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use super::{backend, state::State};
use crate::event::{Event, StartCause, WindowEvent};
use crate::event_loop as root;
use crate::window::WindowId;
use instant::{Duration, Instant};
use std::{
cell::RefCell,
clone::Clone,
collections::{HashSet, VecDeque},
rc::Rc,
};
pub struct Shared<T>(Rc<Execution<T>>);
impl<T> Clone for Shared<T> {
fn clone(&self) -> Self {
Shared(self.0.clone())
}
}
pub struct Execution<T> {
runner: RefCell<Option<Runner<T>>>,
events: RefCell<VecDeque<Event<T>>>,
id: RefCell<u32>,
redraw_pending: RefCell<HashSet<WindowId>>,
}
struct Runner<T> {
state: State,
is_busy: bool,
event_handler: Box<dyn FnMut(Event<T>, &mut root::ControlFlow)>,
}
impl<T: 'static> Runner<T> {
pub fn new(event_handler: Box<dyn FnMut(Event<T>, &mut root::ControlFlow)>) -> Self {
Runner {
state: State::Init,
is_busy: false,
event_handler,
}
}
}
impl<T: 'static> Shared<T> {
pub fn new() -> Self {
Shared(Rc::new(Execution {
runner: RefCell::new(None),
events: RefCell::new(VecDeque::new()),
id: RefCell::new(0),
redraw_pending: RefCell::new(HashSet::new()),
}))
}
// Set the event callback to use for the event loop runner
// This the event callback is a fairly thin layer over the user-provided callback that closes
// over a RootEventLoopWindowTarget reference
pub fn set_listener(&self, event_handler: Box<dyn FnMut(Event<T>, &mut root::ControlFlow)>) {
self.0.runner.replace(Some(Runner::new(event_handler)));
self.send_event(Event::NewEvents(StartCause::Init));
let close_instance = self.clone();
backend::on_unload(move || close_instance.handle_unload());
}
// Generate a strictly increasing ID
// This is used to differentiate windows when handling events
pub fn generate_id(&self) -> u32 {
let mut id = self.0.id.borrow_mut();
*id += 1;
*id
}
pub fn request_redraw(&self, id: WindowId) {
self.0.redraw_pending.borrow_mut().insert(id);
}
// Add an event to the event loop runner
//
// It will determine if the event should be immediately sent to the user or buffered for later
pub fn send_event(&self, event: Event<T>) {
// If the event loop is closed, it should discard any new events
if self.is_closed() {
return;
}
// Determine if event handling is in process, and then release the borrow on the runner
let (start_cause, event_is_start) = match *self.0.runner.borrow() {
Some(ref runner) if !runner.is_busy => {
if let Event::NewEvents(cause) = event {
(cause, true)
} else {
(
match runner.state {
State::Init => StartCause::Init,
State::Poll { .. } => StartCause::Poll,
State::Wait { start } => StartCause::WaitCancelled {
start,
requested_resume: None,
},
State::WaitUntil { start, end, .. } => StartCause::WaitCancelled {
start,
requested_resume: Some(end),
},
State::Exit => {
return;
}
},
false,
)
}
}
_ => {
// Events are currently being handled, so queue this one and don't try to
// double-process the event queue
self.0.events.borrow_mut().push_back(event);
return;
}
};
let mut control = self.current_control_flow();
// Handle starting a new batch of events
//
// The user is informed via Event::NewEvents that there is a batch of events to process
// However, there is only one of these per batch of events
self.handle_event(Event::NewEvents(start_cause), &mut control);
if !event_is_start {
self.handle_event(event, &mut control);
}
// Collect all of the redraw events to avoid double-locking the RefCell
let redraw_events: Vec<WindowId> = self.0.redraw_pending.borrow_mut().drain().collect();
for window_id in redraw_events {
self.handle_event(
Event::WindowEvent {
window_id,
event: WindowEvent::RedrawRequested,
},
&mut control,
);
}
self.handle_event(Event::EventsCleared, &mut control);
self.apply_control_flow(control);
// If the event loop is closed, it has been closed this iteration and now the closing
// event should be emitted
if self.is_closed() {
self.handle_event(Event::LoopDestroyed, &mut control);
}
}
fn handle_unload(&self) {
self.apply_control_flow(root::ControlFlow::Exit);
let mut control = self.current_control_flow();
self.handle_event(Event::LoopDestroyed, &mut control);
}
// handle_event takes in events and either queues them or applies a callback
//
// It should only ever be called from send_event
fn handle_event(&self, event: Event<T>, control: &mut root::ControlFlow) {
let is_closed = self.is_closed();
match *self.0.runner.borrow_mut() {
Some(ref mut runner) => {
// An event is being processed, so the runner should be marked busy
runner.is_busy = true;
(runner.event_handler)(event, control);
// Maintain closed state, even if the callback changes it
if is_closed {
*control = root::ControlFlow::Exit;
}
// An event is no longer being processed
runner.is_busy = false;
}
// If an event is being handled without a runner somehow, add it to the event queue so
// it will eventually be processed
_ => self.0.events.borrow_mut().push_back(event),
}
// Don't take events out of the queue if the loop is closed or the runner doesn't exist
// If the runner doesn't exist and this method recurses, it will recurse infinitely
if !is_closed && self.0.runner.borrow().is_some() {
// Take an event out of the queue and handle it
if let Some(event) = self.0.events.borrow_mut().pop_front() {
self.handle_event(event, control);
}
}
}
// Apply the new ControlFlow that has been selected by the user
// Start any necessary timeouts etc
fn apply_control_flow(&self, control_flow: root::ControlFlow) {
let new_state = match control_flow {
root::ControlFlow::Poll => {
let cloned = self.clone();
State::Poll {
timeout: backend::Timeout::new(
move || cloned.send_event(Event::NewEvents(StartCause::Poll)),
Duration::from_millis(0),
),
}
}
root::ControlFlow::Wait => State::Wait {
start: Instant::now(),
},
root::ControlFlow::WaitUntil(end) => {
let start = Instant::now();
let delay = if end <= start {
Duration::from_millis(0)
} else {
end - start
};
let cloned = self.clone();
State::WaitUntil {
start,
end,
timeout: backend::Timeout::new(
move || cloned.send_event(Event::NewEvents(StartCause::Poll)),
delay,
),
}
}
root::ControlFlow::Exit => State::Exit,
};
match *self.0.runner.borrow_mut() {
Some(ref mut runner) => {
runner.state = new_state;
}
None => (),
}
}
// Check if the event loop is currently closed
fn is_closed(&self) -> bool {
match *self.0.runner.borrow() {
Some(ref runner) => runner.state.is_exit(),
None => false, // If the event loop is None, it has not been intialised yet, so it cannot be closed
}
}
// Get the current control flow state
fn current_control_flow(&self) -> root::ControlFlow {
match *self.0.runner.borrow() {
Some(ref runner) => runner.state.control_flow(),
None => root::ControlFlow::Poll,
}
}
}