1use crate::{BorrowWindow, Bounds, ElementId, LayoutId, Pixels, ViewContext};
2use derive_more::{Deref, DerefMut};
3pub(crate) use smallvec::SmallVec;
4use std::{any::Any, mem};
5
6pub trait Element<V: 'static> {
7 type ElementState: 'static;
8
9 fn id(&self) -> Option<ElementId>;
10
11 /// Called to initialize this element for the current frame. If this
12 /// element had state in a previous frame, it will be passed in for the 3rd argument.
13 fn initialize(
14 &mut self,
15 view_state: &mut V,
16 element_state: Option<Self::ElementState>,
17 cx: &mut ViewContext<V>,
18 ) -> Self::ElementState;
19 // where
20 // V: Any + Send + Sync;
21
22 fn layout(
23 &mut self,
24 view_state: &mut V,
25 element_state: &mut Self::ElementState,
26 cx: &mut ViewContext<V>,
27 ) -> LayoutId;
28 // where
29 // V: Any + Send + Sync;
30
31 fn paint(
32 &mut self,
33 bounds: Bounds<Pixels>,
34 view_state: &mut V,
35 element_state: &mut Self::ElementState,
36 cx: &mut ViewContext<V>,
37 );
38
39 // where
40 // Self::ViewState: Any + Send + Sync;
41}
42
43#[derive(Deref, DerefMut, Default, Clone, Debug, Eq, PartialEq, Hash)]
44pub struct GlobalElementId(SmallVec<[ElementId; 32]>);
45
46pub trait ParentElement<V: 'static> {
47 fn children_mut(&mut self) -> &mut SmallVec<[AnyElement<V>; 2]>;
48
49 fn child(mut self, child: impl IntoAnyElement<V>) -> Self
50 where
51 Self: Sized,
52 {
53 self.children_mut().push(child.into_any());
54 self
55 }
56
57 fn children(mut self, iter: impl IntoIterator<Item = impl IntoAnyElement<V>>) -> Self
58 where
59 Self: Sized,
60 {
61 self.children_mut()
62 .extend(iter.into_iter().map(|item| item.into_any()));
63 self
64 }
65}
66
67trait ElementObject<V> {
68 fn initialize(&mut self, view_state: &mut V, cx: &mut ViewContext<V>);
69 fn layout(&mut self, view_state: &mut V, cx: &mut ViewContext<V>) -> LayoutId;
70 fn paint(&mut self, view_state: &mut V, cx: &mut ViewContext<V>);
71}
72
73struct RenderedElement<V: 'static, E: Element<V>> {
74 element: E,
75 phase: ElementRenderPhase<E::ElementState>,
76}
77
78#[derive(Default)]
79enum ElementRenderPhase<V> {
80 #[default]
81 Start,
82 Initialized {
83 frame_state: Option<V>,
84 },
85 LayoutRequested {
86 layout_id: LayoutId,
87 frame_state: Option<V>,
88 },
89 Painted,
90}
91
92/// Internal struct that wraps an element to store Layout and ElementState after the element is rendered.
93/// It's allocated as a trait object to erase the element type and wrapped in AnyElement<E::State> for
94/// improved usability.
95impl<V, E: Element<V>> RenderedElement<V, E> {
96 fn new(element: E) -> Self {
97 RenderedElement {
98 element,
99 phase: ElementRenderPhase::Start,
100 }
101 }
102}
103
104impl<V, E> ElementObject<V> for RenderedElement<V, E>
105where
106 E: Element<V>,
107 // E::ViewState: Any + Send + Sync,
108 E::ElementState: Any + Send + Sync,
109{
110 fn initialize(&mut self, view_state: &mut V, cx: &mut ViewContext<V>) {
111 let frame_state = if let Some(id) = self.element.id() {
112 cx.with_element_state(id, |element_state, cx| {
113 let element_state = self.element.initialize(view_state, element_state, cx);
114 ((), element_state)
115 });
116 None
117 } else {
118 let frame_state = self.element.initialize(view_state, None, cx);
119 Some(frame_state)
120 };
121
122 self.phase = ElementRenderPhase::Initialized { frame_state };
123 }
124
125 fn layout(&mut self, state: &mut V, cx: &mut ViewContext<V>) -> LayoutId {
126 let layout_id;
127 let mut frame_state;
128 match mem::take(&mut self.phase) {
129 ElementRenderPhase::Initialized {
130 frame_state: initial_frame_state,
131 } => {
132 frame_state = initial_frame_state;
133 if let Some(id) = self.element.id() {
134 layout_id = cx.with_element_state(id, |element_state, cx| {
135 let mut element_state = element_state.unwrap();
136 let layout_id = self.element.layout(state, &mut element_state, cx);
137 (layout_id, element_state)
138 });
139 } else {
140 layout_id = self
141 .element
142 .layout(state, frame_state.as_mut().unwrap(), cx);
143 }
144 }
145 _ => panic!("must call initialize before layout"),
146 };
147
148 self.phase = ElementRenderPhase::LayoutRequested {
149 layout_id,
150 frame_state,
151 };
152 layout_id
153 }
154
155 fn paint(&mut self, view_state: &mut V, cx: &mut ViewContext<V>) {
156 self.phase = match mem::take(&mut self.phase) {
157 ElementRenderPhase::LayoutRequested {
158 layout_id,
159 mut frame_state,
160 } => {
161 let bounds = cx.layout_bounds(layout_id);
162 if let Some(id) = self.element.id() {
163 cx.with_element_state(id, |element_state, cx| {
164 let mut element_state = element_state.unwrap();
165 self.element
166 .paint(bounds, view_state, &mut element_state, cx);
167 ((), element_state)
168 });
169 } else {
170 self.element
171 .paint(bounds, view_state, frame_state.as_mut().unwrap(), cx);
172 }
173 ElementRenderPhase::Painted
174 }
175
176 _ => panic!("must call layout before paint"),
177 };
178 }
179}
180
181pub struct AnyElement<V>(Box<dyn ElementObject<V> + Send + Sync>);
182
183unsafe impl<V> Send for AnyElement<V> {}
184unsafe impl<V> Sync for AnyElement<V> {}
185
186impl<V> AnyElement<V> {
187 pub fn new<E>(element: E) -> Self
188 where
189 V: 'static,
190 E: 'static + Send + Sync,
191 E: Element<V>,
192 E::ElementState: Any + Send + Sync,
193 {
194 AnyElement(Box::new(RenderedElement::new(element)))
195 }
196
197 pub fn initialize(&mut self, view_state: &mut V, cx: &mut ViewContext<V>) {
198 self.0.initialize(view_state, cx);
199 }
200
201 pub fn layout(&mut self, view_state: &mut V, cx: &mut ViewContext<V>) -> LayoutId {
202 self.0.layout(view_state, cx)
203 }
204
205 pub fn paint(&mut self, view_state: &mut V, cx: &mut ViewContext<V>) {
206 self.0.paint(view_state, cx)
207 }
208}
209
210pub trait IntoAnyElement<V> {
211 fn into_any(self) -> AnyElement<V>;
212}
213
214impl<V> IntoAnyElement<V> for AnyElement<V> {
215 fn into_any(self) -> AnyElement<V> {
216 self
217 }
218}
219
220impl<V, E, F> Element<V> for Option<F>
221where
222 V: 'static,
223 E: 'static + IntoAnyElement<V> + Send + Sync,
224 F: FnOnce(&mut V, &mut ViewContext<'_, '_, V>) -> E + Send + Sync + 'static,
225{
226 type ElementState = AnyElement<V>;
227
228 fn id(&self) -> Option<ElementId> {
229 None
230 }
231
232 fn initialize(
233 &mut self,
234 view_state: &mut V,
235 _rendered_element: Option<Self::ElementState>,
236 cx: &mut ViewContext<V>,
237 ) -> Self::ElementState {
238 let render = self.take().unwrap();
239 (render)(view_state, cx).into_any()
240 }
241
242 fn layout(
243 &mut self,
244 view_state: &mut V,
245 rendered_element: &mut Self::ElementState,
246 cx: &mut ViewContext<V>,
247 ) -> LayoutId {
248 rendered_element.layout(view_state, cx)
249 }
250
251 fn paint(
252 &mut self,
253 _bounds: Bounds<Pixels>,
254 view_state: &mut V,
255 rendered_element: &mut Self::ElementState,
256 cx: &mut ViewContext<V>,
257 ) {
258 rendered_element.paint(view_state, cx)
259 }
260}
261
262impl<V, E, F> IntoAnyElement<V> for Option<F>
263where
264 V: 'static,
265 E: 'static + IntoAnyElement<V> + Send + Sync,
266 F: FnOnce(&mut V, &mut ViewContext<'_, '_, V>) -> E + Send + Sync + 'static,
267{
268 fn into_any(self) -> AnyElement<V> {
269 AnyElement::new(self)
270 }
271}
272
273impl<V, E, F> IntoAnyElement<V> for F
274where
275 V: 'static,
276 E: 'static + IntoAnyElement<V> + Send + Sync,
277 F: FnOnce(&mut V, &mut ViewContext<'_, '_, V>) -> E + Send + Sync + 'static,
278{
279 fn into_any(self) -> AnyElement<V> {
280 AnyElement::new(Some(self))
281 }
282}