1mod font_features;
2mod line;
3mod line_layout;
4mod line_wrapper;
5
6use anyhow::anyhow;
7pub use font_features::*;
8pub use line::*;
9pub use line_layout::*;
10use line_wrapper::*;
11use smallvec::SmallVec;
12
13use crate::{
14 px, Bounds, DevicePixels, Hsla, Pixels, PlatformTextSystem, Point, Result, SharedString, Size,
15 UnderlineStyle,
16};
17use collections::HashMap;
18use core::fmt;
19use parking_lot::{Mutex, RwLock, RwLockUpgradableReadGuard};
20use std::{
21 cmp,
22 fmt::{Debug, Display, Formatter},
23 hash::{Hash, Hasher},
24 ops::{Deref, DerefMut},
25 sync::Arc,
26};
27
28#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
29#[repr(C)]
30pub struct FontId(pub usize);
31
32#[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
33pub struct FontFamilyId(pub usize);
34
35pub const SUBPIXEL_VARIANTS: u8 = 4;
36
37pub struct TextSystem {
38 line_layout_cache: Arc<LineLayoutCache>,
39 platform_text_system: Arc<dyn PlatformTextSystem>,
40 font_ids_by_font: RwLock<HashMap<Font, FontId>>,
41 font_metrics: RwLock<HashMap<FontId, FontMetrics>>,
42 wrapper_pool: Mutex<HashMap<FontIdWithSize, Vec<LineWrapper>>>,
43 font_runs_pool: Mutex<Vec<Vec<FontRun>>>,
44}
45
46impl TextSystem {
47 pub fn new(platform_text_system: Arc<dyn PlatformTextSystem>) -> Self {
48 TextSystem {
49 line_layout_cache: Arc::new(LineLayoutCache::new(platform_text_system.clone())),
50 platform_text_system,
51 font_metrics: RwLock::new(HashMap::default()),
52 font_ids_by_font: RwLock::new(HashMap::default()),
53 wrapper_pool: Mutex::new(HashMap::default()),
54 font_runs_pool: Default::default(),
55 }
56 }
57
58 pub fn font_id(&self, font: &Font) -> Result<FontId> {
59 let font_id = self.font_ids_by_font.read().get(font).copied();
60 if let Some(font_id) = font_id {
61 Ok(font_id)
62 } else {
63 let font_id = self.platform_text_system.font_id(font)?;
64 self.font_ids_by_font.write().insert(font.clone(), font_id);
65 Ok(font_id)
66 }
67 }
68
69 pub fn bounding_box(&self, font_id: FontId, font_size: Pixels) -> Result<Bounds<Pixels>> {
70 self.read_metrics(font_id, |metrics| metrics.bounding_box(font_size))
71 }
72
73 pub fn typographic_bounds(
74 &self,
75 font_id: FontId,
76 font_size: Pixels,
77 character: char,
78 ) -> Result<Bounds<Pixels>> {
79 let glyph_id = self
80 .platform_text_system
81 .glyph_for_char(font_id, character)
82 .ok_or_else(|| anyhow!("glyph not found for character '{}'", character))?;
83 let bounds = self
84 .platform_text_system
85 .typographic_bounds(font_id, glyph_id)?;
86 self.read_metrics(font_id, |metrics| {
87 (bounds / metrics.units_per_em as f32 * font_size.0).map(px)
88 })
89 }
90
91 pub fn advance(&self, font_id: FontId, font_size: Pixels, ch: char) -> Result<Size<Pixels>> {
92 let glyph_id = self
93 .platform_text_system
94 .glyph_for_char(font_id, ch)
95 .ok_or_else(|| anyhow!("glyph not found for character '{}'", ch))?;
96 let result = self.platform_text_system.advance(font_id, glyph_id)?
97 / self.units_per_em(font_id)? as f32;
98
99 Ok(result * font_size)
100 }
101
102 pub fn units_per_em(&self, font_id: FontId) -> Result<u32> {
103 self.read_metrics(font_id, |metrics| metrics.units_per_em as u32)
104 }
105
106 pub fn cap_height(&self, font_id: FontId, font_size: Pixels) -> Result<Pixels> {
107 self.read_metrics(font_id, |metrics| metrics.cap_height(font_size))
108 }
109
110 pub fn x_height(&self, font_id: FontId, font_size: Pixels) -> Result<Pixels> {
111 self.read_metrics(font_id, |metrics| metrics.x_height(font_size))
112 }
113
114 pub fn ascent(&self, font_id: FontId, font_size: Pixels) -> Result<Pixels> {
115 self.read_metrics(font_id, |metrics| metrics.ascent(font_size))
116 }
117
118 pub fn descent(&self, font_id: FontId, font_size: Pixels) -> Result<Pixels> {
119 self.read_metrics(font_id, |metrics| metrics.descent(font_size))
120 }
121
122 pub fn baseline_offset(
123 &self,
124 font_id: FontId,
125 font_size: Pixels,
126 line_height: Pixels,
127 ) -> Result<Pixels> {
128 let ascent = self.ascent(font_id, font_size)?;
129 let descent = self.descent(font_id, font_size)?;
130 let padding_top = (line_height - ascent - descent) / 2.;
131 Ok(padding_top + ascent)
132 }
133
134 fn read_metrics<T>(&self, font_id: FontId, read: impl FnOnce(&FontMetrics) -> T) -> Result<T> {
135 let lock = self.font_metrics.upgradable_read();
136
137 if let Some(metrics) = lock.get(&font_id) {
138 Ok(read(metrics))
139 } else {
140 let mut lock = RwLockUpgradableReadGuard::upgrade(lock);
141 let metrics = lock
142 .entry(font_id)
143 .or_insert_with(|| self.platform_text_system.font_metrics(font_id));
144 Ok(read(metrics))
145 }
146 }
147
148 pub fn layout_text(
149 &self,
150 text: &SharedString,
151 font_size: Pixels,
152 runs: &[TextRun],
153 wrap_width: Option<Pixels>,
154 ) -> Result<SmallVec<[Line; 1]>> {
155 let mut runs = runs.iter().cloned().peekable();
156 let mut font_runs = self.font_runs_pool.lock().pop().unwrap_or_default();
157
158 let mut lines = SmallVec::new();
159 let mut line_start = 0;
160 for line_text in text.split('\n') {
161 let line_text = SharedString::from(line_text.to_string());
162 let line_end = line_start + line_text.len();
163
164 let mut last_font: Option<Font> = None;
165 let mut decoration_runs = SmallVec::<[DecorationRun; 32]>::new();
166 let mut run_start = line_start;
167 while run_start < line_end {
168 let Some(run) = runs.peek_mut() else {
169 break;
170 };
171
172 let run_len_within_line = cmp::min(line_end, run_start + run.len) - run_start;
173
174 if last_font == Some(run.font.clone()) {
175 font_runs.last_mut().unwrap().len += run_len_within_line;
176 } else {
177 last_font = Some(run.font.clone());
178 font_runs.push(FontRun {
179 len: run_len_within_line,
180 font_id: self.platform_text_system.font_id(&run.font)?,
181 });
182 }
183
184 if decoration_runs.last().map_or(false, |last_run| {
185 last_run.color == run.color && last_run.underline == run.underline
186 }) {
187 decoration_runs.last_mut().unwrap().len += run_len_within_line as u32;
188 } else {
189 decoration_runs.push(DecorationRun {
190 len: run_len_within_line as u32,
191 color: run.color,
192 underline: run.underline.clone(),
193 });
194 }
195
196 if run_len_within_line == run.len {
197 runs.next();
198 } else {
199 // Preserve the remainder of the run for the next line
200 run.len -= run_len_within_line;
201 }
202 run_start += run_len_within_line;
203 }
204
205 let layout = self
206 .line_layout_cache
207 .layout_line(&line_text, font_size, &font_runs, wrap_width);
208 lines.push(Line {
209 layout,
210 decorations: decoration_runs,
211 });
212
213 line_start = line_end + 1; // Skip `\n` character.
214 font_runs.clear();
215 }
216
217 self.font_runs_pool.lock().push(font_runs);
218
219 Ok(lines)
220 }
221
222 pub fn start_frame(&self) {
223 self.line_layout_cache.start_frame()
224 }
225
226 pub fn line_wrapper(
227 self: &Arc<Self>,
228 font: Font,
229 font_size: Pixels,
230 ) -> Result<LineWrapperHandle> {
231 let lock = &mut self.wrapper_pool.lock();
232 let font_id = self.font_id(&font)?;
233 let wrappers = lock
234 .entry(FontIdWithSize { font_id, font_size })
235 .or_default();
236 let wrapper = wrappers.pop().map(anyhow::Ok).unwrap_or_else(|| {
237 Ok(LineWrapper::new(
238 font_id,
239 font_size,
240 self.platform_text_system.clone(),
241 ))
242 })?;
243
244 Ok(LineWrapperHandle {
245 wrapper: Some(wrapper),
246 text_system: self.clone(),
247 })
248 }
249
250 pub fn raster_bounds(&self, params: &RenderGlyphParams) -> Result<Bounds<DevicePixels>> {
251 self.platform_text_system.glyph_raster_bounds(params)
252 }
253
254 pub fn rasterize_glyph(
255 &self,
256 glyph_id: &RenderGlyphParams,
257 ) -> Result<(Size<DevicePixels>, Vec<u8>)> {
258 self.platform_text_system.rasterize_glyph(glyph_id)
259 }
260}
261
262#[derive(Hash, Eq, PartialEq)]
263struct FontIdWithSize {
264 font_id: FontId,
265 font_size: Pixels,
266}
267
268pub struct LineWrapperHandle {
269 wrapper: Option<LineWrapper>,
270 text_system: Arc<TextSystem>,
271}
272
273impl Drop for LineWrapperHandle {
274 fn drop(&mut self) {
275 let mut state = self.text_system.wrapper_pool.lock();
276 let wrapper = self.wrapper.take().unwrap();
277 state
278 .get_mut(&FontIdWithSize {
279 font_id: wrapper.font_id.clone(),
280 font_size: wrapper.font_size,
281 })
282 .unwrap()
283 .push(wrapper);
284 }
285}
286
287impl Deref for LineWrapperHandle {
288 type Target = LineWrapper;
289
290 fn deref(&self) -> &Self::Target {
291 self.wrapper.as_ref().unwrap()
292 }
293}
294
295impl DerefMut for LineWrapperHandle {
296 fn deref_mut(&mut self) -> &mut Self::Target {
297 self.wrapper.as_mut().unwrap()
298 }
299}
300
301/// The degree of blackness or stroke thickness of a font. This value ranges from 100.0 to 900.0,
302/// with 400.0 as normal.
303#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
304pub struct FontWeight(pub f32);
305
306impl Default for FontWeight {
307 #[inline]
308 fn default() -> FontWeight {
309 FontWeight::NORMAL
310 }
311}
312
313impl Hash for FontWeight {
314 fn hash<H: Hasher>(&self, state: &mut H) {
315 state.write_u32(u32::from_be_bytes(self.0.to_be_bytes()));
316 }
317}
318
319impl Eq for FontWeight {}
320
321impl FontWeight {
322 /// Thin weight (100), the thinnest value.
323 pub const THIN: FontWeight = FontWeight(100.0);
324 /// Extra light weight (200).
325 pub const EXTRA_LIGHT: FontWeight = FontWeight(200.0);
326 /// Light weight (300).
327 pub const LIGHT: FontWeight = FontWeight(300.0);
328 /// Normal (400).
329 pub const NORMAL: FontWeight = FontWeight(400.0);
330 /// Medium weight (500, higher than normal).
331 pub const MEDIUM: FontWeight = FontWeight(500.0);
332 /// Semibold weight (600).
333 pub const SEMIBOLD: FontWeight = FontWeight(600.0);
334 /// Bold weight (700).
335 pub const BOLD: FontWeight = FontWeight(700.0);
336 /// Extra-bold weight (800).
337 pub const EXTRA_BOLD: FontWeight = FontWeight(800.0);
338 /// Black weight (900), the thickest value.
339 pub const BLACK: FontWeight = FontWeight(900.0);
340}
341
342/// Allows italic or oblique faces to be selected.
343#[derive(Clone, Copy, Eq, PartialEq, Debug, Hash)]
344pub enum FontStyle {
345 /// A face that is neither italic not obliqued.
346 Normal,
347 /// A form that is generally cursive in nature.
348 Italic,
349 /// A typically-sloped version of the regular face.
350 Oblique,
351}
352
353impl Default for FontStyle {
354 fn default() -> FontStyle {
355 FontStyle::Normal
356 }
357}
358
359impl Display for FontStyle {
360 fn fmt(&self, f: &mut Formatter) -> fmt::Result {
361 Debug::fmt(self, f)
362 }
363}
364
365#[derive(Clone, Debug, PartialEq, Eq)]
366pub struct TextRun {
367 pub len: usize,
368 pub font: Font,
369 pub color: Hsla,
370 pub underline: Option<UnderlineStyle>,
371}
372
373#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
374#[repr(C)]
375pub struct GlyphId(u32);
376
377impl From<GlyphId> for u32 {
378 fn from(value: GlyphId) -> Self {
379 value.0
380 }
381}
382
383impl From<u16> for GlyphId {
384 fn from(num: u16) -> Self {
385 GlyphId(num as u32)
386 }
387}
388
389impl From<u32> for GlyphId {
390 fn from(num: u32) -> Self {
391 GlyphId(num)
392 }
393}
394
395#[derive(Clone, Debug, PartialEq)]
396pub struct RenderGlyphParams {
397 pub(crate) font_id: FontId,
398 pub(crate) glyph_id: GlyphId,
399 pub(crate) font_size: Pixels,
400 pub(crate) subpixel_variant: Point<u8>,
401 pub(crate) scale_factor: f32,
402 pub(crate) is_emoji: bool,
403}
404
405impl Eq for RenderGlyphParams {}
406
407impl Hash for RenderGlyphParams {
408 fn hash<H: Hasher>(&self, state: &mut H) {
409 self.font_id.0.hash(state);
410 self.glyph_id.0.hash(state);
411 self.font_size.0.to_bits().hash(state);
412 self.subpixel_variant.hash(state);
413 self.scale_factor.to_bits().hash(state);
414 }
415}
416
417#[derive(Clone, Debug, PartialEq)]
418pub struct RenderEmojiParams {
419 pub(crate) font_id: FontId,
420 pub(crate) glyph_id: GlyphId,
421 pub(crate) font_size: Pixels,
422 pub(crate) scale_factor: f32,
423}
424
425impl Eq for RenderEmojiParams {}
426
427impl Hash for RenderEmojiParams {
428 fn hash<H: Hasher>(&self, state: &mut H) {
429 self.font_id.0.hash(state);
430 self.glyph_id.0.hash(state);
431 self.font_size.0.to_bits().hash(state);
432 self.scale_factor.to_bits().hash(state);
433 }
434}
435
436#[derive(Clone, Debug, Eq, PartialEq, Hash)]
437pub struct Font {
438 pub family: SharedString,
439 pub features: FontFeatures,
440 pub weight: FontWeight,
441 pub style: FontStyle,
442}
443
444pub fn font(family: impl Into<SharedString>) -> Font {
445 Font {
446 family: family.into(),
447 features: FontFeatures::default(),
448 weight: FontWeight::default(),
449 style: FontStyle::default(),
450 }
451}
452
453impl Font {
454 pub fn bold(mut self) -> Self {
455 self.weight = FontWeight::BOLD;
456 self
457 }
458}
459
460/// A struct for storing font metrics.
461/// It is used to define the measurements of a typeface.
462#[derive(Clone, Copy, Debug)]
463pub struct FontMetrics {
464 /// The number of font units that make up the "em square",
465 /// a scalable grid for determining the size of a typeface.
466 pub(crate) units_per_em: u32,
467
468 /// The vertical distance from the baseline of the font to the top of the glyph covers.
469 pub(crate) ascent: f32,
470
471 /// The vertical distance from the baseline of the font to the bottom of the glyph covers.
472 pub(crate) descent: f32,
473
474 /// The recommended additional space to add between lines of type.
475 pub(crate) line_gap: f32,
476
477 /// The suggested position of the underline.
478 pub(crate) underline_position: f32,
479
480 /// The suggested thickness of the underline.
481 pub(crate) underline_thickness: f32,
482
483 /// The height of a capital letter measured from the baseline of the font.
484 pub(crate) cap_height: f32,
485
486 /// The height of a lowercase x.
487 pub(crate) x_height: f32,
488
489 /// The outer limits of the area that the font covers.
490 pub(crate) bounding_box: Bounds<f32>,
491}
492
493impl FontMetrics {
494 /// Returns the vertical distance from the baseline of the font to the top of the glyph covers in pixels.
495 pub fn ascent(&self, font_size: Pixels) -> Pixels {
496 Pixels((self.ascent / self.units_per_em as f32) * font_size.0)
497 }
498
499 /// Returns the vertical distance from the baseline of the font to the bottom of the glyph covers in pixels.
500 pub fn descent(&self, font_size: Pixels) -> Pixels {
501 Pixels((self.descent / self.units_per_em as f32) * font_size.0)
502 }
503
504 /// Returns the recommended additional space to add between lines of type in pixels.
505 pub fn line_gap(&self, font_size: Pixels) -> Pixels {
506 Pixels((self.line_gap / self.units_per_em as f32) * font_size.0)
507 }
508
509 /// Returns the suggested position of the underline in pixels.
510 pub fn underline_position(&self, font_size: Pixels) -> Pixels {
511 Pixels((self.underline_position / self.units_per_em as f32) * font_size.0)
512 }
513
514 /// Returns the suggested thickness of the underline in pixels.
515 pub fn underline_thickness(&self, font_size: Pixels) -> Pixels {
516 Pixels((self.underline_thickness / self.units_per_em as f32) * font_size.0)
517 }
518
519 /// Returns the height of a capital letter measured from the baseline of the font in pixels.
520 pub fn cap_height(&self, font_size: Pixels) -> Pixels {
521 Pixels((self.cap_height / self.units_per_em as f32) * font_size.0)
522 }
523
524 /// Returns the height of a lowercase x in pixels.
525 pub fn x_height(&self, font_size: Pixels) -> Pixels {
526 Pixels((self.x_height / self.units_per_em as f32) * font_size.0)
527 }
528
529 /// Returns the outer limits of the area that the font covers in pixels.
530 pub fn bounding_box(&self, font_size: Pixels) -> Bounds<Pixels> {
531 (self.bounding_box / self.units_per_em as f32 * font_size.0).map(px)
532 }
533}