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::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 = self.platform_text_system.all_font_names();
82 names.extend(
83 self.fallback_font_stack
84 .iter()
85 .map(|font| font.family.to_string()),
86 );
87 names.push(".SystemUIFont".to_string());
88 names.sort();
89 names.dedup();
90 names
91 }
92
93 /// Add a font's data to the text system.
94 pub fn add_fonts(&self, fonts: Vec<Cow<'static, [u8]>>) -> Result<()> {
95 self.platform_text_system.add_fonts(fonts)
96 }
97
98 /// Get the FontId for the configure font family and style.
99 pub fn font_id(&self, font: &Font) -> Result<FontId> {
100 fn clone_font_id_result(font_id: &Result<FontId>) -> Result<FontId> {
101 match font_id {
102 Ok(font_id) => Ok(*font_id),
103 Err(err) => Err(anyhow!("{}", err)),
104 }
105 }
106
107 let font_id = self
108 .font_ids_by_font
109 .read()
110 .get(font)
111 .map(clone_font_id_result);
112 if let Some(font_id) = font_id {
113 font_id
114 } else {
115 let font_id = self.platform_text_system.font_id(font);
116 self.font_ids_by_font
117 .write()
118 .insert(font.clone(), clone_font_id_result(&font_id));
119 font_id
120 }
121 }
122
123 /// Get the Font for the Font Id.
124 pub fn get_font_for_id(&self, id: FontId) -> Option<Font> {
125 let lock = self.font_ids_by_font.read();
126 lock.iter()
127 .filter_map(|(font, result)| match result {
128 Ok(font_id) if *font_id == id => Some(font.clone()),
129 _ => None,
130 })
131 .next()
132 }
133
134 /// Resolves the specified font, falling back to the default font stack if
135 /// the font fails to load.
136 ///
137 /// # Panics
138 ///
139 /// Panics if the font and none of the fallbacks can be resolved.
140 pub fn resolve_font(&self, font: &Font) -> FontId {
141 if let Ok(font_id) = self.font_id(font) {
142 return font_id;
143 }
144 for fallback in &self.fallback_font_stack {
145 if let Ok(font_id) = self.font_id(fallback) {
146 return font_id;
147 }
148 }
149
150 panic!(
151 "failed to resolve font '{}' or any of the fallbacks: {}",
152 font.family,
153 self.fallback_font_stack
154 .iter()
155 .map(|fallback| &fallback.family)
156 .join(", ")
157 );
158 }
159
160 /// Get the bounding box for the given font and font size.
161 /// A font's bounding box is the smallest rectangle that could enclose all glyphs
162 /// in the font. superimposed over one another.
163 pub fn bounding_box(&self, font_id: FontId, font_size: Pixels) -> Bounds<Pixels> {
164 self.read_metrics(font_id, |metrics| metrics.bounding_box(font_size))
165 }
166
167 /// Get the typographic bounds for the given character, in the given font and size.
168 pub fn typographic_bounds(
169 &self,
170 font_id: FontId,
171 font_size: Pixels,
172 character: char,
173 ) -> Result<Bounds<Pixels>> {
174 let glyph_id = self
175 .platform_text_system
176 .glyph_for_char(font_id, character)
177 .ok_or_else(|| anyhow!("glyph not found for character '{}'", character))?;
178 let bounds = self
179 .platform_text_system
180 .typographic_bounds(font_id, glyph_id)?;
181 Ok(self.read_metrics(font_id, |metrics| {
182 (bounds / metrics.units_per_em as f32 * font_size.0).map(px)
183 }))
184 }
185
186 /// Get the advance width for the given character, in the given font and size.
187 pub fn advance(&self, font_id: FontId, font_size: Pixels, ch: char) -> Result<Size<Pixels>> {
188 let glyph_id = self
189 .platform_text_system
190 .glyph_for_char(font_id, ch)
191 .ok_or_else(|| anyhow!("glyph not found for character '{}'", ch))?;
192 let result = self.platform_text_system.advance(font_id, glyph_id)?
193 / self.units_per_em(font_id) as f32;
194
195 Ok(result * font_size)
196 }
197
198 /// Get the number of font size units per 'em square',
199 /// Per MDN: "an abstract square whose height is the intended distance between
200 /// lines of type in the same type size"
201 pub fn units_per_em(&self, font_id: FontId) -> u32 {
202 self.read_metrics(font_id, |metrics| metrics.units_per_em)
203 }
204
205 /// Get the height of a capital letter in the given font and size.
206 pub fn cap_height(&self, font_id: FontId, font_size: Pixels) -> Pixels {
207 self.read_metrics(font_id, |metrics| metrics.cap_height(font_size))
208 }
209
210 /// Get the height of the x character in the given font and size.
211 pub fn x_height(&self, font_id: FontId, font_size: Pixels) -> Pixels {
212 self.read_metrics(font_id, |metrics| metrics.x_height(font_size))
213 }
214
215 /// Get the recommended distance from the baseline for the given font
216 pub fn ascent(&self, font_id: FontId, font_size: Pixels) -> Pixels {
217 self.read_metrics(font_id, |metrics| metrics.ascent(font_size))
218 }
219
220 /// Get the recommended distance below the baseline for the given font,
221 /// in single spaced text.
222 pub fn descent(&self, font_id: FontId, font_size: Pixels) -> Pixels {
223 self.read_metrics(font_id, |metrics| metrics.descent(font_size))
224 }
225
226 /// Get the recommended baseline offset for the given font and line height.
227 pub fn baseline_offset(
228 &self,
229 font_id: FontId,
230 font_size: Pixels,
231 line_height: Pixels,
232 ) -> Pixels {
233 let ascent = self.ascent(font_id, font_size);
234 let descent = self.descent(font_id, font_size);
235 let padding_top = (line_height - ascent - descent) / 2.;
236 padding_top + ascent
237 }
238
239 fn read_metrics<T>(&self, font_id: FontId, read: impl FnOnce(&FontMetrics) -> T) -> T {
240 let lock = self.font_metrics.upgradable_read();
241
242 if let Some(metrics) = lock.get(&font_id) {
243 read(metrics)
244 } else {
245 let mut lock = RwLockUpgradableReadGuard::upgrade(lock);
246 let metrics = lock
247 .entry(font_id)
248 .or_insert_with(|| self.platform_text_system.font_metrics(font_id));
249 read(metrics)
250 }
251 }
252
253 /// Returns a handle to a line wrapper, for the given font and font size.
254 pub fn line_wrapper(self: &Arc<Self>, font: Font, font_size: Pixels) -> LineWrapperHandle {
255 let lock = &mut self.wrapper_pool.lock();
256 let font_id = self.resolve_font(&font);
257 let wrappers = lock
258 .entry(FontIdWithSize { font_id, font_size })
259 .or_default();
260 let wrapper = wrappers.pop().unwrap_or_else(|| {
261 LineWrapper::new(font_id, font_size, self.platform_text_system.clone())
262 });
263
264 LineWrapperHandle {
265 wrapper: Some(wrapper),
266 text_system: self.clone(),
267 }
268 }
269
270 /// Get the rasterized size and location of a specific, rendered glyph.
271 pub(crate) fn raster_bounds(&self, params: &RenderGlyphParams) -> Result<Bounds<DevicePixels>> {
272 let raster_bounds = self.raster_bounds.upgradable_read();
273 if let Some(bounds) = raster_bounds.get(params) {
274 Ok(*bounds)
275 } else {
276 let mut raster_bounds = RwLockUpgradableReadGuard::upgrade(raster_bounds);
277 let bounds = self.platform_text_system.glyph_raster_bounds(params)?;
278 raster_bounds.insert(params.clone(), bounds);
279 Ok(bounds)
280 }
281 }
282
283 pub(crate) fn rasterize_glyph(
284 &self,
285 params: &RenderGlyphParams,
286 ) -> Result<(Size<DevicePixels>, Vec<u8>)> {
287 let raster_bounds = self.raster_bounds(params)?;
288 self.platform_text_system
289 .rasterize_glyph(params, raster_bounds)
290 }
291}
292
293/// The GPUI text layout subsystem.
294#[derive(Deref)]
295pub struct WindowTextSystem {
296 line_layout_cache: LineLayoutCache,
297 #[deref]
298 text_system: Arc<TextSystem>,
299}
300
301impl WindowTextSystem {
302 pub(crate) fn new(text_system: Arc<TextSystem>) -> Self {
303 Self {
304 line_layout_cache: LineLayoutCache::new(text_system.platform_text_system.clone()),
305 text_system,
306 }
307 }
308
309 pub(crate) fn layout_index(&self) -> LineLayoutIndex {
310 self.line_layout_cache.layout_index()
311 }
312
313 pub(crate) fn reuse_layouts(&self, index: Range<LineLayoutIndex>) {
314 self.line_layout_cache.reuse_layouts(index)
315 }
316
317 pub(crate) fn truncate_layouts(&self, index: LineLayoutIndex) {
318 self.line_layout_cache.truncate_layouts(index)
319 }
320
321 /// Shape the given line, at the given font_size, for painting to the screen.
322 /// Subsets of the line can be styled independently with the `runs` parameter.
323 ///
324 /// Note that this method can only shape a single line of text. It will panic
325 /// if the text contains newlines. If you need to shape multiple lines of text,
326 /// use `TextLayout::shape_text` instead.
327 pub fn shape_line(
328 &self,
329 text: SharedString,
330 font_size: Pixels,
331 runs: &[TextRun],
332 ) -> Result<ShapedLine> {
333 debug_assert!(
334 text.find('\n').is_none(),
335 "text argument should not contain newlines"
336 );
337
338 let mut decoration_runs = SmallVec::<[DecorationRun; 32]>::new();
339 for run in runs {
340 if let Some(last_run) = decoration_runs.last_mut() {
341 if last_run.color == run.color
342 && last_run.underline == run.underline
343 && last_run.strikethrough == run.strikethrough
344 && last_run.background_color == run.background_color
345 {
346 last_run.len += run.len as u32;
347 continue;
348 }
349 }
350 decoration_runs.push(DecorationRun {
351 len: run.len as u32,
352 color: run.color,
353 background_color: run.background_color,
354 underline: run.underline,
355 strikethrough: run.strikethrough,
356 });
357 }
358
359 let layout = self.layout_line(&text, font_size, runs)?;
360
361 Ok(ShapedLine {
362 layout,
363 text,
364 decoration_runs,
365 })
366 }
367
368 /// Shape a multi line string of text, at the given font_size, for painting to the screen.
369 /// Subsets of the text can be styled independently with the `runs` parameter.
370 /// If `wrap_width` is provided, the line breaks will be adjusted to fit within the given width.
371 pub fn shape_text(
372 &self,
373 text: SharedString,
374 font_size: Pixels,
375 runs: &[TextRun],
376 wrap_width: Option<Pixels>,
377 ) -> Result<SmallVec<[WrappedLine; 1]>> {
378 let mut runs = runs.iter().filter(|run| run.len > 0).cloned().peekable();
379 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
380
381 let mut lines = SmallVec::new();
382 let mut line_start = 0;
383
384 let mut process_line = |line_text: SharedString| {
385 let line_end = line_start + line_text.len();
386
387 let mut last_font: Option<Font> = None;
388 let mut decoration_runs = SmallVec::<[DecorationRun; 32]>::new();
389 let mut run_start = line_start;
390 while run_start < line_end {
391 let Some(run) = runs.peek_mut() else {
392 break;
393 };
394
395 let run_len_within_line = cmp::min(line_end, run_start + run.len) - run_start;
396
397 if last_font == Some(run.font.clone()) {
398 font_runs.last_mut().unwrap().len += run_len_within_line;
399 } else {
400 last_font = Some(run.font.clone());
401 font_runs.push(FontRun {
402 len: run_len_within_line,
403 font_id: self.resolve_font(&run.font),
404 });
405 }
406
407 if decoration_runs.last().map_or(false, |last_run| {
408 last_run.color == run.color
409 && last_run.underline == run.underline
410 && last_run.strikethrough == run.strikethrough
411 && last_run.background_color == run.background_color
412 }) {
413 decoration_runs.last_mut().unwrap().len += run_len_within_line as u32;
414 } else {
415 decoration_runs.push(DecorationRun {
416 len: run_len_within_line as u32,
417 color: run.color,
418 background_color: run.background_color,
419 underline: run.underline,
420 strikethrough: run.strikethrough,
421 });
422 }
423
424 if run_len_within_line == run.len {
425 runs.next();
426 } else {
427 // Preserve the remainder of the run for the next line
428 run.len -= run_len_within_line;
429 }
430 run_start += run_len_within_line;
431 }
432
433 let layout = self
434 .line_layout_cache
435 .layout_wrapped_line(&line_text, font_size, &font_runs, wrap_width);
436
437 lines.push(WrappedLine {
438 layout,
439 decoration_runs,
440 text: line_text,
441 });
442
443 // Skip `\n` character.
444 line_start = line_end + 1;
445 if let Some(run) = runs.peek_mut() {
446 run.len -= 1;
447 if run.len == 0 {
448 runs.next();
449 }
450 }
451
452 font_runs.clear();
453 };
454
455 let mut split_lines = text.split('\n');
456 let mut processed = false;
457
458 if let Some(first_line) = split_lines.next() {
459 if let Some(second_line) = split_lines.next() {
460 processed = true;
461 process_line(first_line.to_string().into());
462 process_line(second_line.to_string().into());
463 for line_text in split_lines {
464 process_line(line_text.to_string().into());
465 }
466 }
467 }
468
469 if !processed {
470 process_line(text);
471 }
472
473 self.font_runs_pool.lock().push(font_runs);
474
475 Ok(lines)
476 }
477
478 pub(crate) fn finish_frame(&self) {
479 self.line_layout_cache.finish_frame()
480 }
481
482 /// Layout the given line of text, at the given font_size.
483 /// Subsets of the line can be styled independently with the `runs` parameter.
484 /// Generally, you should prefer to use `TextLayout::shape_line` instead, which
485 /// can be painted directly.
486 pub fn layout_line<Text>(
487 &self,
488 text: Text,
489 font_size: Pixels,
490 runs: &[TextRun],
491 ) -> Result<Arc<LineLayout>>
492 where
493 Text: AsRef<str>,
494 SharedString: From<Text>,
495 {
496 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
497 for run in runs.iter() {
498 let font_id = self.resolve_font(&run.font);
499 if let Some(last_run) = font_runs.last_mut() {
500 if last_run.font_id == font_id {
501 last_run.len += run.len;
502 continue;
503 }
504 }
505 font_runs.push(FontRun {
506 len: run.len,
507 font_id,
508 });
509 }
510
511 let layout = self
512 .line_layout_cache
513 .layout_line(text, font_size, &font_runs);
514
515 font_runs.clear();
516 self.font_runs_pool.lock().push(font_runs);
517
518 Ok(layout)
519 }
520}
521
522#[derive(Hash, Eq, PartialEq)]
523struct FontIdWithSize {
524 font_id: FontId,
525 font_size: Pixels,
526}
527
528/// A handle into the text system, which can be used to compute the wrapped layout of text
529pub struct LineWrapperHandle {
530 wrapper: Option<LineWrapper>,
531 text_system: Arc<TextSystem>,
532}
533
534impl Drop for LineWrapperHandle {
535 fn drop(&mut self) {
536 let mut state = self.text_system.wrapper_pool.lock();
537 let wrapper = self.wrapper.take().unwrap();
538 state
539 .get_mut(&FontIdWithSize {
540 font_id: wrapper.font_id,
541 font_size: wrapper.font_size,
542 })
543 .unwrap()
544 .push(wrapper);
545 }
546}
547
548impl Deref for LineWrapperHandle {
549 type Target = LineWrapper;
550
551 fn deref(&self) -> &Self::Target {
552 self.wrapper.as_ref().unwrap()
553 }
554}
555
556impl DerefMut for LineWrapperHandle {
557 fn deref_mut(&mut self) -> &mut Self::Target {
558 self.wrapper.as_mut().unwrap()
559 }
560}
561
562/// The degree of blackness or stroke thickness of a font. This value ranges from 100.0 to 900.0,
563/// with 400.0 as normal.
564#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Deserialize, Serialize, JsonSchema)]
565pub struct FontWeight(pub f32);
566
567impl Default for FontWeight {
568 #[inline]
569 fn default() -> FontWeight {
570 FontWeight::NORMAL
571 }
572}
573
574impl Hash for FontWeight {
575 fn hash<H: Hasher>(&self, state: &mut H) {
576 state.write_u32(u32::from_be_bytes(self.0.to_be_bytes()));
577 }
578}
579
580impl Eq for FontWeight {}
581
582impl FontWeight {
583 /// Thin weight (100), the thinnest value.
584 pub const THIN: FontWeight = FontWeight(100.0);
585 /// Extra light weight (200).
586 pub const EXTRA_LIGHT: FontWeight = FontWeight(200.0);
587 /// Light weight (300).
588 pub const LIGHT: FontWeight = FontWeight(300.0);
589 /// Normal (400).
590 pub const NORMAL: FontWeight = FontWeight(400.0);
591 /// Medium weight (500, higher than normal).
592 pub const MEDIUM: FontWeight = FontWeight(500.0);
593 /// Semibold weight (600).
594 pub const SEMIBOLD: FontWeight = FontWeight(600.0);
595 /// Bold weight (700).
596 pub const BOLD: FontWeight = FontWeight(700.0);
597 /// Extra-bold weight (800).
598 pub const EXTRA_BOLD: FontWeight = FontWeight(800.0);
599 /// Black weight (900), the thickest value.
600 pub const BLACK: FontWeight = FontWeight(900.0);
601
602 /// All of the font weights, in order from thinnest to thickest.
603 pub const ALL: [FontWeight; 9] = [
604 Self::THIN,
605 Self::EXTRA_LIGHT,
606 Self::LIGHT,
607 Self::NORMAL,
608 Self::MEDIUM,
609 Self::SEMIBOLD,
610 Self::BOLD,
611 Self::EXTRA_BOLD,
612 Self::BLACK,
613 ];
614}
615
616/// Allows italic or oblique faces to be selected.
617#[derive(Clone, Copy, Eq, PartialEq, Debug, Hash, Default)]
618pub enum FontStyle {
619 /// A face that is neither italic not obliqued.
620 #[default]
621 Normal,
622 /// A form that is generally cursive in nature.
623 Italic,
624 /// A typically-sloped version of the regular face.
625 Oblique,
626}
627
628impl Display for FontStyle {
629 fn fmt(&self, f: &mut Formatter) -> fmt::Result {
630 Debug::fmt(self, f)
631 }
632}
633
634/// A styled run of text, for use in [`TextLayout`].
635#[derive(Clone, Debug, PartialEq, Eq)]
636pub struct TextRun {
637 /// A number of utf8 bytes
638 pub len: usize,
639 /// The font to use for this run.
640 pub font: Font,
641 /// The color
642 pub color: Hsla,
643 /// The background color (if any)
644 pub background_color: Option<Hsla>,
645 /// The underline style (if any)
646 pub underline: Option<UnderlineStyle>,
647 /// The strikethrough style (if any)
648 pub strikethrough: Option<StrikethroughStyle>,
649}
650
651/// An identifier for a specific glyph, as returned by [`TextSystem::layout_line`].
652#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
653#[repr(C)]
654pub struct GlyphId(pub(crate) u32);
655
656#[derive(Clone, Debug, PartialEq)]
657pub(crate) struct RenderGlyphParams {
658 pub(crate) font_id: FontId,
659 pub(crate) glyph_id: GlyphId,
660 pub(crate) font_size: Pixels,
661 pub(crate) subpixel_variant: Point<u8>,
662 pub(crate) scale_factor: f32,
663 pub(crate) is_emoji: bool,
664}
665
666impl Eq for RenderGlyphParams {}
667
668impl Hash for RenderGlyphParams {
669 fn hash<H: Hasher>(&self, state: &mut H) {
670 self.font_id.0.hash(state);
671 self.glyph_id.0.hash(state);
672 self.font_size.0.to_bits().hash(state);
673 self.subpixel_variant.hash(state);
674 self.scale_factor.to_bits().hash(state);
675 self.is_emoji.hash(state);
676 }
677}
678
679/// The configuration details for identifying a specific font.
680#[derive(Clone, Debug, Eq, PartialEq, Hash)]
681pub struct Font {
682 /// The font family name.
683 ///
684 /// The special name ".SystemUIFont" is used to identify the system UI font, which varies based on platform.
685 pub family: SharedString,
686
687 /// The font features to use.
688 pub features: FontFeatures,
689
690 /// The fallbacks fonts to use.
691 pub fallbacks: Option<FontFallbacks>,
692
693 /// The font weight.
694 pub weight: FontWeight,
695
696 /// The font style.
697 pub style: FontStyle,
698}
699
700/// Get a [`Font`] for a given name.
701pub fn font(family: impl Into<SharedString>) -> Font {
702 Font {
703 family: family.into(),
704 features: FontFeatures::default(),
705 weight: FontWeight::default(),
706 style: FontStyle::default(),
707 fallbacks: None,
708 }
709}
710
711impl Font {
712 /// Set this Font to be bold
713 pub fn bold(mut self) -> Self {
714 self.weight = FontWeight::BOLD;
715 self
716 }
717
718 /// Set this Font to be italic
719 pub fn italic(mut self) -> Self {
720 self.style = FontStyle::Italic;
721 self
722 }
723}
724
725/// A struct for storing font metrics.
726/// It is used to define the measurements of a typeface.
727#[derive(Clone, Copy, Debug)]
728pub struct FontMetrics {
729 /// The number of font units that make up the "em square",
730 /// a scalable grid for determining the size of a typeface.
731 pub(crate) units_per_em: u32,
732
733 /// The vertical distance from the baseline of the font to the top of the glyph covers.
734 pub(crate) ascent: f32,
735
736 /// The vertical distance from the baseline of the font to the bottom of the glyph covers.
737 pub(crate) descent: f32,
738
739 /// The recommended additional space to add between lines of type.
740 pub(crate) line_gap: f32,
741
742 /// The suggested position of the underline.
743 pub(crate) underline_position: f32,
744
745 /// The suggested thickness of the underline.
746 pub(crate) underline_thickness: f32,
747
748 /// The height of a capital letter measured from the baseline of the font.
749 pub(crate) cap_height: f32,
750
751 /// The height of a lowercase x.
752 pub(crate) x_height: f32,
753
754 /// The outer limits of the area that the font covers.
755 /// Corresponds to the xMin / xMax / yMin / yMax values in the OpenType `head` table
756 pub(crate) bounding_box: Bounds<f32>,
757}
758
759impl FontMetrics {
760 /// Returns the vertical distance from the baseline of the font to the top of the glyph covers in pixels.
761 pub fn ascent(&self, font_size: Pixels) -> Pixels {
762 Pixels((self.ascent / self.units_per_em as f32) * font_size.0)
763 }
764
765 /// Returns the vertical distance from the baseline of the font to the bottom of the glyph covers in pixels.
766 pub fn descent(&self, font_size: Pixels) -> Pixels {
767 Pixels((self.descent / self.units_per_em as f32) * font_size.0)
768 }
769
770 /// Returns the recommended additional space to add between lines of type in pixels.
771 pub fn line_gap(&self, font_size: Pixels) -> Pixels {
772 Pixels((self.line_gap / self.units_per_em as f32) * font_size.0)
773 }
774
775 /// Returns the suggested position of the underline in pixels.
776 pub fn underline_position(&self, font_size: Pixels) -> Pixels {
777 Pixels((self.underline_position / self.units_per_em as f32) * font_size.0)
778 }
779
780 /// Returns the suggested thickness of the underline in pixels.
781 pub fn underline_thickness(&self, font_size: Pixels) -> Pixels {
782 Pixels((self.underline_thickness / self.units_per_em as f32) * font_size.0)
783 }
784
785 /// Returns the height of a capital letter measured from the baseline of the font in pixels.
786 pub fn cap_height(&self, font_size: Pixels) -> Pixels {
787 Pixels((self.cap_height / self.units_per_em as f32) * font_size.0)
788 }
789
790 /// Returns the height of a lowercase x in pixels.
791 pub fn x_height(&self, font_size: Pixels) -> Pixels {
792 Pixels((self.x_height / self.units_per_em as f32) * font_size.0)
793 }
794
795 /// Returns the outer limits of the area that the font covers in pixels.
796 pub fn bounding_box(&self, font_size: Pixels) -> Bounds<Pixels> {
797 (self.bounding_box / self.units_per_em as f32 * font_size.0).map(px)
798 }
799}