1use crate::{
2 geometry::{
3 rect::RectF,
4 vector::{vec2f, Vector2F},
5 },
6 json::json,
7 sum_tree::{self, Bias, SumTree},
8 DebugContext, Element, ElementBox, ElementRc, Event, EventContext, LayoutContext, PaintContext,
9 SizeConstraint,
10};
11use std::{cell::RefCell, collections::VecDeque, ops::Range, rc::Rc};
12
13pub struct List {
14 state: ListState,
15}
16
17#[derive(Clone)]
18pub struct ListState(Rc<RefCell<StateInner>>);
19
20#[derive(Clone, Copy, Debug, Eq, PartialEq)]
21pub enum Orientation {
22 Top,
23 Bottom,
24}
25
26struct StateInner {
27 last_layout_width: Option<f32>,
28 render_item: Box<dyn FnMut(usize, &mut LayoutContext) -> ElementBox>,
29 rendered_range: Range<usize>,
30 items: SumTree<ListItem>,
31 logical_scroll_top: Option<ListOffset>,
32 orientation: Orientation,
33 overdraw: f32,
34 scroll_handler: Option<Box<dyn FnMut(Range<usize>, &mut EventContext)>>,
35}
36
37#[derive(Clone, Copy, Debug, Default, PartialEq)]
38pub struct ListOffset {
39 item_ix: usize,
40 offset_in_item: f32,
41}
42
43#[derive(Clone)]
44enum ListItem {
45 Unrendered,
46 Rendered(ElementRc),
47 Removed(f32),
48}
49
50impl std::fmt::Debug for ListItem {
51 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
52 match self {
53 Self::Unrendered => write!(f, "Unrendered"),
54 Self::Rendered(_) => f.debug_tuple("Rendered").finish(),
55 Self::Removed(height) => f.debug_tuple("Removed").field(height).finish(),
56 }
57 }
58}
59
60#[derive(Clone, Debug, Default, PartialEq)]
61struct ListItemSummary {
62 count: usize,
63 rendered_count: usize,
64 unrendered_count: usize,
65 height: f32,
66}
67
68#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
69struct Count(usize);
70
71#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
72struct RenderedCount(usize);
73
74#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
75struct UnrenderedCount(usize);
76
77#[derive(Clone, Debug, Default)]
78struct Height(f32);
79
80impl List {
81 pub fn new(state: ListState) -> Self {
82 Self { state }
83 }
84}
85
86impl Element for List {
87 type LayoutState = ListOffset;
88 type PaintState = ();
89
90 fn layout(
91 &mut self,
92 constraint: SizeConstraint,
93 cx: &mut LayoutContext,
94 ) -> (Vector2F, Self::LayoutState) {
95 let state = &mut *self.state.0.borrow_mut();
96 let size = constraint.max;
97 let mut item_constraint = constraint;
98 item_constraint.min.set_y(0.);
99 item_constraint.max.set_y(f32::INFINITY);
100
101 if cx.refreshing || state.last_layout_width != Some(size.x()) {
102 state.rendered_range = 0..0;
103 state.items = SumTree::from_iter(
104 (0..state.items.summary().count).map(|_| ListItem::Unrendered),
105 &(),
106 )
107 }
108
109 let old_items = state.items.clone();
110 let mut new_items = SumTree::new();
111 let mut rendered_items = VecDeque::new();
112 let mut rendered_height = 0.;
113 let mut scroll_top = state
114 .logical_scroll_top
115 .unwrap_or_else(|| match state.orientation {
116 Orientation::Top => ListOffset {
117 item_ix: 0,
118 offset_in_item: 0.,
119 },
120 Orientation::Bottom => ListOffset {
121 item_ix: state.items.summary().count,
122 offset_in_item: 0.,
123 },
124 });
125
126 // Render items after the scroll top, including those in the trailing overdraw.
127 let mut cursor = old_items.cursor::<Count, ()>();
128 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
129 for (ix, item) in cursor.by_ref().enumerate() {
130 if rendered_height - scroll_top.offset_in_item >= size.y() + state.overdraw {
131 break;
132 }
133
134 let element = state.render_item(scroll_top.item_ix + ix, item, item_constraint, cx);
135 rendered_height += element.size().y();
136 rendered_items.push_back(ListItem::Rendered(element));
137 }
138
139 // Prepare to start walking upward from the item at the scroll top.
140 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
141
142 // If the rendered items do not fill the visible region, then adjust
143 // the scroll top upward.
144 if rendered_height - scroll_top.offset_in_item < size.y() {
145 while rendered_height < size.y() {
146 cursor.prev(&());
147 if let Some(item) = cursor.item() {
148 let element =
149 state.render_item(cursor.seek_start().0, item, item_constraint, cx);
150 rendered_height += element.size().y();
151 rendered_items.push_front(ListItem::Rendered(element));
152 } else {
153 break;
154 }
155 }
156
157 scroll_top = ListOffset {
158 item_ix: cursor.seek_start().0,
159 offset_in_item: rendered_height - size.y(),
160 };
161
162 match state.orientation {
163 Orientation::Top => {
164 scroll_top.offset_in_item = scroll_top.offset_in_item.max(0.);
165 state.logical_scroll_top = Some(scroll_top);
166 }
167 Orientation::Bottom => {
168 scroll_top = ListOffset {
169 item_ix: cursor.seek_start().0,
170 offset_in_item: rendered_height - size.y(),
171 };
172 state.logical_scroll_top = None;
173 }
174 };
175 }
176
177 // Render items in the leading overdraw.
178 let mut leading_overdraw = scroll_top.offset_in_item;
179 while leading_overdraw < state.overdraw {
180 cursor.prev(&());
181 if let Some(item) = cursor.item() {
182 let element = state.render_item(cursor.seek_start().0, item, item_constraint, cx);
183 leading_overdraw += element.size().y();
184 rendered_items.push_front(ListItem::Rendered(element));
185 } else {
186 break;
187 }
188 }
189
190 let new_rendered_range =
191 cursor.seek_start().0..(cursor.seek_start().0 + rendered_items.len());
192
193 let mut cursor = old_items.cursor::<Count, ()>();
194
195 if state.rendered_range.start < new_rendered_range.start {
196 new_items.push_tree(
197 cursor.slice(&Count(state.rendered_range.start), Bias::Right, &()),
198 &(),
199 );
200 let remove_to = state.rendered_range.end.min(new_rendered_range.start);
201 while cursor.seek_start().0 < remove_to {
202 new_items.push(cursor.item().unwrap().remove(), &());
203 cursor.next(&());
204 }
205 }
206 new_items.push_tree(
207 cursor.slice(&Count(new_rendered_range.start), Bias::Right, &()),
208 &(),
209 );
210
211 new_items.extend(rendered_items, &());
212 cursor.seek(&Count(new_rendered_range.end), Bias::Right, &());
213
214 if new_rendered_range.end < state.rendered_range.start {
215 new_items.push_tree(
216 cursor.slice(&Count(state.rendered_range.start), Bias::Right, &()),
217 &(),
218 );
219 }
220 while cursor.seek_start().0 < state.rendered_range.end {
221 new_items.push(cursor.item().unwrap().remove(), &());
222 cursor.next(&());
223 }
224
225 new_items.push_tree(cursor.suffix(&()), &());
226
227 state.items = new_items;
228 state.rendered_range = new_rendered_range;
229 state.last_layout_width = Some(size.x());
230 (size, scroll_top)
231 }
232
233 fn paint(&mut self, bounds: RectF, scroll_top: &mut ListOffset, cx: &mut PaintContext) {
234 cx.scene.push_layer(Some(bounds));
235
236 let state = &mut *self.state.0.borrow_mut();
237 for (mut element, origin) in state.visible_elements(bounds, scroll_top) {
238 element.paint(origin, cx);
239 }
240
241 cx.scene.pop_layer();
242 }
243
244 fn dispatch_event(
245 &mut self,
246 event: &Event,
247 bounds: RectF,
248 scroll_top: &mut ListOffset,
249 _: &mut (),
250 cx: &mut EventContext,
251 ) -> bool {
252 let mut handled = false;
253
254 let mut state = self.state.0.borrow_mut();
255 for (mut element, _) in state.visible_elements(bounds, scroll_top) {
256 handled = element.dispatch_event(event, cx) || handled;
257 }
258
259 match event {
260 Event::ScrollWheel {
261 position,
262 delta,
263 precise,
264 } => {
265 if bounds.contains_point(*position) {
266 if state.scroll(scroll_top, bounds.height(), *delta, *precise, cx) {
267 handled = true;
268 }
269 }
270 }
271 _ => {}
272 }
273
274 handled
275 }
276
277 fn debug(
278 &self,
279 bounds: RectF,
280 scroll_top: &Self::LayoutState,
281 _: &(),
282 cx: &DebugContext,
283 ) -> serde_json::Value {
284 let state = self.state.0.borrow_mut();
285 let visible_elements = state
286 .visible_elements(bounds, scroll_top)
287 .map(|e| e.0.debug(cx))
288 .collect::<Vec<_>>();
289 let visible_range = scroll_top.item_ix..(scroll_top.item_ix + visible_elements.len());
290 json!({
291 "visible_range": visible_range,
292 "visible_elements": visible_elements,
293 "scroll_top": state.logical_scroll_top.map(|top| (top.item_ix, top.offset_in_item)),
294 })
295 }
296}
297
298impl ListState {
299 pub fn new<F>(
300 element_count: usize,
301 orientation: Orientation,
302 overdraw: f32,
303 render_item: F,
304 ) -> Self
305 where
306 F: 'static + FnMut(usize, &mut LayoutContext) -> ElementBox,
307 {
308 let mut items = SumTree::new();
309 items.extend((0..element_count).map(|_| ListItem::Unrendered), &());
310 Self(Rc::new(RefCell::new(StateInner {
311 last_layout_width: None,
312 render_item: Box::new(render_item),
313 rendered_range: 0..0,
314 items,
315 logical_scroll_top: None,
316 orientation,
317 overdraw,
318 scroll_handler: None,
319 })))
320 }
321
322 pub fn reset(&self, element_count: usize) {
323 let state = &mut *self.0.borrow_mut();
324 state.logical_scroll_top = None;
325 state.items = SumTree::new();
326 state
327 .items
328 .extend((0..element_count).map(|_| ListItem::Unrendered), &());
329 }
330
331 pub fn splice(&self, old_range: Range<usize>, count: usize) {
332 let state = &mut *self.0.borrow_mut();
333
334 if let Some(ListOffset {
335 item_ix,
336 offset_in_item,
337 }) = state.logical_scroll_top.as_mut()
338 {
339 if old_range.contains(item_ix) {
340 *item_ix = old_range.start;
341 *offset_in_item = 0.;
342 } else if old_range.end <= *item_ix {
343 *item_ix = *item_ix - (old_range.end - old_range.start) + count;
344 }
345 }
346
347 let new_end = old_range.start + count;
348 if old_range.start < state.rendered_range.start {
349 state.rendered_range.start =
350 new_end + state.rendered_range.start.saturating_sub(old_range.end);
351 }
352 if old_range.start < state.rendered_range.end {
353 state.rendered_range.end =
354 new_end + state.rendered_range.end.saturating_sub(old_range.end);
355 }
356
357 let mut old_heights = state.items.cursor::<Count, ()>();
358 let mut new_heights = old_heights.slice(&Count(old_range.start), Bias::Right, &());
359 old_heights.seek_forward(&Count(old_range.end), Bias::Right, &());
360
361 new_heights.extend((0..count).map(|_| ListItem::Unrendered), &());
362 new_heights.push_tree(old_heights.suffix(&()), &());
363 drop(old_heights);
364 state.items = new_heights;
365 }
366
367 pub fn set_scroll_handler(
368 &mut self,
369 handler: impl FnMut(Range<usize>, &mut EventContext) + 'static,
370 ) {
371 self.0.borrow_mut().scroll_handler = Some(Box::new(handler))
372 }
373}
374
375impl StateInner {
376 fn render_item(
377 &mut self,
378 ix: usize,
379 existing_item: &ListItem,
380 constraint: SizeConstraint,
381 cx: &mut LayoutContext,
382 ) -> ElementRc {
383 if let ListItem::Rendered(element) = existing_item {
384 element.clone()
385 } else {
386 let mut element = (self.render_item)(ix, cx);
387 element.layout(constraint, cx);
388 element.into()
389 }
390 }
391
392 fn visible_range(&self, height: f32, scroll_top: &ListOffset) -> Range<usize> {
393 let mut cursor = self.items.cursor::<Count, Height>();
394 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
395 let start_y = cursor.sum_start().0 + scroll_top.offset_in_item;
396 let mut cursor = cursor.swap_dimensions();
397 cursor.seek_forward(&Height(start_y + height), Bias::Left, &());
398 scroll_top.item_ix..cursor.sum_start().0 + 1
399 }
400
401 fn visible_elements<'a>(
402 &'a self,
403 bounds: RectF,
404 scroll_top: &ListOffset,
405 ) -> impl Iterator<Item = (ElementRc, Vector2F)> + 'a {
406 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
407 let mut cursor = self.items.cursor::<Count, ()>();
408 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
409 std::iter::from_fn(move || {
410 while let Some(item) = cursor.item() {
411 if item_origin.y() > bounds.max_y() {
412 break;
413 }
414
415 if let ListItem::Rendered(element) = item {
416 let result = (element.clone(), item_origin);
417 item_origin.set_y(item_origin.y() + element.size().y());
418 cursor.next(&());
419 return Some(result);
420 }
421
422 cursor.next(&());
423 }
424
425 None
426 })
427 }
428
429 fn scroll(
430 &mut self,
431 scroll_top: &ListOffset,
432 height: f32,
433 mut delta: Vector2F,
434 precise: bool,
435 cx: &mut EventContext,
436 ) -> bool {
437 if !precise {
438 delta *= 20.;
439 }
440
441 let scroll_max = (self.items.summary().height - height).max(0.);
442 let new_scroll_top = (self.scroll_top(scroll_top) - delta.y())
443 .max(0.)
444 .min(scroll_max);
445
446 if self.orientation == Orientation::Bottom && new_scroll_top == scroll_max {
447 self.logical_scroll_top = None;
448 } else {
449 let mut cursor = self.items.cursor::<Height, Count>();
450 cursor.seek(&Height(new_scroll_top), Bias::Right, &());
451 let item_ix = cursor.sum_start().0;
452 let offset_in_item = new_scroll_top - cursor.seek_start().0;
453 self.logical_scroll_top = Some(ListOffset {
454 item_ix,
455 offset_in_item,
456 });
457 }
458
459 if self.scroll_handler.is_some() {
460 let visible_range = self.visible_range(height, scroll_top);
461 self.scroll_handler.as_mut().unwrap()(visible_range, cx);
462 }
463 cx.notify();
464
465 true
466 }
467
468 fn scroll_top(&self, logical_scroll_top: &ListOffset) -> f32 {
469 let mut cursor = self.items.cursor::<Count, Height>();
470 cursor.seek(&Count(logical_scroll_top.item_ix), Bias::Right, &());
471 cursor.sum_start().0 + logical_scroll_top.offset_in_item
472 }
473}
474
475impl ListItem {
476 fn remove(&self) -> Self {
477 match self {
478 ListItem::Unrendered => ListItem::Unrendered,
479 ListItem::Rendered(element) => ListItem::Removed(element.size().y()),
480 ListItem::Removed(height) => ListItem::Removed(*height),
481 }
482 }
483}
484
485impl sum_tree::Item for ListItem {
486 type Summary = ListItemSummary;
487
488 fn summary(&self) -> Self::Summary {
489 match self {
490 ListItem::Unrendered => ListItemSummary {
491 count: 1,
492 rendered_count: 0,
493 unrendered_count: 1,
494 height: 0.,
495 },
496 ListItem::Rendered(element) => ListItemSummary {
497 count: 1,
498 rendered_count: 1,
499 unrendered_count: 0,
500 height: element.size().y(),
501 },
502 ListItem::Removed(height) => ListItemSummary {
503 count: 1,
504 rendered_count: 0,
505 unrendered_count: 1,
506 height: *height,
507 },
508 }
509 }
510}
511
512impl sum_tree::Summary for ListItemSummary {
513 type Context = ();
514
515 fn add_summary(&mut self, summary: &Self, _: &()) {
516 self.count += summary.count;
517 self.rendered_count += summary.rendered_count;
518 self.unrendered_count += summary.unrendered_count;
519 self.height += summary.height;
520 }
521}
522
523impl<'a> sum_tree::Dimension<'a, ListItemSummary> for ListItemSummary {
524 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
525 sum_tree::Summary::add_summary(self, summary, &());
526 }
527}
528
529impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Count {
530 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
531 self.0 += summary.count;
532 }
533}
534
535impl<'a> sum_tree::Dimension<'a, ListItemSummary> for RenderedCount {
536 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
537 self.0 += summary.rendered_count;
538 }
539}
540
541impl<'a> sum_tree::Dimension<'a, ListItemSummary> for UnrenderedCount {
542 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
543 self.0 += summary.unrendered_count;
544 }
545}
546
547impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Height {
548 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
549 self.0 += summary.height;
550 }
551}
552
553impl<'a> sum_tree::SeekDimension<'a, ListItemSummary> for Height {
554 fn cmp(&self, other: &Self, _: &()) -> std::cmp::Ordering {
555 self.0.partial_cmp(&other.0).unwrap()
556 }
557}
558
559#[cfg(test)]
560mod tests {
561 use super::*;
562 use crate::geometry::vector::vec2f;
563 use rand::prelude::*;
564 use std::env;
565
566 #[crate::test(self)]
567 fn test_layout(cx: &mut crate::MutableAppContext) {
568 let mut presenter = cx.build_presenter(0, 0.);
569 let constraint = SizeConstraint::new(vec2f(0., 0.), vec2f(100., 40.));
570
571 let elements = Rc::new(RefCell::new(vec![(0, 20.), (1, 30.), (2, 100.)]));
572 let state = ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, {
573 let elements = elements.clone();
574 move |ix, _| {
575 let (id, height) = elements.borrow()[ix];
576 TestElement::new(id, height).boxed()
577 }
578 });
579
580 let mut list = List::new(state.clone());
581 let (size, _) = list.layout(constraint, &mut presenter.build_layout_context(false, cx));
582 assert_eq!(size, vec2f(100., 40.));
583 assert_eq!(
584 state.0.borrow().items.summary(),
585 ListItemSummary {
586 count: 3,
587 rendered_count: 3,
588 unrendered_count: 0,
589 height: 150.
590 }
591 );
592
593 state.0.borrow_mut().scroll(
594 &ListOffset {
595 item_ix: 0,
596 offset_in_item: 0.,
597 },
598 40.,
599 vec2f(0., 54.),
600 true,
601 &mut presenter.build_event_context(cx),
602 );
603 let (_, logical_scroll_top) =
604 list.layout(constraint, &mut presenter.build_layout_context(false, cx));
605 assert_eq!(
606 logical_scroll_top,
607 ListOffset {
608 item_ix: 2,
609 offset_in_item: 4.
610 }
611 );
612 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 54.);
613
614 elements.borrow_mut().splice(1..2, vec![(3, 40.), (4, 50.)]);
615 elements.borrow_mut().push((5, 60.));
616 state.splice(1..2, 2);
617 state.splice(4..4, 1);
618 assert_eq!(
619 state.0.borrow().items.summary(),
620 ListItemSummary {
621 count: 5,
622 rendered_count: 2,
623 unrendered_count: 3,
624 height: 120.
625 }
626 );
627
628 let (size, logical_scroll_top) =
629 list.layout(constraint, &mut presenter.build_layout_context(false, cx));
630 assert_eq!(size, vec2f(100., 40.));
631 assert_eq!(
632 state.0.borrow().items.summary(),
633 ListItemSummary {
634 count: 5,
635 rendered_count: 5,
636 unrendered_count: 0,
637 height: 270.
638 }
639 );
640 assert_eq!(
641 logical_scroll_top,
642 ListOffset {
643 item_ix: 3,
644 offset_in_item: 4.
645 }
646 );
647 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 114.);
648 }
649
650 #[crate::test(self, iterations = 10000, seed = 0)]
651 fn test_random(cx: &mut crate::MutableAppContext, mut rng: StdRng) {
652 let operations = env::var("OPERATIONS")
653 .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
654 .unwrap_or(10);
655
656 let mut presenter = cx.build_presenter(0, 0.);
657 let mut next_id = 0;
658 let elements = Rc::new(RefCell::new(
659 (0..rng.gen_range(0..=20))
660 .map(|_| {
661 let id = next_id;
662 next_id += 1;
663 (id, rng.gen_range(0..=200) as f32 / 2.0)
664 })
665 .collect::<Vec<_>>(),
666 ));
667 let orientation = *[Orientation::Top, Orientation::Bottom]
668 .choose(&mut rng)
669 .unwrap();
670 let overdraw = rng.gen_range(1..=100) as f32;
671 let state = ListState::new(elements.borrow().len(), orientation, overdraw, {
672 let elements = elements.clone();
673 move |ix, _| {
674 let (id, height) = elements.borrow()[ix];
675 TestElement::new(id, height).boxed()
676 }
677 });
678
679 let mut width = rng.gen_range(0..=2000) as f32 / 2.;
680 let mut height = rng.gen_range(0..=2000) as f32 / 2.;
681 log::info!("orientation: {:?}", orientation);
682 log::info!("overdraw: {}", overdraw);
683 log::info!("elements: {:?}", elements.borrow());
684 log::info!("size: ({:?}, {:?})", width, height);
685 log::info!("==================");
686
687 let mut last_logical_scroll_top = None;
688 for _ in 0..operations {
689 match rng.gen_range(0..=100) {
690 0..=29 if last_logical_scroll_top.is_some() => {
691 let delta = vec2f(0., rng.gen_range(-overdraw..=overdraw));
692 log::info!(
693 "Scrolling by {:?}, previous scroll top: {:?}",
694 delta,
695 last_logical_scroll_top.unwrap()
696 );
697 state.0.borrow_mut().scroll(
698 last_logical_scroll_top.as_ref().unwrap(),
699 height,
700 delta,
701 true,
702 &mut presenter.build_event_context(cx),
703 );
704 }
705 30..=34 => {
706 width = rng.gen_range(0..=2000) as f32 / 2.;
707 log::info!("changing width: {:?}", width);
708 }
709 35..=54 => {
710 height = rng.gen_range(0..=1000) as f32 / 2.;
711 log::info!("changing height: {:?}", height);
712 }
713 _ => {
714 let mut elements = elements.borrow_mut();
715 let end_ix = rng.gen_range(0..=elements.len());
716 let start_ix = rng.gen_range(0..=end_ix);
717 let new_elements = (0..rng.gen_range(0..10))
718 .map(|_| {
719 let id = next_id;
720 next_id += 1;
721 (id, rng.gen_range(0..=200) as f32 / 2.)
722 })
723 .collect::<Vec<_>>();
724 log::info!("splice({:?}, {:?})", start_ix..end_ix, new_elements);
725 state.splice(start_ix..end_ix, new_elements.len());
726 elements.splice(start_ix..end_ix, new_elements);
727 for (ix, item) in state.0.borrow().items.cursor::<(), ()>().enumerate() {
728 if let ListItem::Rendered(element) = item {
729 let (expected_id, _) = elements[ix];
730 element.with_metadata(|metadata: Option<&usize>| {
731 assert_eq!(*metadata.unwrap(), expected_id);
732 });
733 }
734 }
735 }
736 }
737
738 let mut list = List::new(state.clone());
739 let (size, logical_scroll_top) = list.layout(
740 SizeConstraint::new(vec2f(0., 0.), vec2f(width, height)),
741 &mut presenter.build_layout_context(false, cx),
742 );
743 assert_eq!(size, vec2f(width, height));
744 last_logical_scroll_top = Some(logical_scroll_top);
745
746 let state = state.0.borrow();
747 log::info!("items {:?}", state.items.items(&()));
748
749 let scroll_top = state.scroll_top(&logical_scroll_top);
750 let rendered_top = (scroll_top - overdraw).max(0.);
751 let rendered_bottom = scroll_top + height + overdraw;
752 let mut item_top = 0.;
753
754 log::info!(
755 "rendered top {:?}, rendered bottom {:?}, scroll top {:?}",
756 rendered_top,
757 rendered_bottom,
758 scroll_top,
759 );
760
761 let mut first_rendered_element_top = None;
762 let mut last_rendered_element_bottom = None;
763 assert_eq!(state.items.summary().count, elements.borrow().len());
764 for (ix, item) in state.items.cursor::<(), ()>().enumerate() {
765 match item {
766 ListItem::Unrendered => {
767 let item_bottom = item_top;
768 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
769 item_top = item_bottom;
770 }
771 ListItem::Removed(height) => {
772 let (id, expected_height) = elements.borrow()[ix];
773 assert_eq!(
774 *height, expected_height,
775 "element {} height didn't match",
776 id
777 );
778 let item_bottom = item_top + height;
779 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
780 item_top = item_bottom;
781 }
782 ListItem::Rendered(element) => {
783 let (expected_id, expected_height) = elements.borrow()[ix];
784 element.with_metadata(|metadata: Option<&usize>| {
785 assert_eq!(*metadata.unwrap(), expected_id);
786 });
787 assert_eq!(element.size().y(), expected_height);
788 let item_bottom = item_top + element.size().y();
789 first_rendered_element_top.get_or_insert(item_top);
790 last_rendered_element_bottom = Some(item_bottom);
791 assert!(item_bottom > rendered_top || item_top < rendered_bottom);
792 item_top = item_bottom;
793 }
794 }
795 }
796
797 match orientation {
798 Orientation::Top => {
799 if let Some(first_rendered_element_top) = first_rendered_element_top {
800 assert!(first_rendered_element_top <= scroll_top);
801 }
802 }
803 Orientation::Bottom => {
804 if let Some(last_rendered_element_bottom) = last_rendered_element_bottom {
805 assert!(last_rendered_element_bottom >= scroll_top + height);
806 }
807 }
808 }
809 }
810 }
811
812 struct TestElement {
813 id: usize,
814 size: Vector2F,
815 }
816
817 impl TestElement {
818 fn new(id: usize, height: f32) -> Self {
819 Self {
820 id,
821 size: vec2f(100., height),
822 }
823 }
824 }
825
826 impl Element for TestElement {
827 type LayoutState = ();
828 type PaintState = ();
829
830 fn layout(&mut self, _: SizeConstraint, _: &mut LayoutContext) -> (Vector2F, ()) {
831 (self.size, ())
832 }
833
834 fn paint(&mut self, _: RectF, _: &mut (), _: &mut PaintContext) {
835 todo!()
836 }
837
838 fn dispatch_event(
839 &mut self,
840 _: &Event,
841 _: RectF,
842 _: &mut (),
843 _: &mut (),
844 _: &mut EventContext,
845 ) -> bool {
846 todo!()
847 }
848
849 fn debug(&self, _: RectF, _: &(), _: &(), _: &DebugContext) -> serde_json::Value {
850 self.id.into()
851 }
852
853 fn metadata(&self) -> Option<&dyn std::any::Any> {
854 Some(&self.id)
855 }
856 }
857}