display(apple): fix screenshot for apple display

Author: osy

Platform/macOS/Display/VMDisplayAppleDisplayWindowController.swift

@@ -22,7 +22,11 @@ class VMDisplayAppleDisplayWindowController: VMDisplayAppleWindowController {
     var appleView: VZVirtualMachineView! {
         mainView as? VZVirtualMachineView
     }
-    
+
+    override var contentView: NSView? {
+        appleView
+    }
+
     var supportsReconfiguration: Bool {
         guard #available(macOS 14, *) else {
             return false

Platform/macOS/Display/VMDisplayAppleTerminalWindowController.swift

@@ -21,7 +21,11 @@ class VMDisplayAppleTerminalWindowController: VMDisplayAppleWindowController, VM
     var terminalView: TerminalView! {
         mainView as? TerminalView
     }
-    
+
+    override var contentView: NSView? {
+        terminalView
+    }
+
     var serialConfig: UTMAppleConfigurationSerial! {
         appleConfig.serials[index]
     }

Platform/macOS/Display/VMDisplayAppleWindowController.swift

@@ -18,7 +18,11 @@ import Foundation
 
 class VMDisplayAppleWindowController: VMDisplayWindowController {
     var mainView: NSView?
-    
+
+    var contentView: NSView? {
+        nil
+    }
+
     var isInstallSuccessful: Bool = false
 
     var appleVM: UTMAppleVirtualMachine! {
@@ -402,7 +406,7 @@ extension VMDisplayAppleWindowController {
 
 extension VMDisplayAppleWindowController: UTMScreenshotProvider {
     var screenshot: UTMVirtualMachineScreenshot? {
-        if let image = mainView?.image() {
+        if let image = contentView?.image() {
             return UTMVirtualMachineScreenshot(wrapping: image)
         } else {
             return nil