window.rs

  1use crate::{
  2    image_cache::RenderImageParams, px, size, AnyView, AppContext, AsyncWindowContext,
  3    AvailableSpace, BorrowAppContext, Bounds, Context, Corners, DevicePixels, DisplayId, Effect,
  4    Element, EntityId, FontId, GlyphId, Handle, Hsla, ImageData, IsZero, LayoutId, MainThread,
  5    MainThreadOnly, MonochromeSprite, Pixels, PlatformAtlas, PlatformWindow, Point,
  6    PolychromeSprite, Reference, RenderGlyphParams, RenderSvgParams, ScaledPixels, Scene,
  7    SharedString, Size, StackingOrder, Style, TaffyLayoutEngine, Task, Underline, UnderlineStyle,
  8    WeakHandle, WindowOptions, SUBPIXEL_VARIANTS,
  9};
 10use anyhow::Result;
 11use smallvec::SmallVec;
 12use std::{any::TypeId, borrow::Cow, future::Future, marker::PhantomData, mem, sync::Arc};
 13use util::ResultExt;
 14
 15pub struct AnyWindow {}
 16
 17pub struct Window {
 18    handle: AnyWindowHandle,
 19    platform_window: MainThreadOnly<Box<dyn PlatformWindow>>,
 20    pub(crate) display_id: DisplayId, // todo!("make private again?")
 21    sprite_atlas: Arc<dyn PlatformAtlas>,
 22    rem_size: Pixels,
 23    content_size: Size<Pixels>,
 24    layout_engine: TaffyLayoutEngine,
 25    pub(crate) root_view: Option<AnyView<()>>,
 26    mouse_position: Point<Pixels>,
 27    current_stacking_order: StackingOrder,
 28    content_mask_stack: Vec<ContentMask>,
 29    pub(crate) scene: Scene,
 30    pub(crate) dirty: bool,
 31}
 32
 33impl Window {
 34    pub fn new(
 35        handle: AnyWindowHandle,
 36        options: WindowOptions,
 37        cx: &mut MainThread<AppContext>,
 38    ) -> Self {
 39        let platform_window = cx.platform().open_window(handle, options);
 40        let display_id = platform_window.display().id();
 41        let sprite_atlas = platform_window.sprite_atlas();
 42        let mouse_position = platform_window.mouse_position();
 43        let content_size = platform_window.content_size();
 44        let scale_factor = platform_window.scale_factor();
 45        platform_window.on_resize(Box::new({
 46            let handle = handle;
 47            let cx = cx.to_async();
 48            move |content_size, scale_factor| {
 49                cx.update_window(handle, |cx| {
 50                    cx.window.scene = Scene::new(scale_factor);
 51                    cx.window.content_size = content_size;
 52                    cx.window.display_id = cx
 53                        .window
 54                        .platform_window
 55                        .borrow_on_main_thread()
 56                        .display()
 57                        .id();
 58                    cx.window.dirty = true;
 59                })
 60                .log_err();
 61            }
 62        }));
 63
 64        let platform_window = MainThreadOnly::new(Arc::new(platform_window), cx.executor.clone());
 65
 66        Window {
 67            handle,
 68            platform_window,
 69            display_id,
 70            sprite_atlas,
 71            rem_size: px(16.),
 72            content_size,
 73            layout_engine: TaffyLayoutEngine::new(),
 74            root_view: None,
 75            mouse_position,
 76            current_stacking_order: SmallVec::new(),
 77            content_mask_stack: Vec::new(),
 78            scene: Scene::new(scale_factor),
 79            dirty: true,
 80        }
 81    }
 82}
 83
 84#[derive(Clone, Debug)]
 85pub struct ContentMask {
 86    pub bounds: Bounds<Pixels>,
 87}
 88
 89impl ContentMask {
 90    pub fn scale(&self, factor: f32) -> ScaledContentMask {
 91        ScaledContentMask {
 92            bounds: self.bounds.scale(factor),
 93        }
 94    }
 95
 96    pub fn intersect(&self, other: &Self) -> Self {
 97        let bounds = self.bounds.intersect(&other.bounds);
 98        ContentMask { bounds }
 99    }
100}
101
102#[derive(Default, Clone, Debug, PartialEq, Eq)]
103#[repr(C)]
104pub struct ScaledContentMask {
105    bounds: Bounds<ScaledPixels>,
106}
107
108pub struct WindowContext<'a, 'w> {
109    app: Reference<'a, AppContext>,
110    window: Reference<'w, Window>,
111}
112
113impl<'a, 'w> WindowContext<'a, 'w> {
114    pub(crate) fn mutable(app: &'a mut AppContext, window: &'w mut Window) -> Self {
115        Self {
116            app: Reference::Mutable(app),
117            window: Reference::Mutable(window),
118        }
119    }
120
121    pub fn notify(&mut self) {
122        self.window.dirty = true;
123    }
124
125    pub fn run_on_main<R>(
126        &mut self,
127        f: impl FnOnce(&mut MainThread<WindowContext<'_, '_>>) -> R + Send + 'static,
128    ) -> Task<Result<R>>
129    where
130        R: Send + 'static,
131    {
132        if self.executor.is_main_thread() {
133            Task::ready(Ok(f(unsafe {
134                mem::transmute::<&mut Self, &mut MainThread<Self>>(self)
135            })))
136        } else {
137            let id = self.window.handle.id;
138            self.app.run_on_main(move |cx| cx.update_window(id, f))
139        }
140    }
141
142    pub fn to_async(&self) -> AsyncWindowContext {
143        AsyncWindowContext::new(self.app.to_async(), self.window.handle)
144    }
145
146    pub fn on_next_frame(&mut self, f: impl FnOnce(&mut WindowContext) + Send + 'static) {
147        let f = Box::new(f);
148        let display_id = self.window.display_id;
149        let async_cx = self.to_async();
150        let app_cx = self.app_mut();
151        match app_cx.next_frame_callbacks.entry(display_id) {
152            collections::hash_map::Entry::Occupied(mut entry) => {
153                if entry.get().is_empty() {
154                    app_cx.display_linker.start(display_id);
155                }
156                entry.get_mut().push(f);
157            }
158            collections::hash_map::Entry::Vacant(entry) => {
159                app_cx.display_linker.set_output_callback(
160                    display_id,
161                    Box::new(move |_current_time, _output_time| {
162                        let _ = async_cx.update(|cx| {
163                            let callbacks = cx
164                                .next_frame_callbacks
165                                .get_mut(&display_id)
166                                .unwrap()
167                                .drain(..)
168                                .collect::<Vec<_>>();
169                            for callback in callbacks {
170                                callback(cx);
171                            }
172
173                            if cx.next_frame_callbacks.get(&display_id).unwrap().is_empty() {
174                                cx.display_linker.stop(display_id);
175                            }
176                        });
177                    }),
178                );
179                app_cx.display_linker.start(display_id);
180                entry.insert(vec![f]);
181            }
182        }
183    }
184
185    pub fn spawn<Fut, R>(
186        &mut self,
187        f: impl FnOnce(AnyWindowHandle, AsyncWindowContext) -> Fut + Send + 'static,
188    ) -> Task<R>
189    where
190        R: Send + 'static,
191        Fut: Future<Output = R> + Send + 'static,
192    {
193        let window = self.window.handle;
194        self.app.spawn(move |app| {
195            let cx = AsyncWindowContext::new(app, window);
196            let future = f(window, cx);
197            async move { future.await }
198        })
199    }
200
201    pub fn request_layout(
202        &mut self,
203        style: Style,
204        children: impl IntoIterator<Item = LayoutId>,
205    ) -> Result<LayoutId> {
206        self.app.layout_id_buffer.clear();
207        self.app.layout_id_buffer.extend(children.into_iter());
208        let rem_size = self.rem_size();
209
210        self.window
211            .layout_engine
212            .request_layout(style, rem_size, &self.app.layout_id_buffer)
213    }
214
215    pub fn request_measured_layout<
216        F: Fn(Size<Option<Pixels>>, Size<AvailableSpace>) -> Size<Pixels> + Send + Sync + 'static,
217    >(
218        &mut self,
219        style: Style,
220        rem_size: Pixels,
221        measure: F,
222    ) -> Result<LayoutId> {
223        self.window
224            .layout_engine
225            .request_measured_layout(style, rem_size, measure)
226    }
227
228    pub fn layout_bounds(&mut self, layout_id: LayoutId) -> Result<Bounds<Pixels>> {
229        Ok(self
230            .window
231            .layout_engine
232            .layout_bounds(layout_id)
233            .map(Into::into)?)
234    }
235
236    pub fn scale_factor(&self) -> f32 {
237        self.window.scene.scale_factor
238    }
239
240    pub fn rem_size(&self) -> Pixels {
241        self.window.rem_size
242    }
243
244    pub fn mouse_position(&self) -> Point<Pixels> {
245        self.window.mouse_position
246    }
247
248    pub fn scene(&mut self) -> &mut Scene {
249        &mut self.window.scene
250    }
251
252    pub fn stack<R>(&mut self, order: u32, f: impl FnOnce(&mut Self) -> R) -> R {
253        self.window.current_stacking_order.push(order);
254        let result = f(self);
255        self.window.current_stacking_order.pop();
256        result
257    }
258
259    pub fn current_stacking_order(&self) -> StackingOrder {
260        self.window.current_stacking_order.clone()
261    }
262
263    pub fn paint_underline(
264        &mut self,
265        origin: Point<Pixels>,
266        width: Pixels,
267        style: &UnderlineStyle,
268    ) -> Result<()> {
269        let scale_factor = self.scale_factor();
270        let height = if style.wavy {
271            style.thickness * 3.
272        } else {
273            style.thickness
274        };
275        let bounds = Bounds {
276            origin,
277            size: size(width, height),
278        };
279        let content_mask = self.content_mask();
280        let layer_id = self.current_stacking_order();
281        self.window.scene.insert(
282            layer_id,
283            Underline {
284                order: 0,
285                bounds: bounds.scale(scale_factor),
286                content_mask: content_mask.scale(scale_factor),
287                thickness: style.thickness.scale(scale_factor),
288                color: style.color.unwrap_or_default(),
289                wavy: style.wavy,
290            },
291        );
292        Ok(())
293    }
294
295    pub fn paint_glyph(
296        &mut self,
297        origin: Point<Pixels>,
298        font_id: FontId,
299        glyph_id: GlyphId,
300        font_size: Pixels,
301        color: Hsla,
302    ) -> Result<()> {
303        let scale_factor = self.scale_factor();
304        let glyph_origin = origin.scale(scale_factor);
305        let subpixel_variant = Point {
306            x: (glyph_origin.x.0.fract() * SUBPIXEL_VARIANTS as f32).floor() as u8,
307            y: (glyph_origin.y.0.fract() * SUBPIXEL_VARIANTS as f32).floor() as u8,
308        };
309        let params = RenderGlyphParams {
310            font_id,
311            glyph_id,
312            font_size,
313            subpixel_variant,
314            scale_factor,
315            is_emoji: false,
316        };
317
318        let raster_bounds = self.text_system().raster_bounds(&params)?;
319        if !raster_bounds.is_zero() {
320            let layer_id = self.current_stacking_order();
321            let tile =
322                self.window
323                    .sprite_atlas
324                    .get_or_insert_with(&params.clone().into(), &mut || {
325                        let (size, bytes) = self.text_system().rasterize_glyph(&params)?;
326                        Ok((size, Cow::Owned(bytes)))
327                    })?;
328            let bounds = Bounds {
329                origin: glyph_origin.map(|px| px.floor()) + raster_bounds.origin.map(Into::into),
330                size: tile.bounds.size.map(Into::into),
331            };
332            let content_mask = self.content_mask().scale(scale_factor);
333
334            self.window.scene.insert(
335                layer_id,
336                MonochromeSprite {
337                    order: 0,
338                    bounds,
339                    content_mask,
340                    color,
341                    tile,
342                },
343            );
344        }
345        Ok(())
346    }
347
348    pub fn paint_emoji(
349        &mut self,
350        origin: Point<Pixels>,
351        font_id: FontId,
352        glyph_id: GlyphId,
353        font_size: Pixels,
354    ) -> Result<()> {
355        let scale_factor = self.scale_factor();
356        let glyph_origin = origin.scale(scale_factor);
357        let params = RenderGlyphParams {
358            font_id,
359            glyph_id,
360            font_size,
361            // We don't render emojis with subpixel variants.
362            subpixel_variant: Default::default(),
363            scale_factor,
364            is_emoji: true,
365        };
366
367        let raster_bounds = self.text_system().raster_bounds(&params)?;
368        if !raster_bounds.is_zero() {
369            let layer_id = self.current_stacking_order();
370            let tile =
371                self.window
372                    .sprite_atlas
373                    .get_or_insert_with(&params.clone().into(), &mut || {
374                        let (size, bytes) = self.text_system().rasterize_glyph(&params)?;
375                        Ok((size, Cow::Owned(bytes)))
376                    })?;
377            let bounds = Bounds {
378                origin: glyph_origin.map(|px| px.floor()) + raster_bounds.origin.map(Into::into),
379                size: tile.bounds.size.map(Into::into),
380            };
381            let content_mask = self.content_mask().scale(scale_factor);
382
383            self.window.scene.insert(
384                layer_id,
385                PolychromeSprite {
386                    order: 0,
387                    bounds,
388                    corner_radii: Default::default(),
389                    content_mask,
390                    tile,
391                    grayscale: false,
392                },
393            );
394        }
395        Ok(())
396    }
397
398    pub fn paint_svg(
399        &mut self,
400        bounds: Bounds<Pixels>,
401        path: SharedString,
402        color: Hsla,
403    ) -> Result<()> {
404        let scale_factor = self.scale_factor();
405        let bounds = bounds.scale(scale_factor);
406        // Render the SVG at twice the size to get a higher quality result.
407        let params = RenderSvgParams {
408            path,
409            size: bounds
410                .size
411                .map(|pixels| DevicePixels::from((pixels.0 * 2.).ceil() as i32)),
412        };
413
414        let layer_id = self.current_stacking_order();
415        let tile =
416            self.window
417                .sprite_atlas
418                .get_or_insert_with(&params.clone().into(), &mut || {
419                    let bytes = self.svg_renderer.render(&params)?;
420                    Ok((params.size, Cow::Owned(bytes)))
421                })?;
422        let content_mask = self.content_mask().scale(scale_factor);
423
424        self.window.scene.insert(
425            layer_id,
426            MonochromeSprite {
427                order: 0,
428                bounds,
429                content_mask,
430                color,
431                tile,
432            },
433        );
434
435        Ok(())
436    }
437
438    pub fn paint_image(
439        &mut self,
440        bounds: Bounds<Pixels>,
441        corner_radii: Corners<Pixels>,
442        data: Arc<ImageData>,
443        grayscale: bool,
444    ) -> Result<()> {
445        let scale_factor = self.scale_factor();
446        let bounds = bounds.scale(scale_factor);
447        let params = RenderImageParams { image_id: data.id };
448
449        let order = self.current_stacking_order();
450        let tile = self
451            .window
452            .sprite_atlas
453            .get_or_insert_with(&params.clone().into(), &mut || {
454                Ok((data.size(), Cow::Borrowed(data.as_bytes())))
455            })?;
456        let content_mask = self.content_mask().scale(scale_factor);
457        let corner_radii = corner_radii.scale(scale_factor);
458
459        self.window.scene.insert(
460            order,
461            PolychromeSprite {
462                order: 0,
463                bounds,
464                content_mask,
465                corner_radii,
466                tile,
467                grayscale,
468            },
469        );
470
471        Ok(())
472    }
473
474    pub(crate) fn draw(&mut self) -> Result<()> {
475        let unit_entity = self.unit_entity.clone();
476        self.update_entity(&unit_entity, |view, cx| {
477            let mut root_view = cx.window.root_view.take().unwrap();
478            let (root_layout_id, mut frame_state) = root_view.layout(&mut (), cx)?;
479            let available_space = cx.window.content_size.map(Into::into);
480
481            cx.window
482                .layout_engine
483                .compute_layout(root_layout_id, available_space)?;
484            let layout = cx.window.layout_engine.layout_bounds(root_layout_id)?;
485
486            root_view.paint(layout, &mut (), &mut frame_state, cx)?;
487            cx.window.root_view = Some(root_view);
488            let scene = cx.window.scene.take();
489
490            cx.run_on_main(view, |_, cx| {
491                cx.window
492                    .platform_window
493                    .borrow_on_main_thread()
494                    .draw(scene);
495                cx.window.dirty = false;
496            })
497            .detach();
498
499            Ok(())
500        })
501    }
502}
503
504impl Context for WindowContext<'_, '_> {
505    type EntityContext<'a, 'w, T: 'static + Send + Sync> = ViewContext<'a, 'w, T>;
506    type Result<T> = T;
507
508    fn entity<T: Send + Sync + 'static>(
509        &mut self,
510        build_entity: impl FnOnce(&mut Self::EntityContext<'_, '_, T>) -> T,
511    ) -> Handle<T> {
512        let slot = self.app.entities.reserve();
513        let entity = build_entity(&mut ViewContext::mutable(
514            &mut *self.app,
515            &mut self.window,
516            slot.id,
517        ));
518        self.entities.insert(slot, entity)
519    }
520
521    fn update_entity<T: Send + Sync + 'static, R>(
522        &mut self,
523        handle: &Handle<T>,
524        update: impl FnOnce(&mut T, &mut Self::EntityContext<'_, '_, T>) -> R,
525    ) -> R {
526        let mut entity = self.entities.lease(handle);
527        let result = update(
528            &mut *entity,
529            &mut ViewContext::mutable(&mut *self.app, &mut *self.window, handle.id),
530        );
531        self.entities.end_lease(entity);
532        result
533    }
534}
535
536impl<'a, 'w> std::ops::Deref for WindowContext<'a, 'w> {
537    type Target = AppContext;
538
539    fn deref(&self) -> &Self::Target {
540        &self.app
541    }
542}
543
544impl<'a, 'w> std::ops::DerefMut for WindowContext<'a, 'w> {
545    fn deref_mut(&mut self) -> &mut Self::Target {
546        &mut self.app
547    }
548}
549
550impl BorrowAppContext for WindowContext<'_, '_> {
551    fn app_mut(&mut self) -> &mut AppContext {
552        &mut *self.app
553    }
554}
555
556pub trait BorrowWindow: BorrowAppContext {
557    fn window(&self) -> &Window;
558    fn window_mut(&mut self) -> &mut Window;
559
560    fn with_content_mask<R>(&mut self, mask: ContentMask, f: impl FnOnce(&mut Self) -> R) -> R {
561        let mask = mask.intersect(&self.content_mask());
562        self.window_mut().content_mask_stack.push(mask);
563        let result = f(self);
564        self.window_mut().content_mask_stack.pop();
565        result
566    }
567
568    fn content_mask(&self) -> ContentMask {
569        self.window()
570            .content_mask_stack
571            .last()
572            .cloned()
573            .unwrap_or_else(|| ContentMask {
574                bounds: Bounds {
575                    origin: Point::default(),
576                    size: self.window().content_size,
577                },
578            })
579    }
580
581    fn rem_size(&self) -> Pixels {
582        self.window().rem_size
583    }
584}
585
586impl BorrowWindow for WindowContext<'_, '_> {
587    fn window(&self) -> &Window {
588        &*self.window
589    }
590
591    fn window_mut(&mut self) -> &mut Window {
592        &mut *self.window
593    }
594}
595
596pub struct ViewContext<'a, 'w, S> {
597    window_cx: WindowContext<'a, 'w>,
598    entity_type: PhantomData<S>,
599    entity_id: EntityId,
600}
601
602impl<S> BorrowAppContext for ViewContext<'_, '_, S> {
603    fn app_mut(&mut self) -> &mut AppContext {
604        &mut *self.window_cx.app
605    }
606
607    fn with_text_style<F, R>(&mut self, style: crate::TextStyleRefinement, f: F) -> R
608    where
609        F: FnOnce(&mut Self) -> R,
610    {
611        self.window_cx.app.push_text_style(style);
612        let result = f(self);
613        self.window_cx.app.pop_text_style();
614        result
615    }
616
617    fn with_state<T: Send + Sync + 'static, F, R>(&mut self, state: T, f: F) -> R
618    where
619        F: FnOnce(&mut Self) -> R,
620    {
621        self.window_cx.app.push_state(state);
622        let result = f(self);
623        self.window_cx.app.pop_state::<T>();
624        result
625    }
626}
627
628impl<S> BorrowWindow for ViewContext<'_, '_, S> {
629    fn window(&self) -> &Window {
630        &self.window_cx.window
631    }
632
633    fn window_mut(&mut self) -> &mut Window {
634        &mut *self.window_cx.window
635    }
636}
637
638impl<'a, 'w, S: Send + Sync + 'static> ViewContext<'a, 'w, S> {
639    fn mutable(app: &'a mut AppContext, window: &'w mut Window, entity_id: EntityId) -> Self {
640        Self {
641            window_cx: WindowContext::mutable(app, window),
642            entity_id,
643            entity_type: PhantomData,
644        }
645    }
646
647    pub fn handle(&self) -> WeakHandle<S> {
648        self.entities.weak_handle(self.entity_id)
649    }
650
651    pub fn stack<R>(&mut self, order: u32, f: impl FnOnce(&mut Self) -> R) -> R {
652        self.window.current_stacking_order.push(order);
653        let result = f(self);
654        self.window.current_stacking_order.pop();
655        result
656    }
657
658    pub fn on_next_frame(&mut self, f: impl FnOnce(&mut S, &mut ViewContext<S>) + Send + 'static) {
659        let entity = self.handle();
660        self.window_cx.on_next_frame(move |cx| {
661            entity.update(cx, f).ok();
662        });
663    }
664
665    pub fn observe<E: Send + Sync + 'static>(
666        &mut self,
667        handle: &Handle<E>,
668        on_notify: impl Fn(&mut S, Handle<E>, &mut ViewContext<'_, '_, S>) + Send + Sync + 'static,
669    ) {
670        let this = self.handle();
671        let handle = handle.downgrade();
672        let window_handle = self.window.handle;
673        self.app
674            .observers
675            .entry(handle.id)
676            .or_default()
677            .push(Arc::new(move |cx| {
678                cx.update_window(window_handle.id, |cx| {
679                    if let Some(handle) = handle.upgrade(cx) {
680                        this.update(cx, |this, cx| on_notify(this, handle, cx))
681                            .is_ok()
682                    } else {
683                        false
684                    }
685                })
686                .unwrap_or(false)
687            }));
688    }
689
690    pub fn notify(&mut self) {
691        self.window_cx.notify();
692        self.window_cx
693            .app
694            .pending_effects
695            .push_back(Effect::Notify(self.entity_id));
696    }
697
698    pub fn run_on_main<R>(
699        &mut self,
700        view: &mut S,
701        f: impl FnOnce(&mut S, &mut MainThread<ViewContext<'_, '_, S>>) -> R + Send + 'static,
702    ) -> Task<Result<R>>
703    where
704        R: Send + 'static,
705    {
706        if self.executor.is_main_thread() {
707            let cx = unsafe { mem::transmute::<&mut Self, &mut MainThread<Self>>(self) };
708            Task::ready(Ok(f(view, cx)))
709        } else {
710            let handle = self.handle().upgrade(self).unwrap();
711            self.window_cx.run_on_main(move |cx| handle.update(cx, f))
712        }
713    }
714
715    pub fn spawn<Fut, R>(
716        &mut self,
717        f: impl FnOnce(WeakHandle<S>, AsyncWindowContext) -> Fut + Send + 'static,
718    ) -> Task<R>
719    where
720        R: Send + 'static,
721        Fut: Future<Output = R> + Send + 'static,
722    {
723        let handle = self.handle();
724        self.window_cx.spawn(move |_, cx| {
725            let result = f(handle, cx);
726            async move { result.await }
727        })
728    }
729
730    pub(crate) fn erase_state<R>(&mut self, f: impl FnOnce(&mut ViewContext<()>) -> R) -> R {
731        let entity_id = self.unit_entity.id;
732        let mut cx = ViewContext::mutable(
733            &mut *self.window_cx.app,
734            &mut *self.window_cx.window,
735            entity_id,
736        );
737        f(&mut cx)
738    }
739}
740
741impl<'a, 'w, S> Context for ViewContext<'a, 'w, S> {
742    type EntityContext<'b, 'c, U: 'static + Send + Sync> = ViewContext<'b, 'c, U>;
743    type Result<U> = U;
744
745    fn entity<T2: Send + Sync + 'static>(
746        &mut self,
747        build_entity: impl FnOnce(&mut Self::EntityContext<'_, '_, T2>) -> T2,
748    ) -> Handle<T2> {
749        self.window_cx.entity(build_entity)
750    }
751
752    fn update_entity<U: Send + Sync + 'static, R>(
753        &mut self,
754        handle: &Handle<U>,
755        update: impl FnOnce(&mut U, &mut Self::EntityContext<'_, '_, U>) -> R,
756    ) -> R {
757        self.window_cx.update_entity(handle, update)
758    }
759}
760
761impl<'a, 'w, S: 'static> std::ops::Deref for ViewContext<'a, 'w, S> {
762    type Target = WindowContext<'a, 'w>;
763
764    fn deref(&self) -> &Self::Target {
765        &self.window_cx
766    }
767}
768
769impl<'a, 'w, S: 'static> std::ops::DerefMut for ViewContext<'a, 'w, S> {
770    fn deref_mut(&mut self) -> &mut Self::Target {
771        &mut self.window_cx
772    }
773}
774
775// #[derive(Clone, Copy, Eq, PartialEq, Hash)]
776slotmap::new_key_type! { pub struct WindowId; }
777
778#[derive(PartialEq, Eq)]
779pub struct WindowHandle<S> {
780    id: WindowId,
781    state_type: PhantomData<S>,
782}
783
784impl<S> Copy for WindowHandle<S> {}
785
786impl<S> Clone for WindowHandle<S> {
787    fn clone(&self) -> Self {
788        WindowHandle {
789            id: self.id,
790            state_type: PhantomData,
791        }
792    }
793}
794
795impl<S> WindowHandle<S> {
796    pub fn new(id: WindowId) -> Self {
797        WindowHandle {
798            id,
799            state_type: PhantomData,
800        }
801    }
802}
803
804impl<S: 'static> Into<AnyWindowHandle> for WindowHandle<S> {
805    fn into(self) -> AnyWindowHandle {
806        AnyWindowHandle {
807            id: self.id,
808            state_type: TypeId::of::<S>(),
809        }
810    }
811}
812
813#[derive(Copy, Clone, PartialEq, Eq)]
814pub struct AnyWindowHandle {
815    pub(crate) id: WindowId,
816    state_type: TypeId,
817}