# NSTitlebarAccessoryViewController An object that manages a custom view—known as an accessory view—in the title bar–toolbar area of a window. ``` class NSTitlebarAccessoryViewController ``` ## Overview Because a title bar accessory view controller is contained in a visual effect view (that is, [`NSVisualEffectView`](/documentation/AppKit/NSVisualEffectView)), it automatically handles the blur behind the accessory view and the size and location changes for the content of the view when a window goes in and out of full screen mode. If you’re currently using [`NSToolbar`](/documentation/AppKit/NSToolbar) fullscreen accessory APIs, such as [`fullScreenAccessoryView`](/documentation/AppKit/NSToolbar/fullScreenAccessoryView), you should use [`NSTitlebarAccessoryViewController`](/documentation/AppKit/NSTitlebarAccessoryViewController) APIs instead. Typically, you create an `NSTitlebarAccessoryViewController` object, give it your custom view, set the [`layoutAttribute`](/documentation/AppKit/NSTitlebarAccessoryViewController/layoutAttribute) property to ensure that it displays correctly in relation to the title bar, and add the view controller to your window. For more information about [`NSWindow`](/documentation/AppKit/NSWindow) methods you can use to add and remove a title bar accessory view controller, see Managing Title Bars. Don’t override the `view` property in your `NSTitlebarAccessoryViewController` subclass. Instead, you can override [`loadView()`](/documentation/AppKit/NSViewController/loadView()), and set the `view` property in that method. > Note: > `NSTitlebarAccessoryViewController` observes the view’s frame for changes. Depending on the value of ``doc://com.apple.appkit/documentation/AppKit/NSTitlebarAccessoryViewController/layoutAttribute``, you can change either the height or the width of the view. Specifically, you can change the view’s height when ``doc://com.apple.appkit/documentation/AppKit/NSTitlebarAccessoryViewController/layoutAttribute`` is , and you can change the view’s width when the ``doc://com.apple.appkit/documentation/AppKit/NSTitlebarAccessoryViewController/layoutAttribute`` is or . The remaining size direction is automatically set to the maximum size as required for the window. ## Topics ### Configuring a title bar accessory view controller [`fullScreenMinHeight`](/documentation/AppKit/NSTitlebarAccessoryViewController/fullScreenMinHeight) The visual minimum height of an accessory view that displays below the title bar when the window is in full screen mode. [`layoutAttribute`](/documentation/AppKit/NSTitlebarAccessoryViewController/layoutAttribute) The location of the accessory view, in relation to the window’s title bar. ### Configuring the scroll edge effect [`preferredScrollEdgeEffectStyle`](/documentation/AppKit/NSTitlebarAccessoryViewController/preferredScrollEdgeEffectStyle) The titlebar accessory’s preferred effect for content scrolling behind it. [`NSScrollEdgeEffectStyle`](/documentation/AppKit/NSScrollEdgeEffectStyle) Styles for a scroll view’s edge effect. ### Responding to view events [`viewDidAppear()`](/documentation/AppKit/NSTitlebarAccessoryViewController/viewDidAppear()) Called when the title bar accessory view controller’s view is fully transitioned onto the screen. [`viewDidDisappear()`](/documentation/AppKit/NSTitlebarAccessoryViewController/viewDidDisappear()) Called after the title bar accessory view controller’s view is removed from the window’s view hierarchy. [`viewWillAppear()`](/documentation/AppKit/NSTitlebarAccessoryViewController/viewWillAppear()) Called after the title bar accessory view controller’s view has been loaded into memory is about to be added to the view hierarchy in the window. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)