1use crate::{
2 AbsoluteLength, App, Bounds, DefiniteLength, Edges, Length, Pixels, Point, Size, Style, Window,
3 point, size,
4};
5use collections::{FxHashMap, FxHashSet};
6use smallvec::SmallVec;
7use stacksafe::{StackSafe, stacksafe};
8use std::{fmt::Debug, ops::Range};
9use taffy::{
10 TaffyTree, TraversePartialTree as _,
11 geometry::{Point as TaffyPoint, Rect as TaffyRect, Size as TaffySize},
12 style::AvailableSpace as TaffyAvailableSpace,
13 tree::NodeId,
14};
15
16type NodeMeasureFn = StackSafe<
17 Box<
18 dyn FnMut(
19 Size<Option<Pixels>>,
20 Size<AvailableSpace>,
21 &mut Window,
22 &mut App,
23 ) -> Size<Pixels>,
24 >,
25>;
26
27struct NodeContext {
28 measure: NodeMeasureFn,
29}
30pub struct TaffyLayoutEngine {
31 taffy: TaffyTree<NodeContext>,
32 absolute_layout_bounds: FxHashMap<LayoutId, Bounds<Pixels>>,
33 computed_layouts: FxHashSet<LayoutId>,
34}
35
36const EXPECT_MESSAGE: &str = "we should avoid taffy layout errors by construction if possible";
37
38impl TaffyLayoutEngine {
39 pub fn new() -> Self {
40 let mut taffy = TaffyTree::new();
41 taffy.enable_rounding();
42 TaffyLayoutEngine {
43 taffy,
44 absolute_layout_bounds: FxHashMap::default(),
45 computed_layouts: FxHashSet::default(),
46 }
47 }
48
49 pub fn clear(&mut self) {
50 self.taffy.clear();
51 self.absolute_layout_bounds.clear();
52 self.computed_layouts.clear();
53 }
54
55 pub fn request_layout(
56 &mut self,
57 style: Style,
58 rem_size: Pixels,
59 scale_factor: f32,
60 children: &[LayoutId],
61 ) -> LayoutId {
62 let taffy_style = style.to_taffy(rem_size, scale_factor);
63
64 if children.is_empty() {
65 self.taffy
66 .new_leaf(taffy_style)
67 .expect(EXPECT_MESSAGE)
68 .into()
69 } else {
70 self.taffy
71 // This is safe because LayoutId is repr(transparent) to taffy::tree::NodeId.
72 .new_with_children(taffy_style, unsafe {
73 std::mem::transmute::<&[LayoutId], &[taffy::NodeId]>(children)
74 })
75 .expect(EXPECT_MESSAGE)
76 .into()
77 }
78 }
79
80 pub fn request_measured_layout(
81 &mut self,
82 style: Style,
83 rem_size: Pixels,
84 scale_factor: f32,
85 measure: impl FnMut(
86 Size<Option<Pixels>>,
87 Size<AvailableSpace>,
88 &mut Window,
89 &mut App,
90 ) -> Size<Pixels>
91 + 'static,
92 ) -> LayoutId {
93 let taffy_style = style.to_taffy(rem_size, scale_factor);
94
95 self.taffy
96 .new_leaf_with_context(
97 taffy_style,
98 NodeContext {
99 measure: StackSafe::new(Box::new(measure)),
100 },
101 )
102 .expect(EXPECT_MESSAGE)
103 .into()
104 }
105
106 // Used to understand performance
107 #[allow(dead_code)]
108 fn count_all_children(&self, parent: LayoutId) -> anyhow::Result<u32> {
109 let mut count = 0;
110
111 for child in self.taffy.children(parent.0)? {
112 // Count this child.
113 count += 1;
114
115 // Count all of this child's children.
116 count += self.count_all_children(LayoutId(child))?
117 }
118
119 Ok(count)
120 }
121
122 // Used to understand performance
123 #[allow(dead_code)]
124 fn max_depth(&self, depth: u32, parent: LayoutId) -> anyhow::Result<u32> {
125 println!(
126 "{parent:?} at depth {depth} has {} children",
127 self.taffy.child_count(parent.0)
128 );
129
130 let mut max_child_depth = 0;
131
132 for child in self.taffy.children(parent.0)? {
133 max_child_depth = std::cmp::max(max_child_depth, self.max_depth(0, LayoutId(child))?);
134 }
135
136 Ok(depth + 1 + max_child_depth)
137 }
138
139 // Used to understand performance
140 #[allow(dead_code)]
141 fn get_edges(&self, parent: LayoutId) -> anyhow::Result<Vec<(LayoutId, LayoutId)>> {
142 let mut edges = Vec::new();
143
144 for child in self.taffy.children(parent.0)? {
145 edges.push((parent, LayoutId(child)));
146
147 edges.extend(self.get_edges(LayoutId(child))?);
148 }
149
150 Ok(edges)
151 }
152
153 #[stacksafe]
154 pub fn compute_layout(
155 &mut self,
156 id: LayoutId,
157 available_space: Size<AvailableSpace>,
158 window: &mut Window,
159 cx: &mut App,
160 ) {
161 // Leaving this here until we have a better instrumentation approach.
162 // println!("Laying out {} children", self.count_all_children(id)?);
163 // println!("Max layout depth: {}", self.max_depth(0, id)?);
164
165 // Output the edges (branches) of the tree in Mermaid format for visualization.
166 // println!("Edges:");
167 // for (a, b) in self.get_edges(id)? {
168 // println!("N{} --> N{}", u64::from(a), u64::from(b));
169 // }
170 //
171
172 if !self.computed_layouts.insert(id) {
173 let mut stack = SmallVec::<[LayoutId; 64]>::new();
174 stack.push(id);
175 while let Some(id) = stack.pop() {
176 self.absolute_layout_bounds.remove(&id);
177 stack.extend(
178 self.taffy
179 .children(id.into())
180 .expect(EXPECT_MESSAGE)
181 .into_iter()
182 .map(Into::into),
183 );
184 }
185 }
186
187 let scale_factor = window.scale_factor();
188
189 let transform = |v: AvailableSpace| match v {
190 AvailableSpace::Definite(pixels) => {
191 AvailableSpace::Definite(Pixels(pixels.0 * scale_factor))
192 }
193 AvailableSpace::MinContent => AvailableSpace::MinContent,
194 AvailableSpace::MaxContent => AvailableSpace::MaxContent,
195 };
196 let available_space = size(
197 transform(available_space.width),
198 transform(available_space.height),
199 );
200
201 self.taffy
202 .compute_layout_with_measure(
203 id.into(),
204 available_space.into(),
205 |known_dimensions, available_space, _id, node_context, _style| {
206 let Some(node_context) = node_context else {
207 return taffy::geometry::Size::default();
208 };
209
210 let known_dimensions = Size {
211 width: known_dimensions.width.map(|e| Pixels(e / scale_factor)),
212 height: known_dimensions.height.map(|e| Pixels(e / scale_factor)),
213 };
214
215 let available_space: Size<AvailableSpace> = available_space.into();
216 let untransform = |ev: AvailableSpace| match ev {
217 AvailableSpace::Definite(pixels) => {
218 AvailableSpace::Definite(Pixels(pixels.0 / scale_factor))
219 }
220 AvailableSpace::MinContent => AvailableSpace::MinContent,
221 AvailableSpace::MaxContent => AvailableSpace::MaxContent,
222 };
223 let available_space = size(
224 untransform(available_space.width),
225 untransform(available_space.height),
226 );
227
228 let a: Size<Pixels> =
229 (node_context.measure)(known_dimensions, available_space, window, cx);
230 size(a.width.0 * scale_factor, a.height.0 * scale_factor).into()
231 },
232 )
233 .expect(EXPECT_MESSAGE);
234 }
235
236 pub fn layout_bounds(&mut self, id: LayoutId, scale_factor: f32) -> Bounds<Pixels> {
237 if let Some(layout) = self.absolute_layout_bounds.get(&id).cloned() {
238 return layout;
239 }
240
241 let layout = self.taffy.layout(id.into()).expect(EXPECT_MESSAGE);
242 let mut bounds = Bounds {
243 origin: point(
244 Pixels(layout.location.x / scale_factor),
245 Pixels(layout.location.y / scale_factor),
246 ),
247 size: size(
248 Pixels(layout.size.width / scale_factor),
249 Pixels(layout.size.height / scale_factor),
250 ),
251 };
252
253 if let Some(parent_id) = self.taffy.parent(id.0) {
254 let parent_bounds = self.layout_bounds(parent_id.into(), scale_factor);
255 bounds.origin += parent_bounds.origin;
256 }
257 self.absolute_layout_bounds.insert(id, bounds);
258
259 bounds
260 }
261}
262
263/// A unique identifier for a layout node, generated when requesting a layout from Taffy
264#[derive(Copy, Clone, Eq, PartialEq, Debug)]
265#[repr(transparent)]
266pub struct LayoutId(NodeId);
267
268impl std::hash::Hash for LayoutId {
269 fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
270 u64::from(self.0).hash(state);
271 }
272}
273
274impl From<NodeId> for LayoutId {
275 fn from(node_id: NodeId) -> Self {
276 Self(node_id)
277 }
278}
279
280impl From<LayoutId> for NodeId {
281 fn from(layout_id: LayoutId) -> NodeId {
282 layout_id.0
283 }
284}
285
286trait ToTaffy<Output> {
287 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> Output;
288}
289
290impl ToTaffy<taffy::style::Style> for Style {
291 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> taffy::style::Style {
292 use taffy::style_helpers::{fr, length, minmax, repeat};
293
294 fn to_grid_line(
295 placement: &Range<crate::GridPlacement>,
296 ) -> taffy::Line<taffy::GridPlacement> {
297 taffy::Line {
298 start: placement.start.into(),
299 end: placement.end.into(),
300 }
301 }
302
303 fn to_grid_repeat<T: taffy::style::CheapCloneStr>(
304 unit: &Option<u16>,
305 ) -> Vec<taffy::GridTemplateComponent<T>> {
306 // grid-template-columns: repeat(<number>, minmax(0, 1fr));
307 unit.map(|count| vec![repeat(count, vec![minmax(length(0.0), fr(1.0))])])
308 .unwrap_or_default()
309 }
310
311 taffy::style::Style {
312 display: self.display.into(),
313 overflow: self.overflow.into(),
314 scrollbar_width: self.scrollbar_width.to_taffy(rem_size, scale_factor),
315 position: self.position.into(),
316 inset: self.inset.to_taffy(rem_size, scale_factor),
317 size: self.size.to_taffy(rem_size, scale_factor),
318 min_size: self.min_size.to_taffy(rem_size, scale_factor),
319 max_size: self.max_size.to_taffy(rem_size, scale_factor),
320 aspect_ratio: self.aspect_ratio,
321 margin: self.margin.to_taffy(rem_size, scale_factor),
322 padding: self.padding.to_taffy(rem_size, scale_factor),
323 border: self.border_widths.to_taffy(rem_size, scale_factor),
324 align_items: self.align_items.map(|x| x.into()),
325 align_self: self.align_self.map(|x| x.into()),
326 align_content: self.align_content.map(|x| x.into()),
327 justify_content: self.justify_content.map(|x| x.into()),
328 gap: self.gap.to_taffy(rem_size, scale_factor),
329 flex_direction: self.flex_direction.into(),
330 flex_wrap: self.flex_wrap.into(),
331 flex_basis: self.flex_basis.to_taffy(rem_size, scale_factor),
332 flex_grow: self.flex_grow,
333 flex_shrink: self.flex_shrink,
334 grid_template_rows: to_grid_repeat(&self.grid_rows),
335 grid_template_columns: to_grid_repeat(&self.grid_cols),
336 grid_row: self
337 .grid_location
338 .as_ref()
339 .map(|location| to_grid_line(&location.row))
340 .unwrap_or_default(),
341 grid_column: self
342 .grid_location
343 .as_ref()
344 .map(|location| to_grid_line(&location.column))
345 .unwrap_or_default(),
346 ..Default::default()
347 }
348 }
349}
350
351impl ToTaffy<f32> for AbsoluteLength {
352 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> f32 {
353 match self {
354 AbsoluteLength::Pixels(pixels) => {
355 let pixels: f32 = pixels.into();
356 pixels * scale_factor
357 }
358 AbsoluteLength::Rems(rems) => {
359 let pixels: f32 = (*rems * rem_size).into();
360 pixels * scale_factor
361 }
362 }
363 }
364}
365
366impl ToTaffy<taffy::style::LengthPercentageAuto> for Length {
367 fn to_taffy(
368 &self,
369 rem_size: Pixels,
370 scale_factor: f32,
371 ) -> taffy::prelude::LengthPercentageAuto {
372 match self {
373 Length::Definite(length) => length.to_taffy(rem_size, scale_factor),
374 Length::Auto => taffy::prelude::LengthPercentageAuto::auto(),
375 }
376 }
377}
378
379impl ToTaffy<taffy::style::Dimension> for Length {
380 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> taffy::prelude::Dimension {
381 match self {
382 Length::Definite(length) => length.to_taffy(rem_size, scale_factor),
383 Length::Auto => taffy::prelude::Dimension::auto(),
384 }
385 }
386}
387
388impl ToTaffy<taffy::style::LengthPercentage> for DefiniteLength {
389 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> taffy::style::LengthPercentage {
390 match self {
391 DefiniteLength::Absolute(length) => match length {
392 AbsoluteLength::Pixels(pixels) => {
393 let pixels: f32 = pixels.into();
394 taffy::style::LengthPercentage::length(pixels * scale_factor)
395 }
396 AbsoluteLength::Rems(rems) => {
397 let pixels: f32 = (*rems * rem_size).into();
398 taffy::style::LengthPercentage::length(pixels * scale_factor)
399 }
400 },
401 DefiniteLength::Fraction(fraction) => {
402 taffy::style::LengthPercentage::percent(*fraction)
403 }
404 }
405 }
406}
407
408impl ToTaffy<taffy::style::LengthPercentageAuto> for DefiniteLength {
409 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> taffy::style::LengthPercentageAuto {
410 match self {
411 DefiniteLength::Absolute(length) => match length {
412 AbsoluteLength::Pixels(pixels) => {
413 let pixels: f32 = pixels.into();
414 taffy::style::LengthPercentageAuto::length(pixels * scale_factor)
415 }
416 AbsoluteLength::Rems(rems) => {
417 let pixels: f32 = (*rems * rem_size).into();
418 taffy::style::LengthPercentageAuto::length(pixels * scale_factor)
419 }
420 },
421 DefiniteLength::Fraction(fraction) => {
422 taffy::style::LengthPercentageAuto::percent(*fraction)
423 }
424 }
425 }
426}
427
428impl ToTaffy<taffy::style::Dimension> for DefiniteLength {
429 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> taffy::style::Dimension {
430 match self {
431 DefiniteLength::Absolute(length) => match length {
432 AbsoluteLength::Pixels(pixels) => {
433 let pixels: f32 = pixels.into();
434 taffy::style::Dimension::length(pixels * scale_factor)
435 }
436 AbsoluteLength::Rems(rems) => {
437 taffy::style::Dimension::length((*rems * rem_size * scale_factor).into())
438 }
439 },
440 DefiniteLength::Fraction(fraction) => taffy::style::Dimension::percent(*fraction),
441 }
442 }
443}
444
445impl ToTaffy<taffy::style::LengthPercentage> for AbsoluteLength {
446 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> taffy::style::LengthPercentage {
447 match self {
448 AbsoluteLength::Pixels(pixels) => {
449 let pixels: f32 = pixels.into();
450 taffy::style::LengthPercentage::length(pixels * scale_factor)
451 }
452 AbsoluteLength::Rems(rems) => {
453 let pixels: f32 = (*rems * rem_size).into();
454 taffy::style::LengthPercentage::length(pixels * scale_factor)
455 }
456 }
457 }
458}
459
460impl<T, T2> From<TaffyPoint<T>> for Point<T2>
461where
462 T: Into<T2>,
463 T2: Clone + Debug + Default + PartialEq,
464{
465 fn from(point: TaffyPoint<T>) -> Point<T2> {
466 Point {
467 x: point.x.into(),
468 y: point.y.into(),
469 }
470 }
471}
472
473impl<T, T2> From<Point<T>> for TaffyPoint<T2>
474where
475 T: Into<T2> + Clone + Debug + Default + PartialEq,
476{
477 fn from(val: Point<T>) -> Self {
478 TaffyPoint {
479 x: val.x.into(),
480 y: val.y.into(),
481 }
482 }
483}
484
485impl<T, U> ToTaffy<TaffySize<U>> for Size<T>
486where
487 T: ToTaffy<U> + Clone + Debug + Default + PartialEq,
488{
489 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> TaffySize<U> {
490 TaffySize {
491 width: self.width.to_taffy(rem_size, scale_factor),
492 height: self.height.to_taffy(rem_size, scale_factor),
493 }
494 }
495}
496
497impl<T, U> ToTaffy<TaffyRect<U>> for Edges<T>
498where
499 T: ToTaffy<U> + Clone + Debug + Default + PartialEq,
500{
501 fn to_taffy(&self, rem_size: Pixels, scale_factor: f32) -> TaffyRect<U> {
502 TaffyRect {
503 top: self.top.to_taffy(rem_size, scale_factor),
504 right: self.right.to_taffy(rem_size, scale_factor),
505 bottom: self.bottom.to_taffy(rem_size, scale_factor),
506 left: self.left.to_taffy(rem_size, scale_factor),
507 }
508 }
509}
510
511impl<T, U> From<TaffySize<T>> for Size<U>
512where
513 T: Into<U>,
514 U: Clone + Debug + Default + PartialEq,
515{
516 fn from(taffy_size: TaffySize<T>) -> Self {
517 Size {
518 width: taffy_size.width.into(),
519 height: taffy_size.height.into(),
520 }
521 }
522}
523
524impl<T, U> From<Size<T>> for TaffySize<U>
525where
526 T: Into<U> + Clone + Debug + Default + PartialEq,
527{
528 fn from(size: Size<T>) -> Self {
529 TaffySize {
530 width: size.width.into(),
531 height: size.height.into(),
532 }
533 }
534}
535
536/// The space available for an element to be laid out in
537#[derive(Copy, Clone, Default, Debug, Eq, PartialEq)]
538pub enum AvailableSpace {
539 /// The amount of space available is the specified number of pixels
540 Definite(Pixels),
541 /// The amount of space available is indefinite and the node should be laid out under a min-content constraint
542 #[default]
543 MinContent,
544 /// The amount of space available is indefinite and the node should be laid out under a max-content constraint
545 MaxContent,
546}
547
548impl AvailableSpace {
549 /// Returns a `Size` with both width and height set to `AvailableSpace::MinContent`.
550 ///
551 /// This function is useful when you want to create a `Size` with the minimum content constraints
552 /// for both dimensions.
553 ///
554 /// # Examples
555 ///
556 /// ```
557 /// use gpui::AvailableSpace;
558 /// let min_content_size = AvailableSpace::min_size();
559 /// assert_eq!(min_content_size.width, AvailableSpace::MinContent);
560 /// assert_eq!(min_content_size.height, AvailableSpace::MinContent);
561 /// ```
562 pub const fn min_size() -> Size<Self> {
563 Size {
564 width: Self::MinContent,
565 height: Self::MinContent,
566 }
567 }
568}
569
570impl From<AvailableSpace> for TaffyAvailableSpace {
571 fn from(space: AvailableSpace) -> TaffyAvailableSpace {
572 match space {
573 AvailableSpace::Definite(Pixels(value)) => TaffyAvailableSpace::Definite(value),
574 AvailableSpace::MinContent => TaffyAvailableSpace::MinContent,
575 AvailableSpace::MaxContent => TaffyAvailableSpace::MaxContent,
576 }
577 }
578}
579
580impl From<TaffyAvailableSpace> for AvailableSpace {
581 fn from(space: TaffyAvailableSpace) -> AvailableSpace {
582 match space {
583 TaffyAvailableSpace::Definite(value) => AvailableSpace::Definite(Pixels(value)),
584 TaffyAvailableSpace::MinContent => AvailableSpace::MinContent,
585 TaffyAvailableSpace::MaxContent => AvailableSpace::MaxContent,
586 }
587 }
588}
589
590impl From<Pixels> for AvailableSpace {
591 fn from(pixels: Pixels) -> Self {
592 AvailableSpace::Definite(pixels)
593 }
594}
595
596impl From<Size<Pixels>> for Size<AvailableSpace> {
597 fn from(size: Size<Pixels>) -> Self {
598 Size {
599 width: AvailableSpace::Definite(size.width),
600 height: AvailableSpace::Definite(size.height),
601 }
602 }
603}