Struct MainThreadToken 

pub struct MainThreadToken(/* private fields */);

A witness of execution that exists solely on a designated “Main Thread”.

In FFI contexts, many libraries (especially legacy C++ or UI frameworks) are not thread-safe and must only be initialized, called, or dropped from the same thread that originally created them.

MainThreadToken is a zero-sized proof carrier. Possessing it proves (at a type-system level) that the holder previously executed on the designated main thread. The PhantomData<*mut ()> makes the token !Send + !Sync, so a token obtained on the main thread cannot leak to another thread through ordinary safe code.

Implementations

impl MainThreadToken

pub unsafe fn new_unchecked() -> Self

Create a new MainThreadToken without verifying the current thread.

Safety

The caller must guarantee that:

1. They are executing on the thread that was (or will be) passed to designate_main_thread, and
2. The resulting token will not be transmitted to another thread through unsafe channels (the type is !Send + !Sync, which prevents safe channels from doing so).

pub fn try_new() -> Option<Self>

Obtain a token if the current thread matches the one previously passed to designate_main_thread.

Returns None if designate_main_thread has never been called, or if the current thread is not the designated main thread.

Trait Implementations

impl Clone for MainThreadToken

fn clone(&self) -> MainThreadToken

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MainThreadToken

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for MainThreadToken

fn eq(&self, other: &MainThreadToken) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for MainThreadToken

impl Eq for MainThreadToken

impl StructuralPartialEq for MainThreadToken