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, MouseRegion,
9 PaintContext, RenderContext, 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 cx.scene
267 .push_mouse_region(MouseRegion::new::<Self>(10, 0, bounds).on_scroll({
268 let state = self.state.clone();
269 let height = bounds.height();
270 let scroll_top = scroll_top.clone();
271 move |e, cx| {
272 state.0.borrow_mut().scroll(
273 &scroll_top,
274 height,
275 e.platform_event.delta,
276 e.platform_event.precise,
277 cx,
278 )
279 }
280 }));
281
282 let state = &mut *self.state.0.borrow_mut();
283 for (mut element, origin) in state.visible_elements(bounds, scroll_top) {
284 element.paint(origin, visible_bounds, cx);
285 }
286
287 cx.scene.pop_layer();
288 }
289
290 fn dispatch_event(
291 &mut self,
292 event: &Event,
293 bounds: RectF,
294 _: RectF,
295 scroll_top: &mut ListOffset,
296 _: &mut (),
297 cx: &mut EventContext,
298 ) -> bool {
299 let mut handled = false;
300
301 let mut state = self.state.0.borrow_mut();
302 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
303 let mut cursor = state.items.cursor::<Count>();
304 let mut new_items = cursor.slice(&Count(scroll_top.item_ix), Bias::Right, &());
305 while let Some(item) = cursor.item() {
306 if item_origin.y() > bounds.max_y() {
307 break;
308 }
309
310 if let ListItem::Rendered(element) = item {
311 let prev_notify_count = cx.notify_count();
312 let mut element = element.clone();
313 handled = element.dispatch_event(event, cx) || handled;
314 item_origin.set_y(item_origin.y() + element.size().y());
315 if cx.notify_count() > prev_notify_count {
316 new_items.push(ListItem::Unrendered, &());
317 self.invalidated_elements.push(element);
318 } else {
319 new_items.push(item.clone(), &());
320 }
321 cursor.next(&());
322 } else {
323 unreachable!();
324 }
325 }
326
327 new_items.push_tree(cursor.suffix(&()), &());
328 drop(cursor);
329 state.items = new_items;
330
331 handled
332 }
333
334 fn rect_for_text_range(
335 &self,
336 range_utf16: Range<usize>,
337 bounds: RectF,
338 _: RectF,
339 scroll_top: &Self::LayoutState,
340 _: &Self::PaintState,
341 cx: &MeasurementContext,
342 ) -> Option<RectF> {
343 let state = self.state.0.borrow();
344 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
345 let mut cursor = state.items.cursor::<Count>();
346 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
347 while let Some(item) = cursor.item() {
348 if item_origin.y() > bounds.max_y() {
349 break;
350 }
351
352 if let ListItem::Rendered(element) = item {
353 if let Some(rect) = element.rect_for_text_range(range_utf16.clone(), cx) {
354 return Some(rect);
355 }
356
357 item_origin.set_y(item_origin.y() + element.size().y());
358 cursor.next(&());
359 } else {
360 unreachable!();
361 }
362 }
363
364 None
365 }
366
367 fn debug(
368 &self,
369 bounds: RectF,
370 scroll_top: &Self::LayoutState,
371 _: &(),
372 cx: &DebugContext,
373 ) -> serde_json::Value {
374 let state = self.state.0.borrow_mut();
375 let visible_elements = state
376 .visible_elements(bounds, scroll_top)
377 .map(|e| e.0.debug(cx))
378 .collect::<Vec<_>>();
379 let visible_range = scroll_top.item_ix..(scroll_top.item_ix + visible_elements.len());
380 json!({
381 "visible_range": visible_range,
382 "visible_elements": visible_elements,
383 "scroll_top": state.logical_scroll_top.map(|top| (top.item_ix, top.offset_in_item)),
384 })
385 }
386}
387
388impl ListState {
389 pub fn new<F, V>(
390 element_count: usize,
391 orientation: Orientation,
392 overdraw: f32,
393 cx: &mut ViewContext<V>,
394 mut render_item: F,
395 ) -> Self
396 where
397 V: View,
398 F: 'static + FnMut(&mut V, usize, &mut RenderContext<V>) -> ElementBox,
399 {
400 let mut items = SumTree::new();
401 items.extend((0..element_count).map(|_| ListItem::Unrendered), &());
402 let handle = cx.weak_handle();
403 Self(Rc::new(RefCell::new(StateInner {
404 last_layout_width: None,
405 render_item: Box::new(move |ix, cx| {
406 let handle = handle.upgrade(cx)?;
407 Some(cx.render(&handle, |view, cx| render_item(view, ix, cx)))
408 }),
409 rendered_range: 0..0,
410 items,
411 logical_scroll_top: None,
412 orientation,
413 overdraw,
414 scroll_handler: None,
415 })))
416 }
417
418 pub fn reset(&self, element_count: usize) {
419 let state = &mut *self.0.borrow_mut();
420 state.rendered_range = 0..0;
421 state.logical_scroll_top = None;
422 state.items = SumTree::new();
423 state
424 .items
425 .extend((0..element_count).map(|_| ListItem::Unrendered), &());
426 }
427
428 pub fn splice(&self, old_range: Range<usize>, count: usize) {
429 let state = &mut *self.0.borrow_mut();
430
431 if let Some(ListOffset {
432 item_ix,
433 offset_in_item,
434 }) = state.logical_scroll_top.as_mut()
435 {
436 if old_range.contains(item_ix) {
437 *item_ix = old_range.start;
438 *offset_in_item = 0.;
439 } else if old_range.end <= *item_ix {
440 *item_ix = *item_ix - (old_range.end - old_range.start) + count;
441 }
442 }
443
444 let new_end = old_range.start + count;
445 if old_range.start < state.rendered_range.start {
446 state.rendered_range.start =
447 new_end + state.rendered_range.start.saturating_sub(old_range.end);
448 }
449 if old_range.start < state.rendered_range.end {
450 state.rendered_range.end =
451 new_end + state.rendered_range.end.saturating_sub(old_range.end);
452 }
453
454 let mut old_heights = state.items.cursor::<Count>();
455 let mut new_heights = old_heights.slice(&Count(old_range.start), Bias::Right, &());
456 old_heights.seek_forward(&Count(old_range.end), Bias::Right, &());
457
458 new_heights.extend((0..count).map(|_| ListItem::Unrendered), &());
459 new_heights.push_tree(old_heights.suffix(&()), &());
460 drop(old_heights);
461 state.items = new_heights;
462 }
463
464 pub fn set_scroll_handler(
465 &mut self,
466 handler: impl FnMut(Range<usize>, &mut EventContext) + 'static,
467 ) {
468 self.0.borrow_mut().scroll_handler = Some(Box::new(handler))
469 }
470}
471
472impl StateInner {
473 fn render_item(
474 &mut self,
475 ix: usize,
476 existing_element: Option<&ListItem>,
477 constraint: SizeConstraint,
478 cx: &mut LayoutContext,
479 ) -> Option<ElementRc> {
480 if let Some(ListItem::Rendered(element)) = existing_element {
481 Some(element.clone())
482 } else {
483 let mut element = (self.render_item)(ix, cx)?;
484 element.layout(constraint, cx);
485 Some(element.into())
486 }
487 }
488
489 fn visible_range(&self, height: f32, scroll_top: &ListOffset) -> Range<usize> {
490 let mut cursor = self.items.cursor::<ListItemSummary>();
491 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
492 let start_y = cursor.start().height + scroll_top.offset_in_item;
493 cursor.seek_forward(&Height(start_y + height), Bias::Left, &());
494 scroll_top.item_ix..cursor.start().count + 1
495 }
496
497 fn visible_elements<'a>(
498 &'a self,
499 bounds: RectF,
500 scroll_top: &ListOffset,
501 ) -> impl Iterator<Item = (ElementRc, Vector2F)> + 'a {
502 let mut item_origin = bounds.origin() - vec2f(0., scroll_top.offset_in_item);
503 let mut cursor = self.items.cursor::<Count>();
504 cursor.seek(&Count(scroll_top.item_ix), Bias::Right, &());
505 std::iter::from_fn(move || {
506 while let Some(item) = cursor.item() {
507 if item_origin.y() > bounds.max_y() {
508 break;
509 }
510
511 if let ListItem::Rendered(element) = item {
512 let result = (element.clone(), item_origin);
513 item_origin.set_y(item_origin.y() + element.size().y());
514 cursor.next(&());
515 return Some(result);
516 }
517
518 cursor.next(&());
519 }
520
521 None
522 })
523 }
524
525 fn scroll(
526 &mut self,
527 scroll_top: &ListOffset,
528 height: f32,
529 mut delta: Vector2F,
530 precise: bool,
531 cx: &mut EventContext,
532 ) {
533 if !precise {
534 delta *= 20.;
535 }
536
537 let scroll_max = (self.items.summary().height - height).max(0.);
538 let new_scroll_top = (self.scroll_top(scroll_top) - delta.y())
539 .max(0.)
540 .min(scroll_max);
541
542 if self.orientation == Orientation::Bottom && new_scroll_top == scroll_max {
543 self.logical_scroll_top = None;
544 } else {
545 let mut cursor = self.items.cursor::<ListItemSummary>();
546 cursor.seek(&Height(new_scroll_top), Bias::Right, &());
547 let item_ix = cursor.start().count;
548 let offset_in_item = new_scroll_top - cursor.start().height;
549 self.logical_scroll_top = Some(ListOffset {
550 item_ix,
551 offset_in_item,
552 });
553 }
554
555 if self.scroll_handler.is_some() {
556 let visible_range = self.visible_range(height, scroll_top);
557 self.scroll_handler.as_mut().unwrap()(visible_range, cx);
558 }
559 }
560
561 fn scroll_top(&self, logical_scroll_top: &ListOffset) -> f32 {
562 let mut cursor = self.items.cursor::<ListItemSummary>();
563 cursor.seek(&Count(logical_scroll_top.item_ix), Bias::Right, &());
564 cursor.start().height + logical_scroll_top.offset_in_item
565 }
566}
567
568impl ListItem {
569 fn remove(&self) -> Self {
570 match self {
571 ListItem::Unrendered => ListItem::Unrendered,
572 ListItem::Rendered(element) => ListItem::Removed(element.size().y()),
573 ListItem::Removed(height) => ListItem::Removed(*height),
574 }
575 }
576}
577
578impl sum_tree::Item for ListItem {
579 type Summary = ListItemSummary;
580
581 fn summary(&self) -> Self::Summary {
582 match self {
583 ListItem::Unrendered => ListItemSummary {
584 count: 1,
585 rendered_count: 0,
586 unrendered_count: 1,
587 height: 0.,
588 },
589 ListItem::Rendered(element) => ListItemSummary {
590 count: 1,
591 rendered_count: 1,
592 unrendered_count: 0,
593 height: element.size().y(),
594 },
595 ListItem::Removed(height) => ListItemSummary {
596 count: 1,
597 rendered_count: 0,
598 unrendered_count: 1,
599 height: *height,
600 },
601 }
602 }
603}
604
605impl sum_tree::Summary for ListItemSummary {
606 type Context = ();
607
608 fn add_summary(&mut self, summary: &Self, _: &()) {
609 self.count += summary.count;
610 self.rendered_count += summary.rendered_count;
611 self.unrendered_count += summary.unrendered_count;
612 self.height += summary.height;
613 }
614}
615
616impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Count {
617 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
618 self.0 += summary.count;
619 }
620}
621
622impl<'a> sum_tree::Dimension<'a, ListItemSummary> for RenderedCount {
623 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
624 self.0 += summary.rendered_count;
625 }
626}
627
628impl<'a> sum_tree::Dimension<'a, ListItemSummary> for UnrenderedCount {
629 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
630 self.0 += summary.unrendered_count;
631 }
632}
633
634impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Height {
635 fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
636 self.0 += summary.height;
637 }
638}
639
640impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Count {
641 fn cmp(&self, other: &ListItemSummary, _: &()) -> std::cmp::Ordering {
642 self.0.partial_cmp(&other.count).unwrap()
643 }
644}
645
646impl<'a> sum_tree::SeekTarget<'a, ListItemSummary, ListItemSummary> for Height {
647 fn cmp(&self, other: &ListItemSummary, _: &()) -> std::cmp::Ordering {
648 self.0.partial_cmp(&other.height).unwrap()
649 }
650}
651
652#[cfg(test)]
653mod tests {
654 use super::*;
655 use crate::{elements::Empty, geometry::vector::vec2f, Entity};
656 use rand::prelude::*;
657 use std::env;
658
659 #[crate::test(self)]
660 fn test_layout(cx: &mut crate::MutableAppContext) {
661 let mut presenter = cx.build_presenter(0, 0., Default::default());
662 let (_, view) = cx.add_window(Default::default(), |_| TestView);
663 let constraint = SizeConstraint::new(vec2f(0., 0.), vec2f(100., 40.));
664
665 let elements = Rc::new(RefCell::new(vec![(0, 20.), (1, 30.), (2, 100.)]));
666
667 let state = view.update(cx, |_, cx| {
668 ListState::new(elements.borrow().len(), Orientation::Top, 1000.0, cx, {
669 let elements = elements.clone();
670 move |_, ix, _| {
671 let (id, height) = elements.borrow()[ix];
672 TestElement::new(id, height).boxed()
673 }
674 })
675 });
676
677 let mut list = List::new(state.clone());
678 let (size, _) = list.layout(
679 constraint,
680 &mut presenter.build_layout_context(vec2f(100., 40.), false, cx),
681 );
682 assert_eq!(size, vec2f(100., 40.));
683 assert_eq!(
684 state.0.borrow().items.summary().clone(),
685 ListItemSummary {
686 count: 3,
687 rendered_count: 3,
688 unrendered_count: 0,
689 height: 150.
690 }
691 );
692
693 state.0.borrow_mut().scroll(
694 &ListOffset {
695 item_ix: 0,
696 offset_in_item: 0.,
697 },
698 40.,
699 vec2f(0., -54.),
700 true,
701 &mut presenter.build_event_context(&mut Default::default(), cx),
702 );
703 let (_, logical_scroll_top) = list.layout(
704 constraint,
705 &mut presenter.build_layout_context(vec2f(100., 40.), false, cx),
706 );
707 assert_eq!(
708 logical_scroll_top,
709 ListOffset {
710 item_ix: 2,
711 offset_in_item: 4.
712 }
713 );
714 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 54.);
715
716 elements.borrow_mut().splice(1..2, vec![(3, 40.), (4, 50.)]);
717 elements.borrow_mut().push((5, 60.));
718 state.splice(1..2, 2);
719 state.splice(4..4, 1);
720 assert_eq!(
721 state.0.borrow().items.summary().clone(),
722 ListItemSummary {
723 count: 5,
724 rendered_count: 2,
725 unrendered_count: 3,
726 height: 120.
727 }
728 );
729
730 let (size, logical_scroll_top) = list.layout(
731 constraint,
732 &mut presenter.build_layout_context(vec2f(100., 40.), false, cx),
733 );
734 assert_eq!(size, vec2f(100., 40.));
735 assert_eq!(
736 state.0.borrow().items.summary().clone(),
737 ListItemSummary {
738 count: 5,
739 rendered_count: 5,
740 unrendered_count: 0,
741 height: 270.
742 }
743 );
744 assert_eq!(
745 logical_scroll_top,
746 ListOffset {
747 item_ix: 3,
748 offset_in_item: 4.
749 }
750 );
751 assert_eq!(state.0.borrow().scroll_top(&logical_scroll_top), 114.);
752 }
753
754 #[crate::test(self, iterations = 10, seed = 0)]
755 fn test_random(cx: &mut crate::MutableAppContext, mut rng: StdRng) {
756 let operations = env::var("OPERATIONS")
757 .map(|i| i.parse().expect("invalid `OPERATIONS` variable"))
758 .unwrap_or(10);
759
760 let (_, view) = cx.add_window(Default::default(), |_| TestView);
761 let mut presenter = cx.build_presenter(0, 0., Default::default());
762 let mut next_id = 0;
763 let elements = Rc::new(RefCell::new(
764 (0..rng.gen_range(0..=20))
765 .map(|_| {
766 let id = next_id;
767 next_id += 1;
768 (id, rng.gen_range(0..=200) as f32 / 2.0)
769 })
770 .collect::<Vec<_>>(),
771 ));
772 let orientation = *[Orientation::Top, Orientation::Bottom]
773 .choose(&mut rng)
774 .unwrap();
775 let overdraw = rng.gen_range(1..=100) as f32;
776
777 let state = view.update(cx, |_, cx| {
778 ListState::new(elements.borrow().len(), orientation, overdraw, cx, {
779 let elements = elements.clone();
780 move |_, ix, _| {
781 let (id, height) = elements.borrow()[ix];
782 TestElement::new(id, height).boxed()
783 }
784 })
785 });
786
787 let mut width = rng.gen_range(0..=2000) as f32 / 2.;
788 let mut height = rng.gen_range(0..=2000) as f32 / 2.;
789 log::info!("orientation: {:?}", orientation);
790 log::info!("overdraw: {}", overdraw);
791 log::info!("elements: {:?}", elements.borrow());
792 log::info!("size: ({:?}, {:?})", width, height);
793 log::info!("==================");
794
795 let mut last_logical_scroll_top = None;
796 for _ in 0..operations {
797 match rng.gen_range(0..=100) {
798 0..=29 if last_logical_scroll_top.is_some() => {
799 let delta = vec2f(0., rng.gen_range(-overdraw..=overdraw));
800 log::info!(
801 "Scrolling by {:?}, previous scroll top: {:?}",
802 delta,
803 last_logical_scroll_top.unwrap()
804 );
805 state.0.borrow_mut().scroll(
806 last_logical_scroll_top.as_ref().unwrap(),
807 height,
808 delta,
809 true,
810 &mut presenter.build_event_context(&mut Default::default(), cx),
811 );
812 }
813 30..=34 => {
814 width = rng.gen_range(0..=2000) as f32 / 2.;
815 log::info!("changing width: {:?}", width);
816 }
817 35..=54 => {
818 height = rng.gen_range(0..=1000) as f32 / 2.;
819 log::info!("changing height: {:?}", height);
820 }
821 _ => {
822 let mut elements = elements.borrow_mut();
823 let end_ix = rng.gen_range(0..=elements.len());
824 let start_ix = rng.gen_range(0..=end_ix);
825 let new_elements = (0..rng.gen_range(0..10))
826 .map(|_| {
827 let id = next_id;
828 next_id += 1;
829 (id, rng.gen_range(0..=200) as f32 / 2.)
830 })
831 .collect::<Vec<_>>();
832 log::info!("splice({:?}, {:?})", start_ix..end_ix, new_elements);
833 state.splice(start_ix..end_ix, new_elements.len());
834 elements.splice(start_ix..end_ix, new_elements);
835 for (ix, item) in state.0.borrow().items.cursor::<()>().enumerate() {
836 if let ListItem::Rendered(element) = item {
837 let (expected_id, _) = elements[ix];
838 element.with_metadata(|metadata: Option<&usize>| {
839 assert_eq!(*metadata.unwrap(), expected_id);
840 });
841 }
842 }
843 }
844 }
845
846 let mut list = List::new(state.clone());
847 let window_size = vec2f(width, height);
848 let (size, logical_scroll_top) = list.layout(
849 SizeConstraint::new(vec2f(0., 0.), window_size),
850 &mut presenter.build_layout_context(window_size, false, cx),
851 );
852 assert_eq!(size, window_size);
853 last_logical_scroll_top = Some(logical_scroll_top);
854
855 let state = state.0.borrow();
856 log::info!("items {:?}", state.items.items(&()));
857
858 let scroll_top = state.scroll_top(&logical_scroll_top);
859 let rendered_top = (scroll_top - overdraw).max(0.);
860 let rendered_bottom = scroll_top + height + overdraw;
861 let mut item_top = 0.;
862
863 log::info!(
864 "rendered top {:?}, rendered bottom {:?}, scroll top {:?}",
865 rendered_top,
866 rendered_bottom,
867 scroll_top,
868 );
869
870 let mut first_rendered_element_top = None;
871 let mut last_rendered_element_bottom = None;
872 assert_eq!(state.items.summary().count, elements.borrow().len());
873 for (ix, item) in state.items.cursor::<()>().enumerate() {
874 match item {
875 ListItem::Unrendered => {
876 let item_bottom = item_top;
877 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
878 item_top = item_bottom;
879 }
880 ListItem::Removed(height) => {
881 let (id, expected_height) = elements.borrow()[ix];
882 assert_eq!(
883 *height, expected_height,
884 "element {} height didn't match",
885 id
886 );
887 let item_bottom = item_top + height;
888 assert!(item_bottom <= rendered_top || item_top >= rendered_bottom);
889 item_top = item_bottom;
890 }
891 ListItem::Rendered(element) => {
892 let (expected_id, expected_height) = elements.borrow()[ix];
893 element.with_metadata(|metadata: Option<&usize>| {
894 assert_eq!(*metadata.unwrap(), expected_id);
895 });
896 assert_eq!(element.size().y(), expected_height);
897 let item_bottom = item_top + element.size().y();
898 first_rendered_element_top.get_or_insert(item_top);
899 last_rendered_element_bottom = Some(item_bottom);
900 assert!(item_bottom > rendered_top || item_top < rendered_bottom);
901 item_top = item_bottom;
902 }
903 }
904 }
905
906 match orientation {
907 Orientation::Top => {
908 if let Some(first_rendered_element_top) = first_rendered_element_top {
909 assert!(first_rendered_element_top <= scroll_top);
910 }
911 }
912 Orientation::Bottom => {
913 if let Some(last_rendered_element_bottom) = last_rendered_element_bottom {
914 assert!(last_rendered_element_bottom >= scroll_top + height);
915 }
916 }
917 }
918 }
919 }
920
921 struct TestView;
922
923 impl Entity for TestView {
924 type Event = ();
925 }
926
927 impl View for TestView {
928 fn ui_name() -> &'static str {
929 "TestView"
930 }
931
932 fn render(&mut self, _: &mut RenderContext<'_, Self>) -> ElementBox {
933 Empty::new().boxed()
934 }
935 }
936
937 struct TestElement {
938 id: usize,
939 size: Vector2F,
940 }
941
942 impl TestElement {
943 fn new(id: usize, height: f32) -> Self {
944 Self {
945 id,
946 size: vec2f(100., height),
947 }
948 }
949 }
950
951 impl Element for TestElement {
952 type LayoutState = ();
953 type PaintState = ();
954
955 fn layout(&mut self, _: SizeConstraint, _: &mut LayoutContext) -> (Vector2F, ()) {
956 (self.size, ())
957 }
958
959 fn paint(&mut self, _: RectF, _: RectF, _: &mut (), _: &mut PaintContext) {
960 todo!()
961 }
962
963 fn dispatch_event(
964 &mut self,
965 _: &Event,
966 _: RectF,
967 _: RectF,
968 _: &mut (),
969 _: &mut (),
970 _: &mut EventContext,
971 ) -> bool {
972 todo!()
973 }
974
975 fn rect_for_text_range(
976 &self,
977 _: Range<usize>,
978 _: RectF,
979 _: RectF,
980 _: &Self::LayoutState,
981 _: &Self::PaintState,
982 _: &MeasurementContext,
983 ) -> Option<RectF> {
984 todo!()
985 }
986
987 fn debug(&self, _: RectF, _: &(), _: &(), _: &DebugContext) -> serde_json::Value {
988 self.id.into()
989 }
990
991 fn metadata(&self) -> Option<&dyn std::any::Any> {
992 Some(&self.id)
993 }
994 }
995}