This code describes a mechanism to adjust traffic light positioning on MacOS with Tauri 2.x

tauri_traffic_light_positioner_plugin.rs

use objc::{msg_send, sel, sel_impl};
use rand::{distributions::Alphanumeric, Rng};
use tauri::{
    plugin::{Builder, TauriPlugin},
    Manager, Runtime, Window,
}; // 0.8

const WINDOW_CONTROL_PAD_X: f64 = 15.0;
const WINDOW_CONTROL_PAD_Y: f64 = 23.0;

struct UnsafeWindowHandle(*mut std::ffi::c_void);
unsafe impl Send for UnsafeWindowHandle {}
unsafe impl Sync for UnsafeWindowHandle {}

pub fn init<R: Runtime>() -> TauriPlugin<R> {
    Builder::new("traffic_light_positioner")
        .on_window_ready(|window| {
            #[cfg(target_os = "macos")]
            setup_traffic_light_positioner(window);
            return;
        })
        .build()
}

#[cfg(target_os = "macos")]
fn position_traffic_lights(ns_window_handle: UnsafeWindowHandle, x: f64, y: f64) {
    use cocoa::appkit::{NSView, NSWindow, NSWindowButton};
    use cocoa::foundation::NSRect;
    let ns_window = ns_window_handle.0 as cocoa::base::id;
    unsafe {
        let close = ns_window.standardWindowButton_(NSWindowButton::NSWindowCloseButton);
        let miniaturize =
            ns_window.standardWindowButton_(NSWindowButton::NSWindowMiniaturizeButton);
        let zoom = ns_window.standardWindowButton_(NSWindowButton::NSWindowZoomButton);

        let title_bar_container_view = close.superview().superview();

        let close_rect: NSRect = msg_send![close, frame];
        let button_height = close_rect.size.height;

        let title_bar_frame_height = button_height + y;
        let mut title_bar_rect = NSView::frame(title_bar_container_view);
        title_bar_rect.size.height = title_bar_frame_height;
        title_bar_rect.origin.y = NSView::frame(ns_window).size.height - title_bar_frame_height;
        let _: () = msg_send![title_bar_container_view, setFrame: title_bar_rect];

        let window_buttons = vec![close, miniaturize, zoom];
        let space_between = NSView::frame(miniaturize).origin.x - NSView::frame(close).origin.x;

        for (i, button) in window_buttons.into_iter().enumerate() {
            let mut rect: NSRect = NSView::frame(button);
            rect.origin.x = x + (i as f64 * space_between);
            button.setFrameOrigin(rect.origin);
        }
    }
}

#[cfg(target_os = "macos")]
#[derive(Debug)]
struct WindowState<R: Runtime> {
    window: Window<R>,
}

#[cfg(target_os = "macos")]
pub fn setup_traffic_light_positioner<R: Runtime>(window: Window<R>) {
    use cocoa::appkit::NSWindow;
    use cocoa::base::{id, BOOL};
    use cocoa::foundation::NSUInteger;
    use objc::runtime::{Object, Sel};
    use std::ffi::c_void;

    // Do the initial positioning
    position_traffic_lights(
        UnsafeWindowHandle(window.ns_window().expect("Failed to create window handle")),
        WINDOW_CONTROL_PAD_X,
        WINDOW_CONTROL_PAD_Y,
    );

    // Ensure they stay in place while resizing the window.
    fn with_window_state<R: Runtime, F: FnOnce(&mut WindowState<R>) -> T, T>(
        this: &Object,
        func: F,
    ) {
        let ptr = unsafe {
            let x: *mut c_void = *this.get_ivar("app_box");
            &mut *(x as *mut WindowState<R>)
        };
        func(ptr);
    }

    unsafe {
        let ns_win = window
            .ns_window()
            .expect("NS Window should exist to mount traffic light delegate.")
            as id;

        let current_delegate: id = ns_win.delegate();

        extern "C" fn on_window_should_close(this: &Object, _cmd: Sel, sender: id) -> BOOL {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                msg_send![super_del, windowShouldClose: sender]
            }
        }
        extern "C" fn on_window_will_close(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowWillClose: notification];
            }
        }
        extern "C" fn on_window_did_resize<R: Runtime>(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                with_window_state(&*this, |state: &mut WindowState<R>| {
                    let id = state
                        .window
                        .ns_window()
                        .expect("NS window should exist on state to handle resize")
                        as id;

                    #[cfg(target_os = "macos")]
                    position_traffic_lights(
                        UnsafeWindowHandle(id as *mut std::ffi::c_void),
                        WINDOW_CONTROL_PAD_X,
                        WINDOW_CONTROL_PAD_Y,
                    );
                });

                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidResize: notification];
            }
        }
        extern "C" fn on_window_did_move(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidMove: notification];
            }
        }
        extern "C" fn on_window_did_change_backing_properties(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidChangeBackingProperties: notification];
            }
        }
        extern "C" fn on_window_did_become_key(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidBecomeKey: notification];
            }
        }
        extern "C" fn on_window_did_resign_key(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidResignKey: notification];
            }
        }
        extern "C" fn on_dragging_entered(this: &Object, _cmd: Sel, notification: id) -> BOOL {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                msg_send![super_del, draggingEntered: notification]
            }
        }
        extern "C" fn on_prepare_for_drag_operation(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) -> BOOL {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                msg_send![super_del, prepareForDragOperation: notification]
            }
        }
        extern "C" fn on_perform_drag_operation(this: &Object, _cmd: Sel, sender: id) -> BOOL {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                msg_send![super_del, performDragOperation: sender]
            }
        }
        extern "C" fn on_conclude_drag_operation(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, concludeDragOperation: notification];
            }
        }
        extern "C" fn on_dragging_exited(this: &Object, _cmd: Sel, notification: id) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, draggingExited: notification];
            }
        }
        extern "C" fn on_window_will_use_full_screen_presentation_options(
            this: &Object,
            _cmd: Sel,
            window: id,
            proposed_options: NSUInteger,
        ) -> NSUInteger {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                msg_send![super_del, window: window willUseFullScreenPresentationOptions: proposed_options]
            }
        }
        extern "C" fn on_window_did_enter_full_screen<R: Runtime>(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                with_window_state(&*this, |state: &mut WindowState<R>| {
                    state
                        .window
                        .emit("did-enter-fullscreen", ())
                        .expect("Failed to emit event");
                });

                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidEnterFullScreen: notification];
            }
        }
        extern "C" fn on_window_will_enter_full_screen<R: Runtime>(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                with_window_state(&*this, |state: &mut WindowState<R>| {
                    state
                        .window
                        .emit("will-enter-fullscreen", ())
                        .expect("Failed to emit event");
                });

                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowWillEnterFullScreen: notification];
            }
        }
        extern "C" fn on_window_did_exit_full_screen<R: Runtime>(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                with_window_state(&*this, |state: &mut WindowState<R>| {
                    state
                        .window
                        .emit("did-exit-fullscreen", ())
                        .expect("Failed to emit event");

                    let id = state.window.ns_window().expect("Failed to emit event") as id;
                    position_traffic_lights(
                        UnsafeWindowHandle(id as *mut std::ffi::c_void),
                        WINDOW_CONTROL_PAD_X,
                        WINDOW_CONTROL_PAD_Y,
                    );
                });

                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidExitFullScreen: notification];
            }
        }
        extern "C" fn on_window_will_exit_full_screen<R: Runtime>(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                with_window_state(&*this, |state: &mut WindowState<R>| {
                    state
                        .window
                        .emit("will-exit-fullscreen", ())
                        .expect("Failed to emit event");
                });

                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowWillExitFullScreen: notification];
            }
        }
        extern "C" fn on_window_did_fail_to_enter_full_screen(
            this: &Object,
            _cmd: Sel,
            window: id,
        ) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, windowDidFailToEnterFullScreen: window];
            }
        }
        extern "C" fn on_effective_appearance_did_change(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![super_del, effectiveAppearanceDidChange: notification];
            }
        }
        extern "C" fn on_effective_appearance_did_changed_on_main_thread(
            this: &Object,
            _cmd: Sel,
            notification: id,
        ) {
            unsafe {
                let super_del: id = *this.get_ivar("super_delegate");
                let _: () = msg_send![
                    super_del,
                    effectiveAppearanceDidChangedOnMainThread: notification
                ];
            }
        }

        // Are we deallocing this properly ? (I miss safe Rust :(  )
        let window_label = window.label().to_string();

        let app_state = WindowState { window };
        let app_box = Box::into_raw(Box::new(app_state)) as *mut c_void;
        let random_str: String = rand::thread_rng()
            .sample_iter(&Alphanumeric)
            .take(20)
            .map(char::from)
            .collect();
        
        // We need to ensure we have a unique delegate name, otherwise we will panic while trying to create a duplicate
        // delegate with the same name.
        let delegate_name = format!("windowDelegate_{}_{}", window_label, random_str);

        ns_win.setDelegate_(delegate!(&delegate_name, {
            window: id = ns_win,
            app_box: *mut c_void = app_box,
            toolbar: id = cocoa::base::nil,
            super_delegate: id = current_delegate,
            (windowShouldClose:) => on_window_should_close as extern fn(&Object, Sel, id) -> BOOL,
            (windowWillClose:) => on_window_will_close as extern fn(&Object, Sel, id),
            (windowDidResize:) => on_window_did_resize::<R> as extern fn(&Object, Sel, id),
            (windowDidMove:) => on_window_did_move as extern fn(&Object, Sel, id),
            (windowDidChangeBackingProperties:) => on_window_did_change_backing_properties as extern fn(&Object, Sel, id),
            (windowDidBecomeKey:) => on_window_did_become_key as extern fn(&Object, Sel, id),
            (windowDidResignKey:) => on_window_did_resign_key as extern fn(&Object, Sel, id),
            (draggingEntered:) => on_dragging_entered as extern fn(&Object, Sel, id) -> BOOL,
            (prepareForDragOperation:) => on_prepare_for_drag_operation as extern fn(&Object, Sel, id) -> BOOL,
            (performDragOperation:) => on_perform_drag_operation as extern fn(&Object, Sel, id) -> BOOL,
            (concludeDragOperation:) => on_conclude_drag_operation as extern fn(&Object, Sel, id),
            (draggingExited:) => on_dragging_exited as extern fn(&Object, Sel, id),
            (window:willUseFullScreenPresentationOptions:) => on_window_will_use_full_screen_presentation_options as extern fn(&Object, Sel, id, NSUInteger) -> NSUInteger,
            (windowDidEnterFullScreen:) => on_window_did_enter_full_screen::<R> as extern fn(&Object, Sel, id),
            (windowWillEnterFullScreen:) => on_window_will_enter_full_screen::<R> as extern fn(&Object, Sel, id),
            (windowDidExitFullScreen:) => on_window_did_exit_full_screen::<R> as extern fn(&Object, Sel, id),
            (windowWillExitFullScreen:) => on_window_will_exit_full_screen::<R> as extern fn(&Object, Sel, id),
            (windowDidFailToEnterFullScreen:) => on_window_did_fail_to_enter_full_screen as extern fn(&Object, Sel, id),
            (effectiveAppearanceDidChange:) => on_effective_appearance_did_change as extern fn(&Object, Sel, id),
            (effectiveAppearanceDidChangedOnMainThread:) => on_effective_appearance_did_changed_on_main_thread as extern fn(&Object, Sel, id)
        }))
    }
}

Hi, thank for great gist

I got error about ns_win.setDelegate_(delegate!(&delegate_name, {}, do you know how to fixed it? I'm in latest tauri v2 beta

My cargo.toml

[target.'cfg(target_os = "macos")'.dependencies]
cocoa = "0.25.0"
objc = "0.2.7"
rand = "0.8.5"

@reyamir You'll need this in your main rust entrypoint (lib.rs for me)

#[cfg(target_os = "macos")]
#[macro_use]
extern crate cocoa;

#[cfg(target_os = "macos")]
#[macro_use]
extern crate objc;

AFAIK you can only add a #[macro_use] in the top level of your crate, so it doesn't really fit into the single file of this gist.

Hi, thank you
It worked on my project now

Hi, I've found another issue,
When my app is running, if I switch to dark mode, the traffic light position will be reset