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