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.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().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    platform: Arc<dyn platform::Platform>,
 570    assets: Arc<AssetCache>,
 571    cx: AppContext,
 572    actions: HashMap<TypeId, HashMap<String, Vec<Box<ActionCallback>>>>,
 573    global_actions: HashMap<String, Vec<Box<GlobalActionCallback>>>,
 574    keystroke_matcher: keymap::Matcher,
 575    next_entity_id: usize,
 576    next_window_id: usize,
 577    subscriptions: HashMap<usize, Vec<Subscription>>,
 578    model_observations: HashMap<usize, Vec<ModelObservation>>,
 579    view_observations: HashMap<usize, Vec<ViewObservation>>,
 580    presenters_and_platform_windows:
 581        HashMap<usize, (Rc<RefCell<Presenter>>, Box<dyn platform::Window>)>,
 582    debug_elements_callbacks: HashMap<usize, Box<dyn Fn(&AppContext) -> crate::json::Value>>,
 583    foreground: Rc<executor::Foreground>,
 584    pending_effects: VecDeque<Effect>,
 585    pending_flushes: usize,
 586    flushing_effects: bool,
 587}
 588
 589impl MutableAppContext {
 590    fn new(
 591        foreground: Rc<executor::Foreground>,
 592        background: Arc<executor::Background>,
 593        platform: Arc<dyn platform::Platform>,
 594        foreground_platform: Rc<dyn platform::ForegroundPlatform>,
 595        asset_source: impl AssetSource,
 596    ) -> Self {
 597        let fonts = platform.fonts();
 598        Self {
 599            weak_self: None,
 600            foreground_platform,
 601            platform,
 602            assets: Arc::new(AssetCache::new(asset_source)),
 603            cx: AppContext {
 604                models: Default::default(),
 605                views: Default::default(),
 606                windows: Default::default(),
 607                values: Default::default(),
 608                ref_counts: Arc::new(Mutex::new(RefCounts::default())),
 609                background,
 610                thread_pool: scoped_pool::Pool::new(num_cpus::get(), "app"),
 611                font_cache: Arc::new(FontCache::new(fonts)),
 612            },
 613            actions: HashMap::new(),
 614            global_actions: HashMap::new(),
 615            keystroke_matcher: keymap::Matcher::default(),
 616            next_entity_id: 0,
 617            next_window_id: 0,
 618            subscriptions: HashMap::new(),
 619            model_observations: HashMap::new(),
 620            view_observations: HashMap::new(),
 621            presenters_and_platform_windows: HashMap::new(),
 622            debug_elements_callbacks: HashMap::new(),
 623            foreground,
 624            pending_effects: VecDeque::new(),
 625            pending_flushes: 0,
 626            flushing_effects: false,
 627        }
 628    }
 629
 630    pub fn upgrade(&self) -> App {
 631        App(self.weak_self.as_ref().unwrap().upgrade().unwrap())
 632    }
 633
 634    pub fn platform(&self) -> Arc<dyn platform::Platform> {
 635        self.platform.clone()
 636    }
 637
 638    pub fn font_cache(&self) -> &Arc<FontCache> {
 639        &self.cx.font_cache
 640    }
 641
 642    pub fn foreground(&self) -> &Rc<executor::Foreground> {
 643        &self.foreground
 644    }
 645
 646    pub fn background(&self) -> &Arc<executor::Background> {
 647        &self.cx.background
 648    }
 649
 650    pub fn on_debug_elements<F>(&mut self, window_id: usize, callback: F)
 651    where
 652        F: 'static + Fn(&AppContext) -> crate::json::Value,
 653    {
 654        self.debug_elements_callbacks
 655            .insert(window_id, Box::new(callback));
 656    }
 657
 658    pub fn debug_elements(&self, window_id: usize) -> Option<crate::json::Value> {
 659        self.debug_elements_callbacks
 660            .get(&window_id)
 661            .map(|debug_elements| debug_elements(&self.cx))
 662    }
 663
 664    pub fn add_action<S, V, T, F>(&mut self, name: S, mut handler: F)
 665    where
 666        S: Into<String>,
 667        V: View,
 668        T: Any,
 669        F: 'static + FnMut(&mut V, &T, &mut ViewContext<V>),
 670    {
 671        let name = name.into();
 672        let name_clone = name.clone();
 673        let handler = Box::new(
 674            move |view: &mut dyn AnyView,
 675                  arg: &dyn Any,
 676                  cx: &mut MutableAppContext,
 677                  window_id: usize,
 678                  view_id: usize| {
 679                match arg.downcast_ref() {
 680                    Some(arg) => {
 681                        let mut cx = ViewContext::new(cx, window_id, view_id);
 682                        handler(
 683                            view.as_any_mut()
 684                                .downcast_mut()
 685                                .expect("downcast is type safe"),
 686                            arg,
 687                            &mut cx,
 688                        );
 689                        cx.halt_action_dispatch
 690                    }
 691                    None => {
 692                        log::error!("Could not downcast argument for action {}", name_clone);
 693                        false
 694                    }
 695                }
 696            },
 697        );
 698
 699        self.actions
 700            .entry(TypeId::of::<V>())
 701            .or_default()
 702            .entry(name)
 703            .or_default()
 704            .push(handler);
 705    }
 706
 707    pub fn add_global_action<S, T, F>(&mut self, name: S, mut handler: F)
 708    where
 709        S: Into<String>,
 710        T: 'static + Any,
 711        F: 'static + FnMut(&T, &mut MutableAppContext),
 712    {
 713        let name = name.into();
 714        let name_clone = name.clone();
 715        let handler = Box::new(move |arg: &dyn Any, cx: &mut MutableAppContext| {
 716            if let Some(arg) = arg.downcast_ref() {
 717                handler(arg, cx);
 718            } else {
 719                log::error!("Could not downcast argument for action {}", name_clone);
 720            }
 721        });
 722
 723        self.global_actions.entry(name).or_default().push(handler);
 724    }
 725
 726    pub fn window_ids(&self) -> impl Iterator<Item = usize> + '_ {
 727        self.cx.windows.keys().cloned()
 728    }
 729
 730    pub fn root_view<T: View>(&self, window_id: usize) -> Option<ViewHandle<T>> {
 731        self.cx
 732            .windows
 733            .get(&window_id)
 734            .and_then(|window| window.root_view.clone().downcast::<T>())
 735    }
 736
 737    pub fn root_view_id(&self, window_id: usize) -> Option<usize> {
 738        self.cx.root_view_id(window_id)
 739    }
 740
 741    pub fn focused_view_id(&self, window_id: usize) -> Option<usize> {
 742        self.cx.focused_view_id(window_id)
 743    }
 744
 745    pub fn render_view(&self, window_id: usize, view_id: usize) -> Result<ElementBox> {
 746        self.cx.render_view(window_id, view_id)
 747    }
 748
 749    pub fn render_views(&self, window_id: usize) -> HashMap<usize, ElementBox> {
 750        self.cx.render_views(window_id)
 751    }
 752
 753    pub fn update<T, F: FnOnce() -> T>(&mut self, callback: F) -> T {
 754        self.pending_flushes += 1;
 755        let result = callback();
 756        self.flush_effects();
 757        result
 758    }
 759
 760    pub fn set_menus(&mut self, menus: Vec<Menu>) {
 761        self.foreground_platform.set_menus(menus);
 762    }
 763
 764    fn prompt<F>(
 765        &self,
 766        window_id: usize,
 767        level: PromptLevel,
 768        msg: &str,
 769        answers: &[&str],
 770        done_fn: F,
 771    ) where
 772        F: 'static + FnOnce(usize, &mut MutableAppContext),
 773    {
 774        let app = self.weak_self.as_ref().unwrap().upgrade().unwrap();
 775        let foreground = self.foreground.clone();
 776        let (_, window) = &self.presenters_and_platform_windows[&window_id];
 777        window.prompt(
 778            level,
 779            msg,
 780            answers,
 781            Box::new(move |answer| {
 782                foreground
 783                    .spawn(async move { (done_fn)(answer, &mut *app.borrow_mut()) })
 784                    .detach();
 785            }),
 786        );
 787    }
 788
 789    pub fn prompt_for_paths<F>(&self, options: PathPromptOptions, done_fn: F)
 790    where
 791        F: 'static + FnOnce(Option<Vec<PathBuf>>, &mut MutableAppContext),
 792    {
 793        let app = self.weak_self.as_ref().unwrap().upgrade().unwrap();
 794        let foreground = self.foreground.clone();
 795        self.foreground_platform.prompt_for_paths(
 796            options,
 797            Box::new(move |paths| {
 798                foreground
 799                    .spawn(async move { (done_fn)(paths, &mut *app.borrow_mut()) })
 800                    .detach();
 801            }),
 802        );
 803    }
 804
 805    pub fn prompt_for_new_path<F>(&self, directory: &Path, done_fn: F)
 806    where
 807        F: 'static + FnOnce(Option<PathBuf>, &mut MutableAppContext),
 808    {
 809        let app = self.weak_self.as_ref().unwrap().upgrade().unwrap();
 810        let foreground = self.foreground.clone();
 811        self.foreground_platform.prompt_for_new_path(
 812            directory,
 813            Box::new(move |path| {
 814                foreground
 815                    .spawn(async move { (done_fn)(path, &mut *app.borrow_mut()) })
 816                    .detach();
 817            }),
 818        );
 819    }
 820
 821    pub(crate) fn notify_view(&mut self, window_id: usize, view_id: usize) {
 822        self.pending_effects
 823            .push_back(Effect::ViewNotification { window_id, view_id });
 824    }
 825
 826    pub fn dispatch_action<T: 'static + Any>(
 827        &mut self,
 828        window_id: usize,
 829        responder_chain: Vec<usize>,
 830        name: &str,
 831        arg: T,
 832    ) {
 833        self.dispatch_action_any(window_id, &responder_chain, name, Box::new(arg).as_ref());
 834    }
 835
 836    pub(crate) fn dispatch_action_any(
 837        &mut self,
 838        window_id: usize,
 839        path: &[usize],
 840        name: &str,
 841        arg: &dyn Any,
 842    ) -> bool {
 843        self.pending_flushes += 1;
 844        let mut halted_dispatch = false;
 845
 846        for view_id in path.iter().rev() {
 847            if let Some(mut view) = self.cx.views.remove(&(window_id, *view_id)) {
 848                let type_id = view.as_any().type_id();
 849
 850                if let Some((name, mut handlers)) = self
 851                    .actions
 852                    .get_mut(&type_id)
 853                    .and_then(|h| h.remove_entry(name))
 854                {
 855                    for handler in handlers.iter_mut().rev() {
 856                        let halt_dispatch = handler(view.as_mut(), arg, self, window_id, *view_id);
 857                        if halt_dispatch {
 858                            halted_dispatch = true;
 859                            break;
 860                        }
 861                    }
 862                    self.actions
 863                        .get_mut(&type_id)
 864                        .unwrap()
 865                        .insert(name, handlers);
 866                }
 867
 868                self.cx.views.insert((window_id, *view_id), view);
 869
 870                if halted_dispatch {
 871                    break;
 872                }
 873            }
 874        }
 875
 876        if !halted_dispatch {
 877            self.dispatch_global_action_any(name, arg);
 878        }
 879
 880        self.flush_effects();
 881        halted_dispatch
 882    }
 883
 884    pub fn dispatch_global_action<T: 'static + Any>(&mut self, name: &str, arg: T) {
 885        self.dispatch_global_action_any(name, Box::new(arg).as_ref());
 886    }
 887
 888    fn dispatch_global_action_any(&mut self, name: &str, arg: &dyn Any) {
 889        if let Some((name, mut handlers)) = self.global_actions.remove_entry(name) {
 890            self.pending_flushes += 1;
 891            for handler in handlers.iter_mut().rev() {
 892                handler(arg, self);
 893            }
 894            self.global_actions.insert(name, handlers);
 895            self.flush_effects();
 896        }
 897    }
 898
 899    pub fn add_bindings<T: IntoIterator<Item = keymap::Binding>>(&mut self, bindings: T) {
 900        self.keystroke_matcher.add_bindings(bindings);
 901    }
 902
 903    pub fn dispatch_keystroke(
 904        &mut self,
 905        window_id: usize,
 906        responder_chain: Vec<usize>,
 907        keystroke: &Keystroke,
 908    ) -> Result<bool> {
 909        let mut context_chain = Vec::new();
 910        let mut context = keymap::Context::default();
 911        for view_id in &responder_chain {
 912            if let Some(view) = self.cx.views.get(&(window_id, *view_id)) {
 913                context.extend(view.keymap_context(self.as_ref()));
 914                context_chain.push(context.clone());
 915            } else {
 916                return Err(anyhow!(
 917                    "View {} in responder chain does not exist",
 918                    view_id
 919                ));
 920            }
 921        }
 922
 923        let mut pending = false;
 924        for (i, cx) in context_chain.iter().enumerate().rev() {
 925            match self
 926                .keystroke_matcher
 927                .push_keystroke(keystroke.clone(), responder_chain[i], cx)
 928            {
 929                MatchResult::None => {}
 930                MatchResult::Pending => pending = true,
 931                MatchResult::Action { name, arg } => {
 932                    if self.dispatch_action_any(
 933                        window_id,
 934                        &responder_chain[0..=i],
 935                        &name,
 936                        arg.as_ref().map(|arg| arg.as_ref()).unwrap_or(&()),
 937                    ) {
 938                        return Ok(true);
 939                    }
 940                }
 941            }
 942        }
 943
 944        Ok(pending)
 945    }
 946
 947    pub fn add_model<T, F>(&mut self, build_model: F) -> ModelHandle<T>
 948    where
 949        T: Entity,
 950        F: FnOnce(&mut ModelContext<T>) -> T,
 951    {
 952        self.pending_flushes += 1;
 953        let model_id = post_inc(&mut self.next_entity_id);
 954        let handle = ModelHandle::new(model_id, &self.cx.ref_counts);
 955        let mut cx = ModelContext::new(self, model_id);
 956        let model = build_model(&mut cx);
 957        self.cx.models.insert(model_id, Box::new(model));
 958        self.flush_effects();
 959        handle
 960    }
 961
 962    pub fn add_window<T, F>(&mut self, build_root_view: F) -> (usize, ViewHandle<T>)
 963    where
 964        T: View,
 965        F: FnOnce(&mut ViewContext<T>) -> T,
 966    {
 967        self.pending_flushes += 1;
 968        let window_id = post_inc(&mut self.next_window_id);
 969        let root_view = self.add_view(window_id, build_root_view);
 970
 971        self.cx.windows.insert(
 972            window_id,
 973            Window {
 974                root_view: root_view.clone().into(),
 975                focused_view_id: root_view.id(),
 976                invalidation: None,
 977            },
 978        );
 979        self.open_platform_window(window_id);
 980        root_view.update(self, |view, cx| {
 981            view.on_focus(cx);
 982            cx.notify();
 983        });
 984        self.flush_effects();
 985
 986        (window_id, root_view)
 987    }
 988
 989    pub fn remove_window(&mut self, window_id: usize) {
 990        self.cx.windows.remove(&window_id);
 991        self.presenters_and_platform_windows.remove(&window_id);
 992        self.remove_dropped_entities();
 993    }
 994
 995    fn open_platform_window(&mut self, window_id: usize) {
 996        let mut window = self.platform.open_window(
 997            window_id,
 998            WindowOptions {
 999                bounds: RectF::new(vec2f(0., 0.), vec2f(1024., 768.)),
1000                title: "Zed".into(),
1001            },
1002            self.foreground.clone(),
1003        );
1004        let text_layout_cache = TextLayoutCache::new(self.platform.fonts());
1005        let presenter = Rc::new(RefCell::new(Presenter::new(
1006            window_id,
1007            self.cx.font_cache.clone(),
1008            text_layout_cache,
1009            self.assets.clone(),
1010            self,
1011        )));
1012
1013        {
1014            let mut app = self.upgrade();
1015            let presenter = presenter.clone();
1016            window.on_event(Box::new(move |event| {
1017                app.update(|cx| {
1018                    if let Event::KeyDown { keystroke, .. } = &event {
1019                        if cx
1020                            .dispatch_keystroke(
1021                                window_id,
1022                                presenter.borrow().dispatch_path(cx.as_ref()),
1023                                keystroke,
1024                            )
1025                            .unwrap()
1026                        {
1027                            return;
1028                        }
1029                    }
1030
1031                    presenter.borrow_mut().dispatch_event(event, cx);
1032                })
1033            }));
1034        }
1035
1036        {
1037            let mut app = self.upgrade();
1038            let presenter = presenter.clone();
1039            window.on_resize(Box::new(move |window| {
1040                app.update(|cx| {
1041                    let scene = presenter.borrow_mut().build_scene(
1042                        window.size(),
1043                        window.scale_factor(),
1044                        cx,
1045                    );
1046                    window.present_scene(scene);
1047                })
1048            }));
1049        }
1050
1051        {
1052            let mut app = self.upgrade();
1053            window.on_close(Box::new(move || {
1054                app.update(|cx| cx.remove_window(window_id));
1055            }));
1056        }
1057
1058        self.presenters_and_platform_windows
1059            .insert(window_id, (presenter.clone(), window));
1060
1061        self.on_debug_elements(window_id, move |cx| {
1062            presenter.borrow().debug_elements(cx).unwrap()
1063        });
1064    }
1065
1066    pub fn add_view<T, F>(&mut self, window_id: usize, build_view: F) -> ViewHandle<T>
1067    where
1068        T: View,
1069        F: FnOnce(&mut ViewContext<T>) -> T,
1070    {
1071        self.add_option_view(window_id, |cx| Some(build_view(cx)))
1072            .unwrap()
1073    }
1074
1075    pub fn add_option_view<T, F>(
1076        &mut self,
1077        window_id: usize,
1078        build_view: F,
1079    ) -> Option<ViewHandle<T>>
1080    where
1081        T: View,
1082        F: FnOnce(&mut ViewContext<T>) -> Option<T>,
1083    {
1084        let view_id = post_inc(&mut self.next_entity_id);
1085        self.pending_flushes += 1;
1086        let handle = ViewHandle::new(window_id, view_id, &self.cx.ref_counts);
1087        let mut cx = ViewContext::new(self, window_id, view_id);
1088        let handle = if let Some(view) = build_view(&mut cx) {
1089            self.cx.views.insert((window_id, view_id), Box::new(view));
1090            if let Some(window) = self.cx.windows.get_mut(&window_id) {
1091                window
1092                    .invalidation
1093                    .get_or_insert_with(Default::default)
1094                    .updated
1095                    .insert(view_id);
1096            }
1097            Some(handle)
1098        } else {
1099            None
1100        };
1101        self.flush_effects();
1102        handle
1103    }
1104
1105    fn remove_dropped_entities(&mut self) {
1106        loop {
1107            let (dropped_models, dropped_views, dropped_values) =
1108                self.cx.ref_counts.lock().take_dropped();
1109            if dropped_models.is_empty() && dropped_views.is_empty() && dropped_values.is_empty() {
1110                break;
1111            }
1112
1113            for model_id in dropped_models {
1114                self.subscriptions.remove(&model_id);
1115                self.model_observations.remove(&model_id);
1116                let mut model = self.cx.models.remove(&model_id).unwrap();
1117                model.release(self);
1118            }
1119
1120            for (window_id, view_id) in dropped_views {
1121                self.subscriptions.remove(&view_id);
1122                self.model_observations.remove(&view_id);
1123                let mut view = self.cx.views.remove(&(window_id, view_id)).unwrap();
1124                view.release(self);
1125                let change_focus_to = self.cx.windows.get_mut(&window_id).and_then(|window| {
1126                    window
1127                        .invalidation
1128                        .get_or_insert_with(Default::default)
1129                        .removed
1130                        .push(view_id);
1131                    if window.focused_view_id == view_id {
1132                        Some(window.root_view.id())
1133                    } else {
1134                        None
1135                    }
1136                });
1137
1138                if let Some(view_id) = change_focus_to {
1139                    self.focus(window_id, view_id);
1140                }
1141            }
1142
1143            let mut values = self.cx.values.write();
1144            for key in dropped_values {
1145                values.remove(&key);
1146            }
1147        }
1148    }
1149
1150    fn flush_effects(&mut self) {
1151        self.pending_flushes = self.pending_flushes.saturating_sub(1);
1152
1153        if !self.flushing_effects && self.pending_flushes == 0 {
1154            self.flushing_effects = true;
1155
1156            loop {
1157                if let Some(effect) = self.pending_effects.pop_front() {
1158                    match effect {
1159                        Effect::Event { entity_id, payload } => self.emit_event(entity_id, payload),
1160                        Effect::ModelNotification { model_id } => {
1161                            self.notify_model_observers(model_id)
1162                        }
1163                        Effect::ViewNotification { window_id, view_id } => {
1164                            self.notify_view_observers(window_id, view_id)
1165                        }
1166                        Effect::Focus { window_id, view_id } => {
1167                            self.focus(window_id, view_id);
1168                        }
1169                    }
1170                    self.remove_dropped_entities();
1171                } else {
1172                    self.remove_dropped_entities();
1173                    self.update_windows();
1174
1175                    if self.pending_effects.is_empty() {
1176                        self.flushing_effects = false;
1177                        break;
1178                    }
1179                }
1180            }
1181        }
1182    }
1183
1184    fn update_windows(&mut self) {
1185        let mut invalidations = HashMap::new();
1186        for (window_id, window) in &mut self.cx.windows {
1187            if let Some(invalidation) = window.invalidation.take() {
1188                invalidations.insert(*window_id, invalidation);
1189            }
1190        }
1191
1192        for (window_id, invalidation) in invalidations {
1193            if let Some((presenter, mut window)) =
1194                self.presenters_and_platform_windows.remove(&window_id)
1195            {
1196                {
1197                    let mut presenter = presenter.borrow_mut();
1198                    presenter.invalidate(invalidation, self.as_ref());
1199                    let scene = presenter.build_scene(window.size(), window.scale_factor(), self);
1200                    window.present_scene(scene);
1201                }
1202                self.presenters_and_platform_windows
1203                    .insert(window_id, (presenter, window));
1204            }
1205        }
1206    }
1207
1208    fn emit_event(&mut self, entity_id: usize, payload: Box<dyn Any>) {
1209        if let Some(subscriptions) = self.subscriptions.remove(&entity_id) {
1210            for mut subscription in subscriptions {
1211                let alive = match &mut subscription {
1212                    Subscription::FromModel { model_id, callback } => {
1213                        if let Some(mut model) = self.cx.models.remove(model_id) {
1214                            callback(model.as_any_mut(), payload.as_ref(), self, *model_id);
1215                            self.cx.models.insert(*model_id, model);
1216                            true
1217                        } else {
1218                            false
1219                        }
1220                    }
1221                    Subscription::FromView {
1222                        window_id,
1223                        view_id,
1224                        callback,
1225                    } => {
1226                        if let Some(mut view) = self.cx.views.remove(&(*window_id, *view_id)) {
1227                            callback(
1228                                view.as_any_mut(),
1229                                payload.as_ref(),
1230                                self,
1231                                *window_id,
1232                                *view_id,
1233                            );
1234                            self.cx.views.insert((*window_id, *view_id), view);
1235                            true
1236                        } else {
1237                            false
1238                        }
1239                    }
1240                };
1241
1242                if alive {
1243                    self.subscriptions
1244                        .entry(entity_id)
1245                        .or_default()
1246                        .push(subscription);
1247                }
1248            }
1249        }
1250    }
1251
1252    fn notify_model_observers(&mut self, observed_id: usize) {
1253        if let Some(observations) = self.model_observations.remove(&observed_id) {
1254            if self.cx.models.contains_key(&observed_id) {
1255                for mut observation in observations {
1256                    let alive = match &mut observation {
1257                        ModelObservation::FromModel { model_id, callback } => {
1258                            if let Some(mut model) = self.cx.models.remove(model_id) {
1259                                callback(model.as_any_mut(), observed_id, self, *model_id);
1260                                self.cx.models.insert(*model_id, model);
1261                                true
1262                            } else {
1263                                false
1264                            }
1265                        }
1266                        ModelObservation::FromView {
1267                            window_id,
1268                            view_id,
1269                            callback,
1270                        } => {
1271                            if let Some(mut view) = self.cx.views.remove(&(*window_id, *view_id)) {
1272                                callback(
1273                                    view.as_any_mut(),
1274                                    observed_id,
1275                                    self,
1276                                    *window_id,
1277                                    *view_id,
1278                                );
1279                                self.cx.views.insert((*window_id, *view_id), view);
1280                                true
1281                            } else {
1282                                false
1283                            }
1284                        }
1285                    };
1286
1287                    if alive {
1288                        self.model_observations
1289                            .entry(observed_id)
1290                            .or_default()
1291                            .push(observation);
1292                    }
1293                }
1294            }
1295        }
1296    }
1297
1298    fn notify_view_observers(&mut self, window_id: usize, view_id: usize) {
1299        if let Some(window) = self.cx.windows.get_mut(&window_id) {
1300            window
1301                .invalidation
1302                .get_or_insert_with(Default::default)
1303                .updated
1304                .insert(view_id);
1305        }
1306
1307        if let Some(observations) = self.view_observations.remove(&view_id) {
1308            if self.cx.views.contains_key(&(window_id, view_id)) {
1309                for mut observation in observations {
1310                    let alive = if let Some(mut view) = self
1311                        .cx
1312                        .views
1313                        .remove(&(observation.window_id, observation.view_id))
1314                    {
1315                        (observation.callback)(
1316                            view.as_any_mut(),
1317                            view_id,
1318                            window_id,
1319                            self,
1320                            observation.window_id,
1321                            observation.view_id,
1322                        );
1323                        self.cx
1324                            .views
1325                            .insert((observation.window_id, observation.view_id), view);
1326                        true
1327                    } else {
1328                        false
1329                    };
1330
1331                    if alive {
1332                        self.view_observations
1333                            .entry(view_id)
1334                            .or_default()
1335                            .push(observation);
1336                    }
1337                }
1338            }
1339        }
1340    }
1341
1342    fn focus(&mut self, window_id: usize, focused_id: usize) {
1343        if self
1344            .cx
1345            .windows
1346            .get(&window_id)
1347            .map(|w| w.focused_view_id)
1348            .map_or(false, |cur_focused| cur_focused == focused_id)
1349        {
1350            return;
1351        }
1352
1353        self.pending_flushes += 1;
1354
1355        let blurred_id = self.cx.windows.get_mut(&window_id).map(|window| {
1356            let blurred_id = window.focused_view_id;
1357            window.focused_view_id = focused_id;
1358            blurred_id
1359        });
1360
1361        if let Some(blurred_id) = blurred_id {
1362            if let Some(mut blurred_view) = self.cx.views.remove(&(window_id, blurred_id)) {
1363                blurred_view.on_blur(self, window_id, blurred_id);
1364                self.cx.views.insert((window_id, blurred_id), blurred_view);
1365            }
1366        }
1367
1368        if let Some(mut focused_view) = self.cx.views.remove(&(window_id, focused_id)) {
1369            focused_view.on_focus(self, window_id, focused_id);
1370            self.cx.views.insert((window_id, focused_id), focused_view);
1371        }
1372
1373        self.flush_effects();
1374    }
1375
1376    pub fn spawn<F, Fut, T>(&self, f: F) -> Task<T>
1377    where
1378        F: FnOnce(AsyncAppContext) -> Fut,
1379        Fut: 'static + Future<Output = T>,
1380        T: 'static,
1381    {
1382        let cx = self.to_async();
1383        self.foreground.spawn(f(cx))
1384    }
1385
1386    pub fn to_async(&self) -> AsyncAppContext {
1387        AsyncAppContext(self.weak_self.as_ref().unwrap().upgrade().unwrap())
1388    }
1389
1390    pub fn write_to_clipboard(&self, item: ClipboardItem) {
1391        self.platform.write_to_clipboard(item);
1392    }
1393
1394    pub fn read_from_clipboard(&self) -> Option<ClipboardItem> {
1395        self.platform.read_from_clipboard()
1396    }
1397}
1398
1399impl ReadModel for MutableAppContext {
1400    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
1401        if let Some(model) = self.cx.models.get(&handle.model_id) {
1402            model
1403                .as_any()
1404                .downcast_ref()
1405                .expect("downcast is type safe")
1406        } else {
1407            panic!("circular model reference");
1408        }
1409    }
1410}
1411
1412impl UpdateModel for MutableAppContext {
1413    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
1414    where
1415        T: Entity,
1416        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
1417    {
1418        if let Some(mut model) = self.cx.models.remove(&handle.model_id) {
1419            self.pending_flushes += 1;
1420            let mut cx = ModelContext::new(self, handle.model_id);
1421            let result = update(
1422                model
1423                    .as_any_mut()
1424                    .downcast_mut()
1425                    .expect("downcast is type safe"),
1426                &mut cx,
1427            );
1428            self.cx.models.insert(handle.model_id, model);
1429            self.flush_effects();
1430            result
1431        } else {
1432            panic!("circular model update");
1433        }
1434    }
1435}
1436
1437impl ReadView for MutableAppContext {
1438    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T {
1439        if let Some(view) = self.cx.views.get(&(handle.window_id, handle.view_id)) {
1440            view.as_any().downcast_ref().expect("downcast is type safe")
1441        } else {
1442            panic!("circular view reference");
1443        }
1444    }
1445}
1446
1447impl UpdateView for MutableAppContext {
1448    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
1449    where
1450        T: View,
1451        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
1452    {
1453        self.pending_flushes += 1;
1454        let mut view = self
1455            .cx
1456            .views
1457            .remove(&(handle.window_id, handle.view_id))
1458            .expect("circular view update");
1459
1460        let mut cx = ViewContext::new(self, handle.window_id, handle.view_id);
1461        let result = update(
1462            view.as_any_mut()
1463                .downcast_mut()
1464                .expect("downcast is type safe"),
1465            &mut cx,
1466        );
1467        self.cx
1468            .views
1469            .insert((handle.window_id, handle.view_id), view);
1470        self.flush_effects();
1471        result
1472    }
1473}
1474
1475impl AsRef<AppContext> for MutableAppContext {
1476    fn as_ref(&self) -> &AppContext {
1477        &self.cx
1478    }
1479}
1480
1481pub struct AppContext {
1482    models: HashMap<usize, Box<dyn AnyModel>>,
1483    views: HashMap<(usize, usize), Box<dyn AnyView>>,
1484    windows: HashMap<usize, Window>,
1485    values: RwLock<HashMap<(TypeId, usize), Box<dyn Any>>>,
1486    background: Arc<executor::Background>,
1487    ref_counts: Arc<Mutex<RefCounts>>,
1488    thread_pool: scoped_pool::Pool,
1489    font_cache: Arc<FontCache>,
1490}
1491
1492impl AppContext {
1493    pub fn root_view_id(&self, window_id: usize) -> Option<usize> {
1494        self.windows
1495            .get(&window_id)
1496            .map(|window| window.root_view.id())
1497    }
1498
1499    pub fn focused_view_id(&self, window_id: usize) -> Option<usize> {
1500        self.windows
1501            .get(&window_id)
1502            .map(|window| window.focused_view_id)
1503    }
1504
1505    pub fn render_view(&self, window_id: usize, view_id: usize) -> Result<ElementBox> {
1506        self.views
1507            .get(&(window_id, view_id))
1508            .map(|v| v.render(self))
1509            .ok_or(anyhow!("view not found"))
1510    }
1511
1512    pub fn render_views(&self, window_id: usize) -> HashMap<usize, ElementBox> {
1513        self.views
1514            .iter()
1515            .filter_map(|((win_id, view_id), view)| {
1516                if *win_id == window_id {
1517                    Some((*view_id, view.render(self)))
1518                } else {
1519                    None
1520                }
1521            })
1522            .collect::<HashMap<_, ElementBox>>()
1523    }
1524
1525    pub fn background(&self) -> &Arc<executor::Background> {
1526        &self.background
1527    }
1528
1529    pub fn font_cache(&self) -> &FontCache {
1530        &self.font_cache
1531    }
1532
1533    pub fn thread_pool(&self) -> &scoped_pool::Pool {
1534        &self.thread_pool
1535    }
1536
1537    pub fn value<Tag: 'static, T: 'static + Default>(&self, id: usize) -> ValueHandle<T> {
1538        let key = (TypeId::of::<Tag>(), id);
1539        let mut values = self.values.write();
1540        values.entry(key).or_insert_with(|| Box::new(T::default()));
1541        ValueHandle::new(TypeId::of::<Tag>(), id, &self.ref_counts)
1542    }
1543}
1544
1545impl ReadModel for AppContext {
1546    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
1547        if let Some(model) = self.models.get(&handle.model_id) {
1548            model
1549                .as_any()
1550                .downcast_ref()
1551                .expect("downcast should be type safe")
1552        } else {
1553            panic!("circular model reference");
1554        }
1555    }
1556}
1557
1558impl ReadView for AppContext {
1559    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T {
1560        if let Some(view) = self.views.get(&(handle.window_id, handle.view_id)) {
1561            view.as_any()
1562                .downcast_ref()
1563                .expect("downcast should be type safe")
1564        } else {
1565            panic!("circular view reference");
1566        }
1567    }
1568}
1569
1570struct Window {
1571    root_view: AnyViewHandle,
1572    focused_view_id: usize,
1573    invalidation: Option<WindowInvalidation>,
1574}
1575
1576#[derive(Default, Clone)]
1577pub struct WindowInvalidation {
1578    pub updated: HashSet<usize>,
1579    pub removed: Vec<usize>,
1580}
1581
1582pub enum Effect {
1583    Event {
1584        entity_id: usize,
1585        payload: Box<dyn Any>,
1586    },
1587    ModelNotification {
1588        model_id: usize,
1589    },
1590    ViewNotification {
1591        window_id: usize,
1592        view_id: usize,
1593    },
1594    Focus {
1595        window_id: usize,
1596        view_id: usize,
1597    },
1598}
1599
1600impl Debug for Effect {
1601    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1602        match self {
1603            Effect::Event { entity_id, .. } => f
1604                .debug_struct("Effect::Event")
1605                .field("entity_id", entity_id)
1606                .finish(),
1607            Effect::ModelNotification { model_id } => f
1608                .debug_struct("Effect::ModelNotification")
1609                .field("model_id", model_id)
1610                .finish(),
1611            Effect::ViewNotification { window_id, view_id } => f
1612                .debug_struct("Effect::ViewNotification")
1613                .field("window_id", window_id)
1614                .field("view_id", view_id)
1615                .finish(),
1616            Effect::Focus { window_id, view_id } => f
1617                .debug_struct("Effect::Focus")
1618                .field("window_id", window_id)
1619                .field("view_id", view_id)
1620                .finish(),
1621        }
1622    }
1623}
1624
1625pub trait AnyModel: Send + Sync {
1626    fn as_any(&self) -> &dyn Any;
1627    fn as_any_mut(&mut self) -> &mut dyn Any;
1628    fn release(&mut self, cx: &mut MutableAppContext);
1629}
1630
1631impl<T> AnyModel for T
1632where
1633    T: Entity,
1634{
1635    fn as_any(&self) -> &dyn Any {
1636        self
1637    }
1638
1639    fn as_any_mut(&mut self) -> &mut dyn Any {
1640        self
1641    }
1642
1643    fn release(&mut self, cx: &mut MutableAppContext) {
1644        self.release(cx);
1645    }
1646}
1647
1648pub trait AnyView: Send + Sync {
1649    fn as_any(&self) -> &dyn Any;
1650    fn as_any_mut(&mut self) -> &mut dyn Any;
1651    fn release(&mut self, cx: &mut MutableAppContext);
1652    fn ui_name(&self) -> &'static str;
1653    fn render<'a>(&self, cx: &AppContext) -> ElementBox;
1654    fn on_focus(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize);
1655    fn on_blur(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize);
1656    fn keymap_context(&self, cx: &AppContext) -> keymap::Context;
1657}
1658
1659impl<T> AnyView for T
1660where
1661    T: View,
1662{
1663    fn as_any(&self) -> &dyn Any {
1664        self
1665    }
1666
1667    fn as_any_mut(&mut self) -> &mut dyn Any {
1668        self
1669    }
1670
1671    fn release(&mut self, cx: &mut MutableAppContext) {
1672        self.release(cx);
1673    }
1674
1675    fn ui_name(&self) -> &'static str {
1676        T::ui_name()
1677    }
1678
1679    fn render<'a>(&self, cx: &AppContext) -> ElementBox {
1680        View::render(self, cx)
1681    }
1682
1683    fn on_focus(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize) {
1684        let mut cx = ViewContext::new(cx, window_id, view_id);
1685        View::on_focus(self, &mut cx);
1686    }
1687
1688    fn on_blur(&mut self, cx: &mut MutableAppContext, window_id: usize, view_id: usize) {
1689        let mut cx = ViewContext::new(cx, window_id, view_id);
1690        View::on_blur(self, &mut cx);
1691    }
1692
1693    fn keymap_context(&self, cx: &AppContext) -> keymap::Context {
1694        View::keymap_context(self, cx)
1695    }
1696}
1697
1698pub struct ModelContext<'a, T: ?Sized> {
1699    app: &'a mut MutableAppContext,
1700    model_id: usize,
1701    model_type: PhantomData<T>,
1702    halt_stream: bool,
1703}
1704
1705impl<'a, T: Entity> ModelContext<'a, T> {
1706    fn new(app: &'a mut MutableAppContext, model_id: usize) -> Self {
1707        Self {
1708            app,
1709            model_id,
1710            model_type: PhantomData,
1711            halt_stream: false,
1712        }
1713    }
1714
1715    pub fn background(&self) -> &Arc<executor::Background> {
1716        &self.app.cx.background
1717    }
1718
1719    pub fn thread_pool(&self) -> &scoped_pool::Pool {
1720        &self.app.cx.thread_pool
1721    }
1722
1723    pub fn halt_stream(&mut self) {
1724        self.halt_stream = true;
1725    }
1726
1727    pub fn model_id(&self) -> usize {
1728        self.model_id
1729    }
1730
1731    pub fn add_model<S, F>(&mut self, build_model: F) -> ModelHandle<S>
1732    where
1733        S: Entity,
1734        F: FnOnce(&mut ModelContext<S>) -> S,
1735    {
1736        self.app.add_model(build_model)
1737    }
1738
1739    pub fn subscribe<S: Entity, F>(&mut self, handle: &ModelHandle<S>, mut callback: F)
1740    where
1741        S::Event: 'static,
1742        F: 'static + FnMut(&mut T, &S::Event, &mut ModelContext<T>),
1743    {
1744        self.app
1745            .subscriptions
1746            .entry(handle.model_id)
1747            .or_default()
1748            .push(Subscription::FromModel {
1749                model_id: self.model_id,
1750                callback: Box::new(move |model, payload, app, model_id| {
1751                    let model = model.downcast_mut().expect("downcast is type safe");
1752                    let payload = payload.downcast_ref().expect("downcast is type safe");
1753                    let mut cx = ModelContext::new(app, model_id);
1754                    callback(model, payload, &mut cx);
1755                }),
1756            });
1757    }
1758
1759    pub fn emit(&mut self, payload: T::Event) {
1760        self.app.pending_effects.push_back(Effect::Event {
1761            entity_id: self.model_id,
1762            payload: Box::new(payload),
1763        });
1764    }
1765
1766    pub fn observe<S, F>(&mut self, handle: &ModelHandle<S>, mut callback: F)
1767    where
1768        S: Entity,
1769        F: 'static + FnMut(&mut T, ModelHandle<S>, &mut ModelContext<T>),
1770    {
1771        self.app
1772            .model_observations
1773            .entry(handle.model_id)
1774            .or_default()
1775            .push(ModelObservation::FromModel {
1776                model_id: self.model_id,
1777                callback: Box::new(move |model, observed_id, app, model_id| {
1778                    let model = model.downcast_mut().expect("downcast is type safe");
1779                    let observed = ModelHandle::new(observed_id, &app.cx.ref_counts);
1780                    let mut cx = ModelContext::new(app, model_id);
1781                    callback(model, observed, &mut cx);
1782                }),
1783            });
1784    }
1785
1786    pub fn notify(&mut self) {
1787        self.app
1788            .pending_effects
1789            .push_back(Effect::ModelNotification {
1790                model_id: self.model_id,
1791            });
1792    }
1793
1794    pub fn handle(&self) -> ModelHandle<T> {
1795        ModelHandle::new(self.model_id, &self.app.cx.ref_counts)
1796    }
1797
1798    pub fn spawn<F, Fut, S>(&self, f: F) -> Task<S>
1799    where
1800        F: FnOnce(ModelHandle<T>, AsyncAppContext) -> Fut,
1801        Fut: 'static + Future<Output = S>,
1802        S: 'static,
1803    {
1804        let handle = self.handle();
1805        self.app.spawn(|cx| f(handle, cx))
1806    }
1807
1808    pub fn spawn_weak<F, Fut, S>(&self, f: F) -> Task<S>
1809    where
1810        F: FnOnce(WeakModelHandle<T>, AsyncAppContext) -> Fut,
1811        Fut: 'static + Future<Output = S>,
1812        S: 'static,
1813    {
1814        let handle = self.handle().downgrade();
1815        self.app.spawn(|cx| f(handle, cx))
1816    }
1817}
1818
1819impl<M> AsRef<AppContext> for ModelContext<'_, M> {
1820    fn as_ref(&self) -> &AppContext {
1821        &self.app.cx
1822    }
1823}
1824
1825impl<M> AsMut<MutableAppContext> for ModelContext<'_, M> {
1826    fn as_mut(&mut self) -> &mut MutableAppContext {
1827        self.app
1828    }
1829}
1830
1831impl<M> ReadModel for ModelContext<'_, M> {
1832    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
1833        self.app.read_model(handle)
1834    }
1835}
1836
1837impl<M> UpdateModel for ModelContext<'_, M> {
1838    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
1839    where
1840        T: Entity,
1841        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
1842    {
1843        self.app.update_model(handle, update)
1844    }
1845}
1846
1847pub struct ViewContext<'a, T: ?Sized> {
1848    app: &'a mut MutableAppContext,
1849    window_id: usize,
1850    view_id: usize,
1851    view_type: PhantomData<T>,
1852    halt_action_dispatch: bool,
1853}
1854
1855impl<'a, T: View> ViewContext<'a, T> {
1856    fn new(app: &'a mut MutableAppContext, window_id: usize, view_id: usize) -> Self {
1857        Self {
1858            app,
1859            window_id,
1860            view_id,
1861            view_type: PhantomData,
1862            halt_action_dispatch: true,
1863        }
1864    }
1865
1866    pub fn handle(&self) -> ViewHandle<T> {
1867        ViewHandle::new(self.window_id, self.view_id, &self.app.cx.ref_counts)
1868    }
1869
1870    pub fn window_id(&self) -> usize {
1871        self.window_id
1872    }
1873
1874    pub fn view_id(&self) -> usize {
1875        self.view_id
1876    }
1877
1878    pub fn foreground(&self) -> &Rc<executor::Foreground> {
1879        self.app.foreground()
1880    }
1881
1882    pub fn background_executor(&self) -> &Arc<executor::Background> {
1883        &self.app.cx.background
1884    }
1885
1886    pub fn platform(&self) -> Arc<dyn Platform> {
1887        self.app.platform()
1888    }
1889
1890    pub fn prompt<F>(&self, level: PromptLevel, msg: &str, answers: &[&str], done_fn: F)
1891    where
1892        F: 'static + FnOnce(usize, &mut MutableAppContext),
1893    {
1894        self.app
1895            .prompt(self.window_id, level, msg, answers, done_fn)
1896    }
1897
1898    pub fn prompt_for_paths<F>(&self, options: PathPromptOptions, done_fn: F)
1899    where
1900        F: 'static + FnOnce(Option<Vec<PathBuf>>, &mut MutableAppContext),
1901    {
1902        self.app.prompt_for_paths(options, done_fn)
1903    }
1904
1905    pub fn prompt_for_new_path<F>(&self, directory: &Path, done_fn: F)
1906    where
1907        F: 'static + FnOnce(Option<PathBuf>, &mut MutableAppContext),
1908    {
1909        self.app.prompt_for_new_path(directory, done_fn)
1910    }
1911
1912    pub fn debug_elements(&self) -> crate::json::Value {
1913        self.app.debug_elements(self.window_id).unwrap()
1914    }
1915
1916    pub fn focus<S>(&mut self, handle: S)
1917    where
1918        S: Into<AnyViewHandle>,
1919    {
1920        let handle = handle.into();
1921        self.app.pending_effects.push_back(Effect::Focus {
1922            window_id: handle.window_id,
1923            view_id: handle.view_id,
1924        });
1925    }
1926
1927    pub fn focus_self(&mut self) {
1928        self.app.pending_effects.push_back(Effect::Focus {
1929            window_id: self.window_id,
1930            view_id: self.view_id,
1931        });
1932    }
1933
1934    pub fn add_model<S, F>(&mut self, build_model: F) -> ModelHandle<S>
1935    where
1936        S: Entity,
1937        F: FnOnce(&mut ModelContext<S>) -> S,
1938    {
1939        self.app.add_model(build_model)
1940    }
1941
1942    pub fn add_view<S, F>(&mut self, build_view: F) -> ViewHandle<S>
1943    where
1944        S: View,
1945        F: FnOnce(&mut ViewContext<S>) -> S,
1946    {
1947        self.app.add_view(self.window_id, build_view)
1948    }
1949
1950    pub fn add_option_view<S, F>(&mut self, build_view: F) -> Option<ViewHandle<S>>
1951    where
1952        S: View,
1953        F: FnOnce(&mut ViewContext<S>) -> Option<S>,
1954    {
1955        self.app.add_option_view(self.window_id, build_view)
1956    }
1957
1958    pub fn subscribe_to_model<E, F>(&mut self, handle: &ModelHandle<E>, mut callback: F)
1959    where
1960        E: Entity,
1961        E::Event: 'static,
1962        F: 'static + FnMut(&mut T, ModelHandle<E>, &E::Event, &mut ViewContext<T>),
1963    {
1964        let emitter_handle = handle.downgrade();
1965        self.subscribe(handle, move |model, payload, cx| {
1966            if let Some(emitter_handle) = emitter_handle.upgrade(cx.as_ref()) {
1967                callback(model, emitter_handle, payload, cx);
1968            }
1969        });
1970    }
1971
1972    pub fn subscribe_to_view<V, F>(&mut self, handle: &ViewHandle<V>, mut callback: F)
1973    where
1974        V: View,
1975        V::Event: 'static,
1976        F: 'static + FnMut(&mut T, ViewHandle<V>, &V::Event, &mut ViewContext<T>),
1977    {
1978        let emitter_handle = handle.downgrade();
1979        self.subscribe(handle, move |view, payload, cx| {
1980            if let Some(emitter_handle) = emitter_handle.upgrade(cx.as_ref()) {
1981                callback(view, emitter_handle, payload, cx);
1982            }
1983        });
1984    }
1985
1986    pub fn subscribe<E, F>(&mut self, handle: &impl Handle<E>, mut callback: F)
1987    where
1988        E: Entity,
1989        E::Event: 'static,
1990        F: 'static + FnMut(&mut T, &E::Event, &mut ViewContext<T>),
1991    {
1992        self.app
1993            .subscriptions
1994            .entry(handle.id())
1995            .or_default()
1996            .push(Subscription::FromView {
1997                window_id: self.window_id,
1998                view_id: self.view_id,
1999                callback: Box::new(move |entity, payload, app, window_id, view_id| {
2000                    let entity = entity.downcast_mut().expect("downcast is type safe");
2001                    let payload = payload.downcast_ref().expect("downcast is type safe");
2002                    let mut cx = ViewContext::new(app, window_id, view_id);
2003                    callback(entity, payload, &mut cx);
2004                }),
2005            });
2006    }
2007
2008    pub fn emit(&mut self, payload: T::Event) {
2009        self.app.pending_effects.push_back(Effect::Event {
2010            entity_id: self.view_id,
2011            payload: Box::new(payload),
2012        });
2013    }
2014
2015    pub fn observe_model<S, F>(&mut self, handle: &ModelHandle<S>, mut callback: F)
2016    where
2017        S: Entity,
2018        F: 'static + FnMut(&mut T, ModelHandle<S>, &mut ViewContext<T>),
2019    {
2020        self.app
2021            .model_observations
2022            .entry(handle.id())
2023            .or_default()
2024            .push(ModelObservation::FromView {
2025                window_id: self.window_id,
2026                view_id: self.view_id,
2027                callback: Box::new(move |view, observed_id, app, window_id, view_id| {
2028                    let view = view.downcast_mut().expect("downcast is type safe");
2029                    let observed = ModelHandle::new(observed_id, &app.cx.ref_counts);
2030                    let mut cx = ViewContext::new(app, window_id, view_id);
2031                    callback(view, observed, &mut cx);
2032                }),
2033            });
2034    }
2035
2036    pub fn observe_view<S, F>(&mut self, handle: &ViewHandle<S>, mut callback: F)
2037    where
2038        S: View,
2039        F: 'static + FnMut(&mut T, ViewHandle<S>, &mut ViewContext<T>),
2040    {
2041        self.app
2042            .view_observations
2043            .entry(handle.id())
2044            .or_default()
2045            .push(ViewObservation {
2046                window_id: self.window_id,
2047                view_id: self.view_id,
2048                callback: Box::new(
2049                    move |view,
2050                          observed_view_id,
2051                          observed_window_id,
2052                          app,
2053                          observing_window_id,
2054                          observing_view_id| {
2055                        let view = view.downcast_mut().expect("downcast is type safe");
2056                        let observed_handle = ViewHandle::new(
2057                            observed_view_id,
2058                            observed_window_id,
2059                            &app.cx.ref_counts,
2060                        );
2061                        let mut cx = ViewContext::new(app, observing_window_id, observing_view_id);
2062                        callback(view, observed_handle, &mut cx);
2063                    },
2064                ),
2065            });
2066    }
2067
2068    pub fn notify(&mut self) {
2069        self.app.notify_view(self.window_id, self.view_id);
2070    }
2071
2072    pub fn propagate_action(&mut self) {
2073        self.halt_action_dispatch = false;
2074    }
2075
2076    pub fn spawn<F, Fut, S>(&self, f: F) -> Task<S>
2077    where
2078        F: FnOnce(ViewHandle<T>, AsyncAppContext) -> Fut,
2079        Fut: 'static + Future<Output = S>,
2080        S: 'static,
2081    {
2082        let handle = self.handle();
2083        self.app.spawn(|cx| f(handle, cx))
2084    }
2085}
2086
2087impl AsRef<AppContext> for &AppContext {
2088    fn as_ref(&self) -> &AppContext {
2089        self
2090    }
2091}
2092
2093impl<M> AsRef<AppContext> for ViewContext<'_, M> {
2094    fn as_ref(&self) -> &AppContext {
2095        &self.app.cx
2096    }
2097}
2098
2099impl<M> AsMut<MutableAppContext> for ViewContext<'_, M> {
2100    fn as_mut(&mut self) -> &mut MutableAppContext {
2101        self.app
2102    }
2103}
2104
2105impl<V> ReadModel for ViewContext<'_, V> {
2106    fn read_model<T: Entity>(&self, handle: &ModelHandle<T>) -> &T {
2107        self.app.read_model(handle)
2108    }
2109}
2110
2111impl<V: View> UpdateModel for ViewContext<'_, V> {
2112    fn update_model<T, F, S>(&mut self, handle: &ModelHandle<T>, update: F) -> S
2113    where
2114        T: Entity,
2115        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
2116    {
2117        self.app.update_model(handle, update)
2118    }
2119}
2120
2121impl<V: View> ReadView for ViewContext<'_, V> {
2122    fn read_view<T: View>(&self, handle: &ViewHandle<T>) -> &T {
2123        self.app.read_view(handle)
2124    }
2125}
2126
2127impl<V: View> UpdateView for ViewContext<'_, V> {
2128    fn update_view<T, F, S>(&mut self, handle: &ViewHandle<T>, update: F) -> S
2129    where
2130        T: View,
2131        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
2132    {
2133        self.app.update_view(handle, update)
2134    }
2135}
2136
2137pub trait Handle<T> {
2138    fn id(&self) -> usize;
2139    fn location(&self) -> EntityLocation;
2140}
2141
2142#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
2143pub enum EntityLocation {
2144    Model(usize),
2145    View(usize, usize),
2146}
2147
2148pub struct ModelHandle<T> {
2149    model_id: usize,
2150    model_type: PhantomData<T>,
2151    ref_counts: Arc<Mutex<RefCounts>>,
2152}
2153
2154impl<T: Entity> ModelHandle<T> {
2155    fn new(model_id: usize, ref_counts: &Arc<Mutex<RefCounts>>) -> Self {
2156        ref_counts.lock().inc_model(model_id);
2157        Self {
2158            model_id,
2159            model_type: PhantomData,
2160            ref_counts: ref_counts.clone(),
2161        }
2162    }
2163
2164    pub fn downgrade(&self) -> WeakModelHandle<T> {
2165        WeakModelHandle::new(self.model_id)
2166    }
2167
2168    pub fn id(&self) -> usize {
2169        self.model_id
2170    }
2171
2172    pub fn read<'a, C: ReadModel>(&self, cx: &'a C) -> &'a T {
2173        cx.read_model(self)
2174    }
2175
2176    pub fn read_with<'a, C, F, S>(&self, cx: &C, read: F) -> S
2177    where
2178        C: ReadModelWith,
2179        F: FnOnce(&T, &AppContext) -> S,
2180    {
2181        cx.read_model_with(self, read)
2182    }
2183
2184    pub fn update<C, F, S>(&self, cx: &mut C, update: F) -> S
2185    where
2186        C: UpdateModel,
2187        F: FnOnce(&mut T, &mut ModelContext<T>) -> S,
2188    {
2189        cx.update_model(self, update)
2190    }
2191
2192    pub fn condition(
2193        &self,
2194        cx: &TestAppContext,
2195        mut predicate: impl FnMut(&T, &AppContext) -> bool,
2196    ) -> impl Future<Output = ()> {
2197        let (tx, mut rx) = mpsc::channel(1024);
2198
2199        let mut cx = cx.cx.borrow_mut();
2200        self.update(&mut *cx, |_, cx| {
2201            cx.observe(self, {
2202                let mut tx = tx.clone();
2203                move |_, _, _| {
2204                    tx.blocking_send(()).ok();
2205                }
2206            });
2207            cx.subscribe(self, {
2208                let mut tx = tx.clone();
2209                move |_, _, _| {
2210                    tx.blocking_send(()).ok();
2211                }
2212            })
2213        });
2214
2215        let cx = cx.weak_self.as_ref().unwrap().upgrade().unwrap();
2216        let handle = self.downgrade();
2217        let duration = if std::env::var("CI").is_ok() {
2218            Duration::from_secs(5)
2219        } else {
2220            Duration::from_secs(1)
2221        };
2222
2223        async move {
2224            timeout(duration, async move {
2225                loop {
2226                    {
2227                        let cx = cx.borrow();
2228                        let cx = cx.as_ref();
2229                        if predicate(
2230                            handle
2231                                .upgrade(cx)
2232                                .expect("model dropped with pending condition")
2233                                .read(cx),
2234                            cx,
2235                        ) {
2236                            break;
2237                        }
2238                    }
2239
2240                    rx.recv()
2241                        .await
2242                        .expect("model dropped with pending condition");
2243                }
2244            })
2245            .await
2246            .expect("condition timed out");
2247        }
2248    }
2249}
2250
2251impl<T> Clone for ModelHandle<T> {
2252    fn clone(&self) -> Self {
2253        self.ref_counts.lock().inc_model(self.model_id);
2254        Self {
2255            model_id: self.model_id,
2256            model_type: PhantomData,
2257            ref_counts: self.ref_counts.clone(),
2258        }
2259    }
2260}
2261
2262impl<T> PartialEq for ModelHandle<T> {
2263    fn eq(&self, other: &Self) -> bool {
2264        self.model_id == other.model_id
2265    }
2266}
2267
2268impl<T> Eq for ModelHandle<T> {}
2269
2270impl<T> Hash for ModelHandle<T> {
2271    fn hash<H: Hasher>(&self, state: &mut H) {
2272        self.model_id.hash(state);
2273    }
2274}
2275
2276impl<T> std::borrow::Borrow<usize> for ModelHandle<T> {
2277    fn borrow(&self) -> &usize {
2278        &self.model_id
2279    }
2280}
2281
2282impl<T> Debug for ModelHandle<T> {
2283    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2284        f.debug_tuple(&format!("ModelHandle<{}>", type_name::<T>()))
2285            .field(&self.model_id)
2286            .finish()
2287    }
2288}
2289
2290unsafe impl<T> Send for ModelHandle<T> {}
2291unsafe impl<T> Sync for ModelHandle<T> {}
2292
2293impl<T> Drop for ModelHandle<T> {
2294    fn drop(&mut self) {
2295        self.ref_counts.lock().dec_model(self.model_id);
2296    }
2297}
2298
2299impl<T> Handle<T> for ModelHandle<T> {
2300    fn id(&self) -> usize {
2301        self.model_id
2302    }
2303
2304    fn location(&self) -> EntityLocation {
2305        EntityLocation::Model(self.model_id)
2306    }
2307}
2308
2309pub struct WeakModelHandle<T> {
2310    model_id: usize,
2311    model_type: PhantomData<T>,
2312}
2313
2314impl<T: Entity> WeakModelHandle<T> {
2315    fn new(model_id: usize) -> Self {
2316        Self {
2317            model_id,
2318            model_type: PhantomData,
2319        }
2320    }
2321
2322    pub fn upgrade(&self, cx: impl AsRef<AppContext>) -> Option<ModelHandle<T>> {
2323        let cx = cx.as_ref();
2324        if cx.models.contains_key(&self.model_id) {
2325            Some(ModelHandle::new(self.model_id, &cx.ref_counts))
2326        } else {
2327            None
2328        }
2329    }
2330}
2331
2332impl<T> Hash for WeakModelHandle<T> {
2333    fn hash<H: Hasher>(&self, state: &mut H) {
2334        self.model_id.hash(state)
2335    }
2336}
2337
2338impl<T> PartialEq for WeakModelHandle<T> {
2339    fn eq(&self, other: &Self) -> bool {
2340        self.model_id == other.model_id
2341    }
2342}
2343
2344impl<T> Eq for WeakModelHandle<T> {}
2345
2346impl<T> Clone for WeakModelHandle<T> {
2347    fn clone(&self) -> Self {
2348        Self {
2349            model_id: self.model_id,
2350            model_type: PhantomData,
2351        }
2352    }
2353}
2354
2355pub struct ViewHandle<T> {
2356    window_id: usize,
2357    view_id: usize,
2358    view_type: PhantomData<T>,
2359    ref_counts: Arc<Mutex<RefCounts>>,
2360}
2361
2362impl<T: View> ViewHandle<T> {
2363    fn new(window_id: usize, view_id: usize, ref_counts: &Arc<Mutex<RefCounts>>) -> Self {
2364        ref_counts.lock().inc_view(window_id, view_id);
2365        Self {
2366            window_id,
2367            view_id,
2368            view_type: PhantomData,
2369            ref_counts: ref_counts.clone(),
2370        }
2371    }
2372
2373    pub fn downgrade(&self) -> WeakViewHandle<T> {
2374        WeakViewHandle::new(self.window_id, self.view_id)
2375    }
2376
2377    pub fn window_id(&self) -> usize {
2378        self.window_id
2379    }
2380
2381    pub fn id(&self) -> usize {
2382        self.view_id
2383    }
2384
2385    pub fn read<'a, C: ReadView>(&self, cx: &'a C) -> &'a T {
2386        cx.read_view(self)
2387    }
2388
2389    pub fn read_with<C, F, S>(&self, cx: &C, read: F) -> S
2390    where
2391        C: ReadViewWith,
2392        F: FnOnce(&T, &AppContext) -> S,
2393    {
2394        cx.read_view_with(self, read)
2395    }
2396
2397    pub fn update<C, F, S>(&self, cx: &mut C, update: F) -> S
2398    where
2399        C: UpdateView,
2400        F: FnOnce(&mut T, &mut ViewContext<T>) -> S,
2401    {
2402        cx.update_view(self, update)
2403    }
2404
2405    pub fn is_focused(&self, cx: &AppContext) -> bool {
2406        cx.focused_view_id(self.window_id)
2407            .map_or(false, |focused_id| focused_id == self.view_id)
2408    }
2409
2410    pub fn condition(
2411        &self,
2412        cx: &TestAppContext,
2413        mut predicate: impl FnMut(&T, &AppContext) -> bool,
2414    ) -> impl Future<Output = ()> {
2415        let (tx, mut rx) = mpsc::channel(1024);
2416
2417        let mut cx = cx.cx.borrow_mut();
2418        self.update(&mut *cx, |_, cx| {
2419            cx.observe_view(self, {
2420                let mut tx = tx.clone();
2421                move |_, _, _| {
2422                    tx.blocking_send(()).ok();
2423                }
2424            });
2425
2426            cx.subscribe(self, {
2427                let mut tx = tx.clone();
2428                move |_, _, _| {
2429                    tx.blocking_send(()).ok();
2430                }
2431            })
2432        });
2433
2434        let cx = cx.weak_self.as_ref().unwrap().upgrade().unwrap();
2435        let handle = self.downgrade();
2436        let duration = if std::env::var("CI").is_ok() {
2437            Duration::from_secs(2)
2438        } else {
2439            Duration::from_millis(500)
2440        };
2441
2442        async move {
2443            timeout(duration, async move {
2444                loop {
2445                    {
2446                        let cx = cx.borrow();
2447                        let cx = cx.as_ref();
2448                        if predicate(
2449                            handle
2450                                .upgrade(cx)
2451                                .expect("view dropped with pending condition")
2452                                .read(cx),
2453                            cx,
2454                        ) {
2455                            break;
2456                        }
2457                    }
2458
2459                    rx.recv()
2460                        .await
2461                        .expect("view dropped with pending condition");
2462                }
2463            })
2464            .await
2465            .expect("condition timed out");
2466        }
2467    }
2468}
2469
2470impl<T> Clone for ViewHandle<T> {
2471    fn clone(&self) -> Self {
2472        self.ref_counts
2473            .lock()
2474            .inc_view(self.window_id, self.view_id);
2475        Self {
2476            window_id: self.window_id,
2477            view_id: self.view_id,
2478            view_type: PhantomData,
2479            ref_counts: self.ref_counts.clone(),
2480        }
2481    }
2482}
2483
2484impl<T> PartialEq for ViewHandle<T> {
2485    fn eq(&self, other: &Self) -> bool {
2486        self.window_id == other.window_id && self.view_id == other.view_id
2487    }
2488}
2489
2490impl<T> Eq for ViewHandle<T> {}
2491
2492impl<T> Debug for ViewHandle<T> {
2493    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2494        f.debug_struct(&format!("ViewHandle<{}>", type_name::<T>()))
2495            .field("window_id", &self.window_id)
2496            .field("view_id", &self.view_id)
2497            .finish()
2498    }
2499}
2500
2501impl<T> Drop for ViewHandle<T> {
2502    fn drop(&mut self) {
2503        self.ref_counts
2504            .lock()
2505            .dec_view(self.window_id, self.view_id);
2506    }
2507}
2508
2509impl<T> Handle<T> for ViewHandle<T> {
2510    fn id(&self) -> usize {
2511        self.view_id
2512    }
2513
2514    fn location(&self) -> EntityLocation {
2515        EntityLocation::View(self.window_id, self.view_id)
2516    }
2517}
2518
2519pub struct AnyViewHandle {
2520    window_id: usize,
2521    view_id: usize,
2522    view_type: TypeId,
2523    ref_counts: Arc<Mutex<RefCounts>>,
2524}
2525
2526impl AnyViewHandle {
2527    pub fn id(&self) -> usize {
2528        self.view_id
2529    }
2530
2531    pub fn is<T: 'static>(&self) -> bool {
2532        TypeId::of::<T>() == self.view_type
2533    }
2534
2535    pub fn downcast<T: View>(self) -> Option<ViewHandle<T>> {
2536        if self.is::<T>() {
2537            let result = Some(ViewHandle {
2538                window_id: self.window_id,
2539                view_id: self.view_id,
2540                ref_counts: self.ref_counts.clone(),
2541                view_type: PhantomData,
2542            });
2543            unsafe {
2544                Arc::decrement_strong_count(&self.ref_counts);
2545            }
2546            std::mem::forget(self);
2547            result
2548        } else {
2549            None
2550        }
2551    }
2552}
2553
2554impl Clone for AnyViewHandle {
2555    fn clone(&self) -> Self {
2556        self.ref_counts
2557            .lock()
2558            .inc_view(self.window_id, self.view_id);
2559        Self {
2560            window_id: self.window_id,
2561            view_id: self.view_id,
2562            view_type: self.view_type,
2563            ref_counts: self.ref_counts.clone(),
2564        }
2565    }
2566}
2567
2568impl<T: View> From<&ViewHandle<T>> for AnyViewHandle {
2569    fn from(handle: &ViewHandle<T>) -> Self {
2570        handle
2571            .ref_counts
2572            .lock()
2573            .inc_view(handle.window_id, handle.view_id);
2574        AnyViewHandle {
2575            window_id: handle.window_id,
2576            view_id: handle.view_id,
2577            view_type: TypeId::of::<T>(),
2578            ref_counts: handle.ref_counts.clone(),
2579        }
2580    }
2581}
2582
2583impl<T: View> From<ViewHandle<T>> for AnyViewHandle {
2584    fn from(handle: ViewHandle<T>) -> Self {
2585        let any_handle = AnyViewHandle {
2586            window_id: handle.window_id,
2587            view_id: handle.view_id,
2588            view_type: TypeId::of::<T>(),
2589            ref_counts: handle.ref_counts.clone(),
2590        };
2591        unsafe {
2592            Arc::decrement_strong_count(&handle.ref_counts);
2593        }
2594        std::mem::forget(handle);
2595        any_handle
2596    }
2597}
2598
2599impl Drop for AnyViewHandle {
2600    fn drop(&mut self) {
2601        self.ref_counts
2602            .lock()
2603            .dec_view(self.window_id, self.view_id);
2604    }
2605}
2606
2607pub struct AnyModelHandle {
2608    model_id: usize,
2609    ref_counts: Arc<Mutex<RefCounts>>,
2610}
2611
2612impl<T: Entity> From<ModelHandle<T>> for AnyModelHandle {
2613    fn from(handle: ModelHandle<T>) -> Self {
2614        handle.ref_counts.lock().inc_model(handle.model_id);
2615        Self {
2616            model_id: handle.model_id,
2617            ref_counts: handle.ref_counts.clone(),
2618        }
2619    }
2620}
2621
2622impl Drop for AnyModelHandle {
2623    fn drop(&mut self) {
2624        self.ref_counts.lock().dec_model(self.model_id);
2625    }
2626}
2627pub struct WeakViewHandle<T> {
2628    window_id: usize,
2629    view_id: usize,
2630    view_type: PhantomData<T>,
2631}
2632
2633impl<T: View> WeakViewHandle<T> {
2634    fn new(window_id: usize, view_id: usize) -> Self {
2635        Self {
2636            window_id,
2637            view_id,
2638            view_type: PhantomData,
2639        }
2640    }
2641
2642    pub fn upgrade(&self, cx: impl AsRef<AppContext>) -> Option<ViewHandle<T>> {
2643        let cx = cx.as_ref();
2644        if cx.ref_counts.lock().is_entity_alive(self.view_id) {
2645            Some(ViewHandle::new(
2646                self.window_id,
2647                self.view_id,
2648                &cx.ref_counts,
2649            ))
2650        } else {
2651            None
2652        }
2653    }
2654}
2655
2656impl<T> Clone for WeakViewHandle<T> {
2657    fn clone(&self) -> Self {
2658        Self {
2659            window_id: self.window_id,
2660            view_id: self.view_id,
2661            view_type: PhantomData,
2662        }
2663    }
2664}
2665
2666pub struct ValueHandle<T> {
2667    value_type: PhantomData<T>,
2668    tag_type_id: TypeId,
2669    id: usize,
2670    ref_counts: Weak<Mutex<RefCounts>>,
2671}
2672
2673impl<T: 'static> ValueHandle<T> {
2674    fn new(tag_type_id: TypeId, id: usize, ref_counts: &Arc<Mutex<RefCounts>>) -> Self {
2675        ref_counts.lock().inc_value(tag_type_id, id);
2676        Self {
2677            value_type: PhantomData,
2678            tag_type_id,
2679            id,
2680            ref_counts: Arc::downgrade(ref_counts),
2681        }
2682    }
2683
2684    pub fn read<R>(&self, cx: &AppContext, f: impl FnOnce(&T) -> R) -> R {
2685        f(cx.values
2686            .read()
2687            .get(&(self.tag_type_id, self.id))
2688            .unwrap()
2689            .downcast_ref()
2690            .unwrap())
2691    }
2692
2693    pub fn update<R>(&self, cx: &AppContext, f: impl FnOnce(&mut T) -> R) -> R {
2694        f(cx.values
2695            .write()
2696            .get_mut(&(self.tag_type_id, self.id))
2697            .unwrap()
2698            .downcast_mut()
2699            .unwrap())
2700    }
2701}
2702
2703impl<T> Drop for ValueHandle<T> {
2704    fn drop(&mut self) {
2705        if let Some(ref_counts) = self.ref_counts.upgrade() {
2706            ref_counts.lock().dec_value(self.tag_type_id, self.id);
2707        }
2708    }
2709}
2710
2711#[derive(Default)]
2712struct RefCounts {
2713    entity_counts: HashMap<usize, usize>,
2714    value_counts: HashMap<(TypeId, usize), usize>,
2715    dropped_models: HashSet<usize>,
2716    dropped_views: HashSet<(usize, usize)>,
2717    dropped_values: HashSet<(TypeId, usize)>,
2718}
2719
2720impl RefCounts {
2721    fn inc_model(&mut self, model_id: usize) {
2722        match self.entity_counts.entry(model_id) {
2723            Entry::Occupied(mut entry) => *entry.get_mut() += 1,
2724            Entry::Vacant(entry) => {
2725                entry.insert(1);
2726                self.dropped_models.remove(&model_id);
2727            }
2728        }
2729    }
2730
2731    fn inc_view(&mut self, window_id: usize, view_id: usize) {
2732        match self.entity_counts.entry(view_id) {
2733            Entry::Occupied(mut entry) => *entry.get_mut() += 1,
2734            Entry::Vacant(entry) => {
2735                entry.insert(1);
2736                self.dropped_views.remove(&(window_id, view_id));
2737            }
2738        }
2739    }
2740
2741    fn inc_value(&mut self, tag_type_id: TypeId, id: usize) {
2742        *self.value_counts.entry((tag_type_id, id)).or_insert(0) += 1;
2743    }
2744
2745    fn dec_model(&mut self, model_id: usize) {
2746        let count = self.entity_counts.get_mut(&model_id).unwrap();
2747        *count -= 1;
2748        if *count == 0 {
2749            self.entity_counts.remove(&model_id);
2750            self.dropped_models.insert(model_id);
2751        }
2752    }
2753
2754    fn dec_view(&mut self, window_id: usize, view_id: usize) {
2755        let count = self.entity_counts.get_mut(&view_id).unwrap();
2756        *count -= 1;
2757        if *count == 0 {
2758            self.entity_counts.remove(&view_id);
2759            self.dropped_views.insert((window_id, view_id));
2760        }
2761    }
2762
2763    fn dec_value(&mut self, tag_type_id: TypeId, id: usize) {
2764        let key = (tag_type_id, id);
2765        let count = self.value_counts.get_mut(&key).unwrap();
2766        *count -= 1;
2767        if *count == 0 {
2768            self.value_counts.remove(&key);
2769            self.dropped_values.insert(key);
2770        }
2771    }
2772
2773    fn is_entity_alive(&self, entity_id: usize) -> bool {
2774        self.entity_counts.contains_key(&entity_id)
2775    }
2776
2777    fn take_dropped(
2778        &mut self,
2779    ) -> (
2780        HashSet<usize>,
2781        HashSet<(usize, usize)>,
2782        HashSet<(TypeId, usize)>,
2783    ) {
2784        let mut dropped_models = HashSet::new();
2785        let mut dropped_views = HashSet::new();
2786        let mut dropped_values = HashSet::new();
2787        std::mem::swap(&mut self.dropped_models, &mut dropped_models);
2788        std::mem::swap(&mut self.dropped_views, &mut dropped_views);
2789        std::mem::swap(&mut self.dropped_values, &mut dropped_values);
2790        (dropped_models, dropped_views, dropped_values)
2791    }
2792}
2793
2794enum Subscription {
2795    FromModel {
2796        model_id: usize,
2797        callback: Box<dyn FnMut(&mut dyn Any, &dyn Any, &mut MutableAppContext, usize)>,
2798    },
2799    FromView {
2800        window_id: usize,
2801        view_id: usize,
2802        callback: Box<dyn FnMut(&mut dyn Any, &dyn Any, &mut MutableAppContext, usize, usize)>,
2803    },
2804}
2805
2806enum ModelObservation {
2807    FromModel {
2808        model_id: usize,
2809        callback: Box<dyn FnMut(&mut dyn Any, usize, &mut MutableAppContext, usize)>,
2810    },
2811    FromView {
2812        window_id: usize,
2813        view_id: usize,
2814        callback: Box<dyn FnMut(&mut dyn Any, usize, &mut MutableAppContext, usize, usize)>,
2815    },
2816}
2817
2818struct ViewObservation {
2819    window_id: usize,
2820    view_id: usize,
2821    callback: Box<dyn FnMut(&mut dyn Any, usize, usize, &mut MutableAppContext, usize, usize)>,
2822}
2823
2824#[cfg(test)]
2825mod tests {
2826    use super::*;
2827    use crate::elements::*;
2828    use smol::future::poll_once;
2829    use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
2830
2831    #[crate::test(self)]
2832    fn test_model_handles(cx: &mut MutableAppContext) {
2833        struct Model {
2834            other: Option<ModelHandle<Model>>,
2835            events: Vec<String>,
2836        }
2837
2838        impl Entity for Model {
2839            type Event = usize;
2840        }
2841
2842        impl Model {
2843            fn new(other: Option<ModelHandle<Self>>, cx: &mut ModelContext<Self>) -> Self {
2844                if let Some(other) = other.as_ref() {
2845                    cx.observe(other, |me, _, _| {
2846                        me.events.push("notified".into());
2847                    });
2848                    cx.subscribe(other, |me, event, _| {
2849                        me.events.push(format!("observed event {}", event));
2850                    });
2851                }
2852
2853                Self {
2854                    other,
2855                    events: Vec::new(),
2856                }
2857            }
2858        }
2859
2860        let handle_1 = cx.add_model(|cx| Model::new(None, cx));
2861        let handle_2 = cx.add_model(|cx| Model::new(Some(handle_1.clone()), cx));
2862        assert_eq!(cx.cx.models.len(), 2);
2863
2864        handle_1.update(cx, |model, cx| {
2865            model.events.push("updated".into());
2866            cx.emit(1);
2867            cx.notify();
2868            cx.emit(2);
2869        });
2870        assert_eq!(handle_1.read(cx).events, vec!["updated".to_string()]);
2871        assert_eq!(
2872            handle_2.read(cx).events,
2873            vec![
2874                "observed event 1".to_string(),
2875                "notified".to_string(),
2876                "observed event 2".to_string(),
2877            ]
2878        );
2879
2880        handle_2.update(cx, |model, _| {
2881            drop(handle_1);
2882            model.other.take();
2883        });
2884
2885        assert_eq!(cx.cx.models.len(), 1);
2886        assert!(cx.subscriptions.is_empty());
2887        assert!(cx.model_observations.is_empty());
2888    }
2889
2890    #[crate::test(self)]
2891    fn test_subscribe_and_emit_from_model(cx: &mut MutableAppContext) {
2892        #[derive(Default)]
2893        struct Model {
2894            events: Vec<usize>,
2895        }
2896
2897        impl Entity for Model {
2898            type Event = usize;
2899        }
2900
2901        let handle_1 = cx.add_model(|_| Model::default());
2902        let handle_2 = cx.add_model(|_| Model::default());
2903        let handle_2b = handle_2.clone();
2904
2905        handle_1.update(cx, |_, c| {
2906            c.subscribe(&handle_2, move |model: &mut Model, event, c| {
2907                model.events.push(*event);
2908
2909                c.subscribe(&handle_2b, |model, event, _| {
2910                    model.events.push(*event * 2);
2911                });
2912            });
2913        });
2914
2915        handle_2.update(cx, |_, c| c.emit(7));
2916        assert_eq!(handle_1.read(cx).events, vec![7]);
2917
2918        handle_2.update(cx, |_, c| c.emit(5));
2919        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5]);
2920    }
2921
2922    #[crate::test(self)]
2923    fn test_observe_and_notify_from_model(cx: &mut MutableAppContext) {
2924        #[derive(Default)]
2925        struct Model {
2926            count: usize,
2927            events: Vec<usize>,
2928        }
2929
2930        impl Entity for Model {
2931            type Event = ();
2932        }
2933
2934        let handle_1 = cx.add_model(|_| Model::default());
2935        let handle_2 = cx.add_model(|_| Model::default());
2936        let handle_2b = handle_2.clone();
2937
2938        handle_1.update(cx, |_, c| {
2939            c.observe(&handle_2, move |model, observed, c| {
2940                model.events.push(observed.read(c).count);
2941                c.observe(&handle_2b, |model, observed, c| {
2942                    model.events.push(observed.read(c).count * 2);
2943                });
2944            });
2945        });
2946
2947        handle_2.update(cx, |model, c| {
2948            model.count = 7;
2949            c.notify()
2950        });
2951        assert_eq!(handle_1.read(cx).events, vec![7]);
2952
2953        handle_2.update(cx, |model, c| {
2954            model.count = 5;
2955            c.notify()
2956        });
2957        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5])
2958    }
2959
2960    #[crate::test(self)]
2961    fn test_view_handles(cx: &mut MutableAppContext) {
2962        struct View {
2963            other: Option<ViewHandle<View>>,
2964            events: Vec<String>,
2965        }
2966
2967        impl Entity for View {
2968            type Event = usize;
2969        }
2970
2971        impl super::View for View {
2972            fn render<'a>(&self, _: &AppContext) -> ElementBox {
2973                Empty::new().boxed()
2974            }
2975
2976            fn ui_name() -> &'static str {
2977                "View"
2978            }
2979        }
2980
2981        impl View {
2982            fn new(other: Option<ViewHandle<View>>, cx: &mut ViewContext<Self>) -> Self {
2983                if let Some(other) = other.as_ref() {
2984                    cx.subscribe_to_view(other, |me, _, event, _| {
2985                        me.events.push(format!("observed event {}", event));
2986                    });
2987                }
2988                Self {
2989                    other,
2990                    events: Vec::new(),
2991                }
2992            }
2993        }
2994
2995        let (window_id, _) = cx.add_window(|cx| View::new(None, cx));
2996        let handle_1 = cx.add_view(window_id, |cx| View::new(None, cx));
2997        let handle_2 = cx.add_view(window_id, |cx| View::new(Some(handle_1.clone()), cx));
2998        assert_eq!(cx.cx.views.len(), 3);
2999
3000        handle_1.update(cx, |view, cx| {
3001            view.events.push("updated".into());
3002            cx.emit(1);
3003            cx.emit(2);
3004        });
3005        assert_eq!(handle_1.read(cx).events, vec!["updated".to_string()]);
3006        assert_eq!(
3007            handle_2.read(cx).events,
3008            vec![
3009                "observed event 1".to_string(),
3010                "observed event 2".to_string(),
3011            ]
3012        );
3013
3014        handle_2.update(cx, |view, _| {
3015            drop(handle_1);
3016            view.other.take();
3017        });
3018
3019        assert_eq!(cx.cx.views.len(), 2);
3020        assert!(cx.subscriptions.is_empty());
3021        assert!(cx.model_observations.is_empty());
3022    }
3023
3024    #[crate::test(self)]
3025    fn test_add_window(cx: &mut MutableAppContext) {
3026        struct View {
3027            mouse_down_count: Arc<AtomicUsize>,
3028        }
3029
3030        impl Entity for View {
3031            type Event = ();
3032        }
3033
3034        impl super::View for View {
3035            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3036                let mouse_down_count = self.mouse_down_count.clone();
3037                EventHandler::new(Empty::new().boxed())
3038                    .on_mouse_down(move |_| {
3039                        mouse_down_count.fetch_add(1, SeqCst);
3040                        true
3041                    })
3042                    .boxed()
3043            }
3044
3045            fn ui_name() -> &'static str {
3046                "View"
3047            }
3048        }
3049
3050        let mouse_down_count = Arc::new(AtomicUsize::new(0));
3051        let (window_id, _) = cx.add_window(|_| View {
3052            mouse_down_count: mouse_down_count.clone(),
3053        });
3054        let presenter = cx.presenters_and_platform_windows[&window_id].0.clone();
3055        // Ensure window's root element is in a valid lifecycle state.
3056        presenter.borrow_mut().dispatch_event(
3057            Event::LeftMouseDown {
3058                position: Default::default(),
3059                cmd: false,
3060            },
3061            cx,
3062        );
3063        assert_eq!(mouse_down_count.load(SeqCst), 1);
3064    }
3065
3066    #[crate::test(self)]
3067    fn test_entity_release_hooks(cx: &mut MutableAppContext) {
3068        struct Model {
3069            released: Arc<Mutex<bool>>,
3070        }
3071
3072        struct View {
3073            released: Arc<Mutex<bool>>,
3074        }
3075
3076        impl Entity for Model {
3077            type Event = ();
3078
3079            fn release(&mut self, _: &mut MutableAppContext) {
3080                *self.released.lock() = true;
3081            }
3082        }
3083
3084        impl Entity for View {
3085            type Event = ();
3086
3087            fn release(&mut self, _: &mut MutableAppContext) {
3088                *self.released.lock() = true;
3089            }
3090        }
3091
3092        impl super::View for View {
3093            fn ui_name() -> &'static str {
3094                "View"
3095            }
3096
3097            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3098                Empty::new().boxed()
3099            }
3100        }
3101
3102        let model_released = Arc::new(Mutex::new(false));
3103        let view_released = Arc::new(Mutex::new(false));
3104
3105        let model = cx.add_model(|_| Model {
3106            released: model_released.clone(),
3107        });
3108
3109        let (window_id, _) = cx.add_window(|_| View {
3110            released: view_released.clone(),
3111        });
3112
3113        assert!(!*model_released.lock());
3114        assert!(!*view_released.lock());
3115
3116        cx.update(move || {
3117            drop(model);
3118        });
3119        assert!(*model_released.lock());
3120
3121        drop(cx.remove_window(window_id));
3122        assert!(*view_released.lock());
3123    }
3124
3125    #[crate::test(self)]
3126    fn test_subscribe_and_emit_from_view(cx: &mut MutableAppContext) {
3127        #[derive(Default)]
3128        struct View {
3129            events: Vec<usize>,
3130        }
3131
3132        impl Entity for View {
3133            type Event = usize;
3134        }
3135
3136        impl super::View for View {
3137            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3138                Empty::new().boxed()
3139            }
3140
3141            fn ui_name() -> &'static str {
3142                "View"
3143            }
3144        }
3145
3146        struct Model;
3147
3148        impl Entity for Model {
3149            type Event = usize;
3150        }
3151
3152        let (window_id, handle_1) = cx.add_window(|_| View::default());
3153        let handle_2 = cx.add_view(window_id, |_| View::default());
3154        let handle_2b = handle_2.clone();
3155        let handle_3 = cx.add_model(|_| Model);
3156
3157        handle_1.update(cx, |_, c| {
3158            c.subscribe_to_view(&handle_2, move |me, _, event, c| {
3159                me.events.push(*event);
3160
3161                c.subscribe_to_view(&handle_2b, |me, _, event, _| {
3162                    me.events.push(*event * 2);
3163                });
3164            });
3165
3166            c.subscribe_to_model(&handle_3, |me, _, event, _| {
3167                me.events.push(*event);
3168            })
3169        });
3170
3171        handle_2.update(cx, |_, c| c.emit(7));
3172        assert_eq!(handle_1.read(cx).events, vec![7]);
3173
3174        handle_2.update(cx, |_, c| c.emit(5));
3175        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5]);
3176
3177        handle_3.update(cx, |_, c| c.emit(9));
3178        assert_eq!(handle_1.read(cx).events, vec![7, 10, 5, 9]);
3179    }
3180
3181    #[crate::test(self)]
3182    fn test_dropping_subscribers(cx: &mut MutableAppContext) {
3183        struct View;
3184
3185        impl Entity for View {
3186            type Event = ();
3187        }
3188
3189        impl super::View for View {
3190            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3191                Empty::new().boxed()
3192            }
3193
3194            fn ui_name() -> &'static str {
3195                "View"
3196            }
3197        }
3198
3199        struct Model;
3200
3201        impl Entity for Model {
3202            type Event = ();
3203        }
3204
3205        let (window_id, _) = cx.add_window(|_| View);
3206        let observing_view = cx.add_view(window_id, |_| View);
3207        let emitting_view = cx.add_view(window_id, |_| View);
3208        let observing_model = cx.add_model(|_| Model);
3209        let observed_model = cx.add_model(|_| Model);
3210
3211        observing_view.update(cx, |_, cx| {
3212            cx.subscribe_to_view(&emitting_view, |_, _, _, _| {});
3213            cx.subscribe_to_model(&observed_model, |_, _, _, _| {});
3214        });
3215        observing_model.update(cx, |_, cx| {
3216            cx.subscribe(&observed_model, |_, _, _| {});
3217        });
3218
3219        cx.update(|| {
3220            drop(observing_view);
3221            drop(observing_model);
3222        });
3223
3224        emitting_view.update(cx, |_, cx| cx.emit(()));
3225        observed_model.update(cx, |_, cx| cx.emit(()));
3226    }
3227
3228    #[crate::test(self)]
3229    fn test_observe_and_notify_from_view(cx: &mut MutableAppContext) {
3230        #[derive(Default)]
3231        struct View {
3232            events: Vec<usize>,
3233        }
3234
3235        impl Entity for View {
3236            type Event = usize;
3237        }
3238
3239        impl super::View for View {
3240            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3241                Empty::new().boxed()
3242            }
3243
3244            fn ui_name() -> &'static str {
3245                "View"
3246            }
3247        }
3248
3249        #[derive(Default)]
3250        struct Model {
3251            count: usize,
3252        }
3253
3254        impl Entity for Model {
3255            type Event = ();
3256        }
3257
3258        let (_, view) = cx.add_window(|_| View::default());
3259        let model = cx.add_model(|_| Model::default());
3260
3261        view.update(cx, |_, c| {
3262            c.observe_model(&model, |me, observed, c| {
3263                me.events.push(observed.read(c).count)
3264            });
3265        });
3266
3267        model.update(cx, |model, c| {
3268            model.count = 11;
3269            c.notify();
3270        });
3271        assert_eq!(view.read(cx).events, vec![11]);
3272    }
3273
3274    #[crate::test(self)]
3275    fn test_dropping_observers(cx: &mut MutableAppContext) {
3276        struct View;
3277
3278        impl Entity for View {
3279            type Event = ();
3280        }
3281
3282        impl super::View for View {
3283            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3284                Empty::new().boxed()
3285            }
3286
3287            fn ui_name() -> &'static str {
3288                "View"
3289            }
3290        }
3291
3292        struct Model;
3293
3294        impl Entity for Model {
3295            type Event = ();
3296        }
3297
3298        let (window_id, _) = cx.add_window(|_| View);
3299        let observing_view = cx.add_view(window_id, |_| View);
3300        let observing_model = cx.add_model(|_| Model);
3301        let observed_model = cx.add_model(|_| Model);
3302
3303        observing_view.update(cx, |_, cx| {
3304            cx.observe_model(&observed_model, |_, _, _| {});
3305        });
3306        observing_model.update(cx, |_, cx| {
3307            cx.observe(&observed_model, |_, _, _| {});
3308        });
3309
3310        cx.update(|| {
3311            drop(observing_view);
3312            drop(observing_model);
3313        });
3314
3315        observed_model.update(cx, |_, cx| cx.notify());
3316    }
3317
3318    #[crate::test(self)]
3319    fn test_focus(cx: &mut MutableAppContext) {
3320        struct View {
3321            name: String,
3322            events: Arc<Mutex<Vec<String>>>,
3323        }
3324
3325        impl Entity for View {
3326            type Event = ();
3327        }
3328
3329        impl super::View for View {
3330            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3331                Empty::new().boxed()
3332            }
3333
3334            fn ui_name() -> &'static str {
3335                "View"
3336            }
3337
3338            fn on_focus(&mut self, _: &mut ViewContext<Self>) {
3339                self.events.lock().push(format!("{} focused", &self.name));
3340            }
3341
3342            fn on_blur(&mut self, _: &mut ViewContext<Self>) {
3343                self.events.lock().push(format!("{} blurred", &self.name));
3344            }
3345        }
3346
3347        let events: Arc<Mutex<Vec<String>>> = Default::default();
3348        let (window_id, view_1) = cx.add_window(|_| View {
3349            events: events.clone(),
3350            name: "view 1".to_string(),
3351        });
3352        let view_2 = cx.add_view(window_id, |_| View {
3353            events: events.clone(),
3354            name: "view 2".to_string(),
3355        });
3356
3357        view_1.update(cx, |_, cx| cx.focus(&view_2));
3358        view_1.update(cx, |_, cx| cx.focus(&view_1));
3359        view_1.update(cx, |_, cx| cx.focus(&view_2));
3360        view_1.update(cx, |_, _| drop(view_2));
3361
3362        assert_eq!(
3363            *events.lock(),
3364            [
3365                "view 1 focused".to_string(),
3366                "view 1 blurred".to_string(),
3367                "view 2 focused".to_string(),
3368                "view 2 blurred".to_string(),
3369                "view 1 focused".to_string(),
3370                "view 1 blurred".to_string(),
3371                "view 2 focused".to_string(),
3372                "view 1 focused".to_string(),
3373            ],
3374        );
3375    }
3376
3377    #[crate::test(self)]
3378    fn test_dispatch_action(cx: &mut MutableAppContext) {
3379        struct ViewA {
3380            id: usize,
3381        }
3382
3383        impl Entity for ViewA {
3384            type Event = ();
3385        }
3386
3387        impl View for ViewA {
3388            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3389                Empty::new().boxed()
3390            }
3391
3392            fn ui_name() -> &'static str {
3393                "View"
3394            }
3395        }
3396
3397        struct ViewB {
3398            id: usize,
3399        }
3400
3401        impl Entity for ViewB {
3402            type Event = ();
3403        }
3404
3405        impl View for ViewB {
3406            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3407                Empty::new().boxed()
3408            }
3409
3410            fn ui_name() -> &'static str {
3411                "View"
3412            }
3413        }
3414
3415        struct ActionArg {
3416            foo: String,
3417        }
3418
3419        let actions = Rc::new(RefCell::new(Vec::new()));
3420
3421        let actions_clone = actions.clone();
3422        cx.add_global_action("action", move |_: &ActionArg, _: &mut MutableAppContext| {
3423            actions_clone.borrow_mut().push("global a".to_string());
3424        });
3425
3426        let actions_clone = actions.clone();
3427        cx.add_global_action("action", move |_: &ActionArg, _: &mut MutableAppContext| {
3428            actions_clone.borrow_mut().push("global b".to_string());
3429        });
3430
3431        let actions_clone = actions.clone();
3432        cx.add_action("action", move |view: &mut ViewA, arg: &ActionArg, cx| {
3433            assert_eq!(arg.foo, "bar");
3434            cx.propagate_action();
3435            actions_clone.borrow_mut().push(format!("{} a", view.id));
3436        });
3437
3438        let actions_clone = actions.clone();
3439        cx.add_action("action", move |view: &mut ViewA, _: &ActionArg, cx| {
3440            if view.id != 1 {
3441                cx.propagate_action();
3442            }
3443            actions_clone.borrow_mut().push(format!("{} b", 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!("{} c", view.id));
3450        });
3451
3452        let actions_clone = actions.clone();
3453        cx.add_action("action", move |view: &mut ViewB, _: &ActionArg, cx| {
3454            cx.propagate_action();
3455            actions_clone.borrow_mut().push(format!("{} d", view.id));
3456        });
3457
3458        let (window_id, view_1) = cx.add_window(|_| ViewA { id: 1 });
3459        let view_2 = cx.add_view(window_id, |_| ViewB { id: 2 });
3460        let view_3 = cx.add_view(window_id, |_| ViewA { id: 3 });
3461        let view_4 = cx.add_view(window_id, |_| ViewB { id: 4 });
3462
3463        cx.dispatch_action(
3464            window_id,
3465            vec![view_1.id(), view_2.id(), view_3.id(), view_4.id()],
3466            "action",
3467            ActionArg { foo: "bar".into() },
3468        );
3469
3470        assert_eq!(
3471            *actions.borrow(),
3472            vec!["4 d", "4 c", "3 b", "3 a", "2 d", "2 c", "1 b"]
3473        );
3474
3475        // Remove view_1, which doesn't propagate the action
3476        actions.borrow_mut().clear();
3477        cx.dispatch_action(
3478            window_id,
3479            vec![view_2.id(), view_3.id(), view_4.id()],
3480            "action",
3481            ActionArg { foo: "bar".into() },
3482        );
3483
3484        assert_eq!(
3485            *actions.borrow(),
3486            vec!["4 d", "4 c", "3 b", "3 a", "2 d", "2 c", "global b", "global a"]
3487        );
3488    }
3489
3490    #[crate::test(self)]
3491    fn test_dispatch_keystroke(cx: &mut MutableAppContext) {
3492        use std::cell::Cell;
3493
3494        #[derive(Clone)]
3495        struct ActionArg {
3496            key: String,
3497        }
3498
3499        struct View {
3500            id: usize,
3501            keymap_context: keymap::Context,
3502        }
3503
3504        impl Entity for View {
3505            type Event = ();
3506        }
3507
3508        impl super::View for View {
3509            fn render<'a>(&self, _: &AppContext) -> ElementBox {
3510                Empty::new().boxed()
3511            }
3512
3513            fn ui_name() -> &'static str {
3514                "View"
3515            }
3516
3517            fn keymap_context(&self, _: &AppContext) -> keymap::Context {
3518                self.keymap_context.clone()
3519            }
3520        }
3521
3522        impl View {
3523            fn new(id: usize) -> Self {
3524                View {
3525                    id,
3526                    keymap_context: keymap::Context::default(),
3527                }
3528            }
3529        }
3530
3531        let mut view_1 = View::new(1);
3532        let mut view_2 = View::new(2);
3533        let mut view_3 = View::new(3);
3534        view_1.keymap_context.set.insert("a".into());
3535        view_2.keymap_context.set.insert("b".into());
3536        view_3.keymap_context.set.insert("c".into());
3537
3538        let (window_id, view_1) = cx.add_window(|_| view_1);
3539        let view_2 = cx.add_view(window_id, |_| view_2);
3540        let view_3 = cx.add_view(window_id, |_| view_3);
3541
3542        // This keymap's only binding dispatches an action on view 2 because that view will have
3543        // "a" and "b" in its context, but not "c".
3544        let binding = keymap::Binding::new("a", "action", Some("a && b && !c"))
3545            .with_arg(ActionArg { key: "a".into() });
3546        cx.add_bindings(vec![binding]);
3547
3548        let handled_action = Rc::new(Cell::new(false));
3549        let handled_action_clone = handled_action.clone();
3550        cx.add_action("action", move |view: &mut View, arg: &ActionArg, _| {
3551            handled_action_clone.set(true);
3552            assert_eq!(view.id, 2);
3553            assert_eq!(arg.key, "a");
3554        });
3555
3556        cx.dispatch_keystroke(
3557            window_id,
3558            vec![view_1.id(), view_2.id(), view_3.id()],
3559            &Keystroke::parse("a").unwrap(),
3560        )
3561        .unwrap();
3562
3563        assert!(handled_action.get());
3564    }
3565
3566    #[crate::test(self)]
3567    async fn test_model_condition(mut cx: TestAppContext) {
3568        struct Counter(usize);
3569
3570        impl super::Entity for Counter {
3571            type Event = ();
3572        }
3573
3574        impl Counter {
3575            fn inc(&mut self, cx: &mut ModelContext<Self>) {
3576                self.0 += 1;
3577                cx.notify();
3578            }
3579        }
3580
3581        let model = cx.add_model(|_| Counter(0));
3582
3583        let condition1 = model.condition(&cx, |model, _| model.0 == 2);
3584        let condition2 = model.condition(&cx, |model, _| model.0 == 3);
3585        smol::pin!(condition1, condition2);
3586
3587        model.update(&mut cx, |model, cx| model.inc(cx));
3588        assert_eq!(poll_once(&mut condition1).await, None);
3589        assert_eq!(poll_once(&mut condition2).await, None);
3590
3591        model.update(&mut cx, |model, cx| model.inc(cx));
3592        assert_eq!(poll_once(&mut condition1).await, Some(()));
3593        assert_eq!(poll_once(&mut condition2).await, None);
3594
3595        model.update(&mut cx, |model, cx| model.inc(cx));
3596        assert_eq!(poll_once(&mut condition2).await, Some(()));
3597
3598        model.update(&mut cx, |_, cx| cx.notify());
3599    }
3600
3601    #[crate::test(self)]
3602    #[should_panic]
3603    async fn test_model_condition_timeout(mut cx: TestAppContext) {
3604        struct Model;
3605
3606        impl super::Entity for Model {
3607            type Event = ();
3608        }
3609
3610        let model = cx.add_model(|_| Model);
3611        model.condition(&cx, |_, _| false).await;
3612    }
3613
3614    #[crate::test(self)]
3615    #[should_panic(expected = "model dropped with pending condition")]
3616    async fn test_model_condition_panic_on_drop(mut cx: TestAppContext) {
3617        struct Model;
3618
3619        impl super::Entity for Model {
3620            type Event = ();
3621        }
3622
3623        let model = cx.add_model(|_| Model);
3624        let condition = model.condition(&cx, |_, _| false);
3625        cx.update(|_| drop(model));
3626        condition.await;
3627    }
3628
3629    #[crate::test(self)]
3630    async fn test_view_condition(mut cx: TestAppContext) {
3631        struct Counter(usize);
3632
3633        impl super::Entity for Counter {
3634            type Event = ();
3635        }
3636
3637        impl super::View for Counter {
3638            fn ui_name() -> &'static str {
3639                "test view"
3640            }
3641
3642            fn render(&self, _: &AppContext) -> ElementBox {
3643                Empty::new().boxed()
3644            }
3645        }
3646
3647        impl Counter {
3648            fn inc(&mut self, cx: &mut ViewContext<Self>) {
3649                self.0 += 1;
3650                cx.notify();
3651            }
3652        }
3653
3654        let (_, view) = cx.add_window(|_| Counter(0));
3655
3656        let condition1 = view.condition(&cx, |view, _| view.0 == 2);
3657        let condition2 = view.condition(&cx, |view, _| view.0 == 3);
3658        smol::pin!(condition1, condition2);
3659
3660        view.update(&mut cx, |view, cx| view.inc(cx));
3661        assert_eq!(poll_once(&mut condition1).await, None);
3662        assert_eq!(poll_once(&mut condition2).await, None);
3663
3664        view.update(&mut cx, |view, cx| view.inc(cx));
3665        assert_eq!(poll_once(&mut condition1).await, Some(()));
3666        assert_eq!(poll_once(&mut condition2).await, None);
3667
3668        view.update(&mut cx, |view, cx| view.inc(cx));
3669        assert_eq!(poll_once(&mut condition2).await, Some(()));
3670        view.update(&mut cx, |_, cx| cx.notify());
3671    }
3672
3673    #[crate::test(self)]
3674    #[should_panic]
3675    async fn test_view_condition_timeout(mut cx: TestAppContext) {
3676        struct View;
3677
3678        impl super::Entity for View {
3679            type Event = ();
3680        }
3681
3682        impl super::View for View {
3683            fn ui_name() -> &'static str {
3684                "test view"
3685            }
3686
3687            fn render(&self, _: &AppContext) -> ElementBox {
3688                Empty::new().boxed()
3689            }
3690        }
3691
3692        let (_, view) = cx.add_window(|_| View);
3693        view.condition(&cx, |_, _| false).await;
3694    }
3695
3696    #[crate::test(self)]
3697    #[should_panic(expected = "view dropped with pending condition")]
3698    async fn test_view_condition_panic_on_drop(mut cx: TestAppContext) {
3699        struct View;
3700
3701        impl super::Entity for View {
3702            type Event = ();
3703        }
3704
3705        impl super::View for View {
3706            fn ui_name() -> &'static str {
3707                "test view"
3708            }
3709
3710            fn render(&self, _: &AppContext) -> ElementBox {
3711                Empty::new().boxed()
3712            }
3713        }
3714
3715        let window_id = cx.add_window(|_| View).0;
3716        let view = cx.add_view(window_id, |_| View);
3717
3718        let condition = view.condition(&cx, |_, _| false);
3719        cx.update(|_| drop(view));
3720        condition.await;
3721    }
3722}