Basic multiline support 📜

4 files changed, 241 insertions, 37 deletions

diff --git a/src/doc.rs b/src/doc.rs
index bff4926a..3e060f6e 100644
--- a/src/doc.rs
+++ b/src/doc.rs
@@ -1,6 +1,5 @@
 //! Abstract representation of a typesetted document.
 
-use std::ops;
 use crate::font::Font;
 
 
@@ -23,8 +22,10 @@ pub struct Style {
 
     /// A fallback list of font families to use.
     pub font_families: Vec<String>,
-    /// The default font size.
+    /// The font size.
     pub font_size: f32,
+    /// The line spacing (as a multiple of the font size).
+    pub line_spacing: f32,
 }
 
 impl Default for Style {
@@ -39,6 +40,7 @@ impl Default for Style {
                 "NotoSans", "NotoSansMath"
             ]).iter().map(ToString::to_string).collect(),
             font_size: 12.0,
+            line_spacing: 1.25,
         }
     }
 }
@@ -78,6 +80,10 @@ pub struct Size {
 }
 
 impl Size {
+    /// Create an zeroed size.
+    #[inline]
+    pub fn zero() -> Size { Size { points: 0.0 } }
+
     /// Create a size from a number of points.
     #[inline]
     pub fn from_points(points: f32) -> Size { Size { points } }
@@ -111,18 +117,98 @@ impl Size {
     pub fn to_cm(&self) -> f32 { self.points * 0.0352778 }
 }
 
-impl ops::Add for Size {
-    type Output = Size;
+mod size {
+    use super::Size;
+    use std::cmp::Ordering;
+    use std::fmt;
+    use std::iter::Sum;
+    use std::ops::*;
 
-    fn add(self, other: Size) -> Size {
-        Size { points: self.points + other.points }
+    impl fmt::Display for Size {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            write!(f, "{}pt", self.points)
+        }
     }
-}
 
-impl ops::Sub for Size {
-    type Output = Size;
+    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 Neg for Size {
+        type Output = Size;
+
+        fn neg(self) -> Size {
+            Size { points: -self.points }
+        }
+    }
 
-    fn sub(self, other: Size) -> Size {
-        Size { points: self.points - 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 PartialOrd for Size {
+        fn partial_cmp(&self, other: &Size) -> Option<Ordering> {
+            self.points.partial_cmp(&other.points)
+        }
+    }
+
+    impl Sum for Size {
+        fn sum<I>(iter: I) -> Size where I: Iterator<Item=Size> {
+            iter.fold(Size::zero(), Add::add)
+        }
     }
 }
diff --git a/src/engine.rs b/src/engine.rs
index 34f98766..ef50ecb4 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -3,59 +3,114 @@
 use std::error;
 use std::fmt;
 use crate::syntax::{SyntaxTree, Node};
-use crate::doc::{Document, Style, Page, Text, TextCommand};
+use crate::doc::{Document, Style, Size, Page, Text, TextCommand};
 use crate::font::Font;
 
 
 /// The core typesetting engine, transforming an abstract syntax tree into a document.
 #[derive(Debug, Clone)]
 pub struct Engine<'s> {
-    tree: SyntaxTree<'s>,
+    // Immutable
+    tree: &'s SyntaxTree<'s>,
+    style: Style,
+
+    // Mutable
+    fonts: Vec<Font>,
+    active_font: usize,
+    text_commands: Vec<TextCommand>,
+    current_line: String,
+    current_width: Size,
 }
 
 impl<'s> Engine<'s> {
     /// Create a new generator from a syntax tree.
-    pub fn new(tree: SyntaxTree<'s>) -> Engine<'s> {
-        Engine { tree }
+    pub fn new(tree: &'s SyntaxTree<'s>) -> Engine<'s> {
+        Engine {
+            style: Style::default(),
+            tree,
+            fonts: Vec::new(),
+            active_font: 0,
+            text_commands: Vec::new(),
+            current_line: String::new(),
+            current_width: Size::zero(),
+        }
     }
 
     /// Generate the abstract document.
-    pub fn typeset(&mut self) -> TypeResult<Document> {
-        let style = Style::default();
-
+    pub fn typeset(mut self) -> TypeResult<Document> {
         // Load font defined by style
-        let font_family = style.font_families.first().unwrap();
+        let font_family = self.style.font_families.first().unwrap();
         let program = std::fs::read(format!("../fonts/{}-Regular.ttf", font_family)).unwrap();
         let font = Font::new(program).unwrap();
 
-        let mut text = String::new();
+        self.fonts.push(font);
+        self.active_font = 0;
+
+        // Move cursor to top-left position
+        self.text_commands.push(TextCommand::Move(
+            self.style.margins[0],
+            self.style.paper_size[1] - self.style.margins[1])
+        );
+
+        // Set the current font
+        self.text_commands.push(TextCommand::SetFont(0, self.style.font_size));
+
+        // Iterate through the documents nodes.
         for node in &self.tree.nodes {
             match node {
-                Node::Space if !text.is_empty() => text.push(' '),
-                Node::Space | Node::Newline => (),
-                Node::Word(word) => text.push_str(word),
+                Node::Word(word) => self.write_word(word),
+
+                Node::Space => self.write_space(),
+                Node::Newline => (),
 
                 Node::ToggleItalics | Node::ToggleBold | Node::ToggleMath => unimplemented!(),
                 Node::Func(_) => unimplemented!(),
             }
         }
 
+        // Create a page from the contents.
         let page = Page {
-            size: style.paper_size,
+            size: self.style.paper_size,
             text: vec![Text {
-                commands: vec![
-                    TextCommand::Move(style.margins[0], style.paper_size[1] - style.margins[1]),
-                    TextCommand::SetFont(0, style.font_size),
-                    TextCommand::Text(text)
-                ]
+                commands: self.text_commands,
             }],
         };
 
         Ok(Document {
             pages: vec![page],
-            fonts: vec![font],
+            fonts: self.fonts,
         })
     }
+
+    fn write_word(&mut self, word: &str) {
+        let max_width = self.style.paper_size[0] - 2 * self.style.margins[0];
+
+        let font = &self.fonts[self.active_font];
+        let width = word.chars()
+            .map(|c| font.widths[font.map(c) as usize] * self.style.font_size)
+            .sum();
+
+
+        if self.current_width + width > max_width {
+            let vertical_move = - self.style.font_size
+                * self.style.line_spacing
+                * font.metrics.ascender;
+            self.text_commands.push(TextCommand::Move(Size::zero(), vertical_move));
+
+            self.current_line.clear();
+            self.current_width = Size::zero();
+        }
+
+        self.text_commands.push(TextCommand::Text(word.to_owned()));
+        self.current_line.push_str(word);
+        self.current_width += width;
+    }
+
+    fn write_space(&mut self) {
+        if !self.current_line.is_empty() {
+            self.write_word(" ");
+        }
+    }
 }
 
 /// Result type used for parsing.
diff --git a/src/font.rs b/src/font.rs
index 30542391..c90fb983 100644
--- a/src/font.rs
+++ b/src/font.rs
@@ -23,6 +23,15 @@ pub struct Font {
     pub widths: Vec<Size>,
     /// The fallback glyph.
     pub default_glyph: u16,
+    /// The relevant metrics of this font.
+    pub metrics: FontMetrics,
+}
+
+/// Font metrics relevant to the typesetting engine.
+#[derive(Debug, Clone, PartialEq)]
+pub struct FontMetrics {
+    /// The typographics ascender relevant for line spacing.
+    pub ascender: Size,
 }
 
 impl Font {
@@ -44,12 +53,17 @@ impl Font {
         let font_name =  base_font.unwrap_or_else(|| "unknown".to_owned());
         let widths = hmtx.metrics.iter().map(|m| convert(m.advance_width)).collect();
 
+        let metrics = FontMetrics {
+            ascender: convert(os2.s_typo_ascender),
+        };
+
         Ok(Font {
             name: font_name,
             program,
             mapping: charmap.mapping,
             widths,
             default_glyph: os2.us_default_char.unwrap_or(0),
+            metrics,
         })
     }
 
@@ -62,7 +76,6 @@ impl Font {
     /// Encode the given text for this font (into glyph ids).
     #[inline]
     pub fn encode(&self, text: &str) -> Vec<u8> {
-        println!("encoding {} with {:?}", text, self.mapping);
         let mut bytes = Vec::with_capacity(2 * text.len());
         for glyph in text.chars().map(|c| self.map(c)) {
             bytes.push((glyph >> 8) as u8);
@@ -181,6 +194,7 @@ impl<'p> Subsetter<'p> {
             mapping,
             widths,
             default_glyph: self.font.default_glyph,
+            metrics: self.font.metrics.clone(),
         })
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index e9d0b1b4..deb5b066 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -68,7 +68,8 @@ impl<'s> Compiler<'s> {
     /// Return the abstract typesetted representation of the document.
     #[inline]
     pub fn typeset(&self) -> Result<Document, Error> {
-        Engine::new(self.parse()?).typeset().map_err(Into::into)
+        let tree = self.parse()?;
+        Engine::new(&tree).typeset().map_err(Into::into)
     }
 
     /// Write the document as a _PDF_, returning how many bytes were written.
@@ -145,15 +146,63 @@ mod test {
     }
 
     #[test]
-    fn pdf() {
+    fn pdfs() {
         test("unicode", "∑mbe∂∂ed font with Unicode!");
         test("parentheses", "Text with ) and ( or (enclosed) works.");
         test("composite-glyph", "Composite character‼");
         test("multiline","
-             Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed
-             diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed
-             diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum.
-             Stet clita kasd gubergren, no sea takimata sanctus est.
+            Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy
+            eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam
+            voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet
+            clita kasd gubergren, no sea takimata sanctus est.
         ");
     }
+
+    #[test]
+    fn long() {
+        test("wikipedia", r#"
+            Typesetting is the composition of text by means of arranging physical types or the
+            digital equivalents. Stored letters and other symbols (called sorts in mechanical
+            systems and glyphs in digital systems) are retrieved and ordered according to a
+            language's orthography for visual display. Typesetting requires one or more fonts
+            (which are widely but erroneously confused with and substituted for typefaces). One
+            significant effect of typesetting was that authorship of works could be spotted more
+            easily, making it difficult for copiers who have not gained permission.
+
+            During much of the letterpress era, movable type was composed by hand for each page.
+            Cast metal sorts were composed into words, then lines, then paragraphs, then pages of
+            text and tightly bound together to make up a form, with all letter faces exactly the
+            same "height to paper", creating an even surface of type. The form was placed in a
+            press, inked, and an impression made on paper.
+
+            During typesetting, individual sorts are picked from a type case with the right hand,
+            and set into a composing stick held in the left hand from left to right, and as viewed
+            by the setter upside down. As seen in the photo of the composing stick, a lower case
+            'q' looks like a 'd', a lower case 'b' looks like a 'p', a lower case 'p' looks like a
+            'b' and a lower case 'd' looks like a 'q'. This is reputed to be the origin of the
+            expression "mind your p's and q's". It might just as easily have been "mind your b's
+            and d's".
+
+            The diagram at right illustrates a cast metal sort: a face, b body or shank, c point
+            size, 1 shoulder, 2 nick, 3 groove, 4 foot. Wooden printing sorts were in use for
+            centuries in combination with metal type. Not shown, and more the concern of the
+            casterman, is the “set”, or width of each sort. Set width, like body size, is measured
+            in points.
+
+            In order to extend the working life of type, and to account for the finite sorts in a
+            case of type, copies of forms were cast when anticipating subsequent printings of a
+            text, freeing the costly type for other work. This was particularly prevalent in book
+            and newspaper work where rotary presses required type forms to wrap an impression
+            cylinder rather than set in the bed of a press. In this process, called stereotyping,
+            the entire form is pressed into a fine matrix such as plaster of Paris or papier mâché
+            called a flong to create a positive, from which the stereotype form was electrotyped,
+            cast of type metal.
+
+            Advances such as the typewriter and computer would push the state of the art even
+            farther ahead. Still, hand composition and letterpress printing have not fallen
+            completely out of use, and since the introduction of digital typesetting, it has seen a
+            revival as an artisanal pursuit. However, it is a very small niche within the larger
+            typesetting market.
+        "#);
+    }
 }