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// "fonterator" crate - Licensed under the MIT LICENSE
// * Copyright (c) 2018 Jeron A. Lau <jeron.lau@plopgrizzly.com>
// * Copyright (c) 2016 Dylan Ede
//! Fonterator is a pure Rust alternative to libraries like FreeType based on
//! RustType.
//!
//! # Getting Started
//! Add the following to your Cargo.toml:
//!
//! ```toml
//! [dependencies]
//! fonterator = "0.1.0"
//! ```
//!
//! To hit the ground running with Fonterator, look at the `image.rs` example
//! supplied with the crate. It demonstrates loading a font file, rasterising an
//! arbitrary string, and saving as an SVG. If you prefer to
//! just look at the documentation, the entry point for loading fonts is
//! `FontCollection`, from which you can access individual fonts, then their
//! glyphs.
//!
//! # Unicode terminology
//!
//! This crate uses terminology for computerised typography as specified by the
//! Unicode standard. If you are not sure of the differences between a code
//! point, a character, and a glyph, you may want to check the [official Unicode
//! glossary](http://unicode.org/glossary/), or alternatively, here's my take on
//! it from a practical perspective:
//!
//! * A character is what you would conventionally call a single symbol,
//! independent of its appearance or representation in a particular font.
//! Examples include `a`, `A`, `ä`, `å`, `1`, `*`, `Ω`, etc.
//! * A Unicode code point is the particular number that the Unicode standard
//! associates with a particular character. Note however that code points also
//! exist for things not conventionally thought of as characters by
//! themselves, but can be combined to form characters, such as diacritics
//! like accents. These "characters" are known in Unicode as "combining
//! characters". E.g., a diaeresis (`¨`) has the code point U+0308. If this
//! code point follows the code point U+0055 (the letter `u`), this sequence
//! represents the character `ü`. Note that there is also a single codepoint
//! for `ü`, U+00FC. This means that what visually looks like the same string
//! can have multiple different Unicode representations. Some fonts will have
//! glyphs (see below) for one sequence of codepoints, but not another that
//! has the same meaning. To deal with this problem it is recommended to use
//! Unicode normalisation, as provided by, for example, the
//! [unicode-normalization](http://crates.io/crates/unicode-normalization)
//! crate, to convert to code point sequences that work with the font in
//! question. Typically a font is more likely to support a single code point
//! vs. a sequence with the same meaning, so the best normalisation to use is
//! "canonical recomposition", known as NFC in the normalisation crate.
//! * A glyph is a particular font's shape to draw the character for a
//! particular Unicode code point. This will have its own identifying number
//! unique to the font, its ID.
extern crate byteorder;
extern crate footile;
extern crate unicode_normalization;
mod tt;
pub use footile::{ PathOp, PathBuilder, Path2D };
use unicode_normalization::UnicodeNormalization;
use std::fmt;
use std::sync::Arc;
/// A 2D vector
#[derive(Copy, Clone)]
struct Vec2(pub f32, pub f32);
/// A collection of fonts read straight from a font file's data. The data in the
/// collection is not validated. This structure may or may not own the font
/// data.
#[derive(Clone, Debug)]
pub struct FontCollection<'a>(SharedBytes<'a>);
/// A single font. This may or may not own the font data.
#[derive(Clone)]
pub struct Font<'a> {
info: tt::FontInfo<SharedBytes<'a>>,
}
/// `SharedBytes` handles the lifetime of font data used in Fonterator. The data
/// is either a shared reference to externally owned data, or managed by
/// reference counting. `SharedBytes` can be conveniently used with `From` and
/// `Into`, and dereferences to the contained bytes.
#[derive(Clone, Debug)]
pub enum SharedBytes<'a> {
ByRef(&'a [u8]),
ByArc(Arc<[u8]>),
}
impl<'a> ::std::ops::Deref for SharedBytes<'a> {
type Target = [u8];
fn deref(&self) -> &[u8] {
match *self {
SharedBytes::ByRef(bytes) => bytes,
SharedBytes::ByArc(ref bytes) => &**bytes,
}
}
}
impl<'a> From<&'a [u8]> for SharedBytes<'a> {
fn from(bytes: &'a [u8]) -> SharedBytes<'a> {
SharedBytes::ByRef(bytes)
}
}
impl From<Arc<[u8]>> for SharedBytes<'static> {
fn from(bytes: Arc<[u8]>) -> SharedBytes<'static> {
SharedBytes::ByArc(bytes)
}
}
impl From<Box<[u8]>> for SharedBytes<'static> {
fn from(bytes: Box<[u8]>) -> SharedBytes<'static> {
SharedBytes::ByArc(bytes.into())
}
}
impl From<Vec<u8>> for SharedBytes<'static> {
fn from(bytes: Vec<u8>) -> SharedBytes<'static> {
SharedBytes::ByArc(bytes.into())
}
}
/// Represents a Unicode code point.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
struct Codepoint(pub u32);
/// Represents a glyph identifier for a particular font. This identifier will not necessarily
/// correspond to the correct glyph in a font other than the one that it was obtained from.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
struct GlyphId(pub u32);
/// A single glyph of a font. this is a thin wrapper referring to the font,
/// glyph id and scaling information.
#[derive(Clone)]
pub struct Glyph<'a> {
inner: GlyphInner<'a>,
v: Vec2,
}
#[derive(Clone)]
struct GlyphInner<'a>(Font<'a>, u32);
/// The "horizontal metrics" of a glyph. This is useful for calculating the
/// horizontal offset of a glyph from the previous one in a string when laying a
/// string out horizontally.
#[derive(Copy, Clone, Debug, PartialEq, PartialOrd)]
struct HMetrics {
/// The horizontal offset that the origin of the next glyph should be from
/// the origin of this glyph.
pub advance_width: f32,
/// The horizontal offset between the origin of this glyph and the leftmost
/// edge/point of the glyph.
pub left_side_bearing: f32,
}
#[derive(Copy, Clone, Debug, PartialEq, PartialOrd)]
/// The "vertical metrics" of a font at a particular scale. This is useful for
/// calculating the amount of vertical space to give a line of text, and for
/// computing the vertical offset between successive lines.
struct VMetrics {
/// The highest point that any glyph in the font extends to above the
/// baseline. Typically positive.
pub ascent: f32,
/// The lowest point that any glyph in the font extends to below the
/// baseline. Typically negative.
pub descent: f32,
/// The gap to leave between the descent of one line and the ascent of the
/// next. This is of course only a guideline given by the font's designers.
pub line_gap: f32,
}
impl From<tt::VMetrics> for VMetrics {
fn from(vm: tt::VMetrics) -> Self {
Self {
ascent: vm.ascent as f32,
descent: vm.descent as f32,
line_gap: vm.line_gap as f32,
}
}
}
/// A trait for types that can be converted into a `GlyphId`, in the context of
/// a specific font.
///
/// Many `fonterator` functions that operate on characters accept values of any
/// type that implements `IntoGlyphId`. Such types include `char`, `Codepoint`,
/// and obviously `GlyphId` itself.
trait IntoGlyphId {
/// Convert `self` into a `GlyphId`, consulting the index map of `font` if
/// necessary.
fn into_glyph_id(self, &Font) -> GlyphId;
}
impl IntoGlyphId for char {
fn into_glyph_id(self, font: &Font) -> GlyphId {
GlyphId(font.info.find_glyph_index(self as u32))
}
}
impl IntoGlyphId for Codepoint {
fn into_glyph_id(self, font: &Font) -> GlyphId {
GlyphId(font.info.find_glyph_index(self.0))
}
}
impl IntoGlyphId for GlyphId {
fn into_glyph_id(self, _font: &Font) -> GlyphId {
self
}
}
impl<'a> FontCollection<'a> {
/// Constructs a font collection from an array of bytes, typically loaded
/// from a font file, which may be a single font or a TrueType Collection
/// holding a number of fonts. This array may be owned (e.g. `Vec<u8>`), or
/// borrowed (`&[u8]`). As long as `From<T>` is implemented for `Bytes` for
/// some type `T`, `T` can be used as input.
///
/// This returns an error if `bytes` does not seem to be font data in a
/// format we recognize.
pub fn new<B: Into<SharedBytes<'a>>>(bytes: B) -> Result<FontCollection<'a>, Error> {
let bytes = bytes.into();
// We should use tt::is_collection once it lands in stb_truetype-rs:
// https://github.com/redox-os/stb_truetype-rs/pull/15
if !tt::is_font(&bytes) && &bytes[0..4] != b"ttcf" {
return Err(Error::UnrecognizedFormat);
}
Ok(FontCollection(bytes))
}
/// If this `FontCollection` holds a single font, or a TrueType Collection
/// containing only one font, return that as a `Font`. The `FontCollection`
/// is consumed.
///
/// If this `FontCollection` holds multiple fonts, return a
/// `CollectionContainsMultipleFonts` error.
///
/// If an error occurs, the `FontCollection` is lost, since this function
/// takes ownership of it, and the error values don't give it back. If that
/// is a problem, use the `font_at` or `into_fonts` methods instead, which
/// borrow the `FontCollection` rather than taking ownership of it.
pub fn into_font(self) -> Result<Font<'a>, Error> {
let offset = if tt::is_font(&self.0) {
0
} else if tt::get_font_offset_for_index(&self.0, 1).is_some() {
return Err(Error::CollectionContainsMultipleFonts);
} else {
// We now know that either a) `self.0` is a collection with only one
// font, or b) `get_font_offset_for_index` found data it couldn't
// recognize. Request the first font's offset, distinguishing
// those two cases.
match tt::get_font_offset_for_index(&self.0, 0) {
None => return Err(Error::IllFormed),
Some(offset) => offset,
}
};
let info = tt::FontInfo::new(self.0, offset as usize).ok_or(Error::IllFormed)?;
Ok(Font { info })
}
/// Gets the font at index `i` in the font collection, if it exists and is
/// valid. The produced font borrows the font data that is either borrowed
/// or owned by this font collection.
pub fn font_at(&self, i: usize) -> Result<Font<'a>, Error> {
let offset = tt::get_font_offset_for_index(&self.0, i as i32)
.ok_or(Error::CollectionIndexOutOfBounds)?;
let info = tt::FontInfo::new(self.0.clone(), offset as usize).ok_or(Error::IllFormed)?;
Ok(Font { info })
}
/// Converts `self` into an `Iterator` yielding each `Font` that exists
/// within the collection.
pub fn into_fonts(self) -> Vec<Font<'a>> {
let mut fonts = vec![];
let mut index = 0;
loop {
let result = self.font_at(index);
if let Err(Error::CollectionIndexOutOfBounds) = result {
break;
}
index += 1;
fonts.push(result.unwrap());
}
fonts
}
}
/// An iterator over glyphs in a string.
pub struct GlyphIterator<'a> {
// The font
font: &'a Font<'a>,
// Scaling info
api_scale: (f32, f32),
// ...
scale: Vec2,
// Normalized string
string: Vec<char>,
// Which character in the string
cursor: usize,
// The previous glyph
last: Option<Glyph<'a>>,
}
impl<'a> Iterator for GlyphIterator<'a> {
type Item = (Glyph<'a>, f32, bool);
fn next(&mut self) -> Option<(Glyph<'a>, f32, bool)> {
let c = self.string.get(self.cursor);
if let Some(c) = c {
let glyph: Glyph<'a> = self.font.glyph(*c, self.scale);
let mut advance = self
.font
.info
.get_glyph_h_metrics(glyph.id().0)
.advance_width as f32
* self.scale.0;
if self.cursor != 0 {
advance += self.font.kerning(
self.api_scale,
self.scale,
self.last.as_ref().unwrap(),
&glyph,
);
}
self.last = Some(glyph.clone());
self.cursor += 1;
Some((glyph, advance, *c == '\n'))
} else {
None
}
}
}
impl<'a> Font<'a> {
/// Constructs a font from an array of bytes, this is a shortcut for
/// `FontCollection::new` for collections comprised of a single font.
pub fn new<B: Into<SharedBytes<'a>>>(bytes: B) -> Result<Font<'a>, Error> {
FontCollection::new(bytes).and_then(|c| c.into_font())
}
/// The "vertical metrics" for this font at a given scale. These metrics are
/// shared by all of the glyphs in the font. See `VMetrics` for more detail.
fn v_metrics(&self, scale: Vec2) -> f32 {
let vm = self.info.get_v_metrics();
let scale = scale.1;
(vm.ascent as f32) * scale
}
/// Returns the units per EM square of this font
pub fn units_per_em(&self) -> u16 {
self.info.units_per_em()
}
/// The number of glyphs present in this font. Glyph identifiers for this
/// font will always be in the range `0..self.glyph_count()`
pub fn glyph_count(&self) -> usize {
self.info.get_num_glyphs() as usize
}
/// Returns the corresponding glyph for a Unicode code point or a glyph id
/// for this font.
///
/// If `id` is a `GlyphId`, it must be valid for this font; otherwise, this
/// function panics. `GlyphId`s should always be produced by looking up some
/// other sort of designator (like a Unicode code point) in a font, and
/// should only be used to index the font they were produced for.
///
/// Note that code points without corresponding glyphs in this font map to
/// the ".notdef" glyph, glyph 0.
fn glyph<C: IntoGlyphId>(&self, id: C, v: Vec2) -> Glyph<'a> {
let gid = id.into_glyph_id(self);
assert!((gid.0 as usize) < self.glyph_count());
// font clone either a reference clone, or arc clone
Glyph::new(GlyphInner(self.clone(), gid.0), v)
}
/// Returns additional kerning to apply as well as that given by HMetrics
/// for a particular pair of glyphs.
fn pair_kerning<A, B>(&self, scale: (f32, f32), v: Vec2, first: A, second: B) -> f32
where
A: IntoGlyphId,
B: IntoGlyphId,
{
let (first, second) = (self.glyph(first, v), self.glyph(second, v));
let factor = self.info.scale_for_pixel_height(scale.1) * (scale.0 / scale.1);
let kern = self
.info
.get_glyph_kern_advance(first.id().0, second.id().0);
factor * kern as f32
}
/// Get an iterator over the glyphs in a string.
pub fn glyphs<T: ToString>(&'a self, text: T, scale: (f32, f32)) -> GlyphIterator<'a> {
let (scale_x, scale_y) = {
let scale_y = self.info.scale_for_pixel_height(scale.1);
let scale_x = scale_y * scale.0 / scale.1;
(scale_x, scale_y)
};
GlyphIterator {
font: &self,
api_scale: scale,
scale: Vec2(scale_x, scale_y),
string: text.to_string().nfc().collect::<Vec<char>>(),
cursor: 0,
last: None,
}
}
/// Render a string.
pub fn render<T: ToString>(&'a self, text: T, scale: (f32, f32),
point_x: f32, mut point_y: f32) -> Path2D
{
let mut path = PathBuilder::new().absolute();
point_y += self.v_metrics(Vec2(scale.0, scale.1));
let mut x = point_x;
let mut y = point_y;
let glyphs = self.glyphs(text, scale);
println!("printing {:?}", glyphs.string);
for g in glyphs {
println!("one");
// Check for newline
if g.2 {
x = point_x;
y += scale.1;
continue;
}
// Draw the glyph
return g.0.draw(x, y);
// Position next glyph
x += g.1;
}
path.build()
}
/// Get the proper spacing from the start of one character to the next.
fn kerning(&self, scale: (f32, f32), v: Vec2, first: &Glyph<'a>, second: &Glyph<'a>) -> f32 {
self.pair_kerning(scale, v, first.id(), second.id())
}
}
impl<'a> Glyph<'a> {
fn new(inner: GlyphInner<'a>, v: Vec2) -> Glyph<'a> {
Glyph { inner, v }
}
/// The font to which this glyph belongs.
fn font(&self) -> &Font<'a> {
&self.inner.0
}
/// The glyph identifier for this glyph.
fn id(&self) -> GlyphId {
GlyphId(self.inner.1)
}
/// Convert the glyph to an iterator over `PathOp`s
pub fn draw(&self, point_x: f32, mut point_y: f32) -> Path2D {
let mut path = PathBuilder::new().absolute();
point_y += self.font().v_metrics(self.v);
let shape = {
let (font, id) = (self.font(), self.id());
font.info.get_glyph_shape(id.0).unwrap_or_else(Vec::new)
};
for v in shape {
let x = v.x as f32 * self.v.0 + point_x;
let y = -v.y as f32 * self.v.1 + point_y;
use tt::VertexType;
match v.vertex_type() {
VertexType::LineTo => path = path.line_to(x, y),
VertexType::CurveTo => {
let cx = v.cx as f32 * self.v.0 + point_x;
let cy = -v.cy as f32 * self.v.1 + point_y;
path = path.quad_to(cx, cy, x, y);
}
VertexType::MoveTo => path = path.move_to(x, y),
}
}
path.build()
}
}
/// The type for errors returned by Fonterator.
#[derive(Debug)]
pub enum Error {
/// Font data presented to Fonterator is not in a format that the
/// library recognizes.
UnrecognizedFormat,
/// Font data presented to Fonterator was ill-formed (lacking necessary
/// tables, for example).
IllFormed,
/// The caller tried to access the `i`'th font from a `FontCollection`,
/// but the collection doesn't contain that many fonts.
CollectionIndexOutOfBounds,
/// The caller tried to convert a `FontCollection` into a font via
/// `into_font`, but the `FontCollection` contains more than one font.
CollectionContainsMultipleFonts,
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> std::result::Result<(), fmt::Error> {
f.write_str(std::error::Error::description(self))
}
}
impl std::error::Error for Error {
fn description(&self) -> &str {
use self::Error::*;
match *self {
UnrecognizedFormat => "Font data in unrecognized format",
IllFormed => "Font data is ill-formed",
CollectionIndexOutOfBounds => "Font collection has no font at the given index",
CollectionContainsMultipleFonts => {
"Attempted to convert collection into a font, \
but collection contais more than one font"
}
}
}
}
impl std::convert::From<Error> for std::io::Error {
fn from(error: Error) -> Self {
std::io::Error::new(std::io::ErrorKind::Other, error)
}
}