1mod font_fallbacks;
2mod font_features;
3mod line;
4mod line_layout;
5mod line_wrapper;
6
7pub use font_fallbacks::*;
8pub use font_features::*;
9pub use line::*;
10pub use line_layout::*;
11pub use line_wrapper::*;
12use schemars::JsonSchema;
13use serde::{Deserialize, Serialize};
14
15use crate::{
16 px, Bounds, DevicePixels, Hsla, Pixels, PlatformTextSystem, Point, Result, SharedString, Size,
17 StrikethroughStyle, UnderlineStyle,
18};
19use anyhow::anyhow;
20use collections::{BTreeSet, FxHashMap};
21use core::fmt;
22use derive_more::Deref;
23use itertools::Itertools;
24use parking_lot::{Mutex, RwLock, RwLockUpgradableReadGuard};
25use smallvec::{smallvec, SmallVec};
26use std::{
27 borrow::Cow,
28 cmp,
29 fmt::{Debug, Display, Formatter},
30 hash::{Hash, Hasher},
31 ops::{Deref, DerefMut, Range},
32 sync::Arc,
33};
34
35/// An opaque identifier for a specific font.
36#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
37#[repr(C)]
38pub struct FontId(pub usize);
39
40/// An opaque identifier for a specific font family.
41#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
42pub struct FontFamilyId(pub usize);
43
44pub(crate) const SUBPIXEL_VARIANTS: u8 = 4;
45
46/// The GPUI text rendering sub system.
47pub struct TextSystem {
48 platform_text_system: Arc<dyn PlatformTextSystem>,
49 font_ids_by_font: RwLock<FxHashMap<Font, Result<FontId>>>,
50 font_metrics: RwLock<FxHashMap<FontId, FontMetrics>>,
51 raster_bounds: RwLock<FxHashMap<RenderGlyphParams, Bounds<DevicePixels>>>,
52 wrapper_pool: Mutex<FxHashMap<FontIdWithSize, Vec<LineWrapper>>>,
53 font_runs_pool: Mutex<Vec<Vec<FontRun>>>,
54 fallback_font_stack: SmallVec<[Font; 2]>,
55}
56
57impl TextSystem {
58 pub(crate) fn new(platform_text_system: Arc<dyn PlatformTextSystem>) -> Self {
59 TextSystem {
60 platform_text_system,
61 font_metrics: RwLock::default(),
62 raster_bounds: RwLock::default(),
63 font_ids_by_font: RwLock::default(),
64 wrapper_pool: Mutex::default(),
65 font_runs_pool: Mutex::default(),
66 fallback_font_stack: smallvec![
67 // TODO: Remove this when Linux have implemented setting fallbacks.
68 font("Zed Plex Mono"),
69 font("Helvetica"),
70 font("Segoe UI"), // Windows
71 font("Cantarell"), // Gnome
72 font("Ubuntu"), // Gnome (Ubuntu)
73 font("Noto Sans"), // KDE
74 font("DejaVu Sans")
75 ],
76 }
77 }
78
79 /// Get a list of all available font names from the operating system.
80 pub fn all_font_names(&self) -> Vec<String> {
81 let mut names: BTreeSet<_> = self
82 .platform_text_system
83 .all_font_names()
84 .into_iter()
85 .collect();
86 names.extend(self.platform_text_system.all_font_families());
87 names.extend(
88 self.fallback_font_stack
89 .iter()
90 .map(|font| font.family.to_string()),
91 );
92 names.into_iter().collect()
93 }
94
95 /// Add a font's data to the text system.
96 pub fn add_fonts(&self, fonts: Vec<Cow<'static, [u8]>>) -> Result<()> {
97 self.platform_text_system.add_fonts(fonts)
98 }
99
100 /// Get the FontId for the configure font family and style.
101 pub fn font_id(&self, font: &Font) -> Result<FontId> {
102 fn clone_font_id_result(font_id: &Result<FontId>) -> Result<FontId> {
103 match font_id {
104 Ok(font_id) => Ok(*font_id),
105 Err(err) => Err(anyhow!("{}", err)),
106 }
107 }
108
109 let font_id = self
110 .font_ids_by_font
111 .read()
112 .get(font)
113 .map(clone_font_id_result);
114 if let Some(font_id) = font_id {
115 font_id
116 } else {
117 let font_id = self.platform_text_system.font_id(font);
118 self.font_ids_by_font
119 .write()
120 .insert(font.clone(), clone_font_id_result(&font_id));
121 font_id
122 }
123 }
124
125 /// Get the Font for the Font Id.
126 pub fn get_font_for_id(&self, id: FontId) -> Option<Font> {
127 let lock = self.font_ids_by_font.read();
128 lock.iter()
129 .filter_map(|(font, result)| match result {
130 Ok(font_id) if *font_id == id => Some(font.clone()),
131 _ => None,
132 })
133 .next()
134 }
135
136 /// Resolves the specified font, falling back to the default font stack if
137 /// the font fails to load.
138 ///
139 /// # Panics
140 ///
141 /// Panics if the font and none of the fallbacks can be resolved.
142 pub fn resolve_font(&self, font: &Font) -> FontId {
143 if let Ok(font_id) = self.font_id(font) {
144 return font_id;
145 }
146 for fallback in &self.fallback_font_stack {
147 if let Ok(font_id) = self.font_id(fallback) {
148 return font_id;
149 }
150 }
151
152 panic!(
153 "failed to resolve font '{}' or any of the fallbacks: {}",
154 font.family,
155 self.fallback_font_stack
156 .iter()
157 .map(|fallback| &fallback.family)
158 .join(", ")
159 );
160 }
161
162 /// Get the bounding box for the given font and font size.
163 /// A font's bounding box is the smallest rectangle that could enclose all glyphs
164 /// in the font. superimposed over one another.
165 pub fn bounding_box(&self, font_id: FontId, font_size: Pixels) -> Bounds<Pixels> {
166 self.read_metrics(font_id, |metrics| metrics.bounding_box(font_size))
167 }
168
169 /// Get the typographic bounds for the given character, in the given font and size.
170 pub fn typographic_bounds(
171 &self,
172 font_id: FontId,
173 font_size: Pixels,
174 character: char,
175 ) -> Result<Bounds<Pixels>> {
176 let glyph_id = self
177 .platform_text_system
178 .glyph_for_char(font_id, character)
179 .ok_or_else(|| anyhow!("glyph not found for character '{}'", character))?;
180 let bounds = self
181 .platform_text_system
182 .typographic_bounds(font_id, glyph_id)?;
183 Ok(self.read_metrics(font_id, |metrics| {
184 (bounds / metrics.units_per_em as f32 * font_size.0).map(px)
185 }))
186 }
187
188 /// Get the advance width for the given character, in the given font and size.
189 pub fn advance(&self, font_id: FontId, font_size: Pixels, ch: char) -> Result<Size<Pixels>> {
190 let glyph_id = self
191 .platform_text_system
192 .glyph_for_char(font_id, ch)
193 .ok_or_else(|| anyhow!("glyph not found for character '{}'", ch))?;
194 let result = self.platform_text_system.advance(font_id, glyph_id)?
195 / self.units_per_em(font_id) as f32;
196
197 Ok(result * font_size)
198 }
199
200 /// Get the number of font size units per 'em square',
201 /// Per MDN: "an abstract square whose height is the intended distance between
202 /// lines of type in the same type size"
203 pub fn units_per_em(&self, font_id: FontId) -> u32 {
204 self.read_metrics(font_id, |metrics| metrics.units_per_em)
205 }
206
207 /// Get the height of a capital letter in the given font and size.
208 pub fn cap_height(&self, font_id: FontId, font_size: Pixels) -> Pixels {
209 self.read_metrics(font_id, |metrics| metrics.cap_height(font_size))
210 }
211
212 /// Get the height of the x character in the given font and size.
213 pub fn x_height(&self, font_id: FontId, font_size: Pixels) -> Pixels {
214 self.read_metrics(font_id, |metrics| metrics.x_height(font_size))
215 }
216
217 /// Get the recommended distance from the baseline for the given font
218 pub fn ascent(&self, font_id: FontId, font_size: Pixels) -> Pixels {
219 self.read_metrics(font_id, |metrics| metrics.ascent(font_size))
220 }
221
222 /// Get the recommended distance below the baseline for the given font,
223 /// in single spaced text.
224 pub fn descent(&self, font_id: FontId, font_size: Pixels) -> Pixels {
225 self.read_metrics(font_id, |metrics| metrics.descent(font_size))
226 }
227
228 /// Get the recommended baseline offset for the given font and line height.
229 pub fn baseline_offset(
230 &self,
231 font_id: FontId,
232 font_size: Pixels,
233 line_height: Pixels,
234 ) -> Pixels {
235 let ascent = self.ascent(font_id, font_size);
236 let descent = self.descent(font_id, font_size);
237 let padding_top = (line_height - ascent - descent) / 2.;
238 padding_top + ascent
239 }
240
241 fn read_metrics<T>(&self, font_id: FontId, read: impl FnOnce(&FontMetrics) -> T) -> T {
242 let lock = self.font_metrics.upgradable_read();
243
244 if let Some(metrics) = lock.get(&font_id) {
245 read(metrics)
246 } else {
247 let mut lock = RwLockUpgradableReadGuard::upgrade(lock);
248 let metrics = lock
249 .entry(font_id)
250 .or_insert_with(|| self.platform_text_system.font_metrics(font_id));
251 read(metrics)
252 }
253 }
254
255 /// Returns a handle to a line wrapper, for the given font and font size.
256 pub fn line_wrapper(self: &Arc<Self>, font: Font, font_size: Pixels) -> LineWrapperHandle {
257 let lock = &mut self.wrapper_pool.lock();
258 let font_id = self.resolve_font(&font);
259 let wrappers = lock
260 .entry(FontIdWithSize { font_id, font_size })
261 .or_default();
262 let wrapper = wrappers.pop().unwrap_or_else(|| {
263 LineWrapper::new(font_id, font_size, self.platform_text_system.clone())
264 });
265
266 LineWrapperHandle {
267 wrapper: Some(wrapper),
268 text_system: self.clone(),
269 }
270 }
271
272 /// Get the rasterized size and location of a specific, rendered glyph.
273 pub(crate) fn raster_bounds(&self, params: &RenderGlyphParams) -> Result<Bounds<DevicePixels>> {
274 let raster_bounds = self.raster_bounds.upgradable_read();
275 if let Some(bounds) = raster_bounds.get(params) {
276 Ok(*bounds)
277 } else {
278 let mut raster_bounds = RwLockUpgradableReadGuard::upgrade(raster_bounds);
279 let bounds = self.platform_text_system.glyph_raster_bounds(params)?;
280 raster_bounds.insert(params.clone(), bounds);
281 Ok(bounds)
282 }
283 }
284
285 pub(crate) fn rasterize_glyph(
286 &self,
287 params: &RenderGlyphParams,
288 ) -> Result<(Size<DevicePixels>, Vec<u8>)> {
289 let raster_bounds = self.raster_bounds(params)?;
290 self.platform_text_system
291 .rasterize_glyph(params, raster_bounds)
292 }
293}
294
295/// The GPUI text layout subsystem.
296#[derive(Deref)]
297pub struct WindowTextSystem {
298 line_layout_cache: LineLayoutCache,
299 #[deref]
300 text_system: Arc<TextSystem>,
301}
302
303impl WindowTextSystem {
304 pub(crate) fn new(text_system: Arc<TextSystem>) -> Self {
305 Self {
306 line_layout_cache: LineLayoutCache::new(text_system.platform_text_system.clone()),
307 text_system,
308 }
309 }
310
311 pub(crate) fn layout_index(&self) -> LineLayoutIndex {
312 self.line_layout_cache.layout_index()
313 }
314
315 pub(crate) fn reuse_layouts(&self, index: Range<LineLayoutIndex>) {
316 self.line_layout_cache.reuse_layouts(index)
317 }
318
319 pub(crate) fn truncate_layouts(&self, index: LineLayoutIndex) {
320 self.line_layout_cache.truncate_layouts(index)
321 }
322
323 /// Shape the given line, at the given font_size, for painting to the screen.
324 /// Subsets of the line can be styled independently with the `runs` parameter.
325 ///
326 /// Note that this method can only shape a single line of text. It will panic
327 /// if the text contains newlines. If you need to shape multiple lines of text,
328 /// use `TextLayout::shape_text` instead.
329 pub fn shape_line(
330 &self,
331 text: SharedString,
332 font_size: Pixels,
333 runs: &[TextRun],
334 ) -> Result<ShapedLine> {
335 debug_assert!(
336 text.find('\n').is_none(),
337 "text argument should not contain newlines"
338 );
339
340 let mut decoration_runs = SmallVec::<[DecorationRun; 32]>::new();
341 for run in runs {
342 if let Some(last_run) = decoration_runs.last_mut() {
343 if last_run.color == run.color
344 && last_run.underline == run.underline
345 && last_run.strikethrough == run.strikethrough
346 && last_run.background_color == run.background_color
347 {
348 last_run.len += run.len as u32;
349 continue;
350 }
351 }
352 decoration_runs.push(DecorationRun {
353 len: run.len as u32,
354 color: run.color,
355 background_color: run.background_color,
356 underline: run.underline,
357 strikethrough: run.strikethrough,
358 });
359 }
360
361 let layout = self.layout_line(text.as_ref(), font_size, runs)?;
362
363 Ok(ShapedLine {
364 layout,
365 text,
366 decoration_runs,
367 })
368 }
369
370 /// Shape a multi line string of text, at the given font_size, for painting to the screen.
371 /// Subsets of the text can be styled independently with the `runs` parameter.
372 /// If `wrap_width` is provided, the line breaks will be adjusted to fit within the given width.
373 pub fn shape_text(
374 &self,
375 text: SharedString,
376 font_size: Pixels,
377 runs: &[TextRun],
378 wrap_width: Option<Pixels>,
379 ) -> Result<SmallVec<[WrappedLine; 1]>> {
380 let mut runs = runs.iter().filter(|run| run.len > 0).cloned().peekable();
381 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
382
383 let mut lines = SmallVec::new();
384 let mut line_start = 0;
385
386 let mut process_line = |line_text: SharedString| {
387 let line_end = line_start + line_text.len();
388
389 let mut last_font: Option<Font> = None;
390 let mut decoration_runs = SmallVec::<[DecorationRun; 32]>::new();
391 let mut run_start = line_start;
392 while run_start < line_end {
393 let Some(run) = runs.peek_mut() else {
394 break;
395 };
396
397 let run_len_within_line = cmp::min(line_end, run_start + run.len) - run_start;
398
399 if last_font == Some(run.font.clone()) {
400 font_runs.last_mut().unwrap().len += run_len_within_line;
401 } else {
402 last_font = Some(run.font.clone());
403 font_runs.push(FontRun {
404 len: run_len_within_line,
405 font_id: self.resolve_font(&run.font),
406 });
407 }
408
409 if decoration_runs.last().map_or(false, |last_run| {
410 last_run.color == run.color
411 && last_run.underline == run.underline
412 && last_run.strikethrough == run.strikethrough
413 && last_run.background_color == run.background_color
414 }) {
415 decoration_runs.last_mut().unwrap().len += run_len_within_line as u32;
416 } else {
417 decoration_runs.push(DecorationRun {
418 len: run_len_within_line as u32,
419 color: run.color,
420 background_color: run.background_color,
421 underline: run.underline,
422 strikethrough: run.strikethrough,
423 });
424 }
425
426 if run_len_within_line == run.len {
427 runs.next();
428 } else {
429 // Preserve the remainder of the run for the next line
430 run.len -= run_len_within_line;
431 }
432 run_start += run_len_within_line;
433 }
434
435 let layout = self
436 .line_layout_cache
437 .layout_wrapped_line(&line_text, font_size, &font_runs, wrap_width);
438
439 lines.push(WrappedLine {
440 layout,
441 decoration_runs,
442 text: line_text,
443 });
444
445 // Skip `\n` character.
446 line_start = line_end + 1;
447 if let Some(run) = runs.peek_mut() {
448 run.len -= 1;
449 if run.len == 0 {
450 runs.next();
451 }
452 }
453
454 font_runs.clear();
455 };
456
457 let mut split_lines = text.split('\n');
458 let mut processed = false;
459
460 if let Some(first_line) = split_lines.next() {
461 if let Some(second_line) = split_lines.next() {
462 processed = true;
463 process_line(first_line.to_string().into());
464 process_line(second_line.to_string().into());
465 for line_text in split_lines {
466 process_line(line_text.to_string().into());
467 }
468 }
469 }
470
471 if !processed {
472 process_line(text);
473 }
474
475 self.font_runs_pool.lock().push(font_runs);
476
477 Ok(lines)
478 }
479
480 pub(crate) fn finish_frame(&self) {
481 self.line_layout_cache.finish_frame()
482 }
483
484 /// Layout the given line of text, at the given font_size.
485 /// Subsets of the line can be styled independently with the `runs` parameter.
486 /// Generally, you should prefer to use `TextLayout::shape_line` instead, which
487 /// can be painted directly.
488 pub fn layout_line(
489 &self,
490 text: &str,
491 font_size: Pixels,
492 runs: &[TextRun],
493 ) -> Result<Arc<LineLayout>> {
494 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
495 for run in runs.iter() {
496 let font_id = self.resolve_font(&run.font);
497 if let Some(last_run) = font_runs.last_mut() {
498 if last_run.font_id == font_id {
499 last_run.len += run.len;
500 continue;
501 }
502 }
503 font_runs.push(FontRun {
504 len: run.len,
505 font_id,
506 });
507 }
508
509 let layout = self
510 .line_layout_cache
511 .layout_line(text, font_size, &font_runs);
512
513 font_runs.clear();
514 self.font_runs_pool.lock().push(font_runs);
515
516 Ok(layout)
517 }
518}
519
520#[derive(Hash, Eq, PartialEq)]
521struct FontIdWithSize {
522 font_id: FontId,
523 font_size: Pixels,
524}
525
526/// A handle into the text system, which can be used to compute the wrapped layout of text
527pub struct LineWrapperHandle {
528 wrapper: Option<LineWrapper>,
529 text_system: Arc<TextSystem>,
530}
531
532impl Drop for LineWrapperHandle {
533 fn drop(&mut self) {
534 let mut state = self.text_system.wrapper_pool.lock();
535 let wrapper = self.wrapper.take().unwrap();
536 state
537 .get_mut(&FontIdWithSize {
538 font_id: wrapper.font_id,
539 font_size: wrapper.font_size,
540 })
541 .unwrap()
542 .push(wrapper);
543 }
544}
545
546impl Deref for LineWrapperHandle {
547 type Target = LineWrapper;
548
549 fn deref(&self) -> &Self::Target {
550 self.wrapper.as_ref().unwrap()
551 }
552}
553
554impl DerefMut for LineWrapperHandle {
555 fn deref_mut(&mut self) -> &mut Self::Target {
556 self.wrapper.as_mut().unwrap()
557 }
558}
559
560/// The degree of blackness or stroke thickness of a font. This value ranges from 100.0 to 900.0,
561/// with 400.0 as normal.
562#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Deserialize, Serialize, JsonSchema)]
563pub struct FontWeight(pub f32);
564
565impl Default for FontWeight {
566 #[inline]
567 fn default() -> FontWeight {
568 FontWeight::NORMAL
569 }
570}
571
572impl Hash for FontWeight {
573 fn hash<H: Hasher>(&self, state: &mut H) {
574 state.write_u32(u32::from_be_bytes(self.0.to_be_bytes()));
575 }
576}
577
578impl Eq for FontWeight {}
579
580impl FontWeight {
581 /// Thin weight (100), the thinnest value.
582 pub const THIN: FontWeight = FontWeight(100.0);
583 /// Extra light weight (200).
584 pub const EXTRA_LIGHT: FontWeight = FontWeight(200.0);
585 /// Light weight (300).
586 pub const LIGHT: FontWeight = FontWeight(300.0);
587 /// Normal (400).
588 pub const NORMAL: FontWeight = FontWeight(400.0);
589 /// Medium weight (500, higher than normal).
590 pub const MEDIUM: FontWeight = FontWeight(500.0);
591 /// Semibold weight (600).
592 pub const SEMIBOLD: FontWeight = FontWeight(600.0);
593 /// Bold weight (700).
594 pub const BOLD: FontWeight = FontWeight(700.0);
595 /// Extra-bold weight (800).
596 pub const EXTRA_BOLD: FontWeight = FontWeight(800.0);
597 /// Black weight (900), the thickest value.
598 pub const BLACK: FontWeight = FontWeight(900.0);
599
600 /// All of the font weights, in order from thinnest to thickest.
601 pub const ALL: [FontWeight; 9] = [
602 Self::THIN,
603 Self::EXTRA_LIGHT,
604 Self::LIGHT,
605 Self::NORMAL,
606 Self::MEDIUM,
607 Self::SEMIBOLD,
608 Self::BOLD,
609 Self::EXTRA_BOLD,
610 Self::BLACK,
611 ];
612}
613
614/// Allows italic or oblique faces to be selected.
615#[derive(Clone, Copy, Eq, PartialEq, Debug, Hash, Default)]
616pub enum FontStyle {
617 /// A face that is neither italic not obliqued.
618 #[default]
619 Normal,
620 /// A form that is generally cursive in nature.
621 Italic,
622 /// A typically-sloped version of the regular face.
623 Oblique,
624}
625
626impl Display for FontStyle {
627 fn fmt(&self, f: &mut Formatter) -> fmt::Result {
628 Debug::fmt(self, f)
629 }
630}
631
632/// A styled run of text, for use in [`TextLayout`].
633#[derive(Clone, Debug, PartialEq, Eq)]
634pub struct TextRun {
635 /// A number of utf8 bytes
636 pub len: usize,
637 /// The font to use for this run.
638 pub font: Font,
639 /// The color
640 pub color: Hsla,
641 /// The background color (if any)
642 pub background_color: Option<Hsla>,
643 /// The underline style (if any)
644 pub underline: Option<UnderlineStyle>,
645 /// The strikethrough style (if any)
646 pub strikethrough: Option<StrikethroughStyle>,
647}
648
649/// An identifier for a specific glyph, as returned by [`TextSystem::layout_line`].
650#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
651#[repr(C)]
652pub struct GlyphId(pub(crate) u32);
653
654#[derive(Clone, Debug, PartialEq)]
655pub(crate) struct RenderGlyphParams {
656 pub(crate) font_id: FontId,
657 pub(crate) glyph_id: GlyphId,
658 pub(crate) font_size: Pixels,
659 pub(crate) subpixel_variant: Point<u8>,
660 pub(crate) scale_factor: f32,
661 pub(crate) is_emoji: bool,
662}
663
664impl Eq for RenderGlyphParams {}
665
666impl Hash for RenderGlyphParams {
667 fn hash<H: Hasher>(&self, state: &mut H) {
668 self.font_id.0.hash(state);
669 self.glyph_id.0.hash(state);
670 self.font_size.0.to_bits().hash(state);
671 self.subpixel_variant.hash(state);
672 self.scale_factor.to_bits().hash(state);
673 }
674}
675
676/// The configuration details for identifying a specific font.
677#[derive(Clone, Debug, Eq, PartialEq, Hash)]
678pub struct Font {
679 /// The font family name.
680 ///
681 /// The special name ".SystemUIFont" is used to identify the system UI font, which varies based on platform.
682 pub family: SharedString,
683
684 /// The font features to use.
685 pub features: FontFeatures,
686
687 /// The fallbacks fonts to use.
688 pub fallbacks: Option<FontFallbacks>,
689
690 /// The font weight.
691 pub weight: FontWeight,
692
693 /// The font style.
694 pub style: FontStyle,
695}
696
697/// Get a [`Font`] for a given name.
698pub fn font(family: impl Into<SharedString>) -> Font {
699 Font {
700 family: family.into(),
701 features: FontFeatures::default(),
702 weight: FontWeight::default(),
703 style: FontStyle::default(),
704 fallbacks: None,
705 }
706}
707
708impl Font {
709 /// Set this Font to be bold
710 pub fn bold(mut self) -> Self {
711 self.weight = FontWeight::BOLD;
712 self
713 }
714
715 /// Set this Font to be italic
716 pub fn italic(mut self) -> Self {
717 self.style = FontStyle::Italic;
718 self
719 }
720}
721
722/// A struct for storing font metrics.
723/// It is used to define the measurements of a typeface.
724#[derive(Clone, Copy, Debug)]
725pub struct FontMetrics {
726 /// The number of font units that make up the "em square",
727 /// a scalable grid for determining the size of a typeface.
728 pub(crate) units_per_em: u32,
729
730 /// The vertical distance from the baseline of the font to the top of the glyph covers.
731 pub(crate) ascent: f32,
732
733 /// The vertical distance from the baseline of the font to the bottom of the glyph covers.
734 pub(crate) descent: f32,
735
736 /// The recommended additional space to add between lines of type.
737 pub(crate) line_gap: f32,
738
739 /// The suggested position of the underline.
740 pub(crate) underline_position: f32,
741
742 /// The suggested thickness of the underline.
743 pub(crate) underline_thickness: f32,
744
745 /// The height of a capital letter measured from the baseline of the font.
746 pub(crate) cap_height: f32,
747
748 /// The height of a lowercase x.
749 pub(crate) x_height: f32,
750
751 /// The outer limits of the area that the font covers.
752 /// Corresponds to the xMin / xMax / yMin / yMax values in the OpenType `head` table
753 pub(crate) bounding_box: Bounds<f32>,
754}
755
756impl FontMetrics {
757 /// Returns the vertical distance from the baseline of the font to the top of the glyph covers in pixels.
758 pub fn ascent(&self, font_size: Pixels) -> Pixels {
759 Pixels((self.ascent / self.units_per_em as f32) * font_size.0)
760 }
761
762 /// Returns the vertical distance from the baseline of the font to the bottom of the glyph covers in pixels.
763 pub fn descent(&self, font_size: Pixels) -> Pixels {
764 Pixels((self.descent / self.units_per_em as f32) * font_size.0)
765 }
766
767 /// Returns the recommended additional space to add between lines of type in pixels.
768 pub fn line_gap(&self, font_size: Pixels) -> Pixels {
769 Pixels((self.line_gap / self.units_per_em as f32) * font_size.0)
770 }
771
772 /// Returns the suggested position of the underline in pixels.
773 pub fn underline_position(&self, font_size: Pixels) -> Pixels {
774 Pixels((self.underline_position / self.units_per_em as f32) * font_size.0)
775 }
776
777 /// Returns the suggested thickness of the underline in pixels.
778 pub fn underline_thickness(&self, font_size: Pixels) -> Pixels {
779 Pixels((self.underline_thickness / self.units_per_em as f32) * font_size.0)
780 }
781
782 /// Returns the height of a capital letter measured from the baseline of the font in pixels.
783 pub fn cap_height(&self, font_size: Pixels) -> Pixels {
784 Pixels((self.cap_height / self.units_per_em as f32) * font_size.0)
785 }
786
787 /// Returns the height of a lowercase x in pixels.
788 pub fn x_height(&self, font_size: Pixels) -> Pixels {
789 Pixels((self.x_height / self.units_per_em as f32) * font_size.0)
790 }
791
792 /// Returns the outer limits of the area that the font covers in pixels.
793 pub fn bounding_box(&self, font_size: Pixels) -> Bounds<Pixels> {
794 (self.bounding_box / self.units_per_em as f32 * font_size.0).map(px)
795 }
796}