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