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//! Core typesetting engine.
use std::error;
use std::fmt;
use crate::syntax::{SyntaxTree, Node};
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> {
// 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: &'s SyntaxTree<'s>, style: Style) -> Engine<'s> {
Engine {
style,
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> {
// Load font defined by style
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();
self.fonts.push(font);
self.active_font = 0;
// Move cursor to top-left position
self.text_commands.push(TextCommand::Move(
self.style.margin_left,
self.style.height - self.style.margin_top
));
// 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::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 {
width: self.style.width,
height: self.style.height,
text: vec![Text {
commands: self.text_commands,
}],
};
Ok(Document {
pages: vec![page],
fonts: self.fonts,
})
}
fn write_word(&mut self, word: &str) {
let font = &self.fonts[self.active_font];
let width = self.width(word);
if self.would_overflow(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) {
let space_width = self.width(" ");
if !self.would_overflow(space_width) && !self.current_line.is_empty() {
self.text_commands.push(TextCommand::Text(" ".to_owned()));
self.current_line.push_str(" ");
self.current_width += space_width;
}
}
fn width(&self, word: &str) -> Size {
let font = &self.fonts[self.active_font];
word.chars()
.map(|c| font.widths[font.map(c) as usize] * self.style.font_size)
.sum()
}
fn would_overflow(&self, width: Size) -> bool {
let max_width = self.style.width
- self.style.margin_left
- self.style.margin_right;
self.current_width + width > max_width
}
}
/// Result type used for parsing.
type TypeResult<T> = std::result::Result<T, TypesetError>;
/// The error type for typesetting.
pub enum TypesetError {}
impl error::Error for TypesetError {}
impl fmt::Display for TypesetError {
#[inline]
fn fmt(&self, _: &mut fmt::Formatter) -> fmt::Result {
Ok(())
}
}
impl fmt::Debug for TypesetError {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Display::fmt(self, f)
}
}
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