# irondash_run_loop

This crate provides a consistent, platform independent interface to system run loop.

## Getting RunLoop for current thread

```rust
let run_loop = RunLoop::current();
```

If there is no run loop associated with current thread, this will create one.
`RunLoop` is backed by platform specific implementation:

- `CFRunLoop` on iOS nad macOS
- `ALooper` on Android
- `GMainContext` on Linux
- `HWND` message loop on Windows

## Calling RunLoop from other threads

`RunLoop` is neither `Send`, nor `Sync`. All interaction with it must be carried on thread where the run loop belongs.

To interact with run loop from other threads, use `RunLoopSender`:

```rust
let run_loop = RunLoop::current();
let sender = run_loop.new_sender();

// sender is Sync, Send and Clone
thread::spawn(move||{
    println("Hello from other thread!");
    sender.send(||{
        println!("Back on RunLoop thread");
    });
});
```

At any point, without needing a `RunLoop` instance, you can request sender that
sends the closure to main thread. For this to work on all platforms your Dart
application must depend on the `irondash_engine_context` plugin.

```rust
thread::spawn(move||{
    let sender = RunLoop::sender_for_main_thread().unwrap();
    sender.send(||{
        println!("Back on main thread");
        // run_loop is main thread run loop
        let run_loop = RunLoop::current();
    });
});
```

Depending on `irondash_engine_context` plugin is necessary because the Rust
code may be part of FFI plugin that gets loaded from UI thread or other background isolate, and on some platforms it is not possible to jump back to main thread without having some preparation done on main thread first (which is facilitated by the native code part of `irondash_engine_context` plugin).

If you want to use `RunLoop` without `irondash_engine_context` plugin, you can call `RunLoop::set_main_thread()` on the main thread as the very first method on the `RunLoop`.

## Scheduling timers

`RunLoop` can also be used to schedule delayed execution of closures:

```rust
let run_loop = RunLoop::current();
let handle = run_loop.schedule(Duration::from_secs(10), || {
    println!("This will be printed after 10 seconds");
});
```

`RunLoop::schedule` returns a `Handle` instance. If handle is dropped before
timer executes, timer will be cancelled. If you don't want that, call `detach`
on the handle:

```rust
let run_loop = RunLoop::current();
self.run_loop(Duration::from_secs(10), || {
    println!("This will be printed after 10 seconds");
}).detach();
```

You can also call `handle.cancel()` to cancel the timer without dropping the
handle.

Timers do not repeat. Every scheduled timer will be executed at most once.

## Async support

`RunLoop` can be used as future executor:

```rust
RunLoop::current().spawn(async move ||{
    RunLoop::current().wait(Duration::from_secs(10)).await;
    println("After 10 second delay");
});

// or use crate::spawn variant:

spawn(async move ||{
    RunLoop::current().wait(Duration::from_secs(10)).await;
    println("After 10 second delay");
});
```

Because futures are executed on single thread to which the `RunLoop` belongs, they do not
need to be `Send`.

## What exactly is main tread?

This slightly varies per platform.

- On iOS and macOS, it is the very first thread created when application is launched. It is the thread for which `pthread_main_np()` returns 1.
- On Linux, for the purpose of RunLoop, main thread is the very first thread similar to iOS and macOS.
- On Android, there is a concept of main thread (i.e. `Looper.getMainLooper()`).
- On Windows, main thread is the first thread created when application was launched, similar to macOS and iOS. If you create windows and pump the message loop on
different thread, `RunLoop::sender_for_main_thread()` will not work as expected.