pub trait EventLoopExtRunReturn {
    type UserEvent;

    // Required method
    fn run_return<F>(&mut self, event_handler: F) -> i32
       where F: FnMut(Event<'_, Self::UserEvent>, &EventLoopWindowTarget<Self::UserEvent>, &mut ControlFlow);
Expand description

Additional methods on EventLoop to return control flow to the caller.

Required Associated Types§


type UserEvent

A type provided by the user that can be passed through Event::UserEvent.

Required Methods§


fn run_return<F>(&mut self, event_handler: F) -> i32where F: FnMut(Event<'_, Self::UserEvent>, &EventLoopWindowTarget<Self::UserEvent>, &mut ControlFlow),

Initializes the winit event loop.

Unlike EventLoop::run, this function accepts non-'static (i.e. non-move) closures and returns control flow to the caller when control_flow is set to ControlFlow::Exit.


Despite its appearance at first glance, this is not a perfect replacement for poll_events. For example, this function will not return on Windows or macOS while a window is getting resized, resulting in all application logic outside of the event_handler closure not running until the resize operation ends. Other OS operations may also result in such freezes. This behavior is caused by fundamental limitations in the underlying OS APIs, which cannot be hidden by winit without severe stability repercussions.

You are strongly encouraged to use run, unless the use of this is absolutely necessary.

  • X11 / Wayland: This function returns 1 upon disconnection from the display server.