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 line_clamp: Option<usize>,
378 ) -> Result<SmallVec<[WrappedLine; 1]>> {
379 let mut runs = runs.iter().filter(|run| run.len > 0).cloned().peekable();
380 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
381
382 let mut lines = SmallVec::new();
383 let mut line_start = 0;
384 let mut max_wrap_lines = line_clamp.unwrap_or(usize::MAX);
385 let mut wrapped_lines = 0;
386
387 let mut process_line = |line_text: SharedString| {
388 let line_end = line_start + line_text.len();
389
390 let mut last_font: Option<Font> = None;
391 let mut decoration_runs = SmallVec::<[DecorationRun; 32]>::new();
392 let mut run_start = line_start;
393 while run_start < line_end {
394 let Some(run) = runs.peek_mut() else {
395 break;
396 };
397
398 let run_len_within_line = cmp::min(line_end, run_start + run.len) - run_start;
399
400 if last_font == Some(run.font.clone()) {
401 font_runs.last_mut().unwrap().len += run_len_within_line;
402 } else {
403 last_font = Some(run.font.clone());
404 font_runs.push(FontRun {
405 len: run_len_within_line,
406 font_id: self.resolve_font(&run.font),
407 });
408 }
409
410 if decoration_runs.last().map_or(false, |last_run| {
411 last_run.color == run.color
412 && last_run.underline == run.underline
413 && last_run.strikethrough == run.strikethrough
414 && last_run.background_color == run.background_color
415 }) {
416 decoration_runs.last_mut().unwrap().len += run_len_within_line as u32;
417 } else {
418 decoration_runs.push(DecorationRun {
419 len: run_len_within_line as u32,
420 color: run.color,
421 background_color: run.background_color,
422 underline: run.underline,
423 strikethrough: run.strikethrough,
424 });
425 }
426
427 if run_len_within_line == run.len {
428 runs.next();
429 } else {
430 // Preserve the remainder of the run for the next line
431 run.len -= run_len_within_line;
432 }
433 run_start += run_len_within_line;
434 }
435
436 let layout = self.line_layout_cache.layout_wrapped_line(
437 &line_text,
438 font_size,
439 &font_runs,
440 wrap_width,
441 Some(max_wrap_lines - wrapped_lines),
442 );
443 wrapped_lines += layout.wrap_boundaries.len();
444
445 lines.push(WrappedLine {
446 layout,
447 decoration_runs,
448 text: line_text,
449 });
450
451 // Skip `\n` character.
452 line_start = line_end + 1;
453 if let Some(run) = runs.peek_mut() {
454 run.len -= 1;
455 if run.len == 0 {
456 runs.next();
457 }
458 }
459
460 font_runs.clear();
461 };
462
463 let mut split_lines = text.split('\n');
464 let mut processed = false;
465
466 if let Some(first_line) = split_lines.next() {
467 if let Some(second_line) = split_lines.next() {
468 processed = true;
469 process_line(first_line.to_string().into());
470 process_line(second_line.to_string().into());
471 for line_text in split_lines {
472 process_line(line_text.to_string().into());
473 }
474 }
475 }
476
477 if !processed {
478 process_line(text);
479 }
480
481 self.font_runs_pool.lock().push(font_runs);
482
483 Ok(lines)
484 }
485
486 pub(crate) fn finish_frame(&self) {
487 self.line_layout_cache.finish_frame()
488 }
489
490 /// Layout the given line of text, at the given font_size.
491 /// Subsets of the line can be styled independently with the `runs` parameter.
492 /// Generally, you should prefer to use `TextLayout::shape_line` instead, which
493 /// can be painted directly.
494 pub fn layout_line<Text>(
495 &self,
496 text: Text,
497 font_size: Pixels,
498 runs: &[TextRun],
499 ) -> Result<Arc<LineLayout>>
500 where
501 Text: AsRef<str>,
502 SharedString: From<Text>,
503 {
504 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
505 for run in runs.iter() {
506 let font_id = self.resolve_font(&run.font);
507 if let Some(last_run) = font_runs.last_mut() {
508 if last_run.font_id == font_id {
509 last_run.len += run.len;
510 continue;
511 }
512 }
513 font_runs.push(FontRun {
514 len: run.len,
515 font_id,
516 });
517 }
518
519 let layout = self
520 .line_layout_cache
521 .layout_line(text, font_size, &font_runs);
522
523 font_runs.clear();
524 self.font_runs_pool.lock().push(font_runs);
525
526 Ok(layout)
527 }
528}
529
530#[derive(Hash, Eq, PartialEq)]
531struct FontIdWithSize {
532 font_id: FontId,
533 font_size: Pixels,
534}
535
536/// A handle into the text system, which can be used to compute the wrapped layout of text
537pub struct LineWrapperHandle {
538 wrapper: Option<LineWrapper>,
539 text_system: Arc<TextSystem>,
540}
541
542impl Drop for LineWrapperHandle {
543 fn drop(&mut self) {
544 let mut state = self.text_system.wrapper_pool.lock();
545 let wrapper = self.wrapper.take().unwrap();
546 state
547 .get_mut(&FontIdWithSize {
548 font_id: wrapper.font_id,
549 font_size: wrapper.font_size,
550 })
551 .unwrap()
552 .push(wrapper);
553 }
554}
555
556impl Deref for LineWrapperHandle {
557 type Target = LineWrapper;
558
559 fn deref(&self) -> &Self::Target {
560 self.wrapper.as_ref().unwrap()
561 }
562}
563
564impl DerefMut for LineWrapperHandle {
565 fn deref_mut(&mut self) -> &mut Self::Target {
566 self.wrapper.as_mut().unwrap()
567 }
568}
569
570/// The degree of blackness or stroke thickness of a font. This value ranges from 100.0 to 900.0,
571/// with 400.0 as normal.
572#[derive(Clone, Copy, Debug, PartialEq, PartialOrd, Deserialize, Serialize, JsonSchema)]
573pub struct FontWeight(pub f32);
574
575impl Default for FontWeight {
576 #[inline]
577 fn default() -> FontWeight {
578 FontWeight::NORMAL
579 }
580}
581
582impl Hash for FontWeight {
583 fn hash<H: Hasher>(&self, state: &mut H) {
584 state.write_u32(u32::from_be_bytes(self.0.to_be_bytes()));
585 }
586}
587
588impl Eq for FontWeight {}
589
590impl FontWeight {
591 /// Thin weight (100), the thinnest value.
592 pub const THIN: FontWeight = FontWeight(100.0);
593 /// Extra light weight (200).
594 pub const EXTRA_LIGHT: FontWeight = FontWeight(200.0);
595 /// Light weight (300).
596 pub const LIGHT: FontWeight = FontWeight(300.0);
597 /// Normal (400).
598 pub const NORMAL: FontWeight = FontWeight(400.0);
599 /// Medium weight (500, higher than normal).
600 pub const MEDIUM: FontWeight = FontWeight(500.0);
601 /// Semibold weight (600).
602 pub const SEMIBOLD: FontWeight = FontWeight(600.0);
603 /// Bold weight (700).
604 pub const BOLD: FontWeight = FontWeight(700.0);
605 /// Extra-bold weight (800).
606 pub const EXTRA_BOLD: FontWeight = FontWeight(800.0);
607 /// Black weight (900), the thickest value.
608 pub const BLACK: FontWeight = FontWeight(900.0);
609
610 /// All of the font weights, in order from thinnest to thickest.
611 pub const ALL: [FontWeight; 9] = [
612 Self::THIN,
613 Self::EXTRA_LIGHT,
614 Self::LIGHT,
615 Self::NORMAL,
616 Self::MEDIUM,
617 Self::SEMIBOLD,
618 Self::BOLD,
619 Self::EXTRA_BOLD,
620 Self::BLACK,
621 ];
622}
623
624/// Allows italic or oblique faces to be selected.
625#[derive(Clone, Copy, Eq, PartialEq, Debug, Hash, Default)]
626pub enum FontStyle {
627 /// A face that is neither italic not obliqued.
628 #[default]
629 Normal,
630 /// A form that is generally cursive in nature.
631 Italic,
632 /// A typically-sloped version of the regular face.
633 Oblique,
634}
635
636impl Display for FontStyle {
637 fn fmt(&self, f: &mut Formatter) -> fmt::Result {
638 Debug::fmt(self, f)
639 }
640}
641
642/// A styled run of text, for use in [`TextLayout`].
643#[derive(Clone, Debug, PartialEq, Eq)]
644pub struct TextRun {
645 /// A number of utf8 bytes
646 pub len: usize,
647 /// The font to use for this run.
648 pub font: Font,
649 /// The color
650 pub color: Hsla,
651 /// The background color (if any)
652 pub background_color: Option<Hsla>,
653 /// The underline style (if any)
654 pub underline: Option<UnderlineStyle>,
655 /// The strikethrough style (if any)
656 pub strikethrough: Option<StrikethroughStyle>,
657}
658
659/// An identifier for a specific glyph, as returned by [`TextSystem::layout_line`].
660#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
661#[repr(C)]
662pub struct GlyphId(pub(crate) u32);
663
664#[derive(Clone, Debug, PartialEq)]
665pub(crate) struct RenderGlyphParams {
666 pub(crate) font_id: FontId,
667 pub(crate) glyph_id: GlyphId,
668 pub(crate) font_size: Pixels,
669 pub(crate) subpixel_variant: Point<u8>,
670 pub(crate) scale_factor: f32,
671 pub(crate) is_emoji: bool,
672}
673
674impl Eq for RenderGlyphParams {}
675
676impl Hash for RenderGlyphParams {
677 fn hash<H: Hasher>(&self, state: &mut H) {
678 self.font_id.0.hash(state);
679 self.glyph_id.0.hash(state);
680 self.font_size.0.to_bits().hash(state);
681 self.subpixel_variant.hash(state);
682 self.scale_factor.to_bits().hash(state);
683 self.is_emoji.hash(state);
684 }
685}
686
687/// The configuration details for identifying a specific font.
688#[derive(Clone, Debug, Eq, PartialEq, Hash)]
689pub struct Font {
690 /// The font family name.
691 ///
692 /// The special name ".SystemUIFont" is used to identify the system UI font, which varies based on platform.
693 pub family: SharedString,
694
695 /// The font features to use.
696 pub features: FontFeatures,
697
698 /// The fallbacks fonts to use.
699 pub fallbacks: Option<FontFallbacks>,
700
701 /// The font weight.
702 pub weight: FontWeight,
703
704 /// The font style.
705 pub style: FontStyle,
706}
707
708/// Get a [`Font`] for a given name.
709pub fn font(family: impl Into<SharedString>) -> Font {
710 Font {
711 family: family.into(),
712 features: FontFeatures::default(),
713 weight: FontWeight::default(),
714 style: FontStyle::default(),
715 fallbacks: None,
716 }
717}
718
719impl Font {
720 /// Set this Font to be bold
721 pub fn bold(mut self) -> Self {
722 self.weight = FontWeight::BOLD;
723 self
724 }
725
726 /// Set this Font to be italic
727 pub fn italic(mut self) -> Self {
728 self.style = FontStyle::Italic;
729 self
730 }
731}
732
733/// A struct for storing font metrics.
734/// It is used to define the measurements of a typeface.
735#[derive(Clone, Copy, Debug)]
736pub struct FontMetrics {
737 /// The number of font units that make up the "em square",
738 /// a scalable grid for determining the size of a typeface.
739 pub(crate) units_per_em: u32,
740
741 /// The vertical distance from the baseline of the font to the top of the glyph covers.
742 pub(crate) ascent: f32,
743
744 /// The vertical distance from the baseline of the font to the bottom of the glyph covers.
745 pub(crate) descent: f32,
746
747 /// The recommended additional space to add between lines of type.
748 pub(crate) line_gap: f32,
749
750 /// The suggested position of the underline.
751 pub(crate) underline_position: f32,
752
753 /// The suggested thickness of the underline.
754 pub(crate) underline_thickness: f32,
755
756 /// The height of a capital letter measured from the baseline of the font.
757 pub(crate) cap_height: f32,
758
759 /// The height of a lowercase x.
760 pub(crate) x_height: f32,
761
762 /// The outer limits of the area that the font covers.
763 /// Corresponds to the xMin / xMax / yMin / yMax values in the OpenType `head` table
764 pub(crate) bounding_box: Bounds<f32>,
765}
766
767impl FontMetrics {
768 /// Returns the vertical distance from the baseline of the font to the top of the glyph covers in pixels.
769 pub fn ascent(&self, font_size: Pixels) -> Pixels {
770 Pixels((self.ascent / self.units_per_em as f32) * font_size.0)
771 }
772
773 /// Returns the vertical distance from the baseline of the font to the bottom of the glyph covers in pixels.
774 pub fn descent(&self, font_size: Pixels) -> Pixels {
775 Pixels((self.descent / self.units_per_em as f32) * font_size.0)
776 }
777
778 /// Returns the recommended additional space to add between lines of type in pixels.
779 pub fn line_gap(&self, font_size: Pixels) -> Pixels {
780 Pixels((self.line_gap / self.units_per_em as f32) * font_size.0)
781 }
782
783 /// Returns the suggested position of the underline in pixels.
784 pub fn underline_position(&self, font_size: Pixels) -> Pixels {
785 Pixels((self.underline_position / self.units_per_em as f32) * font_size.0)
786 }
787
788 /// Returns the suggested thickness of the underline in pixels.
789 pub fn underline_thickness(&self, font_size: Pixels) -> Pixels {
790 Pixels((self.underline_thickness / self.units_per_em as f32) * font_size.0)
791 }
792
793 /// Returns the height of a capital letter measured from the baseline of the font in pixels.
794 pub fn cap_height(&self, font_size: Pixels) -> Pixels {
795 Pixels((self.cap_height / self.units_per_em as f32) * font_size.0)
796 }
797
798 /// Returns the height of a lowercase x in pixels.
799 pub fn x_height(&self, font_size: Pixels) -> Pixels {
800 Pixels((self.x_height / self.units_per_em as f32) * font_size.0)
801 }
802
803 /// Returns the outer limits of the area that the font covers in pixels.
804 pub fn bounding_box(&self, font_size: Pixels) -> Bounds<Pixels> {
805 (self.bounding_box / self.units_per_em as f32 * font_size.0).map(px)
806 }
807}