1use crate::{
2 App, Bounds, DevicePixels, Half, Hsla, LineLayout, Pixels, Point, RenderGlyphParams, Result,
3 ShapedGlyph, ShapedRun, SharedString, StrikethroughStyle, TextAlign, UnderlineStyle, Window,
4 WrapBoundary, WrappedLineLayout, black, fill, point, px, size,
5};
6use derive_more::{Deref, DerefMut};
7use smallvec::SmallVec;
8use std::sync::Arc;
9
10/// Pre-computed glyph data for efficient painting without per-glyph cache lookups.
11///
12/// This is produced by `ShapedLine::compute_glyph_raster_data` during prepaint
13/// and consumed by `ShapedLine::paint_with_raster_data` during paint.
14#[derive(Clone, Debug)]
15pub struct GlyphRasterData {
16 /// The raster bounds for each glyph, in paint order.
17 pub bounds: Vec<Bounds<DevicePixels>>,
18 /// The render params for each glyph (needed for sprite atlas lookup).
19 pub params: Vec<RenderGlyphParams>,
20}
21
22/// Set the text decoration for a run of text.
23#[derive(Debug, Clone)]
24pub struct DecorationRun {
25 /// The length of the run in utf-8 bytes.
26 pub len: u32,
27
28 /// The color for this run
29 pub color: Hsla,
30
31 /// The background color for this run
32 pub background_color: Option<Hsla>,
33
34 /// The underline style for this run
35 pub underline: Option<UnderlineStyle>,
36
37 /// The strikethrough style for this run
38 pub strikethrough: Option<StrikethroughStyle>,
39}
40
41/// A line of text that has been shaped and decorated.
42#[derive(Clone, Default, Debug, Deref, DerefMut)]
43pub struct ShapedLine {
44 #[deref]
45 #[deref_mut]
46 pub(crate) layout: Arc<LineLayout>,
47 /// The text that was shaped for this line.
48 pub text: SharedString,
49 pub(crate) decoration_runs: SmallVec<[DecorationRun; 32]>,
50}
51
52impl ShapedLine {
53 /// The length of the line in utf-8 bytes.
54 #[allow(clippy::len_without_is_empty)]
55 pub fn len(&self) -> usize {
56 self.layout.len
57 }
58
59 /// The width of the shaped line in pixels.
60 ///
61 /// This is the glyph advance width computed by the text shaping system and is useful for
62 /// incrementally advancing a "pen" when painting multiple fragments on the same row.
63 pub fn width(&self) -> Pixels {
64 self.layout.width
65 }
66
67 /// Override the len, useful if you're rendering text a
68 /// as text b (e.g. rendering invisibles).
69 pub fn with_len(mut self, len: usize) -> Self {
70 let layout = self.layout.as_ref();
71 self.layout = Arc::new(LineLayout {
72 font_size: layout.font_size,
73 width: layout.width,
74 ascent: layout.ascent,
75 descent: layout.descent,
76 runs: layout.runs.clone(),
77 len,
78 });
79 self
80 }
81
82 /// Paint the line of text to the window.
83 pub fn paint(
84 &self,
85 origin: Point<Pixels>,
86 line_height: Pixels,
87 align: TextAlign,
88 align_width: Option<Pixels>,
89 window: &mut Window,
90 cx: &mut App,
91 ) -> Result<()> {
92 paint_line(
93 origin,
94 &self.layout,
95 line_height,
96 align,
97 align_width,
98 &self.decoration_runs,
99 &[],
100 window,
101 cx,
102 )?;
103
104 Ok(())
105 }
106
107 /// Paint the background of the line to the window.
108 pub fn paint_background(
109 &self,
110 origin: Point<Pixels>,
111 line_height: Pixels,
112 align: TextAlign,
113 align_width: Option<Pixels>,
114 window: &mut Window,
115 cx: &mut App,
116 ) -> Result<()> {
117 paint_line_background(
118 origin,
119 &self.layout,
120 line_height,
121 align,
122 align_width,
123 &self.decoration_runs,
124 &[],
125 window,
126 cx,
127 )?;
128
129 Ok(())
130 }
131
132 /// Split this shaped line at a byte index, returning `(prefix, suffix)`.
133 ///
134 /// - `prefix` contains glyphs for bytes `[0, byte_index)` with original positions.
135 /// Its width equals the x-advance up to the split point.
136 /// - `suffix` contains glyphs for bytes `[byte_index, len)` with positions
137 /// shifted left so the first glyph starts at x=0, and byte indices rebased to 0.
138 /// - Decoration runs are partitioned at the boundary; a run that straddles it is
139 /// split into two with adjusted lengths.
140 /// - `font_size`, `ascent`, and `descent` are copied to both halves.
141 pub fn split_at(&self, byte_index: usize) -> (ShapedLine, ShapedLine) {
142 let x_offset = self.layout.x_for_index(byte_index);
143
144 // Partition glyph runs. A single run may contribute glyphs to both halves.
145 let mut left_runs = Vec::new();
146 let mut right_runs = Vec::new();
147
148 for run in &self.layout.runs {
149 let split_pos = run.glyphs.partition_point(|g| g.index < byte_index);
150
151 if split_pos > 0 {
152 left_runs.push(ShapedRun {
153 font_id: run.font_id,
154 glyphs: run.glyphs[..split_pos].to_vec(),
155 });
156 }
157
158 if split_pos < run.glyphs.len() {
159 let right_glyphs = run.glyphs[split_pos..]
160 .iter()
161 .map(|g| ShapedGlyph {
162 id: g.id,
163 position: point(g.position.x - x_offset, g.position.y),
164 index: g.index - byte_index,
165 is_emoji: g.is_emoji,
166 })
167 .collect();
168 right_runs.push(ShapedRun {
169 font_id: run.font_id,
170 glyphs: right_glyphs,
171 });
172 }
173 }
174
175 // Partition decoration runs. A run straddling the boundary is split into two.
176 let mut left_decorations = SmallVec::new();
177 let mut right_decorations = SmallVec::new();
178 let mut decoration_offset = 0u32;
179 let split_point = byte_index as u32;
180
181 for decoration in &self.decoration_runs {
182 let run_end = decoration_offset + decoration.len;
183
184 if run_end <= split_point {
185 left_decorations.push(decoration.clone());
186 } else if decoration_offset >= split_point {
187 right_decorations.push(decoration.clone());
188 } else {
189 let left_len = split_point - decoration_offset;
190 let right_len = run_end - split_point;
191 left_decorations.push(DecorationRun {
192 len: left_len,
193 color: decoration.color,
194 background_color: decoration.background_color,
195 underline: decoration.underline,
196 strikethrough: decoration.strikethrough,
197 });
198 right_decorations.push(DecorationRun {
199 len: right_len,
200 color: decoration.color,
201 background_color: decoration.background_color,
202 underline: decoration.underline,
203 strikethrough: decoration.strikethrough,
204 });
205 }
206
207 decoration_offset = run_end;
208 }
209
210 // Split text
211 let left_text = SharedString::new(self.text[..byte_index].to_string());
212 let right_text = SharedString::new(self.text[byte_index..].to_string());
213
214 let left_width = x_offset;
215 let right_width = self.layout.width - left_width;
216
217 let left = ShapedLine {
218 layout: Arc::new(LineLayout {
219 font_size: self.layout.font_size,
220 width: left_width,
221 ascent: self.layout.ascent,
222 descent: self.layout.descent,
223 runs: left_runs,
224 len: byte_index,
225 }),
226 text: left_text,
227 decoration_runs: left_decorations,
228 };
229
230 let right = ShapedLine {
231 layout: Arc::new(LineLayout {
232 font_size: self.layout.font_size,
233 width: right_width,
234 ascent: self.layout.ascent,
235 descent: self.layout.descent,
236 runs: right_runs,
237 len: self.layout.len - byte_index,
238 }),
239 text: right_text,
240 decoration_runs: right_decorations,
241 };
242
243 (left, right)
244 }
245}
246
247/// A line of text that has been shaped, decorated, and wrapped by the text layout system.
248#[derive(Default, Debug, Deref, DerefMut)]
249pub struct WrappedLine {
250 #[deref]
251 #[deref_mut]
252 pub(crate) layout: Arc<WrappedLineLayout>,
253 /// The text that was shaped for this line.
254 pub text: SharedString,
255 pub(crate) decoration_runs: Vec<DecorationRun>,
256}
257
258impl WrappedLine {
259 /// The length of the underlying, unwrapped layout, in utf-8 bytes.
260 #[allow(clippy::len_without_is_empty)]
261 pub fn len(&self) -> usize {
262 self.layout.len()
263 }
264
265 /// Paint this line of text to the window.
266 pub fn paint(
267 &self,
268 origin: Point<Pixels>,
269 line_height: Pixels,
270 align: TextAlign,
271 bounds: Option<Bounds<Pixels>>,
272 window: &mut Window,
273 cx: &mut App,
274 ) -> Result<()> {
275 let align_width = match bounds {
276 Some(bounds) => Some(bounds.size.width),
277 None => self.layout.wrap_width,
278 };
279
280 paint_line(
281 origin,
282 &self.layout.unwrapped_layout,
283 line_height,
284 align,
285 align_width,
286 &self.decoration_runs,
287 &self.wrap_boundaries,
288 window,
289 cx,
290 )?;
291
292 Ok(())
293 }
294
295 /// Paint the background of line of text to the window.
296 pub fn paint_background(
297 &self,
298 origin: Point<Pixels>,
299 line_height: Pixels,
300 align: TextAlign,
301 bounds: Option<Bounds<Pixels>>,
302 window: &mut Window,
303 cx: &mut App,
304 ) -> Result<()> {
305 let align_width = match bounds {
306 Some(bounds) => Some(bounds.size.width),
307 None => self.layout.wrap_width,
308 };
309
310 paint_line_background(
311 origin,
312 &self.layout.unwrapped_layout,
313 line_height,
314 align,
315 align_width,
316 &self.decoration_runs,
317 &self.wrap_boundaries,
318 window,
319 cx,
320 )?;
321
322 Ok(())
323 }
324}
325
326fn paint_line(
327 origin: Point<Pixels>,
328 layout: &LineLayout,
329 line_height: Pixels,
330 align: TextAlign,
331 align_width: Option<Pixels>,
332 decoration_runs: &[DecorationRun],
333 wrap_boundaries: &[WrapBoundary],
334 window: &mut Window,
335 cx: &mut App,
336) -> Result<()> {
337 let line_bounds = Bounds::new(
338 origin,
339 size(
340 layout.width,
341 line_height * (wrap_boundaries.len() as f32 + 1.),
342 ),
343 );
344 window.paint_layer(line_bounds, |window| {
345 let padding_top = (line_height - layout.ascent - layout.descent) / 2.;
346 let baseline_offset = point(px(0.), padding_top + layout.ascent);
347 let mut decoration_runs = decoration_runs.iter();
348 let mut wraps = wrap_boundaries.iter().peekable();
349 let mut run_end = 0;
350 let mut color = black();
351 let mut current_underline: Option<(Point<Pixels>, UnderlineStyle)> = None;
352 let mut current_strikethrough: Option<(Point<Pixels>, StrikethroughStyle)> = None;
353 let text_system = cx.text_system().clone();
354 let mut glyph_origin = point(
355 aligned_origin_x(
356 origin,
357 align_width.unwrap_or(layout.width),
358 px(0.0),
359 &align,
360 layout,
361 wraps.peek(),
362 ),
363 origin.y,
364 );
365 let mut prev_glyph_position = Point::default();
366 let mut max_glyph_size = size(px(0.), px(0.));
367 let mut first_glyph_x = origin.x;
368 for (run_ix, run) in layout.runs.iter().enumerate() {
369 max_glyph_size = text_system.bounding_box(run.font_id, layout.font_size).size;
370
371 for (glyph_ix, glyph) in run.glyphs.iter().enumerate() {
372 glyph_origin.x += glyph.position.x - prev_glyph_position.x;
373 if glyph_ix == 0 && run_ix == 0 {
374 first_glyph_x = glyph_origin.x;
375 }
376
377 if wraps.peek() == Some(&&WrapBoundary { run_ix, glyph_ix }) {
378 wraps.next();
379 if let Some((underline_origin, underline_style)) = current_underline.as_mut() {
380 if glyph_origin.x == underline_origin.x {
381 underline_origin.x -= max_glyph_size.width.half();
382 };
383 window.paint_underline(
384 *underline_origin,
385 glyph_origin.x - underline_origin.x,
386 underline_style,
387 );
388 underline_origin.x = origin.x;
389 underline_origin.y += line_height;
390 }
391 if let Some((strikethrough_origin, strikethrough_style)) =
392 current_strikethrough.as_mut()
393 {
394 if glyph_origin.x == strikethrough_origin.x {
395 strikethrough_origin.x -= max_glyph_size.width.half();
396 };
397 window.paint_strikethrough(
398 *strikethrough_origin,
399 glyph_origin.x - strikethrough_origin.x,
400 strikethrough_style,
401 );
402 strikethrough_origin.x = origin.x;
403 strikethrough_origin.y += line_height;
404 }
405
406 glyph_origin.x = aligned_origin_x(
407 origin,
408 align_width.unwrap_or(layout.width),
409 glyph.position.x,
410 &align,
411 layout,
412 wraps.peek(),
413 );
414 glyph_origin.y += line_height;
415 }
416 prev_glyph_position = glyph.position;
417
418 let mut finished_underline: Option<(Point<Pixels>, UnderlineStyle)> = None;
419 let mut finished_strikethrough: Option<(Point<Pixels>, StrikethroughStyle)> = None;
420 if glyph.index >= run_end {
421 let mut style_run = decoration_runs.next();
422
423 // ignore style runs that apply to a partial glyph
424 while let Some(run) = style_run {
425 if glyph.index < run_end + (run.len as usize) {
426 break;
427 }
428 run_end += run.len as usize;
429 style_run = decoration_runs.next();
430 }
431
432 if let Some(style_run) = style_run {
433 if let Some((_, underline_style)) = &mut current_underline
434 && style_run.underline.as_ref() != Some(underline_style)
435 {
436 finished_underline = current_underline.take();
437 }
438 if let Some(run_underline) = style_run.underline.as_ref() {
439 current_underline.get_or_insert((
440 point(
441 glyph_origin.x,
442 glyph_origin.y + baseline_offset.y + (layout.descent * 0.618),
443 ),
444 UnderlineStyle {
445 color: Some(run_underline.color.unwrap_or(style_run.color)),
446 thickness: run_underline.thickness,
447 wavy: run_underline.wavy,
448 },
449 ));
450 }
451 if let Some((_, strikethrough_style)) = &mut current_strikethrough
452 && style_run.strikethrough.as_ref() != Some(strikethrough_style)
453 {
454 finished_strikethrough = current_strikethrough.take();
455 }
456 if let Some(run_strikethrough) = style_run.strikethrough.as_ref() {
457 current_strikethrough.get_or_insert((
458 point(
459 glyph_origin.x,
460 glyph_origin.y
461 + (((layout.ascent * 0.5) + baseline_offset.y) * 0.5),
462 ),
463 StrikethroughStyle {
464 color: Some(run_strikethrough.color.unwrap_or(style_run.color)),
465 thickness: run_strikethrough.thickness,
466 },
467 ));
468 }
469
470 run_end += style_run.len as usize;
471 color = style_run.color;
472 } else {
473 run_end = layout.len;
474 finished_underline = current_underline.take();
475 finished_strikethrough = current_strikethrough.take();
476 }
477 }
478
479 if let Some((mut underline_origin, underline_style)) = finished_underline {
480 if underline_origin.x == glyph_origin.x {
481 underline_origin.x -= max_glyph_size.width.half();
482 };
483 window.paint_underline(
484 underline_origin,
485 glyph_origin.x - underline_origin.x,
486 &underline_style,
487 );
488 }
489
490 if let Some((mut strikethrough_origin, strikethrough_style)) =
491 finished_strikethrough
492 {
493 if strikethrough_origin.x == glyph_origin.x {
494 strikethrough_origin.x -= max_glyph_size.width.half();
495 };
496 window.paint_strikethrough(
497 strikethrough_origin,
498 glyph_origin.x - strikethrough_origin.x,
499 &strikethrough_style,
500 );
501 }
502
503 let max_glyph_bounds = Bounds {
504 origin: glyph_origin,
505 size: max_glyph_size,
506 };
507
508 let content_mask = window.content_mask();
509 if max_glyph_bounds.intersects(&content_mask.bounds) {
510 let vertical_offset = point(px(0.0), glyph.position.y);
511 if glyph.is_emoji {
512 window.paint_emoji(
513 glyph_origin + baseline_offset + vertical_offset,
514 run.font_id,
515 glyph.id,
516 layout.font_size,
517 )?;
518 } else {
519 window.paint_glyph(
520 glyph_origin + baseline_offset + vertical_offset,
521 run.font_id,
522 glyph.id,
523 layout.font_size,
524 color,
525 )?;
526 }
527 }
528 }
529 }
530
531 let mut last_line_end_x = first_glyph_x + layout.width;
532 if let Some(boundary) = wrap_boundaries.last() {
533 let run = &layout.runs[boundary.run_ix];
534 let glyph = &run.glyphs[boundary.glyph_ix];
535 last_line_end_x -= glyph.position.x;
536 }
537
538 if let Some((mut underline_start, underline_style)) = current_underline.take() {
539 if last_line_end_x == underline_start.x {
540 underline_start.x -= max_glyph_size.width.half()
541 };
542 window.paint_underline(
543 underline_start,
544 last_line_end_x - underline_start.x,
545 &underline_style,
546 );
547 }
548
549 if let Some((mut strikethrough_start, strikethrough_style)) = current_strikethrough.take() {
550 if last_line_end_x == strikethrough_start.x {
551 strikethrough_start.x -= max_glyph_size.width.half()
552 };
553 window.paint_strikethrough(
554 strikethrough_start,
555 last_line_end_x - strikethrough_start.x,
556 &strikethrough_style,
557 );
558 }
559
560 Ok(())
561 })
562}
563
564fn paint_line_background(
565 origin: Point<Pixels>,
566 layout: &LineLayout,
567 line_height: Pixels,
568 align: TextAlign,
569 align_width: Option<Pixels>,
570 decoration_runs: &[DecorationRun],
571 wrap_boundaries: &[WrapBoundary],
572 window: &mut Window,
573 cx: &mut App,
574) -> Result<()> {
575 let line_bounds = Bounds::new(
576 origin,
577 size(
578 layout.width,
579 line_height * (wrap_boundaries.len() as f32 + 1.),
580 ),
581 );
582 window.paint_layer(line_bounds, |window| {
583 let mut decoration_runs = decoration_runs.iter();
584 let mut wraps = wrap_boundaries.iter().peekable();
585 let mut run_end = 0;
586 let mut current_background: Option<(Point<Pixels>, Hsla)> = None;
587 let text_system = cx.text_system().clone();
588 let mut glyph_origin = point(
589 aligned_origin_x(
590 origin,
591 align_width.unwrap_or(layout.width),
592 px(0.0),
593 &align,
594 layout,
595 wraps.peek(),
596 ),
597 origin.y,
598 );
599 let mut prev_glyph_position = Point::default();
600 let mut max_glyph_size = size(px(0.), px(0.));
601 for (run_ix, run) in layout.runs.iter().enumerate() {
602 max_glyph_size = text_system.bounding_box(run.font_id, layout.font_size).size;
603
604 for (glyph_ix, glyph) in run.glyphs.iter().enumerate() {
605 glyph_origin.x += glyph.position.x - prev_glyph_position.x;
606
607 if wraps.peek() == Some(&&WrapBoundary { run_ix, glyph_ix }) {
608 wraps.next();
609 if let Some((background_origin, background_color)) = current_background.as_mut()
610 {
611 if glyph_origin.x == background_origin.x {
612 background_origin.x -= max_glyph_size.width.half()
613 }
614 window.paint_quad(fill(
615 Bounds {
616 origin: *background_origin,
617 size: size(glyph_origin.x - background_origin.x, line_height),
618 },
619 *background_color,
620 ));
621 background_origin.x = origin.x;
622 background_origin.y += line_height;
623 }
624
625 glyph_origin.x = aligned_origin_x(
626 origin,
627 align_width.unwrap_or(layout.width),
628 glyph.position.x,
629 &align,
630 layout,
631 wraps.peek(),
632 );
633 glyph_origin.y += line_height;
634 }
635 prev_glyph_position = glyph.position;
636
637 let mut finished_background: Option<(Point<Pixels>, Hsla)> = None;
638 if glyph.index >= run_end {
639 let mut style_run = decoration_runs.next();
640
641 // ignore style runs that apply to a partial glyph
642 while let Some(run) = style_run {
643 if glyph.index < run_end + (run.len as usize) {
644 break;
645 }
646 run_end += run.len as usize;
647 style_run = decoration_runs.next();
648 }
649
650 if let Some(style_run) = style_run {
651 if let Some((_, background_color)) = &mut current_background
652 && style_run.background_color.as_ref() != Some(background_color)
653 {
654 finished_background = current_background.take();
655 }
656 if let Some(run_background) = style_run.background_color {
657 current_background.get_or_insert((
658 point(glyph_origin.x, glyph_origin.y),
659 run_background,
660 ));
661 }
662 run_end += style_run.len as usize;
663 } else {
664 run_end = layout.len;
665 finished_background = current_background.take();
666 }
667 }
668
669 if let Some((mut background_origin, background_color)) = finished_background {
670 let mut width = glyph_origin.x - background_origin.x;
671 if background_origin.x == glyph_origin.x {
672 background_origin.x -= max_glyph_size.width.half();
673 };
674 window.paint_quad(fill(
675 Bounds {
676 origin: background_origin,
677 size: size(width, line_height),
678 },
679 background_color,
680 ));
681 }
682 }
683 }
684
685 let mut last_line_end_x = origin.x + layout.width;
686 if let Some(boundary) = wrap_boundaries.last() {
687 let run = &layout.runs[boundary.run_ix];
688 let glyph = &run.glyphs[boundary.glyph_ix];
689 last_line_end_x -= glyph.position.x;
690 }
691
692 if let Some((mut background_origin, background_color)) = current_background.take() {
693 if last_line_end_x == background_origin.x {
694 background_origin.x -= max_glyph_size.width.half()
695 };
696 window.paint_quad(fill(
697 Bounds {
698 origin: background_origin,
699 size: size(last_line_end_x - background_origin.x, line_height),
700 },
701 background_color,
702 ));
703 }
704
705 Ok(())
706 })
707}
708
709fn aligned_origin_x(
710 origin: Point<Pixels>,
711 align_width: Pixels,
712 last_glyph_x: Pixels,
713 align: &TextAlign,
714 layout: &LineLayout,
715 wrap_boundary: Option<&&WrapBoundary>,
716) -> Pixels {
717 let end_of_line = if let Some(WrapBoundary { run_ix, glyph_ix }) = wrap_boundary {
718 layout.runs[*run_ix].glyphs[*glyph_ix].position.x
719 } else {
720 layout.width
721 };
722
723 let line_width = end_of_line - last_glyph_x;
724
725 match align {
726 TextAlign::Left => origin.x,
727 TextAlign::Center => (origin.x * 2.0 + align_width - line_width) / 2.0,
728 TextAlign::Right => origin.x + align_width - line_width,
729 }
730}
731
732#[cfg(test)]
733mod tests {
734 use super::*;
735 use crate::{FontId, GlyphId};
736
737 /// Helper: build a ShapedLine from glyph descriptors without the platform text system.
738 /// Each glyph is described as (byte_index, x_position).
739 fn make_shaped_line(
740 text: &str,
741 glyphs: &[(usize, f32)],
742 width: f32,
743 decorations: &[DecorationRun],
744 ) -> ShapedLine {
745 let shaped_glyphs: Vec<ShapedGlyph> = glyphs
746 .iter()
747 .map(|&(index, x)| ShapedGlyph {
748 id: GlyphId(0),
749 position: point(px(x), px(0.0)),
750 index,
751 is_emoji: false,
752 })
753 .collect();
754
755 ShapedLine {
756 layout: Arc::new(LineLayout {
757 font_size: px(16.0),
758 width: px(width),
759 ascent: px(12.0),
760 descent: px(4.0),
761 runs: vec![ShapedRun {
762 font_id: FontId(0),
763 glyphs: shaped_glyphs,
764 }],
765 len: text.len(),
766 }),
767 text: SharedString::new(text.to_string()),
768 decoration_runs: SmallVec::from(decorations.to_vec()),
769 }
770 }
771
772 #[test]
773 fn test_split_at_invariants() {
774 // Split "abcdef" at every possible byte index and verify structural invariants.
775 let line = make_shaped_line(
776 "abcdef",
777 &[
778 (0, 0.0),
779 (1, 10.0),
780 (2, 20.0),
781 (3, 30.0),
782 (4, 40.0),
783 (5, 50.0),
784 ],
785 60.0,
786 &[],
787 );
788
789 for i in 0..=6 {
790 let (left, right) = line.split_at(i);
791
792 assert_eq!(
793 left.width() + right.width(),
794 line.width(),
795 "widths must sum at split={i}"
796 );
797 assert_eq!(
798 left.len() + right.len(),
799 line.len(),
800 "lengths must sum at split={i}"
801 );
802 assert_eq!(
803 format!("{}{}", left.text.as_ref(), right.text.as_ref()),
804 "abcdef",
805 "text must concatenate at split={i}"
806 );
807 assert_eq!(left.font_size, line.font_size, "font_size at split={i}");
808 assert_eq!(right.ascent, line.ascent, "ascent at split={i}");
809 assert_eq!(right.descent, line.descent, "descent at split={i}");
810 }
811
812 // Edge: split at 0 produces no left runs, full content on right
813 let (left, right) = line.split_at(0);
814 assert_eq!(left.runs.len(), 0);
815 assert_eq!(right.runs[0].glyphs.len(), 6);
816
817 // Edge: split at end produces full content on left, no right runs
818 let (left, right) = line.split_at(6);
819 assert_eq!(left.runs[0].glyphs.len(), 6);
820 assert_eq!(right.runs.len(), 0);
821 }
822
823 #[test]
824 fn test_split_at_glyph_rebasing() {
825 // Two font runs (simulating a font fallback boundary at byte 3):
826 // run A (FontId 0): glyphs at bytes 0,1,2 positions 0,10,20
827 // run B (FontId 1): glyphs at bytes 3,4,5 positions 30,40,50
828 // Successive splits simulate the incremental splitting done during wrap.
829 let line = ShapedLine {
830 layout: Arc::new(LineLayout {
831 font_size: px(16.0),
832 width: px(60.0),
833 ascent: px(12.0),
834 descent: px(4.0),
835 runs: vec![
836 ShapedRun {
837 font_id: FontId(0),
838 glyphs: vec![
839 ShapedGlyph {
840 id: GlyphId(0),
841 position: point(px(0.0), px(0.0)),
842 index: 0,
843 is_emoji: false,
844 },
845 ShapedGlyph {
846 id: GlyphId(0),
847 position: point(px(10.0), px(0.0)),
848 index: 1,
849 is_emoji: false,
850 },
851 ShapedGlyph {
852 id: GlyphId(0),
853 position: point(px(20.0), px(0.0)),
854 index: 2,
855 is_emoji: false,
856 },
857 ],
858 },
859 ShapedRun {
860 font_id: FontId(1),
861 glyphs: vec![
862 ShapedGlyph {
863 id: GlyphId(0),
864 position: point(px(30.0), px(0.0)),
865 index: 3,
866 is_emoji: false,
867 },
868 ShapedGlyph {
869 id: GlyphId(0),
870 position: point(px(40.0), px(0.0)),
871 index: 4,
872 is_emoji: false,
873 },
874 ShapedGlyph {
875 id: GlyphId(0),
876 position: point(px(50.0), px(0.0)),
877 index: 5,
878 is_emoji: false,
879 },
880 ],
881 },
882 ],
883 len: 6,
884 }),
885 text: "abcdef".into(),
886 decoration_runs: SmallVec::new(),
887 };
888
889 // First split at byte 2 — mid-run in run A
890 let (first, remainder) = line.split_at(2);
891 assert_eq!(first.text.as_ref(), "ab");
892 assert_eq!(first.runs.len(), 1);
893 assert_eq!(first.runs[0].font_id, FontId(0));
894
895 // Remainder "cdef" should have two runs: tail of A (1 glyph) + all of B (3 glyphs)
896 assert_eq!(remainder.text.as_ref(), "cdef");
897 assert_eq!(remainder.runs.len(), 2);
898 assert_eq!(remainder.runs[0].font_id, FontId(0));
899 assert_eq!(remainder.runs[0].glyphs.len(), 1);
900 assert_eq!(remainder.runs[0].glyphs[0].index, 0);
901 assert_eq!(remainder.runs[0].glyphs[0].position.x, px(0.0));
902 assert_eq!(remainder.runs[1].font_id, FontId(1));
903 assert_eq!(remainder.runs[1].glyphs[0].index, 1);
904 assert_eq!(remainder.runs[1].glyphs[0].position.x, px(10.0));
905
906 // Second split at byte 2 within remainder — crosses the run boundary
907 let (second, final_part) = remainder.split_at(2);
908 assert_eq!(second.text.as_ref(), "cd");
909 assert_eq!(final_part.text.as_ref(), "ef");
910 assert_eq!(final_part.runs[0].glyphs[0].index, 0);
911 assert_eq!(final_part.runs[0].glyphs[0].position.x, px(0.0));
912
913 // Widths must sum across all three pieces
914 assert_eq!(
915 first.width() + second.width() + final_part.width(),
916 line.width()
917 );
918 }
919
920 #[test]
921 fn test_split_at_decorations() {
922 // Three decoration runs: red [0..2), green [2..5), blue [5..6).
923 // Split at byte 3 — red goes entirely left, green straddles, blue goes entirely right.
924 let red = Hsla {
925 h: 0.0,
926 s: 1.0,
927 l: 0.5,
928 a: 1.0,
929 };
930 let green = Hsla {
931 h: 0.3,
932 s: 1.0,
933 l: 0.5,
934 a: 1.0,
935 };
936 let blue = Hsla {
937 h: 0.6,
938 s: 1.0,
939 l: 0.5,
940 a: 1.0,
941 };
942
943 let line = make_shaped_line(
944 "abcdef",
945 &[
946 (0, 0.0),
947 (1, 10.0),
948 (2, 20.0),
949 (3, 30.0),
950 (4, 40.0),
951 (5, 50.0),
952 ],
953 60.0,
954 &[
955 DecorationRun {
956 len: 2,
957 color: red,
958 background_color: None,
959 underline: None,
960 strikethrough: None,
961 },
962 DecorationRun {
963 len: 3,
964 color: green,
965 background_color: None,
966 underline: None,
967 strikethrough: None,
968 },
969 DecorationRun {
970 len: 1,
971 color: blue,
972 background_color: None,
973 underline: None,
974 strikethrough: None,
975 },
976 ],
977 );
978
979 let (left, right) = line.split_at(3);
980
981 // Left: red(2) + green(1) — green straddled, left portion has len 1
982 assert_eq!(left.decoration_runs.len(), 2);
983 assert_eq!(left.decoration_runs[0].len, 2);
984 assert_eq!(left.decoration_runs[0].color, red);
985 assert_eq!(left.decoration_runs[1].len, 1);
986 assert_eq!(left.decoration_runs[1].color, green);
987
988 // Right: green(2) + blue(1) — green straddled, right portion has len 2
989 assert_eq!(right.decoration_runs.len(), 2);
990 assert_eq!(right.decoration_runs[0].len, 2);
991 assert_eq!(right.decoration_runs[0].color, green);
992 assert_eq!(right.decoration_runs[1].len, 1);
993 assert_eq!(right.decoration_runs[1].color, blue);
994 }
995}