app.rs

   1use std::{
   2    any::{type_name, TypeId},
   3    cell::{Ref, RefCell, RefMut},
   4    marker::PhantomData,
   5    ops::{Deref, DerefMut},
   6    path::{Path, PathBuf},
   7    rc::{Rc, Weak},
   8    sync::{atomic::Ordering::SeqCst, Arc},
   9    time::Duration,
  10};
  11
  12use anyhow::{anyhow, Result};
  13use derive_more::{Deref, DerefMut};
  14use futures::{
  15    channel::oneshot,
  16    future::{LocalBoxFuture, Shared},
  17    Future, FutureExt,
  18};
  19use slotmap::SlotMap;
  20
  21pub use async_context::*;
  22use collections::{FxHashMap, FxHashSet, VecDeque};
  23pub use entity_map::*;
  24use http_client::HttpClient;
  25pub use model_context::*;
  26#[cfg(any(test, feature = "test-support"))]
  27pub use test_context::*;
  28use util::ResultExt;
  29
  30use crate::{
  31    current_platform, hash, init_app_menus, Action, ActionRegistry, Any, AnyView, AnyWindowHandle,
  32    Asset, AssetSource, BackgroundExecutor, ClipboardItem, Context, DispatchPhase, DisplayId,
  33    Entity, EventEmitter, ForegroundExecutor, Global, KeyBinding, Keymap, Keystroke, LayoutId,
  34    Menu, MenuItem, OwnedMenu, PathPromptOptions, Pixels, Platform, PlatformDisplay, Point,
  35    PromptBuilder, PromptHandle, PromptLevel, Render, RenderablePromptHandle, Reservation,
  36    SharedString, SubscriberSet, Subscription, SvgRenderer, Task, TextSystem, View, ViewContext,
  37    Window, WindowAppearance, WindowContext, WindowHandle, WindowId,
  38};
  39
  40mod async_context;
  41mod entity_map;
  42mod model_context;
  43#[cfg(any(test, feature = "test-support"))]
  44mod test_context;
  45
  46/// The duration for which futures returned from [AppContext::on_app_context] or [ModelContext::on_app_quit] can run before the application fully quits.
  47pub const SHUTDOWN_TIMEOUT: Duration = Duration::from_millis(100);
  48
  49/// Temporary(?) wrapper around [`RefCell<AppContext>`] to help us debug any double borrows.
  50/// Strongly consider removing after stabilization.
  51#[doc(hidden)]
  52pub struct AppCell {
  53    app: RefCell<AppContext>,
  54}
  55
  56impl AppCell {
  57    #[doc(hidden)]
  58    #[track_caller]
  59    pub fn borrow(&self) -> AppRef {
  60        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  61            let thread_id = std::thread::current().id();
  62            eprintln!("borrowed {thread_id:?}");
  63        }
  64        AppRef(self.app.borrow())
  65    }
  66
  67    #[doc(hidden)]
  68    #[track_caller]
  69    pub fn borrow_mut(&self) -> AppRefMut {
  70        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  71            let thread_id = std::thread::current().id();
  72            eprintln!("borrowed {thread_id:?}");
  73        }
  74        AppRefMut(self.app.borrow_mut())
  75    }
  76}
  77
  78#[doc(hidden)]
  79#[derive(Deref, DerefMut)]
  80pub struct AppRef<'a>(Ref<'a, AppContext>);
  81
  82impl<'a> Drop for AppRef<'a> {
  83    fn drop(&mut self) {
  84        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  85            let thread_id = std::thread::current().id();
  86            eprintln!("dropped borrow from {thread_id:?}");
  87        }
  88    }
  89}
  90
  91#[doc(hidden)]
  92#[derive(Deref, DerefMut)]
  93pub struct AppRefMut<'a>(RefMut<'a, AppContext>);
  94
  95impl<'a> Drop for AppRefMut<'a> {
  96    fn drop(&mut self) {
  97        if option_env!("TRACK_THREAD_BORROWS").is_some() {
  98            let thread_id = std::thread::current().id();
  99            eprintln!("dropped {thread_id:?}");
 100        }
 101    }
 102}
 103
 104/// A reference to a GPUI application, typically constructed in the `main` function of your app.
 105/// You won't interact with this type much outside of initial configuration and startup.
 106pub struct App(Rc<AppCell>);
 107
 108/// Represents an application before it is fully launched. Once your app is
 109/// configured, you'll start the app with `App::run`.
 110impl App {
 111    /// Builds an app with the given asset source.
 112    #[allow(clippy::new_without_default)]
 113    pub fn new() -> Self {
 114        #[cfg(any(test, feature = "test-support"))]
 115        log::info!("GPUI was compiled in test mode");
 116
 117        Self(AppContext::new(
 118            current_platform(false),
 119            Arc::new(()),
 120            http_client::client(None, None),
 121        ))
 122    }
 123
 124    /// Build an app in headless mode. This prevents opening windows,
 125    /// but makes it possible to run an application in an context like
 126    /// SSH, where GUI applications are not allowed.
 127    pub fn headless() -> Self {
 128        Self(AppContext::new(
 129            current_platform(true),
 130            Arc::new(()),
 131            http_client::client(None, None),
 132        ))
 133    }
 134
 135    /// Assign
 136    pub fn with_assets(self, asset_source: impl AssetSource) -> Self {
 137        let mut context_lock = self.0.borrow_mut();
 138        let asset_source = Arc::new(asset_source);
 139        context_lock.asset_source = asset_source.clone();
 140        context_lock.svg_renderer = SvgRenderer::new(asset_source);
 141        drop(context_lock);
 142        self
 143    }
 144
 145    /// Start the application. The provided callback will be called once the
 146    /// app is fully launched.
 147    pub fn run<F>(self, on_finish_launching: F)
 148    where
 149        F: 'static + FnOnce(&mut AppContext),
 150    {
 151        let this = self.0.clone();
 152        let platform = self.0.borrow().platform.clone();
 153        platform.run(Box::new(move || {
 154            let cx = &mut *this.borrow_mut();
 155            on_finish_launching(cx);
 156        }));
 157    }
 158
 159    /// Register a handler to be invoked when the platform instructs the application
 160    /// to open one or more URLs.
 161    pub fn on_open_urls<F>(&self, mut callback: F) -> &Self
 162    where
 163        F: 'static + FnMut(Vec<String>),
 164    {
 165        self.0.borrow().platform.on_open_urls(Box::new(callback));
 166        self
 167    }
 168
 169    /// Invokes a handler when an already-running application is launched.
 170    /// On macOS, this can occur when the application icon is double-clicked or the app is launched via the dock.
 171    pub fn on_reopen<F>(&self, mut callback: F) -> &Self
 172    where
 173        F: 'static + FnMut(&mut AppContext),
 174    {
 175        let this = Rc::downgrade(&self.0);
 176        self.0.borrow_mut().platform.on_reopen(Box::new(move || {
 177            if let Some(app) = this.upgrade() {
 178                callback(&mut app.borrow_mut());
 179            }
 180        }));
 181        self
 182    }
 183
 184    /// Returns a handle to the [`BackgroundExecutor`] associated with this app, which can be used to spawn futures in the background.
 185    pub fn background_executor(&self) -> BackgroundExecutor {
 186        self.0.borrow().background_executor.clone()
 187    }
 188
 189    /// Returns a handle to the [`ForegroundExecutor`] associated with this app, which can be used to spawn futures in the foreground.
 190    pub fn foreground_executor(&self) -> ForegroundExecutor {
 191        self.0.borrow().foreground_executor.clone()
 192    }
 193
 194    /// Returns a reference to the [`TextSystem`] associated with this app.
 195    pub fn text_system(&self) -> Arc<TextSystem> {
 196        self.0.borrow().text_system.clone()
 197    }
 198
 199    /// Returns the file URL of the executable with the specified name in the application bundle
 200    pub fn path_for_auxiliary_executable(&self, name: &str) -> Result<PathBuf> {
 201        self.0.borrow().path_for_auxiliary_executable(name)
 202    }
 203}
 204
 205type Handler = Box<dyn FnMut(&mut AppContext) -> bool + 'static>;
 206type Listener = Box<dyn FnMut(&dyn Any, &mut AppContext) -> bool + 'static>;
 207type KeystrokeObserver = Box<dyn FnMut(&KeystrokeEvent, &mut WindowContext) + 'static>;
 208type QuitHandler = Box<dyn FnOnce(&mut AppContext) -> LocalBoxFuture<'static, ()> + 'static>;
 209type ReleaseListener = Box<dyn FnOnce(&mut dyn Any, &mut AppContext) + 'static>;
 210type NewViewListener = Box<dyn FnMut(AnyView, &mut WindowContext) + 'static>;
 211
 212/// Contains the state of the full application, and passed as a reference to a variety of callbacks.
 213/// Other contexts such as [ModelContext], [WindowContext], and [ViewContext] deref to this type, making it the most general context type.
 214/// You need a reference to an `AppContext` to access the state of a [Model].
 215pub struct AppContext {
 216    pub(crate) this: Weak<AppCell>,
 217    pub(crate) platform: Rc<dyn Platform>,
 218    text_system: Arc<TextSystem>,
 219    flushing_effects: bool,
 220    pending_updates: usize,
 221    pub(crate) actions: Rc<ActionRegistry>,
 222    pub(crate) active_drag: Option<AnyDrag>,
 223    pub(crate) background_executor: BackgroundExecutor,
 224    pub(crate) foreground_executor: ForegroundExecutor,
 225    pub(crate) loading_assets: FxHashMap<(TypeId, u64), Box<dyn Any>>,
 226    asset_source: Arc<dyn AssetSource>,
 227    pub(crate) svg_renderer: SvgRenderer,
 228    http_client: Arc<dyn HttpClient>,
 229    pub(crate) globals_by_type: FxHashMap<TypeId, Box<dyn Any>>,
 230    pub(crate) entities: EntityMap,
 231    pub(crate) new_view_observers: SubscriberSet<TypeId, NewViewListener>,
 232    pub(crate) windows: SlotMap<WindowId, Option<Window>>,
 233    pub(crate) window_handles: FxHashMap<WindowId, AnyWindowHandle>,
 234    pub(crate) keymap: Rc<RefCell<Keymap>>,
 235    pub(crate) global_action_listeners:
 236        FxHashMap<TypeId, Vec<Rc<dyn Fn(&dyn Any, DispatchPhase, &mut Self)>>>,
 237    pending_effects: VecDeque<Effect>,
 238    pub(crate) pending_notifications: FxHashSet<EntityId>,
 239    pub(crate) pending_global_notifications: FxHashSet<TypeId>,
 240    pub(crate) observers: SubscriberSet<EntityId, Handler>,
 241    // TypeId is the type of the event that the listener callback expects
 242    pub(crate) event_listeners: SubscriberSet<EntityId, (TypeId, Listener)>,
 243    pub(crate) keystroke_observers: SubscriberSet<(), KeystrokeObserver>,
 244    pub(crate) release_listeners: SubscriberSet<EntityId, ReleaseListener>,
 245    pub(crate) global_observers: SubscriberSet<TypeId, Handler>,
 246    pub(crate) quit_observers: SubscriberSet<(), QuitHandler>,
 247    pub(crate) layout_id_buffer: Vec<LayoutId>, // We recycle this memory across layout requests.
 248    pub(crate) propagate_event: bool,
 249    pub(crate) prompt_builder: Option<PromptBuilder>,
 250}
 251
 252impl AppContext {
 253    #[allow(clippy::new_ret_no_self)]
 254    pub(crate) fn new(
 255        platform: Rc<dyn Platform>,
 256        asset_source: Arc<dyn AssetSource>,
 257        http_client: Arc<dyn HttpClient>,
 258    ) -> Rc<AppCell> {
 259        let executor = platform.background_executor();
 260        let foreground_executor = platform.foreground_executor();
 261        assert!(
 262            executor.is_main_thread(),
 263            "must construct App on main thread"
 264        );
 265
 266        let text_system = Arc::new(TextSystem::new(platform.text_system()));
 267        let entities = EntityMap::new();
 268
 269        let app = Rc::new_cyclic(|this| AppCell {
 270            app: RefCell::new(AppContext {
 271                this: this.clone(),
 272                platform: platform.clone(),
 273                text_system,
 274                actions: Rc::new(ActionRegistry::default()),
 275                flushing_effects: false,
 276                pending_updates: 0,
 277                active_drag: None,
 278                background_executor: executor,
 279                foreground_executor,
 280                svg_renderer: SvgRenderer::new(asset_source.clone()),
 281                loading_assets: Default::default(),
 282                asset_source,
 283                http_client,
 284                globals_by_type: FxHashMap::default(),
 285                entities,
 286                new_view_observers: SubscriberSet::new(),
 287                window_handles: FxHashMap::default(),
 288                windows: SlotMap::with_key(),
 289                keymap: Rc::new(RefCell::new(Keymap::default())),
 290                global_action_listeners: FxHashMap::default(),
 291                pending_effects: VecDeque::new(),
 292                pending_notifications: FxHashSet::default(),
 293                pending_global_notifications: FxHashSet::default(),
 294                observers: SubscriberSet::new(),
 295                event_listeners: SubscriberSet::new(),
 296                release_listeners: SubscriberSet::new(),
 297                keystroke_observers: SubscriberSet::new(),
 298                global_observers: SubscriberSet::new(),
 299                quit_observers: SubscriberSet::new(),
 300                layout_id_buffer: Default::default(),
 301                propagate_event: true,
 302                prompt_builder: Some(PromptBuilder::Default),
 303            }),
 304        });
 305
 306        init_app_menus(platform.as_ref(), &mut app.borrow_mut());
 307
 308        platform.on_quit(Box::new({
 309            let cx = app.clone();
 310            move || {
 311                cx.borrow_mut().shutdown();
 312            }
 313        }));
 314
 315        app
 316    }
 317
 318    /// Quit the application gracefully. Handlers registered with [`ModelContext::on_app_quit`]
 319    /// will be given 100ms to complete before exiting.
 320    pub fn shutdown(&mut self) {
 321        let mut futures = Vec::new();
 322
 323        for observer in self.quit_observers.remove(&()) {
 324            futures.push(observer(self));
 325        }
 326
 327        self.windows.clear();
 328        self.window_handles.clear();
 329        self.flush_effects();
 330
 331        let futures = futures::future::join_all(futures);
 332        if self
 333            .background_executor
 334            .block_with_timeout(SHUTDOWN_TIMEOUT, futures)
 335            .is_err()
 336        {
 337            log::error!("timed out waiting on app_will_quit");
 338        }
 339    }
 340
 341    /// Gracefully quit the application via the platform's standard routine.
 342    pub fn quit(&mut self) {
 343        self.platform.quit();
 344    }
 345
 346    /// Schedules all windows in the application to be redrawn. This can be called
 347    /// multiple times in an update cycle and still result in a single redraw.
 348    pub fn refresh(&mut self) {
 349        self.pending_effects.push_back(Effect::Refresh);
 350    }
 351
 352    pub(crate) fn update<R>(&mut self, update: impl FnOnce(&mut Self) -> R) -> R {
 353        self.pending_updates += 1;
 354        let result = update(self);
 355        if !self.flushing_effects && self.pending_updates == 1 {
 356            self.flushing_effects = true;
 357            self.flush_effects();
 358            self.flushing_effects = false;
 359        }
 360        self.pending_updates -= 1;
 361        result
 362    }
 363
 364    /// Arrange a callback to be invoked when the given model or view calls `notify` on its respective context.
 365    pub fn observe<W, E>(
 366        &mut self,
 367        entity: &E,
 368        mut on_notify: impl FnMut(E, &mut AppContext) + 'static,
 369    ) -> Subscription
 370    where
 371        W: 'static,
 372        E: Entity<W>,
 373    {
 374        self.observe_internal(entity, move |e, cx| {
 375            on_notify(e, cx);
 376            true
 377        })
 378    }
 379
 380    pub(crate) fn new_observer(&mut self, key: EntityId, value: Handler) -> Subscription {
 381        let (subscription, activate) = self.observers.insert(key, value);
 382        self.defer(move |_| activate());
 383        subscription
 384    }
 385    pub(crate) fn observe_internal<W, E>(
 386        &mut self,
 387        entity: &E,
 388        mut on_notify: impl FnMut(E, &mut AppContext) -> bool + 'static,
 389    ) -> Subscription
 390    where
 391        W: 'static,
 392        E: Entity<W>,
 393    {
 394        let entity_id = entity.entity_id();
 395        let handle = entity.downgrade();
 396        self.new_observer(
 397            entity_id,
 398            Box::new(move |cx| {
 399                if let Some(handle) = E::upgrade_from(&handle) {
 400                    on_notify(handle, cx)
 401                } else {
 402                    false
 403                }
 404            }),
 405        )
 406    }
 407
 408    /// Arrange for the given callback to be invoked whenever the given model or view emits an event of a given type.
 409    /// The callback is provided a handle to the emitting entity and a reference to the emitted event.
 410    pub fn subscribe<T, E, Event>(
 411        &mut self,
 412        entity: &E,
 413        mut on_event: impl FnMut(E, &Event, &mut AppContext) + 'static,
 414    ) -> Subscription
 415    where
 416        T: 'static + EventEmitter<Event>,
 417        E: Entity<T>,
 418        Event: 'static,
 419    {
 420        self.subscribe_internal(entity, move |entity, event, cx| {
 421            on_event(entity, event, cx);
 422            true
 423        })
 424    }
 425
 426    pub(crate) fn new_subscription(
 427        &mut self,
 428        key: EntityId,
 429        value: (TypeId, Listener),
 430    ) -> Subscription {
 431        let (subscription, activate) = self.event_listeners.insert(key, value);
 432        self.defer(move |_| activate());
 433        subscription
 434    }
 435    pub(crate) fn subscribe_internal<T, E, Evt>(
 436        &mut self,
 437        entity: &E,
 438        mut on_event: impl FnMut(E, &Evt, &mut AppContext) -> bool + 'static,
 439    ) -> Subscription
 440    where
 441        T: 'static + EventEmitter<Evt>,
 442        E: Entity<T>,
 443        Evt: 'static,
 444    {
 445        let entity_id = entity.entity_id();
 446        let entity = entity.downgrade();
 447        self.new_subscription(
 448            entity_id,
 449            (
 450                TypeId::of::<Evt>(),
 451                Box::new(move |event, cx| {
 452                    let event: &Evt = event.downcast_ref().expect("invalid event type");
 453                    if let Some(handle) = E::upgrade_from(&entity) {
 454                        on_event(handle, event, cx)
 455                    } else {
 456                        false
 457                    }
 458                }),
 459            ),
 460        )
 461    }
 462
 463    /// Returns handles to all open windows in the application.
 464    /// Each handle could be downcast to a handle typed for the root view of that window.
 465    /// To find all windows of a given type, you could filter on
 466    pub fn windows(&self) -> Vec<AnyWindowHandle> {
 467        self.windows
 468            .keys()
 469            .flat_map(|window_id| self.window_handles.get(&window_id).copied())
 470            .collect()
 471    }
 472
 473    /// Returns the window handles ordered by their appearance on screen, front to back.
 474    ///
 475    /// The first window in the returned list is the active/topmost window of the application.
 476    ///
 477    /// This method returns None if the platform doesn't implement the method yet.
 478    pub fn window_stack(&self) -> Option<Vec<AnyWindowHandle>> {
 479        self.platform.window_stack()
 480    }
 481
 482    /// Returns a handle to the window that is currently focused at the platform level, if one exists.
 483    pub fn active_window(&self) -> Option<AnyWindowHandle> {
 484        self.platform.active_window()
 485    }
 486
 487    /// Opens a new window with the given option and the root view returned by the given function.
 488    /// The function is invoked with a `WindowContext`, which can be used to interact with window-specific
 489    /// functionality.
 490    pub fn open_window<V: 'static + Render>(
 491        &mut self,
 492        options: crate::WindowOptions,
 493        build_root_view: impl FnOnce(&mut WindowContext) -> View<V>,
 494    ) -> anyhow::Result<WindowHandle<V>> {
 495        self.update(|cx| {
 496            let id = cx.windows.insert(None);
 497            let handle = WindowHandle::new(id);
 498            match Window::new(handle.into(), options, cx) {
 499                Ok(mut window) => {
 500                    let root_view = build_root_view(&mut WindowContext::new(cx, &mut window));
 501                    window.root_view.replace(root_view.into());
 502                    WindowContext::new(cx, &mut window).defer(|cx| cx.appearance_changed());
 503                    cx.window_handles.insert(id, window.handle);
 504                    cx.windows.get_mut(id).unwrap().replace(window);
 505                    Ok(handle)
 506                }
 507                Err(e) => {
 508                    cx.windows.remove(id);
 509                    Err(e)
 510                }
 511            }
 512        })
 513    }
 514
 515    /// Instructs the platform to activate the application by bringing it to the foreground.
 516    pub fn activate(&self, ignoring_other_apps: bool) {
 517        self.platform.activate(ignoring_other_apps);
 518    }
 519
 520    /// Hide the application at the platform level.
 521    pub fn hide(&self) {
 522        self.platform.hide();
 523    }
 524
 525    /// Hide other applications at the platform level.
 526    pub fn hide_other_apps(&self) {
 527        self.platform.hide_other_apps();
 528    }
 529
 530    /// Unhide other applications at the platform level.
 531    pub fn unhide_other_apps(&self) {
 532        self.platform.unhide_other_apps();
 533    }
 534
 535    /// Returns the list of currently active displays.
 536    pub fn displays(&self) -> Vec<Rc<dyn PlatformDisplay>> {
 537        self.platform.displays()
 538    }
 539
 540    /// Returns the primary display that will be used for new windows.
 541    pub fn primary_display(&self) -> Option<Rc<dyn PlatformDisplay>> {
 542        self.platform.primary_display()
 543    }
 544
 545    /// Returns the display with the given ID, if one exists.
 546    pub fn find_display(&self, id: DisplayId) -> Option<Rc<dyn PlatformDisplay>> {
 547        self.displays()
 548            .iter()
 549            .find(|display| display.id() == id)
 550            .cloned()
 551    }
 552
 553    /// Returns the appearance of the application's windows.
 554    pub fn window_appearance(&self) -> WindowAppearance {
 555        self.platform.window_appearance()
 556    }
 557
 558    /// Writes data to the primary selection buffer.
 559    /// Only available on Linux.
 560    #[cfg(target_os = "linux")]
 561    pub fn write_to_primary(&self, item: ClipboardItem) {
 562        self.platform.write_to_primary(item)
 563    }
 564
 565    /// Writes data to the platform clipboard.
 566    pub fn write_to_clipboard(&self, item: ClipboardItem) {
 567        self.platform.write_to_clipboard(item)
 568    }
 569
 570    /// Reads data from the primary selection buffer.
 571    /// Only available on Linux.
 572    #[cfg(target_os = "linux")]
 573    pub fn read_from_primary(&self) -> Option<ClipboardItem> {
 574        self.platform.read_from_primary()
 575    }
 576
 577    /// Reads data from the platform clipboard.
 578    pub fn read_from_clipboard(&self) -> Option<ClipboardItem> {
 579        self.platform.read_from_clipboard()
 580    }
 581
 582    /// Writes credentials to the platform keychain.
 583    pub fn write_credentials(
 584        &self,
 585        url: &str,
 586        username: &str,
 587        password: &[u8],
 588    ) -> Task<Result<()>> {
 589        self.platform.write_credentials(url, username, password)
 590    }
 591
 592    /// Reads credentials from the platform keychain.
 593    pub fn read_credentials(&self, url: &str) -> Task<Result<Option<(String, Vec<u8>)>>> {
 594        self.platform.read_credentials(url)
 595    }
 596
 597    /// Deletes credentials from the platform keychain.
 598    pub fn delete_credentials(&self, url: &str) -> Task<Result<()>> {
 599        self.platform.delete_credentials(url)
 600    }
 601
 602    /// Directs the platform's default browser to open the given URL.
 603    pub fn open_url(&self, url: &str) {
 604        self.platform.open_url(url);
 605    }
 606
 607    /// register_url_scheme requests that the given scheme (e.g. `zed` for `zed://` urls)
 608    /// is opened by the current app.
 609    /// On some platforms (e.g. macOS) you may be able to register URL schemes as part of app
 610    /// distribution, but this method exists to let you register schemes at runtime.
 611    pub fn register_url_scheme(&self, scheme: &str) -> Task<Result<()>> {
 612        self.platform.register_url_scheme(scheme)
 613    }
 614
 615    /// Returns the full pathname of the current app bundle.
 616    /// If the app is not being run from a bundle, returns an error.
 617    pub fn app_path(&self) -> Result<PathBuf> {
 618        self.platform.app_path()
 619    }
 620
 621    /// On Linux, returns the name of the compositor in use.
 622    /// Is blank on other platforms.
 623    pub fn compositor_name(&self) -> &'static str {
 624        self.platform.compositor_name()
 625    }
 626
 627    /// Returns the file URL of the executable with the specified name in the application bundle
 628    pub fn path_for_auxiliary_executable(&self, name: &str) -> Result<PathBuf> {
 629        self.platform.path_for_auxiliary_executable(name)
 630    }
 631
 632    /// Displays a platform modal for selecting paths.
 633    /// When one or more paths are selected, they'll be relayed asynchronously via the returned oneshot channel.
 634    /// If cancelled, a `None` will be relayed instead.
 635    /// May return an error on Linux if the file picker couldn't be opened.
 636    pub fn prompt_for_paths(
 637        &self,
 638        options: PathPromptOptions,
 639    ) -> oneshot::Receiver<Result<Option<Vec<PathBuf>>>> {
 640        self.platform.prompt_for_paths(options)
 641    }
 642
 643    /// Displays a platform modal for selecting a new path where a file can be saved.
 644    /// The provided directory will be used to set the initial location.
 645    /// When a path is selected, it is relayed asynchronously via the returned oneshot channel.
 646    /// If cancelled, a `None` will be relayed instead.
 647    /// May return an error on Linux if the file picker couldn't be opened.
 648    pub fn prompt_for_new_path(
 649        &self,
 650        directory: &Path,
 651    ) -> oneshot::Receiver<Result<Option<PathBuf>>> {
 652        self.platform.prompt_for_new_path(directory)
 653    }
 654
 655    /// Reveals the specified path at the platform level, such as in Finder on macOS.
 656    pub fn reveal_path(&self, path: &Path) {
 657        self.platform.reveal_path(path)
 658    }
 659
 660    /// Opens the specified path with the system's default application.
 661    pub fn open_with_system(&self, path: &Path) {
 662        self.platform.open_with_system(path)
 663    }
 664
 665    /// Returns whether the user has configured scrollbars to auto-hide at the platform level.
 666    pub fn should_auto_hide_scrollbars(&self) -> bool {
 667        self.platform.should_auto_hide_scrollbars()
 668    }
 669
 670    /// Restart the application.
 671    pub fn restart(&self, binary_path: Option<PathBuf>) {
 672        self.platform.restart(binary_path)
 673    }
 674
 675    /// Updates the http client assigned to GPUI
 676    pub fn set_http_client(&mut self, new_client: Arc<dyn HttpClient>) {
 677        self.http_client = new_client;
 678    }
 679
 680    /// Returns the http client assigned to GPUI
 681    pub fn http_client(&self) -> Arc<dyn HttpClient> {
 682        self.http_client.clone()
 683    }
 684
 685    /// Returns the SVG renderer GPUI uses
 686    pub(crate) fn svg_renderer(&self) -> SvgRenderer {
 687        self.svg_renderer.clone()
 688    }
 689
 690    pub(crate) fn push_effect(&mut self, effect: Effect) {
 691        match &effect {
 692            Effect::Notify { emitter } => {
 693                if !self.pending_notifications.insert(*emitter) {
 694                    return;
 695                }
 696            }
 697            Effect::NotifyGlobalObservers { global_type } => {
 698                if !self.pending_global_notifications.insert(*global_type) {
 699                    return;
 700                }
 701            }
 702            _ => {}
 703        };
 704
 705        self.pending_effects.push_back(effect);
 706    }
 707
 708    /// Called at the end of [`AppContext::update`] to complete any side effects
 709    /// such as notifying observers, emitting events, etc. Effects can themselves
 710    /// cause effects, so we continue looping until all effects are processed.
 711    fn flush_effects(&mut self) {
 712        loop {
 713            self.release_dropped_entities();
 714            self.release_dropped_focus_handles();
 715
 716            if let Some(effect) = self.pending_effects.pop_front() {
 717                match effect {
 718                    Effect::Notify { emitter } => {
 719                        self.apply_notify_effect(emitter);
 720                    }
 721
 722                    Effect::Emit {
 723                        emitter,
 724                        event_type,
 725                        event,
 726                    } => self.apply_emit_effect(emitter, event_type, event),
 727
 728                    Effect::Refresh => {
 729                        self.apply_refresh_effect();
 730                    }
 731
 732                    Effect::NotifyGlobalObservers { global_type } => {
 733                        self.apply_notify_global_observers_effect(global_type);
 734                    }
 735
 736                    Effect::Defer { callback } => {
 737                        self.apply_defer_effect(callback);
 738                    }
 739                }
 740            } else {
 741                #[cfg(any(test, feature = "test-support"))]
 742                for window in self
 743                    .windows
 744                    .values()
 745                    .filter_map(|window| {
 746                        let window = window.as_ref()?;
 747                        window.dirty.get().then_some(window.handle)
 748                    })
 749                    .collect::<Vec<_>>()
 750                {
 751                    self.update_window(window, |_, cx| cx.draw()).unwrap();
 752                }
 753
 754                if self.pending_effects.is_empty() {
 755                    break;
 756                }
 757            }
 758        }
 759    }
 760
 761    /// Repeatedly called during `flush_effects` to release any entities whose
 762    /// reference count has become zero. We invoke any release observers before dropping
 763    /// each entity.
 764    fn release_dropped_entities(&mut self) {
 765        loop {
 766            let dropped = self.entities.take_dropped();
 767            if dropped.is_empty() {
 768                break;
 769            }
 770
 771            for (entity_id, mut entity) in dropped {
 772                self.observers.remove(&entity_id);
 773                self.event_listeners.remove(&entity_id);
 774                for release_callback in self.release_listeners.remove(&entity_id) {
 775                    release_callback(entity.as_mut(), self);
 776                }
 777            }
 778        }
 779    }
 780
 781    /// Repeatedly called during `flush_effects` to handle a focused handle being dropped.
 782    fn release_dropped_focus_handles(&mut self) {
 783        for window_handle in self.windows() {
 784            window_handle
 785                .update(self, |_, cx| {
 786                    let mut blur_window = false;
 787                    let focus = cx.window.focus;
 788                    cx.window.focus_handles.write().retain(|handle_id, count| {
 789                        if count.load(SeqCst) == 0 {
 790                            if focus == Some(handle_id) {
 791                                blur_window = true;
 792                            }
 793                            false
 794                        } else {
 795                            true
 796                        }
 797                    });
 798
 799                    if blur_window {
 800                        cx.blur();
 801                    }
 802                })
 803                .unwrap();
 804        }
 805    }
 806
 807    fn apply_notify_effect(&mut self, emitter: EntityId) {
 808        self.pending_notifications.remove(&emitter);
 809
 810        self.observers
 811            .clone()
 812            .retain(&emitter, |handler| handler(self));
 813    }
 814
 815    fn apply_emit_effect(&mut self, emitter: EntityId, event_type: TypeId, event: Box<dyn Any>) {
 816        self.event_listeners
 817            .clone()
 818            .retain(&emitter, |(stored_type, handler)| {
 819                if *stored_type == event_type {
 820                    handler(event.as_ref(), self)
 821                } else {
 822                    true
 823                }
 824            });
 825    }
 826
 827    fn apply_refresh_effect(&mut self) {
 828        for window in self.windows.values_mut() {
 829            if let Some(window) = window.as_mut() {
 830                window.dirty.set(true);
 831            }
 832        }
 833    }
 834
 835    fn apply_notify_global_observers_effect(&mut self, type_id: TypeId) {
 836        self.pending_global_notifications.remove(&type_id);
 837        self.global_observers
 838            .clone()
 839            .retain(&type_id, |observer| observer(self));
 840    }
 841
 842    fn apply_defer_effect(&mut self, callback: Box<dyn FnOnce(&mut Self) + 'static>) {
 843        callback(self);
 844    }
 845
 846    /// Creates an `AsyncAppContext`, which can be cloned and has a static lifetime
 847    /// so it can be held across `await` points.
 848    pub fn to_async(&self) -> AsyncAppContext {
 849        AsyncAppContext {
 850            app: self.this.clone(),
 851            background_executor: self.background_executor.clone(),
 852            foreground_executor: self.foreground_executor.clone(),
 853        }
 854    }
 855
 856    /// Obtains a reference to the executor, which can be used to spawn futures.
 857    pub fn background_executor(&self) -> &BackgroundExecutor {
 858        &self.background_executor
 859    }
 860
 861    /// Obtains a reference to the executor, which can be used to spawn futures.
 862    pub fn foreground_executor(&self) -> &ForegroundExecutor {
 863        &self.foreground_executor
 864    }
 865
 866    /// Spawns the future returned by the given function on the thread pool. The closure will be invoked
 867    /// with [AsyncAppContext], which allows the application state to be accessed across await points.
 868    pub fn spawn<Fut, R>(&self, f: impl FnOnce(AsyncAppContext) -> Fut) -> Task<R>
 869    where
 870        Fut: Future<Output = R> + 'static,
 871        R: 'static,
 872    {
 873        self.foreground_executor.spawn(f(self.to_async()))
 874    }
 875
 876    /// Schedules the given function to be run at the end of the current effect cycle, allowing entities
 877    /// that are currently on the stack to be returned to the app.
 878    pub fn defer(&mut self, f: impl FnOnce(&mut AppContext) + 'static) {
 879        self.push_effect(Effect::Defer {
 880            callback: Box::new(f),
 881        });
 882    }
 883
 884    /// Accessor for the application's asset source, which is provided when constructing the `App`.
 885    pub fn asset_source(&self) -> &Arc<dyn AssetSource> {
 886        &self.asset_source
 887    }
 888
 889    /// Accessor for the text system.
 890    pub fn text_system(&self) -> &Arc<TextSystem> {
 891        &self.text_system
 892    }
 893
 894    /// Check whether a global of the given type has been assigned.
 895    pub fn has_global<G: Global>(&self) -> bool {
 896        self.globals_by_type.contains_key(&TypeId::of::<G>())
 897    }
 898
 899    /// Access the global of the given type. Panics if a global for that type has not been assigned.
 900    #[track_caller]
 901    pub fn global<G: Global>(&self) -> &G {
 902        self.globals_by_type
 903            .get(&TypeId::of::<G>())
 904            .map(|any_state| any_state.downcast_ref::<G>().unwrap())
 905            .ok_or_else(|| anyhow!("no state of type {} exists", type_name::<G>()))
 906            .unwrap()
 907    }
 908
 909    /// Access the global of the given type if a value has been assigned.
 910    pub fn try_global<G: Global>(&self) -> Option<&G> {
 911        self.globals_by_type
 912            .get(&TypeId::of::<G>())
 913            .map(|any_state| any_state.downcast_ref::<G>().unwrap())
 914    }
 915
 916    /// Access the global of the given type mutably. Panics if a global for that type has not been assigned.
 917    #[track_caller]
 918    pub fn global_mut<G: Global>(&mut self) -> &mut G {
 919        let global_type = TypeId::of::<G>();
 920        self.push_effect(Effect::NotifyGlobalObservers { global_type });
 921        self.globals_by_type
 922            .get_mut(&global_type)
 923            .and_then(|any_state| any_state.downcast_mut::<G>())
 924            .ok_or_else(|| anyhow!("no state of type {} exists", type_name::<G>()))
 925            .unwrap()
 926    }
 927
 928    /// Access the global of the given type mutably. A default value is assigned if a global of this type has not
 929    /// yet been assigned.
 930    pub fn default_global<G: Global + Default>(&mut self) -> &mut G {
 931        let global_type = TypeId::of::<G>();
 932        self.push_effect(Effect::NotifyGlobalObservers { global_type });
 933        self.globals_by_type
 934            .entry(global_type)
 935            .or_insert_with(|| Box::<G>::default())
 936            .downcast_mut::<G>()
 937            .unwrap()
 938    }
 939
 940    /// Sets the value of the global of the given type.
 941    pub fn set_global<G: Global>(&mut self, global: G) {
 942        let global_type = TypeId::of::<G>();
 943        self.push_effect(Effect::NotifyGlobalObservers { global_type });
 944        self.globals_by_type.insert(global_type, Box::new(global));
 945    }
 946
 947    /// Clear all stored globals. Does not notify global observers.
 948    #[cfg(any(test, feature = "test-support"))]
 949    pub fn clear_globals(&mut self) {
 950        self.globals_by_type.drain();
 951    }
 952
 953    /// Remove the global of the given type from the app context. Does not notify global observers.
 954    pub fn remove_global<G: Global>(&mut self) -> G {
 955        let global_type = TypeId::of::<G>();
 956        self.push_effect(Effect::NotifyGlobalObservers { global_type });
 957        *self
 958            .globals_by_type
 959            .remove(&global_type)
 960            .unwrap_or_else(|| panic!("no global added for {}", std::any::type_name::<G>()))
 961            .downcast()
 962            .unwrap()
 963    }
 964
 965    /// Register a callback to be invoked when a global of the given type is updated.
 966    pub fn observe_global<G: Global>(
 967        &mut self,
 968        mut f: impl FnMut(&mut Self) + 'static,
 969    ) -> Subscription {
 970        let (subscription, activate) = self.global_observers.insert(
 971            TypeId::of::<G>(),
 972            Box::new(move |cx| {
 973                f(cx);
 974                true
 975            }),
 976        );
 977        self.defer(move |_| activate());
 978        subscription
 979    }
 980
 981    /// Move the global of the given type to the stack.
 982    pub(crate) fn lease_global<G: Global>(&mut self) -> GlobalLease<G> {
 983        GlobalLease::new(
 984            self.globals_by_type
 985                .remove(&TypeId::of::<G>())
 986                .ok_or_else(|| anyhow!("no global registered of type {}", type_name::<G>()))
 987                .unwrap(),
 988        )
 989    }
 990
 991    /// Restore the global of the given type after it is moved to the stack.
 992    pub(crate) fn end_global_lease<G: Global>(&mut self, lease: GlobalLease<G>) {
 993        let global_type = TypeId::of::<G>();
 994        self.push_effect(Effect::NotifyGlobalObservers { global_type });
 995        self.globals_by_type.insert(global_type, lease.global);
 996    }
 997
 998    pub(crate) fn new_view_observer(
 999        &mut self,
1000        key: TypeId,
1001        value: NewViewListener,
1002    ) -> Subscription {
1003        let (subscription, activate) = self.new_view_observers.insert(key, value);
1004        activate();
1005        subscription
1006    }
1007    /// Arrange for the given function to be invoked whenever a view of the specified type is created.
1008    /// The function will be passed a mutable reference to the view along with an appropriate context.
1009    pub fn observe_new_views<V: 'static>(
1010        &mut self,
1011        on_new: impl 'static + Fn(&mut V, &mut ViewContext<V>),
1012    ) -> Subscription {
1013        self.new_view_observer(
1014            TypeId::of::<V>(),
1015            Box::new(move |any_view: AnyView, cx: &mut WindowContext| {
1016                any_view
1017                    .downcast::<V>()
1018                    .unwrap()
1019                    .update(cx, |view_state, cx| {
1020                        on_new(view_state, cx);
1021                    })
1022            }),
1023        )
1024    }
1025
1026    /// Observe the release of a model or view. The callback is invoked after the model or view
1027    /// has no more strong references but before it has been dropped.
1028    pub fn observe_release<E, T>(
1029        &mut self,
1030        handle: &E,
1031        on_release: impl FnOnce(&mut T, &mut AppContext) + 'static,
1032    ) -> Subscription
1033    where
1034        E: Entity<T>,
1035        T: 'static,
1036    {
1037        let (subscription, activate) = self.release_listeners.insert(
1038            handle.entity_id(),
1039            Box::new(move |entity, cx| {
1040                let entity = entity.downcast_mut().expect("invalid entity type");
1041                on_release(entity, cx)
1042            }),
1043        );
1044        activate();
1045        subscription
1046    }
1047
1048    /// Register a callback to be invoked when a keystroke is received by the application
1049    /// in any window. Note that this fires after all other action and event mechanisms have resolved
1050    /// and that this API will not be invoked if the event's propagation is stopped.
1051    pub fn observe_keystrokes(
1052        &mut self,
1053        f: impl FnMut(&KeystrokeEvent, &mut WindowContext) + 'static,
1054    ) -> Subscription {
1055        fn inner(
1056            keystroke_observers: &mut SubscriberSet<(), KeystrokeObserver>,
1057            handler: KeystrokeObserver,
1058        ) -> Subscription {
1059            let (subscription, activate) = keystroke_observers.insert((), handler);
1060            activate();
1061            subscription
1062        }
1063        inner(&mut self.keystroke_observers, Box::new(f))
1064    }
1065
1066    /// Register key bindings.
1067    pub fn bind_keys(&mut self, bindings: impl IntoIterator<Item = KeyBinding>) {
1068        self.keymap.borrow_mut().add_bindings(bindings);
1069        self.pending_effects.push_back(Effect::Refresh);
1070    }
1071
1072    /// Clear all key bindings in the app.
1073    pub fn clear_key_bindings(&mut self) {
1074        self.keymap.borrow_mut().clear();
1075        self.pending_effects.push_back(Effect::Refresh);
1076    }
1077
1078    /// Register a global listener for actions invoked via the keyboard.
1079    pub fn on_action<A: Action>(&mut self, listener: impl Fn(&A, &mut Self) + 'static) {
1080        self.global_action_listeners
1081            .entry(TypeId::of::<A>())
1082            .or_default()
1083            .push(Rc::new(move |action, phase, cx| {
1084                if phase == DispatchPhase::Bubble {
1085                    let action = action.downcast_ref().unwrap();
1086                    listener(action, cx)
1087                }
1088            }));
1089    }
1090
1091    /// Event handlers propagate events by default. Call this method to stop dispatching to
1092    /// event handlers with a lower z-index (mouse) or higher in the tree (keyboard). This is
1093    /// the opposite of [`Self::propagate`]. It's also possible to cancel a call to [`Self::propagate`] by
1094    /// calling this method before effects are flushed.
1095    pub fn stop_propagation(&mut self) {
1096        self.propagate_event = false;
1097    }
1098
1099    /// Action handlers stop propagation by default during the bubble phase of action dispatch
1100    /// dispatching to action handlers higher in the element tree. This is the opposite of
1101    /// [`Self::stop_propagation`]. It's also possible to cancel a call to [`Self::stop_propagation`] by calling
1102    /// this method before effects are flushed.
1103    pub fn propagate(&mut self) {
1104        self.propagate_event = true;
1105    }
1106
1107    /// Build an action from some arbitrary data, typically a keymap entry.
1108    pub fn build_action(
1109        &self,
1110        name: &str,
1111        data: Option<serde_json::Value>,
1112    ) -> Result<Box<dyn Action>> {
1113        self.actions.build_action(name, data)
1114    }
1115
1116    /// Get a list of all action names that have been registered.
1117    /// in the application. Note that registration only allows for
1118    /// actions to be built dynamically, and is unrelated to binding
1119    /// actions in the element tree.
1120    pub fn all_action_names(&self) -> &[SharedString] {
1121        self.actions.all_action_names()
1122    }
1123
1124    /// Register a callback to be invoked when the application is about to quit.
1125    /// It is not possible to cancel the quit event at this point.
1126    pub fn on_app_quit<Fut>(
1127        &mut self,
1128        mut on_quit: impl FnMut(&mut AppContext) -> Fut + 'static,
1129    ) -> Subscription
1130    where
1131        Fut: 'static + Future<Output = ()>,
1132    {
1133        let (subscription, activate) = self.quit_observers.insert(
1134            (),
1135            Box::new(move |cx| {
1136                let future = on_quit(cx);
1137                future.boxed_local()
1138            }),
1139        );
1140        activate();
1141        subscription
1142    }
1143
1144    pub(crate) fn clear_pending_keystrokes(&mut self) {
1145        for window in self.windows() {
1146            window
1147                .update(self, |_, cx| {
1148                    cx.clear_pending_keystrokes();
1149                })
1150                .ok();
1151        }
1152    }
1153
1154    /// Checks if the given action is bound in the current context, as defined by the app's current focus,
1155    /// the bindings in the element tree, and any global action listeners.
1156    pub fn is_action_available(&mut self, action: &dyn Action) -> bool {
1157        let mut action_available = false;
1158        if let Some(window) = self.active_window() {
1159            if let Ok(window_action_available) =
1160                window.update(self, |_, cx| cx.is_action_available(action))
1161            {
1162                action_available = window_action_available;
1163            }
1164        }
1165
1166        action_available
1167            || self
1168                .global_action_listeners
1169                .contains_key(&action.as_any().type_id())
1170    }
1171
1172    /// Sets the menu bar for this application. This will replace any existing menu bar.
1173    pub fn set_menus(&mut self, menus: Vec<Menu>) {
1174        self.platform.set_menus(menus, &self.keymap.borrow());
1175    }
1176
1177    /// Gets the menu bar for this application.
1178    pub fn get_menus(&self) -> Option<Vec<OwnedMenu>> {
1179        self.platform.get_menus()
1180    }
1181
1182    /// Sets the right click menu for the app icon in the dock
1183    pub fn set_dock_menu(&mut self, menus: Vec<MenuItem>) {
1184        self.platform.set_dock_menu(menus, &self.keymap.borrow());
1185    }
1186
1187    /// Adds given path to the bottom of the list of recent paths for the application.
1188    /// The list is usually shown on the application icon's context menu in the dock,
1189    /// and allows to open the recent files via that context menu.
1190    /// If the path is already in the list, it will be moved to the bottom of the list.
1191    pub fn add_recent_document(&mut self, path: &Path) {
1192        self.platform.add_recent_document(path);
1193    }
1194
1195    /// Dispatch an action to the currently active window or global action handler
1196    /// See [action::Action] for more information on how actions work
1197    pub fn dispatch_action(&mut self, action: &dyn Action) {
1198        if let Some(active_window) = self.active_window() {
1199            active_window
1200                .update(self, |_, cx| cx.dispatch_action(action.boxed_clone()))
1201                .log_err();
1202        } else {
1203            self.dispatch_global_action(action);
1204        }
1205    }
1206
1207    fn dispatch_global_action(&mut self, action: &dyn Action) {
1208        self.propagate_event = true;
1209
1210        if let Some(mut global_listeners) = self
1211            .global_action_listeners
1212            .remove(&action.as_any().type_id())
1213        {
1214            for listener in &global_listeners {
1215                listener(action.as_any(), DispatchPhase::Capture, self);
1216                if !self.propagate_event {
1217                    break;
1218                }
1219            }
1220
1221            global_listeners.extend(
1222                self.global_action_listeners
1223                    .remove(&action.as_any().type_id())
1224                    .unwrap_or_default(),
1225            );
1226
1227            self.global_action_listeners
1228                .insert(action.as_any().type_id(), global_listeners);
1229        }
1230
1231        if self.propagate_event {
1232            if let Some(mut global_listeners) = self
1233                .global_action_listeners
1234                .remove(&action.as_any().type_id())
1235            {
1236                for listener in global_listeners.iter().rev() {
1237                    listener(action.as_any(), DispatchPhase::Bubble, self);
1238                    if !self.propagate_event {
1239                        break;
1240                    }
1241                }
1242
1243                global_listeners.extend(
1244                    self.global_action_listeners
1245                        .remove(&action.as_any().type_id())
1246                        .unwrap_or_default(),
1247                );
1248
1249                self.global_action_listeners
1250                    .insert(action.as_any().type_id(), global_listeners);
1251            }
1252        }
1253    }
1254
1255    /// Is there currently something being dragged?
1256    pub fn has_active_drag(&self) -> bool {
1257        self.active_drag.is_some()
1258    }
1259
1260    /// Set the prompt renderer for GPUI. This will replace the default or platform specific
1261    /// prompts with this custom implementation.
1262    pub fn set_prompt_builder(
1263        &mut self,
1264        renderer: impl Fn(
1265                PromptLevel,
1266                &str,
1267                Option<&str>,
1268                &[&str],
1269                PromptHandle,
1270                &mut WindowContext,
1271            ) -> RenderablePromptHandle
1272            + 'static,
1273    ) {
1274        self.prompt_builder = Some(PromptBuilder::Custom(Box::new(renderer)))
1275    }
1276
1277    /// Remove an asset from GPUI's cache
1278    pub fn remove_cached_asset<A: Asset + 'static>(&mut self, source: &A::Source) {
1279        let asset_id = (TypeId::of::<A>(), hash(source));
1280        self.loading_assets.remove(&asset_id);
1281    }
1282
1283    /// Asynchronously load an asset, if the asset hasn't finished loading this will return None.
1284    ///
1285    /// Note that the multiple calls to this method will only result in one `Asset::load` call at a
1286    /// time, and the results of this call will be cached
1287    ///
1288    /// This asset will not be cached by default, see [Self::use_cached_asset]
1289    pub fn fetch_asset<A: Asset + 'static>(
1290        &mut self,
1291        source: &A::Source,
1292    ) -> (Shared<Task<A::Output>>, bool) {
1293        let asset_id = (TypeId::of::<A>(), hash(source));
1294        let mut is_first = false;
1295        let task = self
1296            .loading_assets
1297            .remove(&asset_id)
1298            .map(|boxed_task| *boxed_task.downcast::<Shared<Task<A::Output>>>().unwrap())
1299            .unwrap_or_else(|| {
1300                is_first = true;
1301                let future = A::load(source.clone(), self);
1302                let task = self.background_executor().spawn(future).shared();
1303                task
1304            });
1305
1306        self.loading_assets.insert(asset_id, Box::new(task.clone()));
1307
1308        (task, is_first)
1309    }
1310}
1311
1312impl Context for AppContext {
1313    type Result<T> = T;
1314
1315    /// Build an entity that is owned by the application. The given function will be invoked with
1316    /// a `ModelContext` and must return an object representing the entity. A `Model` handle will be returned,
1317    /// which can be used to access the entity in a context.
1318    fn new_model<T: 'static>(
1319        &mut self,
1320        build_model: impl FnOnce(&mut ModelContext<'_, T>) -> T,
1321    ) -> Model<T> {
1322        self.update(|cx| {
1323            let slot = cx.entities.reserve();
1324            let entity = build_model(&mut ModelContext::new(cx, slot.downgrade()));
1325            cx.entities.insert(slot, entity)
1326        })
1327    }
1328
1329    fn reserve_model<T: 'static>(&mut self) -> Self::Result<Reservation<T>> {
1330        Reservation(self.entities.reserve())
1331    }
1332
1333    fn insert_model<T: 'static>(
1334        &mut self,
1335        reservation: Reservation<T>,
1336        build_model: impl FnOnce(&mut ModelContext<'_, T>) -> T,
1337    ) -> Self::Result<Model<T>> {
1338        self.update(|cx| {
1339            let slot = reservation.0;
1340            let entity = build_model(&mut ModelContext::new(cx, slot.downgrade()));
1341            cx.entities.insert(slot, entity)
1342        })
1343    }
1344
1345    /// Updates the entity referenced by the given model. The function is passed a mutable reference to the
1346    /// entity along with a `ModelContext` for the entity.
1347    fn update_model<T: 'static, R>(
1348        &mut self,
1349        model: &Model<T>,
1350        update: impl FnOnce(&mut T, &mut ModelContext<'_, T>) -> R,
1351    ) -> R {
1352        self.update(|cx| {
1353            let mut entity = cx.entities.lease(model);
1354            let result = update(&mut entity, &mut ModelContext::new(cx, model.downgrade()));
1355            cx.entities.end_lease(entity);
1356            result
1357        })
1358    }
1359
1360    fn read_model<T, R>(
1361        &self,
1362        handle: &Model<T>,
1363        read: impl FnOnce(&T, &AppContext) -> R,
1364    ) -> Self::Result<R>
1365    where
1366        T: 'static,
1367    {
1368        let entity = self.entities.read(handle);
1369        read(entity, self)
1370    }
1371
1372    fn update_window<T, F>(&mut self, handle: AnyWindowHandle, update: F) -> Result<T>
1373    where
1374        F: FnOnce(AnyView, &mut WindowContext<'_>) -> T,
1375    {
1376        self.update(|cx| {
1377            let mut window = cx
1378                .windows
1379                .get_mut(handle.id)
1380                .ok_or_else(|| anyhow!("window not found"))?
1381                .take()
1382                .ok_or_else(|| anyhow!("window not found"))?;
1383
1384            let root_view = window.root_view.clone().unwrap();
1385            let result = update(root_view, &mut WindowContext::new(cx, &mut window));
1386
1387            if window.removed {
1388                cx.window_handles.remove(&handle.id);
1389                cx.windows.remove(handle.id);
1390            } else {
1391                cx.windows
1392                    .get_mut(handle.id)
1393                    .ok_or_else(|| anyhow!("window not found"))?
1394                    .replace(window);
1395            }
1396
1397            Ok(result)
1398        })
1399    }
1400
1401    fn read_window<T, R>(
1402        &self,
1403        window: &WindowHandle<T>,
1404        read: impl FnOnce(View<T>, &AppContext) -> R,
1405    ) -> Result<R>
1406    where
1407        T: 'static,
1408    {
1409        let window = self
1410            .windows
1411            .get(window.id)
1412            .ok_or_else(|| anyhow!("window not found"))?
1413            .as_ref()
1414            .unwrap();
1415
1416        let root_view = window.root_view.clone().unwrap();
1417        let view = root_view
1418            .downcast::<T>()
1419            .map_err(|_| anyhow!("root view's type has changed"))?;
1420
1421        Ok(read(view, self))
1422    }
1423}
1424
1425/// These effects are processed at the end of each application update cycle.
1426pub(crate) enum Effect {
1427    Notify {
1428        emitter: EntityId,
1429    },
1430    Emit {
1431        emitter: EntityId,
1432        event_type: TypeId,
1433        event: Box<dyn Any>,
1434    },
1435    Refresh,
1436    NotifyGlobalObservers {
1437        global_type: TypeId,
1438    },
1439    Defer {
1440        callback: Box<dyn FnOnce(&mut AppContext) + 'static>,
1441    },
1442}
1443
1444/// Wraps a global variable value during `update_global` while the value has been moved to the stack.
1445pub(crate) struct GlobalLease<G: Global> {
1446    global: Box<dyn Any>,
1447    global_type: PhantomData<G>,
1448}
1449
1450impl<G: Global> GlobalLease<G> {
1451    fn new(global: Box<dyn Any>) -> Self {
1452        GlobalLease {
1453            global,
1454            global_type: PhantomData,
1455        }
1456    }
1457}
1458
1459impl<G: Global> Deref for GlobalLease<G> {
1460    type Target = G;
1461
1462    fn deref(&self) -> &Self::Target {
1463        self.global.downcast_ref().unwrap()
1464    }
1465}
1466
1467impl<G: Global> DerefMut for GlobalLease<G> {
1468    fn deref_mut(&mut self) -> &mut Self::Target {
1469        self.global.downcast_mut().unwrap()
1470    }
1471}
1472
1473/// Contains state associated with an active drag operation, started by dragging an element
1474/// within the window or by dragging into the app from the underlying platform.
1475pub struct AnyDrag {
1476    /// The view used to render this drag
1477    pub view: AnyView,
1478
1479    /// The value of the dragged item, to be dropped
1480    pub value: Box<dyn Any>,
1481
1482    /// This is used to render the dragged item in the same place
1483    /// on the original element that the drag was initiated
1484    pub cursor_offset: Point<Pixels>,
1485}
1486
1487/// Contains state associated with a tooltip. You'll only need this struct if you're implementing
1488/// tooltip behavior on a custom element. Otherwise, use [Div::tooltip].
1489#[derive(Clone)]
1490pub struct AnyTooltip {
1491    /// The view used to display the tooltip
1492    pub view: AnyView,
1493
1494    /// The absolute position of the mouse when the tooltip was deployed.
1495    pub mouse_position: Point<Pixels>,
1496}
1497
1498/// A keystroke event, and potentially the associated action
1499#[derive(Debug)]
1500pub struct KeystrokeEvent {
1501    /// The keystroke that occurred
1502    pub keystroke: Keystroke,
1503
1504    /// The action that was resolved for the keystroke, if any
1505    pub action: Option<Box<dyn Action>>,
1506}