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use crate::parse::*;
use crate::table::loca::*;
use crate::FontResult;
use alloc::vec::*;
// Apple: https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6glyf.html
// Microsoft: https://docs.microsoft.com/en-us/typography/opentype/spec/glyf
#[allow(non_snake_case)]
pub mod SimpleFlags {
pub const NONE: u8 = 0x00;
pub const ON_CURVE: u8 = 0x01;
pub const X_SHORT: u8 = 0x02;
pub const Y_SHORT: u8 = 0x04;
pub const REPEAT: u8 = 0x08;
pub const X_DUAL: u8 = 0x10;
pub const Y_DUAL: u8 = 0x20;
pub const OVERLAP_SIMPLE: u8 = 0x40;
pub const X_SHORT_AND_DUAL: u8 = X_SHORT | X_DUAL;
pub const Y_SHORT_AND_DUAL: u8 = Y_SHORT | Y_DUAL;
}
#[allow(non_snake_case)]
pub mod CompoundFlags {
pub const NONE: u16 = 0x0000;
pub const ARGS_ARE_WORDS: u16 = 0x0001;
pub const ARGS_ARE_XY_VALUES: u16 = 0x0002;
pub const ROUND_XY_TO_GRID: u16 = 0x0004;
pub const WE_HAVE_A_SCALE: u16 = 0x0008;
pub const MORE_COMPONENTS: u16 = 0x0020;
pub const WE_HAVE_AN_X_AND_Y_SCALE: u16 = 0x0040;
pub const WE_HAVE_A_TWO_BY_TWO: u16 = 0x0080;
pub const WE_HAVE_INSTRUCTIONS: u16 = 0x0100;
pub const USE_MY_METRICS: u16 = 0x0200;
pub const OVERLAP_COMPOUND: u16 = 0x0400;
pub const SCALED_COMPONENT_OFFSET: u16 = 0x0800;
pub const UNSCALED_COMPONENT_OFFSET: u16 = 0x1000;
pub const ARGS_ARE_WORDS_AND_XY_VALUES: u16 = ARGS_ARE_WORDS | ARGS_ARE_XY_VALUES;
}
#[derive(Copy, Clone, Debug, PartialEq, Default)]
pub struct RawPoint {
/// Absolute X coordinate.
pub x: f32,
/// Absolute Y coordinate.
pub y: f32,
/// Flags associated with the point. The last bit (0x80) is used to mark if this is the start
/// of a new contour. The bit is otherwise reserved in spec.
pub flags: u8,
/// Marks if this is the last point in the contour.
pub end_point: bool,
/// Marks if this is the first point in the contour.
pub start_point: bool,
}
impl RawPoint {
#[inline]
pub fn on_curve(&self) -> bool {
flag_u8(self.flags, SimpleFlags::ON_CURVE)
}
pub fn transform(&mut self, a: f32, b: f32, c: f32, d: f32, cx: f32, cy: f32) {
let px = self.x;
let py = self.y;
self.x = a * px + c * py + cx;
self.y = b * px + d * py + cy;
}
}
#[derive(Debug, Clone)]
pub struct Glyph {
/// The number of contours in the glyph.
pub num_contours: i16,
/// The index of the metrics location for this glyph.
pub metrics: usize,
/// The first point is always marked as the start point, and the last point is always marked as
/// the end point.
pub points: Vec<RawPoint>,
}
impl Default for Glyph {
fn default() -> Glyph {
Glyph {
num_contours: 0,
metrics: 0,
points: Vec::with_capacity(0),
}
}
}
pub struct TableGlyf {
/// Indexed by glyph id.
pub glyphs: Vec<Glyph>,
}
// Truetype is a marvelous format.
fn parse_glyph(glyf: &[u8], locations: &[GlyphLocation], index: usize) -> FontResult<Glyph> {
let loc = &locations[index];
let mut glyph = Glyph::default();
glyph.metrics = index;
// Empty glyph, exit early.
if loc.length == 0 {
return Ok(glyph);
}
let mut stream = Stream::new(glyf);
stream.seek(loc.offset);
glyph.num_contours = stream.read_i16();
// The boundary box is skipped because the bounds are computed after parsing. Never trust the
// font.
stream.skip(8); // xmin: i16, ymin: i16, xmax: i16, ymax: i16
// No contours, exit early.
if glyph.num_contours == 0 {
// This is an empty glyph and shouldn’t have any glyph data, but if it does we will simply
// ignore it.
} else if glyph.num_contours > 0 {
// Simple glyphs.
// Read the contours. A contour is basically just a continous line. The letter 'O'
// for example has 2 contours. The end_points_of_contours array basically has the
// number of points to read for each contour.
let mut end_points_of_contours = Vec::with_capacity(glyph.num_contours as usize);
for _ in 0..glyph.num_contours as usize {
let end_points_of_contour = stream.read_u16();
end_points_of_contours.push(end_points_of_contour);
}
// Since end_points_of_contours indexes by the point index, the last contour has
// the number of points in the glyph minus 1.
let num_points = end_points_of_contours[glyph.num_contours as usize - 1] as usize + 1;
// Skip instructions, we don't need a manual to go where we're going.
// (Really, what is this for in 2019?)
let instruction_length = stream.read_u16();
stream.skip(instruction_length as usize);
// Read flags. Flags can repeat, but they're not stored as literal repeats, they
// instead have a byte after them for their repeat count and you just need to
// re-use the prior flag that many times.
glyph.points = Vec::with_capacity(num_points);
while glyph.points.len() < num_points {
let flags = stream.read_u8();
let point = RawPoint {
x: 0.0,
y: 0.0,
flags,
// These are set later
start_point: false,
end_point: false,
};
glyph.points.push(point);
if flag_u8(flags, SimpleFlags::REPEAT) {
let count = stream.read_u8();
for _ in 0..count {
glyph.points.push(point);
}
}
}
// We're now at the x-coordinates. These are not absolute positions, but deltas
// from the last position. This will parse them into absolute positions.
let mut last_x = 0i16;
for point in &mut glyph.points {
match point.flags & (SimpleFlags::X_SHORT | SimpleFlags::X_DUAL) {
SimpleFlags::X_SHORT_AND_DUAL => {
last_x += stream.read_u8() as i16;
}
SimpleFlags::X_SHORT => {
last_x -= stream.read_u8() as i16;
}
SimpleFlags::X_DUAL => {
// Reuse last_x.
}
_ => {
last_x += stream.read_i16();
}
}
point.x = last_x as f32;
}
// Finally, the y-coordinates. Parsed the same as x basically; just use the
// y-coord version of the flags instead.
let mut last_y = 0i16;
for point in &mut glyph.points {
match point.flags & SimpleFlags::Y_SHORT_AND_DUAL {
SimpleFlags::Y_SHORT_AND_DUAL => {
last_y += stream.read_u8() as i16;
}
SimpleFlags::Y_SHORT => {
last_y -= stream.read_u8() as i16;
}
SimpleFlags::Y_DUAL => {
// Reuse last_y.
}
_ => {
last_y += stream.read_i16();
}
}
point.y = last_y as f32;
}
// Mark the start and end points in each contour. This makes figuring out contours easier.
for end_point in end_points_of_contours {
let end_point = end_point as usize;
glyph.points[end_point].end_point = true;
glyph.points[(end_point + 1) % num_points].start_point = true;
}
} else {
// Compound glyphs.
let mut flags = CompoundFlags::MORE_COMPONENTS;
while flag_u16(flags, CompoundFlags::MORE_COMPONENTS) {
flags = stream.read_u16();
let compound_glyph_index = stream.read_u16();
if flag_u16(flags, CompoundFlags::USE_MY_METRICS) {
glyph.metrics = compound_glyph_index as usize;
}
let cx;
let cy;
match flags & CompoundFlags::ARGS_ARE_WORDS_AND_XY_VALUES {
CompoundFlags::ARGS_ARE_WORDS_AND_XY_VALUES => {
cx = stream.read_i16() as i32;
cy = stream.read_i16() as i32;
}
CompoundFlags::ARGS_ARE_WORDS => {
return Err("Font.glyf: Component matched point numbers are unsupported");
// TODO: Matched point numbers. Rusttype doesn't support them either.
// cx = read_u16(&glyf[offset..]) as i32;
// cy = read_u16(&glyf[offset + 2..]) as i32;
// offset += 4;
}
CompoundFlags::ARGS_ARE_XY_VALUES => {
cx = stream.read_i8() as i32;
cy = stream.read_i8() as i32;
}
_ => {
return Err("Font.glyf: Component matched point numbers are unsupported");
// TODO: Matched point numbers. Rusttype doesn't support them either.
// cx = read_u8(&glyf[offset..]) as i32;
// cy = read_u8(&glyf[offset + 1..]) as i32;
// offset += 2;
}
}
let mut a = 1.0;
let mut b = 0.0;
let mut c = 0.0;
let mut d = 1.0;
if flag_u16(flags, CompoundFlags::WE_HAVE_A_SCALE) {
a = stream.read_f2dot14();
d = a;
} else if flag_u16(flags, CompoundFlags::WE_HAVE_AN_X_AND_Y_SCALE) {
a = stream.read_f2dot14();
d = stream.read_f2dot14();
} else if flag_u16(flags, CompoundFlags::WE_HAVE_A_TWO_BY_TWO) {
a = stream.read_f2dot14();
b = stream.read_f2dot14();
c = stream.read_f2dot14();
d = stream.read_f2dot14();
} else {
// Do nothing, use the values we have for a, b, c, d.
}
// This is the only valid configuration to use scale offsets.
if flag_u16(flags, CompoundFlags::SCALED_COMPONENT_OFFSET)
&& !flag_u16(flags, CompoundFlags::UNSCALED_COMPONENT_OFFSET)
{
return Err("Font.glyf: Scaled component offset is unsupported");
// TODO: Scaled offset. Rusttype doesn't handle this, neither does Chrome.
}
let mut compound_glyph_points =
parse_glyph(glyf, locations, compound_glyph_index as usize)?.points;
for point in &mut compound_glyph_points {
point.transform(a, b, c, d, cx as f32, cy as f32);
}
glyph.points.append(&mut compound_glyph_points);
}
}
Ok(glyph)
}
impl TableGlyf {
pub fn new(glyf: &[u8], locations: &[GlyphLocation]) -> FontResult<TableGlyf> {
let mut glyphs = Vec::with_capacity(locations.len());
for i in 0..locations.len() {
let glyph = parse_glyph(glyf, locations, i)?;
glyphs.push(glyph);
}
Ok(TableGlyf {
glyphs,
})
}
}