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.rendered_range = 0..0;
325 state.logical_scroll_top = None;
326 state.items = SumTree::new();
327 state
328 .items
329 .extend((0..element_count).map(|_| ListItem::Unrendered), &());
330 }
331
332 pub fn splice(&self, old_range: Range<usize>, count: usize) {
333 let state = &mut *self.0.borrow_mut();
334
335 if let Some(ListOffset {
336 item_ix,
337 offset_in_item,
338 }) = state.logical_scroll_top.as_mut()
339 {
340 if old_range.contains(item_ix) {
341 *item_ix = old_range.start;
342 *offset_in_item = 0.;
343 } else if old_range.end <= *item_ix {
344 *item_ix = *item_ix - (old_range.end - old_range.start) + count;
345 }
346 }
347
348 let new_end = old_range.start + count;
349 if old_range.start < state.rendered_range.start {
350 state.rendered_range.start =
351 new_end + state.rendered_range.start.saturating_sub(old_range.end);
352 }
353 if old_range.start < state.rendered_range.end {
354 state.rendered_range.end =
355 new_end + state.rendered_range.end.saturating_sub(old_range.end);
356 }
357
358 let mut old_heights = state.items.cursor::<Count, ()>();
359 let mut new_heights = old_heights.slice(&Count(old_range.start), Bias::Right, &());
360 old_heights.seek_forward(&Count(old_range.end), Bias::Right, &());
361
362 new_heights.extend((0..count).map(|_| ListItem::Unrendered), &());
363 new_heights.push_tree(old_heights.suffix(&()), &());
364 drop(old_heights);
365 state.items = new_heights;
366 }
367
368 pub fn set_scroll_handler(
369 &mut self,
370 handler: impl FnMut(Range<usize>, &mut EventContext) + 'static,
371 ) {
372 self.0.borrow_mut().scroll_handler = Some(Box::new(handler))
373 }
374}
375
376impl StateInner {
377 fn render_item(
378 &mut self,
379 ix: usize,
380 existing_item: &ListItem,
381 constraint: SizeConstraint,
382 cx: &mut LayoutContext,
383 ) -> ElementRc {
384 if let ListItem::Rendered(element) = existing_item {
385 element.clone()
386 } else {
387 let mut element = (self.render_item)(ix, cx);
388 element.layout(constraint, cx);
389 element.into()
390 }
391 }
392
393 fn visible_range(&self, height: f32, scroll_top: &ListOffset) -> Range<usize> {
394 let mut cursor = self.items.cursor::<Count, Height>();
395 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
396 let start_y = cursor.sum_start().0 + scroll_top.offset_in_item;
397 let mut cursor = cursor.swap_dimensions();
398 cursor.seek_forward(&Height(start_y + height), Bias::Left, &());
399 scroll_top.item_ix..cursor.sum_start().0 + 1
400 }
401
402 fn visible_elements<'a>(
403 &'a self,
404 bounds: RectF,
405 scroll_top: &ListOffset,
406 ) -> impl Iterator<Item = (ElementRc, Vector2F)> + 'a {
407 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
408 let mut cursor = self.items.cursor::<Count, ()>();
409 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
410 std::iter::from_fn(move || {
411 while let Some(item) = cursor.item() {
412 if item_origin.y() > bounds.max_y() {
413 break;
414 }
415
416 if let ListItem::Rendered(element) = item {
417 let result = (element.clone(), item_origin);
418 item_origin.set_y(item_origin.y() + element.size().y());
419 cursor.next(&());
420 return Some(result);
421 }
422
423 cursor.next(&());
424 }
425
426 None
427 })
428 }
429
430 fn scroll(
431 &mut self,
432 scroll_top: &ListOffset,
433 height: f32,
434 mut delta: Vector2F,
435 precise: bool,
436 cx: &mut EventContext,
437 ) -> bool {
438 if !precise {
439 delta *= 20.;
440 }
441
442 let scroll_max = (self.items.summary().height - height).max(0.);
443 let new_scroll_top = (self.scroll_top(scroll_top) - delta.y())
444 .max(0.)
445 .min(scroll_max);
446
447 if self.orientation == Orientation::Bottom && new_scroll_top == scroll_max {
448 self.logical_scroll_top = None;
449 } else {
450 let mut cursor = self.items.cursor::<Height, Count>();
451 cursor.seek(&Height(new_scroll_top), Bias::Right, &());
452 let item_ix = cursor.sum_start().0;
453 let offset_in_item = new_scroll_top - cursor.seek_start().0;
454 self.logical_scroll_top = Some(ListOffset {
455 item_ix,
456 offset_in_item,
457 });
458 }
459
460 if self.scroll_handler.is_some() {
461 let visible_range = self.visible_range(height, scroll_top);
462 self.scroll_handler.as_mut().unwrap()(visible_range, cx);
463 }
464 cx.notify();
465
466 true
467 }
468
469 fn scroll_top(&self, logical_scroll_top: &ListOffset) -> f32 {
470 let mut cursor = self.items.cursor::<Count, Height>();
471 cursor.seek(&Count(logical_scroll_top.item_ix), Bias::Right, &());
472 cursor.sum_start().0 + logical_scroll_top.offset_in_item
473 }
474}
475
476impl ListItem {
477 fn remove(&self) -> Self {
478 match self {
479 ListItem::Unrendered => ListItem::Unrendered,
480 ListItem::Rendered(element) => ListItem::Removed(element.size().y()),
481 ListItem::Removed(height) => ListItem::Removed(*height),
482 }
483 }
484}
485
486impl sum_tree::Item for ListItem {
487 type Summary = ListItemSummary;
488
489 fn summary(&self) -> Self::Summary {
490 match self {
491 ListItem::Unrendered => ListItemSummary {
492 count: 1,
493 rendered_count: 0,
494 unrendered_count: 1,
495 height: 0.,
496 },
497 ListItem::Rendered(element) => ListItemSummary {
498 count: 1,
499 rendered_count: 1,
500 unrendered_count: 0,
501 height: element.size().y(),
502 },
503 ListItem::Removed(height) => ListItemSummary {
504 count: 1,
505 rendered_count: 0,
506 unrendered_count: 1,
507 height: *height,
508 },
509 }
510 }
511}
512
513impl sum_tree::Summary for ListItemSummary {
514 type Context = ();
515
516 fn add_summary(&mut self, summary: &Self, _: &()) {
517 self.count += summary.count;
518 self.rendered_count += summary.rendered_count;
519 self.unrendered_count += summary.unrendered_count;
520 self.height += summary.height;
521 }
522}
523
524impl<'a> sum_tree::Dimension<'a, ListItemSummary> for ListItemSummary {
525 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
526 sum_tree::Summary::add_summary(self, summary, &());
527 }
528}
529
530impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Count {
531 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
532 self.0 += summary.count;
533 }
534}
535
536impl<'a> sum_tree::Dimension<'a, ListItemSummary> for RenderedCount {
537 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
538 self.0 += summary.rendered_count;
539 }
540}
541
542impl<'a> sum_tree::Dimension<'a, ListItemSummary> for UnrenderedCount {
543 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
544 self.0 += summary.unrendered_count;
545 }
546}
547
548impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Height {
549 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
550 self.0 += summary.height;
551 }
552}
553
554impl<'a> sum_tree::SeekDimension<'a, ListItemSummary> for Height {
555 fn cmp(&self, other: &Self, _: &()) -> std::cmp::Ordering {
556 self.0.partial_cmp(&other.0).unwrap()
557 }
558}
559
560#[cfg(test)]
561mod tests {
562 use super::*;
563 use crate::geometry::vector::vec2f;
564 use rand::prelude::*;
565 use std::env;
566
567 #[crate::test(self)]
568 fn test_layout(cx: &mut crate::MutableAppContext) {
569 let mut presenter = cx.build_presenter(0, 0.);
570 let constraint = SizeConstraint::new(vec2f(0., 0.), vec2f(100., 40.));
571
572 let elements = Rc::new(RefCell::new(vec![(0, 20.), (1, 30.), (2, 100.)]));
573 let state = ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, {
574 let elements = elements.clone();
575 move |ix, _| {
576 let (id, height) = elements.borrow()[ix];
577 TestElement::new(id, height).boxed()
578 }
579 });
580
581 let mut list = List::new(state.clone());
582 let (size, _) = list.layout(constraint, &mut presenter.build_layout_context(false, cx));
583 assert_eq!(size, vec2f(100., 40.));
584 assert_eq!(
585 state.0.borrow().items.summary(),
586 ListItemSummary {
587 count: 3,
588 rendered_count: 3,
589 unrendered_count: 0,
590 height: 150.
591 }
592 );
593
594 state.0.borrow_mut().scroll(
595 &ListOffset {
596 item_ix: 0,
597 offset_in_item: 0.,
598 },
599 40.,
600 vec2f(0., 54.),
601 true,
602 &mut presenter.build_event_context(cx),
603 );
604 let (_, logical_scroll_top) =
605 list.layout(constraint, &mut presenter.build_layout_context(false, cx));
606 assert_eq!(
607 logical_scroll_top,
608 ListOffset {
609 item_ix: 2,
610 offset_in_item: 4.
611 }
612 );
613 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 54.);
614
615 elements.borrow_mut().splice(1..2, vec![(3, 40.), (4, 50.)]);
616 elements.borrow_mut().push((5, 60.));
617 state.splice(1..2, 2);
618 state.splice(4..4, 1);
619 assert_eq!(
620 state.0.borrow().items.summary(),
621 ListItemSummary {
622 count: 5,
623 rendered_count: 2,
624 unrendered_count: 3,
625 height: 120.
626 }
627 );
628
629 let (size, logical_scroll_top) =
630 list.layout(constraint, &mut presenter.build_layout_context(false, cx));
631 assert_eq!(size, vec2f(100., 40.));
632 assert_eq!(
633 state.0.borrow().items.summary(),
634 ListItemSummary {
635 count: 5,
636 rendered_count: 5,
637 unrendered_count: 0,
638 height: 270.
639 }
640 );
641 assert_eq!(
642 logical_scroll_top,
643 ListOffset {
644 item_ix: 3,
645 offset_in_item: 4.
646 }
647 );
648 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 114.);
649 }
650
651 #[crate::test(self, iterations = 10000, seed = 0)]
652 fn test_random(cx: &mut crate::MutableAppContext, mut rng: StdRng) {
653 let operations = env::var("OPERATIONS")
654 .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
655 .unwrap_or(10);
656
657 let mut presenter = cx.build_presenter(0, 0.);
658 let mut next_id = 0;
659 let elements = Rc::new(RefCell::new(
660 (0..rng.gen_range(0..=20))
661 .map(|_| {
662 let id = next_id;
663 next_id += 1;
664 (id, rng.gen_range(0..=200) as f32 / 2.0)
665 })
666 .collect::<Vec<_>>(),
667 ));
668 let orientation = *[Orientation::Top, Orientation::Bottom]
669 .choose(&mut rng)
670 .unwrap();
671 let overdraw = rng.gen_range(1..=100) as f32;
672 let state = ListState::new(elements.borrow().len(), orientation, overdraw, {
673 let elements = elements.clone();
674 move |ix, _| {
675 let (id, height) = elements.borrow()[ix];
676 TestElement::new(id, height).boxed()
677 }
678 });
679
680 let mut width = rng.gen_range(0..=2000) as f32 / 2.;
681 let mut height = rng.gen_range(0..=2000) as f32 / 2.;
682 log::info!("orientation: {:?}", orientation);
683 log::info!("overdraw: {}", overdraw);
684 log::info!("elements: {:?}", elements.borrow());
685 log::info!("size: ({:?}, {:?})", width, height);
686 log::info!("==================");
687
688 let mut last_logical_scroll_top = None;
689 for _ in 0..operations {
690 match rng.gen_range(0..=100) {
691 0..=29 if last_logical_scroll_top.is_some() => {
692 let delta = vec2f(0., rng.gen_range(-overdraw..=overdraw));
693 log::info!(
694 "Scrolling by {:?}, previous scroll top: {:?}",
695 delta,
696 last_logical_scroll_top.unwrap()
697 );
698 state.0.borrow_mut().scroll(
699 last_logical_scroll_top.as_ref().unwrap(),
700 height,
701 delta,
702 true,
703 &mut presenter.build_event_context(cx),
704 );
705 }
706 30..=34 => {
707 width = rng.gen_range(0..=2000) as f32 / 2.;
708 log::info!("changing width: {:?}", width);
709 }
710 35..=54 => {
711 height = rng.gen_range(0..=1000) as f32 / 2.;
712 log::info!("changing height: {:?}", height);
713 }
714 _ => {
715 let mut elements = elements.borrow_mut();
716 let end_ix = rng.gen_range(0..=elements.len());
717 let start_ix = rng.gen_range(0..=end_ix);
718 let new_elements = (0..rng.gen_range(0..10))
719 .map(|_| {
720 let id = next_id;
721 next_id += 1;
722 (id, rng.gen_range(0..=200) as f32 / 2.)
723 })
724 .collect::<Vec<_>>();
725 log::info!("splice({:?}, {:?})", start_ix..end_ix, new_elements);
726 state.splice(start_ix..end_ix, new_elements.len());
727 elements.splice(start_ix..end_ix, new_elements);
728 for (ix, item) in state.0.borrow().items.cursor::<(), ()>().enumerate() {
729 if let ListItem::Rendered(element) = item {
730 let (expected_id, _) = elements[ix];
731 element.with_metadata(|metadata: Option<&usize>| {
732 assert_eq!(*metadata.unwrap(), expected_id);
733 });
734 }
735 }
736 }
737 }
738
739 let mut list = List::new(state.clone());
740 let (size, logical_scroll_top) = list.layout(
741 SizeConstraint::new(vec2f(0., 0.), vec2f(width, height)),
742 &mut presenter.build_layout_context(false, cx),
743 );
744 assert_eq!(size, vec2f(width, height));
745 last_logical_scroll_top = Some(logical_scroll_top);
746
747 let state = state.0.borrow();
748 log::info!("items {:?}", state.items.items(&()));
749
750 let scroll_top = state.scroll_top(&logical_scroll_top);
751 let rendered_top = (scroll_top - overdraw).max(0.);
752 let rendered_bottom = scroll_top + height + overdraw;
753 let mut item_top = 0.;
754
755 log::info!(
756 "rendered top {:?}, rendered bottom {:?}, scroll top {:?}",
757 rendered_top,
758 rendered_bottom,
759 scroll_top,
760 );
761
762 let mut first_rendered_element_top = None;
763 let mut last_rendered_element_bottom = None;
764 assert_eq!(state.items.summary().count, elements.borrow().len());
765 for (ix, item) in state.items.cursor::<(), ()>().enumerate() {
766 match item {
767 ListItem::Unrendered => {
768 let item_bottom = item_top;
769 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
770 item_top = item_bottom;
771 }
772 ListItem::Removed(height) => {
773 let (id, expected_height) = elements.borrow()[ix];
774 assert_eq!(
775 *height, expected_height,
776 "element {} height didn't match",
777 id
778 );
779 let item_bottom = item_top + height;
780 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
781 item_top = item_bottom;
782 }
783 ListItem::Rendered(element) => {
784 let (expected_id, expected_height) = elements.borrow()[ix];
785 element.with_metadata(|metadata: Option<&usize>| {
786 assert_eq!(*metadata.unwrap(), expected_id);
787 });
788 assert_eq!(element.size().y(), expected_height);
789 let item_bottom = item_top + element.size().y();
790 first_rendered_element_top.get_or_insert(item_top);
791 last_rendered_element_bottom = Some(item_bottom);
792 assert!(item_bottom > rendered_top || item_top < rendered_bottom);
793 item_top = item_bottom;
794 }
795 }
796 }
797
798 match orientation {
799 Orientation::Top => {
800 if let Some(first_rendered_element_top) = first_rendered_element_top {
801 assert!(first_rendered_element_top <= scroll_top);
802 }
803 }
804 Orientation::Bottom => {
805 if let Some(last_rendered_element_bottom) = last_rendered_element_bottom {
806 assert!(last_rendered_element_bottom >= scroll_top + height);
807 }
808 }
809 }
810 }
811 }
812
813 struct TestElement {
814 id: usize,
815 size: Vector2F,
816 }
817
818 impl TestElement {
819 fn new(id: usize, height: f32) -> Self {
820 Self {
821 id,
822 size: vec2f(100., height),
823 }
824 }
825 }
826
827 impl Element for TestElement {
828 type LayoutState = ();
829 type PaintState = ();
830
831 fn layout(&mut self, _: SizeConstraint, _: &mut LayoutContext) -> (Vector2F, ()) {
832 (self.size, ())
833 }
834
835 fn paint(&mut self, _: RectF, _: &mut (), _: &mut PaintContext) {
836 todo!()
837 }
838
839 fn dispatch_event(
840 &mut self,
841 _: &Event,
842 _: RectF,
843 _: &mut (),
844 _: &mut (),
845 _: &mut EventContext,
846 ) -> bool {
847 todo!()
848 }
849
850 fn debug(&self, _: RectF, _: &(), _: &(), _: &DebugContext) -> serde_json::Value {
851 self.id.into()
852 }
853
854 fn metadata(&self) -> Option<&dyn std::any::Any> {
855 Some(&self.id)
856 }
857 }
858}