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Windows: Use ApplicationHandler (#4141)

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* Make ActiveEventLoop a thin wrapper over EventLoopRunner
* Use ApplicationHandler instead of Event
This commit is contained in:
Mads Marquart 2025-03-01 12:09:59 +01:00 • committed by GitHub
parent 8c3e69c08b
commit e26b831f23
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GPG key ID: B5690EEEBB952194
4 changed files with 391 additions and 567 deletions
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182
src/platform_impl/windows/event_loop/runner.rs
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@ -1,22 +1,27 @@
use std::any::Any;
use std::cell::{Cell, RefCell};
use std::collections::VecDeque;
use std::rc::Rc;
use std::sync::{Arc, Mutex};
use std::time::Instant;
use std::{mem, panic};
use windows_sys::Win32::Foundation::HWND;
use super::ControlFlow;
use super::{ActiveEventLoop, ControlFlow, EventLoopThreadExecutor};
use crate::application::ApplicationHandler;
use crate::dpi::PhysicalSize;
use crate::event::{Event, StartCause, SurfaceSizeWriter, WindowEvent};
use crate::event::{DeviceEvent, DeviceId, StartCause, SurfaceSizeWriter, WindowEvent};
use crate::event_loop::ActiveEventLoop as RootActiveEventLoop;
use crate::platform_impl::platform::event_loop::{WindowData, GWL_USERDATA};
use crate::platform_impl::platform::get_window_long;
use crate::window::WindowId;
type EventHandler = Cell<Option<Box<dyn FnMut(Event)>>>;
type EventHandler = Cell<Option<&'static mut (dyn ApplicationHandler + 'static)>>;
pub(crate) struct EventLoopRunner {
pub(super) thread_id: u32,
// The event loop's win32 handles
pub(super) thread_msg_target: HWND,
@ -29,8 +34,8 @@ pub(crate) struct EventLoopRunner {
exit: Cell<Option<i32>>,
runner_state: Cell<RunnerState>,
last_events_cleared: Cell<Instant>,
event_handler: EventHandler,
event_buffer: RefCell<VecDeque<BufferedEvent>>,
event_handler: Rc<EventHandler>,
event_buffer: RefCell<VecDeque<Event>>,
panic_error: Cell<Option<PanicError>>,
}
@ -51,14 +56,20 @@ pub(crate) enum RunnerState {
Destroyed,
}
enum BufferedEvent {
Event(Event),
ScaleFactorChanged(HWND, f64, PhysicalSize<u32>),
#[derive(Debug, Clone)]
pub(crate) enum Event {
Device { device_id: DeviceId, event: DeviceEvent },
Window { window_id: WindowId, event: WindowEvent },
BufferedScaleFactorChanged(HWND, f64, PhysicalSize<u32>),
// FIXME(madsmtm): Coalesce these into a flag (or similar) instead of handling them as events.
// https://github.com/rust-windowing/winit/pull/3687
WakeUp,
}
impl EventLoopRunner {
pub(crate) fn new(thread_msg_target: HWND) -> EventLoopRunner {
EventLoopRunner {
pub(crate) fn new(thread_id: u32, thread_msg_target: HWND) -> Self {
Self {
thread_id,
thread_msg_target,
interrupt_msg_dispatch: Cell::new(false),
runner_state: Cell::new(RunnerState::Uninitialized),
@ -66,40 +77,50 @@ impl EventLoopRunner {
exit: Cell::new(None),
panic_error: Cell::new(None),
last_events_cleared: Cell::new(Instant::now()),
event_handler: Cell::new(None),
event_handler: Rc::new(Cell::new(None)),
event_buffer: RefCell::new(VecDeque::new()),
}
}
/// Associate the application's event handler with the runner
/// Associate the application's event handler with the runner.
///
/// # Safety
/// This is ignoring the lifetime of the application handler (which may not
/// outlive the EventLoopRunner) and can lead to undefined behaviour if
/// the handler is not cleared before the end of real lifetime.
///
/// All public APIs that take an event handler (`run`, `run_on_demand`,
/// `pump_events`) _must_ pair a call to `set_event_handler` with
/// a call to `clear_event_handler` before returning to avoid
/// undefined behaviour.
pub(crate) unsafe fn set_event_handler<F>(&self, f: F)
where
F: FnMut(Event),
{
// Erase closure lifetime.
// SAFETY: Caller upholds that the lifetime of the closure is upheld.
let f =
unsafe { mem::transmute::<Box<dyn FnMut(Event)>, Box<dyn FnMut(Event)>>(Box::new(f)) };
let old_event_handler = self.event_handler.replace(Some(f));
assert!(old_event_handler.is_none());
}
/// The returned type must not be leaked (as that would allow the application to be associated
/// with the runner for too long).
pub(crate) unsafe fn set_app<'app>(
&self,
app: &'app mut (dyn ApplicationHandler + 'app),
) -> impl Drop + 'app {
// Erase app lifetime, to allow storing on the event loop runner.
//
// SAFETY: Caller upholds that the lifetime of the closure is upheld, by not dropping the
// return type which resets it.
let f = unsafe {
mem::transmute::<
&'app mut (dyn ApplicationHandler + 'app),
&'static mut (dyn ApplicationHandler + 'static),
>(app)
};
pub(crate) fn clear_event_handler(&self) {
self.event_handler.set(None);
let old_event_handler = self.event_handler.replace(Some(f));
assert!(old_event_handler.is_none());
struct Resetter(Rc<EventHandler>);
impl Drop for Resetter {
fn drop(&mut self) {
self.0.set(None);
}
}
Resetter(self.event_handler.clone())
}
pub(crate) fn reset_runner(&self) {
let EventLoopRunner {
let Self {
thread_id: _,
thread_msg_target: _,
interrupt_msg_dispatch,
runner_state,
@ -188,21 +209,26 @@ impl EventLoopRunner {
None
}
}
#[inline(always)]
pub(crate) fn create_thread_executor(&self) -> EventLoopThreadExecutor {
EventLoopThreadExecutor { thread_id: self.thread_id, target_window: self.thread_msg_target }
}
}
/// Event dispatch functions.
impl EventLoopRunner {
pub(crate) fn prepare_wait(&self) {
pub(crate) fn prepare_wait(self: &Rc<Self>) {
self.move_state_to(RunnerState::Idle);
}
pub(crate) fn wakeup(&self) {
pub(crate) fn wakeup(self: &Rc<Self>) {
self.move_state_to(RunnerState::HandlingMainEvents);
}
pub(crate) fn send_event(&self, event: Event) {
if let Event::WindowEvent { event: WindowEvent::RedrawRequested, .. } = event {
self.call_event_handler(event);
pub(crate) fn send_event(self: &Rc<Self>, event: Event) {
if let Event::Window { event: WindowEvent::RedrawRequested, .. } = event {
self.call_event_handler(|app, event_loop| event.dispatch_event(app, event_loop));
// As a rule, to ensure that `pump_events` can't block an external event loop
// for too long, we always guarantee that `pump_events` will return control to
// the external loop asap after a `RedrawRequested` event is dispatched.
@ -210,31 +236,34 @@ impl EventLoopRunner {
} else if self.should_buffer() {
// If the runner is already borrowed, we're in the middle of an event loop invocation.
// Add the event to a buffer to be processed later.
self.event_buffer.borrow_mut().push_back(BufferedEvent::from_event(event))
self.event_buffer.borrow_mut().push_back(event.buffer_scale_factor())
} else {
self.call_event_handler(event);
self.call_event_handler(|app, event_loop| event.dispatch_event(app, event_loop));
self.dispatch_buffered_events();
}
}
pub(crate) fn loop_destroyed(&self) {
pub(crate) fn loop_destroyed(self: &Rc<Self>) {
self.move_state_to(RunnerState::Destroyed);
}
fn call_event_handler(&self, event: Event) {
fn call_event_handler(
self: &Rc<Self>,
closure: impl FnOnce(&mut dyn ApplicationHandler, &dyn RootActiveEventLoop),
) {
self.catch_unwind(|| {
let mut event_handler = self.event_handler.take().expect(
let event_handler = self.event_handler.take().expect(
"either event handler is re-entrant (likely), or no event handler is registered \
(very unlikely)",
);
event_handler(event);
closure(event_handler, ActiveEventLoop::from_ref(self));
assert!(self.event_handler.replace(Some(event_handler)).is_none());
});
}
fn dispatch_buffered_events(&self) {
fn dispatch_buffered_events(self: &Rc<Self>) {
loop {
// We do this instead of using a `while let` loop because if we use a `while let`
// loop the reference returned `borrow_mut()` doesn't get dropped until the end
@ -242,7 +271,9 @@ impl EventLoopRunner {
// `process_event` will fail.
let buffered_event_opt = self.event_buffer.borrow_mut().pop_front();
match buffered_event_opt {
Some(e) => e.dispatch_event(|e| self.call_event_handler(e)),
Some(e) => {
self.call_event_handler(|app, event_loop| e.dispatch_event(app, event_loop))
},
None => break,
}
}
@ -272,7 +303,7 @@ impl EventLoopRunner {
/// state is a no-op. Even if the `new_runner_state` isn't the immediate next state in the
/// runner state machine (e.g. `self.runner_state == HandlingMainEvents` and
/// `new_runner_state == Idle`), the intermediate state transitions will still be executed.
fn move_state_to(&self, new_runner_state: RunnerState) {
fn move_state_to(self: &Rc<Self>, new_runner_state: RunnerState) {
use RunnerState::{Destroyed, HandlingMainEvents, Idle, Uninitialized};
match (self.runner_state.replace(new_runner_state), new_runner_state) {
@ -287,14 +318,14 @@ impl EventLoopRunner {
},
(Uninitialized, Idle) => {
self.call_new_events(true);
self.call_event_handler(Event::AboutToWait);
self.call_event_handler(|app, event_loop| app.about_to_wait(event_loop));
self.last_events_cleared.set(Instant::now());
},
(Uninitialized, Destroyed) => {
self.call_new_events(true);
self.call_event_handler(Event::AboutToWait);
self.call_event_handler(|app, event_loop| app.about_to_wait(event_loop));
self.last_events_cleared.set(Instant::now());
self.call_event_handler(Event::LoopExiting);
self.call_event_handler(|app, event_loop| app.exiting(event_loop));
},
(_, Uninitialized) => panic!("cannot move state to Uninitialized"),
@ -303,25 +334,25 @@ impl EventLoopRunner {
self.call_new_events(false);
},
(Idle, Destroyed) => {
self.call_event_handler(Event::LoopExiting);
self.call_event_handler(|app, event_loop| app.exiting(event_loop));
},
(HandlingMainEvents, Idle) => {
// This is always the last event we dispatch before waiting for new events
self.call_event_handler(Event::AboutToWait);
self.call_event_handler(|app, event_loop| app.about_to_wait(event_loop));
self.last_events_cleared.set(Instant::now());
},
(HandlingMainEvents, Destroyed) => {
self.call_event_handler(Event::AboutToWait);
self.call_event_handler(|app, event_loop| app.about_to_wait(event_loop));
self.last_events_cleared.set(Instant::now());
self.call_event_handler(Event::LoopExiting);
self.call_event_handler(|app, event_loop| app.exiting(event_loop));
},
(Destroyed, _) => panic!("cannot move state from Destroyed"),
}
}
fn call_new_events(&self, init: bool) {
fn call_new_events(self: &Rc<Self>, init: bool) {
let start_cause = match (init, self.control_flow(), self.exit.get()) {
(true, ..) => StartCause::Init,
(false, ControlFlow::Poll, None) => StartCause::Poll,
@ -343,45 +374,55 @@ impl EventLoopRunner {
}
},
};
self.call_event_handler(Event::NewEvents(start_cause));
self.call_event_handler(|app, event_loop| app.new_events(event_loop, start_cause));
// NB: For consistency all platforms must call `can_create_surfaces` even though Windows
// applications don't themselves have a formal surface destroy/create lifecycle.
if init {
self.call_event_handler(Event::CreateSurfaces);
self.call_event_handler(|app, event_loop| app.can_create_surfaces(event_loop));
}
self.dispatch_buffered_events();
}
}
impl BufferedEvent {
pub fn from_event(event: Event) -> BufferedEvent {
match event {
Event::WindowEvent {
impl Event {
/// Mark ScaleFactorChanged as being buffered (which forces us to re-handle when the user set a
/// new size).
pub fn buffer_scale_factor(self) -> Self {
match self {
Self::Window {
event: WindowEvent::ScaleFactorChanged { scale_factor, surface_size_writer },
window_id,
} => BufferedEvent::ScaleFactorChanged(
} => Event::BufferedScaleFactorChanged(
window_id.into_raw() as HWND,
scale_factor,
*surface_size_writer.new_surface_size.upgrade().unwrap().lock().unwrap(),
),
event => BufferedEvent::Event(event),
event => event,
}
}
pub fn dispatch_event(self, dispatch: impl FnOnce(Event)) {
pub fn dispatch_event(
self,
app: &mut dyn ApplicationHandler,
event_loop: &dyn RootActiveEventLoop,
) {
match self {
Self::Event(event) => dispatch(event),
Self::ScaleFactorChanged(window, scale_factor, new_surface_size) => {
Self::Window { window_id, event } => app.window_event(event_loop, window_id, event),
Self::Device { device_id, event } => {
app.device_event(event_loop, Some(device_id), event)
},
Self::BufferedScaleFactorChanged(window, scale_factor, new_surface_size) => {
let user_new_surface_size = Arc::new(Mutex::new(new_surface_size));
dispatch(Event::WindowEvent {
window_id: WindowId::from_raw(window as usize),
event: WindowEvent::ScaleFactorChanged {
app.window_event(
event_loop,
WindowId::from_raw(window as usize),
WindowEvent::ScaleFactorChanged {
scale_factor,
surface_size_writer: SurfaceSizeWriter::new(Arc::downgrade(
&user_new_surface_size,
)),
},
});
);
let surface_size = *user_new_surface_size.lock().unwrap();
drop(user_new_surface_size);
@ -395,6 +436,7 @@ impl BufferedEvent {
window_flags.set_size(window, surface_size);
}
},
Self::WakeUp => app.proxy_wake_up(event_loop),
}
}
}