1use crate::{
2 geometry::{
3 rect::RectF,
4 vector::{vec2f, Vector2F},
5 },
6 json::json,
7 AnyElement, Element, MouseRegion, SizeConstraint, ViewContext,
8};
9use std::{cell::RefCell, collections::VecDeque, fmt::Debug, ops::Range, rc::Rc};
10use sum_tree::{Bias, SumTree};
11
12pub struct List<V> {
13 state: ListState<V>,
14}
15
16pub struct ListState<V>(Rc<RefCell<StateInner<V>>>);
17
18#[derive(Clone, Copy, Debug, Eq, PartialEq)]
19pub enum Orientation {
20 Top,
21 Bottom,
22}
23
24struct StateInner<V> {
25 last_layout_width: Option<f32>,
26 render_item: Box<dyn FnMut(&mut V, usize, &mut ViewContext<V>) -> AnyElement<V>>,
27 rendered_range: Range<usize>,
28 items: SumTree<ListItem<V>>,
29 logical_scroll_top: Option<ListOffset>,
30 orientation: Orientation,
31 overdraw: f32,
32 #[allow(clippy::type_complexity)]
33 scroll_handler: Option<Box<dyn FnMut(Range<usize>, &mut V, &mut ViewContext<V>)>>,
34}
35
36#[derive(Clone, Copy, Debug, Default, PartialEq)]
37pub struct ListOffset {
38 pub item_ix: usize,
39 pub offset_in_item: f32,
40}
41
42enum ListItem<V> {
43 Unrendered,
44 Rendered(Rc<RefCell<AnyElement<V>>>),
45 Removed(f32),
46}
47
48impl<V> Clone for ListItem<V> {
49 fn clone(&self) -> Self {
50 match self {
51 Self::Unrendered => Self::Unrendered,
52 Self::Rendered(element) => Self::Rendered(element.clone()),
53 Self::Removed(height) => Self::Removed(*height),
54 }
55 }
56}
57
58impl<V> Debug for ListItem<V> {
59 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
60 match self {
61 Self::Unrendered => write!(f, "Unrendered"),
62 Self::Rendered(_) => f.debug_tuple("Rendered").finish(),
63 Self::Removed(height) => f.debug_tuple("Removed").field(height).finish(),
64 }
65 }
66}
67
68#[derive(Clone, Debug, Default, PartialEq)]
69struct ListItemSummary {
70 count: usize,
71 rendered_count: usize,
72 unrendered_count: usize,
73 height: f32,
74}
75
76#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
77struct Count(usize);
78
79#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
80struct RenderedCount(usize);
81
82#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
83struct UnrenderedCount(usize);
84
85#[derive(Clone, Debug, Default)]
86struct Height(f32);
87
88impl<V> List<V> {
89 pub fn new(state: ListState<V>) -> Self {
90 Self { state }
91 }
92}
93
94impl<V: 'static> Element<V> for List<V> {
95 type LayoutState = ListOffset;
96 type PaintState = ();
97
98 fn layout(
99 &mut self,
100 constraint: SizeConstraint,
101 view: &mut V,
102 cx: &mut ViewContext<V>,
103 ) -> (Vector2F, Self::LayoutState) {
104 let state = &mut *self.state.0.borrow_mut();
105 let size = constraint.max;
106 let mut item_constraint = constraint;
107 item_constraint.min.set_y(0.);
108 item_constraint.max.set_y(f32::INFINITY);
109
110 if cx.refreshing() || state.last_layout_width != Some(size.x()) {
111 state.rendered_range = 0..0;
112 state.items = SumTree::from_iter(
113 (0..state.items.summary().count).map(|_| ListItem::Unrendered),
114 &(),
115 )
116 }
117
118 let old_items = state.items.clone();
119 let mut new_items = SumTree::new();
120 let mut rendered_items = VecDeque::new();
121 let mut rendered_height = 0.;
122 let mut scroll_top = state.logical_scroll_top();
123
124 // Render items after the scroll top, including those in the trailing overdraw.
125 let mut cursor = old_items.cursor::<Count>();
126 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
127 for (ix, item) in cursor.by_ref().enumerate() {
128 let visible_height = rendered_height - scroll_top.offset_in_item;
129 if visible_height >= size.y() + state.overdraw {
130 break;
131 }
132
133 // Force re-render if the item is visible, but attempt to re-use an existing one
134 // if we are inside the overdraw.
135 let existing_element = if visible_height >= size.y() {
136 Some(item)
137 } else {
138 None
139 };
140 if let Some(element) = state.render_item(
141 scroll_top.item_ix + ix,
142 existing_element,
143 item_constraint,
144 view,
145 cx,
146 ) {
147 rendered_height += element.borrow().size().y();
148 rendered_items.push_back(ListItem::Rendered(element));
149 }
150 }
151
152 // Prepare to start walking upward from the item at the scroll top.
153 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
154
155 // If the rendered items do not fill the visible region, then adjust
156 // the scroll top upward.
157 if rendered_height - scroll_top.offset_in_item < size.y() {
158 while rendered_height < size.y() {
159 cursor.prev(&());
160 if cursor.item().is_some() {
161 if let Some(element) =
162 state.render_item(cursor.start().0, None, item_constraint, view, cx)
163 {
164 rendered_height += element.borrow().size().y();
165 rendered_items.push_front(ListItem::Rendered(element));
166 }
167 } else {
168 break;
169 }
170 }
171
172 scroll_top = ListOffset {
173 item_ix: cursor.start().0,
174 offset_in_item: rendered_height - size.y(),
175 };
176
177 match state.orientation {
178 Orientation::Top => {
179 scroll_top.offset_in_item = scroll_top.offset_in_item.max(0.);
180 state.logical_scroll_top = Some(scroll_top);
181 }
182 Orientation::Bottom => {
183 scroll_top = ListOffset {
184 item_ix: cursor.start().0,
185 offset_in_item: rendered_height - size.y(),
186 };
187 state.logical_scroll_top = None;
188 }
189 };
190 }
191
192 // Render items in the leading overdraw.
193 let mut leading_overdraw = scroll_top.offset_in_item;
194 while leading_overdraw < state.overdraw {
195 cursor.prev(&());
196 if let Some(item) = cursor.item() {
197 if let Some(element) =
198 state.render_item(cursor.start().0, Some(item), item_constraint, view, cx)
199 {
200 leading_overdraw += element.borrow().size().y();
201 rendered_items.push_front(ListItem::Rendered(element));
202 }
203 } else {
204 break;
205 }
206 }
207
208 let new_rendered_range = cursor.start().0..(cursor.start().0 + rendered_items.len());
209
210 let mut cursor = old_items.cursor::<Count>();
211
212 if state.rendered_range.start < new_rendered_range.start {
213 new_items.append(
214 cursor.slice(&Count(state.rendered_range.start), Bias::Right, &()),
215 &(),
216 );
217 let remove_to = state.rendered_range.end.min(new_rendered_range.start);
218 while cursor.start().0 < remove_to {
219 new_items.push(cursor.item().unwrap().remove(), &());
220 cursor.next(&());
221 }
222 }
223 new_items.append(
224 cursor.slice(&Count(new_rendered_range.start), Bias::Right, &()),
225 &(),
226 );
227
228 new_items.extend(rendered_items, &());
229 cursor.seek(&Count(new_rendered_range.end), Bias::Right, &());
230
231 if new_rendered_range.end < state.rendered_range.start {
232 new_items.append(
233 cursor.slice(&Count(state.rendered_range.start), Bias::Right, &()),
234 &(),
235 );
236 }
237 while cursor.start().0 < state.rendered_range.end {
238 new_items.push(cursor.item().unwrap().remove(), &());
239 cursor.next(&());
240 }
241
242 new_items.append(cursor.suffix(&()), &());
243
244 state.items = new_items;
245 state.rendered_range = new_rendered_range;
246 state.last_layout_width = Some(size.x());
247 (size, scroll_top)
248 }
249
250 fn paint(
251 &mut self,
252 bounds: RectF,
253 visible_bounds: RectF,
254 scroll_top: &mut ListOffset,
255 view: &mut V,
256 cx: &mut ViewContext<V>,
257 ) {
258 let visible_bounds = visible_bounds.intersection(bounds).unwrap_or_default();
259 cx.scene().push_layer(Some(visible_bounds));
260 let view_id = cx.view_id();
261 cx.scene()
262 .push_mouse_region(MouseRegion::new::<Self>(view_id, 0, bounds).on_scroll({
263 let state = self.state.clone();
264 let height = bounds.height();
265 let scroll_top = scroll_top.clone();
266 move |e, view, cx| {
267 state.0.borrow_mut().scroll(
268 &scroll_top,
269 height,
270 *e.platform_event.delta.raw(),
271 e.platform_event.delta.precise(),
272 view,
273 cx,
274 )
275 }
276 }));
277
278 let state = &mut *self.state.0.borrow_mut();
279 for (element, origin) in state.visible_elements(bounds, scroll_top) {
280 element.borrow_mut().paint(origin, visible_bounds, view, cx);
281 }
282
283 cx.scene().pop_layer();
284 }
285
286 fn rect_for_text_range(
287 &self,
288 range_utf16: Range<usize>,
289 bounds: RectF,
290 _: RectF,
291 scroll_top: &Self::LayoutState,
292 _: &Self::PaintState,
293 view: &V,
294 cx: &ViewContext<V>,
295 ) -> Option<RectF> {
296 let state = self.state.0.borrow();
297 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
298 let mut cursor = state.items.cursor::<Count>();
299 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
300 while let Some(item) = cursor.item() {
301 if item_origin.y() > bounds.max_y() {
302 break;
303 }
304
305 if let ListItem::Rendered(element) = item {
306 if let Some(rect) =
307 element
308 .borrow()
309 .rect_for_text_range(range_utf16.clone(), view, cx)
310 {
311 return Some(rect);
312 }
313
314 item_origin.set_y(item_origin.y() + element.borrow().size().y());
315 cursor.next(&());
316 } else {
317 unreachable!();
318 }
319 }
320
321 None
322 }
323
324 fn debug(
325 &self,
326 bounds: RectF,
327 scroll_top: &Self::LayoutState,
328 _: &(),
329 view: &V,
330 cx: &ViewContext<V>,
331 ) -> serde_json::Value {
332 let state = self.state.0.borrow_mut();
333 let visible_elements = state
334 .visible_elements(bounds, scroll_top)
335 .map(|e| e.0.borrow().debug(view, cx))
336 .collect::<Vec<_>>();
337 let visible_range = scroll_top.item_ix..(scroll_top.item_ix + visible_elements.len());
338 json!({
339 "visible_range": visible_range,
340 "visible_elements": visible_elements,
341 "scroll_top": state.logical_scroll_top.map(|top| (top.item_ix, top.offset_in_item)),
342 })
343 }
344}
345
346impl<V: 'static> ListState<V> {
347 pub fn new<D, F>(
348 element_count: usize,
349 orientation: Orientation,
350 overdraw: f32,
351 mut render_item: F,
352 ) -> Self
353 where
354 D: Element<V>,
355 F: 'static + FnMut(&mut V, usize, &mut ViewContext<V>) -> D,
356 {
357 let mut items = SumTree::new();
358 items.extend((0..element_count).map(|_| ListItem::Unrendered), &());
359 Self(Rc::new(RefCell::new(StateInner {
360 last_layout_width: None,
361 render_item: Box::new(move |view, ix, cx| render_item(view, ix, cx).into_any()),
362 rendered_range: 0..0,
363 items,
364 logical_scroll_top: None,
365 orientation,
366 overdraw,
367 scroll_handler: None,
368 })))
369 }
370
371 pub fn reset(&self, element_count: usize) {
372 let state = &mut *self.0.borrow_mut();
373 state.rendered_range = 0..0;
374 state.logical_scroll_top = None;
375 state.items = SumTree::new();
376 state
377 .items
378 .extend((0..element_count).map(|_| ListItem::Unrendered), &());
379 }
380
381 pub fn splice(&self, old_range: Range<usize>, count: usize) {
382 let state = &mut *self.0.borrow_mut();
383
384 if let Some(ListOffset {
385 item_ix,
386 offset_in_item,
387 }) = state.logical_scroll_top.as_mut()
388 {
389 if old_range.contains(item_ix) {
390 *item_ix = old_range.start;
391 *offset_in_item = 0.;
392 } else if old_range.end <= *item_ix {
393 *item_ix = *item_ix - (old_range.end - old_range.start) + count;
394 }
395 }
396
397 let new_end = old_range.start + count;
398 if old_range.start < state.rendered_range.start {
399 state.rendered_range.start =
400 new_end + state.rendered_range.start.saturating_sub(old_range.end);
401 }
402 if old_range.start < state.rendered_range.end {
403 state.rendered_range.end =
404 new_end + state.rendered_range.end.saturating_sub(old_range.end);
405 }
406
407 let mut old_heights = state.items.cursor::<Count>();
408 let mut new_heights = old_heights.slice(&Count(old_range.start), Bias::Right, &());
409 old_heights.seek_forward(&Count(old_range.end), Bias::Right, &());
410
411 new_heights.extend((0..count).map(|_| ListItem::Unrendered), &());
412 new_heights.append(old_heights.suffix(&()), &());
413 drop(old_heights);
414 state.items = new_heights;
415 }
416
417 pub fn set_scroll_handler(
418 &mut self,
419 handler: impl FnMut(Range<usize>, &mut V, &mut ViewContext<V>) + 'static,
420 ) {
421 self.0.borrow_mut().scroll_handler = Some(Box::new(handler))
422 }
423
424 pub fn logical_scroll_top(&self) -> ListOffset {
425 self.0.borrow().logical_scroll_top()
426 }
427
428 pub fn scroll_to(&self, mut scroll_top: ListOffset) {
429 let state = &mut *self.0.borrow_mut();
430 let item_count = state.items.summary().count;
431 if scroll_top.item_ix >= item_count {
432 scroll_top.item_ix = item_count;
433 scroll_top.offset_in_item = 0.;
434 }
435 state.logical_scroll_top = Some(scroll_top);
436 }
437}
438
439impl<V> Clone for ListState<V> {
440 fn clone(&self) -> Self {
441 Self(self.0.clone())
442 }
443}
444
445impl<V: 'static> StateInner<V> {
446 fn render_item(
447 &mut self,
448 ix: usize,
449 existing_element: Option<&ListItem<V>>,
450 constraint: SizeConstraint,
451 view: &mut V,
452 cx: &mut ViewContext<V>,
453 ) -> Option<Rc<RefCell<AnyElement<V>>>> {
454 if let Some(ListItem::Rendered(element)) = existing_element {
455 Some(element.clone())
456 } else {
457 let mut element = (self.render_item)(view, ix, cx);
458 element.layout(constraint, view, cx);
459 Some(Rc::new(RefCell::new(element)))
460 }
461 }
462
463 fn visible_range(&self, height: f32, scroll_top: &ListOffset) -> Range<usize> {
464 let mut cursor = self.items.cursor::<ListItemSummary>();
465 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
466 let start_y = cursor.start().height + scroll_top.offset_in_item;
467 cursor.seek_forward(&Height(start_y + height), Bias::Left, &());
468 scroll_top.item_ix..cursor.start().count + 1
469 }
470
471 fn visible_elements<'a>(
472 &'a self,
473 bounds: RectF,
474 scroll_top: &ListOffset,
475 ) -> impl Iterator<Item = (Rc<RefCell<AnyElement<V>>>, Vector2F)> + 'a {
476 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
477 let mut cursor = self.items.cursor::<Count>();
478 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
479 std::iter::from_fn(move || {
480 while let Some(item) = cursor.item() {
481 if item_origin.y() > bounds.max_y() {
482 break;
483 }
484
485 if let ListItem::Rendered(element) = item {
486 let result = (element.clone(), item_origin);
487 item_origin.set_y(item_origin.y() + element.borrow().size().y());
488 cursor.next(&());
489 return Some(result);
490 }
491
492 cursor.next(&());
493 }
494
495 None
496 })
497 }
498
499 fn scroll(
500 &mut self,
501 scroll_top: &ListOffset,
502 height: f32,
503 mut delta: Vector2F,
504 precise: bool,
505 view: &mut V,
506 cx: &mut ViewContext<V>,
507 ) {
508 if !precise {
509 delta *= 20.;
510 }
511
512 let scroll_max = (self.items.summary().height - height).max(0.);
513 let new_scroll_top = (self.scroll_top(scroll_top) - delta.y())
514 .max(0.)
515 .min(scroll_max);
516
517 if self.orientation == Orientation::Bottom && new_scroll_top == scroll_max {
518 self.logical_scroll_top = None;
519 } else {
520 let mut cursor = self.items.cursor::<ListItemSummary>();
521 cursor.seek(&Height(new_scroll_top), Bias::Right, &());
522 let item_ix = cursor.start().count;
523 let offset_in_item = new_scroll_top - cursor.start().height;
524 self.logical_scroll_top = Some(ListOffset {
525 item_ix,
526 offset_in_item,
527 });
528 }
529
530 if self.scroll_handler.is_some() {
531 let visible_range = self.visible_range(height, scroll_top);
532 self.scroll_handler.as_mut().unwrap()(visible_range, view, cx);
533 }
534
535 cx.notify();
536 }
537
538 fn logical_scroll_top(&self) -> ListOffset {
539 self.logical_scroll_top
540 .unwrap_or_else(|| match self.orientation {
541 Orientation::Top => ListOffset {
542 item_ix: 0,
543 offset_in_item: 0.,
544 },
545 Orientation::Bottom => ListOffset {
546 item_ix: self.items.summary().count,
547 offset_in_item: 0.,
548 },
549 })
550 }
551
552 fn scroll_top(&self, logical_scroll_top: &ListOffset) -> f32 {
553 let mut cursor = self.items.cursor::<ListItemSummary>();
554 cursor.seek(&Count(logical_scroll_top.item_ix), Bias::Right, &());
555 cursor.start().height + logical_scroll_top.offset_in_item
556 }
557}
558
559impl<V> ListItem<V> {
560 fn remove(&self) -> Self {
561 match self {
562 ListItem::Unrendered => ListItem::Unrendered,
563 ListItem::Rendered(element) => ListItem::Removed(element.borrow().size().y()),
564 ListItem::Removed(height) => ListItem::Removed(*height),
565 }
566 }
567}
568
569impl<V> sum_tree::Item for ListItem<V> {
570 type Summary = ListItemSummary;
571
572 fn summary(&self) -> Self::Summary {
573 match self {
574 ListItem::Unrendered => ListItemSummary {
575 count: 1,
576 rendered_count: 0,
577 unrendered_count: 1,
578 height: 0.,
579 },
580 ListItem::Rendered(element) => ListItemSummary {
581 count: 1,
582 rendered_count: 1,
583 unrendered_count: 0,
584 height: element.borrow().size().y(),
585 },
586 ListItem::Removed(height) => ListItemSummary {
587 count: 1,
588 rendered_count: 0,
589 unrendered_count: 1,
590 height: *height,
591 },
592 }
593 }
594}
595
596impl sum_tree::Summary for ListItemSummary {
597 type Context = ();
598
599 fn add_summary(&mut self, summary: &Self, _: &()) {
600 self.count += summary.count;
601 self.rendered_count += summary.rendered_count;
602 self.unrendered_count += summary.unrendered_count;
603 self.height += summary.height;
604 }
605}
606
607impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Count {
608 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
609 self.0 += summary.count;
610 }
611}
612
613impl<'a> sum_tree::Dimension<'a, ListItemSummary> for RenderedCount {
614 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
615 self.0 += summary.rendered_count;
616 }
617}
618
619impl<'a> sum_tree::Dimension<'a, ListItemSummary> for UnrenderedCount {
620 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
621 self.0 += summary.unrendered_count;
622 }
623}
624
625impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Height {
626 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
627 self.0 += summary.height;
628 }
629}
630
631impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Count {
632 fn cmp(&self, other: &ListItemSummary, _: &()) -> std::cmp::Ordering {
633 self.0.partial_cmp(&other.count).unwrap()
634 }
635}
636
637impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Height {
638 fn cmp(&self, other: &ListItemSummary, _: &()) -> std::cmp::Ordering {
639 self.0.partial_cmp(&other.height).unwrap()
640 }
641}
642
643#[cfg(test)]
644mod tests {
645 use super::*;
646 use crate::{elements::Empty, geometry::vector::vec2f, Entity};
647 use rand::prelude::*;
648 use std::env;
649
650 #[crate::test(self)]
651 fn test_layout(cx: &mut crate::AppContext) {
652 cx.add_window(Default::default(), |cx| {
653 let mut view = TestView;
654 let constraint = SizeConstraint::new(vec2f(0., 0.), vec2f(100., 40.));
655 let elements = Rc::new(RefCell::new(vec![(0, 20.), (1, 30.), (2, 100.)]));
656 let state = ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, {
657 let elements = elements.clone();
658 move |_, ix, _| {
659 let (id, height) = elements.borrow()[ix];
660 TestElement::new(id, height).into_any()
661 }
662 });
663
664 let mut list = List::new(state.clone());
665 let (size, _) = list.layout(constraint, &mut view, cx);
666 assert_eq!(size, vec2f(100., 40.));
667 assert_eq!(
668 state.0.borrow().items.summary().clone(),
669 ListItemSummary {
670 count: 3,
671 rendered_count: 3,
672 unrendered_count: 0,
673 height: 150.
674 }
675 );
676
677 state.0.borrow_mut().scroll(
678 &ListOffset {
679 item_ix: 0,
680 offset_in_item: 0.,
681 },
682 40.,
683 vec2f(0., -54.),
684 true,
685 &mut view,
686 cx,
687 );
688
689 let (_, logical_scroll_top) = list.layout(constraint, &mut view, cx);
690 assert_eq!(
691 logical_scroll_top,
692 ListOffset {
693 item_ix: 2,
694 offset_in_item: 4.
695 }
696 );
697 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 54.);
698
699 elements.borrow_mut().splice(1..2, vec![(3, 40.), (4, 50.)]);
700 elements.borrow_mut().push((5, 60.));
701 state.splice(1..2, 2);
702 state.splice(4..4, 1);
703 assert_eq!(
704 state.0.borrow().items.summary().clone(),
705 ListItemSummary {
706 count: 5,
707 rendered_count: 2,
708 unrendered_count: 3,
709 height: 120.
710 }
711 );
712
713 let (size, logical_scroll_top) = list.layout(constraint, &mut view, cx);
714 assert_eq!(size, vec2f(100., 40.));
715 assert_eq!(
716 state.0.borrow().items.summary().clone(),
717 ListItemSummary {
718 count: 5,
719 rendered_count: 5,
720 unrendered_count: 0,
721 height: 270.
722 }
723 );
724 assert_eq!(
725 logical_scroll_top,
726 ListOffset {
727 item_ix: 3,
728 offset_in_item: 4.
729 }
730 );
731 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 114.);
732
733 view
734 });
735 }
736
737 #[crate::test(self, iterations = 10)]
738 fn test_random(cx: &mut crate::AppContext, mut rng: StdRng) {
739 let operations = env::var("OPERATIONS")
740 .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
741 .unwrap_or(10);
742
743 cx.add_window(Default::default(), |cx| {
744 let mut view = TestView;
745
746 let mut next_id = 0;
747 let elements = Rc::new(RefCell::new(
748 (0..rng.gen_range(0..=20))
749 .map(|_| {
750 let id = next_id;
751 next_id += 1;
752 (id, rng.gen_range(0..=200) as f32 / 2.0)
753 })
754 .collect::<Vec<_>>(),
755 ));
756 let orientation = *[Orientation::Top, Orientation::Bottom]
757 .choose(&mut rng)
758 .unwrap();
759 let overdraw = rng.gen_range(1..=100) as f32;
760
761 let state = ListState::new(elements.borrow().len(), orientation, overdraw, {
762 let elements = elements.clone();
763 move |_, ix, _| {
764 let (id, height) = elements.borrow()[ix];
765 TestElement::new(id, height).into_any()
766 }
767 });
768
769 let mut width = rng.gen_range(0..=2000) as f32 / 2.;
770 let mut height = rng.gen_range(0..=2000) as f32 / 2.;
771 log::info!("orientation: {:?}", orientation);
772 log::info!("overdraw: {}", overdraw);
773 log::info!("elements: {:?}", elements.borrow());
774 log::info!("size: ({:?}, {:?})", width, height);
775 log::info!("==================");
776
777 let mut last_logical_scroll_top = None;
778 for _ in 0..operations {
779 match rng.gen_range(0..=100) {
780 0..=29 if last_logical_scroll_top.is_some() => {
781 let delta = vec2f(0., rng.gen_range(-overdraw..=overdraw));
782 log::info!(
783 "Scrolling by {:?}, previous scroll top: {:?}",
784 delta,
785 last_logical_scroll_top.unwrap()
786 );
787 state.0.borrow_mut().scroll(
788 last_logical_scroll_top.as_ref().unwrap(),
789 height,
790 delta,
791 true,
792 &mut view,
793 cx,
794 );
795 }
796 30..=34 => {
797 width = rng.gen_range(0..=2000) as f32 / 2.;
798 log::info!("changing width: {:?}", width);
799 }
800 35..=54 => {
801 height = rng.gen_range(0..=1000) as f32 / 2.;
802 log::info!("changing height: {:?}", height);
803 }
804 _ => {
805 let mut elements = elements.borrow_mut();
806 let end_ix = rng.gen_range(0..=elements.len());
807 let start_ix = rng.gen_range(0..=end_ix);
808 let new_elements = (0..rng.gen_range(0..10))
809 .map(|_| {
810 let id = next_id;
811 next_id += 1;
812 (id, rng.gen_range(0..=200) as f32 / 2.)
813 })
814 .collect::<Vec<_>>();
815 log::info!("splice({:?}, {:?})", start_ix..end_ix, new_elements);
816 state.splice(start_ix..end_ix, new_elements.len());
817 elements.splice(start_ix..end_ix, new_elements);
818 for (ix, item) in state.0.borrow().items.cursor::<()>().enumerate() {
819 if let ListItem::Rendered(element) = item {
820 let (expected_id, _) = elements[ix];
821 element.borrow().with_metadata(|metadata: Option<&usize>| {
822 assert_eq!(*metadata.unwrap(), expected_id);
823 });
824 }
825 }
826 }
827 }
828
829 let mut list = List::new(state.clone());
830 let window_size = vec2f(width, height);
831 let (size, logical_scroll_top) = list.layout(
832 SizeConstraint::new(vec2f(0., 0.), window_size),
833 &mut view,
834 cx,
835 );
836 assert_eq!(size, window_size);
837 last_logical_scroll_top = Some(logical_scroll_top);
838
839 let state = state.0.borrow();
840 log::info!("items {:?}", state.items.items(&()));
841
842 let scroll_top = state.scroll_top(&logical_scroll_top);
843 let rendered_top = (scroll_top - overdraw).max(0.);
844 let rendered_bottom = scroll_top + height + overdraw;
845 let mut item_top = 0.;
846
847 log::info!(
848 "rendered top {:?}, rendered bottom {:?}, scroll top {:?}",
849 rendered_top,
850 rendered_bottom,
851 scroll_top,
852 );
853
854 let mut first_rendered_element_top = None;
855 let mut last_rendered_element_bottom = None;
856 assert_eq!(state.items.summary().count, elements.borrow().len());
857 for (ix, item) in state.items.cursor::<()>().enumerate() {
858 match item {
859 ListItem::Unrendered => {
860 let item_bottom = item_top;
861 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
862 item_top = item_bottom;
863 }
864 ListItem::Removed(height) => {
865 let (id, expected_height) = elements.borrow()[ix];
866 assert_eq!(
867 *height, expected_height,
868 "element {} height didn't match",
869 id
870 );
871 let item_bottom = item_top + height;
872 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
873 item_top = item_bottom;
874 }
875 ListItem::Rendered(element) => {
876 let (expected_id, expected_height) = elements.borrow()[ix];
877 let element = element.borrow();
878 element.with_metadata(|metadata: Option<&usize>| {
879 assert_eq!(*metadata.unwrap(), expected_id);
880 });
881 assert_eq!(element.size().y(), expected_height);
882 let item_bottom = item_top + element.size().y();
883 first_rendered_element_top.get_or_insert(item_top);
884 last_rendered_element_bottom = Some(item_bottom);
885 assert!(item_bottom > rendered_top || item_top < rendered_bottom);
886 item_top = item_bottom;
887 }
888 }
889 }
890
891 match orientation {
892 Orientation::Top => {
893 if let Some(first_rendered_element_top) = first_rendered_element_top {
894 assert!(first_rendered_element_top <= scroll_top);
895 }
896 }
897 Orientation::Bottom => {
898 if let Some(last_rendered_element_bottom) = last_rendered_element_bottom {
899 assert!(last_rendered_element_bottom >= scroll_top + height);
900 }
901 }
902 }
903 }
904
905 view
906 });
907 }
908
909 struct TestView;
910
911 impl Entity for TestView {
912 type Event = ();
913 }
914
915 impl crate::View for TestView {
916 fn ui_name() -> &'static str {
917 "TestView"
918 }
919
920 fn render(&mut self, _: &mut ViewContext<Self>) -> AnyElement<Self> {
921 Empty::new().into_any()
922 }
923 }
924
925 struct TestElement {
926 id: usize,
927 size: Vector2F,
928 }
929
930 impl TestElement {
931 fn new(id: usize, height: f32) -> Self {
932 Self {
933 id,
934 size: vec2f(100., height),
935 }
936 }
937 }
938
939 impl<V: 'static> Element<V> for TestElement {
940 type LayoutState = ();
941 type PaintState = ();
942
943 fn layout(
944 &mut self,
945 _: SizeConstraint,
946 _: &mut V,
947 _: &mut ViewContext<V>,
948 ) -> (Vector2F, ()) {
949 (self.size, ())
950 }
951
952 fn paint(&mut self, _: RectF, _: RectF, _: &mut (), _: &mut V, _: &mut ViewContext<V>) {
953 unimplemented!()
954 }
955
956 fn rect_for_text_range(
957 &self,
958 _: Range<usize>,
959 _: RectF,
960 _: RectF,
961 _: &Self::LayoutState,
962 _: &Self::PaintState,
963 _: &V,
964 _: &ViewContext<V>,
965 ) -> Option<RectF> {
966 unimplemented!()
967 }
968
969 fn debug(&self, _: RectF, _: &(), _: &(), _: &V, _: &ViewContext<V>) -> serde_json::Value {
970 self.id.into()
971 }
972
973 fn metadata(&self) -> Option<&dyn std::any::Any> {
974 Some(&self.id)
975 }
976 }
977}