Introduce flex layouting 🎈

11 files changed, 559 insertions, 574 deletions

diff --git a/src/doc.rs b/src/doc.rs
index 304b4936..f08332f6 100644
--- a/src/doc.rs
+++ b/src/doc.rs
@@ -1,7 +1,7 @@
 //! Representation of typesetted documents.
 
 use crate::font::Font;
-use crate::layout::{Size, Position};
+use crate::size::{Size, Size2D};
 
 
 /// A complete typesetted document, which can be exported.
@@ -28,9 +28,9 @@ pub struct Page {
 #[derive(Debug, Clone)]
 pub enum TextAction {
     /// Move to an absolute position.
-    MoveAbsolute(Position),
+    MoveAbsolute(Size2D),
     /// Move from the _start_ of the current line by an (x, y) offset.
-    MoveNewline(Position),
+    MoveNewline(Size2D),
     /// Write text starting at the current position.
     WriteText(String),
     /// Set the font by index and font size.
diff --git a/src/export/pdf.rs b/src/export/pdf.rs
index c3f67afa..1c0d52b0 100644
--- a/src/export/pdf.rs
+++ b/src/export/pdf.rs
@@ -10,7 +10,7 @@ use pdf::font::{GlyphUnit, CMap, CMapEncoding, WidthRecord, FontStream};
 
 use crate::doc::{Document, Page as DocPage, TextAction};
 use crate::font::{Font, FontError};
-use crate::layout::Size;
+use crate::size::Size;
 
 
 /// Exports documents into _PDFs_.
diff --git a/src/font.rs b/src/font.rs
index 6b074e73..fada64ef 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -22,7 +22,7 @@ use opentype::{Error as OpentypeError, OpenTypeReader, Outlines, TableRecord, Ta
 use opentype::tables::{Header, Name, CharMap, MaximumProfile, HorizontalMetrics, Post, OS2};
 use opentype::global::{MacStyleFlags, NameEntry};
 
-use crate::layout::Size;
+use crate::size::Size;
 
 
 /// A loaded and parsed font program.
diff --git a/src/layout/boxed.rs b/src/layout/boxed.rs
index c240db0b..b75ea75a 100644
--- a/src/layout/boxed.rs
+++ b/src/layout/boxed.rs
@@ -1,10 +1,34 @@
-//! Layouting of layout boxes.
+//! Definitive layouting of boxes.
 
-use crate::doc::TextAction;
-use super::{Layouter, Layout, LayoutContext, LayoutResult, Position};
+use crate::doc::{Document, Page, TextAction};
+use crate::font::Font;
+use super::{Layouter, LayoutContext, Size2D};
 
 
-/// Layouts sublayouts within the constraints of a layouting context.
+/// A box layout has a fixed width and height and consists of actions.
+#[derive(Debug, Clone)]
+pub struct BoxLayout {
+    /// The size of the box.
+    dimensions: Size2D,
+    /// The actions composing this layout.
+    actions: Vec<TextAction>,
+}
+
+impl BoxLayout {
+    /// Convert this layout into a document given the list of fonts referenced by it.
+    pub fn into_doc(self, fonts: Vec<Font>) -> Document {
+        Document {
+            pages: vec![Page {
+                width: self.dimensions.x,
+                height: self.dimensions.y,
+                actions: self.actions,
+            }],
+            fonts,
+        }
+    }
+}
+
+/// Layouts boxes block-style.
 #[derive(Debug)]
 pub struct BoxLayouter<'a, 'p> {
     ctx: &'a LayoutContext<'a, 'p>,
@@ -21,17 +45,29 @@ impl<'a, 'p> BoxLayouter<'a, 'p> {
     }
 
     /// Add a sublayout.
-    pub fn add_layout_absolute(&mut self, position: Position, layout: Layout) {
+    pub fn add_box(&mut self, layout: BoxLayout) {
+        unimplemented!()
+    }
+
+    /// Add a sublayout at an absolute position.
+    pub fn add_box_absolute(&mut self, position: Size2D, layout: BoxLayout) {
         self.actions.push(TextAction::MoveAbsolute(position));
         self.actions.extend(layout.actions);
     }
 }
 
 impl Layouter for BoxLayouter<'_, '_> {
-    fn finish(self) -> LayoutResult<Layout> {
-        Ok(Layout {
-            extent: self.ctx.max_extent.clone(),
+    type Layout = BoxLayout;
+
+    /// Finish the layouting and create a box layout from this.
+    fn finish(self) -> BoxLayout {
+        BoxLayout {
+            dimensions: self.ctx.space.dimensions.clone(),
             actions: self.actions
-        })
+        }
+    }
+
+    fn is_empty(&self) -> bool {
+        self.actions.is_empty()
     }
 }
diff --git a/src/layout/flex.rs b/src/layout/flex.rs
new file mode 100644
index 00000000..faddc95a
--- /dev/null
+++ b/src/layout/flex.rs
@@ -0,0 +1,61 @@
+//! Flexible and lazy layouting of boxes.
+
+use super::{Layouter, LayoutContext, BoxLayout};
+
+
+/// A flex layout consists of a yet unarranged list of boxes.
+#[derive(Debug, Clone)]
+pub struct FlexLayout {
+    /// The sublayouts composing this layout.
+    layouts: Vec<BoxLayout>,
+}
+
+impl FlexLayout {
+    /// Compute the layout.
+    pub fn into_box(self) -> BoxLayout {
+        // TODO: Do the justification.
+        unimplemented!()
+    }
+}
+
+/// Layouts boxes next to each other (inline-style) lazily.
+#[derive(Debug)]
+pub struct FlexLayouter<'a, 'p> {
+    ctx: &'a LayoutContext<'a, 'p>,
+    layouts: Vec<BoxLayout>,
+}
+
+impl<'a, 'p> FlexLayouter<'a, 'p> {
+    /// Create a new flex layouter.
+    pub fn new(ctx: &'a LayoutContext<'a, 'p>) -> FlexLayouter<'a, 'p> {
+        FlexLayouter {
+            ctx,
+            layouts: vec![],
+        }
+    }
+
+    /// Add a sublayout.
+    pub fn add_box(&mut self, layout: BoxLayout) {
+        self.layouts.push(layout);
+    }
+
+    /// Add all sublayouts of another flex layout.
+    pub fn add_flexible(&mut self, layout: FlexLayout) {
+        self.layouts.extend(layout.layouts);
+    }
+}
+
+impl Layouter for FlexLayouter<'_, '_> {
+    type Layout = FlexLayout;
+
+    /// Finish the layouting and create a flexible layout from this.
+    fn finish(self) -> FlexLayout {
+        FlexLayout {
+            layouts: self.layouts
+        }
+    }
+
+    fn is_empty(&self) -> bool {
+        self.layouts.is_empty()
+    }
+}
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 1c1f743e..8b0c3004 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -1,74 +1,35 @@
 //! The layouting engine.
 
-use crate::doc::{Document, Page, TextAction};
-use crate::font::{Font, FontLoader, FontFamily, FontError};
+use crate::font::{FontLoader, FontError};
+use crate::size::{Size2D, SizeBox};
 use crate::syntax::{SyntaxTree, Node};
+use crate::style::TextStyle;
 
-mod size;
-mod text;
 mod boxed;
+mod flex;
 
-pub use size::{Size, Position, Extent};
-pub use text::TextLayouter;
-pub use boxed::BoxLayouter;
+pub use flex::{FlexLayout, FlexLayouter};
+pub use boxed::{BoxLayout, BoxLayouter};
 
 
-/// Layout a syntax tree in a given context.
-pub fn layout(tree: &SyntaxTree, ctx: &LayoutContext) -> LayoutResult<Layout> {
-    let mut layouter = TextLayouter::new(ctx);
-
-    let mut italic = false;
-    let mut bold = false;
-
-    for node in &tree.nodes {
-        match node {
-            Node::Text(text) => layouter.add_text(text)?,
-            Node::Space => layouter.add_space()?,
-            Node::Newline => layouter.add_paragraph()?,
-
-            Node::ToggleItalics => {
-                italic = !italic;
-                layouter.set_italic(italic);
-            },
-            Node::ToggleBold => {
-                bold = !bold;
-                layouter.set_bold(bold);
-            }
+/// Types that layout components and can be finished into some kind of layout.
+pub trait Layouter {
+    type Layout;
 
-            Node::Func(_) => unimplemented!(),
-        }
-    }
+    /// Finish the layouting and create the layout from this.
+    fn finish(self) -> Self::Layout;
 
-    layouter.finish()
+    /// Whether this layouter contains any items.
+    fn is_empty(&self) -> bool;
 }
 
 /// A collection of layouted content.
 #[derive(Debug, Clone)]
-pub struct Layout {
-    /// The extent of this layout into all directions.
-    extent: Extent,
-    /// Actions composing this layout.
-    actions: Vec<TextAction>,
-}
-
-impl Layout {
-    /// Convert this layout into a document given the list of fonts referenced by it.
-    pub fn into_document(self, fonts: Vec<Font>) -> Document {
-        Document {
-            pages: vec![Page {
-                width: self.extent.width,
-                height: self.extent.height,
-                actions: self.actions,
-            }],
-            fonts,
-        }
-    }
-}
-
-/// Types supporting some kind of layouting.
-pub trait Layouter {
-    /// Finishing the current layouting process and return a layout.
-    fn finish(self) -> LayoutResult<Layout>;
+pub enum Layout {
+    /// A box layout.
+    Boxed(BoxLayout),
+    /// A flexible layout.
+    Flex(FlexLayout),
 }
 
 /// The context for layouting.
@@ -76,70 +37,61 @@ pub trait Layouter {
 pub struct LayoutContext<'a, 'p> {
     /// Loads fonts matching queries.
     pub loader: &'a FontLoader<'p>,
-    /// The spacial constraints to layout in.
-    pub max_extent: Extent,
     /// Base style to set text with.
-    pub text_style: TextStyle,
+    pub style: TextStyle,
+    /// The space to layout in.
+    pub space: LayoutSpace,
 }
 
-/// Default styles for text.
+/// Spacial constraints for layouting.
 #[derive(Debug, Clone)]
-pub struct TextStyle {
-    /// A fallback list of font families to use.
-    pub font_families: Vec<FontFamily>,
-    /// The font size.
-    pub font_size: f32,
-    /// The line spacing (as a multiple of the font size).
-    pub line_spacing: f32,
-    /// The paragraphs spacing (as a multiple of the line spacing).
-    pub paragraph_spacing: f32,
+pub struct LayoutSpace {
+    /// The maximum size of the box to layout in.
+    pub dimensions: Size2D,
+    /// Padding that should be respected on each side.
+    pub padding: SizeBox,
 }
 
-impl Default for TextStyle {
-    fn default() -> TextStyle {
-        use FontFamily::*;
-        TextStyle {
-            // Default font family, font size and line spacing.
-            font_families: vec![SansSerif, Serif, Monospace],
-            font_size: 11.0,
-            line_spacing: 1.25,
-            paragraph_spacing: 1.5,
-        }
-    }
-}
+/// Layout a syntax tree in a given context.
+pub fn layout(tree: &SyntaxTree, ctx: &LayoutContext) -> LayoutResult<BoxLayout> {
+    // The top-level layouter and the sub-level layouter.
+    let mut box_layouter = BoxLayouter::new(ctx);
+    let mut flex_layouter = FlexLayouter::new(ctx);
 
-/// Default styles for pages.
-#[derive(Debug, Clone)]
-pub struct PageStyle {
-    /// The width of the page.
-    pub width: Size,
-    /// The height of the page.
-    pub height: Size,
-
-    /// The amount of white space on the left side.
-    pub margin_left: Size,
-    /// The amount of white space on the top side.
-    pub margin_top: Size,
-    /// The amount of white space on the right side.
-    pub margin_right: Size,
-    /// The amount of white space on the bottom side.
-    pub margin_bottom: Size,
-}
+    // The current text style.
+    let mut italic = false;
+    let mut bold = false;
 
-impl Default for PageStyle {
-    fn default() -> PageStyle {
-        PageStyle {
-            // A4 paper.
-            width: Size::from_mm(210.0),
-            height: Size::from_mm(297.0),
-
-            // All the same margins.
-            margin_left: Size::from_cm(3.0),
-            margin_top: Size::from_cm(3.0),
-            margin_right: Size::from_cm(3.0),
-            margin_bottom: Size::from_cm(3.0),
+    // Walk all nodes and layout them.
+    for node in &tree.nodes {
+        match node {
+            Node::Text(text) => {
+                unimplemented!()
+            },
+            Node::Space => {
+                unimplemented!()
+            },
+            Node::Newline => {
+                unimplemented!()
+            },
+
+            // Toggle the text styles.
+            Node::ToggleItalics => italic = !italic,
+            Node::ToggleBold => bold = !bold,
+
+            Node::Func(func) => {
+                unimplemented!()
+            }
         }
     }
+
+    // If there are remainings, add them to the layout.
+    if !flex_layouter.is_empty() {
+        let boxed = flex_layouter.finish().into_box();
+        box_layouter.add_box(boxed);
+    }
+
+    Ok(box_layouter.finish())
 }
 
 /// The error type for layouting.
diff --git a/src/layout/size.rs b/src/layout/size.rs
deleted file mode 100644
index 92a4c113..00000000
--- a/src/layout/size.rs
+++ /dev/null
@@ -1,173 +0,0 @@
-//! A general spacing type.
-
-use std::cmp::Ordering;
-use std::fmt::{self, Display, Debug, Formatter};
-use std::iter::Sum;
-use std::ops::*;
-
-
-/// A position in 2-dimensional space.
-#[derive(Debug, Copy, Clone, PartialEq, Default)]
-pub struct Position {
-    /// The horizontal coordinate.
-    pub x: Size,
-    /// The vertical coordinate.
-    pub y: Size,
-}
-
-impl Position {
-    /// Create a zeroed position.
-    #[inline]
-    pub fn zero() -> Position { Position { x: Size::zero(), y: Size::zero() } }
-}
-
-/// Size of a box in 2-dimensional space.
-#[derive(Debug, Copy, Clone, PartialEq, Default)]
-pub struct Extent {
-    /// The horizontal extent.
-    pub width: Size,
-    /// The vertical extent.
-    pub height: Size,
-}
-
-/// A general spacing type.
-#[derive(Copy, Clone, PartialEq, Default)]
-pub struct Size {
-    /// The size in typographic points (1/72 inches).
-    points: f32,
-}
-
-impl Size {
-    /// Create a zeroed size.
-    #[inline]
-    pub fn zero() -> Size { Size { points: 0.0 } }
-
-    /// Create a size from an amount of points.
-    #[inline]
-    pub fn from_points(points: f32) -> Size { Size { points } }
-
-    /// Create a size from an amount of inches.
-    #[inline]
-    pub fn from_inches(inches: f32) -> Size { Size { points: 72.0 * inches } }
-
-    /// Create a size from an amount of millimeters.
-    #[inline]
-    pub fn from_mm(mm: f32) -> Size { Size { points: 2.83465 * mm  } }
-
-    /// Create a size from an amount of centimeters.
-    #[inline]
-    pub fn from_cm(cm: f32) -> Size { Size { points: 28.3465 * cm } }
-
-    /// Convert this size into points.
-    #[inline]
-    pub fn to_points(&self) -> f32 { self.points }
-
-    /// Convert this size into inches.
-    #[inline]
-    pub fn to_inches(&self) -> f32 { self.points * 0.0138889 }
-
-    /// Convert this size into millimeters.
-    #[inline]
-    pub fn to_mm(&self) -> f32 { self.points * 0.352778 }
-
-    /// Convert this size into centimeters.
-    #[inline]
-    pub fn to_cm(&self) -> f32 { self.points * 0.0352778 }
-}
-
-impl Display for Size {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{}pt", self.points)
-    }
-}
-
-impl Debug for Size {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        Display::fmt(self, f)
-    }
-}
-
-impl PartialOrd for Size {
-    #[inline]
-    fn partial_cmp(&self, other: &Size) -> Option<Ordering> {
-        self.points.partial_cmp(&other.points)
-    }
-}
-
-impl Neg for Size {
-    type Output = Size;
-
-    #[inline]
-    fn neg(self) -> Size {
-        Size { points: -self.points }
-    }
-}
-
-impl Sum for Size {
-    #[inline]
-    fn sum<I>(iter: I) -> Size where I: Iterator<Item=Size> {
-        iter.fold(Size::zero(), Add::add)
-    }
-}
-
-macro_rules! impl_reflexive {
-    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident) => {
-        impl $trait for Size {
-            type Output = Size;
-
-            #[inline]
-            fn $func(self, other: Size) -> Size {
-                Size { points: $trait::$func(self.points, other.points) }
-            }
-        }
-
-        impl $assign_trait for Size {
-            #[inline]
-            fn $assign_func(&mut self, other: Size) {
-                $assign_trait::$assign_func(&mut self.points, other.points);
-            }
-        }
-    };
-}
-
-macro_rules! impl_num_back {
-    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident, $ty:ty) => {
-        impl $trait<$ty> for Size {
-            type Output = Size;
-
-            #[inline]
-            fn $func(self, other: $ty) -> Size {
-                Size { points: $trait::$func(self.points, other as f32) }
-            }
-        }
-
-        impl $assign_trait<$ty> for Size {
-            #[inline]
-            fn $assign_func(&mut self, other: $ty) {
-                $assign_trait::$assign_func(&mut self.points, other as f32);
-            }
-        }
-    };
-}
-
-macro_rules! impl_num_both {
-    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident, $ty:ty) => {
-        impl_num_back!($trait, $func, $assign_trait, $assign_func, $ty);
-
-        impl $trait<Size> for $ty {
-            type Output = Size;
-
-            #[inline]
-            fn $func(self, other: Size) -> Size {
-                Size { points: $trait::$func(self as f32, other.points) }
-            }
-        }
-    };
-}
-
-impl_reflexive!(Add, add, AddAssign, add_assign);
-impl_reflexive!(Sub, sub, SubAssign, sub_assign);
-impl_num_both!(Mul, mul, MulAssign, mul_assign, f32);
-impl_num_both!(Mul, mul, MulAssign, mul_assign, i32);
-impl_num_back!(Div, div, DivAssign, div_assign, f32);
-impl_num_back!(Div, div, DivAssign, div_assign, i32);
diff --git a/src/layout/text.rs b/src/layout/text.rs
deleted file mode 100644
index d1e2afd7..00000000
--- a/src/layout/text.rs
+++ /dev/null
@@ -1,243 +0,0 @@
-//! Layouting of text.
-
-use std::cell::Ref;
-use std::mem;
-
-use smallvec::SmallVec;
-
-use crate::doc::TextAction;
-use crate::font::{Font, FontQuery};
-use super::{Layouter, Layout, LayoutError, LayoutContext, LayoutResult, Size, Position};
-
-
-/// Layouts text within the constraints of a layouting context.
-#[derive(Debug)]
-pub struct TextLayouter<'a, 'p> {
-    ctx: &'a LayoutContext<'a, 'p>,
-    units: Vec<Unit>,
-    italic: bool,
-    bold: bool,
-}
-
-/// A units that is arranged by the text layouter.
-#[derive(Debug, Clone)]
-enum Unit {
-    /// A paragraph.
-    Paragraph,
-    /// A space with its font index and width.
-    Space(usize, Size),
-    /// One logical tex  unit.
-    Text(TextUnit),
-}
-
-/// A logical unit of text (a word, syllable or a similar construct).
-#[derive(Debug, Clone)]
-struct TextUnit {
-    /// Contains pairs of (characters, font_index, char_width) for each character of the text.
-    chars_with_widths: SmallVec<[(char, usize, Size); 12]>,
-    /// The total width of the unit.
-    width: Size,
-}
-
-impl<'a, 'p> TextLayouter<'a, 'p> {
-    /// Create a new text layouter.
-    pub fn new(ctx: &'a LayoutContext<'a, 'p>) -> TextLayouter<'a, 'p> {
-        TextLayouter {
-            ctx,
-            italic: false,
-            bold: false,
-            units: vec![],
-        }
-    }
-
-    /// Add more text to the layout.
-    pub fn add_text(&mut self, text: &str) -> LayoutResult<()> {
-        let mut chars_with_widths = SmallVec::<[(char, usize, Size); 12]>::new();
-
-        // Find out which font to use for each character in the text and meanwhile calculate the
-        // width of the text.
-        let mut text_width = Size::zero();
-        for c in text.chars() {
-            // Find out the width and add it to the total width.
-            let (index, font) = self.get_font_for(c)?;
-            let char_width = self.width_of(c, &font);
-            text_width += char_width;
-
-            chars_with_widths.push((c, index, char_width));
-        }
-
-        self.units.push(Unit::Text(TextUnit {
-            chars_with_widths,
-            width: text_width,
-        }));
-
-        Ok(())
-    }
-
-    /// Add a single space character.
-    pub fn add_space(&mut self) -> LayoutResult<()> {
-        let (index, font) = self.get_font_for(' ')?;
-        let width = self.width_of(' ', &font);
-        drop(font);
-        Ok(self.units.push(Unit::Space(index, width)))
-    }
-
-    /// Start a new paragraph.
-    pub fn add_paragraph(&mut self) -> LayoutResult<()> {
-        Ok(self.units.push(Unit::Paragraph))
-    }
-
-    /// Enable or disable italics.
-    pub fn set_italic(&mut self, italic: bool) {
-        self.italic = italic;
-    }
-
-    /// Enable or disable boldface.
-    pub fn set_bold(&mut self, bold: bool) {
-        self.bold = bold;
-    }
-
-    /// Load a font that has the character we need.
-    fn get_font_for(&self, character: char) -> LayoutResult<(usize, Ref<Font>)> {
-        self.ctx.loader.get(FontQuery {
-            families: self.ctx.text_style.font_families.clone(),
-            italic: self.italic,
-            bold: self.bold,
-            character,
-        }).ok_or_else(|| LayoutError::NoSuitableFont(character))
-    }
-
-    /// The width of a char in a specific font.
-    fn width_of(&self, character: char, font: &Font) -> Size {
-        font.widths[font.map(character) as usize] * self.ctx.text_style.font_size
-    }
-}
-
-impl Layouter for TextLayouter<'_, '_> {
-    fn finish(self) -> LayoutResult<Layout> {
-        TextFinisher {
-            actions: vec![],
-            buffered_text: String::new(),
-            current_width: Size::zero(),
-            active_font: std::usize::MAX,
-            max_width: self.ctx.max_extent.width,
-            layouter: self,
-        }.finish()
-    }
-}
-
-/// Finishes a text layout by converting the text units into a stream of text actions.
-#[derive(Debug)]
-struct TextFinisher<'a, 'p> {
-    layouter: TextLayouter<'a, 'p>,
-    actions: Vec<TextAction>,
-    buffered_text: String,
-    current_width: Size,
-    active_font: usize,
-    max_width: Size,
-}
-
-impl<'a, 'p> TextFinisher<'a, 'p> {
-    /// Finish the layout.
-    fn finish(mut self) -> LayoutResult<Layout> {
-        // Move the units out of the layouter leaving an empty vector in place. This is needed to
-        // move the units out into the for loop while keeping the borrow checker happy.
-        let mut units = Vec::new();
-        mem::swap(&mut self.layouter.units, &mut units);
-
-        // Move from the origin one line below because the y-component of the origin is the
-        // baseline.
-        self.move_newline(1.0);
-
-        for unit in units {
-            match unit {
-                Unit::Paragraph => self.write_paragraph(),
-                Unit::Space(index, width) => self.write_space(index, width),
-                Unit::Text(text) => self.write_text_unit(text),
-            }
-        }
-
-        self.write_buffered_text();
-
-        Ok(Layout {
-            extent: self.layouter.ctx.max_extent.clone(),
-            actions: self.actions,
-        })
-    }
-
-    /// Add a paragraph to the output.
-    fn write_paragraph(&mut self) {
-        self.write_buffered_text();
-        self.move_newline(self.layouter.ctx.text_style.paragraph_spacing);
-    }
-
-    /// Add a single space to the output if it is not eaten by a line break.
-    fn write_space(&mut self, font: usize, width: Size) {
-        if self.would_overflow(width) {
-            self.write_buffered_text();
-            self.move_newline(1.0);
-        } else if self.current_width > Size::zero() {
-            if font != self.active_font {
-                self.write_buffered_text();
-                self.set_font(font);
-            }
-
-            self.buffered_text.push(' ');
-            self.current_width += width;
-        }
-    }
-
-    /// Add a single unit of text without breaking it apart.
-    fn write_text_unit(&mut self, text: TextUnit) {
-        if self.would_overflow(text.width) {
-            self.write_buffered_text();
-            self.move_newline(1.0);
-        }
-
-        // Finally write the word.
-        for (c, font, width) in text.chars_with_widths {
-            if font != self.active_font {
-                // If we will change the font, first write the remaining things.
-                self.write_buffered_text();
-                self.set_font(font);
-            }
-
-            self.buffered_text.push(c);
-            self.current_width += width;
-        }
-    }
-
-    /// Move to the next line. A factor of 1.0 uses the default line spacing.
-    fn move_newline(&mut self, factor: f32) {
-        let vertical = Size::from_points(self.layouter.ctx.text_style.font_size)
-            * self.layouter.ctx.text_style.line_spacing
-            * factor;
-
-        self.actions.push(TextAction::MoveNewline(Position {
-            x: Size::zero(),
-            y: vertical
-        }));
-
-        self.current_width = Size::zero();
-    }
-
-    /// Output a text action containing the buffered text and reset the buffer.
-    fn write_buffered_text(&mut self) {
-        if !self.buffered_text.is_empty() {
-            let mut buffered = String::new();
-            mem::swap(&mut self.buffered_text, &mut buffered);
-            self.actions.push(TextAction::WriteText(buffered));
-        }
-    }
-
-    /// Output an action setting a new font and update the active font.
-    fn set_font(&mut self, index: usize) {
-        self.active_font = index;
-        self.actions.push(TextAction::SetFont(index, self.layouter.ctx.text_style.font_size));
-    }
-
-    /// Check whether additional text with the given width would overflow the current line.
-    fn would_overflow(&self, width: Size) -> bool {
-        self.current_width + width > self.max_width
-    }
-}
diff --git a/src/lib.rs b/src/lib.rs
index 398df467..08156e14 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -48,9 +48,9 @@ use std::fmt::{self, Debug, Formatter};
 use crate::doc::Document;
 use crate::font::{Font, FontLoader, FontProvider};
 use crate::func::Scope;
-use crate::layout::{layout, Layout, Layouter, LayoutContext, BoxLayouter, Extent, Position};
-use crate::layout::{PageStyle, TextStyle, LayoutResult, LayoutError};
 use crate::parsing::{parse, ParseContext, ParseResult, ParseError};
+use crate::layout::{layout, LayoutContext, LayoutSpace, LayoutError, LayoutResult, BoxLayout};
+use crate::style::{PageStyle, TextStyle};
 use crate::syntax::SyntaxTree;
 
 #[macro_use]
@@ -62,6 +62,8 @@ pub mod font;
 pub mod func;
 pub mod layout;
 pub mod parsing;
+pub mod size;
+pub mod style;
 pub mod syntax;
 
 
@@ -69,12 +71,12 @@ pub mod syntax;
 ///
 /// Can be configured through various methods.
 pub struct Typesetter<'p> {
-    /// The default page style.
-    page_style: PageStyle,
-    /// The default text style.
-    text_style: TextStyle,
     /// Font providers.
     font_providers: Vec<Box<dyn FontProvider + 'p>>,
+    /// The default text style.
+    text_style: TextStyle,
+    /// The default page style.
+    page_style: PageStyle,
 }
 
 impl<'p> Typesetter<'p> {
@@ -82,8 +84,8 @@ impl<'p> Typesetter<'p> {
     #[inline]
     pub fn new() -> Typesetter<'p> {
         Typesetter {
-            page_style: PageStyle::default(),
             text_style: TextStyle::default(),
+            page_style: PageStyle::default(),
             font_providers: vec![],
         }
     }
@@ -115,36 +117,19 @@ impl<'p> Typesetter<'p> {
     }
 
     /// Layout a syntax tree and return the layout and the referenced font list.
-    pub fn layout(&self, tree: &SyntaxTree) -> LayoutResult<(Layout, Vec<Font>)> {
+    pub fn layout(&self, tree: &SyntaxTree) -> LayoutResult<(BoxLayout, Vec<Font>)> {
         let loader = FontLoader::new(&self.font_providers);
-
-        // Prepare the layouting context.
-        let page = &self.page_style;
-        let mut ctx = LayoutContext {
+        let ctx = LayoutContext {
             loader: &loader,
-            text_style: self.text_style.clone(),
-            max_extent: Extent {
-                width: page.width - page.margin_left - page.margin_right,
-                height: page.height - page.margin_top - page.margin_bottom,
+            style: self.text_style.clone(),
+            space: LayoutSpace {
+                dimensions: self.page_style.dimensions,
+                padding: self.page_style.margins,
             },
         };
 
-        // Layout the content of the page (without margins).
-        let content = layout(&tree, &ctx)?;
-
-        // Adjust the context for adding the margins.
-        ctx.max_extent = Extent {
-            width: page.width,
-            height: page.height,
-        };
-
-        // Add the margins.
-        let mut box_layouter = BoxLayouter::new(&ctx);
-        let start = Position { x: page.margin_left, y: page.margin_top };
-        box_layouter.add_layout_absolute(start, content);
-        let layout = box_layouter.finish()?;
-
-        Ok((layout, loader.into_fonts()))
+        let pages = layout(&tree, &ctx)?;
+        Ok((pages, loader.into_fonts()))
     }
 
     /// Typeset a portable document from source code.
@@ -152,7 +137,7 @@ impl<'p> Typesetter<'p> {
     pub fn typeset(&self, src: &str) -> Result<Document, TypesetError> {
         let tree = self.parse(src)?;
         let (layout, fonts) = self.layout(&tree)?;
-        let document = layout.into_document(fonts);
+        let document = layout.into_doc(fonts);
         Ok(document)
     }
 }
diff --git a/src/size.rs b/src/size.rs
new file mode 100644
index 00000000..d1096164
--- /dev/null
+++ b/src/size.rs
@@ -0,0 +1,307 @@
+//! General spacing types.
+
+use std::cmp::Ordering;
+use std::fmt::{self, Display, Debug, Formatter};
+use std::iter::Sum;
+use std::ops::*;
+
+
+/// A general spacing type.
+#[derive(Copy, Clone, PartialEq, Default)]
+pub struct Size {
+    /// The size in typographic points (1/72 inches).
+    points: f32,
+}
+
+/// A position or extent in 2-dimensional space.
+#[derive(Copy, Clone, PartialEq, PartialOrd, Default)]
+pub struct Size2D {
+    /// The horizontal coordinate.
+    pub x: Size,
+    /// The vertical coordinate.
+    pub y: Size,
+}
+
+/// A size in four directions.
+#[derive(Copy, Clone, PartialEq, PartialOrd, Default)]
+pub struct SizeBox {
+    /// The left extent.
+    pub left: Size,
+    /// The top extent.
+    pub top: Size,
+    /// The right extent.
+    pub right: Size,
+    /// The bottom extent.
+    pub bottom: Size,
+}
+
+impl Size {
+    /// Create a zeroed size.
+    #[inline]
+    pub fn zero() -> Size { Size { points: 0.0 } }
+
+    /// Create a size from an amount of points.
+    #[inline]
+    pub fn from_points(points: f32) -> Size { Size { points } }
+
+    /// Create a size from an amount of inches.
+    #[inline]
+    pub fn from_inches(inches: f32) -> Size { Size { points: 72.0 * inches } }
+
+    /// Create a size from an amount of millimeters.
+    #[inline]
+    pub fn from_mm(mm: f32) -> Size { Size { points: 2.83465 * mm  } }
+
+    /// Create a size from an amount of centimeters.
+    #[inline]
+    pub fn from_cm(cm: f32) -> Size { Size { points: 28.3465 * cm } }
+
+    /// Convert this size into points.
+    #[inline]
+    pub fn to_points(&self) -> f32 { self.points }
+
+    /// Convert this size into inches.
+    #[inline]
+    pub fn to_inches(&self) -> f32 { self.points * 0.0138889 }
+
+    /// Convert this size into millimeters.
+    #[inline]
+    pub fn to_mm(&self) -> f32 { self.points * 0.352778 }
+
+    /// Convert this size into centimeters.
+    #[inline]
+    pub fn to_cm(&self) -> f32 { self.points * 0.0352778 }
+}
+
+impl Size2D {
+    /// Create a new 2D vector from two sizes.
+    #[inline]
+    pub fn new(x: Size, y: Size) -> Size2D { Size2D { x, y } }
+
+    /// Create a zeroed vector.
+    #[inline]
+    pub fn zero() -> Size2D { Size2D { x: Size::zero(), y: Size::zero() } }
+}
+
+impl SizeBox {
+    /// Create a new box from four sizes.
+    #[inline]
+    pub fn new(left: Size, top: Size, right: Size, bottom: Size) -> SizeBox {
+        SizeBox { left, top, right, bottom }
+    }
+
+    /// Create a zeroed vector.
+    #[inline]
+    pub fn zero() -> SizeBox {
+        SizeBox {
+            left: Size::zero(),
+            top: Size::zero(),
+            right: Size::zero(),
+            bottom: Size::zero(),
+        }
+    }
+}
+
+impl Display for Size {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}pt", self.points)
+    }
+}
+
+impl Debug for Size {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        Display::fmt(self, f)
+    }
+}
+
+impl PartialOrd for Size {
+    #[inline]
+    fn partial_cmp(&self, other: &Size) -> Option<Ordering> {
+        self.points.partial_cmp(&other.points)
+    }
+}
+
+impl Neg for Size {
+    type Output = Size;
+
+    #[inline]
+    fn neg(self) -> Size {
+        Size { points: -self.points }
+    }
+}
+
+impl Sum for Size {
+    #[inline]
+    fn sum<I>(iter: I) -> Size where I: Iterator<Item=Size> {
+        iter.fold(Size::zero(), Add::add)
+    }
+}
+
+macro_rules! impl_reflexive {
+    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident) => {
+        impl $trait for Size {
+            type Output = Size;
+
+            #[inline]
+            fn $func(self, other: Size) -> Size {
+                Size { points: $trait::$func(self.points, other.points) }
+            }
+        }
+
+        impl $assign_trait for Size {
+            #[inline]
+            fn $assign_func(&mut self, other: Size) {
+                $assign_trait::$assign_func(&mut self.points, other.points);
+            }
+        }
+    };
+}
+
+macro_rules! impl_num_back {
+    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident, $ty:ty) => {
+        impl $trait<$ty> for Size {
+            type Output = Size;
+
+            #[inline]
+            fn $func(self, other: $ty) -> Size {
+                Size { points: $trait::$func(self.points, other as f32) }
+            }
+        }
+
+        impl $assign_trait<$ty> for Size {
+            #[inline]
+            fn $assign_func(&mut self, other: $ty) {
+                $assign_trait::$assign_func(&mut self.points, other as f32);
+            }
+        }
+    };
+}
+
+macro_rules! impl_num_both {
+    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident, $ty:ty) => {
+        impl_num_back!($trait, $func, $assign_trait, $assign_func, $ty);
+
+        impl $trait<Size> for $ty {
+            type Output = Size;
+
+            #[inline]
+            fn $func(self, other: Size) -> Size {
+                Size { points: $trait::$func(self as f32, other.points) }
+            }
+        }
+    };
+}
+
+impl_reflexive!(Add, add, AddAssign, add_assign);
+impl_reflexive!(Sub, sub, SubAssign, sub_assign);
+impl_num_both!(Mul, mul, MulAssign, mul_assign, f32);
+impl_num_both!(Mul, mul, MulAssign, mul_assign, i32);
+impl_num_back!(Div, div, DivAssign, div_assign, f32);
+impl_num_back!(Div, div, DivAssign, div_assign, i32);
+
+impl Display for Size2D {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "[{}, {}]", self.x, self.y)
+    }
+}
+
+impl Debug for Size2D {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        Display::fmt(self, f)
+    }
+}
+
+impl Neg for Size2D {
+    type Output = Size2D;
+
+    #[inline]
+    fn neg(self) -> Size2D {
+        Size2D { x: -self.x, y: -self.y }
+    }
+}
+
+macro_rules! impl_reflexive2d {
+    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident) => {
+        impl $trait for Size2D {
+            type Output = Size2D;
+
+            #[inline]
+            fn $func(self, other: Size2D) -> Size2D {
+                Size2D {
+                    x: $trait::$func(self.x, other.x),
+                    y: $trait::$func(self.y, other.y),
+                }
+            }
+        }
+
+        impl $assign_trait for Size2D {
+            #[inline]
+            fn $assign_func(&mut self, other: Size2D) {
+                $assign_trait::$assign_func(&mut self.x, other.x);
+                $assign_trait::$assign_func(&mut self.y, other.y);
+            }
+        }
+    };
+}
+
+macro_rules! impl_num_back2d {
+    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident, $ty:ty) => {
+        impl $trait<$ty> for Size2D {
+            type Output = Size2D;
+
+            #[inline]
+            fn $func(self, other: $ty) -> Size2D {
+                Size2D {
+                    x: $trait::$func(self.x, other as f32),
+                    y: $trait::$func(self.y, other as f32),
+                }
+            }
+        }
+
+        impl $assign_trait<$ty> for Size2D {
+            #[inline]
+            fn $assign_func(&mut self, other: $ty) {
+                $assign_trait::$assign_func(&mut self.x, other as f32);
+                $assign_trait::$assign_func(&mut self.y, other as f32);
+            }
+        }
+    };
+}
+
+macro_rules! impl_num_both2d {
+    ($trait:ident, $func:ident, $assign_trait:ident, $assign_func:ident, $ty:ty) => {
+        impl_num_back2d!($trait, $func, $assign_trait, $assign_func, $ty);
+
+        impl $trait<Size2D> for $ty {
+            type Output = Size2D;
+
+            #[inline]
+            fn $func(self, other: Size2D) -> Size2D {
+                Size2D {
+                    x: $trait::$func(self as f32, other.x),
+                    y: $trait::$func(self as f32, other.y),
+                }
+            }
+        }
+    };
+}
+
+impl_reflexive2d!(Add, add, AddAssign, add_assign);
+impl_reflexive2d!(Sub, sub, SubAssign, sub_assign);
+impl_num_both2d!(Mul, mul, MulAssign, mul_assign, f32);
+impl_num_both2d!(Mul, mul, MulAssign, mul_assign, i32);
+impl_num_back2d!(Div, div, DivAssign, div_assign, f32);
+impl_num_back2d!(Div, div, DivAssign, div_assign, i32);
+
+impl Display for SizeBox {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "[left: {}, top: {}, right: {}, bottom: {}]",
+            self.left, self.top, self.right, self.bottom)
+    }
+}
+
+impl Debug for SizeBox {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        Display::fmt(self, f)
+    }
+}
diff --git a/src/style.rs b/src/style.rs
new file mode 100644
index 00000000..c4e92ec9
--- /dev/null
+++ b/src/style.rs
@@ -0,0 +1,60 @@
+//! Styles for layouting.
+
+use crate::font::FontFamily;
+use crate::size::{Size, Size2D, SizeBox};
+
+
+/// Default styles for text.
+#[derive(Debug, Clone)]
+pub struct TextStyle {
+    /// A fallback list of font families to use.
+    pub font_families: Vec<FontFamily>,
+    /// The font size.
+    pub font_size: f32,
+    /// The line spacing (as a multiple of the font size).
+    pub line_spacing: f32,
+    /// The paragraphs spacing (as a multiple of the line spacing).
+    pub paragraph_spacing: f32,
+}
+
+impl Default for TextStyle {
+    fn default() -> TextStyle {
+        use FontFamily::*;
+        TextStyle {
+            // Default font family, font size and line spacing.
+            font_families: vec![SansSerif, Serif, Monospace],
+            font_size: 11.0,
+            line_spacing: 1.25,
+            paragraph_spacing: 1.5,
+        }
+    }
+}
+
+/// Default styles for pages.
+#[derive(Debug, Clone)]
+pub struct PageStyle {
+    /// Width and height of the page.
+    pub dimensions: Size2D,
+    /// The amount of white space on each side.
+    pub margins: SizeBox,
+}
+
+impl Default for PageStyle {
+    fn default() -> PageStyle {
+        PageStyle {
+            // A4 paper.
+            dimensions: Size2D {
+                x: Size::from_mm(210.0),
+                y: Size::from_mm(297.0),
+            },
+
+            // All the same margins.
+            margins: SizeBox {
+                left: Size::from_cm(3.0),
+                top: Size::from_cm(3.0),
+                right: Size::from_cm(3.0),
+                bottom: Size::from_cm(3.0),
+            },
+        }
+    }
+}