From 1ae93229593194dc1e5a4c7a6d29fd02cfa93930 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Sat, 5 Oct 2024 06:19:07 -1000
Subject: [PATCH] macos: non-native fs keeps track of screen number for change
 screen comp

Fixes #2370

Comparing NSScreens directly was fragile. It appears that AppKit/Cocoa
can return different instances of NSScreen for the same screen for
unknown reasons between calls to windowDidChangeScreen. I don't fully
understand why this happens.

In any case, our comparison was not safe. Instad, we now keep track of
of the CGDirectDisplayID for each screen and compare those instead.
---
 macos/Sources/Ghostty/SurfaceView_AppKit.swift | 3 +--
 macos/Sources/Helpers/Fullscreen.swift         | 6 +++---
 macos/Sources/Helpers/NSScreen+Extension.swift | 5 +++++
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/macos/Sources/Ghostty/SurfaceView_AppKit.swift b/macos/Sources/Ghostty/SurfaceView_AppKit.swift
index a5e6b2f04..ead898bdd 100644
--- a/macos/Sources/Ghostty/SurfaceView_AppKit.swift
+++ b/macos/Sources/Ghostty/SurfaceView_AppKit.swift
@@ -325,8 +325,7 @@ extension Ghostty {
             // When the window changes screens, we need to update libghostty with the screen
             // ID. If vsync is enabled, this will be used with the CVDisplayLink to ensure
             // the proper refresh rate is going.
-            let id = (screen.deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")] as! NSNumber).uint32Value
-            ghostty_surface_set_display_id(surface, id)
+            ghostty_surface_set_display_id(surface, screen.displayID ?? 0)
         }
 
         // MARK: - NSView
diff --git a/macos/Sources/Helpers/Fullscreen.swift b/macos/Sources/Helpers/Fullscreen.swift
index 65de2f627..f5df43ec2 100644
--- a/macos/Sources/Helpers/Fullscreen.swift
+++ b/macos/Sources/Helpers/Fullscreen.swift
@@ -269,7 +269,7 @@ class NonNativeFullscreen: FullscreenStyle {
               object == window else { return }
 
         // Our screens must have changed
-        guard savedState.screen != window.screen else { return }
+        guard savedState.screenID != window.screen?.displayID else { return }
 
         // When we change screens, we simply exit fullscreen. Changing
         // screens shouldn't naturally be possible, it can only happen
@@ -337,7 +337,7 @@ class NonNativeFullscreen: FullscreenStyle {
 
     /// The state that must be saved for non-native fullscreen to exit fullscreen.
     class SavedState {
-        weak var screen: NSScreen?
+        let screenID: UInt32?
         let tabGroup: NSWindowTabGroup?
         let tabGroupIndex: Int?
         let contentFrame: NSRect
@@ -347,7 +347,7 @@ class NonNativeFullscreen: FullscreenStyle {
         init?(_ window: NSWindow) {
             guard let contentView = window.contentView else { return nil }
 
-            self.screen = window.screen
+            self.screenID = window.screen?.displayID
             self.tabGroup = window.tabGroup
             self.tabGroupIndex = window.tabGroup?.windows.firstIndex(of: window)
             self.contentFrame = window.convertToScreen(contentView.frame)
diff --git a/macos/Sources/Helpers/NSScreen+Extension.swift b/macos/Sources/Helpers/NSScreen+Extension.swift
index f5a08b524..1091436dd 100644
--- a/macos/Sources/Helpers/NSScreen+Extension.swift
+++ b/macos/Sources/Helpers/NSScreen+Extension.swift
@@ -1,6 +1,11 @@
 import Cocoa
 
 extension NSScreen {
+    /// The unique CoreGraphics display ID for this screen.
+    var displayID: UInt32? {
+        deviceDescription[NSDeviceDescriptionKey("NSScreenNumber")] as? UInt32
+    }
+
     // Returns true if the given screen has a visible dock. This isn't
     // point-in-time visible, this is true if the dock is always visible
     // AND present on this screen.