1use crate::{
2 geometry::{
3 rect::RectF,
4 vector::{vec2f, Vector2F},
5 },
6 json::json,
7 presenter::MeasurementContext,
8 DebugContext, Element, ElementBox, ElementRc, Event, EventContext, LayoutContext, PaintContext,
9 RenderContext, ScrollWheelEvent, SizeConstraint, View, ViewContext,
10};
11use std::{cell::RefCell, collections::VecDeque, ops::Range, rc::Rc};
12use sum_tree::{Bias, SumTree};
13
14pub struct List {
15 state: ListState,
16 invalidated_elements: Vec<ElementRc>,
17}
18
19#[derive(Clone)]
20pub struct ListState(Rc<RefCell<StateInner>>);
21
22#[derive(Clone, Copy, Debug, Eq, PartialEq)]
23pub enum Orientation {
24 Top,
25 Bottom,
26}
27
28struct StateInner {
29 last_layout_width: Option<f32>,
30 render_item: Box<dyn FnMut(usize, &mut LayoutContext) -> Option<ElementBox>>,
31 rendered_range: Range<usize>,
32 items: SumTree<ListItem>,
33 logical_scroll_top: Option<ListOffset>,
34 orientation: Orientation,
35 overdraw: f32,
36 #[allow(clippy::type_complexity)]
37 scroll_handler: Option<Box<dyn FnMut(Range<usize>, &mut EventContext)>>,
38}
39
40#[derive(Clone, Copy, Debug, Default, PartialEq)]
41pub struct ListOffset {
42 item_ix: usize,
43 offset_in_item: f32,
44}
45
46#[derive(Clone)]
47enum ListItem {
48 Unrendered,
49 Rendered(ElementRc),
50 Removed(f32),
51}
52
53impl std::fmt::Debug for ListItem {
54 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
55 match self {
56 Self::Unrendered => write!(f, "Unrendered"),
57 Self::Rendered(_) => f.debug_tuple("Rendered").finish(),
58 Self::Removed(height) => f.debug_tuple("Removed").field(height).finish(),
59 }
60 }
61}
62
63#[derive(Clone, Debug, Default, PartialEq)]
64struct ListItemSummary {
65 count: usize,
66 rendered_count: usize,
67 unrendered_count: usize,
68 height: f32,
69}
70
71#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
72struct Count(usize);
73
74#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
75struct RenderedCount(usize);
76
77#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
78struct UnrenderedCount(usize);
79
80#[derive(Clone, Debug, Default)]
81struct Height(f32);
82
83impl List {
84 pub fn new(state: ListState) -> Self {
85 Self {
86 state,
87 invalidated_elements: Default::default(),
88 }
89 }
90}
91
92impl Element for List {
93 type LayoutState = ListOffset;
94 type PaintState = ();
95
96 fn layout(
97 &mut self,
98 constraint: SizeConstraint,
99 cx: &mut LayoutContext,
100 ) -> (Vector2F, Self::LayoutState) {
101 let state = &mut *self.state.0.borrow_mut();
102 let size = constraint.max;
103 let mut item_constraint = constraint;
104 item_constraint.min.set_y(0.);
105 item_constraint.max.set_y(f32::INFINITY);
106
107 if cx.refreshing || state.last_layout_width != Some(size.x()) {
108 state.rendered_range = 0..0;
109 state.items = SumTree::from_iter(
110 (0..state.items.summary().count).map(|_| ListItem::Unrendered),
111 &(),
112 )
113 }
114
115 let old_items = state.items.clone();
116 let mut new_items = SumTree::new();
117 let mut rendered_items = VecDeque::new();
118 let mut rendered_height = 0.;
119 let mut scroll_top = state
120 .logical_scroll_top
121 .unwrap_or_else(|| match state.orientation {
122 Orientation::Top => ListOffset {
123 item_ix: 0,
124 offset_in_item: 0.,
125 },
126 Orientation::Bottom => ListOffset {
127 item_ix: state.items.summary().count,
128 offset_in_item: 0.,
129 },
130 });
131
132 // Render items after the scroll top, including those in the trailing overdraw.
133 let mut cursor = old_items.cursor::<Count>();
134 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
135 for (ix, item) in cursor.by_ref().enumerate() {
136 let visible_height = rendered_height - scroll_top.offset_in_item;
137 if visible_height >= size.y() + state.overdraw {
138 break;
139 }
140
141 // Force re-render if the item is visible, but attempt to re-use an existing one
142 // if we are inside the overdraw.
143 let existing_element = if visible_height >= size.y() {
144 Some(item)
145 } else {
146 None
147 };
148 if let Some(element) = state.render_item(
149 scroll_top.item_ix + ix,
150 existing_element,
151 item_constraint,
152 cx,
153 ) {
154 rendered_height += element.size().y();
155 rendered_items.push_back(ListItem::Rendered(element));
156 }
157 }
158
159 // Prepare to start walking upward from the item at the scroll top.
160 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
161
162 // If the rendered items do not fill the visible region, then adjust
163 // the scroll top upward.
164 if rendered_height - scroll_top.offset_in_item < size.y() {
165 while rendered_height < size.y() {
166 cursor.prev(&());
167 if cursor.item().is_some() {
168 if let Some(element) =
169 state.render_item(cursor.start().0, None, item_constraint, cx)
170 {
171 rendered_height += element.size().y();
172 rendered_items.push_front(ListItem::Rendered(element));
173 }
174 } else {
175 break;
176 }
177 }
178
179 scroll_top = ListOffset {
180 item_ix: cursor.start().0,
181 offset_in_item: rendered_height - size.y(),
182 };
183
184 match state.orientation {
185 Orientation::Top => {
186 scroll_top.offset_in_item = scroll_top.offset_in_item.max(0.);
187 state.logical_scroll_top = Some(scroll_top);
188 }
189 Orientation::Bottom => {
190 scroll_top = ListOffset {
191 item_ix: cursor.start().0,
192 offset_in_item: rendered_height - size.y(),
193 };
194 state.logical_scroll_top = None;
195 }
196 };
197 }
198
199 // Render items in the leading overdraw.
200 let mut leading_overdraw = scroll_top.offset_in_item;
201 while leading_overdraw < state.overdraw {
202 cursor.prev(&());
203 if let Some(item) = cursor.item() {
204 if let Some(element) =
205 state.render_item(cursor.start().0, Some(item), item_constraint, cx)
206 {
207 leading_overdraw += element.size().y();
208 rendered_items.push_front(ListItem::Rendered(element));
209 }
210 } else {
211 break;
212 }
213 }
214
215 let new_rendered_range = cursor.start().0..(cursor.start().0 + rendered_items.len());
216
217 let mut cursor = old_items.cursor::<Count>();
218
219 if state.rendered_range.start < new_rendered_range.start {
220 new_items.push_tree(
221 cursor.slice(&Count(state.rendered_range.start), Bias::Right, &()),
222 &(),
223 );
224 let remove_to = state.rendered_range.end.min(new_rendered_range.start);
225 while cursor.start().0 < remove_to {
226 new_items.push(cursor.item().unwrap().remove(), &());
227 cursor.next(&());
228 }
229 }
230 new_items.push_tree(
231 cursor.slice(&Count(new_rendered_range.start), Bias::Right, &()),
232 &(),
233 );
234
235 new_items.extend(rendered_items, &());
236 cursor.seek(&Count(new_rendered_range.end), Bias::Right, &());
237
238 if new_rendered_range.end < state.rendered_range.start {
239 new_items.push_tree(
240 cursor.slice(&Count(state.rendered_range.start), Bias::Right, &()),
241 &(),
242 );
243 }
244 while cursor.start().0 < state.rendered_range.end {
245 new_items.push(cursor.item().unwrap().remove(), &());
246 cursor.next(&());
247 }
248
249 new_items.push_tree(cursor.suffix(&()), &());
250
251 state.items = new_items;
252 state.rendered_range = new_rendered_range;
253 state.last_layout_width = Some(size.x());
254 (size, scroll_top)
255 }
256
257 fn paint(
258 &mut self,
259 bounds: RectF,
260 visible_bounds: RectF,
261 scroll_top: &mut ListOffset,
262 cx: &mut PaintContext,
263 ) {
264 cx.scene.push_layer(Some(bounds));
265
266 let state = &mut *self.state.0.borrow_mut();
267 for (mut element, origin) in state.visible_elements(bounds, scroll_top) {
268 element.paint(origin, visible_bounds, cx);
269 }
270
271 cx.scene.pop_layer();
272 }
273
274 fn dispatch_event(
275 &mut self,
276 event: &Event,
277 bounds: RectF,
278 _: RectF,
279 scroll_top: &mut ListOffset,
280 _: &mut (),
281 cx: &mut EventContext,
282 ) -> bool {
283 let mut handled = false;
284
285 let mut state = self.state.0.borrow_mut();
286 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
287 let mut cursor = state.items.cursor::<Count>();
288 let mut new_items = cursor.slice(&Count(scroll_top.item_ix), Bias::Right, &());
289 while let Some(item) = cursor.item() {
290 if item_origin.y() > bounds.max_y() {
291 break;
292 }
293
294 if let ListItem::Rendered(element) = item {
295 let prev_notify_count = cx.notify_count();
296 let mut element = element.clone();
297 handled = element.dispatch_event(event, cx) || handled;
298 item_origin.set_y(item_origin.y() + element.size().y());
299 if cx.notify_count() > prev_notify_count {
300 new_items.push(ListItem::Unrendered, &());
301 self.invalidated_elements.push(element);
302 } else {
303 new_items.push(item.clone(), &());
304 }
305 cursor.next(&());
306 } else {
307 unreachable!();
308 }
309 }
310
311 new_items.push_tree(cursor.suffix(&()), &());
312 drop(cursor);
313 state.items = new_items;
314
315 if let Event::ScrollWheel(ScrollWheelEvent {
316 position,
317 delta,
318 precise,
319 ..
320 }) = event
321 {
322 if bounds.contains_point(*position)
323 && state.scroll(scroll_top, bounds.height(), *delta, *precise, cx)
324 {
325 handled = true;
326 }
327 }
328
329 handled
330 }
331
332 fn rect_for_text_range(
333 &self,
334 range_utf16: Range<usize>,
335 bounds: RectF,
336 _: RectF,
337 scroll_top: &Self::LayoutState,
338 _: &Self::PaintState,
339 cx: &MeasurementContext,
340 ) -> Option<RectF> {
341 let state = self.state.0.borrow();
342 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
343 let mut cursor = state.items.cursor::<Count>();
344 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
345 while let Some(item) = cursor.item() {
346 if item_origin.y() > bounds.max_y() {
347 break;
348 }
349
350 if let ListItem::Rendered(element) = item {
351 if let Some(rect) = element.rect_for_text_range(range_utf16.clone(), cx) {
352 return Some(rect);
353 }
354
355 item_origin.set_y(item_origin.y() + element.size().y());
356 cursor.next(&());
357 } else {
358 unreachable!();
359 }
360 }
361
362 None
363 }
364
365 fn debug(
366 &self,
367 bounds: RectF,
368 scroll_top: &Self::LayoutState,
369 _: &(),
370 cx: &DebugContext,
371 ) -> serde_json::Value {
372 let state = self.state.0.borrow_mut();
373 let visible_elements = state
374 .visible_elements(bounds, scroll_top)
375 .map(|e| e.0.debug(cx))
376 .collect::<Vec<_>>();
377 let visible_range = scroll_top.item_ix..(scroll_top.item_ix + visible_elements.len());
378 json!({
379 "visible_range": visible_range,
380 "visible_elements": visible_elements,
381 "scroll_top": state.logical_scroll_top.map(|top| (top.item_ix, top.offset_in_item)),
382 })
383 }
384}
385
386impl ListState {
387 pub fn new<F, V>(
388 element_count: usize,
389 orientation: Orientation,
390 overdraw: f32,
391 cx: &mut ViewContext<V>,
392 mut render_item: F,
393 ) -> Self
394 where
395 V: View,
396 F: 'static + FnMut(&mut V, usize, &mut RenderContext<V>) -> ElementBox,
397 {
398 let mut items = SumTree::new();
399 items.extend((0..element_count).map(|_| ListItem::Unrendered), &());
400 let handle = cx.weak_handle();
401 Self(Rc::new(RefCell::new(StateInner {
402 last_layout_width: None,
403 render_item: Box::new(move |ix, cx| {
404 let handle = handle.upgrade(cx)?;
405 Some(cx.render(&handle, |view, cx| render_item(view, ix, cx)))
406 }),
407 rendered_range: 0..0,
408 items,
409 logical_scroll_top: None,
410 orientation,
411 overdraw,
412 scroll_handler: None,
413 })))
414 }
415
416 pub fn reset(&self, element_count: usize) {
417 let state = &mut *self.0.borrow_mut();
418 state.rendered_range = 0..0;
419 state.logical_scroll_top = None;
420 state.items = SumTree::new();
421 state
422 .items
423 .extend((0..element_count).map(|_| ListItem::Unrendered), &());
424 }
425
426 pub fn splice(&self, old_range: Range<usize>, count: usize) {
427 let state = &mut *self.0.borrow_mut();
428
429 if let Some(ListOffset {
430 item_ix,
431 offset_in_item,
432 }) = state.logical_scroll_top.as_mut()
433 {
434 if old_range.contains(item_ix) {
435 *item_ix = old_range.start;
436 *offset_in_item = 0.;
437 } else if old_range.end <= *item_ix {
438 *item_ix = *item_ix - (old_range.end - old_range.start) + count;
439 }
440 }
441
442 let new_end = old_range.start + count;
443 if old_range.start < state.rendered_range.start {
444 state.rendered_range.start =
445 new_end + state.rendered_range.start.saturating_sub(old_range.end);
446 }
447 if old_range.start < state.rendered_range.end {
448 state.rendered_range.end =
449 new_end + state.rendered_range.end.saturating_sub(old_range.end);
450 }
451
452 let mut old_heights = state.items.cursor::<Count>();
453 let mut new_heights = old_heights.slice(&Count(old_range.start), Bias::Right, &());
454 old_heights.seek_forward(&Count(old_range.end), Bias::Right, &());
455
456 new_heights.extend((0..count).map(|_| ListItem::Unrendered), &());
457 new_heights.push_tree(old_heights.suffix(&()), &());
458 drop(old_heights);
459 state.items = new_heights;
460 }
461
462 pub fn set_scroll_handler(
463 &mut self,
464 handler: impl FnMut(Range<usize>, &mut EventContext) + 'static,
465 ) {
466 self.0.borrow_mut().scroll_handler = Some(Box::new(handler))
467 }
468}
469
470impl StateInner {
471 fn render_item(
472 &mut self,
473 ix: usize,
474 existing_element: Option<&ListItem>,
475 constraint: SizeConstraint,
476 cx: &mut LayoutContext,
477 ) -> Option<ElementRc> {
478 if let Some(ListItem::Rendered(element)) = existing_element {
479 Some(element.clone())
480 } else {
481 let mut element = (self.render_item)(ix, cx)?;
482 element.layout(constraint, cx);
483 Some(element.into())
484 }
485 }
486
487 fn visible_range(&self, height: f32, scroll_top: &ListOffset) -> Range<usize> {
488 let mut cursor = self.items.cursor::<ListItemSummary>();
489 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
490 let start_y = cursor.start().height + scroll_top.offset_in_item;
491 cursor.seek_forward(&Height(start_y + height), Bias::Left, &());
492 scroll_top.item_ix..cursor.start().count + 1
493 }
494
495 fn visible_elements<'a>(
496 &'a self,
497 bounds: RectF,
498 scroll_top: &ListOffset,
499 ) -> impl Iterator<Item = (ElementRc, Vector2F)> + 'a {
500 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
501 let mut cursor = self.items.cursor::<Count>();
502 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
503 std::iter::from_fn(move || {
504 while let Some(item) = cursor.item() {
505 if item_origin.y() > bounds.max_y() {
506 break;
507 }
508
509 if let ListItem::Rendered(element) = item {
510 let result = (element.clone(), item_origin);
511 item_origin.set_y(item_origin.y() + element.size().y());
512 cursor.next(&());
513 return Some(result);
514 }
515
516 cursor.next(&());
517 }
518
519 None
520 })
521 }
522
523 fn scroll(
524 &mut self,
525 scroll_top: &ListOffset,
526 height: f32,
527 mut delta: Vector2F,
528 precise: bool,
529 cx: &mut EventContext,
530 ) -> bool {
531 if !precise {
532 delta *= 20.;
533 }
534
535 let scroll_max = (self.items.summary().height - height).max(0.);
536 let new_scroll_top = (self.scroll_top(scroll_top) - delta.y())
537 .max(0.)
538 .min(scroll_max);
539
540 if self.orientation == Orientation::Bottom && new_scroll_top == scroll_max {
541 self.logical_scroll_top = None;
542 } else {
543 let mut cursor = self.items.cursor::<ListItemSummary>();
544 cursor.seek(&Height(new_scroll_top), Bias::Right, &());
545 let item_ix = cursor.start().count;
546 let offset_in_item = new_scroll_top - cursor.start().height;
547 self.logical_scroll_top = Some(ListOffset {
548 item_ix,
549 offset_in_item,
550 });
551 }
552
553 if self.scroll_handler.is_some() {
554 let visible_range = self.visible_range(height, scroll_top);
555 self.scroll_handler.as_mut().unwrap()(visible_range, cx);
556 }
557 cx.notify();
558
559 true
560 }
561
562 fn scroll_top(&self, logical_scroll_top: &ListOffset) -> f32 {
563 let mut cursor = self.items.cursor::<ListItemSummary>();
564 cursor.seek(&Count(logical_scroll_top.item_ix), Bias::Right, &());
565 cursor.start().height + logical_scroll_top.offset_in_item
566 }
567}
568
569impl ListItem {
570 fn remove(&self) -> Self {
571 match self {
572 ListItem::Unrendered => ListItem::Unrendered,
573 ListItem::Rendered(element) => ListItem::Removed(element.size().y()),
574 ListItem::Removed(height) => ListItem::Removed(*height),
575 }
576 }
577}
578
579impl sum_tree::Item for ListItem {
580 type Summary = ListItemSummary;
581
582 fn summary(&self) -> Self::Summary {
583 match self {
584 ListItem::Unrendered => ListItemSummary {
585 count: 1,
586 rendered_count: 0,
587 unrendered_count: 1,
588 height: 0.,
589 },
590 ListItem::Rendered(element) => ListItemSummary {
591 count: 1,
592 rendered_count: 1,
593 unrendered_count: 0,
594 height: element.size().y(),
595 },
596 ListItem::Removed(height) => ListItemSummary {
597 count: 1,
598 rendered_count: 0,
599 unrendered_count: 1,
600 height: *height,
601 },
602 }
603 }
604}
605
606impl sum_tree::Summary for ListItemSummary {
607 type Context = ();
608
609 fn add_summary(&mut self, summary: &Self, _: &()) {
610 self.count += summary.count;
611 self.rendered_count += summary.rendered_count;
612 self.unrendered_count += summary.unrendered_count;
613 self.height += summary.height;
614 }
615}
616
617impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Count {
618 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
619 self.0 += summary.count;
620 }
621}
622
623impl<'a> sum_tree::Dimension<'a, ListItemSummary> for RenderedCount {
624 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
625 self.0 += summary.rendered_count;
626 }
627}
628
629impl<'a> sum_tree::Dimension<'a, ListItemSummary> for UnrenderedCount {
630 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
631 self.0 += summary.unrendered_count;
632 }
633}
634
635impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Height {
636 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
637 self.0 += summary.height;
638 }
639}
640
641impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Count {
642 fn cmp(&self, other: &ListItemSummary, _: &()) -> std::cmp::Ordering {
643 self.0.partial_cmp(&other.count).unwrap()
644 }
645}
646
647impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Height {
648 fn cmp(&self, other: &ListItemSummary, _: &()) -> std::cmp::Ordering {
649 self.0.partial_cmp(&other.height).unwrap()
650 }
651}
652
653#[cfg(test)]
654mod tests {
655 use super::*;
656 use crate::{elements::Empty, geometry::vector::vec2f, Entity};
657 use rand::prelude::*;
658 use std::env;
659
660 #[crate::test(self)]
661 fn test_layout(cx: &mut crate::MutableAppContext) {
662 let mut presenter = cx.build_presenter(0, 0., Default::default());
663 let (_, view) = cx.add_window(Default::default(), |_| TestView);
664 let constraint = SizeConstraint::new(vec2f(0., 0.), vec2f(100., 40.));
665
666 let elements = Rc::new(RefCell::new(vec![(0, 20.), (1, 30.), (2, 100.)]));
667
668 let state = view.update(cx, |_, cx| {
669 ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, cx, {
670 let elements = elements.clone();
671 move |_, ix, _| {
672 let (id, height) = elements.borrow()[ix];
673 TestElement::new(id, height).boxed()
674 }
675 })
676 });
677
678 let mut list = List::new(state.clone());
679 let (size, _) = list.layout(
680 constraint,
681 &mut presenter.build_layout_context(vec2f(100., 40.), false, cx),
682 );
683 assert_eq!(size, vec2f(100., 40.));
684 assert_eq!(
685 state.0.borrow().items.summary().clone(),
686 ListItemSummary {
687 count: 3,
688 rendered_count: 3,
689 unrendered_count: 0,
690 height: 150.
691 }
692 );
693
694 state.0.borrow_mut().scroll(
695 &ListOffset {
696 item_ix: 0,
697 offset_in_item: 0.,
698 },
699 40.,
700 vec2f(0., -54.),
701 true,
702 &mut presenter.build_event_context(&mut Default::default(), cx),
703 );
704 let (_, logical_scroll_top) = list.layout(
705 constraint,
706 &mut presenter.build_layout_context(vec2f(100., 40.), false, cx),
707 );
708 assert_eq!(
709 logical_scroll_top,
710 ListOffset {
711 item_ix: 2,
712 offset_in_item: 4.
713 }
714 );
715 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 54.);
716
717 elements.borrow_mut().splice(1..2, vec![(3, 40.), (4, 50.)]);
718 elements.borrow_mut().push((5, 60.));
719 state.splice(1..2, 2);
720 state.splice(4..4, 1);
721 assert_eq!(
722 state.0.borrow().items.summary().clone(),
723 ListItemSummary {
724 count: 5,
725 rendered_count: 2,
726 unrendered_count: 3,
727 height: 120.
728 }
729 );
730
731 let (size, logical_scroll_top) = list.layout(
732 constraint,
733 &mut presenter.build_layout_context(vec2f(100., 40.), false, cx),
734 );
735 assert_eq!(size, vec2f(100., 40.));
736 assert_eq!(
737 state.0.borrow().items.summary().clone(),
738 ListItemSummary {
739 count: 5,
740 rendered_count: 5,
741 unrendered_count: 0,
742 height: 270.
743 }
744 );
745 assert_eq!(
746 logical_scroll_top,
747 ListOffset {
748 item_ix: 3,
749 offset_in_item: 4.
750 }
751 );
752 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 114.);
753 }
754
755 #[crate::test(self, iterations = 10, seed = 0)]
756 fn test_random(cx: &mut crate::MutableAppContext, mut rng: StdRng) {
757 let operations = env::var("OPERATIONS")
758 .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
759 .unwrap_or(10);
760
761 let (_, view) = cx.add_window(Default::default(), |_| TestView);
762 let mut presenter = cx.build_presenter(0, 0., Default::default());
763 let mut next_id = 0;
764 let elements = Rc::new(RefCell::new(
765 (0..rng.gen_range(0..=20))
766 .map(|_| {
767 let id = next_id;
768 next_id += 1;
769 (id, rng.gen_range(0..=200) as f32 / 2.0)
770 })
771 .collect::<Vec<_>>(),
772 ));
773 let orientation = *[Orientation::Top, Orientation::Bottom]
774 .choose(&mut rng)
775 .unwrap();
776 let overdraw = rng.gen_range(1..=100) as f32;
777
778 let state = view.update(cx, |_, cx| {
779 ListState::new(elements.borrow().len(), orientation, overdraw, cx, {
780 let elements = elements.clone();
781 move |_, ix, _| {
782 let (id, height) = elements.borrow()[ix];
783 TestElement::new(id, height).boxed()
784 }
785 })
786 });
787
788 let mut width = rng.gen_range(0..=2000) as f32 / 2.;
789 let mut height = rng.gen_range(0..=2000) as f32 / 2.;
790 log::info!("orientation: {:?}", orientation);
791 log::info!("overdraw: {}", overdraw);
792 log::info!("elements: {:?}", elements.borrow());
793 log::info!("size: ({:?}, {:?})", width, height);
794 log::info!("==================");
795
796 let mut last_logical_scroll_top = None;
797 for _ in 0..operations {
798 match rng.gen_range(0..=100) {
799 0..=29 if last_logical_scroll_top.is_some() => {
800 let delta = vec2f(0., rng.gen_range(-overdraw..=overdraw));
801 log::info!(
802 "Scrolling by {:?}, previous scroll top: {:?}",
803 delta,
804 last_logical_scroll_top.unwrap()
805 );
806 state.0.borrow_mut().scroll(
807 last_logical_scroll_top.as_ref().unwrap(),
808 height,
809 delta,
810 true,
811 &mut presenter.build_event_context(&mut Default::default(), cx),
812 );
813 }
814 30..=34 => {
815 width = rng.gen_range(0..=2000) as f32 / 2.;
816 log::info!("changing width: {:?}", width);
817 }
818 35..=54 => {
819 height = rng.gen_range(0..=1000) as f32 / 2.;
820 log::info!("changing height: {:?}", height);
821 }
822 _ => {
823 let mut elements = elements.borrow_mut();
824 let end_ix = rng.gen_range(0..=elements.len());
825 let start_ix = rng.gen_range(0..=end_ix);
826 let new_elements = (0..rng.gen_range(0..10))
827 .map(|_| {
828 let id = next_id;
829 next_id += 1;
830 (id, rng.gen_range(0..=200) as f32 / 2.)
831 })
832 .collect::<Vec<_>>();
833 log::info!("splice({:?}, {:?})", start_ix..end_ix, new_elements);
834 state.splice(start_ix..end_ix, new_elements.len());
835 elements.splice(start_ix..end_ix, new_elements);
836 for (ix, item) in state.0.borrow().items.cursor::<()>().enumerate() {
837 if let ListItem::Rendered(element) = item {
838 let (expected_id, _) = elements[ix];
839 element.with_metadata(|metadata: Option<&usize>| {
840 assert_eq!(*metadata.unwrap(), expected_id);
841 });
842 }
843 }
844 }
845 }
846
847 let mut list = List::new(state.clone());
848 let window_size = vec2f(width, height);
849 let (size, logical_scroll_top) = list.layout(
850 SizeConstraint::new(vec2f(0., 0.), window_size),
851 &mut presenter.build_layout_context(window_size, false, cx),
852 );
853 assert_eq!(size, window_size);
854 last_logical_scroll_top = Some(logical_scroll_top);
855
856 let state = state.0.borrow();
857 log::info!("items {:?}", state.items.items(&()));
858
859 let scroll_top = state.scroll_top(&logical_scroll_top);
860 let rendered_top = (scroll_top - overdraw).max(0.);
861 let rendered_bottom = scroll_top + height + overdraw;
862 let mut item_top = 0.;
863
864 log::info!(
865 "rendered top {:?}, rendered bottom {:?}, scroll top {:?}",
866 rendered_top,
867 rendered_bottom,
868 scroll_top,
869 );
870
871 let mut first_rendered_element_top = None;
872 let mut last_rendered_element_bottom = None;
873 assert_eq!(state.items.summary().count, elements.borrow().len());
874 for (ix, item) in state.items.cursor::<()>().enumerate() {
875 match item {
876 ListItem::Unrendered => {
877 let item_bottom = item_top;
878 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
879 item_top = item_bottom;
880 }
881 ListItem::Removed(height) => {
882 let (id, expected_height) = elements.borrow()[ix];
883 assert_eq!(
884 *height, expected_height,
885 "element {} height didn't match",
886 id
887 );
888 let item_bottom = item_top + height;
889 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
890 item_top = item_bottom;
891 }
892 ListItem::Rendered(element) => {
893 let (expected_id, expected_height) = elements.borrow()[ix];
894 element.with_metadata(|metadata: Option<&usize>| {
895 assert_eq!(*metadata.unwrap(), expected_id);
896 });
897 assert_eq!(element.size().y(), expected_height);
898 let item_bottom = item_top + element.size().y();
899 first_rendered_element_top.get_or_insert(item_top);
900 last_rendered_element_bottom = Some(item_bottom);
901 assert!(item_bottom > rendered_top || item_top < rendered_bottom);
902 item_top = item_bottom;
903 }
904 }
905 }
906
907 match orientation {
908 Orientation::Top => {
909 if let Some(first_rendered_element_top) = first_rendered_element_top {
910 assert!(first_rendered_element_top <= scroll_top);
911 }
912 }
913 Orientation::Bottom => {
914 if let Some(last_rendered_element_bottom) = last_rendered_element_bottom {
915 assert!(last_rendered_element_bottom >= scroll_top + height);
916 }
917 }
918 }
919 }
920 }
921
922 struct TestView;
923
924 impl Entity for TestView {
925 type Event = ();
926 }
927
928 impl View for TestView {
929 fn ui_name() -> &'static str {
930 "TestView"
931 }
932
933 fn render(&mut self, _: &mut RenderContext<'_, Self>) -> ElementBox {
934 Empty::new().boxed()
935 }
936 }
937
938 struct TestElement {
939 id: usize,
940 size: Vector2F,
941 }
942
943 impl TestElement {
944 fn new(id: usize, height: f32) -> Self {
945 Self {
946 id,
947 size: vec2f(100., height),
948 }
949 }
950 }
951
952 impl Element for TestElement {
953 type LayoutState = ();
954 type PaintState = ();
955
956 fn layout(&mut self, _: SizeConstraint, _: &mut LayoutContext) -> (Vector2F, ()) {
957 (self.size, ())
958 }
959
960 fn paint(&mut self, _: RectF, _: RectF, _: &mut (), _: &mut PaintContext) {
961 todo!()
962 }
963
964 fn dispatch_event(
965 &mut self,
966 _: &Event,
967 _: RectF,
968 _: RectF,
969 _: &mut (),
970 _: &mut (),
971 _: &mut EventContext,
972 ) -> bool {
973 todo!()
974 }
975
976 fn rect_for_text_range(
977 &self,
978 _: Range<usize>,
979 _: RectF,
980 _: RectF,
981 _: &Self::LayoutState,
982 _: &Self::PaintState,
983 _: &MeasurementContext,
984 ) -> Option<RectF> {
985 todo!()
986 }
987
988 fn debug(&self, _: RectF, _: &(), _: &(), _: &DebugContext) -> serde_json::Value {
989 self.id.into()
990 }
991
992 fn metadata(&self) -> Option<&dyn std::any::Any> {
993 Some(&self.id)
994 }
995 }
996}