app.rs

   1use crate::{
   2    elements::ElementBox,
   3    executor,
   4    keymap::{self, Keystroke},
   5    platform::{self, Platform, PromptLevel, WindowOptions},
   6    presenter::Presenter,
   7    util::{post_inc, timeout},
   8    AssetCache, AssetSource, ClipboardItem, FontCache, PathPromptOptions, TextLayoutCache,
   9};
  10use anyhow::{anyhow, Result};
  11use async_task::Task;
  12use keymap::MatchResult;
  13use parking_lot::{Mutex, RwLock};
  14use pathfinder_geometry::{rect::RectF, vector::vec2f};
  15use platform::Event;
  16use postage::{mpsc, sink::Sink as _, stream::Stream as _};
  17use smol::prelude::*;
  18use std::{
  19    any::{type_name, Any, TypeId},
  20    cell::RefCell,
  21    collections::{hash_map::Entry, HashMap, HashSet, VecDeque},
  22    fmt::{self, Debug},
  23    hash::{Hash, Hasher},
  24    marker::PhantomData,
  25    path::{Path, PathBuf},
  26    rc::{self, Rc},
  27    sync::{Arc, Weak},
  28    time::Duration,
  29};
  30
  31pub trait Entity: 'static + Send + Sync {
  32    type Event;
  33
  34    fn release(&mut self, _: &mut MutableAppContext) {}
  35}
  36
  37pub trait View: Entity {
  38    fn ui_name() -> &'static str;
  39    fn render<'a>(&self, cx: &AppContext) -> ElementBox;
  40    fn on_focus(&mut self, _: &mut ViewContext<Self>) {}
  41    fn on_blur(&mut self, _: &mut ViewContext<Self>) {}
  42    fn keymap_context(&self, _: &AppContext) -> keymap::Context {
  43        Self::default_keymap_context()
  44    }
  45    fn default_keymap_context() -> keymap::Context {
  46        let mut cx = keymap::Context::default();
  47        cx.set.insert(Self::ui_name().into());
  48        cx
  49    }
  50}
  51
  52pub trait ReadModel {
  53    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T;
  54}
  55
  56pub trait ReadModelWith {
  57    fn read_model_with<E: Entity, F: FnOnce(&E, &AppContext) -> T, T>(
  58        &self,
  59        handle: &ModelHandle<E>,
  60        read: F,
  61    ) -> T;
  62}
  63
  64pub trait UpdateModel {
  65    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
  66    where
  67        T: Entity,
  68        F: FnOnce(&mut T, &mut ModelContext<T>) -> S;
  69}
  70
  71pub trait ReadView {
  72    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T;
  73}
  74
  75pub trait ReadViewWith {
  76    fn read_view_with<V, F, T>(&self, handle: &ViewHandle<V>, read: F) -> T
  77    where
  78        V: View,
  79        F: FnOnce(&V, &AppContext) -> T;
  80}
  81
  82pub trait UpdateView {
  83    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
  84    where
  85        T: View,
  86        F: FnOnce(&mut T, &mut ViewContext<T>) -> S;
  87}
  88
  89pub struct Menu<'a> {
  90    pub name: &'a str,
  91    pub items: Vec<MenuItem<'a>>,
  92}
  93
  94pub enum MenuItem<'a> {
  95    Action {
  96        name: &'a str,
  97        keystroke: Option<&'a str>,
  98        action: &'a str,
  99        arg: Option<Box<dyn Any + 'static>>,
 100    },
 101    Separator,
 102}
 103
 104#[derive(Clone)]
 105pub struct App(Rc<RefCell<MutableAppContext>>);
 106
 107#[derive(Clone)]
 108pub struct AsyncAppContext(Rc<RefCell<MutableAppContext>>);
 109
 110pub struct BackgroundAppContext(*const RefCell<MutableAppContext>);
 111
 112#[derive(Clone)]
 113pub struct TestAppContext {
 114    cx: Rc<RefCell<MutableAppContext>>,
 115    foreground_platform: Rc<platform::test::ForegroundPlatform>,
 116}
 117
 118impl App {
 119    pub fn test<T, F: FnOnce(&mut MutableAppContext) -> T>(f: F) -> T {
 120        let foreground_platform = platform::test::foreground_platform();
 121        let platform = platform::test::platform();
 122        let foreground = Rc::new(executor::Foreground::test());
 123        let cx = Rc::new(RefCell::new(MutableAppContext::new(
 124            foreground,
 125            Arc::new(executor::Background::new()),
 126            Arc::new(platform),
 127            Rc::new(foreground_platform),
 128            (),
 129        )));
 130        cx.borrow_mut().weak_self = Some(Rc::downgrade(&cx));
 131        let mut cx = cx.borrow_mut();
 132        f(&mut *cx)
 133    }
 134
 135    pub fn new(asset_source: impl AssetSource) -> Result<Self> {
 136        let platform = platform::current::platform();
 137        let foreground_platform = platform::current::foreground_platform();
 138        let foreground = Rc::new(executor::Foreground::platform(platform.dispatcher())?);
 139        let app = Self(Rc::new(RefCell::new(MutableAppContext::new(
 140            foreground,
 141            Arc::new(executor::Background::new()),
 142            platform.clone(),
 143            foreground_platform.clone(),
 144            asset_source,
 145        ))));
 146
 147        let cx = app.0.clone();
 148        foreground_platform.on_menu_command(Box::new(move |command, arg| {
 149            let mut cx = cx.borrow_mut();
 150            if let Some(key_window_id) = cx.cx.platform.key_window_id() {
 151                if let Some((presenter, _)) = cx.presenters_and_platform_windows.get(&key_window_id)
 152                {
 153                    let presenter = presenter.clone();
 154                    let path = presenter.borrow().dispatch_path(cx.as_ref());
 155                    cx.dispatch_action_any(key_window_id, &path, command, arg.unwrap_or(&()));
 156                } else {
 157                    cx.dispatch_global_action_any(command, arg.unwrap_or(&()));
 158                }
 159            } else {
 160                cx.dispatch_global_action_any(command, arg.unwrap_or(&()));
 161            }
 162        }));
 163
 164        app.0.borrow_mut().weak_self = Some(Rc::downgrade(&app.0));
 165        Ok(app)
 166    }
 167
 168    pub fn on_become_active<F>(self, mut callback: F) -> Self
 169    where
 170        F: 'static + FnMut(&mut MutableAppContext),
 171    {
 172        let cx = self.0.clone();
 173        self.0
 174            .borrow_mut()
 175            .foreground_platform
 176            .on_become_active(Box::new(move || callback(&mut *cx.borrow_mut())));
 177        self
 178    }
 179
 180    pub fn on_resign_active<F>(self, mut callback: F) -> Self
 181    where
 182        F: 'static + FnMut(&mut MutableAppContext),
 183    {
 184        let cx = self.0.clone();
 185        self.0
 186            .borrow_mut()
 187            .foreground_platform
 188            .on_resign_active(Box::new(move || callback(&mut *cx.borrow_mut())));
 189        self
 190    }
 191
 192    pub fn on_event<F>(self, mut callback: F) -> Self
 193    where
 194        F: 'static + FnMut(Event, &mut MutableAppContext) -> bool,
 195    {
 196        let cx = self.0.clone();
 197        self.0
 198            .borrow_mut()
 199            .foreground_platform
 200            .on_event(Box::new(move |event| {
 201                callback(event, &mut *cx.borrow_mut())
 202            }));
 203        self
 204    }
 205
 206    pub fn on_open_files<F>(self, mut callback: F) -> Self
 207    where
 208        F: 'static + FnMut(Vec<PathBuf>, &mut MutableAppContext),
 209    {
 210        let cx = self.0.clone();
 211        self.0
 212            .borrow_mut()
 213            .foreground_platform
 214            .on_open_files(Box::new(move |paths| {
 215                callback(paths, &mut *cx.borrow_mut())
 216            }));
 217        self
 218    }
 219
 220    pub fn run<F>(self, on_finish_launching: F)
 221    where
 222        F: 'static + FnOnce(&mut MutableAppContext),
 223    {
 224        let platform = self.0.borrow().foreground_platform.clone();
 225        platform.run(Box::new(move || {
 226            let mut cx = self.0.borrow_mut();
 227            on_finish_launching(&mut *cx);
 228        }))
 229    }
 230
 231    pub fn font_cache(&self) -> Arc<FontCache> {
 232        self.0.borrow().cx.font_cache.clone()
 233    }
 234
 235    fn update<T, F: FnOnce(&mut MutableAppContext) -> T>(&mut self, callback: F) -> T {
 236        let mut state = self.0.borrow_mut();
 237        state.pending_flushes += 1;
 238        let result = callback(&mut *state);
 239        state.flush_effects();
 240        result
 241    }
 242}
 243
 244impl TestAppContext {
 245    pub fn new(
 246        foreground: Rc<executor::Foreground>,
 247        background: Arc<executor::Background>,
 248        first_entity_id: usize,
 249    ) -> Self {
 250        let platform = Arc::new(platform::test::platform());
 251        let foreground_platform = Rc::new(platform::test::foreground_platform());
 252        let mut cx = MutableAppContext::new(
 253            foreground.clone(),
 254            background,
 255            platform,
 256            foreground_platform.clone(),
 257            (),
 258        );
 259        cx.next_entity_id = first_entity_id;
 260        let cx = TestAppContext {
 261            cx: Rc::new(RefCell::new(cx)),
 262            foreground_platform,
 263        };
 264        cx.cx.borrow_mut().weak_self = Some(Rc::downgrade(&cx.cx));
 265        cx
 266    }
 267
 268    pub fn dispatch_action<T: 'static + Any>(
 269        &self,
 270        window_id: usize,
 271        responder_chain: Vec<usize>,
 272        name: &str,
 273        arg: T,
 274    ) {
 275        self.cx.borrow_mut().dispatch_action_any(
 276            window_id,
 277            &responder_chain,
 278            name,
 279            Box::new(arg).as_ref(),
 280        );
 281    }
 282
 283    pub fn dispatch_global_action<T: 'static + Any>(&self, name: &str, arg: T) {
 284        self.cx.borrow_mut().dispatch_global_action(name, arg);
 285    }
 286
 287    pub fn dispatch_keystroke(
 288        &self,
 289        window_id: usize,
 290        responder_chain: Vec<usize>,
 291        keystroke: &Keystroke,
 292    ) -> Result<bool> {
 293        let mut state = self.cx.borrow_mut();
 294        state.dispatch_keystroke(window_id, responder_chain, keystroke)
 295    }
 296
 297    pub fn add_model<T, F>(&mut self, build_model: F) -> ModelHandle<T>
 298    where
 299        T: Entity,
 300        F: FnOnce(&mut ModelContext<T>) -> T,
 301    {
 302        let mut state = self.cx.borrow_mut();
 303        state.pending_flushes += 1;
 304        let handle = state.add_model(build_model);
 305        state.flush_effects();
 306        handle
 307    }
 308
 309    pub fn add_window<T, F>(&mut self, build_root_view: F) -> (usize, ViewHandle<T>)
 310    where
 311        T: View,
 312        F: FnOnce(&mut ViewContext<T>) -> T,
 313    {
 314        self.cx.borrow_mut().add_window(build_root_view)
 315    }
 316
 317    pub fn window_ids(&self) -> Vec<usize> {
 318        self.cx.borrow().window_ids().collect()
 319    }
 320
 321    pub fn root_view<T: View>(&self, window_id: usize) -> Option<ViewHandle<T>> {
 322        self.cx.borrow().root_view(window_id)
 323    }
 324
 325    pub fn add_view<T, F>(&mut self, window_id: usize, build_view: F) -> ViewHandle<T>
 326    where
 327        T: View,
 328        F: FnOnce(&mut ViewContext<T>) -> T,
 329    {
 330        let mut state = self.cx.borrow_mut();
 331        state.pending_flushes += 1;
 332        let handle = state.add_view(window_id, build_view);
 333        state.flush_effects();
 334        handle
 335    }
 336
 337    pub fn add_option_view<T, F>(
 338        &mut self,
 339        window_id: usize,
 340        build_view: F,
 341    ) -> Option<ViewHandle<T>>
 342    where
 343        T: View,
 344        F: FnOnce(&mut ViewContext<T>) -> Option<T>,
 345    {
 346        let mut state = self.cx.borrow_mut();
 347        state.pending_flushes += 1;
 348        let handle = state.add_option_view(window_id, build_view);
 349        state.flush_effects();
 350        handle
 351    }
 352
 353    pub fn read<T, F: FnOnce(&AppContext) -> T>(&self, callback: F) -> T {
 354        callback(self.cx.borrow().as_ref())
 355    }
 356
 357    pub fn update<T, F: FnOnce(&mut MutableAppContext) -> T>(&mut self, callback: F) -> T {
 358        let mut state = self.cx.borrow_mut();
 359        // Don't increment pending flushes in order to effects to be flushed before the callback
 360        // completes, which is helpful in tests.
 361        let result = callback(&mut *state);
 362        // Flush effects after the callback just in case there are any. This can happen in edge
 363        // cases such as the closure dropping handles.
 364        state.flush_effects();
 365        result
 366    }
 367
 368    pub fn to_async(&self) -> AsyncAppContext {
 369        AsyncAppContext(self.cx.clone())
 370    }
 371
 372    pub fn font_cache(&self) -> Arc<FontCache> {
 373        self.cx.borrow().cx.font_cache.clone()
 374    }
 375
 376    pub fn platform(&self) -> Arc<dyn platform::Platform> {
 377        self.cx.borrow().cx.platform.clone()
 378    }
 379
 380    pub fn foreground(&self) -> Rc<executor::Foreground> {
 381        self.cx.borrow().foreground().clone()
 382    }
 383
 384    pub fn background(&self) -> Arc<executor::Background> {
 385        self.cx.borrow().background().clone()
 386    }
 387
 388    pub fn simulate_new_path_selection(&self, result: impl FnOnce(PathBuf) -> Option<PathBuf>) {
 389        self.foreground_platform.simulate_new_path_selection(result);
 390    }
 391
 392    pub fn did_prompt_for_new_path(&self) -> bool {
 393        self.foreground_platform.as_ref().did_prompt_for_new_path()
 394    }
 395
 396    pub fn simulate_prompt_answer(&self, window_id: usize, answer: usize) {
 397        let mut state = self.cx.borrow_mut();
 398        let (_, window) = state
 399            .presenters_and_platform_windows
 400            .get_mut(&window_id)
 401            .unwrap();
 402        let test_window = window
 403            .as_any_mut()
 404            .downcast_mut::<platform::test::Window>()
 405            .unwrap();
 406        let callback = test_window
 407            .last_prompt
 408            .take()
 409            .expect("prompt was not called");
 410        (callback)(answer);
 411    }
 412}
 413
 414impl AsyncAppContext {
 415    pub fn spawn<F, Fut, T>(&self, f: F) -> Task<T>
 416    where
 417        F: FnOnce(AsyncAppContext) -> Fut,
 418        Fut: 'static + Future<Output = T>,
 419        T: 'static,
 420    {
 421        self.0.borrow().foreground.spawn(f(self.clone()))
 422    }
 423
 424    pub fn read<T, F: FnOnce(&AppContext) -> T>(&mut self, callback: F) -> T {
 425        callback(self.0.borrow().as_ref())
 426    }
 427
 428    pub fn update<T, F: FnOnce(&mut MutableAppContext) -> T>(&mut self, callback: F) -> T {
 429        let mut state = self.0.borrow_mut();
 430        state.pending_flushes += 1;
 431        let result = callback(&mut *state);
 432        state.flush_effects();
 433        result
 434    }
 435
 436    pub fn add_model<T, F>(&mut self, build_model: F) -> ModelHandle<T>
 437    where
 438        T: Entity,
 439        F: FnOnce(&mut ModelContext<T>) -> T,
 440    {
 441        self.update(|cx| cx.add_model(build_model))
 442    }
 443
 444    pub fn platform(&self) -> Arc<dyn Platform> {
 445        self.0.borrow().platform()
 446    }
 447
 448    pub fn foreground(&self) -> Rc<executor::Foreground> {
 449        self.0.borrow().foreground.clone()
 450    }
 451
 452    pub fn background(&self) -> Arc<executor::Background> {
 453        self.0.borrow().cx.background.clone()
 454    }
 455}
 456
 457impl UpdateModel for AsyncAppContext {
 458    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
 459    where
 460        T: Entity,
 461        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
 462    {
 463        let mut state = self.0.borrow_mut();
 464        state.pending_flushes += 1;
 465        let result = state.update_model(handle, update);
 466        state.flush_effects();
 467        result
 468    }
 469}
 470
 471impl ReadModelWith for AsyncAppContext {
 472    fn read_model_with<E: Entity, F: FnOnce(&E, &AppContext) -> T, T>(
 473        &self,
 474        handle: &ModelHandle<E>,
 475        read: F,
 476    ) -> T {
 477        let cx = self.0.borrow();
 478        let cx = cx.as_ref();
 479        read(handle.read(cx), cx)
 480    }
 481}
 482
 483impl UpdateView for AsyncAppContext {
 484    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
 485    where
 486        T: View,
 487        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
 488    {
 489        let mut state = self.0.borrow_mut();
 490        state.pending_flushes += 1;
 491        let result = state.update_view(handle, update);
 492        state.flush_effects();
 493        result
 494    }
 495}
 496
 497impl ReadViewWith for AsyncAppContext {
 498    fn read_view_with<V, F, T>(&self, handle: &ViewHandle<V>, read: F) -> T
 499    where
 500        V: View,
 501        F: FnOnce(&V, &AppContext) -> T,
 502    {
 503        let cx = self.0.borrow();
 504        let cx = cx.as_ref();
 505        read(handle.read(cx), cx)
 506    }
 507}
 508
 509impl UpdateModel for TestAppContext {
 510    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
 511    where
 512        T: Entity,
 513        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
 514    {
 515        let mut state = self.cx.borrow_mut();
 516        state.pending_flushes += 1;
 517        let result = state.update_model(handle, update);
 518        state.flush_effects();
 519        result
 520    }
 521}
 522
 523impl ReadModelWith for TestAppContext {
 524    fn read_model_with<E: Entity, F: FnOnce(&E, &AppContext) -> T, T>(
 525        &self,
 526        handle: &ModelHandle<E>,
 527        read: F,
 528    ) -> T {
 529        let cx = self.cx.borrow();
 530        let cx = cx.as_ref();
 531        read(handle.read(cx), cx)
 532    }
 533}
 534
 535impl UpdateView for TestAppContext {
 536    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
 537    where
 538        T: View,
 539        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
 540    {
 541        let mut state = self.cx.borrow_mut();
 542        state.pending_flushes += 1;
 543        let result = state.update_view(handle, update);
 544        state.flush_effects();
 545        result
 546    }
 547}
 548
 549impl ReadViewWith for TestAppContext {
 550    fn read_view_with<V, F, T>(&self, handle: &ViewHandle<V>, read: F) -> T
 551    where
 552        V: View,
 553        F: FnOnce(&V, &AppContext) -> T,
 554    {
 555        let cx = self.cx.borrow();
 556        let cx = cx.as_ref();
 557        read(handle.read(cx), cx)
 558    }
 559}
 560
 561type ActionCallback =
 562    dyn FnMut(&mut dyn AnyView, &dyn Any, &mut MutableAppContext, usize, usize) -> bool;
 563
 564type GlobalActionCallback = dyn FnMut(&dyn Any, &mut MutableAppContext);
 565
 566pub struct MutableAppContext {
 567    weak_self: Option<rc::Weak<RefCell<Self>>>,
 568    foreground_platform: Rc<dyn platform::ForegroundPlatform>,
 569    assets: Arc<AssetCache>,
 570    cx: AppContext,
 571    actions: HashMap<TypeId, HashMap<String, Vec<Box<ActionCallback>>>>,
 572    global_actions: HashMap<String, Vec<Box<GlobalActionCallback>>>,
 573    keystroke_matcher: keymap::Matcher,
 574    next_entity_id: usize,
 575    next_window_id: usize,
 576    subscriptions: HashMap<usize, Vec<Subscription>>,
 577    model_observations: HashMap<usize, Vec<ModelObservation>>,
 578    view_observations: HashMap<usize, Vec<ViewObservation>>,
 579    presenters_and_platform_windows:
 580        HashMap<usize, (Rc<RefCell<Presenter>>, Box<dyn platform::Window>)>,
 581    debug_elements_callbacks: HashMap<usize, Box<dyn Fn(&AppContext) -> crate::json::Value>>,
 582    foreground: Rc<executor::Foreground>,
 583    pending_effects: VecDeque<Effect>,
 584    pending_flushes: usize,
 585    flushing_effects: bool,
 586}
 587
 588impl MutableAppContext {
 589    fn new(
 590        foreground: Rc<executor::Foreground>,
 591        background: Arc<executor::Background>,
 592        platform: Arc<dyn platform::Platform>,
 593        foreground_platform: Rc<dyn platform::ForegroundPlatform>,
 594        asset_source: impl AssetSource,
 595    ) -> Self {
 596        let fonts = platform.fonts();
 597        Self {
 598            weak_self: None,
 599            foreground_platform,
 600            assets: Arc::new(AssetCache::new(asset_source)),
 601            cx: AppContext {
 602                models: Default::default(),
 603                views: Default::default(),
 604                windows: Default::default(),
 605                values: Default::default(),
 606                ref_counts: Arc::new(Mutex::new(RefCounts::default())),
 607                background,
 608                font_cache: Arc::new(FontCache::new(fonts)),
 609                platform,
 610            },
 611            actions: HashMap::new(),
 612            global_actions: HashMap::new(),
 613            keystroke_matcher: keymap::Matcher::default(),
 614            next_entity_id: 0,
 615            next_window_id: 0,
 616            subscriptions: HashMap::new(),
 617            model_observations: HashMap::new(),
 618            view_observations: HashMap::new(),
 619            presenters_and_platform_windows: HashMap::new(),
 620            debug_elements_callbacks: HashMap::new(),
 621            foreground,
 622            pending_effects: VecDeque::new(),
 623            pending_flushes: 0,
 624            flushing_effects: false,
 625        }
 626    }
 627
 628    pub fn upgrade(&self) -> App {
 629        App(self.weak_self.as_ref().unwrap().upgrade().unwrap())
 630    }
 631
 632    pub fn platform(&self) -> Arc<dyn platform::Platform> {
 633        self.cx.platform.clone()
 634    }
 635
 636    pub fn font_cache(&self) -> &Arc<FontCache> {
 637        &self.cx.font_cache
 638    }
 639
 640    pub fn foreground(&self) -> &Rc<executor::Foreground> {
 641        &self.foreground
 642    }
 643
 644    pub fn background(&self) -> &Arc<executor::Background> {
 645        &self.cx.background
 646    }
 647
 648    pub fn on_debug_elements<F>(&mut self, window_id: usize, callback: F)
 649    where
 650        F: 'static + Fn(&AppContext) -> crate::json::Value,
 651    {
 652        self.debug_elements_callbacks
 653            .insert(window_id, Box::new(callback));
 654    }
 655
 656    pub fn debug_elements(&self, window_id: usize) -> Option<crate::json::Value> {
 657        self.debug_elements_callbacks
 658            .get(&window_id)
 659            .map(|debug_elements| debug_elements(&self.cx))
 660    }
 661
 662    pub fn add_action<S, V, T, F>(&mut self, name: S, mut handler: F)
 663    where
 664        S: Into<String>,
 665        V: View,
 666        T: Any,
 667        F: 'static + FnMut(&mut V, &T, &mut ViewContext<V>),
 668    {
 669        let name = name.into();
 670        let name_clone = name.clone();
 671        let handler = Box::new(
 672            move |view: &mut dyn AnyView,
 673                  arg: &dyn Any,
 674                  cx: &mut MutableAppContext,
 675                  window_id: usize,
 676                  view_id: usize| {
 677                match arg.downcast_ref() {
 678                    Some(arg) => {
 679                        let mut cx = ViewContext::new(cx, window_id, view_id);
 680                        handler(
 681                            view.as_any_mut()
 682                                .downcast_mut()
 683                                .expect("downcast is type safe"),
 684                            arg,
 685                            &mut cx,
 686                        );
 687                        cx.halt_action_dispatch
 688                    }
 689                    None => {
 690                        log::error!("Could not downcast argument for action {}", name_clone);
 691                        false
 692                    }
 693                }
 694            },
 695        );
 696
 697        self.actions
 698            .entry(TypeId::of::<V>())
 699            .or_default()
 700            .entry(name)
 701            .or_default()
 702            .push(handler);
 703    }
 704
 705    pub fn add_global_action<S, T, F>(&mut self, name: S, mut handler: F)
 706    where
 707        S: Into<String>,
 708        T: 'static + Any,
 709        F: 'static + FnMut(&T, &mut MutableAppContext),
 710    {
 711        let name = name.into();
 712        let name_clone = name.clone();
 713        let handler = Box::new(move |arg: &dyn Any, cx: &mut MutableAppContext| {
 714            if let Some(arg) = arg.downcast_ref() {
 715                handler(arg, cx);
 716            } else {
 717                log::error!("Could not downcast argument for action {}", name_clone);
 718            }
 719        });
 720
 721        self.global_actions.entry(name).or_default().push(handler);
 722    }
 723
 724    pub fn window_ids(&self) -> impl Iterator<Item = usize> + '_ {
 725        self.cx.windows.keys().cloned()
 726    }
 727
 728    pub fn root_view<T: View>(&self, window_id: usize) -> Option<ViewHandle<T>> {
 729        self.cx
 730            .windows
 731            .get(&window_id)
 732            .and_then(|window| window.root_view.clone().downcast::<T>())
 733    }
 734
 735    pub fn root_view_id(&self, window_id: usize) -> Option<usize> {
 736        self.cx.root_view_id(window_id)
 737    }
 738
 739    pub fn focused_view_id(&self, window_id: usize) -> Option<usize> {
 740        self.cx.focused_view_id(window_id)
 741    }
 742
 743    pub fn render_view(&self, window_id: usize, view_id: usize) -> Result<ElementBox> {
 744        self.cx.render_view(window_id, view_id)
 745    }
 746
 747    pub fn render_views(&self, window_id: usize) -> HashMap<usize, ElementBox> {
 748        self.cx.render_views(window_id)
 749    }
 750
 751    pub fn update<T, F: FnOnce() -> T>(&mut self, callback: F) -> T {
 752        self.pending_flushes += 1;
 753        let result = callback();
 754        self.flush_effects();
 755        result
 756    }
 757
 758    pub fn set_menus(&mut self, menus: Vec<Menu>) {
 759        self.foreground_platform.set_menus(menus);
 760    }
 761
 762    fn prompt<F>(
 763        &self,
 764        window_id: usize,
 765        level: PromptLevel,
 766        msg: &str,
 767        answers: &[&str],
 768        done_fn: F,
 769    ) where
 770        F: 'static + FnOnce(usize, &mut MutableAppContext),
 771    {
 772        let app = self.weak_self.as_ref().unwrap().upgrade().unwrap();
 773        let foreground = self.foreground.clone();
 774        let (_, window) = &self.presenters_and_platform_windows[&window_id];
 775        window.prompt(
 776            level,
 777            msg,
 778            answers,
 779            Box::new(move |answer| {
 780                foreground
 781                    .spawn(async move { (done_fn)(answer, &mut *app.borrow_mut()) })
 782                    .detach();
 783            }),
 784        );
 785    }
 786
 787    pub fn prompt_for_paths<F>(&self, options: PathPromptOptions, done_fn: F)
 788    where
 789        F: 'static + FnOnce(Option<Vec<PathBuf>>, &mut MutableAppContext),
 790    {
 791        let app = self.weak_self.as_ref().unwrap().upgrade().unwrap();
 792        let foreground = self.foreground.clone();
 793        self.foreground_platform.prompt_for_paths(
 794            options,
 795            Box::new(move |paths| {
 796                foreground
 797                    .spawn(async move { (done_fn)(paths, &mut *app.borrow_mut()) })
 798                    .detach();
 799            }),
 800        );
 801    }
 802
 803    pub fn prompt_for_new_path<F>(&self, directory: &Path, done_fn: F)
 804    where
 805        F: 'static + FnOnce(Option<PathBuf>, &mut MutableAppContext),
 806    {
 807        let app = self.weak_self.as_ref().unwrap().upgrade().unwrap();
 808        let foreground = self.foreground.clone();
 809        self.foreground_platform.prompt_for_new_path(
 810            directory,
 811            Box::new(move |path| {
 812                foreground
 813                    .spawn(async move { (done_fn)(path, &mut *app.borrow_mut()) })
 814                    .detach();
 815            }),
 816        );
 817    }
 818
 819    pub(crate) fn notify_view(&mut self, window_id: usize, view_id: usize) {
 820        self.pending_effects
 821            .push_back(Effect::ViewNotification { window_id, view_id });
 822    }
 823
 824    pub fn dispatch_action<T: 'static + Any>(
 825        &mut self,
 826        window_id: usize,
 827        responder_chain: Vec<usize>,
 828        name: &str,
 829        arg: T,
 830    ) {
 831        self.dispatch_action_any(window_id, &responder_chain, name, Box::new(arg).as_ref());
 832    }
 833
 834    pub(crate) fn dispatch_action_any(
 835        &mut self,
 836        window_id: usize,
 837        path: &[usize],
 838        name: &str,
 839        arg: &dyn Any,
 840    ) -> bool {
 841        self.pending_flushes += 1;
 842        let mut halted_dispatch = false;
 843
 844        for view_id in path.iter().rev() {
 845            if let Some(mut view) = self.cx.views.remove(&(window_id, *view_id)) {
 846                let type_id = view.as_any().type_id();
 847
 848                if let Some((name, mut handlers)) = self
 849                    .actions
 850                    .get_mut(&type_id)
 851                    .and_then(|h| h.remove_entry(name))
 852                {
 853                    for handler in handlers.iter_mut().rev() {
 854                        let halt_dispatch = handler(view.as_mut(), arg, self, window_id, *view_id);
 855                        if halt_dispatch {
 856                            halted_dispatch = true;
 857                            break;
 858                        }
 859                    }
 860                    self.actions
 861                        .get_mut(&type_id)
 862                        .unwrap()
 863                        .insert(name, handlers);
 864                }
 865
 866                self.cx.views.insert((window_id, *view_id), view);
 867
 868                if halted_dispatch {
 869                    break;
 870                }
 871            }
 872        }
 873
 874        if !halted_dispatch {
 875            self.dispatch_global_action_any(name, arg);
 876        }
 877
 878        self.flush_effects();
 879        halted_dispatch
 880    }
 881
 882    pub fn dispatch_global_action<T: 'static + Any>(&mut self, name: &str, arg: T) {
 883        self.dispatch_global_action_any(name, Box::new(arg).as_ref());
 884    }
 885
 886    fn dispatch_global_action_any(&mut self, name: &str, arg: &dyn Any) {
 887        if let Some((name, mut handlers)) = self.global_actions.remove_entry(name) {
 888            self.pending_flushes += 1;
 889            for handler in handlers.iter_mut().rev() {
 890                handler(arg, self);
 891            }
 892            self.global_actions.insert(name, handlers);
 893            self.flush_effects();
 894        }
 895    }
 896
 897    pub fn add_bindings<T: IntoIterator<Item = keymap::Binding>>(&mut self, bindings: T) {
 898        self.keystroke_matcher.add_bindings(bindings);
 899    }
 900
 901    pub fn dispatch_keystroke(
 902        &mut self,
 903        window_id: usize,
 904        responder_chain: Vec<usize>,
 905        keystroke: &Keystroke,
 906    ) -> Result<bool> {
 907        let mut context_chain = Vec::new();
 908        let mut context = keymap::Context::default();
 909        for view_id in &responder_chain {
 910            if let Some(view) = self.cx.views.get(&(window_id, *view_id)) {
 911                context.extend(view.keymap_context(self.as_ref()));
 912                context_chain.push(context.clone());
 913            } else {
 914                return Err(anyhow!(
 915                    "View {} in responder chain does not exist",
 916                    view_id
 917                ));
 918            }
 919        }
 920
 921        let mut pending = false;
 922        for (i, cx) in context_chain.iter().enumerate().rev() {
 923            match self
 924                .keystroke_matcher
 925                .push_keystroke(keystroke.clone(), responder_chain[i], cx)
 926            {
 927                MatchResult::None => {}
 928                MatchResult::Pending => pending = true,
 929                MatchResult::Action { name, arg } => {
 930                    if self.dispatch_action_any(
 931                        window_id,
 932                        &responder_chain[0..=i],
 933                        &name,
 934                        arg.as_ref().map(|arg| arg.as_ref()).unwrap_or(&()),
 935                    ) {
 936                        return Ok(true);
 937                    }
 938                }
 939            }
 940        }
 941
 942        Ok(pending)
 943    }
 944
 945    pub fn add_model<T, F>(&mut self, build_model: F) -> ModelHandle<T>
 946    where
 947        T: Entity,
 948        F: FnOnce(&mut ModelContext<T>) -> T,
 949    {
 950        self.pending_flushes += 1;
 951        let model_id = post_inc(&mut self.next_entity_id);
 952        let handle = ModelHandle::new(model_id, &self.cx.ref_counts);
 953        let mut cx = ModelContext::new(self, model_id);
 954        let model = build_model(&mut cx);
 955        self.cx.models.insert(model_id, Box::new(model));
 956        self.flush_effects();
 957        handle
 958    }
 959
 960    pub fn add_window<T, F>(&mut self, build_root_view: F) -> (usize, ViewHandle<T>)
 961    where
 962        T: View,
 963        F: FnOnce(&mut ViewContext<T>) -> T,
 964    {
 965        self.pending_flushes += 1;
 966        let window_id = post_inc(&mut self.next_window_id);
 967        let root_view = self.add_view(window_id, build_root_view);
 968
 969        self.cx.windows.insert(
 970            window_id,
 971            Window {
 972                root_view: root_view.clone().into(),
 973                focused_view_id: root_view.id(),
 974                invalidation: None,
 975            },
 976        );
 977        self.open_platform_window(window_id);
 978        root_view.update(self, |view, cx| {
 979            view.on_focus(cx);
 980            cx.notify();
 981        });
 982        self.flush_effects();
 983
 984        (window_id, root_view)
 985    }
 986
 987    pub fn remove_window(&mut self, window_id: usize) {
 988        self.cx.windows.remove(&window_id);
 989        self.presenters_and_platform_windows.remove(&window_id);
 990        self.remove_dropped_entities();
 991    }
 992
 993    fn open_platform_window(&mut self, window_id: usize) {
 994        let mut window = self.cx.platform.open_window(
 995            window_id,
 996            WindowOptions {
 997                bounds: RectF::new(vec2f(0., 0.), vec2f(1024., 768.)),
 998                title: "Zed".into(),
 999            },
1000            self.foreground.clone(),
1001        );
1002        let text_layout_cache = TextLayoutCache::new(self.cx.platform.fonts());
1003        let presenter = Rc::new(RefCell::new(Presenter::new(
1004            window_id,
1005            self.cx.font_cache.clone(),
1006            text_layout_cache,
1007            self.assets.clone(),
1008            self,
1009        )));
1010
1011        {
1012            let mut app = self.upgrade();
1013            let presenter = presenter.clone();
1014            window.on_event(Box::new(move |event| {
1015                app.update(|cx| {
1016                    if let Event::KeyDown { keystroke, .. } = &event {
1017                        if cx
1018                            .dispatch_keystroke(
1019                                window_id,
1020                                presenter.borrow().dispatch_path(cx.as_ref()),
1021                                keystroke,
1022                            )
1023                            .unwrap()
1024                        {
1025                            return;
1026                        }
1027                    }
1028
1029                    presenter.borrow_mut().dispatch_event(event, cx);
1030                })
1031            }));
1032        }
1033
1034        {
1035            let mut app = self.upgrade();
1036            let presenter = presenter.clone();
1037            window.on_resize(Box::new(move |window| {
1038                app.update(|cx| {
1039                    let scene = presenter.borrow_mut().build_scene(
1040                        window.size(),
1041                        window.scale_factor(),
1042                        cx,
1043                    );
1044                    window.present_scene(scene);
1045                })
1046            }));
1047        }
1048
1049        {
1050            let mut app = self.upgrade();
1051            window.on_close(Box::new(move || {
1052                app.update(|cx| cx.remove_window(window_id));
1053            }));
1054        }
1055
1056        self.presenters_and_platform_windows
1057            .insert(window_id, (presenter.clone(), window));
1058
1059        self.on_debug_elements(window_id, move |cx| {
1060            presenter.borrow().debug_elements(cx).unwrap()
1061        });
1062    }
1063
1064    pub fn add_view<T, F>(&mut self, window_id: usize, build_view: F) -> ViewHandle<T>
1065    where
1066        T: View,
1067        F: FnOnce(&mut ViewContext<T>) -> T,
1068    {
1069        self.add_option_view(window_id, |cx| Some(build_view(cx)))
1070            .unwrap()
1071    }
1072
1073    pub fn add_option_view<T, F>(
1074        &mut self,
1075        window_id: usize,
1076        build_view: F,
1077    ) -> Option<ViewHandle<T>>
1078    where
1079        T: View,
1080        F: FnOnce(&mut ViewContext<T>) -> Option<T>,
1081    {
1082        let view_id = post_inc(&mut self.next_entity_id);
1083        self.pending_flushes += 1;
1084        let handle = ViewHandle::new(window_id, view_id, &self.cx.ref_counts);
1085        let mut cx = ViewContext::new(self, window_id, view_id);
1086        let handle = if let Some(view) = build_view(&mut cx) {
1087            self.cx.views.insert((window_id, view_id), Box::new(view));
1088            if let Some(window) = self.cx.windows.get_mut(&window_id) {
1089                window
1090                    .invalidation
1091                    .get_or_insert_with(Default::default)
1092                    .updated
1093                    .insert(view_id);
1094            }
1095            Some(handle)
1096        } else {
1097            None
1098        };
1099        self.flush_effects();
1100        handle
1101    }
1102
1103    fn remove_dropped_entities(&mut self) {
1104        loop {
1105            let (dropped_models, dropped_views, dropped_values) =
1106                self.cx.ref_counts.lock().take_dropped();
1107            if dropped_models.is_empty() && dropped_views.is_empty() && dropped_values.is_empty() {
1108                break;
1109            }
1110
1111            for model_id in dropped_models {
1112                self.subscriptions.remove(&model_id);
1113                self.model_observations.remove(&model_id);
1114                let mut model = self.cx.models.remove(&model_id).unwrap();
1115                model.release(self);
1116            }
1117
1118            for (window_id, view_id) in dropped_views {
1119                self.subscriptions.remove(&view_id);
1120                self.model_observations.remove(&view_id);
1121                let mut view = self.cx.views.remove(&(window_id, view_id)).unwrap();
1122                view.release(self);
1123                let change_focus_to = self.cx.windows.get_mut(&window_id).and_then(|window| {
1124                    window
1125                        .invalidation
1126                        .get_or_insert_with(Default::default)
1127                        .removed
1128                        .push(view_id);
1129                    if window.focused_view_id == view_id {
1130                        Some(window.root_view.id())
1131                    } else {
1132                        None
1133                    }
1134                });
1135
1136                if let Some(view_id) = change_focus_to {
1137                    self.focus(window_id, view_id);
1138                }
1139            }
1140
1141            let mut values = self.cx.values.write();
1142            for key in dropped_values {
1143                values.remove(&key);
1144            }
1145        }
1146    }
1147
1148    fn flush_effects(&mut self) {
1149        self.pending_flushes = self.pending_flushes.saturating_sub(1);
1150
1151        if !self.flushing_effects && self.pending_flushes == 0 {
1152            self.flushing_effects = true;
1153
1154            loop {
1155                if let Some(effect) = self.pending_effects.pop_front() {
1156                    match effect {
1157                        Effect::Event { entity_id, payload } => self.emit_event(entity_id, payload),
1158                        Effect::ModelNotification { model_id } => {
1159                            self.notify_model_observers(model_id)
1160                        }
1161                        Effect::ViewNotification { window_id, view_id } => {
1162                            self.notify_view_observers(window_id, view_id)
1163                        }
1164                        Effect::Focus { window_id, view_id } => {
1165                            self.focus(window_id, view_id);
1166                        }
1167                    }
1168                    self.remove_dropped_entities();
1169                } else {
1170                    self.remove_dropped_entities();
1171                    self.update_windows();
1172
1173                    if self.pending_effects.is_empty() {
1174                        self.flushing_effects = false;
1175                        break;
1176                    }
1177                }
1178            }
1179        }
1180    }
1181
1182    fn update_windows(&mut self) {
1183        let mut invalidations = HashMap::new();
1184        for (window_id, window) in &mut self.cx.windows {
1185            if let Some(invalidation) = window.invalidation.take() {
1186                invalidations.insert(*window_id, invalidation);
1187            }
1188        }
1189
1190        for (window_id, invalidation) in invalidations {
1191            if let Some((presenter, mut window)) =
1192                self.presenters_and_platform_windows.remove(&window_id)
1193            {
1194                {
1195                    let mut presenter = presenter.borrow_mut();
1196                    presenter.invalidate(invalidation, self.as_ref());
1197                    let scene = presenter.build_scene(window.size(), window.scale_factor(), self);
1198                    window.present_scene(scene);
1199                }
1200                self.presenters_and_platform_windows
1201                    .insert(window_id, (presenter, window));
1202            }
1203        }
1204    }
1205
1206    fn emit_event(&mut self, entity_id: usize, payload: Box<dyn Any>) {
1207        if let Some(subscriptions) = self.subscriptions.remove(&entity_id) {
1208            for mut subscription in subscriptions {
1209                let alive = match &mut subscription {
1210                    Subscription::FromModel { model_id, callback } => {
1211                        if let Some(mut model) = self.cx.models.remove(model_id) {
1212                            callback(model.as_any_mut(), payload.as_ref(), self, *model_id);
1213                            self.cx.models.insert(*model_id, model);
1214                            true
1215                        } else {
1216                            false
1217                        }
1218                    }
1219                    Subscription::FromView {
1220                        window_id,
1221                        view_id,
1222                        callback,
1223                    } => {
1224                        if let Some(mut view) = self.cx.views.remove(&(*window_id, *view_id)) {
1225                            callback(
1226                                view.as_any_mut(),
1227                                payload.as_ref(),
1228                                self,
1229                                *window_id,
1230                                *view_id,
1231                            );
1232                            self.cx.views.insert((*window_id, *view_id), view);
1233                            true
1234                        } else {
1235                            false
1236                        }
1237                    }
1238                };
1239
1240                if alive {
1241                    self.subscriptions
1242                        .entry(entity_id)
1243                        .or_default()
1244                        .push(subscription);
1245                }
1246            }
1247        }
1248    }
1249
1250    fn notify_model_observers(&mut self, observed_id: usize) {
1251        if let Some(observations) = self.model_observations.remove(&observed_id) {
1252            if self.cx.models.contains_key(&observed_id) {
1253                for mut observation in observations {
1254                    let alive = match &mut observation {
1255                        ModelObservation::FromModel { model_id, callback } => {
1256                            if let Some(mut model) = self.cx.models.remove(model_id) {
1257                                callback(model.as_any_mut(), observed_id, self, *model_id);
1258                                self.cx.models.insert(*model_id, model);
1259                                true
1260                            } else {
1261                                false
1262                            }
1263                        }
1264                        ModelObservation::FromView {
1265                            window_id,
1266                            view_id,
1267                            callback,
1268                        } => {
1269                            if let Some(mut view) = self.cx.views.remove(&(*window_id, *view_id)) {
1270                                callback(
1271                                    view.as_any_mut(),
1272                                    observed_id,
1273                                    self,
1274                                    *window_id,
1275                                    *view_id,
1276                                );
1277                                self.cx.views.insert((*window_id, *view_id), view);
1278                                true
1279                            } else {
1280                                false
1281                            }
1282                        }
1283                    };
1284
1285                    if alive {
1286                        self.model_observations
1287                            .entry(observed_id)
1288                            .or_default()
1289                            .push(observation);
1290                    }
1291                }
1292            }
1293        }
1294    }
1295
1296    fn notify_view_observers(&mut self, window_id: usize, view_id: usize) {
1297        if let Some(window) = self.cx.windows.get_mut(&window_id) {
1298            window
1299                .invalidation
1300                .get_or_insert_with(Default::default)
1301                .updated
1302                .insert(view_id);
1303        }
1304
1305        if let Some(observations) = self.view_observations.remove(&view_id) {
1306            if self.cx.views.contains_key(&(window_id, view_id)) {
1307                for mut observation in observations {
1308                    let alive = if let Some(mut view) = self
1309                        .cx
1310                        .views
1311                        .remove(&(observation.window_id, observation.view_id))
1312                    {
1313                        (observation.callback)(
1314                            view.as_any_mut(),
1315                            view_id,
1316                            window_id,
1317                            self,
1318                            observation.window_id,
1319                            observation.view_id,
1320                        );
1321                        self.cx
1322                            .views
1323                            .insert((observation.window_id, observation.view_id), view);
1324                        true
1325                    } else {
1326                        false
1327                    };
1328
1329                    if alive {
1330                        self.view_observations
1331                            .entry(view_id)
1332                            .or_default()
1333                            .push(observation);
1334                    }
1335                }
1336            }
1337        }
1338    }
1339
1340    fn focus(&mut self, window_id: usize, focused_id: usize) {
1341        if self
1342            .cx
1343            .windows
1344            .get(&window_id)
1345            .map(|w| w.focused_view_id)
1346            .map_or(false, |cur_focused| cur_focused == focused_id)
1347        {
1348            return;
1349        }
1350
1351        self.pending_flushes += 1;
1352
1353        let blurred_id = self.cx.windows.get_mut(&window_id).map(|window| {
1354            let blurred_id = window.focused_view_id;
1355            window.focused_view_id = focused_id;
1356            blurred_id
1357        });
1358
1359        if let Some(blurred_id) = blurred_id {
1360            if let Some(mut blurred_view) = self.cx.views.remove(&(window_id, blurred_id)) {
1361                blurred_view.on_blur(self, window_id, blurred_id);
1362                self.cx.views.insert((window_id, blurred_id), blurred_view);
1363            }
1364        }
1365
1366        if let Some(mut focused_view) = self.cx.views.remove(&(window_id, focused_id)) {
1367            focused_view.on_focus(self, window_id, focused_id);
1368            self.cx.views.insert((window_id, focused_id), focused_view);
1369        }
1370
1371        self.flush_effects();
1372    }
1373
1374    pub fn spawn<F, Fut, T>(&self, f: F) -> Task<T>
1375    where
1376        F: FnOnce(AsyncAppContext) -> Fut,
1377        Fut: 'static + Future<Output = T>,
1378        T: 'static,
1379    {
1380        let cx = self.to_async();
1381        self.foreground.spawn(f(cx))
1382    }
1383
1384    pub fn to_async(&self) -> AsyncAppContext {
1385        AsyncAppContext(self.weak_self.as_ref().unwrap().upgrade().unwrap())
1386    }
1387
1388    pub fn write_to_clipboard(&self, item: ClipboardItem) {
1389        self.cx.platform.write_to_clipboard(item);
1390    }
1391
1392    pub fn read_from_clipboard(&self) -> Option<ClipboardItem> {
1393        self.cx.platform.read_from_clipboard()
1394    }
1395}
1396
1397impl ReadModel for MutableAppContext {
1398    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
1399        if let Some(model) = self.cx.models.get(&handle.model_id) {
1400            model
1401                .as_any()
1402                .downcast_ref()
1403                .expect("downcast is type safe")
1404        } else {
1405            panic!("circular model reference");
1406        }
1407    }
1408}
1409
1410impl UpdateModel for MutableAppContext {
1411    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
1412    where
1413        T: Entity,
1414        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
1415    {
1416        if let Some(mut model) = self.cx.models.remove(&handle.model_id) {
1417            self.pending_flushes += 1;
1418            let mut cx = ModelContext::new(self, handle.model_id);
1419            let result = update(
1420                model
1421                    .as_any_mut()
1422                    .downcast_mut()
1423                    .expect("downcast is type safe"),
1424                &mut cx,
1425            );
1426            self.cx.models.insert(handle.model_id, model);
1427            self.flush_effects();
1428            result
1429        } else {
1430            panic!("circular model update");
1431        }
1432    }
1433}
1434
1435impl ReadView for MutableAppContext {
1436    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T {
1437        if let Some(view) = self.cx.views.get(&(handle.window_id, handle.view_id)) {
1438            view.as_any().downcast_ref().expect("downcast is type safe")
1439        } else {
1440            panic!("circular view reference");
1441        }
1442    }
1443}
1444
1445impl UpdateView for MutableAppContext {
1446    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
1447    where
1448        T: View,
1449        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
1450    {
1451        self.pending_flushes += 1;
1452        let mut view = self
1453            .cx
1454            .views
1455            .remove(&(handle.window_id, handle.view_id))
1456            .expect("circular view update");
1457
1458        let mut cx = ViewContext::new(self, handle.window_id, handle.view_id);
1459        let result = update(
1460            view.as_any_mut()
1461                .downcast_mut()
1462                .expect("downcast is type safe"),
1463            &mut cx,
1464        );
1465        self.cx
1466            .views
1467            .insert((handle.window_id, handle.view_id), view);
1468        self.flush_effects();
1469        result
1470    }
1471}
1472
1473impl AsRef<AppContext> for MutableAppContext {
1474    fn as_ref(&self) -> &AppContext {
1475        &self.cx
1476    }
1477}
1478
1479pub struct AppContext {
1480    models: HashMap<usize, Box<dyn AnyModel>>,
1481    views: HashMap<(usize, usize), Box<dyn AnyView>>,
1482    windows: HashMap<usize, Window>,
1483    values: RwLock<HashMap<(TypeId, usize), Box<dyn Any>>>,
1484    background: Arc<executor::Background>,
1485    ref_counts: Arc<Mutex<RefCounts>>,
1486    font_cache: Arc<FontCache>,
1487    platform: Arc<dyn Platform>,
1488}
1489
1490impl AppContext {
1491    pub fn root_view_id(&self, window_id: usize) -> Option<usize> {
1492        self.windows
1493            .get(&window_id)
1494            .map(|window| window.root_view.id())
1495    }
1496
1497    pub fn focused_view_id(&self, window_id: usize) -> Option<usize> {
1498        self.windows
1499            .get(&window_id)
1500            .map(|window| window.focused_view_id)
1501    }
1502
1503    pub fn render_view(&self, window_id: usize, view_id: usize) -> Result<ElementBox> {
1504        self.views
1505            .get(&(window_id, view_id))
1506            .map(|v| v.render(self))
1507            .ok_or(anyhow!("view not found"))
1508    }
1509
1510    pub fn render_views(&self, window_id: usize) -> HashMap<usize, ElementBox> {
1511        self.views
1512            .iter()
1513            .filter_map(|((win_id, view_id), view)| {
1514                if *win_id == window_id {
1515                    Some((*view_id, view.render(self)))
1516                } else {
1517                    None
1518                }
1519            })
1520            .collect::<HashMap<_, ElementBox>>()
1521    }
1522
1523    pub fn background(&self) -> &Arc<executor::Background> {
1524        &self.background
1525    }
1526
1527    pub fn font_cache(&self) -> &Arc<FontCache> {
1528        &self.font_cache
1529    }
1530
1531    pub fn platform(&self) -> &Arc<dyn Platform> {
1532        &self.platform
1533    }
1534
1535    pub fn value<Tag: 'static, T: 'static + Default>(&self, id: usize) -> ValueHandle<T> {
1536        let key = (TypeId::of::<Tag>(), id);
1537        let mut values = self.values.write();
1538        values.entry(key).or_insert_with(|| Box::new(T::default()));
1539        ValueHandle::new(TypeId::of::<Tag>(), id, &self.ref_counts)
1540    }
1541}
1542
1543impl ReadModel for AppContext {
1544    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
1545        if let Some(model) = self.models.get(&handle.model_id) {
1546            model
1547                .as_any()
1548                .downcast_ref()
1549                .expect("downcast should be type safe")
1550        } else {
1551            panic!("circular model reference");
1552        }
1553    }
1554}
1555
1556impl ReadView for AppContext {
1557    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T {
1558        if let Some(view) = self.views.get(&(handle.window_id, handle.view_id)) {
1559            view.as_any()
1560                .downcast_ref()
1561                .expect("downcast should be type safe")
1562        } else {
1563            panic!("circular view reference");
1564        }
1565    }
1566}
1567
1568struct Window {
1569    root_view: AnyViewHandle,
1570    focused_view_id: usize,
1571    invalidation: Option<WindowInvalidation>,
1572}
1573
1574#[derive(Default, Clone)]
1575pub struct WindowInvalidation {
1576    pub updated: HashSet<usize>,
1577    pub removed: Vec<usize>,
1578}
1579
1580pub enum Effect {
1581    Event {
1582        entity_id: usize,
1583        payload: Box<dyn Any>,
1584    },
1585    ModelNotification {
1586        model_id: usize,
1587    },
1588    ViewNotification {
1589        window_id: usize,
1590        view_id: usize,
1591    },
1592    Focus {
1593        window_id: usize,
1594        view_id: usize,
1595    },
1596}
1597
1598impl Debug for Effect {
1599    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1600        match self {
1601            Effect::Event { entity_id, .. } => f
1602                .debug_struct("Effect::Event")
1603                .field("entity_id", entity_id)
1604                .finish(),
1605            Effect::ModelNotification { model_id } => f
1606                .debug_struct("Effect::ModelNotification")
1607                .field("model_id", model_id)
1608                .finish(),
1609            Effect::ViewNotification { window_id, view_id } => f
1610                .debug_struct("Effect::ViewNotification")
1611                .field("window_id", window_id)
1612                .field("view_id", view_id)
1613                .finish(),
1614            Effect::Focus { window_id, view_id } => f
1615                .debug_struct("Effect::Focus")
1616                .field("window_id", window_id)
1617                .field("view_id", view_id)
1618                .finish(),
1619        }
1620    }
1621}
1622
1623pub trait AnyModel: Send + Sync {
1624    fn as_any(&self) -> &dyn Any;
1625    fn as_any_mut(&mut self) -> &mut dyn Any;
1626    fn release(&mut self, cx: &mut MutableAppContext);
1627}
1628
1629impl<T> AnyModel for T
1630where
1631    T: Entity,
1632{
1633    fn as_any(&self) -> &dyn Any {
1634        self
1635    }
1636
1637    fn as_any_mut(&mut self) -> &mut dyn Any {
1638        self
1639    }
1640
1641    fn release(&mut self, cx: &mut MutableAppContext) {
1642        self.release(cx);
1643    }
1644}
1645
1646pub trait AnyView: Send + Sync {
1647    fn as_any(&self) -> &dyn Any;
1648    fn as_any_mut(&mut self) -> &mut dyn Any;
1649    fn release(&mut self, cx: &mut MutableAppContext);
1650    fn ui_name(&self) -> &'static str;
1651    fn render<'a>(&self, cx: &AppContext) -> ElementBox;
1652    fn on_focus(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize);
1653    fn on_blur(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize);
1654    fn keymap_context(&self, cx: &AppContext) -> keymap::Context;
1655}
1656
1657impl<T> AnyView for T
1658where
1659    T: View,
1660{
1661    fn as_any(&self) -> &dyn Any {
1662        self
1663    }
1664
1665    fn as_any_mut(&mut self) -> &mut dyn Any {
1666        self
1667    }
1668
1669    fn release(&mut self, cx: &mut MutableAppContext) {
1670        self.release(cx);
1671    }
1672
1673    fn ui_name(&self) -> &'static str {
1674        T::ui_name()
1675    }
1676
1677    fn render<'a>(&self, cx: &AppContext) -> ElementBox {
1678        View::render(self, cx)
1679    }
1680
1681    fn on_focus(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize) {
1682        let mut cx = ViewContext::new(cx, window_id, view_id);
1683        View::on_focus(self, &mut cx);
1684    }
1685
1686    fn on_blur(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize) {
1687        let mut cx = ViewContext::new(cx, window_id, view_id);
1688        View::on_blur(self, &mut cx);
1689    }
1690
1691    fn keymap_context(&self, cx: &AppContext) -> keymap::Context {
1692        View::keymap_context(self, cx)
1693    }
1694}
1695
1696pub struct ModelContext<'a, T: ?Sized> {
1697    app: &'a mut MutableAppContext,
1698    model_id: usize,
1699    model_type: PhantomData<T>,
1700    halt_stream: bool,
1701}
1702
1703impl<'a, T: Entity> ModelContext<'a, T> {
1704    fn new(app: &'a mut MutableAppContext, model_id: usize) -> Self {
1705        Self {
1706            app,
1707            model_id,
1708            model_type: PhantomData,
1709            halt_stream: false,
1710        }
1711    }
1712
1713    pub fn background(&self) -> &Arc<executor::Background> {
1714        &self.app.cx.background
1715    }
1716
1717    pub fn halt_stream(&mut self) {
1718        self.halt_stream = true;
1719    }
1720
1721    pub fn model_id(&self) -> usize {
1722        self.model_id
1723    }
1724
1725    pub fn add_model<S, F>(&mut self, build_model: F) -> ModelHandle<S>
1726    where
1727        S: Entity,
1728        F: FnOnce(&mut ModelContext<S>) -> S,
1729    {
1730        self.app.add_model(build_model)
1731    }
1732
1733    pub fn subscribe<S: Entity, F>(&mut self, handle: &ModelHandle<S>, mut callback: F)
1734    where
1735        S::Event: 'static,
1736        F: 'static + FnMut(&mut T, &S::Event, &mut ModelContext<T>),
1737    {
1738        self.app
1739            .subscriptions
1740            .entry(handle.model_id)
1741            .or_default()
1742            .push(Subscription::FromModel {
1743                model_id: self.model_id,
1744                callback: Box::new(move |model, payload, app, model_id| {
1745                    let model = model.downcast_mut().expect("downcast is type safe");
1746                    let payload = payload.downcast_ref().expect("downcast is type safe");
1747                    let mut cx = ModelContext::new(app, model_id);
1748                    callback(model, payload, &mut cx);
1749                }),
1750            });
1751    }
1752
1753    pub fn emit(&mut self, payload: T::Event) {
1754        self.app.pending_effects.push_back(Effect::Event {
1755            entity_id: self.model_id,
1756            payload: Box::new(payload),
1757        });
1758    }
1759
1760    pub fn observe<S, F>(&mut self, handle: &ModelHandle<S>, mut callback: F)
1761    where
1762        S: Entity,
1763        F: 'static + FnMut(&mut T, ModelHandle<S>, &mut ModelContext<T>),
1764    {
1765        self.app
1766            .model_observations
1767            .entry(handle.model_id)
1768            .or_default()
1769            .push(ModelObservation::FromModel {
1770                model_id: self.model_id,
1771                callback: Box::new(move |model, observed_id, app, model_id| {
1772                    let model = model.downcast_mut().expect("downcast is type safe");
1773                    let observed = ModelHandle::new(observed_id, &app.cx.ref_counts);
1774                    let mut cx = ModelContext::new(app, model_id);
1775                    callback(model, observed, &mut cx);
1776                }),
1777            });
1778    }
1779
1780    pub fn notify(&mut self) {
1781        self.app
1782            .pending_effects
1783            .push_back(Effect::ModelNotification {
1784                model_id: self.model_id,
1785            });
1786    }
1787
1788    pub fn handle(&self) -> ModelHandle<T> {
1789        ModelHandle::new(self.model_id, &self.app.cx.ref_counts)
1790    }
1791
1792    pub fn spawn<F, Fut, S>(&self, f: F) -> Task<S>
1793    where
1794        F: FnOnce(ModelHandle<T>, AsyncAppContext) -> Fut,
1795        Fut: 'static + Future<Output = S>,
1796        S: 'static,
1797    {
1798        let handle = self.handle();
1799        self.app.spawn(|cx| f(handle, cx))
1800    }
1801
1802    pub fn spawn_weak<F, Fut, S>(&self, f: F) -> Task<S>
1803    where
1804        F: FnOnce(WeakModelHandle<T>, AsyncAppContext) -> Fut,
1805        Fut: 'static + Future<Output = S>,
1806        S: 'static,
1807    {
1808        let handle = self.handle().downgrade();
1809        self.app.spawn(|cx| f(handle, cx))
1810    }
1811}
1812
1813impl<M> AsRef<AppContext> for ModelContext<'_, M> {
1814    fn as_ref(&self) -> &AppContext {
1815        &self.app.cx
1816    }
1817}
1818
1819impl<M> AsMut<MutableAppContext> for ModelContext<'_, M> {
1820    fn as_mut(&mut self) -> &mut MutableAppContext {
1821        self.app
1822    }
1823}
1824
1825impl<M> ReadModel for ModelContext<'_, M> {
1826    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
1827        self.app.read_model(handle)
1828    }
1829}
1830
1831impl<M> UpdateModel for ModelContext<'_, M> {
1832    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
1833    where
1834        T: Entity,
1835        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
1836    {
1837        self.app.update_model(handle, update)
1838    }
1839}
1840
1841pub struct ViewContext<'a, T: ?Sized> {
1842    app: &'a mut MutableAppContext,
1843    window_id: usize,
1844    view_id: usize,
1845    view_type: PhantomData<T>,
1846    halt_action_dispatch: bool,
1847}
1848
1849impl<'a, T: View> ViewContext<'a, T> {
1850    fn new(app: &'a mut MutableAppContext, window_id: usize, view_id: usize) -> Self {
1851        Self {
1852            app,
1853            window_id,
1854            view_id,
1855            view_type: PhantomData,
1856            halt_action_dispatch: true,
1857        }
1858    }
1859
1860    pub fn handle(&self) -> ViewHandle<T> {
1861        ViewHandle::new(self.window_id, self.view_id, &self.app.cx.ref_counts)
1862    }
1863
1864    pub fn window_id(&self) -> usize {
1865        self.window_id
1866    }
1867
1868    pub fn view_id(&self) -> usize {
1869        self.view_id
1870    }
1871
1872    pub fn foreground(&self) -> &Rc<executor::Foreground> {
1873        self.app.foreground()
1874    }
1875
1876    pub fn background_executor(&self) -> &Arc<executor::Background> {
1877        &self.app.cx.background
1878    }
1879
1880    pub fn platform(&self) -> Arc<dyn Platform> {
1881        self.app.platform()
1882    }
1883
1884    pub fn prompt<F>(&self, level: PromptLevel, msg: &str, answers: &[&str], done_fn: F)
1885    where
1886        F: 'static + FnOnce(usize, &mut MutableAppContext),
1887    {
1888        self.app
1889            .prompt(self.window_id, level, msg, answers, done_fn)
1890    }
1891
1892    pub fn prompt_for_paths<F>(&self, options: PathPromptOptions, done_fn: F)
1893    where
1894        F: 'static + FnOnce(Option<Vec<PathBuf>>, &mut MutableAppContext),
1895    {
1896        self.app.prompt_for_paths(options, done_fn)
1897    }
1898
1899    pub fn prompt_for_new_path<F>(&self, directory: &Path, done_fn: F)
1900    where
1901        F: 'static + FnOnce(Option<PathBuf>, &mut MutableAppContext),
1902    {
1903        self.app.prompt_for_new_path(directory, done_fn)
1904    }
1905
1906    pub fn debug_elements(&self) -> crate::json::Value {
1907        self.app.debug_elements(self.window_id).unwrap()
1908    }
1909
1910    pub fn focus<S>(&mut self, handle: S)
1911    where
1912        S: Into<AnyViewHandle>,
1913    {
1914        let handle = handle.into();
1915        self.app.pending_effects.push_back(Effect::Focus {
1916            window_id: handle.window_id,
1917            view_id: handle.view_id,
1918        });
1919    }
1920
1921    pub fn focus_self(&mut self) {
1922        self.app.pending_effects.push_back(Effect::Focus {
1923            window_id: self.window_id,
1924            view_id: self.view_id,
1925        });
1926    }
1927
1928    pub fn add_model<S, F>(&mut self, build_model: F) -> ModelHandle<S>
1929    where
1930        S: Entity,
1931        F: FnOnce(&mut ModelContext<S>) -> S,
1932    {
1933        self.app.add_model(build_model)
1934    }
1935
1936    pub fn add_view<S, F>(&mut self, build_view: F) -> ViewHandle<S>
1937    where
1938        S: View,
1939        F: FnOnce(&mut ViewContext<S>) -> S,
1940    {
1941        self.app.add_view(self.window_id, build_view)
1942    }
1943
1944    pub fn add_option_view<S, F>(&mut self, build_view: F) -> Option<ViewHandle<S>>
1945    where
1946        S: View,
1947        F: FnOnce(&mut ViewContext<S>) -> Option<S>,
1948    {
1949        self.app.add_option_view(self.window_id, build_view)
1950    }
1951
1952    pub fn subscribe_to_model<E, F>(&mut self, handle: &ModelHandle<E>, mut callback: F)
1953    where
1954        E: Entity,
1955        E::Event: 'static,
1956        F: 'static + FnMut(&mut T, ModelHandle<E>, &E::Event, &mut ViewContext<T>),
1957    {
1958        let emitter_handle = handle.downgrade();
1959        self.subscribe(handle, move |model, payload, cx| {
1960            if let Some(emitter_handle) = emitter_handle.upgrade(cx.as_ref()) {
1961                callback(model, emitter_handle, payload, cx);
1962            }
1963        });
1964    }
1965
1966    pub fn subscribe_to_view<V, F>(&mut self, handle: &ViewHandle<V>, mut callback: F)
1967    where
1968        V: View,
1969        V::Event: 'static,
1970        F: 'static + FnMut(&mut T, ViewHandle<V>, &V::Event, &mut ViewContext<T>),
1971    {
1972        let emitter_handle = handle.downgrade();
1973        self.subscribe(handle, move |view, payload, cx| {
1974            if let Some(emitter_handle) = emitter_handle.upgrade(cx.as_ref()) {
1975                callback(view, emitter_handle, payload, cx);
1976            }
1977        });
1978    }
1979
1980    pub fn subscribe<E, F>(&mut self, handle: &impl Handle<E>, mut callback: F)
1981    where
1982        E: Entity,
1983        E::Event: 'static,
1984        F: 'static + FnMut(&mut T, &E::Event, &mut ViewContext<T>),
1985    {
1986        self.app
1987            .subscriptions
1988            .entry(handle.id())
1989            .or_default()
1990            .push(Subscription::FromView {
1991                window_id: self.window_id,
1992                view_id: self.view_id,
1993                callback: Box::new(move |entity, payload, app, window_id, view_id| {
1994                    let entity = entity.downcast_mut().expect("downcast is type safe");
1995                    let payload = payload.downcast_ref().expect("downcast is type safe");
1996                    let mut cx = ViewContext::new(app, window_id, view_id);
1997                    callback(entity, payload, &mut cx);
1998                }),
1999            });
2000    }
2001
2002    pub fn emit(&mut self, payload: T::Event) {
2003        self.app.pending_effects.push_back(Effect::Event {
2004            entity_id: self.view_id,
2005            payload: Box::new(payload),
2006        });
2007    }
2008
2009    pub fn observe_model<S, F>(&mut self, handle: &ModelHandle<S>, mut callback: F)
2010    where
2011        S: Entity,
2012        F: 'static + FnMut(&mut T, ModelHandle<S>, &mut ViewContext<T>),
2013    {
2014        self.app
2015            .model_observations
2016            .entry(handle.id())
2017            .or_default()
2018            .push(ModelObservation::FromView {
2019                window_id: self.window_id,
2020                view_id: self.view_id,
2021                callback: Box::new(move |view, observed_id, app, window_id, view_id| {
2022                    let view = view.downcast_mut().expect("downcast is type safe");
2023                    let observed = ModelHandle::new(observed_id, &app.cx.ref_counts);
2024                    let mut cx = ViewContext::new(app, window_id, view_id);
2025                    callback(view, observed, &mut cx);
2026                }),
2027            });
2028    }
2029
2030    pub fn observe_view<S, F>(&mut self, handle: &ViewHandle<S>, mut callback: F)
2031    where
2032        S: View,
2033        F: 'static + FnMut(&mut T, ViewHandle<S>, &mut ViewContext<T>),
2034    {
2035        self.app
2036            .view_observations
2037            .entry(handle.id())
2038            .or_default()
2039            .push(ViewObservation {
2040                window_id: self.window_id,
2041                view_id: self.view_id,
2042                callback: Box::new(
2043                    move |view,
2044                          observed_view_id,
2045                          observed_window_id,
2046                          app,
2047                          observing_window_id,
2048                          observing_view_id| {
2049                        let view = view.downcast_mut().expect("downcast is type safe");
2050                        let observed_handle = ViewHandle::new(
2051                            observed_view_id,
2052                            observed_window_id,
2053                            &app.cx.ref_counts,
2054                        );
2055                        let mut cx = ViewContext::new(app, observing_window_id, observing_view_id);
2056                        callback(view, observed_handle, &mut cx);
2057                    },
2058                ),
2059            });
2060    }
2061
2062    pub fn notify(&mut self) {
2063        self.app.notify_view(self.window_id, self.view_id);
2064    }
2065
2066    pub fn propagate_action(&mut self) {
2067        self.halt_action_dispatch = false;
2068    }
2069
2070    pub fn spawn<F, Fut, S>(&self, f: F) -> Task<S>
2071    where
2072        F: FnOnce(ViewHandle<T>, AsyncAppContext) -> Fut,
2073        Fut: 'static + Future<Output = S>,
2074        S: 'static,
2075    {
2076        let handle = self.handle();
2077        self.app.spawn(|cx| f(handle, cx))
2078    }
2079}
2080
2081impl AsRef<AppContext> for &AppContext {
2082    fn as_ref(&self) -> &AppContext {
2083        self
2084    }
2085}
2086
2087impl<M> AsRef<AppContext> for ViewContext<'_, M> {
2088    fn as_ref(&self) -> &AppContext {
2089        &self.app.cx
2090    }
2091}
2092
2093impl<M> AsMut<MutableAppContext> for ViewContext<'_, M> {
2094    fn as_mut(&mut self) -> &mut MutableAppContext {
2095        self.app
2096    }
2097}
2098
2099impl<V> ReadModel for ViewContext<'_, V> {
2100    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
2101        self.app.read_model(handle)
2102    }
2103}
2104
2105impl<V: View> UpdateModel for ViewContext<'_, V> {
2106    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
2107    where
2108        T: Entity,
2109        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
2110    {
2111        self.app.update_model(handle, update)
2112    }
2113}
2114
2115impl<V: View> ReadView for ViewContext<'_, V> {
2116    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T {
2117        self.app.read_view(handle)
2118    }
2119}
2120
2121impl<V: View> UpdateView for ViewContext<'_, V> {
2122    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
2123    where
2124        T: View,
2125        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
2126    {
2127        self.app.update_view(handle, update)
2128    }
2129}
2130
2131pub trait Handle<T> {
2132    fn id(&self) -> usize;
2133    fn location(&self) -> EntityLocation;
2134}
2135
2136#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
2137pub enum EntityLocation {
2138    Model(usize),
2139    View(usize, usize),
2140}
2141
2142pub struct ModelHandle<T> {
2143    model_id: usize,
2144    model_type: PhantomData<T>,
2145    ref_counts: Arc<Mutex<RefCounts>>,
2146}
2147
2148impl<T: Entity> ModelHandle<T> {
2149    fn new(model_id: usize, ref_counts: &Arc<Mutex<RefCounts>>) -> Self {
2150        ref_counts.lock().inc_model(model_id);
2151        Self {
2152            model_id,
2153            model_type: PhantomData,
2154            ref_counts: ref_counts.clone(),
2155        }
2156    }
2157
2158    pub fn downgrade(&self) -> WeakModelHandle<T> {
2159        WeakModelHandle::new(self.model_id)
2160    }
2161
2162    pub fn id(&self) -> usize {
2163        self.model_id
2164    }
2165
2166    pub fn read<'a, C: ReadModel>(&self, cx: &'a C) -> &'a T {
2167        cx.read_model(self)
2168    }
2169
2170    pub fn read_with<'a, C, F, S>(&self, cx: &C, read: F) -> S
2171    where
2172        C: ReadModelWith,
2173        F: FnOnce(&T, &AppContext) -> S,
2174    {
2175        cx.read_model_with(self, read)
2176    }
2177
2178    pub fn update<C, F, S>(&self, cx: &mut C, update: F) -> S
2179    where
2180        C: UpdateModel,
2181        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
2182    {
2183        cx.update_model(self, update)
2184    }
2185
2186    pub fn condition(
2187        &self,
2188        cx: &TestAppContext,
2189        mut predicate: impl FnMut(&T, &AppContext) -> bool,
2190    ) -> impl Future<Output = ()> {
2191        let (tx, mut rx) = mpsc::channel(1024);
2192
2193        let mut cx = cx.cx.borrow_mut();
2194        self.update(&mut *cx, |_, cx| {
2195            cx.observe(self, {
2196                let mut tx = tx.clone();
2197                move |_, _, _| {
2198                    tx.blocking_send(()).ok();
2199                }
2200            });
2201            cx.subscribe(self, {
2202                let mut tx = tx.clone();
2203                move |_, _, _| {
2204                    tx.blocking_send(()).ok();
2205                }
2206            })
2207        });
2208
2209        let cx = cx.weak_self.as_ref().unwrap().upgrade().unwrap();
2210        let handle = self.downgrade();
2211        let duration = if std::env::var("CI").is_ok() {
2212            Duration::from_secs(5)
2213        } else {
2214            Duration::from_secs(1)
2215        };
2216
2217        async move {
2218            timeout(duration, async move {
2219                loop {
2220                    {
2221                        let cx = cx.borrow();
2222                        let cx = cx.as_ref();
2223                        if predicate(
2224                            handle
2225                                .upgrade(cx)
2226                                .expect("model dropped with pending condition")
2227                                .read(cx),
2228                            cx,
2229                        ) {
2230                            break;
2231                        }
2232                    }
2233
2234                    rx.recv()
2235                        .await
2236                        .expect("model dropped with pending condition");
2237                }
2238            })
2239            .await
2240            .expect("condition timed out");
2241        }
2242    }
2243}
2244
2245impl<T> Clone for ModelHandle<T> {
2246    fn clone(&self) -> Self {
2247        self.ref_counts.lock().inc_model(self.model_id);
2248        Self {
2249            model_id: self.model_id,
2250            model_type: PhantomData,
2251            ref_counts: self.ref_counts.clone(),
2252        }
2253    }
2254}
2255
2256impl<T> PartialEq for ModelHandle<T> {
2257    fn eq(&self, other: &Self) -> bool {
2258        self.model_id == other.model_id
2259    }
2260}
2261
2262impl<T> Eq for ModelHandle<T> {}
2263
2264impl<T> Hash for ModelHandle<T> {
2265    fn hash<H: Hasher>(&self, state: &mut H) {
2266        self.model_id.hash(state);
2267    }
2268}
2269
2270impl<T> std::borrow::Borrow<usize> for ModelHandle<T> {
2271    fn borrow(&self) -> &usize {
2272        &self.model_id
2273    }
2274}
2275
2276impl<T> Debug for ModelHandle<T> {
2277    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2278        f.debug_tuple(&format!("ModelHandle<{}>", type_name::<T>()))
2279            .field(&self.model_id)
2280            .finish()
2281    }
2282}
2283
2284unsafe impl<T> Send for ModelHandle<T> {}
2285unsafe impl<T> Sync for ModelHandle<T> {}
2286
2287impl<T> Drop for ModelHandle<T> {
2288    fn drop(&mut self) {
2289        self.ref_counts.lock().dec_model(self.model_id);
2290    }
2291}
2292
2293impl<T> Handle<T> for ModelHandle<T> {
2294    fn id(&self) -> usize {
2295        self.model_id
2296    }
2297
2298    fn location(&self) -> EntityLocation {
2299        EntityLocation::Model(self.model_id)
2300    }
2301}
2302
2303pub struct WeakModelHandle<T> {
2304    model_id: usize,
2305    model_type: PhantomData<T>,
2306}
2307
2308impl<T: Entity> WeakModelHandle<T> {
2309    fn new(model_id: usize) -> Self {
2310        Self {
2311            model_id,
2312            model_type: PhantomData,
2313        }
2314    }
2315
2316    pub fn upgrade(&self, cx: impl AsRef<AppContext>) -> Option<ModelHandle<T>> {
2317        let cx = cx.as_ref();
2318        if cx.models.contains_key(&self.model_id) {
2319            Some(ModelHandle::new(self.model_id, &cx.ref_counts))
2320        } else {
2321            None
2322        }
2323    }
2324}
2325
2326impl<T> Hash for WeakModelHandle<T> {
2327    fn hash<H: Hasher>(&self, state: &mut H) {
2328        self.model_id.hash(state)
2329    }
2330}
2331
2332impl<T> PartialEq for WeakModelHandle<T> {
2333    fn eq(&self, other: &Self) -> bool {
2334        self.model_id == other.model_id
2335    }
2336}
2337
2338impl<T> Eq for WeakModelHandle<T> {}
2339
2340impl<T> Clone for WeakModelHandle<T> {
2341    fn clone(&self) -> Self {
2342        Self {
2343            model_id: self.model_id,
2344            model_type: PhantomData,
2345        }
2346    }
2347}
2348
2349pub struct ViewHandle<T> {
2350    window_id: usize,
2351    view_id: usize,
2352    view_type: PhantomData<T>,
2353    ref_counts: Arc<Mutex<RefCounts>>,
2354}
2355
2356impl<T: View> ViewHandle<T> {
2357    fn new(window_id: usize, view_id: usize, ref_counts: &Arc<Mutex<RefCounts>>) -> Self {
2358        ref_counts.lock().inc_view(window_id, view_id);
2359        Self {
2360            window_id,
2361            view_id,
2362            view_type: PhantomData,
2363            ref_counts: ref_counts.clone(),
2364        }
2365    }
2366
2367    pub fn downgrade(&self) -> WeakViewHandle<T> {
2368        WeakViewHandle::new(self.window_id, self.view_id)
2369    }
2370
2371    pub fn window_id(&self) -> usize {
2372        self.window_id
2373    }
2374
2375    pub fn id(&self) -> usize {
2376        self.view_id
2377    }
2378
2379    pub fn read<'a, C: ReadView>(&self, cx: &'a C) -> &'a T {
2380        cx.read_view(self)
2381    }
2382
2383    pub fn read_with<C, F, S>(&self, cx: &C, read: F) -> S
2384    where
2385        C: ReadViewWith,
2386        F: FnOnce(&T, &AppContext) -> S,
2387    {
2388        cx.read_view_with(self, read)
2389    }
2390
2391    pub fn update<C, F, S>(&self, cx: &mut C, update: F) -> S
2392    where
2393        C: UpdateView,
2394        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
2395    {
2396        cx.update_view(self, update)
2397    }
2398
2399    pub fn is_focused(&self, cx: &AppContext) -> bool {
2400        cx.focused_view_id(self.window_id)
2401            .map_or(false, |focused_id| focused_id == self.view_id)
2402    }
2403
2404    pub fn condition(
2405        &self,
2406        cx: &TestAppContext,
2407        mut predicate: impl FnMut(&T, &AppContext) -> bool,
2408    ) -> impl Future<Output = ()> {
2409        let (tx, mut rx) = mpsc::channel(1024);
2410
2411        let mut cx = cx.cx.borrow_mut();
2412        self.update(&mut *cx, |_, cx| {
2413            cx.observe_view(self, {
2414                let mut tx = tx.clone();
2415                move |_, _, _| {
2416                    tx.blocking_send(()).ok();
2417                }
2418            });
2419
2420            cx.subscribe(self, {
2421                let mut tx = tx.clone();
2422                move |_, _, _| {
2423                    tx.blocking_send(()).ok();
2424                }
2425            })
2426        });
2427
2428        let cx = cx.weak_self.as_ref().unwrap().upgrade().unwrap();
2429        let handle = self.downgrade();
2430        let duration = if std::env::var("CI").is_ok() {
2431            Duration::from_secs(2)
2432        } else {
2433            Duration::from_millis(500)
2434        };
2435
2436        async move {
2437            timeout(duration, async move {
2438                loop {
2439                    {
2440                        let cx = cx.borrow();
2441                        let cx = cx.as_ref();
2442                        if predicate(
2443                            handle
2444                                .upgrade(cx)
2445                                .expect("view dropped with pending condition")
2446                                .read(cx),
2447                            cx,
2448                        ) {
2449                            break;
2450                        }
2451                    }
2452
2453                    rx.recv()
2454                        .await
2455                        .expect("view dropped with pending condition");
2456                }
2457            })
2458            .await
2459            .expect("condition timed out");
2460        }
2461    }
2462}
2463
2464impl<T> Clone for ViewHandle<T> {
2465    fn clone(&self) -> Self {
2466        self.ref_counts
2467            .lock()
2468            .inc_view(self.window_id, self.view_id);
2469        Self {
2470            window_id: self.window_id,
2471            view_id: self.view_id,
2472            view_type: PhantomData,
2473            ref_counts: self.ref_counts.clone(),
2474        }
2475    }
2476}
2477
2478impl<T> PartialEq for ViewHandle<T> {
2479    fn eq(&self, other: &Self) -> bool {
2480        self.window_id == other.window_id && self.view_id == other.view_id
2481    }
2482}
2483
2484impl<T> Eq for ViewHandle<T> {}
2485
2486impl<T> Debug for ViewHandle<T> {
2487    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2488        f.debug_struct(&format!("ViewHandle<{}>", type_name::<T>()))
2489            .field("window_id", &self.window_id)
2490            .field("view_id", &self.view_id)
2491            .finish()
2492    }
2493}
2494
2495impl<T> Drop for ViewHandle<T> {
2496    fn drop(&mut self) {
2497        self.ref_counts
2498            .lock()
2499            .dec_view(self.window_id, self.view_id);
2500    }
2501}
2502
2503impl<T> Handle<T> for ViewHandle<T> {
2504    fn id(&self) -> usize {
2505        self.view_id
2506    }
2507
2508    fn location(&self) -> EntityLocation {
2509        EntityLocation::View(self.window_id, self.view_id)
2510    }
2511}
2512
2513pub struct AnyViewHandle {
2514    window_id: usize,
2515    view_id: usize,
2516    view_type: TypeId,
2517    ref_counts: Arc<Mutex<RefCounts>>,
2518}
2519
2520impl AnyViewHandle {
2521    pub fn id(&self) -> usize {
2522        self.view_id
2523    }
2524
2525    pub fn is<T: 'static>(&self) -> bool {
2526        TypeId::of::<T>() == self.view_type
2527    }
2528
2529    pub fn downcast<T: View>(self) -> Option<ViewHandle<T>> {
2530        if self.is::<T>() {
2531            let result = Some(ViewHandle {
2532                window_id: self.window_id,
2533                view_id: self.view_id,
2534                ref_counts: self.ref_counts.clone(),
2535                view_type: PhantomData,
2536            });
2537            unsafe {
2538                Arc::decrement_strong_count(&self.ref_counts);
2539            }
2540            std::mem::forget(self);
2541            result
2542        } else {
2543            None
2544        }
2545    }
2546}
2547
2548impl Clone for AnyViewHandle {
2549    fn clone(&self) -> Self {
2550        self.ref_counts
2551            .lock()
2552            .inc_view(self.window_id, self.view_id);
2553        Self {
2554            window_id: self.window_id,
2555            view_id: self.view_id,
2556            view_type: self.view_type,
2557            ref_counts: self.ref_counts.clone(),
2558        }
2559    }
2560}
2561
2562impl<T: View> From<&ViewHandle<T>> for AnyViewHandle {
2563    fn from(handle: &ViewHandle<T>) -> Self {
2564        handle
2565            .ref_counts
2566            .lock()
2567            .inc_view(handle.window_id, handle.view_id);
2568        AnyViewHandle {
2569            window_id: handle.window_id,
2570            view_id: handle.view_id,
2571            view_type: TypeId::of::<T>(),
2572            ref_counts: handle.ref_counts.clone(),
2573        }
2574    }
2575}
2576
2577impl<T: View> From<ViewHandle<T>> for AnyViewHandle {
2578    fn from(handle: ViewHandle<T>) -> Self {
2579        let any_handle = AnyViewHandle {
2580            window_id: handle.window_id,
2581            view_id: handle.view_id,
2582            view_type: TypeId::of::<T>(),
2583            ref_counts: handle.ref_counts.clone(),
2584        };
2585        unsafe {
2586            Arc::decrement_strong_count(&handle.ref_counts);
2587        }
2588        std::mem::forget(handle);
2589        any_handle
2590    }
2591}
2592
2593impl Drop for AnyViewHandle {
2594    fn drop(&mut self) {
2595        self.ref_counts
2596            .lock()
2597            .dec_view(self.window_id, self.view_id);
2598    }
2599}
2600
2601pub struct AnyModelHandle {
2602    model_id: usize,
2603    ref_counts: Arc<Mutex<RefCounts>>,
2604}
2605
2606impl<T: Entity> From<ModelHandle<T>> for AnyModelHandle {
2607    fn from(handle: ModelHandle<T>) -> Self {
2608        handle.ref_counts.lock().inc_model(handle.model_id);
2609        Self {
2610            model_id: handle.model_id,
2611            ref_counts: handle.ref_counts.clone(),
2612        }
2613    }
2614}
2615
2616impl Drop for AnyModelHandle {
2617    fn drop(&mut self) {
2618        self.ref_counts.lock().dec_model(self.model_id);
2619    }
2620}
2621pub struct WeakViewHandle<T> {
2622    window_id: usize,
2623    view_id: usize,
2624    view_type: PhantomData<T>,
2625}
2626
2627impl<T: View> WeakViewHandle<T> {
2628    fn new(window_id: usize, view_id: usize) -> Self {
2629        Self {
2630            window_id,
2631            view_id,
2632            view_type: PhantomData,
2633        }
2634    }
2635
2636    pub fn upgrade(&self, cx: impl AsRef<AppContext>) -> Option<ViewHandle<T>> {
2637        let cx = cx.as_ref();
2638        if cx.ref_counts.lock().is_entity_alive(self.view_id) {
2639            Some(ViewHandle::new(
2640                self.window_id,
2641                self.view_id,
2642                &cx.ref_counts,
2643            ))
2644        } else {
2645            None
2646        }
2647    }
2648}
2649
2650impl<T> Clone for WeakViewHandle<T> {
2651    fn clone(&self) -> Self {
2652        Self {
2653            window_id: self.window_id,
2654            view_id: self.view_id,
2655            view_type: PhantomData,
2656        }
2657    }
2658}
2659
2660pub struct ValueHandle<T> {
2661    value_type: PhantomData<T>,
2662    tag_type_id: TypeId,
2663    id: usize,
2664    ref_counts: Weak<Mutex<RefCounts>>,
2665}
2666
2667impl<T: 'static> ValueHandle<T> {
2668    fn new(tag_type_id: TypeId, id: usize, ref_counts: &Arc<Mutex<RefCounts>>) -> Self {
2669        ref_counts.lock().inc_value(tag_type_id, id);
2670        Self {
2671            value_type: PhantomData,
2672            tag_type_id,
2673            id,
2674            ref_counts: Arc::downgrade(ref_counts),
2675        }
2676    }
2677
2678    pub fn read<R>(&self, cx: &AppContext, f: impl FnOnce(&T) -> R) -> R {
2679        f(cx.values
2680            .read()
2681            .get(&(self.tag_type_id, self.id))
2682            .unwrap()
2683            .downcast_ref()
2684            .unwrap())
2685    }
2686
2687    pub fn update<R>(&self, cx: &AppContext, f: impl FnOnce(&mut T) -> R) -> R {
2688        f(cx.values
2689            .write()
2690            .get_mut(&(self.tag_type_id, self.id))
2691            .unwrap()
2692            .downcast_mut()
2693            .unwrap())
2694    }
2695}
2696
2697impl<T> Drop for ValueHandle<T> {
2698    fn drop(&mut self) {
2699        if let Some(ref_counts) = self.ref_counts.upgrade() {
2700            ref_counts.lock().dec_value(self.tag_type_id, self.id);
2701        }
2702    }
2703}
2704
2705#[derive(Default)]
2706struct RefCounts {
2707    entity_counts: HashMap<usize, usize>,
2708    value_counts: HashMap<(TypeId, usize), usize>,
2709    dropped_models: HashSet<usize>,
2710    dropped_views: HashSet<(usize, usize)>,
2711    dropped_values: HashSet<(TypeId, usize)>,
2712}
2713
2714impl RefCounts {
2715    fn inc_model(&mut self, model_id: usize) {
2716        match self.entity_counts.entry(model_id) {
2717            Entry::Occupied(mut entry) => *entry.get_mut() += 1,
2718            Entry::Vacant(entry) => {
2719                entry.insert(1);
2720                self.dropped_models.remove(&model_id);
2721            }
2722        }
2723    }
2724
2725    fn inc_view(&mut self, window_id: usize, view_id: usize) {
2726        match self.entity_counts.entry(view_id) {
2727            Entry::Occupied(mut entry) => *entry.get_mut() += 1,
2728            Entry::Vacant(entry) => {
2729                entry.insert(1);
2730                self.dropped_views.remove(&(window_id, view_id));
2731            }
2732        }
2733    }
2734
2735    fn inc_value(&mut self, tag_type_id: TypeId, id: usize) {
2736        *self.value_counts.entry((tag_type_id, id)).or_insert(0) += 1;
2737    }
2738
2739    fn dec_model(&mut self, model_id: usize) {
2740        let count = self.entity_counts.get_mut(&model_id).unwrap();
2741        *count -= 1;
2742        if *count == 0 {
2743            self.entity_counts.remove(&model_id);
2744            self.dropped_models.insert(model_id);
2745        }
2746    }
2747
2748    fn dec_view(&mut self, window_id: usize, view_id: usize) {
2749        let count = self.entity_counts.get_mut(&view_id).unwrap();
2750        *count -= 1;
2751        if *count == 0 {
2752            self.entity_counts.remove(&view_id);
2753            self.dropped_views.insert((window_id, view_id));
2754        }
2755    }
2756
2757    fn dec_value(&mut self, tag_type_id: TypeId, id: usize) {
2758        let key = (tag_type_id, id);
2759        let count = self.value_counts.get_mut(&key).unwrap();
2760        *count -= 1;
2761        if *count == 0 {
2762            self.value_counts.remove(&key);
2763            self.dropped_values.insert(key);
2764        }
2765    }
2766
2767    fn is_entity_alive(&self, entity_id: usize) -> bool {
2768        self.entity_counts.contains_key(&entity_id)
2769    }
2770
2771    fn take_dropped(
2772        &mut self,
2773    ) -> (
2774        HashSet<usize>,
2775        HashSet<(usize, usize)>,
2776        HashSet<(TypeId, usize)>,
2777    ) {
2778        let mut dropped_models = HashSet::new();
2779        let mut dropped_views = HashSet::new();
2780        let mut dropped_values = HashSet::new();
2781        std::mem::swap(&mut self.dropped_models, &mut dropped_models);
2782        std::mem::swap(&mut self.dropped_views, &mut dropped_views);
2783        std::mem::swap(&mut self.dropped_values, &mut dropped_values);
2784        (dropped_models, dropped_views, dropped_values)
2785    }
2786}
2787
2788enum Subscription {
2789    FromModel {
2790        model_id: usize,
2791        callback: Box<dyn FnMut(&mut dyn Any, &dyn Any, &mut MutableAppContext, usize)>,
2792    },
2793    FromView {
2794        window_id: usize,
2795        view_id: usize,
2796        callback: Box<dyn FnMut(&mut dyn Any, &dyn Any, &mut MutableAppContext, usize, usize)>,
2797    },
2798}
2799
2800enum ModelObservation {
2801    FromModel {
2802        model_id: usize,
2803        callback: Box<dyn FnMut(&mut dyn Any, usize, &mut MutableAppContext, usize)>,
2804    },
2805    FromView {
2806        window_id: usize,
2807        view_id: usize,
2808        callback: Box<dyn FnMut(&mut dyn Any, usize, &mut MutableAppContext, usize, usize)>,
2809    },
2810}
2811
2812struct ViewObservation {
2813    window_id: usize,
2814    view_id: usize,
2815    callback: Box<dyn FnMut(&mut dyn Any, usize, usize, &mut MutableAppContext, usize, usize)>,
2816}
2817
2818#[cfg(test)]
2819mod tests {
2820    use super::*;
2821    use crate::elements::*;
2822    use smol::future::poll_once;
2823    use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
2824
2825    #[crate::test(self)]
2826    fn test_model_handles(cx: &mut MutableAppContext) {
2827        struct Model {
2828            other: Option<ModelHandle<Model>>,
2829            events: Vec<String>,
2830        }
2831
2832        impl Entity for Model {
2833            type Event = usize;
2834        }
2835
2836        impl Model {
2837            fn new(other: Option<ModelHandle<Self>>, cx: &mut ModelContext<Self>) -> Self {
2838                if let Some(other) = other.as_ref() {
2839                    cx.observe(other, |me, _, _| {
2840                        me.events.push("notified".into());
2841                    });
2842                    cx.subscribe(other, |me, event, _| {
2843                        me.events.push(format!("observed event {}", event));
2844                    });
2845                }
2846
2847                Self {
2848                    other,
2849                    events: Vec::new(),
2850                }
2851            }
2852        }
2853
2854        let handle_1 = cx.add_model(|cx| Model::new(None, cx));
2855        let handle_2 = cx.add_model(|cx| Model::new(Some(handle_1.clone()), cx));
2856        assert_eq!(cx.cx.models.len(), 2);
2857
2858        handle_1.update(cx, |model, cx| {
2859            model.events.push("updated".into());
2860            cx.emit(1);
2861            cx.notify();
2862            cx.emit(2);
2863        });
2864        assert_eq!(handle_1.read(cx).events, vec!["updated".to_string()]);
2865        assert_eq!(
2866            handle_2.read(cx).events,
2867            vec![
2868                "observed event 1".to_string(),
2869                "notified".to_string(),
2870                "observed event 2".to_string(),
2871            ]
2872        );
2873
2874        handle_2.update(cx, |model, _| {
2875            drop(handle_1);
2876            model.other.take();
2877        });
2878
2879        assert_eq!(cx.cx.models.len(), 1);
2880        assert!(cx.subscriptions.is_empty());
2881        assert!(cx.model_observations.is_empty());
2882    }
2883
2884    #[crate::test(self)]
2885    fn test_subscribe_and_emit_from_model(cx: &mut MutableAppContext) {
2886        #[derive(Default)]
2887        struct Model {
2888            events: Vec<usize>,
2889        }
2890
2891        impl Entity for Model {
2892            type Event = usize;
2893        }
2894
2895        let handle_1 = cx.add_model(|_| Model::default());
2896        let handle_2 = cx.add_model(|_| Model::default());
2897        let handle_2b = handle_2.clone();
2898
2899        handle_1.update(cx, |_, c| {
2900            c.subscribe(&handle_2, move |model: &mut Model, event, c| {
2901                model.events.push(*event);
2902
2903                c.subscribe(&handle_2b, |model, event, _| {
2904                    model.events.push(*event * 2);
2905                });
2906            });
2907        });
2908
2909        handle_2.update(cx, |_, c| c.emit(7));
2910        assert_eq!(handle_1.read(cx).events, vec![7]);
2911
2912        handle_2.update(cx, |_, c| c.emit(5));
2913        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5]);
2914    }
2915
2916    #[crate::test(self)]
2917    fn test_observe_and_notify_from_model(cx: &mut MutableAppContext) {
2918        #[derive(Default)]
2919        struct Model {
2920            count: usize,
2921            events: Vec<usize>,
2922        }
2923
2924        impl Entity for Model {
2925            type Event = ();
2926        }
2927
2928        let handle_1 = cx.add_model(|_| Model::default());
2929        let handle_2 = cx.add_model(|_| Model::default());
2930        let handle_2b = handle_2.clone();
2931
2932        handle_1.update(cx, |_, c| {
2933            c.observe(&handle_2, move |model, observed, c| {
2934                model.events.push(observed.read(c).count);
2935                c.observe(&handle_2b, |model, observed, c| {
2936                    model.events.push(observed.read(c).count * 2);
2937                });
2938            });
2939        });
2940
2941        handle_2.update(cx, |model, c| {
2942            model.count = 7;
2943            c.notify()
2944        });
2945        assert_eq!(handle_1.read(cx).events, vec![7]);
2946
2947        handle_2.update(cx, |model, c| {
2948            model.count = 5;
2949            c.notify()
2950        });
2951        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5])
2952    }
2953
2954    #[crate::test(self)]
2955    fn test_view_handles(cx: &mut MutableAppContext) {
2956        struct View {
2957            other: Option<ViewHandle<View>>,
2958            events: Vec<String>,
2959        }
2960
2961        impl Entity for View {
2962            type Event = usize;
2963        }
2964
2965        impl super::View for View {
2966            fn render<'a>(&self, _: &AppContext) -> ElementBox {
2967                Empty::new().boxed()
2968            }
2969
2970            fn ui_name() -> &'static str {
2971                "View"
2972            }
2973        }
2974
2975        impl View {
2976            fn new(other: Option<ViewHandle<View>>, cx: &mut ViewContext<Self>) -> Self {
2977                if let Some(other) = other.as_ref() {
2978                    cx.subscribe_to_view(other, |me, _, event, _| {
2979                        me.events.push(format!("observed event {}", event));
2980                    });
2981                }
2982                Self {
2983                    other,
2984                    events: Vec::new(),
2985                }
2986            }
2987        }
2988
2989        let (window_id, _) = cx.add_window(|cx| View::new(None, cx));
2990        let handle_1 = cx.add_view(window_id, |cx| View::new(None, cx));
2991        let handle_2 = cx.add_view(window_id, |cx| View::new(Some(handle_1.clone()), cx));
2992        assert_eq!(cx.cx.views.len(), 3);
2993
2994        handle_1.update(cx, |view, cx| {
2995            view.events.push("updated".into());
2996            cx.emit(1);
2997            cx.emit(2);
2998        });
2999        assert_eq!(handle_1.read(cx).events, vec!["updated".to_string()]);
3000        assert_eq!(
3001            handle_2.read(cx).events,
3002            vec![
3003                "observed event 1".to_string(),
3004                "observed event 2".to_string(),
3005            ]
3006        );
3007
3008        handle_2.update(cx, |view, _| {
3009            drop(handle_1);
3010            view.other.take();
3011        });
3012
3013        assert_eq!(cx.cx.views.len(), 2);
3014        assert!(cx.subscriptions.is_empty());
3015        assert!(cx.model_observations.is_empty());
3016    }
3017
3018    #[crate::test(self)]
3019    fn test_add_window(cx: &mut MutableAppContext) {
3020        struct View {
3021            mouse_down_count: Arc<AtomicUsize>,
3022        }
3023
3024        impl Entity for View {
3025            type Event = ();
3026        }
3027
3028        impl super::View for View {
3029            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3030                let mouse_down_count = self.mouse_down_count.clone();
3031                EventHandler::new(Empty::new().boxed())
3032                    .on_mouse_down(move |_| {
3033                        mouse_down_count.fetch_add(1, SeqCst);
3034                        true
3035                    })
3036                    .boxed()
3037            }
3038
3039            fn ui_name() -> &'static str {
3040                "View"
3041            }
3042        }
3043
3044        let mouse_down_count = Arc::new(AtomicUsize::new(0));
3045        let (window_id, _) = cx.add_window(|_| View {
3046            mouse_down_count: mouse_down_count.clone(),
3047        });
3048        let presenter = cx.presenters_and_platform_windows[&window_id].0.clone();
3049        // Ensure window's root element is in a valid lifecycle state.
3050        presenter.borrow_mut().dispatch_event(
3051            Event::LeftMouseDown {
3052                position: Default::default(),
3053                cmd: false,
3054            },
3055            cx,
3056        );
3057        assert_eq!(mouse_down_count.load(SeqCst), 1);
3058    }
3059
3060    #[crate::test(self)]
3061    fn test_entity_release_hooks(cx: &mut MutableAppContext) {
3062        struct Model {
3063            released: Arc<Mutex<bool>>,
3064        }
3065
3066        struct View {
3067            released: Arc<Mutex<bool>>,
3068        }
3069
3070        impl Entity for Model {
3071            type Event = ();
3072
3073            fn release(&mut self, _: &mut MutableAppContext) {
3074                *self.released.lock() = true;
3075            }
3076        }
3077
3078        impl Entity for View {
3079            type Event = ();
3080
3081            fn release(&mut self, _: &mut MutableAppContext) {
3082                *self.released.lock() = true;
3083            }
3084        }
3085
3086        impl super::View for View {
3087            fn ui_name() -> &'static str {
3088                "View"
3089            }
3090
3091            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3092                Empty::new().boxed()
3093            }
3094        }
3095
3096        let model_released = Arc::new(Mutex::new(false));
3097        let view_released = Arc::new(Mutex::new(false));
3098
3099        let model = cx.add_model(|_| Model {
3100            released: model_released.clone(),
3101        });
3102
3103        let (window_id, _) = cx.add_window(|_| View {
3104            released: view_released.clone(),
3105        });
3106
3107        assert!(!*model_released.lock());
3108        assert!(!*view_released.lock());
3109
3110        cx.update(move || {
3111            drop(model);
3112        });
3113        assert!(*model_released.lock());
3114
3115        drop(cx.remove_window(window_id));
3116        assert!(*view_released.lock());
3117    }
3118
3119    #[crate::test(self)]
3120    fn test_subscribe_and_emit_from_view(cx: &mut MutableAppContext) {
3121        #[derive(Default)]
3122        struct View {
3123            events: Vec<usize>,
3124        }
3125
3126        impl Entity for View {
3127            type Event = usize;
3128        }
3129
3130        impl super::View for View {
3131            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3132                Empty::new().boxed()
3133            }
3134
3135            fn ui_name() -> &'static str {
3136                "View"
3137            }
3138        }
3139
3140        struct Model;
3141
3142        impl Entity for Model {
3143            type Event = usize;
3144        }
3145
3146        let (window_id, handle_1) = cx.add_window(|_| View::default());
3147        let handle_2 = cx.add_view(window_id, |_| View::default());
3148        let handle_2b = handle_2.clone();
3149        let handle_3 = cx.add_model(|_| Model);
3150
3151        handle_1.update(cx, |_, c| {
3152            c.subscribe_to_view(&handle_2, move |me, _, event, c| {
3153                me.events.push(*event);
3154
3155                c.subscribe_to_view(&handle_2b, |me, _, event, _| {
3156                    me.events.push(*event * 2);
3157                });
3158            });
3159
3160            c.subscribe_to_model(&handle_3, |me, _, event, _| {
3161                me.events.push(*event);
3162            })
3163        });
3164
3165        handle_2.update(cx, |_, c| c.emit(7));
3166        assert_eq!(handle_1.read(cx).events, vec![7]);
3167
3168        handle_2.update(cx, |_, c| c.emit(5));
3169        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5]);
3170
3171        handle_3.update(cx, |_, c| c.emit(9));
3172        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5, 9]);
3173    }
3174
3175    #[crate::test(self)]
3176    fn test_dropping_subscribers(cx: &mut MutableAppContext) {
3177        struct View;
3178
3179        impl Entity for View {
3180            type Event = ();
3181        }
3182
3183        impl super::View for View {
3184            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3185                Empty::new().boxed()
3186            }
3187
3188            fn ui_name() -> &'static str {
3189                "View"
3190            }
3191        }
3192
3193        struct Model;
3194
3195        impl Entity for Model {
3196            type Event = ();
3197        }
3198
3199        let (window_id, _) = cx.add_window(|_| View);
3200        let observing_view = cx.add_view(window_id, |_| View);
3201        let emitting_view = cx.add_view(window_id, |_| View);
3202        let observing_model = cx.add_model(|_| Model);
3203        let observed_model = cx.add_model(|_| Model);
3204
3205        observing_view.update(cx, |_, cx| {
3206            cx.subscribe_to_view(&emitting_view, |_, _, _, _| {});
3207            cx.subscribe_to_model(&observed_model, |_, _, _, _| {});
3208        });
3209        observing_model.update(cx, |_, cx| {
3210            cx.subscribe(&observed_model, |_, _, _| {});
3211        });
3212
3213        cx.update(|| {
3214            drop(observing_view);
3215            drop(observing_model);
3216        });
3217
3218        emitting_view.update(cx, |_, cx| cx.emit(()));
3219        observed_model.update(cx, |_, cx| cx.emit(()));
3220    }
3221
3222    #[crate::test(self)]
3223    fn test_observe_and_notify_from_view(cx: &mut MutableAppContext) {
3224        #[derive(Default)]
3225        struct View {
3226            events: Vec<usize>,
3227        }
3228
3229        impl Entity for View {
3230            type Event = usize;
3231        }
3232
3233        impl super::View for View {
3234            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3235                Empty::new().boxed()
3236            }
3237
3238            fn ui_name() -> &'static str {
3239                "View"
3240            }
3241        }
3242
3243        #[derive(Default)]
3244        struct Model {
3245            count: usize,
3246        }
3247
3248        impl Entity for Model {
3249            type Event = ();
3250        }
3251
3252        let (_, view) = cx.add_window(|_| View::default());
3253        let model = cx.add_model(|_| Model::default());
3254
3255        view.update(cx, |_, c| {
3256            c.observe_model(&model, |me, observed, c| {
3257                me.events.push(observed.read(c).count)
3258            });
3259        });
3260
3261        model.update(cx, |model, c| {
3262            model.count = 11;
3263            c.notify();
3264        });
3265        assert_eq!(view.read(cx).events, vec![11]);
3266    }
3267
3268    #[crate::test(self)]
3269    fn test_dropping_observers(cx: &mut MutableAppContext) {
3270        struct View;
3271
3272        impl Entity for View {
3273            type Event = ();
3274        }
3275
3276        impl super::View for View {
3277            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3278                Empty::new().boxed()
3279            }
3280
3281            fn ui_name() -> &'static str {
3282                "View"
3283            }
3284        }
3285
3286        struct Model;
3287
3288        impl Entity for Model {
3289            type Event = ();
3290        }
3291
3292        let (window_id, _) = cx.add_window(|_| View);
3293        let observing_view = cx.add_view(window_id, |_| View);
3294        let observing_model = cx.add_model(|_| Model);
3295        let observed_model = cx.add_model(|_| Model);
3296
3297        observing_view.update(cx, |_, cx| {
3298            cx.observe_model(&observed_model, |_, _, _| {});
3299        });
3300        observing_model.update(cx, |_, cx| {
3301            cx.observe(&observed_model, |_, _, _| {});
3302        });
3303
3304        cx.update(|| {
3305            drop(observing_view);
3306            drop(observing_model);
3307        });
3308
3309        observed_model.update(cx, |_, cx| cx.notify());
3310    }
3311
3312    #[crate::test(self)]
3313    fn test_focus(cx: &mut MutableAppContext) {
3314        struct View {
3315            name: String,
3316            events: Arc<Mutex<Vec<String>>>,
3317        }
3318
3319        impl Entity for View {
3320            type Event = ();
3321        }
3322
3323        impl super::View for View {
3324            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3325                Empty::new().boxed()
3326            }
3327
3328            fn ui_name() -> &'static str {
3329                "View"
3330            }
3331
3332            fn on_focus(&mut self, _: &mut ViewContext<Self>) {
3333                self.events.lock().push(format!("{} focused", &self.name));
3334            }
3335
3336            fn on_blur(&mut self, _: &mut ViewContext<Self>) {
3337                self.events.lock().push(format!("{} blurred", &self.name));
3338            }
3339        }
3340
3341        let events: Arc<Mutex<Vec<String>>> = Default::default();
3342        let (window_id, view_1) = cx.add_window(|_| View {
3343            events: events.clone(),
3344            name: "view 1".to_string(),
3345        });
3346        let view_2 = cx.add_view(window_id, |_| View {
3347            events: events.clone(),
3348            name: "view 2".to_string(),
3349        });
3350
3351        view_1.update(cx, |_, cx| cx.focus(&view_2));
3352        view_1.update(cx, |_, cx| cx.focus(&view_1));
3353        view_1.update(cx, |_, cx| cx.focus(&view_2));
3354        view_1.update(cx, |_, _| drop(view_2));
3355
3356        assert_eq!(
3357            *events.lock(),
3358            [
3359                "view 1 focused".to_string(),
3360                "view 1 blurred".to_string(),
3361                "view 2 focused".to_string(),
3362                "view 2 blurred".to_string(),
3363                "view 1 focused".to_string(),
3364                "view 1 blurred".to_string(),
3365                "view 2 focused".to_string(),
3366                "view 1 focused".to_string(),
3367            ],
3368        );
3369    }
3370
3371    #[crate::test(self)]
3372    fn test_dispatch_action(cx: &mut MutableAppContext) {
3373        struct ViewA {
3374            id: usize,
3375        }
3376
3377        impl Entity for ViewA {
3378            type Event = ();
3379        }
3380
3381        impl View for ViewA {
3382            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3383                Empty::new().boxed()
3384            }
3385
3386            fn ui_name() -> &'static str {
3387                "View"
3388            }
3389        }
3390
3391        struct ViewB {
3392            id: usize,
3393        }
3394
3395        impl Entity for ViewB {
3396            type Event = ();
3397        }
3398
3399        impl View for ViewB {
3400            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3401                Empty::new().boxed()
3402            }
3403
3404            fn ui_name() -> &'static str {
3405                "View"
3406            }
3407        }
3408
3409        struct ActionArg {
3410            foo: String,
3411        }
3412
3413        let actions = Rc::new(RefCell::new(Vec::new()));
3414
3415        let actions_clone = actions.clone();
3416        cx.add_global_action("action", move |_: &ActionArg, _: &mut MutableAppContext| {
3417            actions_clone.borrow_mut().push("global a".to_string());
3418        });
3419
3420        let actions_clone = actions.clone();
3421        cx.add_global_action("action", move |_: &ActionArg, _: &mut MutableAppContext| {
3422            actions_clone.borrow_mut().push("global b".to_string());
3423        });
3424
3425        let actions_clone = actions.clone();
3426        cx.add_action("action", move |view: &mut ViewA, arg: &ActionArg, cx| {
3427            assert_eq!(arg.foo, "bar");
3428            cx.propagate_action();
3429            actions_clone.borrow_mut().push(format!("{} a", view.id));
3430        });
3431
3432        let actions_clone = actions.clone();
3433        cx.add_action("action", move |view: &mut ViewA, _: &ActionArg, cx| {
3434            if view.id != 1 {
3435                cx.propagate_action();
3436            }
3437            actions_clone.borrow_mut().push(format!("{} b", view.id));
3438        });
3439
3440        let actions_clone = actions.clone();
3441        cx.add_action("action", move |view: &mut ViewB, _: &ActionArg, cx| {
3442            cx.propagate_action();
3443            actions_clone.borrow_mut().push(format!("{} c", view.id));
3444        });
3445
3446        let actions_clone = actions.clone();
3447        cx.add_action("action", move |view: &mut ViewB, _: &ActionArg, cx| {
3448            cx.propagate_action();
3449            actions_clone.borrow_mut().push(format!("{} d", view.id));
3450        });
3451
3452        let (window_id, view_1) = cx.add_window(|_| ViewA { id: 1 });
3453        let view_2 = cx.add_view(window_id, |_| ViewB { id: 2 });
3454        let view_3 = cx.add_view(window_id, |_| ViewA { id: 3 });
3455        let view_4 = cx.add_view(window_id, |_| ViewB { id: 4 });
3456
3457        cx.dispatch_action(
3458            window_id,
3459            vec![view_1.id(), view_2.id(), view_3.id(), view_4.id()],
3460            "action",
3461            ActionArg { foo: "bar".into() },
3462        );
3463
3464        assert_eq!(
3465            *actions.borrow(),
3466            vec!["4 d", "4 c", "3 b", "3 a", "2 d", "2 c", "1 b"]
3467        );
3468
3469        // Remove view_1, which doesn't propagate the action
3470        actions.borrow_mut().clear();
3471        cx.dispatch_action(
3472            window_id,
3473            vec![view_2.id(), view_3.id(), view_4.id()],
3474            "action",
3475            ActionArg { foo: "bar".into() },
3476        );
3477
3478        assert_eq!(
3479            *actions.borrow(),
3480            vec!["4 d", "4 c", "3 b", "3 a", "2 d", "2 c", "global b", "global a"]
3481        );
3482    }
3483
3484    #[crate::test(self)]
3485    fn test_dispatch_keystroke(cx: &mut MutableAppContext) {
3486        use std::cell::Cell;
3487
3488        #[derive(Clone)]
3489        struct ActionArg {
3490            key: String,
3491        }
3492
3493        struct View {
3494            id: usize,
3495            keymap_context: keymap::Context,
3496        }
3497
3498        impl Entity for View {
3499            type Event = ();
3500        }
3501
3502        impl super::View for View {
3503            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3504                Empty::new().boxed()
3505            }
3506
3507            fn ui_name() -> &'static str {
3508                "View"
3509            }
3510
3511            fn keymap_context(&self, _: &AppContext) -> keymap::Context {
3512                self.keymap_context.clone()
3513            }
3514        }
3515
3516        impl View {
3517            fn new(id: usize) -> Self {
3518                View {
3519                    id,
3520                    keymap_context: keymap::Context::default(),
3521                }
3522            }
3523        }
3524
3525        let mut view_1 = View::new(1);
3526        let mut view_2 = View::new(2);
3527        let mut view_3 = View::new(3);
3528        view_1.keymap_context.set.insert("a".into());
3529        view_2.keymap_context.set.insert("b".into());
3530        view_3.keymap_context.set.insert("c".into());
3531
3532        let (window_id, view_1) = cx.add_window(|_| view_1);
3533        let view_2 = cx.add_view(window_id, |_| view_2);
3534        let view_3 = cx.add_view(window_id, |_| view_3);
3535
3536        // This keymap's only binding dispatches an action on view 2 because that view will have
3537        // "a" and "b" in its context, but not "c".
3538        let binding = keymap::Binding::new("a", "action", Some("a && b && !c"))
3539            .with_arg(ActionArg { key: "a".into() });
3540        cx.add_bindings(vec![binding]);
3541
3542        let handled_action = Rc::new(Cell::new(false));
3543        let handled_action_clone = handled_action.clone();
3544        cx.add_action("action", move |view: &mut View, arg: &ActionArg, _| {
3545            handled_action_clone.set(true);
3546            assert_eq!(view.id, 2);
3547            assert_eq!(arg.key, "a");
3548        });
3549
3550        cx.dispatch_keystroke(
3551            window_id,
3552            vec![view_1.id(), view_2.id(), view_3.id()],
3553            &Keystroke::parse("a").unwrap(),
3554        )
3555        .unwrap();
3556
3557        assert!(handled_action.get());
3558    }
3559
3560    #[crate::test(self)]
3561    async fn test_model_condition(mut cx: TestAppContext) {
3562        struct Counter(usize);
3563
3564        impl super::Entity for Counter {
3565            type Event = ();
3566        }
3567
3568        impl Counter {
3569            fn inc(&mut self, cx: &mut ModelContext<Self>) {
3570                self.0 += 1;
3571                cx.notify();
3572            }
3573        }
3574
3575        let model = cx.add_model(|_| Counter(0));
3576
3577        let condition1 = model.condition(&cx, |model, _| model.0 == 2);
3578        let condition2 = model.condition(&cx, |model, _| model.0 == 3);
3579        smol::pin!(condition1, condition2);
3580
3581        model.update(&mut cx, |model, cx| model.inc(cx));
3582        assert_eq!(poll_once(&mut condition1).await, None);
3583        assert_eq!(poll_once(&mut condition2).await, None);
3584
3585        model.update(&mut cx, |model, cx| model.inc(cx));
3586        assert_eq!(poll_once(&mut condition1).await, Some(()));
3587        assert_eq!(poll_once(&mut condition2).await, None);
3588
3589        model.update(&mut cx, |model, cx| model.inc(cx));
3590        assert_eq!(poll_once(&mut condition2).await, Some(()));
3591
3592        model.update(&mut cx, |_, cx| cx.notify());
3593    }
3594
3595    #[crate::test(self)]
3596    #[should_panic]
3597    async fn test_model_condition_timeout(mut cx: TestAppContext) {
3598        struct Model;
3599
3600        impl super::Entity for Model {
3601            type Event = ();
3602        }
3603
3604        let model = cx.add_model(|_| Model);
3605        model.condition(&cx, |_, _| false).await;
3606    }
3607
3608    #[crate::test(self)]
3609    #[should_panic(expected = "model dropped with pending condition")]
3610    async fn test_model_condition_panic_on_drop(mut cx: TestAppContext) {
3611        struct Model;
3612
3613        impl super::Entity for Model {
3614            type Event = ();
3615        }
3616
3617        let model = cx.add_model(|_| Model);
3618        let condition = model.condition(&cx, |_, _| false);
3619        cx.update(|_| drop(model));
3620        condition.await;
3621    }
3622
3623    #[crate::test(self)]
3624    async fn test_view_condition(mut cx: TestAppContext) {
3625        struct Counter(usize);
3626
3627        impl super::Entity for Counter {
3628            type Event = ();
3629        }
3630
3631        impl super::View for Counter {
3632            fn ui_name() -> &'static str {
3633                "test view"
3634            }
3635
3636            fn render(&self, _: &AppContext) -> ElementBox {
3637                Empty::new().boxed()
3638            }
3639        }
3640
3641        impl Counter {
3642            fn inc(&mut self, cx: &mut ViewContext<Self>) {
3643                self.0 += 1;
3644                cx.notify();
3645            }
3646        }
3647
3648        let (_, view) = cx.add_window(|_| Counter(0));
3649
3650        let condition1 = view.condition(&cx, |view, _| view.0 == 2);
3651        let condition2 = view.condition(&cx, |view, _| view.0 == 3);
3652        smol::pin!(condition1, condition2);
3653
3654        view.update(&mut cx, |view, cx| view.inc(cx));
3655        assert_eq!(poll_once(&mut condition1).await, None);
3656        assert_eq!(poll_once(&mut condition2).await, None);
3657
3658        view.update(&mut cx, |view, cx| view.inc(cx));
3659        assert_eq!(poll_once(&mut condition1).await, Some(()));
3660        assert_eq!(poll_once(&mut condition2).await, None);
3661
3662        view.update(&mut cx, |view, cx| view.inc(cx));
3663        assert_eq!(poll_once(&mut condition2).await, Some(()));
3664        view.update(&mut cx, |_, cx| cx.notify());
3665    }
3666
3667    #[crate::test(self)]
3668    #[should_panic]
3669    async fn test_view_condition_timeout(mut cx: TestAppContext) {
3670        struct View;
3671
3672        impl super::Entity for View {
3673            type Event = ();
3674        }
3675
3676        impl super::View for View {
3677            fn ui_name() -> &'static str {
3678                "test view"
3679            }
3680
3681            fn render(&self, _: &AppContext) -> ElementBox {
3682                Empty::new().boxed()
3683            }
3684        }
3685
3686        let (_, view) = cx.add_window(|_| View);
3687        view.condition(&cx, |_, _| false).await;
3688    }
3689
3690    #[crate::test(self)]
3691    #[should_panic(expected = "view dropped with pending condition")]
3692    async fn test_view_condition_panic_on_drop(mut cx: TestAppContext) {
3693        struct View;
3694
3695        impl super::Entity for View {
3696            type Event = ();
3697        }
3698
3699        impl super::View for View {
3700            fn ui_name() -> &'static str {
3701                "test view"
3702            }
3703
3704            fn render(&self, _: &AppContext) -> ElementBox {
3705                Empty::new().boxed()
3706            }
3707        }
3708
3709        let window_id = cx.add_window(|_| View).0;
3710        let view = cx.add_view(window_id, |_| View);
3711
3712        let condition = view.condition(&cx, |_, _| false);
3713        cx.update(|_| drop(view));
3714        condition.await;
3715    }
3716}