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-//! Core typesetting engine.
-
-use std::cell::Ref;
-use std::mem::swap;
-
-use smallvec::SmallVec;
-
-use crate::doc::{Document, Page, Text, TextCommand};
-use crate::font::{Font, FontFamily, FontProvider, FontError};
-use crate::syntax::{SyntaxTree, Node};
-use loader::{FontLoader, FontQuery};
-
-mod size;
-mod loader;
-pub use size::Size;
-
-
-/// Typeset a parsed syntax tree.
-pub fn typeset<'p>(tree: &SyntaxTree, style: &Style, font_providers: &[Box<dyn FontProvider + 'p>])
- -> TypesetResult<Document> {
- Engine::new(tree, style, font_providers).typeset()
-}
-
-
-/// The core typesetting engine, transforming an abstract syntax tree into a document.
-struct Engine<'a> {
- // Input
- tree: &'a SyntaxTree,
- style: &'a Style,
-
- // Internal
- font_loader: FontLoader<'a>,
-
- // Output
- text_commands: Vec<TextCommand>,
-
- // Intermediates
- active_font: usize,
- current_text: String,
- current_line_width: Size,
- current_max_vertical_move: Size,
- bold: bool,
- italic: bool,
-}
-
-impl<'a> Engine<'a> {
- /// Create a new generator from a syntax tree.
- fn new(
- tree: &'a SyntaxTree,
- style: &'a Style,
- font_providers: &'a [Box<dyn FontProvider + 'a>]
- ) -> Engine<'a> {
- Engine {
- tree,
- style,
- font_loader: FontLoader::new(font_providers),
- text_commands: vec![],
- active_font: std::usize::MAX,
- current_text: String::new(),
- current_line_width: Size::zero(),
- current_max_vertical_move: Size::zero(),
- italic: false,
- bold: false,
- }
- }
-
- /// Generate the abstract document.
- fn typeset(mut self) -> TypesetResult<Document> {
- // Start by moving to a suitable position.
- self.move_start();
-
- // Iterate through the documents nodes.
- for node in &self.tree.nodes {
- match node {
- Node::Text(text) => self.write_word(text)?,
- Node::Space => self.write_space()?,
- Node::Newline => {
- self.write_buffered_text();
- self.move_newline(self.style.paragraph_spacing);
- },
-
- Node::ToggleItalics => self.italic = !self.italic,
- Node::ToggleBold => self.bold = !self.bold,
-
- Node::ToggleMath => unimplemented!(),
- Node::Func(_) => unimplemented!(),
- }
- }
-
- // Flush the text buffer.
- self.write_buffered_text();
-
- // Create a document with one page from the contents.
- Ok(Document {
- pages: vec![Page {
- width: self.style.width,
- height: self.style.height,
- text: vec![Text {
- commands: self.text_commands,
- }],
- }],
- fonts: self.font_loader.into_fonts(),
- })
- }
-
- /// Write a word.
- fn write_word(&mut self, word: &str) -> TypesetResult<()> {
- // Contains pairs of (characters, font_index, char_width).
- let mut chars_with_widths = SmallVec::<[(char, usize, Size); 12]>::new();
-
- // Find out which font to use for each character in the word and meanwhile
- // calculate the width of the word.
- let mut word_width = Size::zero();
- for c in word.chars() {
- let (index, font) = self.get_font_for(c)?;
- let width = self.char_width(c, &font);
- word_width += width;
- chars_with_widths.push((c, index, width));
- }
-
- // If this would overflow, we move to a new line and finally write the previous one.
- if self.would_overflow(word_width) {
- self.write_buffered_text();
- self.move_newline(1.0);
- }
-
- // Finally write the word.
- for (c, index, width) in chars_with_widths {
- if index != self.active_font {
- // If we will change the font, first write the remaining things.
- self.write_buffered_text();
- self.set_font(index);
- }
-
- self.current_text.push(c);
- self.current_line_width += width;
- }
-
- Ok(())
- }
-
- /// Write the space character: `' '`.
- fn write_space(&mut self) -> TypesetResult<()> {
- let space_width = self.char_width(' ', &self.get_font_for(' ')?.1);
- if !self.would_overflow(space_width) && self.current_line_width > Size::zero() {
- self.write_word(" ")?;
- }
-
- Ok(())
- }
-
- /// Write a text command with the buffered text.
- fn write_buffered_text(&mut self) {
- if !self.current_text.is_empty() {
- let mut current_text = String::new();
- swap(&mut self.current_text, &mut current_text);
- self.text_commands.push(TextCommand::Text(current_text));
- }
- }
-
- /// Move to the starting position defined by the style.
- fn move_start(&mut self) {
- // Move cursor to top-left position
- self.text_commands.push(TextCommand::Move(
- self.style.margin_left,
- self.style.height - self.style.margin_top
- ));
- }
-
- /// Move to a new line.
- fn move_newline(&mut self, factor: f32) {
- if self.active_font == std::usize::MAX {
- return;
- }
-
- let vertical_move = if self.current_max_vertical_move == Size::zero() {
- // If max vertical move is still zero, the line is empty and we take the
- // font size from the previous line.
- self.style.font_size
- * self.style.line_spacing
- * self.get_font_at(self.active_font).metrics.ascender
- * factor
- } else {
- self.current_max_vertical_move
- };
-
- self.text_commands.push(TextCommand::Move(Size::zero(), -vertical_move));
- self.current_max_vertical_move = Size::zero();
- self.current_line_width = Size::zero();
- }
-
- /// Set the current font.
- fn set_font(&mut self, index: usize) {
- self.text_commands.push(TextCommand::SetFont(index, self.style.font_size));
- self.active_font = index;
- }
-
- /// Whether the current line plus the extra `width` would overflow the line.
- fn would_overflow(&self, width: Size) -> bool {
- let max_width = self.style.width
- - self.style.margin_left - self.style.margin_right;
- self.current_line_width + width > max_width
- }
-
- /// Load a font that has the character we need.
- fn get_font_for(&self, character: char) -> TypesetResult<(usize, Ref<Font>)> {
- self.font_loader.get(FontQuery {
- families: &self.style.font_families,
- italic: self.italic,
- bold: self.bold,
- character,
- }).ok_or_else(|| TypesetError::MissingFont)
- }
-
- /// Load a font at an index.
- fn get_font_at(&self, index: usize) -> Ref<Font> {
- self.font_loader.get_with_index(index)
- }
-
- /// The width of a char in a specific font.
- fn char_width(&self, character: char, font: &Font) -> Size {
- font.widths[font.map(character) as usize] * self.style.font_size
- }
-}
-
-/// The context for typesetting a function.
-#[derive(Debug)]
-pub struct TypesetContext {}
-
-/// Default styles for typesetting.
-#[derive(Debug, Clone, PartialEq)]
-pub struct Style {
- /// The width of the paper.
- pub width: Size,
- /// The height of the paper.
- pub height: Size,
-
- /// The left margin of the paper.
- pub margin_left: Size,
- /// The top margin of the paper.
- pub margin_top: Size,
- /// The right margin of the paper.
- pub margin_right: Size,
- /// The bottom margin of the paper.
- pub margin_bottom: Size,
-
- /// 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 spacing for paragraphs (as a multiple of the line spacing).
- pub paragraph_spacing: f32,
-}
-
-impl Default for Style {
- fn default() -> Style {
- use FontFamily::*;
- Style {
- // A4 paper.
- width: Size::from_mm(210.0),
- height: Size::from_mm(297.0),
-
- // Margins. A bit more on top and bottom.
- 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),
-
- // 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,
- }
- }
-}
-
-/// The error type for typesetting.
-pub enum TypesetError {
- /// There was no suitable font.
- MissingFont,
- /// An error occured while gathering font data.
- Font(FontError),
-}
-
-/// The result type for typesetting.
-pub type TypesetResult<T> = Result<T, TypesetError>;
-
-error_type! {
- err: TypesetError,
- show: f => match err {
- TypesetError::MissingFont => write!(f, "missing font"),
- TypesetError::Font(err) => write!(f, "font error: {}", err),
- },
- source: match err {
- TypesetError::Font(err) => Some(err),
- _ => None,
- },
- from: (std::io::Error, TypesetError::Font(FontError::Io(err))),
- from: (FontError, TypesetError::Font(err)),
-}
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