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[skrifa] autohint bug fixes to match FT #1145

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Sep 10, 2024
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17 changes: 17 additions & 0 deletions fauntlet/src/compare_glyphs.rs
Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
use crate::Hinting;

use super::{FreeTypeInstance, InstanceOptions, RegularizingPen, SkrifaInstance};
use skrifa::{outline::pen::PathElement, GlyphId};
use std::{io::Write, path::Path};
Expand All @@ -13,6 +15,20 @@ pub fn compare_glyphs(
// Don't run on bitmap fonts (yet)
return true;
}
if let Some(Hinting::Auto(_)) = options.hinting {
// This font is a pathological case for autohinting due to the
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Perhaps add an issue reference?

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Will do. I want to get some actual metrics from this font so we can potentially add limits to prevent this performance cliff. Beyond a certain level of geometric complexity, hinting is likely to produce useless results anyway.

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Yes, similarly we might want to disable it for COLRv1 fonts, but I can do that on the client side.

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Sgtm.

Filed #1147 and added a link in the comment

// extreme number of generated segments and edges. To be
// precise, it takes longer to test this single font than the
// entire remainder of the Google Fonts corpus so we skip it
// here.
if ft_instance
.family_name()
.unwrap_or_default()
.contains("Handjet")
{
return true;
}
}
let glyph_count = skrifa_instance.glyph_count();
let is_scaled = options.ppem != 0;

Expand Down Expand Up @@ -86,6 +102,7 @@ pub fn compare_glyphs(
if exit_on_fail {
std::process::exit(1);
}
break;
}
}
ok
Expand Down
24 changes: 7 additions & 17 deletions fauntlet/src/font/freetype.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,26 +3,12 @@ use freetype::{
ffi::{FT_Long, FT_Vector},
Face, Library,
};
use skrifa::{
outline::{HintingMode, LcdLayout, OutlinePen},
GlyphId,
};
use skrifa::{outline::OutlinePen, GlyphId};

use std::ffi::{c_int, c_void};

use super::{InstanceOptions, SharedFontData};

fn load_flags_from_hinting(mode: HintingMode) -> LoadFlag {
match mode {
HintingMode::Strong => LoadFlag::TARGET_MONO,
HintingMode::Smooth { lcd_subpixel, .. } => match lcd_subpixel {
Some(LcdLayout::Horizontal) => LoadFlag::TARGET_LCD,
Some(LcdLayout::Vertical) => LoadFlag::TARGET_LCD_V,
None => LoadFlag::TARGET_NORMAL,
},
}
}

pub struct FreeTypeInstance {
face: Face<SharedFontData>,
load_flags: LoadFlag,
Expand All @@ -37,10 +23,10 @@ impl FreeTypeInstance {
let mut face = library
.new_memory_face2(data.clone(), options.index as isize)
.ok()?;
let mut load_flags = LoadFlag::NO_AUTOHINT | LoadFlag::NO_BITMAP;
let mut load_flags = LoadFlag::NO_BITMAP;
match options.hinting {
None => load_flags |= LoadFlag::NO_HINTING,
Some(hinting) => load_flags |= load_flags_from_hinting(hinting),
Some(hinting) => load_flags |= hinting.freetype_load_flags(),
};
if options.ppem != 0 {
face.set_pixel_sizes(options.ppem, options.ppem).ok()?;
Expand Down Expand Up @@ -76,6 +62,10 @@ impl FreeTypeInstance {
Some(Self { face, load_flags })
}

pub fn family_name(&self) -> Option<String> {
self.face.family_name()
}

pub fn is_scalable(&self) -> bool {
self.face.is_scalable()
}
Expand Down
73 changes: 64 additions & 9 deletions fauntlet/src/font/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,9 @@ use std::{
sync::Arc,
};

use ::freetype::Library;
use ::freetype::{face::LoadFlag, Library};
use ::skrifa::{
outline::HintingMode,
outline::{HintingOptions, SmoothMode, Target},
raw::{types::F2Dot14, FileRef, FontRef, TableProvider},
};

Expand All @@ -16,21 +16,76 @@ mod skrifa;
pub use freetype::FreeTypeInstance;
pub use skrifa::SkrifaInstance;

#[derive(Copy, Clone, PartialEq, Eq, Default, Debug)]
pub enum HintingTarget {
#[default]
Normal,
Light,
Lcd,
VerticalLcd,
Mono,
}

impl HintingTarget {
pub fn to_skrifa_target(self) -> Target {
match self {
Self::Normal => SmoothMode::Normal.into(),
Self::Light => SmoothMode::Light.into(),
Self::Lcd => SmoothMode::Lcd.into(),
Self::VerticalLcd => SmoothMode::VerticalLcd.into(),
Self::Mono => Target::Mono,
}
}

pub fn to_freetype_load_flags(self) -> LoadFlag {
match self {
Self::Normal => LoadFlag::TARGET_NORMAL,
Self::Light => LoadFlag::TARGET_LIGHT,
Self::Lcd => LoadFlag::TARGET_LCD,
Self::VerticalLcd => LoadFlag::TARGET_LCD_V,
Self::Mono => LoadFlag::TARGET_MONO,
}
}
}

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Hinting {
Interpreter(HintingTarget),
Auto(HintingTarget),
}

impl Hinting {
pub fn skrifa_options(self) -> HintingOptions {
match self {
Self::Interpreter(target) => HintingOptions {
engine: ::skrifa::outline::Engine::Interpreter,
target: target.to_skrifa_target(),
},
Self::Auto(target) => HintingOptions {
engine: ::skrifa::outline::Engine::Auto(None),
target: target.to_skrifa_target(),
},
}
}

pub fn freetype_load_flags(self) -> LoadFlag {
match self {
Self::Interpreter(target) => LoadFlag::NO_AUTOHINT | target.to_freetype_load_flags(),
Self::Auto(target) => LoadFlag::FORCE_AUTOHINT | target.to_freetype_load_flags(),
}
}
}

#[derive(Copy, Clone, Debug)]
pub struct InstanceOptions<'a> {
pub index: usize,
pub ppem: u32,
pub coords: &'a [F2Dot14],
pub hinting: Option<HintingMode>,
pub hinting: Option<Hinting>,
}

impl<'a> InstanceOptions<'a> {
pub fn new(
index: usize,
ppem: u32,
coords: &'a [F2Dot14],
hinting: Option<HintingMode>,
) -> Self {
pub fn new(index: usize, ppem: u32, coords: &'a [F2Dot14], hinting: Option<Hinting>) -> Self {
Self {
index,
ppem,
Expand Down
9 changes: 7 additions & 2 deletions fauntlet/src/font/skrifa.rs
Original file line number Diff line number Diff line change
Expand Up @@ -27,8 +27,13 @@ impl<'a> SkrifaInstance<'a> {
let outlines = font.outline_glyphs();
let hinter = if options.ppem != 0 && options.hinting.is_some() {
Some(
HintingInstance::new(&outlines, size, options.coords, options.hinting.unwrap())
.ok()?,
HintingInstance::new(
&outlines,
size,
options.coords,
options.hinting.unwrap().skrifa_options(),
)
.ok()?,
)
} else {
None
Expand Down
4 changes: 3 additions & 1 deletion fauntlet/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -3,5 +3,7 @@ mod font;
mod pen;

pub use compare_glyphs::compare_glyphs;
pub use font::{Font, FreeTypeInstance, InstanceOptions, SharedFontData, SkrifaInstance};
pub use font::{
Font, FreeTypeInstance, Hinting, HintingTarget, InstanceOptions, SharedFontData, SkrifaInstance,
};
pub use pen::RegularizingPen;
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