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