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winit-web: return immediately from run_app on web

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This avoids using JavaScript exceptions to support `EventLoop::run_app`
on the web, which is a huge hack, and doesn't work with the Exception
Handling Proposal for WebAssembly:
https://github.com/WebAssembly/exception-handling

This needs the application handler passed to `run_app` to be `'static`,
but that works better on iOS too anyhow (since you can't accidentally
forget to pass in state that then wouldn't be dropped when terminating).
This commit is contained in:
Mads Marquart 2025-03-17 04:49:58 +01:00 • committed by Kirill Chibisov
parent e8bccfff4f
commit f69b601abb
9 changed files with 81 additions and 102 deletions
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7
winit-core/src/event_loop/run_on_demand.rs
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@ -12,7 +12,7 @@ pub trait EventLoopExtRunOnDemand {
/// Run the application with the event loop on the calling thread.
///
/// Unlike [`EventLoop::run_app`], this function accepts non-`'static` (i.e. non-`move`)
/// closures and it is possible to return control back to the caller without
/// state and it is possible to return control back to the caller without
/// consuming the `EventLoop` (by using [`exit()`]) and
/// so the event loop can be re-run after it has exit.
///
@ -31,8 +31,7 @@ pub trait EventLoopExtRunOnDemand {
///
/// # Caveats
/// - This extension isn't available on all platforms, since it's not always possible to return
/// to the caller (specifically this is impossible on iOS and Web - though with the Web
/// backend it is possible to use `EventLoopExtWeb::spawn_app()`[^1] more than once instead).
/// to the caller (specifically this is impossible on iOS and Web).
/// - No [`Window`] state can be carried between separate runs of the event loop.
///
/// You are strongly encouraged to use [`EventLoop::run_app()`] for portability, unless you
@ -51,8 +50,6 @@ pub trait EventLoopExtRunOnDemand {
/// are delivered via callbacks based on an event loop that is internal to the browser itself.
/// - **iOS:** It's not possible to stop and start an `UIApplication` repeatedly on iOS.
///
/// [^1]: `spawn_app()` is only available on the Web platforms.
///
/// [`exit()`]: ActiveEventLoop::exit()
/// [`set_control_flow()`]: ActiveEventLoop::set_control_flow()
fn run_app_on_demand<A: ApplicationHandler>(&mut self, app: A) -> Result<(), EventLoopError>;