From 04b38aec873f43de5793a969bcb6e33d9c309d13 Mon Sep 17 00:00:00 2001
From: osy <50960678+osy@users.noreply.github.com>
Date: Sat, 19 Sep 2026 23:37:09 -0500
Subject: [PATCH] display: turn off Hot Corners while a VM is in full screen

A guest in full screen owns the whole display, and its own corners are
commonly used (Start button, Show Desktop, Apple menu). Moving the pointer
there also triggered the Hot Corner configured on the host, e.g. Quick Note
or Mission Control popping up over the guest.

macOS 27 adds NSApplication.PresentationOptions.disableScreenCornerInteractions,
which we now request for the full screen space. The camera housing mode
forces its own options and has to carry the flag over.

On macOS 27.0 the window server keeps the corners disabled for the app after
the full screen space is gone, even though AppKit reports no options, until
the options change again. Reset them when leaving full screen.

Nothing is done for a captured mouse: the pointer is detached from the
cursor and parked in the middle of the screen, so it never reaches a corner.

Assisted-by: Claude:claude-fable-5-1
---
 Platform/macOS/Display/VMDisplayWindow.swift  | 19 ++++++++++++++++++-
 .../Display/VMDisplayWindowController.swift   |  7 ++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/Platform/macOS/Display/VMDisplayWindow.swift b/Platform/macOS/Display/VMDisplayWindow.swift
index d10dde30..381f335a 100644
--- a/Platform/macOS/Display/VMDisplayWindow.swift
+++ b/Platform/macOS/Display/VMDisplayWindow.swift
@@ -108,6 +108,7 @@ class VMDisplayWindow: NSWindow {
         center.addObserver(self, selector: #selector(updateMenuBarHidden), name: NSWindow.didResizeNotification, object: self)
         center.addObserver(self, selector: #selector(willLeaveFullScreen), name: NSWindow.willExitFullScreenNotification, object: self)
         center.addObserver(self, selector: #selector(willLeaveFullScreen), name: NSWindow.willCloseNotification, object: self)
+        center.addObserver(self, selector: #selector(didExitFullScreen), name: NSWindow.didExitFullScreenNotification, object: self)
         center.addObserver(self, selector: #selector(menuBarRevealDidChange), name: MenuBarReveal.didChangeNotification, object: nil)
         center.addObserver(self, selector: #selector(otherWindowDidChangeOcclusionState), name: NSWindow.didChangeOcclusionStateNotification, object: nil)
         center.addObserver(self, selector: #selector(updatePresentationOptions), name: NSWindow.didBecomeKeyNotification, object: self)
@@ -171,6 +172,18 @@ class VMDisplayWindow: NSWindow {
         showMenuBar()
     }
 
+    @objc private func didExitFullScreen() {
+        guard #available(macOS 27, *) else {
+            return
+        }
+        // the window server keeps Hot Corners disabled after the full screen space is gone, until the options change
+        guard NSApp.presentationOptions.isEmpty else {
+            return // another full screen window is in front and still wants them disabled
+        }
+        NSApp.presentationOptions = [.autoHideDock]
+        NSApp.presentationOptions = []
+    }
+
     /// Hides the menu bar of our full screen space if and only if we are covered by it.
     @objc private func updateMenuBarHidden() {
         if isInFullScreenSpace, let screen = screen, frame != screen.frame {
@@ -226,7 +239,11 @@ class VMDisplayWindow: NSWindow {
         // the menu bar is only kept hidden for the space we are in, but what we did must be undone in any case
         let options: NSApplication.PresentationOptions?
         if !isMenuBarRevealAllowed && isKeyWindow {
-            options = [.fullScreen, .hideMenuBar, .hideDock]
+            var forcedOptions: NSApplication.PresentationOptions = [.fullScreen, .hideMenuBar, .hideDock]
+            if #available(macOS 27, *) {
+                forcedOptions.formUnion(revealableOptions.intersection(.disableScreenCornerInteractions))
+            }
+            options = forcedOptions
             isPresentationOptionsForced = true
         } else if isPresentationOptionsForced {
             options = revealableOptions
diff --git a/Platform/macOS/Display/VMDisplayWindowController.swift b/Platform/macOS/Display/VMDisplayWindowController.swift
index 8d768cdb..e7086c80 100644
--- a/Platform/macOS/Display/VMDisplayWindowController.swift
+++ b/Platform/macOS/Display/VMDisplayWindowController.swift
@@ -419,7 +419,12 @@ class VMDisplayWindowController: NSWindowController, UTMVirtualMachineDelegate {
 
 extension VMDisplayWindowController: NSWindowDelegate {
     func window(_ window: NSWindow, willUseFullScreenPresentationOptions proposedOptions: NSApplication.PresentationOptions = []) -> NSApplication.PresentationOptions {
-        return proposedOptions.union([.autoHideToolbar])
+        var options = proposedOptions.union([.autoHideToolbar])
+        if #available(macOS 27, *) {
+            // the guest owns the whole screen, so its corners should not trigger Hot Corners on the host
+            options.insert(.disableScreenCornerInteractions)
+        }
+        return options
     }
     
     func windowShouldClose(_ sender: NSWindow) -> Bool {