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