gpui_macos: Fix traffic light hitbox after repositioning (#58534)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- N/A

This is a follow up to https://github.com/zed-industries/zed/pull/58169
and https://github.com/zed-industries/zed/pull/58518 after removing a
bunch of unsafe usage.

Before this, GPUI moved traffic lights by directly changing the native
button frames inside AppKit’s existing titlebar layout and the old
y-coordinate was based on the native titlebar height, so the buttons
moved visually while the titlebar tracking geometry could still be based
on the old layout.

Now the native titlebar container is resized and repositioned to contain
the traffic lights. We capture the original AppKit titlebar/button
frames, resize the titlebar container to fit the requested position,
move the native close/minimize/zoom buttons inside that container and
update AppKit tracking areas. This keeps the visible buttons and
hover/click geometry aligned.

### Before


https://github.com/user-attachments/assets/77dde6cb-3fc8-4166-bc86-22cf2c93e119

### After


https://github.com/user-attachments/assets/da84ade6-ef47-4e53-ae4a-3779315773f9

---------

Co-authored-by: Yara 🏳️‍⚧️ <git@yara.blue>

Cargo.lock

@@ -7888,7 +7888,9 @@ dependencies = [
  "media",
  "metal",
  "objc",
- "objc2-app-kit 0.3.1",
+ "objc2 0.6.3",
+ "objc2-app-kit 0.3.2",
+ "objc2-foundation 0.3.2",
  "parking_lot",
  "pathfinder_geometry",
  "raw-window-handle",
@@ -11844,11 +11846,13 @@ dependencies = [
 
 [[package]]
 name = "objc2-app-kit"
-version = "0.3.1"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e6f29f568bec459b0ddff777cec4fe3fd8666d82d5a40ebd0ff7e66134f89bcc"
+checksum = "d49e936b501e5c5bf01fda3a9452ff86dc3ea98ad5f283e1455153142d97518c"
 dependencies = [
+ "bitflags 2.10.0",
  "objc2 0.6.3",
+ "objc2-core-foundation",
  "objc2-foundation 0.3.2",
 ]
 

Cargo.toml

@@ -635,7 +635,16 @@ nix = "0.29"
 nucleo = "0.5"
 num-format = "0.4.4"
 objc = "0.2"
-objc2-app-kit = { version = "0.3", default-features = false, features = [ "NSGraphics" ] }
+objc2 = "0.6"
+objc2-app-kit = { version = "0.3.2", default-features = false, features = [
+    "NSButton",
+    "NSControl",
+    "NSGraphics",
+    "NSResponder",
+    "NSView",
+    "NSWindow",
+    "objc2-core-foundation",
+] }
 objc2-foundation = { version = "=0.3.2", default-features = false, features = [
     "NSArray",
     "NSAttributedString",

crates/gpui/Cargo.toml

@@ -132,7 +132,7 @@ foreign-types = "0.5"
 log.workspace = true
 media.workspace = true
 objc.workspace = true
-objc2 = { version = "0.6", optional = true }
+objc2 = { workspace = true, optional = true }
 objc2-metal = { version = "0.3", optional = true }
 mach2.workspace = true
 #TODO: replace with "objc2"

crates/gpui_macos/Cargo.toml

@@ -50,7 +50,9 @@ mach2.workspace = true
 media.workspace = true
 metal.workspace = true
 objc.workspace = true
+objc2.workspace = true
 objc2-app-kit.workspace = true
+objc2-foundation.workspace = true
 parking_lot.workspace = true
 pathfinder_geometry = "0.5"
 raw-window-handle = "0.6"

crates/gpui_macos/src/window.rs

@@ -12,9 +12,8 @@ use cocoa::{
         NSAppKitVersionNumber, NSAppKitVersionNumber12_0, NSApplication, NSBackingStoreBuffered,
         NSColor, NSEvent, NSEventModifierFlags, NSFilenamesPboardType, NSPasteboard, NSScreen,
         NSView, NSViewHeightSizable, NSViewWidthSizable, NSVisualEffectMaterial,
-        NSVisualEffectState, NSVisualEffectView, NSWindow, NSWindowButton,
-        NSWindowCollectionBehavior, NSWindowOcclusionState, NSWindowOrderingMode,
-        NSWindowStyleMask, NSWindowTitleVisibility,
+        NSVisualEffectState, NSVisualEffectView, NSWindow, NSWindowCollectionBehavior,
+        NSWindowOcclusionState, NSWindowOrderingMode, NSWindowStyleMask, NSWindowTitleVisibility,
     },
     base::{id, nil},
     foundation::{
@@ -39,7 +38,7 @@ use image::RgbaImage;
 use core_foundation::base::{CFRelease, CFTypeRef};
 use core_foundation_sys::base::CFEqual;
 use core_foundation_sys::number::{CFBooleanGetValue, CFBooleanRef};
-use core_graphics::display::{CGDirectDisplayID, CGPoint, CGRect};
+use core_graphics::display::{CGDirectDisplayID, CGRect};
 use ctor::ctor;
 use futures::channel::oneshot;
 use objc::{
@@ -49,7 +48,12 @@ use objc::{
     runtime::{BOOL, Class, NO, Object, Protocol, Sel, YES},
     sel, sel_impl,
 };
-use objc2_app_kit::NSBeep;
+use objc2::rc::Retained;
+use objc2_app_kit::{
+    NSBeep, NSButton as Objc2NSButton, NSView as Objc2NSView, NSWindow as Objc2NSWindow,
+    NSWindowButton as Objc2NSWindowButton,
+};
+use objc2_foundation::{NSPoint as Objc2NSPoint, NSRect as Objc2NSRect};
 use parking_lot::Mutex;
 use raw_window_handle as rwh;
 use smallvec::SmallVec;
@@ -390,6 +394,10 @@ unsafe fn build_window_class(name: &'static str, superclass: &Class) -> *const C
             sel!(windowWillExitFullScreen:),
             window_will_exit_fullscreen as extern "C" fn(&Object, Sel, id),
         );
+        decl.add_method(
+            sel!(windowDidExitFullScreen:),
+            window_did_exit_fullscreen as extern "C" fn(&Object, Sel, id),
+        );
         decl.add_method(
             sel!(windowDidMove:),
             window_did_move as extern "C" fn(&Object, Sel, id),
@@ -468,6 +476,19 @@ unsafe fn build_window_class(name: &'static str, superclass: &Class) -> *const C
     }
 }
 
+struct TrafficLightFrames {
+    titlebar: Objc2NSRect,
+    close: Objc2NSRect,
+    minimize: Objc2NSRect,
+    zoom: Objc2NSRect,
+}
+
+struct TrafficLightButtons {
+    close: Retained<Objc2NSButton>,
+    minimize: Retained<Objc2NSButton>,
+    zoom: Retained<Objc2NSButton>,
+}
+
 struct MacWindowState {
     handle: AnyWindowHandle,
     foreground_executor: ForegroundExecutor,
@@ -492,6 +513,7 @@ struct MacWindowState {
     last_key_equivalent: Option<KeyDownEvent>,
     synthetic_drag_counter: usize,
     traffic_light_position: Option<Point<Pixels>>,
+    traffic_light_frames: Option<TrafficLightFrames>,
     transparent_titlebar: bool,
     previous_modifiers_changed_event: Option<PlatformInput>,
     keystroke_for_do_command: Option<Keystroke>,
@@ -513,54 +535,121 @@ struct MacWindowState {
 }
 
 impl MacWindowState {
-    fn move_traffic_light(&self) {
+    fn move_traffic_light(&mut self) {
         if let Some(traffic_light_position) = self.traffic_light_position {
             if self.is_fullscreen() {
-                // Moving traffic lights while fullscreen doesn't work,
-                // see https://github.com/zed-industries/zed/issues/4712
+                self.restore_traffic_light();
                 return;
             }
 
-            let titlebar_height = self.titlebar_height();
-
-            unsafe {
-                let close_button: id = msg_send![
-                    self.native_window,
-                    standardWindowButton: NSWindowButton::NSWindowCloseButton
-                ];
-                let min_button: id = msg_send![
-                    self.native_window,
-                    standardWindowButton: NSWindowButton::NSWindowMiniaturizeButton
-                ];
-                let zoom_button: id = msg_send![
-                    self.native_window,
-                    standardWindowButton: NSWindowButton::NSWindowZoomButton
-                ];
-
-                let mut close_button_frame: CGRect = msg_send![close_button, frame];
-                let mut min_button_frame: CGRect = msg_send![min_button, frame];
-                let mut zoom_button_frame: CGRect = msg_send![zoom_button, frame];
-                let mut origin = point(
-                    traffic_light_position.x,
-                    titlebar_height
-                        - traffic_light_position.y
-                        - px(close_button_frame.size.height as f32),
-                );
-                let button_spacing =
-                    px((min_button_frame.origin.x - close_button_frame.origin.x) as f32);
-
-                close_button_frame.origin = CGPoint::new(origin.x.into(), origin.y.into());
-                let _: () = msg_send![close_button, setFrame: close_button_frame];
-                origin.x += button_spacing;
-
-                min_button_frame.origin = CGPoint::new(origin.x.into(), origin.y.into());
-                let _: () = msg_send![min_button, setFrame: min_button_frame];
-                origin.x += button_spacing;
-
-                zoom_button_frame.origin = CGPoint::new(origin.x.into(), origin.y.into());
-                let _: () = msg_send![zoom_button, setFrame: zoom_button_frame];
-                origin.x += button_spacing;
+            if self.traffic_light_frames.is_none() {
+                self.traffic_light_frames = self.capture_traffic_light_frames();
             }
+
+            let window_height = Pixels::from(self.native_window().frame().size.height);
+            if self.traffic_light_frames.is_some() {
+                // AppKit can recreate standard buttons, so fetch the live views for each layout pass.
+                let Some(buttons) = self.traffic_light_buttons() else {
+                    return;
+                };
+                let Some(titlebar_container) = Self::titlebar_container(&buttons.close) else {
+                    return;
+                };
+
+                let close_frame = buttons.close.frame();
+                let minimize_frame = buttons.minimize.frame();
+                let button_width = Pixels::from(close_frame.size.width);
+                let button_height = Pixels::from(close_frame.size.height);
+                let button_padding = Pixels::from(
+                    minimize_frame.origin.x - close_frame.origin.x - close_frame.size.width,
+                );
+                let container_height =
+                    button_height + traffic_light_position.y + traffic_light_position.y;
+
+                let mut titlebar_frame = titlebar_container.frame();
+                titlebar_frame.size.height = container_height.to_f64();
+                titlebar_frame.origin.y = (window_height - container_height).to_f64();
+
+                let minimize_x = traffic_light_position.x + button_width + button_padding;
+                let zoom_x = minimize_x + button_width + button_padding;
+
+                titlebar_container.setFrame(titlebar_frame);
+                buttons.close.setFrameOrigin(Objc2NSPoint::new(
+                    traffic_light_position.x.to_f64(),
+                    traffic_light_position.y.to_f64(),
+                ));
+                buttons.minimize.setFrameOrigin(Objc2NSPoint::new(
+                    minimize_x.to_f64(),
+                    traffic_light_position.y.to_f64(),
+                ));
+                buttons.zoom.setFrameOrigin(Objc2NSPoint::new(
+                    zoom_x.to_f64(),
+                    traffic_light_position.y.to_f64(),
+                ));
+
+                titlebar_container.updateTrackingAreas();
+                buttons.close.updateTrackingAreas();
+                buttons.minimize.updateTrackingAreas();
+                buttons.zoom.updateTrackingAreas();
+            }
+        }
+    }
+
+    fn capture_traffic_light_frames(&self) -> Option<TrafficLightFrames> {
+        let buttons = self.traffic_light_buttons()?;
+        let titlebar_container = Self::titlebar_container(&buttons.close)?;
+
+        Some(TrafficLightFrames {
+            titlebar: titlebar_container.frame(),
+            close: buttons.close.frame(),
+            minimize: buttons.minimize.frame(),
+            zoom: buttons.zoom.frame(),
+        })
+    }
+
+    fn native_window(&self) -> &Objc2NSWindow {
+        // SAFETY: `MacWindow::new` initializes `self.native_window` with the AppKit
+        // window for this state. It is either `NSWindow` or `NSPanel`, so borrowing it
+        // as `Objc2NSWindow` is valid here.
+        unsafe { &*self.native_window.cast::<Objc2NSWindow>() }
+    }
+
+    fn traffic_light_buttons(&self) -> Option<TrafficLightButtons> {
+        let window = self.native_window();
+        Some(TrafficLightButtons {
+            close: window.standardWindowButton(Objc2NSWindowButton::CloseButton)?,
+            minimize: window.standardWindowButton(Objc2NSWindowButton::MiniaturizeButton)?,
+            zoom: window.standardWindowButton(Objc2NSWindowButton::ZoomButton)?,
+        })
+    }
+
+    fn titlebar_container(close_button: &Objc2NSButton) -> Option<Retained<Objc2NSView>> {
+        // SAFETY: `close_button` comes from AppKit's `standardWindowButton(_:)`.
+        // Although `superview` is unsafe, objc2 returns each result as `Retained<NSView>`.
+        unsafe {
+            let button_container = close_button.superview()?;
+            button_container.superview()
+        }
+    }
+
+    fn restore_traffic_light(&mut self) {
+        if let Some(frames) = self.traffic_light_frames.take() {
+            let Some(buttons) = self.traffic_light_buttons() else {
+                return;
+            };
+            let Some(titlebar_container) = Self::titlebar_container(&buttons.close) else {
+                return;
+            };
+
+            buttons.close.setFrame(frames.close);
+            buttons.minimize.setFrame(frames.minimize);
+            buttons.zoom.setFrame(frames.zoom);
+            titlebar_container.setFrame(frames.titlebar);
+
+            titlebar_container.updateTrackingAreas();
+            buttons.close.updateTrackingAreas();
+            buttons.minimize.updateTrackingAreas();
+            buttons.zoom.updateTrackingAreas();
         }
     }
 
@@ -642,14 +731,6 @@ impl MacWindowState {
         get_scale_factor(self.native_window)
     }
 
-    fn titlebar_height(&self) -> Pixels {
-        unsafe {
-            let frame = NSWindow::frame(self.native_window);
-            let content_layout_rect: CGRect = msg_send![self.native_window, contentLayoutRect];
-            px((frame.size.height - content_layout_rect.size.height) as f32)
-        }
-    }
-
     fn window_bounds(&self) -> WindowBounds {
         if self.is_fullscreen() {
             WindowBounds::Fullscreen(self.fullscreen_restore_bounds)
@@ -821,6 +902,7 @@ impl MacWindow {
                 traffic_light_position: titlebar
                     .as_ref()
                     .and_then(|titlebar| titlebar.traffic_light_position),
+                traffic_light_frames: None,
                 transparent_titlebar: titlebar
                     .as_ref()
                     .is_none_or(|titlebar| titlebar.appears_transparent),
@@ -1737,7 +1819,7 @@ impl PlatformWindow for MacWindow {
     }
 
     fn play_system_bell(&self) {
-        unsafe { NSBeep() }
+        NSBeep()
     }
 
     #[cfg(any(test, feature = "test-support"))]
@@ -2317,6 +2399,7 @@ extern "C" fn window_will_enter_fullscreen(this: &Object, _: Sel, _: id) {
     let window_state = unsafe { get_window_state(this) };
     let mut lock = window_state.as_ref().lock();
     lock.fullscreen_restore_bounds = lock.bounds();
+    lock.restore_traffic_light();
 
     let min_version = NSOperatingSystemVersion::new(15, 3, 0);
 
@@ -2340,6 +2423,13 @@ extern "C" fn window_will_exit_fullscreen(this: &Object, _: Sel, _: id) {
     }
 }
 
+extern "C" fn window_did_exit_fullscreen(this: &Object, _: Sel, _: id) {
+    // SAFETY: This method is registered only on GPUI window classes, which initialize
+    // WINDOW_STATE_IVAR with an Arc<Mutex<MacWindowState>> during window creation.
+    let window_state = unsafe { get_window_state(this) };
+    window_state.as_ref().lock().move_traffic_light();
+}
+
 pub(crate) fn is_macos_version_at_least(version: NSOperatingSystemVersion) -> bool {
     unsafe { NSProcessInfo::processInfo(nil).isOperatingSystemAtLeastVersion(version) }
 }