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Merge pull request #311 from Monadic-Cat/feature-ab_glyph
Add `ab_glyph` font backend
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Original file line number | Diff line number | Diff line change |
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use super::{FontData, FontFamily, FontStyle, LayoutBox}; | ||
use ab_glyph::{Font, FontRef, ScaleFont}; | ||
use core::fmt::{self, Display}; | ||
use once_cell::sync::Lazy; | ||
use std::collections::HashMap; | ||
use std::error::Error; | ||
use std::sync::RwLock; | ||
|
||
struct FontMap { | ||
map: HashMap<String, FontRef<'static>>, | ||
} | ||
impl FontMap { | ||
fn new() -> Self { | ||
Self { | ||
map: HashMap::with_capacity(4), | ||
} | ||
} | ||
fn insert(&mut self, style: FontStyle, font: FontRef<'static>) -> Option<FontRef<'static>> { | ||
self.map.insert(style.as_str().to_string(), font) | ||
} | ||
// fn get(&self, style: FontStyle) -> Option<&FontRef<'static>> { | ||
// self.map.get(style.as_str()) | ||
// } | ||
fn get_fallback(&self, style: FontStyle) -> Option<&FontRef<'static>> { | ||
self.map | ||
.get(style.as_str()) | ||
.or_else(|| self.map.get(FontStyle::Normal.as_str())) | ||
} | ||
} | ||
|
||
static FONTS: Lazy<RwLock<HashMap<String, FontMap>>> = Lazy::new(|| RwLock::new(HashMap::new())); | ||
pub struct InvalidFont { | ||
_priv: (), | ||
} | ||
|
||
// Note for future contributors: There is nothing fundamental about the static reference requirement here. | ||
// It would be reasonably easy to add a function which accepts an owned buffer, | ||
// or even a reference counted buffer, instead. | ||
/// Register a font in the fonts table. | ||
/// | ||
/// The `name` parameter gives the name this font shall be referred to | ||
/// in the other APIs, like `"sans-serif"`. | ||
/// | ||
/// The `bytes` parameter should be the complete contents | ||
/// of an OpenType font file, like: | ||
/// ```ignore | ||
/// include_bytes!("FiraGO-Regular.otf") | ||
/// ``` | ||
pub fn register_font( | ||
name: &str, | ||
style: FontStyle, | ||
bytes: &'static [u8], | ||
) -> Result<(), InvalidFont> { | ||
let font = FontRef::try_from_slice(bytes).map_err(|_| InvalidFont { _priv: () })?; | ||
let mut lock = FONTS.write().unwrap(); | ||
lock.entry(name.to_string()) | ||
.or_insert_with(FontMap::new) | ||
.insert(style, font); | ||
Ok(()) | ||
} | ||
|
||
#[derive(Clone)] | ||
pub struct FontDataInternal { | ||
font_ref: FontRef<'static>, | ||
} | ||
|
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#[derive(Debug, Clone)] | ||
pub enum FontError { | ||
/// No idea what the problem is | ||
Unknown, | ||
/// No font data available for the requested family and style. | ||
FontUnavailable, | ||
} | ||
impl Display for FontError { | ||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
// Since it makes literally no difference to how we'd format | ||
// this, just delegate to the derived Debug formatter. | ||
write!(f, "{:?}", self) | ||
} | ||
} | ||
impl Error for FontError {} | ||
|
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impl FontData for FontDataInternal { | ||
// TODO: can we rename this to `Error`? | ||
type ErrorType = FontError; | ||
fn new(family: FontFamily<'_>, style: FontStyle) -> Result<Self, Self::ErrorType> { | ||
Ok(Self { | ||
font_ref: FONTS | ||
.read() | ||
.unwrap() | ||
.get(family.as_str()) | ||
.and_then(|fam| fam.get_fallback(style)) | ||
.ok_or(FontError::FontUnavailable)? | ||
.clone(), | ||
}) | ||
} | ||
// TODO: ngl, it makes no sense that this uses the same error type as `new` | ||
fn estimate_layout(&self, size: f64, text: &str) -> Result<LayoutBox, Self::ErrorType> { | ||
let pixel_per_em = size / 1.24; | ||
// let units_per_em = self.font_ref.units_per_em().unwrap(); | ||
let font = self.font_ref.as_scaled(size as f32); | ||
|
||
let mut x_pixels = 0f32; | ||
|
||
let mut prev = None; | ||
for c in text.chars() { | ||
let glyph_id = font.glyph_id(c); | ||
let size = font.h_advance(glyph_id); | ||
x_pixels += size; | ||
if let Some(pc) = prev { | ||
x_pixels += font.kern(pc, glyph_id); | ||
} | ||
prev = Some(glyph_id); | ||
} | ||
|
||
Ok(((0, 0), (x_pixels as i32, pixel_per_em as i32))) | ||
} | ||
fn draw<E, DrawFunc: FnMut(i32, i32, f32) -> Result<(), E>>( | ||
&self, | ||
pos: (i32, i32), | ||
size: f64, | ||
text: &str, | ||
mut draw: DrawFunc, | ||
) -> Result<Result<(), E>, Self::ErrorType> { | ||
let font = self.font_ref.as_scaled(size as f32); | ||
let mut draw = |x: i32, y: i32, c| { | ||
let (base_x, base_y) = pos; | ||
draw(base_x + x, base_y + y, c) | ||
}; | ||
let mut x_shift = 0f32; | ||
let mut prev = None; | ||
for c in text.chars() { | ||
if let Some(pc) = prev { | ||
x_shift += font.kern(font.glyph_id(pc), font.glyph_id(c)); | ||
} | ||
prev = Some(c); | ||
let glyph = font.scaled_glyph(c); | ||
if let Some(q) = font.outline_glyph(glyph) { | ||
let rect = q.px_bounds(); | ||
let y_shift = ((size as f32) / 2.0 + rect.min.y) as i32; | ||
let x_shift = x_shift as i32; | ||
let mut buf = vec![]; | ||
q.draw(|x, y, c| buf.push((x, y, c))); | ||
for (x, y, c) in buf { | ||
draw(x as i32 + x_shift, y as i32 + y_shift, c).map_err(|_e| { | ||
// Note: If ever `plotters` adds a tracing or logging crate, | ||
// this would be a good place to use it. | ||
FontError::Unknown | ||
})?; | ||
} | ||
} | ||
x_shift += font.h_advance(font.glyph_id(c)); | ||
} | ||
Ok(Ok(())) | ||
} | ||
} |
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