Implement function layouting ✒

8 files changed, 166 insertions, 61 deletions

diff --git a/src/bin/main.rs b/src/bin/main.rs
index 6ca1ba56..b2f3d405 100644
--- a/src/bin/main.rs
+++ b/src/bin/main.rs
@@ -48,16 +48,22 @@ fn run() -> Result<(), Box<Error>> {
     let mut src = String::new();
     file.read_to_string(&mut src).map_err(|_| "failed to read from source file")?;
 
-    // Create a typesetter with a font provider that provides three fonts
-    // (two sans-serif fonts and a fallback for the emoji).
+    // Create a typesetter with a font provider that provides the default fonts.
     let mut typesetter = Typesetter::new();
     typesetter.add_font_provider(FileSystemFontProvider::new("fonts", vec![
-        ("NotoSans-Regular.ttf",     font_info!(["NotoSans", "Noto", SansSerif])),
-        ("NotoSans-Italic.ttf",      font_info!(["NotoSans", "Noto", SansSerif], italic)),
-        ("NotoSans-Bold.ttf",        font_info!(["NotoSans", "Noto", SansSerif], bold)),
-        ("NotoSans-BoldItalic.ttf",  font_info!(["NotoSans", "Noto", SansSerif], italic, bold)),
-        ("NotoSansMath-Regular.ttf", font_info!(["NotoSansMath", "Noto", SansSerif])),
-        ("NotoEmoji-Regular.ttf",    font_info!(["NotoEmoji", "Noto", SansSerif, Serif, Monospace])),
+        ("CMU-SansSerif-Regular.ttf", font_info!(["Computer Modern", SansSerif])),
+        ("CMU-SansSerif-Italic.ttf", font_info!(["Computer Modern", SansSerif], italic)),
+        ("CMU-SansSerif-Bold.ttf", font_info!(["Computer Modern", SansSerif], bold)),
+        ("CMU-SansSerif-Bold-Italic.ttf", font_info!(["Computer Modern", SansSerif], bold, italic)),
+        ("CMU-Serif-Regular.ttf", font_info!(["Computer Modern", Serif])),
+        ("CMU-Serif-Italic.ttf", font_info!(["Computer Modern", Serif], italic)),
+        ("CMU-Serif-Bold.ttf", font_info!(["Computer Modern", Serif], bold)),
+        ("CMU-Serif-Bold-Italic.ttf", font_info!(["Computer Modern", Serif], bold, italic)),
+        ("CMU-Typewriter-Regular.ttf", font_info!(["Computer Modern", Monospace])),
+        ("CMU-Typewriter-Italic.ttf", font_info!(["Computer Modern", Monospace], italic)),
+        ("CMU-Typewriter-Bold.ttf", font_info!(["Computer Modern", Monospace], bold)),
+        ("CMU-Typewriter-Bold-Italic.ttf", font_info!(["Computer Modern", Monospace], bold, italic)),
+        ("NotoEmoji-Regular.ttf", font_info!(["NotoEmoji", "Noto", SansSerif, Serif, Monospace])),
     ]));
 
     // Typeset the source code.
diff --git a/src/func.rs b/src/func.rs
index 402bf6fa..0d2a6274 100644
--- a/src/func.rs
+++ b/src/func.rs
@@ -4,9 +4,10 @@ use std::any::Any;
 use std::collections::HashMap;
 use std::fmt::{self, Debug, Formatter};
 
-use crate::layout::{Layout, LayoutContext, LayoutResult};
-use crate::parsing::{ParseContext, ParseResult};
-use crate::syntax::FuncHeader;
+use crate::layout::{layout, Layout, LayoutContext, LayoutResult};
+use crate::layout::flex::FlexLayout;
+use crate::parsing::{parse, ParseContext, ParseError, ParseResult};
+use crate::syntax::{SyntaxTree, FuncHeader};
 
 
 /// Typesetting function types.
@@ -25,8 +26,7 @@ pub trait Function: FunctionBounds {
     ///
     /// Returns optionally the resulting layout and a new context if changes to the context should
     /// be made.
-    fn layout(&self, ctx: &LayoutContext)
-        -> LayoutResult<(Option<Layout>, Option<LayoutContext>)>;
+    fn layout(&self, ctx: &LayoutContext) -> LayoutResult<Option<Layout>>;
 }
 
 impl PartialEq for dyn Function {
@@ -76,9 +76,14 @@ impl Scope {
         Scope { parsers: HashMap::new() }
     }
 
-    /// Create a new scope with the standard functions contained.
+    /// Create a new scope with the standard functions contained:
+    /// - `italic`
+    /// - `bold`
     pub fn with_std() -> Scope {
-        Scope::new()
+        let mut std = Scope::new();
+        std.add::<BoldFunc>("bold");
+        std.add::<ItalicFunc>("italic");
+        std
     }
 
     /// Add a function type to the scope giving it a name.
@@ -103,3 +108,52 @@ impl Debug for Scope {
         write!(f, "{:?}", self.parsers.keys())
     }
 }
+
+/// Creates style functions like bold and italic.
+macro_rules! style_func {
+    ($(#[$outer:meta])* pub struct $struct:ident { $name:expr },
+     $new_ctx:ident => $ctx_change:block) => {
+        $(#[$outer])*
+        #[derive(Debug, PartialEq)]
+        pub struct $struct { body: SyntaxTree }
+        impl Function for $struct {
+            fn parse(header: &FuncHeader, body: Option<&str>, ctx: &ParseContext)
+                -> ParseResult<Self> where Self: Sized {
+                // Accept only invocations without arguments and with body.
+                if header.args.is_empty() && header.kwargs.is_empty() {
+                    if let Some(body) = body {
+                        Ok($struct { body: parse(body, ctx)? })
+                    } else {
+                        Err(ParseError::new(format!("expected body for function `{}`", $name)))
+                    }
+                } else {
+                    Err(ParseError::new(format!("unexpected arguments to function `{}`", $name)))
+                }
+            }
+
+            fn layout(&self, ctx: &LayoutContext) -> LayoutResult<Option<Layout>> {
+                // Change the context.
+                let mut $new_ctx = ctx.clone();
+                $ctx_change
+
+                // Create a box and put it into a flex layout.
+                let boxed = layout(&self.body, &$new_ctx)?;
+                let flex = FlexLayout::from_box(boxed);
+
+                Ok(Some(Layout::Flex(flex)))
+            }
+        }
+    };
+}
+
+style_func! {
+    /// Typesets text in bold.
+    pub struct BoldFunc { "bold" },
+    ctx => { ctx.style.bold = !ctx.style.bold }
+}
+
+style_func! {
+    /// Typesets text in italics.
+    pub struct ItalicFunc { "italic" },
+    ctx => { ctx.style.italic = !ctx.style.italic }
+}
diff --git a/src/layout/boxed.rs b/src/layout/boxed.rs
index 89c641bc..e712f650 100644
--- a/src/layout/boxed.rs
+++ b/src/layout/boxed.rs
@@ -86,6 +86,15 @@ impl BoxLayouter {
         Ok(())
     }
 
+    /// Add a sublayout at an absolute position.
+    pub fn add_box_absolute(&mut self, position: Size2D, layout: BoxLayout) {
+        // Move all actions into this layout and translate absolute positions.
+        self.actions.reset_origin();
+        self.actions.add(TextAction::MoveAbsolute(position));
+        self.actions.set_origin(position);
+        self.actions.extend(layout.actions);
+    }
+
     /// Add some space in between two boxes.
     pub fn add_space(&mut self, space: Size) -> LayoutResult<()> {
         // Check whether this space fits.
@@ -100,20 +109,6 @@ impl BoxLayouter {
         Ok(())
     }
 
-    /// Add a sublayout at an absolute position.
-    pub fn add_box_absolute(&mut self, position: Size2D, layout: BoxLayout) {
-        // Move all actions into this layout and translate absolute positions.
-        self.actions.reset_origin();
-        self.actions.add(TextAction::MoveAbsolute(position));
-        self.actions.set_origin(position);
-        self.actions.extend(layout.actions);
-    }
-
-    /// Whether this layouter contains any items.
-    pub fn is_empty(&self) -> bool {
-        self.actions.is_empty()
-    }
-
     /// The remaining space for new boxes.
     pub fn remaining(&self) -> Size2D {
         Size2D {
@@ -122,6 +117,11 @@ impl BoxLayouter {
         }
     }
 
+    /// Whether this layouter contains any items.
+    pub fn is_empty(&self) -> bool {
+        self.actions.is_empty()
+    }
+
     /// Finish the layouting and create a box layout from this.
     pub fn finish(self) -> BoxLayout {
         BoxLayout {
diff --git a/src/layout/flex.rs b/src/layout/flex.rs
index 5fd7b157..f966eae2 100644
--- a/src/layout/flex.rs
+++ b/src/layout/flex.rs
@@ -1,7 +1,7 @@
 //! Flexible and lazy layouting of boxes.
 
 use crate::doc::TextAction;
-use crate::size::Size2D;
+use crate::size::{Size, Size2D};
 use super::{BoxLayout, ActionList, LayoutSpace, LayoutResult, LayoutError};
 
 
@@ -10,8 +10,6 @@ use super::{BoxLayout, ActionList, LayoutSpace, LayoutResult, LayoutError};
 pub struct FlexLayout {
     /// The sublayouts composing this layout.
     pub units: Vec<FlexUnit>,
-    /// The layout space to arrange in.
-    pub ctx: FlexContext,
 }
 
 /// A unit in a flex layout.
@@ -25,14 +23,20 @@ pub enum FlexUnit {
 }
 
 impl FlexLayout {
-    /// Create a new flex layouter.
-    pub fn new(ctx: FlexContext) -> FlexLayout {
+    /// Create a new flex layout.
+    pub fn new() -> FlexLayout {
         FlexLayout {
-            ctx,
             units: vec![],
         }
     }
 
+    /// Create a new flex layout containing just one box.
+    pub fn from_box(boxed: BoxLayout) -> FlexLayout {
+        FlexLayout {
+            units: vec![FlexUnit::Boxed(boxed)],
+        }
+    }
+
     /// Add a sublayout.
     pub fn add_box(&mut self, layout: BoxLayout) {
         self.units.push(FlexUnit::Boxed(layout));
@@ -54,8 +58,8 @@ impl FlexLayout {
     }
 
     /// Compute the justified layout.
-    pub fn into_box(self) -> LayoutResult<BoxLayout> {
-        FlexFinisher::new(self).finish()
+    pub fn finish(self, ctx: FlexContext) -> LayoutResult<BoxLayout> {
+        FlexFinisher::new(self, ctx).finish()
     }
 }
 
@@ -64,8 +68,8 @@ impl FlexLayout {
 pub struct FlexContext {
     /// The space to layout the boxes in.
     pub space: LayoutSpace,
-    /// The flex spacing (like line spacing).
-    pub flex_spacing: f32,
+    /// The flex spacing between two lines of boxes.
+    pub flex_spacing: Size,
 }
 
 /// Finishes a flex layout by justifying the positions of the individual boxes.
@@ -82,11 +86,11 @@ struct FlexFinisher {
 
 impl FlexFinisher {
     /// Create the finisher from the layout.
-    fn new(layout: FlexLayout) -> FlexFinisher {
-        let space = layout.ctx.space;
+    fn new(layout: FlexLayout, ctx: FlexContext) -> FlexFinisher {
+        let space = ctx.space;
         FlexFinisher {
             units: layout.units,
-            ctx: layout.ctx,
+            ctx,
             actions: ActionList::new(),
             dimensions: Size2D::zero(),
             usable: space.usable(),
@@ -165,11 +169,13 @@ impl FlexFinisher {
 
     /// Move to the next line.
     fn newline(&mut self) {
-        self.line.y *= self.ctx.flex_spacing;
         self.dimensions.x = crate::size::max(self.dimensions.x, self.line.x);
+        if self.dimensions.y > Size::zero() {
+            self.dimensions.y += self.ctx.flex_spacing;
+        }
         self.dimensions.y += self.line.y;
         self.cursor.x = self.ctx.space.padding.left;
-        self.cursor.y += self.line.y;
+        self.cursor.y += self.line.y + self.ctx.flex_spacing;
         self.line = Size2D::zero();
     }
 }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index f8819d0b..40948a13 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -70,6 +70,7 @@ struct Layouter<'a, 'p> {
     flex_layout: FlexLayout,
     flex_ctx: FlexContext,
     text_ctx: TextContext<'a, 'p>,
+    func_ctx: LayoutContext<'a, 'p>,
 }
 
 impl<'a, 'p> Layouter<'a, 'p> {
@@ -85,7 +86,7 @@ impl<'a, 'p> Layouter<'a, 'p> {
                 padding: SizeBox::zero(),
                 shrink_to_fit: true,
             },
-            flex_spacing: ctx.style.line_spacing,
+            flex_spacing: (ctx.style.line_spacing - 1.0) * Size::points(ctx.style.font_size),
         };
 
         // The mutable context for layouting single pieces of text.
@@ -94,12 +95,24 @@ impl<'a, 'p> Layouter<'a, 'p> {
             style: ctx.style.clone(),
         };
 
+        // The mutable context for layouting single functions.
+        let func_ctx = LayoutContext {
+            loader: &ctx.loader,
+            style: ctx.style.clone(),
+            space: LayoutSpace {
+                dimensions: ctx.space.usable(),
+                padding: SizeBox::zero(),
+                shrink_to_fit: true,
+            },
+        };
+
         Layouter {
             tree,
             box_layouter: BoxLayouter::new(box_ctx),
-            flex_layout: FlexLayout::new(flex_ctx),
+            flex_layout: FlexLayout::new(),
             flex_ctx,
             text_ctx,
+            func_ctx,
         }
     }
 
@@ -124,28 +137,53 @@ impl<'a, 'p> Layouter<'a, 'p> {
                 // Then start a new flex layouting process.
                 Node::Newline => {
                     // Finish the current paragraph into a box and add it.
-                    self.add_paragraph_spacing()?;
-                    let boxed = self.flex_layout.into_box()?;
+                    let boxed = self.flex_layout.finish(self.flex_ctx)?;
                     self.box_layouter.add_box(boxed)?;
 
                     // Create a fresh flex layout for the next paragraph.
                     self.flex_ctx.space.dimensions = self.box_layouter.remaining();
-                    self.flex_layout = FlexLayout::new(self.flex_ctx);
+                    self.flex_layout = FlexLayout::new();
+                    self.add_paragraph_spacing()?;
                 },
 
                 // Toggle the text styles.
-                Node::ToggleItalics => self.text_ctx.style.italic = !self.text_ctx.style.italic,
-                Node::ToggleBold => self.text_ctx.style.bold = !self.text_ctx.style.bold,
+                Node::ToggleItalics => {
+                    self.text_ctx.style.italic = !self.text_ctx.style.italic;
+                    self.func_ctx.style.italic = !self.func_ctx.style.italic;
+                },
+                Node::ToggleBold => {
+                    self.text_ctx.style.bold = !self.text_ctx.style.bold;
+                    self.func_ctx.style.bold = !self.func_ctx.style.bold;
+                },
 
                 // Execute a function.
-                Node::Func(_) => unimplemented!(),
+                Node::Func(func) => {
+                    self.func_ctx.space.dimensions = self.box_layouter.remaining();
+                    let layout = func.body.layout(&self.func_ctx)?;
+
+                    // Add the potential layout.
+                    if let Some(layout) = layout {
+                        match layout {
+                            Layout::Boxed(boxed) => {
+                                // Finish the previous flex run before adding the box.
+                                let previous = self.flex_layout.finish(self.flex_ctx)?;
+                                self.box_layouter.add_box(previous)?;
+                                self.box_layouter.add_box(boxed)?;
+
+                                // Create a fresh flex layout for the following content.
+                                self.flex_ctx.space.dimensions = self.box_layouter.remaining();
+                                self.flex_layout = FlexLayout::new();
+                            },
+                            Layout::Flex(flex) => self.flex_layout.add_flexible(flex),
+                        }
+                    }
+                },
             }
         }
 
         // If there are remainings, add them to the layout.
         if !self.flex_layout.is_empty() {
-            self.add_paragraph_spacing()?;
-            let boxed = self.flex_layout.into_box()?;
+            let boxed = self.flex_layout.finish(self.flex_ctx)?;
             self.box_layouter.add_box(boxed)?;
         }
 
diff --git a/src/lib.rs b/src/lib.rs
index 334f20b9..4799188b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -216,7 +216,7 @@ mod test {
     #[test]
     fn features() {
         test("features", r"
-            **FEATURES TEST PAGE**
+            **Features Test Page**
 
             __Multiline:__
             Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy
@@ -226,7 +226,10 @@ mod test {
 
             __Emoji:__ Hello World! 🌍
 
-            __Styles:__ This is **bold** and that is __italic__!
+            __Styles:__ This is made **bold** and that __italic__ using the built-in syntax!
+
+            __Styles with functions:__ This is in [bold][boldface] and that is in [italic][italics]
+            using library functions!
         ");
     }
 
diff --git a/src/parsing.rs b/src/parsing.rs
index 727a06d8..81a729ab 100644
--- a/src/parsing.rs
+++ b/src/parsing.rs
@@ -822,8 +822,7 @@ mod parse_tests {
                 }
             }
 
-            fn layout(&self, _: &LayoutContext)
-                -> LayoutResult<(Option<Layout>, Option<LayoutContext>)> { Ok((None, None)) }
+            fn layout(&self, _: &LayoutContext) -> LayoutResult<Option<Layout>> { Ok(None) }
         }
 
         /// A testing function without a body.
@@ -840,8 +839,7 @@ mod parse_tests {
                 }
             }
 
-            fn layout(&self, _: &LayoutContext)
-                -> LayoutResult<(Option<Layout>, Option<LayoutContext>)> { Ok((None, None)) }
+            fn layout(&self, _: &LayoutContext) -> LayoutResult<Option<Layout>> { Ok(None) }
         }
     }
 
diff --git a/src/style.rs b/src/style.rs
index 97f9552c..cd0a9579 100644
--- a/src/style.rs
+++ b/src/style.rs
@@ -30,7 +30,7 @@ impl Default for TextStyle {
             italic: false,
             bold: false,
             font_size: 11.0,
-            line_spacing: 1.25,
+            line_spacing: 1.2,
             paragraph_spacing: 1.5,
         }
     }