1use super::{Element, Event, EventContext, LayoutContext, PaintContext, SizeConstraint};
2use crate::{
3 geometry::{
4 rect::RectF,
5 vector::{vec2f, Vector2F},
6 },
7 json::{self, json},
8 AppContext, ElementBox,
9};
10use json::ToJson;
11use parking_lot::Mutex;
12use std::{cmp, ops::Range, sync::Arc};
13
14#[derive(Clone, Default)]
15pub struct UniformListState(Arc<Mutex<StateInner>>);
16
17impl UniformListState {
18 pub fn scroll_to(&self, item_ix: usize) {
19 self.0.lock().scroll_to = Some(item_ix);
20 }
21
22 pub fn scroll_top(&self) -> f32 {
23 self.0.lock().scroll_top
24 }
25}
26
27#[derive(Default)]
28struct StateInner {
29 scroll_top: f32,
30 scroll_to: Option<usize>,
31}
32
33pub struct LayoutState {
34 scroll_max: f32,
35 item_height: f32,
36 items: Vec<ElementBox>,
37}
38
39pub struct UniformList<F>
40where
41 F: Fn(Range<usize>, &mut Vec<ElementBox>, &AppContext),
42{
43 state: UniformListState,
44 item_count: usize,
45 append_items: F,
46}
47
48impl<F> UniformList<F>
49where
50 F: Fn(Range<usize>, &mut Vec<ElementBox>, &AppContext),
51{
52 pub fn new(state: UniformListState, item_count: usize, append_items: F) -> Self {
53 Self {
54 state,
55 item_count,
56 append_items,
57 }
58 }
59
60 fn scroll(
61 &self,
62 _: Vector2F,
63 delta: Vector2F,
64 precise: bool,
65 scroll_max: f32,
66 cx: &mut EventContext,
67 ) -> bool {
68 if !precise {
69 todo!("still need to handle non-precise scroll events from a mouse wheel");
70 }
71
72 let mut state = self.state.0.lock();
73 state.scroll_top = (state.scroll_top - delta.y()).max(0.0).min(scroll_max);
74 cx.notify();
75
76 true
77 }
78
79 fn autoscroll(&mut self, scroll_max: f32, list_height: f32, item_height: f32) {
80 let mut state = self.state.0.lock();
81
82 if state.scroll_top > scroll_max {
83 state.scroll_top = scroll_max;
84 }
85
86 if let Some(item_ix) = state.scroll_to.take() {
87 let item_top = item_ix as f32 * item_height;
88 let item_bottom = item_top + item_height;
89
90 if item_top < state.scroll_top {
91 state.scroll_top = item_top;
92 } else if item_bottom > (state.scroll_top + list_height) {
93 state.scroll_top = item_bottom - list_height;
94 }
95 }
96 }
97
98 fn scroll_top(&self) -> f32 {
99 self.state.0.lock().scroll_top
100 }
101}
102
103impl<F> Element for UniformList<F>
104where
105 F: Fn(Range<usize>, &mut Vec<ElementBox>, &AppContext),
106{
107 type LayoutState = LayoutState;
108 type PaintState = ();
109
110 fn layout(
111 &mut self,
112 constraint: SizeConstraint,
113 cx: &mut LayoutContext,
114 ) -> (Vector2F, Self::LayoutState) {
115 if constraint.max.y().is_infinite() {
116 unimplemented!(
117 "UniformList does not support being rendered with an unconstrained height"
118 );
119 }
120 let mut size = constraint.max;
121 let mut item_constraint =
122 SizeConstraint::new(vec2f(size.x(), 0.0), vec2f(size.x(), f32::INFINITY));
123 let mut item_height = 0.;
124 let mut scroll_max = 0.;
125
126 let mut items = Vec::new();
127 (self.append_items)(0..1, &mut items, cx.app);
128 if let Some(first_item) = items.first_mut() {
129 let mut item_size = first_item.layout(item_constraint, cx);
130 item_size.set_x(size.x());
131 item_constraint.min = item_size;
132 item_constraint.max = item_size;
133 item_height = item_size.y();
134
135 let scroll_height = self.item_count as f32 * item_height;
136 if scroll_height < size.y() {
137 size.set_y(size.y().min(scroll_height).max(constraint.min.y()));
138 }
139
140 scroll_max = item_height * self.item_count as f32 - size.y();
141 self.autoscroll(scroll_max, size.y(), item_height);
142
143 items.clear();
144 let start = cmp::min((self.scroll_top() / item_height) as usize, self.item_count);
145 let end = cmp::min(
146 self.item_count,
147 start + (size.y() / item_height).ceil() as usize + 1,
148 );
149 (self.append_items)(start..end, &mut items, cx.app);
150 for item in &mut items {
151 item.layout(item_constraint, cx);
152 }
153 }
154
155 (
156 size,
157 LayoutState {
158 item_height,
159 scroll_max,
160 items,
161 },
162 )
163 }
164
165 fn paint(
166 &mut self,
167 bounds: RectF,
168 layout: &mut Self::LayoutState,
169 cx: &mut PaintContext,
170 ) -> Self::PaintState {
171 cx.scene.push_layer(Some(bounds));
172
173 let mut item_origin =
174 bounds.origin() - vec2f(0.0, self.state.scroll_top() % layout.item_height);
175
176 for item in &mut layout.items {
177 item.paint(item_origin, cx);
178 item_origin += vec2f(0.0, layout.item_height);
179 }
180
181 cx.scene.pop_layer();
182 }
183
184 fn dispatch_event(
185 &mut self,
186 event: &Event,
187 bounds: RectF,
188 layout: &mut Self::LayoutState,
189 _: &mut Self::PaintState,
190 cx: &mut EventContext,
191 ) -> bool {
192 let mut handled = false;
193 for item in &mut layout.items {
194 handled = item.dispatch_event(event, cx) || handled;
195 }
196
197 match event {
198 Event::ScrollWheel {
199 position,
200 delta,
201 precise,
202 } => {
203 if bounds.contains_point(*position) {
204 if self.scroll(*position, *delta, *precise, layout.scroll_max, cx) {
205 handled = true;
206 }
207 }
208 }
209 _ => {}
210 }
211
212 handled
213 }
214
215 fn debug(
216 &self,
217 bounds: RectF,
218 layout: &Self::LayoutState,
219 _: &Self::PaintState,
220 cx: &crate::DebugContext,
221 ) -> json::Value {
222 json!({
223 "type": "UniformList",
224 "bounds": bounds.to_json(),
225 "scroll_max": layout.scroll_max,
226 "item_height": layout.item_height,
227 "items": layout.items.iter().map(|item| item.debug(cx)).collect::<Vec<json::Value>>()
228
229 })
230 }
231}