typst/src/library/text.rs
2021-11-20 13:26:28 +01:00

694 lines
22 KiB
Rust

use std::borrow::Cow;
use std::convert::TryInto;
use std::ops::Range;
use rustybuzz::{Feature, UnicodeBuffer};
use ttf_parser::Tag;
use super::prelude::*;
use crate::font::{
Face, FaceId, FontStore, FontStretch, FontStyle, FontVariant, FontWeight,
VerticalFontMetric,
};
use crate::geom::{Dir, Em, Length, Point, Size};
use crate::style::{
FontFamily, FontFeatures, NumberPosition, NumberType, NumberWidth, Style,
StylisticSet, TextStyle,
};
use crate::util::{EcoString, SliceExt};
/// `font`: Configure the font.
pub fn font(ctx: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
castable! {
Vec<FontFamily>,
Expected: "string, generic family or array thereof",
Value::Str(string) => vec![FontFamily::Named(string.to_lowercase())],
Value::Array(values) => {
values.into_iter().filter_map(|v| v.cast().ok()).collect()
},
@family: FontFamily => vec![family.clone()],
}
castable! {
Vec<EcoString>,
Expected: "string or array of strings",
Value::Str(string) => vec![string.to_lowercase()],
Value::Array(values) => values
.into_iter()
.filter_map(|v| v.cast().ok())
.map(|string: EcoString| string.to_lowercase())
.collect(),
}
castable! {
FontStyle,
Expected: "string",
Value::Str(string) => match string.as_str() {
"normal" => Self::Normal,
"italic" => Self::Italic,
"oblique" => Self::Oblique,
_ => Err(r#"expected "normal", "italic" or "oblique""#)?,
},
}
castable! {
FontWeight,
Expected: "integer or string",
Value::Int(v) => v.try_into().map_or(Self::BLACK, Self::from_number),
Value::Str(string) => match string.as_str() {
"thin" => Self::THIN,
"extralight" => Self::EXTRALIGHT,
"light" => Self::LIGHT,
"regular" => Self::REGULAR,
"medium" => Self::MEDIUM,
"semibold" => Self::SEMIBOLD,
"bold" => Self::BOLD,
"extrabold" => Self::EXTRABOLD,
"black" => Self::BLACK,
_ => Err("unknown font weight")?,
},
}
castable! {
FontStretch,
Expected: "relative",
Value::Relative(v) => Self::from_ratio(v.get() as f32),
}
castable! {
VerticalFontMetric,
Expected: "linear or string",
Value::Length(v) => Self::Linear(v.into()),
Value::Relative(v) => Self::Linear(v.into()),
Value::Linear(v) => Self::Linear(v),
Value::Str(string) => match string.as_str() {
"ascender" => Self::Ascender,
"cap-height" => Self::CapHeight,
"x-height" => Self::XHeight,
"baseline" => Self::Baseline,
"descender" => Self::Descender,
_ => Err("unknown font metric")?,
},
}
castable! {
StylisticSet,
Expected: "none or integer",
Value::None => Self(None),
Value::Int(v) => match v {
1 ..= 20 => Self(Some(v as u8)),
_ => Err("must be between 1 and 20")?,
},
}
castable! {
NumberType,
Expected: "auto or string",
Value::Auto => Self::Auto,
Value::Str(string) => match string.as_str() {
"lining" => Self::Lining,
"old-style" => Self::OldStyle,
_ => Err(r#"expected "lining" or "old-style""#)?,
},
}
castable! {
NumberWidth,
Expected: "auto or string",
Value::Auto => Self::Auto,
Value::Str(string) => match string.as_str() {
"proportional" => Self::Proportional,
"tabular" => Self::Tabular,
_ => Err(r#"expected "proportional" or "tabular""#)?,
},
}
castable! {
NumberPosition,
Expected: "string",
Value::Str(string) => match string.as_str() {
"normal" => Self::Normal,
"subscript" => Self::Subscript,
"superscript" => Self::Superscript,
_ => Err(r#"expected "normal", "subscript" or "superscript""#)?,
},
}
castable! {
Vec<(Tag, u32)>,
Expected: "array of strings or dictionary mapping tags to integers",
Value::Array(values) => values
.into_iter()
.filter_map(|v| v.cast().ok())
.map(|string: EcoString| (Tag::from_bytes_lossy(string.as_bytes()), 1))
.collect(),
Value::Dict(values) => values
.into_iter()
.filter_map(|(k, v)| {
let tag = Tag::from_bytes_lossy(k.as_bytes());
let num = v.cast::<i64>().ok()?.try_into().ok()?;
Some((tag, num))
})
.collect(),
}
let list = args.named("family")?.or_else(|| {
let families: Vec<_> = args.all().collect();
(!families.is_empty()).then(|| families)
});
let serif = args.named("serif")?;
let sans_serif = args.named("sans-serif")?;
let monospace = args.named("monospace")?;
let fallback = args.named("fallback")?;
let style = args.named("style")?;
let weight = args.named("weight")?;
let tracking = args.named("tracking")?;
let stretch = args.named("stretch")?;
let size = args.named::<Linear>("size")?.or_else(|| args.find());
let top_edge = args.named("top-edge")?;
let bottom_edge = args.named("bottom-edge")?;
let fill = args.named("fill")?.or_else(|| args.find());
let kerning = args.named("kerning")?;
let smallcaps = args.named("smallcaps")?;
let alternates = args.named("alternates")?;
let stylistic_set = args.named("stylistic-set")?;
let ligatures = args.named("ligatures")?;
let discretionary_ligatures = args.named("discretionary-ligatures")?;
let historical_ligatures = args.named("historical-ligatures")?;
let number_type = args.named("number-type")?;
let number_width = args.named("number-width")?;
let number_position = args.named("number-position")?;
let slashed_zero = args.named("slashed-zero")?;
let fractions = args.named("fractions")?;
let features = args.named("features")?;
let body = args.find::<Template>();
macro_rules! set {
($target:expr => $source:expr) => {
if let Some(v) = $source {
$target = v;
}
};
}
let f = move |style_: &mut Style| {
let text = style_.text_mut();
if let Some(size) = size {
text.size = size.resolve(text.size);
}
if let Some(fill) = fill {
text.fill = Paint::Color(fill);
}
if let Some(tracking) = tracking {
text.tracking = Em::new(tracking);
}
set!(text.variant.style => style);
set!(text.variant.weight => weight);
set!(text.variant.stretch => stretch);
set!(text.top_edge => top_edge);
set!(text.bottom_edge => bottom_edge);
set!(text.fallback => fallback);
set!(text.families_mut().list => list.clone());
set!(text.families_mut().serif => serif.clone());
set!(text.families_mut().sans_serif => sans_serif.clone());
set!(text.families_mut().monospace => monospace.clone());
set!(text.features_mut().kerning => kerning);
set!(text.features_mut().smallcaps => smallcaps);
set!(text.features_mut().alternates => alternates);
set!(text.features_mut().stylistic_set => stylistic_set);
set!(text.features_mut().ligatures.standard => ligatures);
set!(text.features_mut().ligatures.discretionary => discretionary_ligatures);
set!(text.features_mut().ligatures.historical => historical_ligatures);
set!(text.features_mut().numbers.type_ => number_type);
set!(text.features_mut().numbers.width => number_width);
set!(text.features_mut().numbers.position => number_position);
set!(text.features_mut().numbers.slashed_zero => slashed_zero);
set!(text.features_mut().numbers.fractions => fractions);
set!(text.features_mut().raw => features.clone());
};
Ok(if let Some(body) = body {
Value::Template(body.modified(f))
} else {
ctx.template.modify(f);
Value::None
})
}
/// Shape text into [`ShapedText`].
pub fn shape<'a>(
ctx: &mut LayoutContext,
text: &'a str,
style: &'a TextStyle,
dir: Dir,
) -> ShapedText<'a> {
let mut glyphs = vec![];
if !text.is_empty() {
shape_segment(
ctx.fonts,
&mut glyphs,
0,
text,
style.variant(),
style.families(),
None,
dir,
&tags(&style.features),
);
}
track(&mut glyphs, style.tracking);
let (size, baseline) = measure(ctx, &glyphs, style);
ShapedText {
text,
dir,
style,
size,
baseline,
glyphs: Cow::Owned(glyphs),
}
}
/// The result of shaping text.
///
/// This type contains owned or borrowed shaped text runs, which can be
/// measured, used to reshape substrings more quickly and converted into a
/// frame.
#[derive(Debug, Clone)]
pub struct ShapedText<'a> {
/// The text that was shaped.
pub text: &'a str,
/// The text direction.
pub dir: Dir,
/// The properties used for font selection.
pub style: &'a TextStyle,
/// The font size.
pub size: Size,
/// The baseline from the top of the frame.
pub baseline: Length,
/// The shaped glyphs.
pub glyphs: Cow<'a, [ShapedGlyph]>,
}
/// A single glyph resulting from shaping.
#[derive(Debug, Copy, Clone)]
pub struct ShapedGlyph {
/// The font face the glyph is contained in.
pub face_id: FaceId,
/// The glyph's index in the face.
pub glyph_id: u16,
/// The advance width of the glyph.
pub x_advance: Em,
/// The horizontal offset of the glyph.
pub x_offset: Em,
/// The start index of the glyph in the source text.
pub text_index: usize,
/// Whether splitting the shaping result before this glyph would yield the
/// same results as shaping the parts to both sides of `text_index`
/// separately.
pub safe_to_break: bool,
}
impl<'a> ShapedText<'a> {
/// Build the shaped text's frame.
pub fn build(&self) -> Frame {
let mut frame = Frame::new(self.size, self.baseline);
let mut offset = Length::zero();
for (face_id, group) in self.glyphs.as_ref().group_by_key(|g| g.face_id) {
let pos = Point::new(offset, self.baseline);
let mut text = Text {
face_id,
size: self.style.size,
width: Length::zero(),
fill: self.style.fill,
glyphs: vec![],
};
for glyph in group {
text.glyphs.push(Glyph {
id: glyph.glyph_id,
x_advance: glyph.x_advance,
x_offset: glyph.x_offset,
});
text.width += glyph.x_advance.to_length(text.size);
}
offset += text.width;
frame.push(pos, Element::Text(text));
}
frame
}
/// Reshape a range of the shaped text, reusing information from this
/// shaping process if possible.
pub fn reshape(
&'a self,
ctx: &mut LayoutContext,
text_range: Range<usize>,
) -> ShapedText<'a> {
if let Some(glyphs) = self.slice_safe_to_break(text_range.clone()) {
let (size, baseline) = measure(ctx, glyphs, self.style);
Self {
text: &self.text[text_range],
dir: self.dir,
style: self.style,
size,
baseline,
glyphs: Cow::Borrowed(glyphs),
}
} else {
shape(ctx, &self.text[text_range], self.style, self.dir)
}
}
/// Find the subslice of glyphs that represent the given text range if both
/// sides are safe to break.
fn slice_safe_to_break(&self, text_range: Range<usize>) -> Option<&[ShapedGlyph]> {
let Range { mut start, mut end } = text_range;
if !self.dir.is_positive() {
std::mem::swap(&mut start, &mut end);
}
let left = self.find_safe_to_break(start, Side::Left)?;
let right = self.find_safe_to_break(end, Side::Right)?;
Some(&self.glyphs[left .. right])
}
/// Find the glyph offset matching the text index that is most towards the
/// given side and safe-to-break.
fn find_safe_to_break(&self, text_index: usize, towards: Side) -> Option<usize> {
let ltr = self.dir.is_positive();
// Handle edge cases.
let len = self.glyphs.len();
if text_index == 0 {
return Some(if ltr { 0 } else { len });
} else if text_index == self.text.len() {
return Some(if ltr { len } else { 0 });
}
// Find any glyph with the text index.
let mut idx = self
.glyphs
.binary_search_by(|g| {
let ordering = g.text_index.cmp(&text_index);
if ltr { ordering } else { ordering.reverse() }
})
.ok()?;
let next = match towards {
Side::Left => usize::checked_sub,
Side::Right => usize::checked_add,
};
// Search for the outermost glyph with the text index.
while let Some(next) = next(idx, 1) {
if self.glyphs.get(next).map_or(true, |g| g.text_index != text_index) {
break;
}
idx = next;
}
// RTL needs offset one because the left side of the range should be
// exclusive and the right side inclusive, contrary to the normal
// behaviour of ranges.
if !ltr {
idx += 1;
}
self.glyphs[idx].safe_to_break.then(|| idx)
}
}
/// A visual side.
enum Side {
Left,
Right,
}
/// Shape text with font fallback using the `families` iterator.
fn shape_segment<'a>(
fonts: &mut FontStore,
glyphs: &mut Vec<ShapedGlyph>,
base: usize,
text: &str,
variant: FontVariant,
mut families: impl Iterator<Item = &'a str> + Clone,
mut first_face: Option<FaceId>,
dir: Dir,
tags: &[rustybuzz::Feature],
) {
// Select the font family.
let (face_id, fallback) = loop {
// Try to load the next available font family.
match families.next() {
Some(family) => {
if let Some(id) = fonts.select(family, variant) {
break (id, true);
}
}
// We're out of families, so we don't do any more fallback and just
// shape the tofus with the first face we originally used.
None => match first_face {
Some(id) => break (id, false),
None => return,
},
}
};
// Remember the id if this the first available face since we use that one to
// shape tofus.
first_face.get_or_insert(face_id);
// Fill the buffer with our text.
let mut buffer = UnicodeBuffer::new();
buffer.push_str(text);
buffer.set_direction(match dir {
Dir::LTR => rustybuzz::Direction::LeftToRight,
Dir::RTL => rustybuzz::Direction::RightToLeft,
_ => unimplemented!(),
});
// Shape!
let mut face = fonts.get(face_id);
let buffer = rustybuzz::shape(face.ttf(), tags, buffer);
let infos = buffer.glyph_infos();
let pos = buffer.glyph_positions();
// Collect the shaped glyphs, doing fallback and shaping parts again with
// the next font if necessary.
let mut i = 0;
while i < infos.len() {
let info = &infos[i];
let cluster = info.cluster as usize;
if info.glyph_id != 0 || !fallback {
// Add the glyph to the shaped output.
// TODO: Don't ignore y_advance and y_offset.
glyphs.push(ShapedGlyph {
face_id,
glyph_id: info.glyph_id as u16,
x_advance: face.to_em(pos[i].x_advance),
x_offset: face.to_em(pos[i].x_offset),
text_index: base + cluster,
safe_to_break: !info.unsafe_to_break(),
});
} else {
// Determine the source text range for the tofu sequence.
let range = {
// First, search for the end of the tofu sequence.
let k = i;
while infos.get(i + 1).map_or(false, |info| info.glyph_id == 0) {
i += 1;
}
// Then, determine the start and end text index.
//
// Examples:
// Everything is shown in visual order. Tofus are written as "_".
// We want to find out that the tofus span the text `2..6`.
// Note that the clusters are longer than 1 char.
//
// Left-to-right:
// Text: h a l i h a l l o
// Glyphs: A _ _ C E
// Clusters: 0 2 4 6 8
// k=1 i=2
//
// Right-to-left:
// Text: O L L A H I L A H
// Glyphs: E C _ _ A
// Clusters: 8 6 4 2 0
// k=2 i=3
let ltr = dir.is_positive();
let first = if ltr { k } else { i };
let start = infos[first].cluster as usize;
let last = if ltr { i.checked_add(1) } else { k.checked_sub(1) };
let end = last
.and_then(|last| infos.get(last))
.map_or(text.len(), |info| info.cluster as usize);
start .. end
};
// Recursively shape the tofu sequence with the next family.
shape_segment(
fonts,
glyphs,
base + range.start,
&text[range],
variant,
families.clone(),
first_face,
dir,
tags,
);
face = fonts.get(face_id);
}
i += 1;
}
}
/// Apply tracking to a slice of shaped glyphs.
fn track(glyphs: &mut [ShapedGlyph], tracking: Em) {
if tracking.is_zero() {
return;
}
let mut glyphs = glyphs.iter_mut().peekable();
while let Some(glyph) = glyphs.next() {
if glyphs
.peek()
.map_or(false, |next| glyph.text_index != next.text_index)
{
glyph.x_advance += tracking;
}
}
}
/// Measure the size and baseline of a run of shaped glyphs with the given
/// properties.
fn measure(
ctx: &mut LayoutContext,
glyphs: &[ShapedGlyph],
style: &TextStyle,
) -> (Size, Length) {
let mut width = Length::zero();
let mut top = Length::zero();
let mut bottom = Length::zero();
// Expand top and bottom by reading the face's vertical metrics.
let mut expand = |face: &Face| {
top.set_max(face.vertical_metric(style.top_edge, style.size));
bottom.set_max(-face.vertical_metric(style.bottom_edge, style.size));
};
if glyphs.is_empty() {
// When there are no glyphs, we just use the vertical metrics of the
// first available font.
for family in style.families() {
if let Some(face_id) = ctx.fonts.select(family, style.variant) {
expand(ctx.fonts.get(face_id));
break;
}
}
} else {
for (face_id, group) in glyphs.group_by_key(|g| g.face_id) {
let face = ctx.fonts.get(face_id);
expand(face);
for glyph in group {
width += glyph.x_advance.to_length(style.size);
}
}
}
(Size::new(width, top + bottom), top)
}
/// Collect the tags of the OpenType features to apply.
fn tags(features: &FontFeatures) -> Vec<Feature> {
let mut tags = vec![];
let mut feat = |tag, value| {
tags.push(Feature::new(Tag::from_bytes(tag), value, ..));
};
// Features that are on by default in Harfbuzz are only added if disabled.
if !features.kerning {
feat(b"kern", 0);
}
// Features that are off by default in Harfbuzz are only added if enabled.
if features.smallcaps {
feat(b"smcp", 1);
}
if features.alternates {
feat(b"salt", 1);
}
let storage;
if let StylisticSet(Some(set @ 1 ..= 20)) = features.stylistic_set {
storage = [b's', b's', b'0' + set / 10, b'0' + set % 10];
feat(&storage, 1);
}
if !features.ligatures.standard {
feat(b"liga", 0);
feat(b"clig", 0);
}
if features.ligatures.discretionary {
feat(b"dlig", 1);
}
if features.ligatures.historical {
feat(b"hilg", 1);
}
match features.numbers.type_ {
NumberType::Auto => {}
NumberType::Lining => feat(b"lnum", 1),
NumberType::OldStyle => feat(b"onum", 1),
}
match features.numbers.width {
NumberWidth::Auto => {}
NumberWidth::Proportional => feat(b"pnum", 1),
NumberWidth::Tabular => feat(b"tnum", 1),
}
match features.numbers.position {
NumberPosition::Normal => {}
NumberPosition::Subscript => feat(b"subs", 1),
NumberPosition::Superscript => feat(b"sups", 1),
}
if features.numbers.slashed_zero {
feat(b"zero", 1);
}
if features.numbers.fractions {
feat(b"frac", 1);
}
for &(tag, value) in features.raw.iter() {
tags.push(Feature::new(tag, value, ..))
}
tags
}