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//! The [`EventLoop`] struct and assorted supporting types, including
//! [`ControlFlow`].
//!
//! If you want to send custom events to the event loop, use
//! [`EventLoop::create_proxy`] to acquire an [`EventLoopProxy`] and call its
//! [`wake_up`][EventLoopProxy::wake_up] method. Then during handling the wake up
//! you can poll your event sources.
//!
//! See the root-level documentation for information on how to create and use an event loop to
//! handle events.
use std::fmt;
use std::marker::PhantomData;
#[cfg(any(x11_platform, wayland_platform))]
use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, RawFd};
use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
#[cfg(not(web_platform))]
use std::time::{Duration, Instant};
#[cfg(web_platform)]
use web_time::{Duration, Instant};
use crate::application::ApplicationHandler;
use crate::error::{EventLoopError, RequestError};
use crate::monitor::MonitorHandle;
use crate::platform_impl;
use crate::utils::AsAny;
use crate::window::{CustomCursor, CustomCursorSource, Theme, Window, WindowAttributes};
/// Provides a way to retrieve events from the system and from the windows that were registered to
/// the events loop.
///
/// An `EventLoop` can be seen more or less as a "context". Calling [`EventLoop::new`]
/// initializes everything that will be required to create windows. For example on Linux creating
/// an event loop opens a connection to the X or Wayland server.
///
/// To wake up an `EventLoop` from a another thread, see the [`EventLoopProxy`] docs.
///
/// Note that this cannot be shared across threads (due to platform-dependant logic
/// forbidding it), as such it is neither [`Send`] nor [`Sync`]. If you need cross-thread access,
/// the [`Window`] created from this _can_ be sent to an other thread, and the
/// [`EventLoopProxy`] allows you to wake up an `EventLoop` from another thread.
///
/// [`Window`]: crate::window::Window
pub struct EventLoop {
pub(crate) event_loop: platform_impl::EventLoop,
pub(crate) _marker: PhantomData<*mut ()>, // Not Send nor Sync
}
/// Object that allows building the event loop.
///
/// This is used to make specifying options that affect the whole application
/// easier. But note that constructing multiple event loops is not supported.
///
/// This can be created using [`EventLoop::builder`].
#[derive(Default, PartialEq, Eq, Hash)]
pub struct EventLoopBuilder {
pub(crate) platform_specific: platform_impl::PlatformSpecificEventLoopAttributes,
}
static EVENT_LOOP_CREATED: AtomicBool = AtomicBool::new(false);
impl EventLoopBuilder {
/// Builds a new event loop.
///
/// ***For cross-platform compatibility, the [`EventLoop`] must be created on the main thread,
/// and only once per application.***
///
/// Calling this function will result in display backend initialisation.
///
/// ## Panics
///
/// Attempting to create the event loop off the main thread will panic. This
/// restriction isn't strictly necessary on all platforms, but is imposed to
/// eliminate any nasty surprises when porting to platforms that require it.
/// `EventLoopBuilderExt::any_thread` functions are exposed in the relevant
/// [`platform`] module if the target platform supports creating an event
/// loop on any thread.
///
/// ## Platform-specific
///
/// - **Wayland/X11:** to prevent running under `Wayland` or `X11` unset `WAYLAND_DISPLAY` or
/// `DISPLAY` respectively when building the event loop.
/// - **Android:** must be configured with an `AndroidApp` from `android_main()` by calling
/// [`.with_android_app(app)`] before calling `.build()`, otherwise it'll panic.
///
/// [`platform`]: crate::platform
#[cfg_attr(
android_platform,
doc = "[`.with_android_app(app)`]: \
crate::platform::android::EventLoopBuilderExtAndroid::with_android_app"
)]
#[cfg_attr(
not(android_platform),
doc = "[`.with_android_app(app)`]: #only-available-on-android"
)]
#[inline]
pub fn build(&mut self) -> Result<EventLoop, EventLoopError> {
let _span = tracing::debug_span!("winit::EventLoopBuilder::build").entered();
if EVENT_LOOP_CREATED.swap(true, Ordering::Relaxed) {
return Err(EventLoopError::RecreationAttempt);
}
// Certain platforms accept a mutable reference in their API.
#[allow(clippy::unnecessary_mut_passed)]
Ok(EventLoop {
event_loop: platform_impl::EventLoop::new(&mut self.platform_specific)?,
_marker: PhantomData,
})
}
#[cfg(web_platform)]
pub(crate) fn allow_event_loop_recreation() {
EVENT_LOOP_CREATED.store(false, Ordering::Relaxed);
}
}
impl fmt::Debug for EventLoopBuilder {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("EventLoopBuilder").finish_non_exhaustive()
}
}
impl fmt::Debug for EventLoop {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("EventLoop").finish_non_exhaustive()
}
}
/// Set through [`ActiveEventLoop::set_control_flow()`].
///
/// Indicates the desired behavior of the event loop after [`about_to_wait`] is called.
///
/// Defaults to [`Wait`].
///
/// [`Wait`]: Self::Wait
/// [`about_to_wait`]: crate::application::ApplicationHandler::about_to_wait
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Hash)]
pub enum ControlFlow {
/// When the current loop iteration finishes, immediately begin a new iteration regardless of
/// whether or not new events are available to process.
Poll,
/// When the current loop iteration finishes, suspend the thread until another event arrives.
#[default]
Wait,
/// When the current loop iteration finishes, suspend the thread until either another event
/// arrives or the given time is reached.
///
/// Useful for implementing efficient timers. Applications which want to render at the
/// display's native refresh rate should instead use [`Poll`] and the VSync functionality
/// of a graphics API to reduce odds of missed frames.
///
/// [`Poll`]: Self::Poll
WaitUntil(Instant),
}
impl ControlFlow {
/// Creates a [`ControlFlow`] that waits until a timeout has expired.
///
/// In most cases, this is set to [`WaitUntil`]. However, if the timeout overflows, it is
/// instead set to [`Wait`].
///
/// [`WaitUntil`]: Self::WaitUntil
/// [`Wait`]: Self::Wait
pub fn wait_duration(timeout: Duration) -> Self {
match Instant::now().checked_add(timeout) {
Some(instant) => Self::WaitUntil(instant),
None => Self::Wait,
}
}
}
impl EventLoop {
/// Create the event loop.
///
/// This is an alias of `EventLoop::builder().build()`.
#[inline]
pub fn new() -> Result<EventLoop, EventLoopError> {
Self::builder().build()
}
/// Start building a new event loop.
///
/// This returns an [`EventLoopBuilder`], to allow configuring the event loop before creation.
///
/// To get the actual event loop, call [`build`][EventLoopBuilder::build] on that.
#[inline]
pub fn builder() -> EventLoopBuilder {
EventLoopBuilder { platform_specific: Default::default() }
}
}
impl EventLoop {
/// Run the application with the event loop on the calling thread.
///
/// See the [`set_control_flow()`] docs on how to change the event loop's behavior.
///
/// ## Platform-specific
///
/// - **iOS:** Will never return to the caller and so values not passed to this function will
/// *not* be dropped before the process exits.
/// - **Web:** Will _act_ as if it never returns to the caller by throwing a Javascript
/// exception (that Rust doesn't see) that will also mean that the rest of the function is
/// never executed and any values not passed to this function will *not* be dropped.
///
/// Web applications are recommended to use
#[cfg_attr(
any(web_platform, docsrs),
doc = " [`EventLoopExtWeb::spawn_app()`][crate::platform::web::EventLoopExtWeb::spawn_app()]"
)]
#[cfg_attr(not(any(web_platform, docsrs)), doc = " `EventLoopExtWeb::spawn_app()`")]
/// [^1] instead of [`run_app()`] to avoid the need for the Javascript exception trick, and to
/// make it clearer that the event loop runs asynchronously (via the browser's own,
/// internal, event loop) and doesn't block the current thread of execution like it does
/// on other platforms.
///
/// This function won't be available with `target_feature = "exception-handling"`.
///
/// [^1]: `spawn_app()` is only available on the Web platform.
///
/// [`set_control_flow()`]: ActiveEventLoop::set_control_flow()
/// [`run_app()`]: Self::run_app()
#[inline]
#[cfg(not(all(web_platform, target_feature = "exception-handling")))]
pub fn run_app<A: ApplicationHandler>(self, app: A) -> Result<(), EventLoopError> {
self.event_loop.run_app(app)
}
/// Creates an [`EventLoopProxy`] that can be used to dispatch user events
/// to the main event loop, possibly from another thread.
pub fn create_proxy(&self) -> EventLoopProxy {
self.event_loop.window_target().create_proxy()
}
/// Gets a persistent reference to the underlying platform display.
///
/// See the [`OwnedDisplayHandle`] type for more information.
pub fn owned_display_handle(&self) -> OwnedDisplayHandle {
self.event_loop.window_target().owned_display_handle()
}
/// Change if or when [`DeviceEvent`]s are captured.
///
/// See [`ActiveEventLoop::listen_device_events`] for details.
///
/// [`DeviceEvent`]: crate::event::DeviceEvent
pub fn listen_device_events(&self, allowed: DeviceEvents) {
let _span = tracing::debug_span!(
"winit::EventLoop::listen_device_events",
allowed = ?allowed
)
.entered();
self.event_loop.window_target().listen_device_events(allowed)
}
/// Sets the [`ControlFlow`].
pub fn set_control_flow(&self, control_flow: ControlFlow) {
self.event_loop.window_target().set_control_flow(control_flow);
}
/// Create custom cursor.
///
/// ## Platform-specific
///
/// **iOS / Android / Orbital:** Unsupported.
pub fn create_custom_cursor(
&self,
custom_cursor: CustomCursorSource,
) -> Result<CustomCursor, RequestError> {
self.event_loop.window_target().create_custom_cursor(custom_cursor)
}
}
#[cfg(feature = "rwh_06")]
impl rwh_06::HasDisplayHandle for EventLoop {
fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
rwh_06::HasDisplayHandle::display_handle(self.event_loop.window_target().rwh_06_handle())
}
}
#[cfg(any(x11_platform, wayland_platform))]
impl AsFd for EventLoop {
/// Get the underlying [EventLoop]'s `fd` which you can register
/// into other event loop, like [`calloop`] or [`mio`]. When doing so, the
/// loop must be polled with the [`pump_app_events`] API.
///
/// [`calloop`]: https://crates.io/crates/calloop
/// [`mio`]: https://crates.io/crates/mio
/// [`pump_app_events`]: crate::platform::pump_events::EventLoopExtPumpEvents::pump_app_events
fn as_fd(&self) -> BorrowedFd<'_> {
self.event_loop.as_fd()
}
}
#[cfg(any(x11_platform, wayland_platform))]
impl AsRawFd for EventLoop {
/// Get the underlying [EventLoop]'s raw `fd` which you can register
/// into other event loop, like [`calloop`] or [`mio`]. When doing so, the
/// loop must be polled with the [`pump_app_events`] API.
///
/// [`calloop`]: https://crates.io/crates/calloop
/// [`mio`]: https://crates.io/crates/mio
/// [`pump_app_events`]: crate::platform::pump_events::EventLoopExtPumpEvents::pump_app_events
fn as_raw_fd(&self) -> RawFd {
self.event_loop.as_raw_fd()
}
}
pub trait ActiveEventLoop: AsAny {
/// Creates an [`EventLoopProxy`] that can be used to dispatch user events
/// to the main event loop, possibly from another thread.
fn create_proxy(&self) -> EventLoopProxy;
/// Create the window.
///
/// Possible causes of error include denied permission, incompatible system, and lack of memory.
///
/// ## Platform-specific
///
/// - **Web:** The window is created but not inserted into the Web page automatically. Please
/// see the Web platform module for more information.
fn create_window(
&self,
window_attributes: WindowAttributes,
) -> Result<Box<dyn Window>, RequestError>;
/// Create custom cursor.
///
/// ## Platform-specific
///
/// **iOS / Android / Orbital:** Unsupported.
fn create_custom_cursor(
&self,
custom_cursor: CustomCursorSource,
) -> Result<CustomCursor, RequestError>;
/// Returns the list of all the monitors available on the system.
///
/// ## Platform-specific
///
/// **Web:** Only returns the current monitor without
#[cfg_attr(
any(web_platform, docsrs),
doc = "[detailed monitor permissions][crate::platform::web::ActiveEventLoopExtWeb::request_detailed_monitor_permission]."
)]
#[cfg_attr(not(any(web_platform, docsrs)), doc = "detailed monitor permissions.")]
fn available_monitors(&self) -> Box<dyn Iterator<Item = MonitorHandle>>;
/// Returns the primary monitor of the system.
///
/// Returns `None` if it can't identify any monitor as a primary one.
///
/// ## Platform-specific
///
/// - **Wayland:** Always returns `None`.
/// - **Web:** Always returns `None` without
#[cfg_attr(
any(web_platform, docsrs),
doc = " [detailed monitor permissions][crate::platform::web::ActiveEventLoopExtWeb::request_detailed_monitor_permission]."
)]
#[cfg_attr(not(any(web_platform, docsrs)), doc = " detailed monitor permissions.")]
fn primary_monitor(&self) -> Option<MonitorHandle>;
/// Change if or when [`DeviceEvent`]s are captured.
///
/// Since the [`DeviceEvent`] capture can lead to high CPU usage for unfocused windows, winit
/// will ignore them by default for unfocused windows on Linux/BSD. This method allows changing
/// this at runtime to explicitly capture them again.
///
/// ## Platform-specific
///
/// - **Wayland / macOS / iOS / Android / Orbital:** Unsupported.
///
/// [`DeviceEvent`]: crate::event::DeviceEvent
fn listen_device_events(&self, allowed: DeviceEvents);
/// Returns the current system theme.
///
/// Returns `None` if it cannot be determined on the current platform.
///
/// ## Platform-specific
///
/// - **iOS / Android / Wayland / x11 / Orbital:** Unsupported.
fn system_theme(&self) -> Option<Theme>;
/// Sets the [`ControlFlow`].
fn set_control_flow(&self, control_flow: ControlFlow);
/// Gets the current [`ControlFlow`].
fn control_flow(&self) -> ControlFlow;
/// This exits the event loop.
///
/// See [`exiting`][crate::application::ApplicationHandler::exiting].
fn exit(&self);
/// Returns if the [`EventLoop`] is about to stop.
///
/// See [`exit()`][Self::exit].
fn exiting(&self) -> bool;
/// Gets a persistent reference to the underlying platform display.
///
/// See the [`OwnedDisplayHandle`] type for more information.
fn owned_display_handle(&self) -> OwnedDisplayHandle;
/// Get the raw-window-handle handle.
#[cfg(feature = "rwh_06")]
fn rwh_06_handle(&self) -> &dyn rwh_06::HasDisplayHandle;
}
#[cfg(feature = "rwh_06")]
impl rwh_06::HasDisplayHandle for dyn ActiveEventLoop + '_ {
fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
self.rwh_06_handle().display_handle()
}
}
/// A proxy for the underlying display handle.
///
/// The purpose of this type is to provide a cheaply clonable handle to the underlying
/// display handle. This is often used by graphics APIs to connect to the underlying APIs.
/// It is difficult to keep a handle to the [`EventLoop`] type or the [`ActiveEventLoop`]
/// type. In contrast, this type involves no lifetimes and can be persisted for as long as
/// needed.
///
/// For all platforms, this is one of the following:
///
/// - A zero-sized type that is likely optimized out.
/// - A reference-counted pointer to the underlying type.
#[derive(Clone, PartialEq, Eq)]
pub struct OwnedDisplayHandle {
#[cfg_attr(not(feature = "rwh_06"), allow(dead_code))]
pub(crate) platform: platform_impl::OwnedDisplayHandle,
}
impl fmt::Debug for OwnedDisplayHandle {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("OwnedDisplayHandle").finish_non_exhaustive()
}
}
#[cfg(feature = "rwh_06")]
impl rwh_06::HasDisplayHandle for OwnedDisplayHandle {
#[inline]
fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
let raw = self.platform.raw_display_handle_rwh_06()?;
// SAFETY: The underlying display handle should be safe.
let handle = unsafe { rwh_06::DisplayHandle::borrow_raw(raw) };
Ok(handle)
}
}
/// Control the [`EventLoop`], possibly from a different thread, without referencing it directly.
#[derive(Clone)]
pub struct EventLoopProxy {
pub(crate) event_loop_proxy: platform_impl::EventLoopProxy,
}
impl EventLoopProxy {
/// Wake up the [`EventLoop`], resulting in [`ApplicationHandler::proxy_wake_up()`] being
/// called.
///
/// Calls to this method are coalesced into a single call to [`proxy_wake_up`], see the
/// documentation on that for details.
///
/// If the event loop is no longer running, this is a no-op.
///
/// [`proxy_wake_up`]: ApplicationHandler::proxy_wake_up
///
/// # Platform-specific
///
/// - **Windows**: The wake-up may be ignored under high contention, see [#3687].
///
/// [#3687]: https://github.com/rust-windowing/winit/pull/3687
pub fn wake_up(&self) {
self.event_loop_proxy.wake_up();
}
}
impl fmt::Debug for EventLoopProxy {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ActiveEventLoop").finish_non_exhaustive()
}
}
/// Control when device events are captured.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Default)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum DeviceEvents {
/// Report device events regardless of window focus.
Always,
/// Only capture device events while the window is focused.
#[default]
WhenFocused,
/// Never capture device events.
Never,
}
/// A unique identifier of the winit's async request.
///
/// This could be used to identify the async request once it's done
/// and a specific action must be taken.
///
/// One of the handling scenarios could be to maintain a working list
/// containing [`AsyncRequestSerial`] and some closure associated with it.
/// Then once event is arriving the working list is being traversed and a job
/// executed and removed from the list.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct AsyncRequestSerial {
serial: usize,
}
impl AsyncRequestSerial {
// TODO(kchibisov): Remove `cfg` when the clipboard will be added.
#[allow(dead_code)]
pub(crate) fn get() -> Self {
static CURRENT_SERIAL: AtomicUsize = AtomicUsize::new(0);
// NOTE: We rely on wrap around here, while the user may just request
// in the loop usize::MAX times that's issue is considered on them.
let serial = CURRENT_SERIAL.fetch_add(1, Ordering::Relaxed);
Self { serial }
}
}