canary-rs/src/text/glyph.rs

// Copyright (c) 2022 Marceline Cramer
// SPDX-License-Identifier: LGPL-3.0-or-later

use super::{AllsortsFont, Rect, Vec2};

use allsorts::binary::read::ReadScope;
use allsorts::cff::CFF;
use allsorts::font::GlyphTableFlags;
use allsorts::font_data::DynamicFontTableProvider;
use allsorts::outline::OutlineBuilder;
use allsorts::pathfinder_geometry::{line_segment::LineSegment2F, vector::Vector2F};
use allsorts::tables::{glyf::GlyfTable, loca::LocaTable, FontTableProvider, SfntVersion};
use allsorts::tag;
use lyon::path::Path;
use parking_lot::RwLock;

pub struct GlyphCache {
    pub units_per_em: f32,
    pub glyphs: RwLock<Vec<CachedGlyph>>,
}

impl GlyphCache {
    pub fn new(font: &AllsortsFont<DynamicFontTableProvider>) -> Self {
        let glyph_num = font.num_glyphs();
        let mut glyphs = Vec::with_capacity(glyph_num as usize);
        let units_per_em = font.head_table().unwrap().unwrap().units_per_em as f32;

        if font.glyph_table_flags.contains(GlyphTableFlags::CFF)
            && font.font_table_provider.sfnt_version() == tag::OTTO
        {
            let cff_data = font.font_table_provider.read_table_data(tag::CFF).unwrap();
            let mut cff = ReadScope::new(&cff_data).read::<CFF<'_>>().unwrap();
            for index in 0..glyph_num {
                glyphs.push(CachedGlyph::new(units_per_em, &mut cff, index));
            }
        } else if font.glyph_table_flags.contains(GlyphTableFlags::GLYF) {
            let loca_data = font.font_table_provider.read_table_data(tag::LOCA).unwrap();
            let loca = ReadScope::new(&loca_data)
                .read_dep::<LocaTable<'_>>((
                    usize::from(font.maxp_table.num_glyphs),
                    font.head_table().unwrap().unwrap().index_to_loc_format,
                ))
                .unwrap();
            let glyf_data = font.font_table_provider.read_table_data(tag::GLYF).unwrap();
            let mut glyf = ReadScope::new(&glyf_data)
                .read_dep::<GlyfTable<'_>>(&loca)
                .unwrap();

            for index in 0..glyph_num {
                glyphs.push(CachedGlyph::new(units_per_em, &mut glyf, index));
            }
        } else {
            panic!("no glyf or CFF table");
        }

        Self {
            units_per_em,
            glyphs: RwLock::new(glyphs),
        }
    }
}

pub struct CachedGlyph {
    pub bounding_box: Rect,
    path: Path,
    mesh: Option<GlyphMesh>,
}

impl CachedGlyph {
    pub fn new(units_per_em: f32, builder: &mut impl OutlineBuilder, index: u16) -> Self {
        let mut sink = OutlineSink::new(units_per_em);
        builder.visit(index, &mut sink).unwrap();
        let bounding_box = sink.bounding_box;
        let path = sink.builder.build();

        Self {
            bounding_box,
            path,
            mesh: None,
        }
    }

    pub fn get_mesh(&mut self) -> &GlyphMesh {
        self.mesh.get_or_insert_with(|| {
            use lyon::tessellation::*;

            let mut geometry: VertexBuffers<Vec2, u32> = VertexBuffers::new();
            let fill_options = FillOptions::default().with_tolerance(0.0005);
            let mut tessellator = FillTessellator::new();
            tessellator
                .tessellate_path(
                    &self.path.clone(),
                    &fill_options,
                    &mut BuffersBuilder::new(&mut geometry, |vertex: FillVertex| {
                        let position = vertex.position();
                        Vec2::new(position.x, position.y)
                    }),
                )
                .unwrap();

            GlyphMesh {
                vertices: geometry.vertices,
                indices: geometry.indices,
            }
        })
    }
}

pub struct OutlineSink {
    units_per_em: f32,
    bounding_box: Rect,
    builder: lyon::path::path::Builder,
}

impl OutlineSink {
    pub fn new(units_per_em: f32) -> Self {
        Self {
            units_per_em,
            bounding_box: Rect::NEG_INFINITY,
            builder: lyon::path::Path::builder(),
        }
    }

    fn pf_line_to_lyon(
        &mut self,
        line: &LineSegment2F,
    ) -> (lyon::geom::Point<f32>, lyon::geom::Point<f32>) {
        (
            self.pf_vector_to_lyon(&line.from()),
            self.pf_vector_to_lyon(&line.to()),
        )
    }

    fn pf_vector_to_lyon(&mut self, v: &Vector2F) -> lyon::geom::Point<f32> {
        let point = lyon::geom::Point::<f32>::new(v.x(), -v.y()) / self.units_per_em;
        let glam_point = Vec2::new(point.x, point.y);
        self.bounding_box = self.bounding_box.union_point(glam_point);
        point
    }
}

impl allsorts::outline::OutlineSink for OutlineSink {
    fn move_to(&mut self, to: Vector2F) {
        let to = self.pf_vector_to_lyon(&to);
        self.builder.begin(to);
    }

    fn line_to(&mut self, to: Vector2F) {
        let to = self.pf_vector_to_lyon(&to);
        self.builder.line_to(to);
    }

    fn quadratic_curve_to(&mut self, control: Vector2F, to: Vector2F) {
        let control = self.pf_vector_to_lyon(&control);
        let to = self.pf_vector_to_lyon(&to);
        self.builder.quadratic_bezier_to(control, to);
    }

    fn cubic_curve_to(&mut self, control: LineSegment2F, to: Vector2F) {
        let (ctrl1, ctrl2) = self.pf_line_to_lyon(&control);
        let to = self.pf_vector_to_lyon(&to);
        self.builder.cubic_bezier_to(ctrl1, ctrl2, to);
    }

    fn close(&mut self) {
        self.builder.close();
    }
}

pub struct GlyphMesh {
    pub vertices: Vec<Vec2>,
    pub indices: Vec<u32>,
}