[MacOS] Close a invisible window cause segment fault.

[kaiwk]

The code is modified from examples/multiwindow.rs, and reproduction is simple:

1. press 'a' will add an invisible window;
2. press 'x' will remove all windows except current window (which receives key events), then a segment fault throwed.

use std::collections::HashMap;

use simple_logger::SimpleLogger;
use winit::{
    event::{ElementState, Event, KeyboardInput, VirtualKeyCode, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    window::Window,
};

fn main() {
    SimpleLogger::new().init().unwrap();
    let event_loop = EventLoop::new();

    let mut windows = HashMap::new();
    let window = Window::new(&event_loop).unwrap();
    windows.insert(window.id(), window);

    event_loop.run(move |event, event_loop, control_flow| {
        *control_flow = ControlFlow::Wait;

        match event {
            Event::WindowEvent { event, window_id } => {
                match event {
                    WindowEvent::CloseRequested => {
                        println!("Window {:?} has received the signal to close", window_id);

                        // This drops the window, causing it to close.
                        windows.remove(&window_id);

                        if windows.is_empty() {
                            *control_flow = ControlFlow::Exit;
                        }
                    }
                    WindowEvent::KeyboardInput {
                        input:
                            KeyboardInput {
                                state: ElementState::Pressed,
                                virtual_keycode: Some(VirtualKeyCode::A),
                                ..
                            },
                        ..
                    } => {
                        let window = Window::new(&event_loop).unwrap();
                        window.set_visible(false);
                        windows.insert(window.id(), window);
                    }
                    WindowEvent::KeyboardInput {
                        input:
                            KeyboardInput {
                                state: ElementState::Pressed,
                                virtual_keycode: Some(VirtualKeyCode::X),
                                ..
                            },
                        ..
                    } => {
                        windows.retain(|id, _| *id == window_id);
                    }
                    _ => (),
                }
            }
            _ => (),
        }
    })
}

I guess it's related to #158?

[kaiwk]

From the nswindow doc, even for invisible window, nswindow.close() should post NSWindowWillCloseNotification, but looks like window_will_close is not triggtered from the trace log.

For example, when the application terminates, it sends the close message to all windows in its window list, even those that are not currently visible.

[kaiwk]

It seems window delegate drops before NSWindow somehow, one quick dirty fix is here.

[ArturKovacs]

Please check if this is fixed on the master currently. I believe this was fixed by #1874.

[kaiwk]

Thanks, I tested it and it works.