    }
+}
+
 /// Directions along which content is laid out.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum Axis {
@@ -318,7 +319,7 @@ impl SpecificAxisKind {
 }
 
 /// The place to put a layout in a container.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Default, Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct LayoutAlignment {
     pub primary: Alignment,
     pub secondary: Alignment,
@@ -331,7 +332,7 @@ impl LayoutAlignment {
 }
 
 /// Where to align content.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub enum Alignment {
     Origin,
     Center,
@@ -349,6 +350,12 @@ impl Alignment {
     }
 }
 
+impl Default for Alignment {
+    fn default() -> Alignment {
+        Alignment::Origin
+    }
+}
+
 /// Whitespace between boxes with different interaction properties.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum SpacingKind {
@@ -377,7 +384,7 @@ impl LastSpacing {
     fn soft_or_zero(&self) -> Size {
         match self {
             LastSpacing::Soft(space, _) => *space,
-            _ => Size::zero(),
+            _ => Size::ZERO,
         }
     }
 }
diff --git a/src/layout/stack.rs b/src/layout/stack.rs
index b11aee79..2e4f2d3a 100644
--- a/src/layout/stack.rs
+++ b/src/layout/stack.rs
@@ -1,4 +1,5 @@
 use smallvec::smallvec;
+use crate::size::{min, max};
 use super::*;
 
 /// The stack layouter arranges boxes stacked onto each other.
@@ -13,9 +14,6 @@ pub struct StackLayouter {
     layouts: MultiLayout,
     /// The currently active layout space.
     space: Space,
-    /// The remaining subspace of the active space. Whenever the layouting axes
-    /// change a new subspace is started.
-    sub: Subspace,
 }
 
 /// The context for stack layouting.
@@ -37,40 +35,20 @@ struct Space {
     /// Whether to add the layout for this space even if it would be empty.
     hard: bool,
     /// The so-far accumulated subspaces.
-    subs: Vec<Subspace>,
-}
-
-/// A part of a space with fixed axes and secondary alignment.
-#[derive(Debug, Clone)]
-struct Subspace {
-    /// The axes along which contents in this subspace are laid out.
-    axes: LayoutAxes,
-    /// The secondary alignment of this subspace.
-    alignment: Alignment,
-    /// The beginning of this subspace in the parent space (specialized).
-    origin: Size2D,
-    /// The total usable space of this subspace (generalized).
-    usable: Size2D,
-    /// The used size of this subspace (generalized), with
-    /// - `x` being the maximum of the primary size of all boxes.
-    /// - `y` being the total extent of all boxes and space in the secondary
-    ///   direction.
+    layouts: Vec<(LayoutAxes, Layout)>,
+    /// The specialized size of this subspace.
     size: Size2D,
-    /// The so-far accumulated layouts.
-    layouts: Vec<LayoutEntry>,
+    /// The specialized remaining space.
+    usable: Size2D,
+    /// The specialized extra-needed dimensions to affect the size at all.
+    extra: Size2D,
+    /// The maximal secondary alignment for both specialized axes (horizontal,
+    /// vertical).
+    alignment: (Alignment, Alignment),
     /// The last added spacing if the last added thing was spacing.
     last_spacing: LastSpacing,
 }
 
-/// A single layout in a subspace.
-#[derive(Debug, Clone)]
-struct LayoutEntry {
-    /// The offset of this box on the secondary axis.
-    offset: Size,
-    /// The layout itself.
-    layout: Layout,
-}
-
 impl StackLayouter {
     /// Create a new stack layouter.
     pub fn new(ctx: StackContext) -> StackLayouter {
@@ -80,55 +58,55 @@ impl StackLayouter {
         StackLayouter {
             ctx,
             layouts: MultiLayout::new(),
-            space: Space::new(0, true),
-            sub: Subspace::new(axes, Alignment::Origin, space.start(), space.usable()),
+            space: Space::new(0, true, space.usable()),
         }
     }
 
     /// Add a layout to the stack.
     pub fn add(&mut self, layout: Layout) -> LayoutResult<()> {
-        if layout.alignment.secondary != self.sub.alignment {
-            self.finish_subspace(layout.alignment.secondary);
+        // If the layout's secondary alignment is less than what we have already
+        // seen, it needs to go into the next space.
+        if layout.alignment.secondary < *self.secondary_alignment() {
+            self.finish_space(true);
         }
 
+        // We want the new maximal alignment and since the layout's secondary
+        // alignment is at least the previous maximum, we just take it.
+        *self.secondary_alignment() = layout.alignment.secondary;
+
         // Add a cached soft space if there is one.
-        if let LastSpacing::Soft(space, _) = self.sub.last_spacing {
-            self.add_spacing(space, SpacingKind::Hard);
+        if let LastSpacing::Soft(spacing, _) = self.space.last_spacing {
+            self.add_spacing(spacing, SpacingKind::Hard);
         }
 
-        // The new primary size is the maximum of the current one and the
-        // layout's one while the secondary size grows by the layout's size.
-        let size = self.ctx.axes.generalize(layout.dimensions);
-        let mut new_size = Size2D {
-            x: crate::size::max(self.sub.size.x, size.x),
-            y: self.sub.size.y + size.y
-        };
-
-        // Find the first (sub-)space that fits the layout.
-        while !self.sub.usable.fits(new_size) {
+        // Find the first space that fits the layout.
+        while !self.space.usable.fits(layout.dimensions) {
             if self.space_is_last() && self.space_is_empty() {
-                error!("box of size {} does not fit into remaining stack of size {}",
-                    size, self.sub.usable - Size2D::with_y(self.sub.size.y));
+                error!("box of size {} does not fit into remaining usable size {}",
+                    layout.dimensions, self.space.usable);
             }
 
             self.finish_space(true);
-            new_size = size;
         }
 
-        // The secondary offset from the start of layouts is given by the
-        // current primary size of the subspace.
-        let offset = self.sub.size.y;
-        self.sub.layouts.push(LayoutEntry {
-            offset,
-            layout,
-        });
+        let axes = self.ctx.axes;
+        let dimensions = layout.dimensions.generalized(axes);
+
+        let mut size = self.space.size.generalized(axes);
+        let mut extra = self.space.extra.generalized(axes);
+
+        size.x += max(dimensions.x - extra.x, Size::ZERO);
+        size.y += max(dimensions.y - extra.y, Size::ZERO);
+        extra.x = max(extra.x, dimensions.x);
+        extra.y = max(extra.y - dimensions.y, Size::ZERO);
 
-        // The new size of the subspace is the previously calculated
-        // combination.
-        self.sub.size = new_size;
+        self.space.size = size.specialized(axes);
+        self.space.extra = extra.specialized(axes);
 
-        // Since the last item was a box, last spacing is reset to `None`.
-        self.sub.last_spacing = LastSpacing::None;
+        *self.space.usable.secondary_mut(axes) -= dimensions.y;
+
+        self.space.layouts.push((self.ctx.axes, layout));
+        self.space.last_spacing = LastSpacing::None;
 
         Ok(())
     }
@@ -144,30 +122,34 @@ impl StackLayouter {
     }
 
     /// Add secondary spacing to the stack.
-    pub fn add_spacing(&mut self, space: Size, kind: SpacingKind) {
+    pub fn add_spacing(&mut self, mut spacing: Size, kind: SpacingKind) {
         match kind {
             // A hard space is directly added to the sub's size.
             SpacingKind::Hard => {
-                if self.sub.size.y + space > self.sub.usable.y {
-                    self.sub.size.y = self.sub.usable.y;
-                } else {
-                    self.sub.size.y += space;
-                }
+                // Reduce the spacing such that definitely fits.
+                spacing.min_eq(self.space.usable.secondary(self.ctx.axes));
 
-                self.sub.last_spacing = LastSpacing::Hard;
+                self.add(Layout {
+                    dimensions: Size2D::with_y(spacing).specialized(self.ctx.axes),
+                    baseline: None,
+                    alignment: LayoutAlignment::default(),
+                    actions: vec![],
+                }).expect("spacing should fit");
+
+                self.space.last_spacing = LastSpacing::Hard;
             }
 
             // A hard space is cached if it is not consumed by a hard space or
             // previous soft space with higher level.
             SpacingKind::Soft(level) => {
-                let consumes = match self.sub.last_spacing {
+                let consumes = match self.space.last_spacing {
                     LastSpacing::None => true,
                     LastSpacing::Soft(_, prev) if level < prev => true,
                     _ => false,
                 };
 
                 if consumes {
-                    self.sub.last_spacing = LastSpacing::Soft(space, level);
+                    self.space.last_spacing = LastSpacing::Soft(spacing, level);
                 }
             }
         }
@@ -178,13 +160,7 @@ impl StackLayouter {
     /// This starts a new subspace (if the axes are actually different from the
     /// current ones).
     pub fn set_axes(&mut self, axes: LayoutAxes) {
-        if axes != self.ctx.axes {
-            self.finish_subspace(Alignment::Origin);
-
-            let (origin, usable) = self.remaining_subspace();
-            self.sub = Subspace::new(axes, Alignment::Origin, origin, usable);
-            self.ctx.axes = axes;
-        }
+        self.ctx.axes = axes;
     }
 
     /// Change the layouting spaces to use.
@@ -206,9 +182,9 @@ impl StackLayouter {
     /// out into these spaces, it will fit into this stack.
     pub fn remaining(&self) -> LayoutSpaces {
         let mut spaces = smallvec![LayoutSpace {
-            dimensions: self.remaining_subspace().1,
-            padding: SizeBox::zero(),
-            expand: (false, false),
+            dimensions: self.space.usable,
+            padding: SizeBox::ZERO,
+            expand: LayoutExpansion::new(false, false),
         }];
 
         for space in &self.ctx.spaces[self.next_space()..] {
@@ -220,12 +196,12 @@ impl StackLayouter {
 
     /// The usable size along the primary axis.
     pub fn primary_usable(&self) -> Size {
-        self.sub.usable.x
+        self.space.usable.primary(self.ctx.axes)
     }
 
     /// Whether the current layout space (not subspace) is empty.
     pub fn space_is_empty(&self) -> bool {
-        self.subspace_is_empty() && self.space.subs.is_empty()
+        self.space.size == Size2D::ZERO && self.space.layouts.is_empty()
     }
 
     /// Whether the current layout space is the last is the followup list.
@@ -243,117 +219,36 @@ impl StackLayouter {
 
     /// Finish the current space and start a new one.
     pub fn finish_space(&mut self, hard: bool) {
-        self.finish_subspace(Alignment::Origin);
-
-        println!();
-        println!("FINISHING SPACE:");
-        println!();
-
         let space = self.ctx.spaces[self.space.index];
-        let mut subs = std::mem::replace(&mut self.space.subs, vec![]);
 
-        // ---------------------------------------------------------------------
-        // Compute the size of the whole space.
         let usable = space.usable();
-        let mut max = Size2D {
-            x: if space.expand.0 { usable.x } else { Size::zero() },
-            y: if space.expand.1 { usable.y } else { Size::zero() },
-        };
-
-        // The total size is determined by the maximum position + extent of one
-        // of the boxes.
-        for sub in &subs {
-            max.max_eq(sub.origin + sub.axes.specialize(sub.size));
-        }
+        if space.expand.horizontal { self.space.size.x = usable.x; }
+        if space.expand.vertical   { self.space.size.y = usable.y; }
 
-        let dimensions = max.padded(space.padding);
-
-        println!("WITH DIMENSIONS: {}", dimensions);
-
-        println!("SUBS: {:#?}", subs);
-
-        // ---------------------------------------------------------------------
-        // Justify the boxes according to their alignment and give each box
-        // the appropriate origin and usable space.
-
-        // use Alignment::*;
-
-        for sub in &mut subs {
-            // The usable width should not exceed the total usable width
-            // (previous value) or the maximum width of the layout as a whole.
-            sub.usable.x = crate::size::min(
-                sub.usable.x,
-                sub.axes.specialize(max - sub.origin).x,
-            );
-
-            sub.usable.y = sub.size.y;
-        }
+        let dimensions = self.space.size.padded(space.padding);
 
-        // if space.expand.1 {
-        //     let height = subs.iter().map(|sub| sub.size.y).sum();
-        //     let centers = subs.iter()
-        //         .filter(|sub| sub.alignment == Alignment::Center)
-        //         .count()
-        //         .max(1);
-
-        //     let grow = max.y - height;
-        //     let center_grow = grow / (centers as i32);
-
-        //     println!("center grow = {}", center_grow);
-
-        //     let mut offset = Size::zero();
-        //     for sub in &mut subs {
-        //         sub.origin.y += offset;
-        //         if sub.alignment == Center {
-        //             sub.usable.y += center_grow;
-        //             offset += center_grow;
-        //         }
-        //     }
-
-        //     if let Some(last) = subs.last_mut() {
-        //         last.usable.y += grow - offset;
-        //     }
-        // }
-
-        // ---------------------------------------------------------------------
-        // Do the thing
-
-        // Add a debug box with this boxes size.
         let mut actions = LayoutActions::new();
         actions.add(LayoutAction::DebugBox(dimensions));
 
-        for sub in subs {
-            let LayoutAxes { primary, secondary } = sub.axes;
-
-            // The factor is +1 if the axis is positive and -1 otherwise.
-            let factor = sub.axes.secondary.factor();
-
-            // The anchor is the position of the origin-most point of the
-            // layout.
-            let anchor =
-                sub.usable.y.anchor(sub.alignment, secondary.is_positive())
-                - factor * sub.size.y.anchor(sub.alignment, true);
+        let mut cursor = space.start();
+        for (axes, layout) in std::mem::replace(&mut self.space.layouts, vec![]) {
+            let LayoutAxes { primary, secondary } = axes;
+            let size = layout.dimensions.specialized(axes);
+            let alignment = layout.alignment.primary;
 
-            for entry in sub.layouts {
-                let layout = entry.layout;
-                let alignment = layout.alignment.primary;
-                let size = sub.axes.generalize(layout.dimensions);
+            let primary_usable = self.space.size.primary(axes) - cursor.primary(axes);
 
-                let x =
-                    sub.usable.x.anchor(alignment, primary.is_positive())
-                    - size.x.anchor(alignment, primary.is_positive());
+            let position = Size2D {
+                x: cursor.primary(axes)
+                   + primary_usable.anchor(alignment, primary.is_positive())
+                   - size.x.anchor(alignment, primary.is_positive()),
+                y: cursor.secondary(axes),
+            };
 
-                let y = anchor
-                    + factor * entry.offset
-                    - size.y.anchor(Alignment::Origin, secondary.is_positive());
-
-                let pos = sub.origin + sub.axes.specialize(Size2D::new(x, y));
-                actions.add_layout(pos, layout);
-            }
+            actions.add_layout(position.specialized(axes), layout);
+            *cursor.secondary_mut(axes) += size.y;
         }
 
-        // ---------------------------------------------------------------------
-
         self.layouts.push(Layout {
             dimensions,
             baseline: None,
@@ -365,14 +260,9 @@ impl StackLayouter {
     }
 
     /// Start a new space with the given index.
-    fn start_space(&mut self, space: usize, hard: bool) {
-        // Start the space.
-        self.space = Space::new(space, hard);
-
-        // Start the subspace.
-        let space = self.ctx.spaces[space];
-        let axes = self.ctx.axes;
-        self.sub = Subspace::new(axes, Alignment::Origin, space.start(), space.usable());
+    fn start_space(&mut self, index: usize, hard: bool) {
+        let space = self.ctx.spaces[index];
+        self.space = Space::new(index, hard, space.usable());
     }
 
     /// The index of the next space.
@@ -380,62 +270,25 @@ impl StackLayouter {
         (self.space.index + 1).min(self.ctx.spaces.len() - 1)
     }
 
-    /// Finish the current subspace.
-    fn finish_subspace(&mut self, new_alignment: Alignment) {
-        let empty = self.subspace_is_empty();
-
-        let axes = self.ctx.axes;
-        let (origin, usable) = self.remaining_subspace();
-        let new_sub = Subspace::new(axes, new_alignment, origin, usable);
-        let sub = std::mem::replace(&mut self.sub, new_sub);
-
-        if !empty {
-            self.space.subs.push(sub);
+    // Access the secondary alignment in the current system of axes.
+    fn secondary_alignment(&mut self) -> &mut Alignment {
+        match self.ctx.axes.primary.is_horizontal() {
+            true => &mut self.space.alignment.1,
+            false => &mut self.space.alignment.0,
         }
     }
-
-    /// The remaining sub
-    fn remaining_subspace(&self) -> (Size2D, Size2D) {
-        let offset = self.sub.size.y + self.sub.last_spacing.soft_or_zero();
-
-        let new_origin = self.sub.origin + match self.ctx.axes.secondary.is_positive() {
-            true => self.ctx.axes.specialize(Size2D::with_y(offset)),
-            false => Size2D::zero(),
-        };
-
-        let new_usable = self.ctx.axes.specialize(Size2D {
-            x: self.sub.usable.x,
-            y: self.sub.usable.y - offset,
-        });
-
-        (new_origin, new_usable)
-    }
-
-    /// Whether the current layout space (not subspace) is empty.
-    fn subspace_is_empty(&self) -> bool {
-        self.sub.layouts.is_empty() && self.sub.size == Size2D::zero()
-    }
 }
 
 impl Space {
-    fn new(index: usize, hard: bool) -> Space {
+    fn new(index: usize, hard: bool, usable: Size2D) -> Space {
         Space {
             index,
             hard,
-            subs: vec![],
-        }
-    }
-}
-
-impl Subspace {
-    fn new(axes: LayoutAxes, alignment: Alignment, origin: Size2D, usable: Size2D) -> Subspace {
-        Subspace {
-            axes,
-            alignment,
-            origin,
-            usable: axes.generalize(usable),
-            size: Size2D::zero(),
             layouts: vec![],
+            size: Size2D::ZERO,
+            usable,
+            extra: Size2D::ZERO,
+            alignment: (Alignment::Origin, Alignment::Origin),
             last_spacing: LastSpacing::Hard,
         }
     }
diff --git a/src/layout/text.rs b/src/layout/text.rs
index b5ff192e..30620c0b 100644
--- a/src/layout/text.rs
+++ b/src/layout/text.rs
@@ -42,7 +42,7 @@ impl<'a, 'p> TextLayouter<'a, 'p> {
             actions: LayoutActions::new(),
             buffer: String::new(),
             active_font: std::usize::MAX,
-            width: Size::zero(),
+            width: Size::ZERO,
             classes: ctx.style.classes.clone(),
         }
     }
diff --git a/src/layout/tree.rs b/src/layout/tree.rs
index 94a50eea..d620739d 100644
--- a/src/layout/tree.rs
+++ b/src/layout/tree.rs
@@ -116,7 +116,7 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
                     LayoutSpace {
                         dimensions: style.dimensions,
                         padding: style.margins,
-                        expand: (true, true),
+                        expand: LayoutExpansion::new(true, true),
                     }
                 ], true);
             }
diff --git a/src/lib.rs b/src/lib.rs
index f2ebd572..368d0cda 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -27,7 +27,7 @@ use toddle::Error as FontError;
 use crate::func::Scope;
 use crate::layout::{layout_tree, MultiLayout, LayoutContext};
 use crate::layout::{LayoutAxes, LayoutAlignment, Axis, Alignment};
-use crate::layout::{LayoutResult, LayoutSpace};
+use crate::layout::{LayoutResult, LayoutSpace, LayoutExpansion};
 use crate::syntax::{parse, SyntaxTree, ParseContext, Span, ParseResult};
 use crate::style::{LayoutStyle, PageStyle, TextStyle};
 
@@ -98,11 +98,11 @@ impl<'p> Typesetter<'p> {
                 style: &self.style,
                 spaces: smallvec![LayoutSpace {
                     dimensions: self.style.page.dimensions,
-                    expand: (true, true),
+                    expand: LayoutExpansion::new(true, true),
                     padding: self.style.page.margins,
                 }],
-                axes: LayoutAxes::new(Axis::LeftToRight, Axis::TopToBottom),
-                alignment: LayoutAlignment::new(Alignment::Origin, Alignment::Origin),
+                axes: LayoutAxes::default(),
+                alignment: LayoutAlignment::default(),
             },
         )?)
     }
diff --git a/src/library/boxed.rs b/src/library/boxed.rs
index d3d5b591..7c0ea0c6 100644
--- a/src/library/boxed.rs
+++ b/src/library/boxed.rs
@@ -11,7 +11,7 @@ function! {
 
     parse(args, body, ctx) {
         Boxed {
-            body: parse!(expected: body, ctx),
+            body: parse!(optional: body, ctx).unwrap_or(SyntaxTree::new()),
             map: ExtentMap::new(&mut args, false)?,
         }
     }
@@ -22,8 +22,8 @@ function! {
         let space = &mut ctx.spaces[0];
         self.map.apply_with(ctx.axes, |axis, p| {
             let entity = match axis {
-                Horizontal => { space.expand.0 = true; &mut space.dimensions.x },
-                Vertical => { space.expand.1 = true; &mut space.dimensions.y },
+                Horizontal => { space.expand.horizontal = true; &mut space.dimensions.x },
+                Vertical => { space.expand.vertical = true; &mut space.dimensions.y },
             };
 
             *entity = p.concretize(*entity)
diff --git a/src/library/keys.rs b/src/library/keys.rs
index c7e34839..969d92be 100644
--- a/src/library/keys.rs
+++ b/src/library/keys.rs
@@ -118,7 +118,7 @@ impl AlignmentKey {
         use AlignmentKey::*;
         use SpecificAxisKind::*;
 
-        let positive = axes.get_specific(axis).is_positive();
+        let positive = axes.specific(axis).is_positive();
         match (self, axis, positive) {
             (Origin, Horizontal, true) | (End, Horizontal, false) => Left,
             (End, Horizontal, true) | (Origin, Horizontal, false) => Right,
diff --git a/src/library/maps.rs b/src/library/maps.rs
index c89d46cb..077ebc5e 100644
--- a/src/library/maps.rs
+++ b/src/library/maps.rs
@@ -86,8 +86,8 @@ impl<E: ExpressionKind + Copy> ExtentMap<E> {
             let key = match arg.v.key.v.0.as_str() {
                 "width" | "w" => AxisKey::Horizontal,
                 "height" | "h" => AxisKey::Vertical,
-                "primary-size" => AxisKey::Primary,
-                "secondary-size" => AxisKey::Secondary,
+                "primary-size" | "ps" => AxisKey::Primary,
+                "secondary-size" | "ss" => AxisKey::Secondary,
                 _ => if enforce {
                     error!("expected dimension")
                 } else {
diff --git a/src/size.rs b/src/size.rs
index 4a81a65d..71c5458f 100644
--- a/src/size.rs
+++ b/src/size.rs
@@ -6,7 +6,7 @@ use std::iter::Sum;
 use std::ops::*;
 use std::str::FromStr;
 
-use crate::layout::Alignment;
+use crate::layout::{LayoutAxes, Alignment};
 
 /// A general space type.
 #[derive(Copy, Clone, PartialEq)]
@@ -51,8 +51,11 @@ pub type FSize = ScaleSize;
 pub type PSize = ScaleSize;
 
 impl Size {
+    /// The zeroed size.
+    pub const ZERO: Size = Size { points: 0.0 };
+
     /// Create a zeroed size.
-    pub fn zero() -> Size { Size { points: 0.0 } }
+    pub fn zero() -> Size { Size::ZERO }
 
     /// Create a size from an amount of points.
     pub fn pt(points: f32) -> Size { Size { points } }
@@ -83,12 +86,17 @@ impl Size {
         *self = max(*self, other);
     }
 
+    /// Set this size to the minimum of itself and the other size.
+    pub fn min_eq(&mut self, other: Size) {
+        *self = min(*self, other);
+    }
+
     /// The specialized anchor position for an item with the given alignment in a
     /// container with a given size along the given axis.
     pub fn anchor(&self, alignment: Alignment, positive: bool) -> Size {
         use Alignment::*;
         match (positive, alignment) {
-            (true, Origin) | (false, End) => Size::zero(),
+            (true, Origin) | (false, End) => Size::ZERO,
             (_, Center) => *self / 2,
             (true, End) | (false, Origin) => *self,
         }
@@ -97,6 +105,9 @@ impl Size {
 }
 
 impl Size2D {
+    /// The zeroed 2D-size.
+    pub const ZERO: Size2D = Size2D { x: Size::ZERO, y: Size::ZERO };
+
     /// Create a new 2D-size from two sizes.
     pub fn new(x: Size, y: Size) -> Size2D {
         Size2D { x, y }
@@ -104,7 +115,7 @@ impl Size2D {
 
     /// Create a 2D-size with both sizes set to zero.
     pub fn zero() -> Size2D {
-        Size2D { x: Size::zero(), y: Size::zero() }
+        Size2D::ZERO
     }
 
     /// Create a 2D-size with `x` and `y` set to the same value `s`.
@@ -114,12 +125,63 @@ impl Size2D {
 
     /// Create a new 2D-size with `x` set to a value and `y` zero.
     pub fn with_x(x: Size) -> Size2D {
-        Size2D { x, y: Size::zero() }
+        Size2D { x, y: Size::ZERO }
     }
 
     /// Create a new 2D-size with `y` set to a value and `x` zero.
     pub fn with_y(y: Size) -> Size2D {
-        Size2D { x: Size::zero(), y }
+        Size2D { x: Size::ZERO, y }
+    }
+
+    /// Access the primary size of this 2D-size.
+    pub fn primary(&self, axes: LayoutAxes) -> Size {
+        match axes.primary.is_horizontal() {
+            true => self.x,
+            false => self.y,
+        }
+    }
+
+    /// Access the secondary size of this 2D-size.
+    pub fn secondary(&self, axes: LayoutAxes) -> Size {
+        match axes.primary.is_horizontal() {
+            true => self.y,
+            false => self.x,
+        }
+    }
+
+    /// Access the primary size of this 2D-size.
+    pub fn primary_mut(&mut self, axes: LayoutAxes) -> &mut Size {
+        match axes.primary.is_horizontal() {
+            true => &mut self.x,
+            false => &mut self.y,
+        }
+    }
+
+    /// Access the secondary size of this 2D-size.
+    pub fn secondary_mut(&mut self, axes: LayoutAxes) -> &mut Size {
+        match axes.primary.is_horizontal() {
+            true => &mut self.y,
+            false => &mut self.x,
+        }
+    }
+
+    /// Returns the generalized version of a `Size2D` dependent on
+    /// the layouting axes, that is:
+    /// - The x coordinate describes the primary axis instead of the horizontal one.
+    /// - The y coordinate describes the secondary axis instead of the vertical one.
+    pub fn generalized(&self, axes: LayoutAxes) -> Size2D {
+        match axes.primary.is_horizontal() {
+            true => *self,
+            false => Size2D { x: self.y, y: self.x },
+        }
+    }
+
+    /// Returns the specialized version of this generalized Size2D.
+    /// (Inverse to `generalized`).
+    pub fn specialized(&self, axes: LayoutAxes) -> Size2D {
+        // In fact, generalized is its own inverse. For reasons of clarity
+        // at the call site, we still have this second function.
+        self.generalized(axes)
     }
 
     /// Return a 2D-size padded by the paddings of the given box.
@@ -150,9 +212,24 @@ impl Size2D {
         self.x.max_eq(other.x);
         self.y.max_eq(other.y);
     }
+
+    /// Set this size to the minimum of itself and the other size
+    /// (for both dimensions).
+    pub fn min_eq(&mut self, other: Size2D) {
+        self.x.min_eq(other.x);
+        self.y.min_eq(other.y);
+    }
 }
 
 impl SizeBox {
+    /// The zeroed size box.
+    pub const ZERO: SizeBox = SizeBox {
+        left: Size::ZERO,
+        top: Size::ZERO,
+        right: Size::ZERO,
+        bottom: Size::ZERO,
+    };
+
     /// Create a new box from four sizes.
     pub fn new(left: Size, top: Size, right: Size, bottom: Size) -> SizeBox {
         SizeBox {
@@ -165,8 +242,7 @@ impl SizeBox {
 
     /// Create a box with all values set to zero.
     pub fn zero() -> SizeBox {
-        let zero = Size::zero();
-        SizeBox::new(zero, zero, zero, zero)
+        SizeBox::ZERO
     }
 
     /// Create a box with all four fields set to the same value `s`.
@@ -269,7 +345,7 @@ impl Neg for Size {
 impl Sum for Size {
     fn sum<I>(iter: I) -> Size
     where I: Iterator<Item = Size> {
-        iter.fold(Size::zero(), Add::add)
+        iter.fold(Size::ZERO, Add::add)
     }
 }
 
diff --git a/tests/layouts/test.typ b/tests/layouts/test.typ
index 063a7bfe..68f73a73 100644
--- a/tests/layouts/test.typ
+++ b/tests/layouts/test.typ
@@ -1,31 +1,21 @@
 [page.size: w=5cm, h=5cm]
 [page.margins: 0cm]
 
-// [box: w=4cm, h=3cm][1]
-// //
-// [direction: ttb, ltr]
-// [box: w=2cm, h=1][2]
-// //
-// [direction: btt, rtl]
-// [align: bottom, right]
-// [box: w=3cm, h=1][3]
-// //
-// [direction: ltr, ttb]
-// [align: center, center]
-// [box: w=2cm, h=2cm][4]
+// Test 1
+// [box][
+//     [align: center]
+//     [box: ps=3cm, ss=1cm]
+//     [direction: ttb, ltr]
+//     [box: ps=3cm, ss=1cm]
+//     [box: ps=1cm, ss=1cm]
+//     [box: ps=2cm, ss=1cm]
+//     [box: ps=1cm, ss=1cm]
+// ]
 
-[align: center]
-
-//[direction: primary=btt, secondary=rtl]
-//[align: primary=bottom, secondary=right]
-//[box][Hi]
-
-[box][
-//[align: primary=center, secondary=bottom]
-[direction: secondary=btt]
-Blabla
-[v: 0.5cm]
-[align: vertical=end] Origin 2]
-//[align: vertical=center] Center
-//[align: vertical=center] Center
-//[align: vertical=end]    End End End
+// Test 2
+[align: secondary=top] Top
+[align: secondary=center] Center
+[align: secondary=bottom] Bottom
+[direction: ttb, ltr]
+[align: primary=bottom]
+[box: w=1cm, h=1cm]
diff --git a/tests/render.py b/tests/render.py
index 2e105eb2..93d59ea8 100644
--- a/tests/render.py
+++ b/tests/render.py
@@ -105,10 +105,10 @@ class BoxRenderer:
 
         img = Image.new('RGBA', self.size, (255, 255, 255, 255))
         pixels = numpy.array(img)
-        for i in range(0, int(height)):
-            for j in range(0, int(width)):
-                if ((i // 2) % 2 == 0) == ((j // 2) % 2 == 0):
-                    pixels[4*i:4*(i+1), 4*j:4*(j+1)] = (225, 225, 225, 255)
+        # for i in range(0, int(height)):
+        #     for j in range(0, int(width)):
+        #         if ((i // 2) % 2 == 0) == ((j // 2) % 2 == 0):
+        #             pixels[4*i:4*(i+1), 4*j:4*(j+1)] = (225, 225, 225, 255)
 
         self.img = Image.fromarray(pixels, 'RGBA')
         self.draw = ImageDraw.Draw(self.img)