So if I create an Alias of a folder in Finder and hand the alias to my app (I also moved the alias file to a new folder, but I did not move the original folder)...so then my app resolves the alias using: NSURL +URLByResolvingAliasFileAtURL: What happens? The resolved URL points to a completely different folder. Well not completely different. It resolves to a folder that happens to share same last path component as the original folder...but this folder is inside the same parent folder the alias file is in. It does not resolve to the original folder I created the alias of. So then once my app touches the alias with +URLByResolvingAliasFileAtURL: the alias now resolves to this new (wrong) location (even in Finder). Couple details: My app is not sandboxed. I have permission to access the original folder in my app (but even if I didn't the alias shouldn't be mutated just by merely resolving it). Only seems to happen if the folder I move the alias to happens to contain a sibling folder that has the same title as the original folder. Like it's just deleting the last path component of the alias and then appending the last path component of the original filename and just going with that. I hope that makes sense. I tried creating the alias myself using -bookmarkDataWithOptions: and going the other way (to Finder) but Finder must be resolving the alias using a different API because it resolves to the original location as expected.

Is anyone else getting new warning about menu items with submenus when running on Tahoe? I'm getting big performance problems using my menu as well as seeing these messages and I'm wondering if there's a connection. My app is faceless with a NSStatusItem with an NSMenu. Specifically it's my own subclass of NSMenu where I have a lot of code to manage the menu's dynamic behavior. This code is directly in the menu subclass instead of in a controller because the app I forked had it this way, a little wacky but I don't see it being a problem. A nib defines the contents of the menu, and it's instantiated manually with code like: var nibObjects: NSArray? = [] guard let nib = NSNib(nibNamed: "AppMenu", bundle: nil) else { ... } guard nib.instantiate(withOwner: owner, topLevelObjects: &nibObjects) else { ... } guard let menu = nibObjects?.compactMap({ $0 as? Self }).first else { ... } Within that nib.instantiate call I see a warning logged that seems new to Tahoe, before the menu's awakeFromNib is called, that says (edited): Internal inconsistency in menus - menu <NSMenu: 0x6000034e5340> believes it has <My_StatusItem_App.AppMenu: 0x7f9570c1a440> as a supermenu, but the supermenu does not seem to have any item with that submenu My_StatusItem_App.AppMenu: 0x7f9570c1a440 is my menu belonging to the NSStatusItem, NSMenu: 0x6000034e5340 is the submenu of one of its menu items. At a breakpoint in the NSMenu subclass's awakeFromNib I print self and see clear evidence of the warning's incorrectness. Below is a snippet of the console including the full warning, only edited for clarity and brevity. It shows on line 32 menu item with placeholder title "prototype batch item" that indeed has that submenu. Internal inconsistency in menus - menu <NSMenu: 0x6000034e5340> Title: Supermenu: 0x7f9570c1a440 (My StatusItem App), autoenable: YES Previous menu: 0x0 (None) Next menu: 0x0 (None) Items: ( "<NSMenuItem: 0x6000010e4fa0 Do The Thing Again, ke mask='<none>'>", "<NSMenuItem: 0x6000010e5040 Customize\U2026, ke mask='<none>'>", "<NSMenuItem: 0x6000010e50e0, ke mask='<none>'>" ) believes it has <My_StatusItem_App.AppMenu: 0x7f9570c1a440> Title: My StatusItem App Supermenu: 0x0 (None), autoenable: YES Previous menu: 0x0 (None) Next menu: 0x0 (None) Items: ( ) as a supermenu, but the supermenu does not seem to have any item with that submenu (lldb) po self <My_StatusItem_App.AppMenu: 0x7f9570c1a440> Title: My StatusItem App Supermenu: 0x0 (None), autoenable: YES Previous menu: 0x0 (None) Next menu: 0x0 (None) Items: ( "<NSMenuItem: 0x6000010fd7c0 About My StatusItem App\U2026, ke mask='<none>', action: showAbout:, action image: info.circle>", "<NSMenuItem: 0x6000010fd860 Show Onboarding Window\U2026, ke mask='Shift', action: showIntro:>", "<NSMenuItem: 0x6000010fd900 Update Available\U2026, ke mask='<none>', action: installUpdate:, standard image: icloud.and.arrow.down, hidden>", "<NSMenuItem: 0x6000010e46e0, ke mask='<none>'>", "<NSMenuItem: 0x6000010e4780 Start The Thing, ke mask='<none>', action: startTheThing:>", "<NSMenuItem: 0x6000010e4dc0 \U2318-\U232b key detector item, ke mask='<none>', view: <My_StatusItem_App.KeyDetectorView: 0x7f9570c1a010>>", "<NSMenuItem: 0x6000010e4e60, ke mask='<none>'>", "<NSMenuItem: 0x6000010e4f00 saved batches heading item, ke mask='<none>', view: <NSView: 0x7f9570b4be10>, hidden>", "<My_StatusItem_App.BatchMenuItem: 0x6000016e02c0 prototype batch item, ke mask='<none>', action: replaySavedBatch:, submenu: 0x6000034e5340 ()>", "<NSMenuItem: 0x6000010f7d40, ke mask='<none>'>", "<My_StatusItem_App.ClipMenuItem: 0x7f956ef14fd0 prototype copy clip item, ke mask='<none>', action: copyClip:>", "<NSMenuItem: 0x6000010fa620 Settings\U2026, ke='Command-,', action: showSettings:>", "<NSMenuItem: 0x6000010fa6c0, ke mask='<none>'>", "<NSMenuItem: 0x6000010fa760 Quit My StatusItem App, ke='Command-Q', action: quit:>" ) Is this seemingly incorrect inconsistency message harmless? Am I only grasping at straws to think it has some connection to the performance issues with this menu?

When I end editing pressing the escape key, the system sometimes plays NSBeep(). I noticed this with NSBrowser. Every time I press escape to end editing the system beeps. At first I thought it was somewhere in my app but I set a symbolic breakpoint and discovered it was not coming from my code. I filed FB22127038. Since then I discovered that NSBeep playing at inappropriate times is not exclusive to NSBrowser. It appears if there is a NSTableView in the window and you just press the escape key (even if you aren't editing anything) AppKit beeps. It can be traced to: #0 0x0000000199e3184c in NSBeep () #1 0x000000019aa03fac in -[NSWindow doCommandBySelector:] () #2 0x000000019ac1d01c in -[NSTableView(NSTableViewViewBased) cancelOperation:] ()

I get warnings like this on each project I build while debugging.. Internal inconsistency in menus - menu <NSMenu: 0x8b4b49ec0> Title: Help Supermenu: 0x8b4b49f80 (Main Menu), autoenable: YES Previous menu: 0x0 (None) Next menu: 0x0 (None) Items: ( "<NSMenuItem: 0x8b5771720 Metal4C Help, ke='Command-?'>" ) believes it has <NSMenu: 0x8b4b49f80> Title: Main Menu Supermenu: 0x0 (None), autoenable: YES Previous menu: 0x0 (None) Next menu: 0x0 (None) Items: ( ) as a supermenu, but the supermenu does not seem to have any item with that submenu What am I doing wrong? I get these errors even if I create a default app with no code?

I have received a few crash reports for my app "Find Any File" with an assertion failure as follows: assertion failure: "displayTiming != ((void *)0)" -&gt; %lld Googling this turns up nothing, though. I wonder if someone has some insight into why this might happen, and how to prevent it. One reporting user suggests that it happens when my app shows a very long list of items in an NSTableView (&gt;10000 elements). I have 4 reports from 3 users, and the main thread is doing something related to the table view each time, though not the same (the few other threads are all idle): Crash 1, in macOS 14.0 (23A344: Thread 0:: Dispatch queue: com.apple.main-thread 0 libobjc.A.dylib 0x182c69400 objc_msgSend + 0 1 AppKit 0x186f15400 -[CALayer(NSViewVisibleRect) NS_viewVisibleRectDidChange] + 40 2 AppKit 0x186900e10 NSViewHierarchyInvalidateVisibleRect + 276 3 AppKit 0x186900db0 NSViewHierarchyInvalidateVisibleRect + 180 4 AppKit 0x186900db0 NSViewHierarchyInvalidateVisibleRect + 180 5 AppKit 0x186900db0 NSViewHierarchyInvalidateVisibleRect + 180 6 AppKit 0x186900db0 NSViewHierarchyInvalidateVisibleRect + 180 7 AppKit 0x186900db0 NSViewHierarchyInvalidateVisibleRect + 180 8 AppKit 0x1869990e0 -[NSView translateOriginToPoint:] + 164 9 AppKit 0x186984108 -[NSClipView _immediateScrollToPoint:] + 420 10 AppKit 0x186983eb8 -[NSClipView scrollToPoint:] + 184 11 AppKit 0x186998d80 -[NSScrollView scrollClipView:toPoint:] + 84 12 AppKit 0x1869448dc -[NSClipView _scrollTo:animateScroll:flashScrollerKnobs:] + 480 13 AppKit 0x186b65b24 __62-[NSScrollingBehaviorConcurrentVBL _stopGestureScrollTracking]_block_invoke + 192 14 AppKit 0x186e6a6e8 ___NSMainRunLoopPerformBlockInModes_block_invoke + 44 15 CoreFoundation 0x18310b8c0 __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 28 Crash 2, in macOS 14.1.1 (23B81): Thread 0:: Dispatch queue: com.apple.main-thread 0 CoreFoundation 0x18ba401f4 DYLD-STUB$$_Block_object_assign + 0 1 libsystem_blocks.dylib 0x18b506118 _call_copy_helpers_excp + 80 2 libsystem_blocks.dylib 0x18b505c68 _Block_copy + 376 3 libdispatch.dylib 0x18b641c7c _dispatch_Block_copy + 32 4 libdispatch.dylib 0x18b658df0 _dispatch_source_set_handler + 92 5 CoreFoundation 0x18b99e1e4 __CFRunLoopCopyMode + 540 6 CoreFoundation 0x18b8b7458 CFRunLoopAddObserver + 220 7 AppKit 0x18f0a687c _PerfAddRunLoopObserver + 192 8 AppKit 0x18f87cd60 -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 368 9 AppKit 0x18f323318 -[_NSScrollingConcurrentEventMonitor startMonitoring] + 380 10 AppKit 0x18f321df8 -[NSScrollingBehaviorConcurrentVBL _scrollView:trackGestureScrollWithEvent:] + 884 11 AppKit 0x18f2e67f8 -[NSScrollingBehaviorConcurrentVBL scrollView:scrollWheelWithEvent:] + 512 12 AppKit 0x18f241770 forwardMethod + 252 13 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 14 AppKit 0x18f241770 forwardMethod + 252 15 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 16 AppKit 0x18f241770 forwardMethod + 252 17 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 18 AppKit 0x18f241770 forwardMethod + 252 19 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 20 AppKit 0x18fc45880 -[NSCollectionView scrollWheel:] + 180 21 AppKit 0x18f241770 forwardMethod + 252 22 AppKit 0x18f241770 forwardMethod + 252 23 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 24 AppKit 0x18f241770 forwardMethod + 252 25 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 26 AppKit 0x18f241770 forwardMethod + 252 27 AppKit 0x18f2e62a0 -[NSView scrollWheel:] + 408 28 AppKit 0x18f1d27b0 -[NSWindow(NSEventRouting) _reallySendEvent:isDelayedEvent:] + 652 As you can see, there's no code of mine involved at the time of crash. The other (and older) reports are similar, in macOS 13.6.1 and macOS 13.1. All four happened on ARM architecture (which may not be significant due to small number of samples). Memory use of app was not critical (in one case it was about 9 GB total, in others below 4 GB). The "Binary Images" section only lists Apple libs, apart from my app's. So, there seems to be no 3rd party ext involved. I've attached a full report as well. Full report of Crash 1

When you have multiple Apps on the Mac which all provide Quicklook extensions for the same file type, then I would assume that if I activate one of these Quicklook extensions in the system settings, this one would be used. But this doesn't seem to be the case. It looks like the macOS just looks the very first extension it can find for a certain file type, and if this Quicklook extension is switched off, the file can not be previewed anymore. The macOS just doesn't bother to look for the other existing quicklook extension for this file, even if this other is enabled. The only option right now to get this other extension to be used by the system would be to completely delete the first App, so its extension is deleted as well. Is this really the way how it is supposed to work? How can this be fixed? Can I tell my users something else than "just delete the other App"?

I'd like to create a Quick Look extension for a file type for which a location or region on a Map should be shown as preview. However the MapView would only show a grid without any map. From within the MapKit delegate I can see from the "Error" parameter (a server with this domain can not be found) that this seems to be a network issue. The Quick Look extension seems to have no access to the internet and therefore the MapView can not load any map data. I've then also done some other tests via URLSession, which also only fails with connection errors. I haven't seen any limitations or restrictions mentioned in the API documentation. Is this the expected behavior? Is this a bug? Or am I missing something?

Hello Using a MacBook Pro Intel with macOS 12.7.6 Monterey, I test in Objective-C an event for the option key but it is not working - (void)keyDown:(NSEvent *)event { printf("%s %p\n", __FUNCTION__, self); BOOL altFlag = [event modifierFlags] & NSEventModifierFlagOption; if (altFlag) { // UpdateClass printf("option pressed\n"); } else { printf("option not pressed\n"); } } The same in Swift works fine override func keyDown(with event: NSEvent) { if event.modifierFlags.contains(.option) { print("option pressed") } else { print("option NOT pressed") } } The Obj-C code works fine on a MacBook Air Tahoe 26.3 Any idea why it does not work on the macOS 12.7.6 Intel? Many Thanks Jean

We are currently testing our application under macOS 26 in Liquid Glass mode and noticed an issue with NSSegmentedCell. Our app makes extensive use of NSCell-based drawing. Since macOS 26, when running in Liquid Glass mode, NSSegmentedCell does not render at the expected location. The control itself appears visually correct, but it is clearly drawn offset from the rect it is supposed to occupy. In compatibility mode, everything renders exactly as expected (same code, same layout). To illustrate the issue, here are two screenshots of the same view: Liquid Glass mode 👉 (screenshot 1 – segmented control visibly shifted) Compatibility mode 👉 (screenshot 2 – correct rendering) The regression is obvious when switching between the two modes. This behavior has been present since the first macOS 26 release and is still reproducible with Xcode 26.2 (17C52). I have already filed a report via Feedback Assistant (FB reference available if useful), but I’m posting here to see whether others are experiencing the same issue or have found a workaround. Thanks.

In this Mac App, I have an IBOutlet (which is defined as instance of a subclass of NSView). When I connect the IBOutlet to the code, referencing as file's owner, it works OK. But if I reference to the class, it crashes, when I access a specific IBOutlet (but other IBOutlets are accessed just before it without crashing).. The IBOutlet turnPageControl is defined as instance of subclass of NSView. Note: I have implemented several init methods: override init(window: NSWindow!) { } required init?(coder: (NSCoder?)) { } // Yes, (NSCoder?) convenience init(parameters) { // loading from nib } override func windowDidLoad() { super.windowDidLoad() // Access turnpageControl I get those calls before crash: init(window:) init(parameters:) init(window:) windowDidLoad() -> crash inside on accessing the IBOutlet for turnPageControl.isHidden = true Is there any reason to this ?

I reported Korean IME bug to QT Bug report. Please refer to below link. https://bugreports.qt.io/browse/QTBUG-136128?jql=text%20~%20korean%20ORDER%20BY%20created%20DESC But, QT reponsed me like follwing. Thank you for reporting. However, this issue seems like a known issue with apple's Korean IME. There are many threads in Korean community about the same problem with Non-Qt apps. If this issue is a really Qt issue, feel free to open it again. Is there any workaround to fix this IME bug ? Thanks, Ted

My application provides a unique feature for MacOS 26+ users, while keeping legacy for other versions (12.4+). So I aim to provide two help books localized package, depending on MacOS' version of the running computer. I designed two help bundles, with their own Info.plist files (identifiers, default filename…) and I've made multiple checks to verify that all their settings are correct and different when needed. As an app's info.plist can deal only with one Help Book, my application delegate registers both in applicationDidFinishLaunching: using: [[NSHelpManager sharedHelpManager] registerBooksInBundle:[NSBundle mainBundle]]; In Interface Builder, the help menu item is connected to the application delegate's "showHelp:" method to set the correct help package. The code in this method is: if (@available(macOS 26.0,*)){ helpbook = @"fr.myapp.updated.help"; } else { helpbook = @"fr.myapp.legacy.help"; } [[NSHelpManager sharedHelpManager] openHelpAnchor:@"index" inBook:helpbook]; The problem is that despite the MacOS version of the user's Mac, (either 15.1 or 26.2) , the «legacy» helpbook is always used. All default index.html (for each lproj) have a tag immediately after the I spent dozen of hours to understand the problem, forum parsing, including hours long dialogs with ChatGPT and Claude AIs (not mentioning MacOS' help system cache problems I could solve) I noticed also, to be complete, that when parsing the application package, opening the legacy .help with "Tips.app" always works, but with the "updated" one the help system opens with an "unavailable content" message. Both help bundles are fully included in the built application. Tested whether the app is installed in the debug directory, moved to in the Applications one, reboot, emptying/deleting cache files. So Houston, I have a problem… Any idea?

I'm building a macOS app that uses WKWebView for text editing (not NSTextView). I need to provide grammar checking by calling NSSpellChecker programmatically and sending results back to the web editor. The problem: TextEdit (which uses NSTextView) catches grammar errors like "Can I has pie?" and "These are have" — but when I call NSSpellChecker's APIs directly, those same errors are never flagged. I've tried both APIs: 1. The unified check() API: let results = checker.check( text, range: range, types: NSTextCheckingAllTypes, options: [:], inSpellDocumentWithTag: tag, orthography: &orthography, wordCount: &wordCount) This returns only .orthography results (language detection). No .spelling, no .grammar — just orthography. 2. The dedicated checkGrammar(of:startingAt:...) API: let sentenceRange = checker.checkGrammar( of: text, startingAt: offset, language: nil, wrap: false, inSpellDocumentWithTag: tag, details: &details) This catches sentence fragments ("The.", "No.") and some agreement errors ("The is anyone.") but misses "Can I has pie?", "These are have", "This will be happened", and other subject-verb agreement errors that TextEdit highlights. What I've confirmed: "Check Grammar With Spelling" is enabled in System Settings TextEdit reliably catches all these errors with green underlines Both APIs are called with a valid spellDocumentTag from uniqueSpellDocumentTag() The text is passed as plain strings (no attributed string context) My question: How does NSTextView's grammar checking work internally? It must be using something beyond these two public APIs. Possibilities I'm considering: Does NSTextView use the NSTextCheckingClient protocol / requestChecking(of:range:types:options:) for asynchronous checking that produces different results? Does NSTextView provide additional context (attributed string, layout info) that improves grammar detection? Is there a private/undocumented API or framework that NSTextView uses for deeper grammar analysis? Any insight from anyone who has implemented programmatic grammar checking on macOS would be appreciated. NOTE: This post was composed with the help of Claude Code, which I am using to help write a word-processing application, but I am frustrated because Claude Code wants to give up and switch to a 3rd party grammar checker, like LanguageTool, and it seems to me that it should be possible to use native Apple tools to achieve this goal without requiring the user to send their data elsewhere for checking. I've spent a lot of time searching the web for answers and have found surprisingly little on this. Any pointers people might have would be very much appreciated! Thanks.

When disabling the opacity slider of color panels, my app crashes with unsatisfiable layout constraints. Feel free reproduce with a minimal test project: A macOS app based on the Xcode 26.0 template with only one line added to the ViewController's viewDidLoad() function: NSColorPanel.shared.showsAlpha = false The issue doesn't occur if this property is set to "true" or not set at all. I just filed a corresponding bug report (FB20269686), although I don't expect any feedback from Apple ... as numerous issues I reported were never updated or commented at all (after migrating from RADARs).

Context: Xcode 16.4, Appkit In a windowController, I need to create and send a mouseDown event (newMouseDownEvent). I create the event with: let newMouseDownEvent = NSEvent.mouseEvent( with: .leftMouseDown, location: clickPoint, // all other fields I also need to make window key and front, otherwise the event is not handled.   func simulateMouseDown() { self.window?.makeFirstResponder(self.window) self.calepinFullView.perform(#selector(NSResponder.self.mouseDown(with:)), with: newMouseDownEvent!) }   As I have to delay the call( 0.5 s), I use asyncAfter: DispatchQueue.main.asyncAfter(deadline: .now() + 0.5, qos: .userInteractive) { self.simulateMouseDown() }   It works as intended, but that generates the following (purple) warning at runtime: [Internal] Thread running at User-interactive quality-of-service class waiting on a lower QoS thread running at Default quality-of-service class. Investigate ways to avoid priority inversions I have tried several solutions, change qos in await: DispatchQueue.main.asyncAfter(deadline: .now() + 0.5, qos: ..default) call from a DispatchQueue let interactiveQueue = DispatchQueue.global(qos: .userInteractive) interactiveQueue.async { self.window?.makeFirstResponder(self.window) self.calepinFullView.perform(#selector(NSResponder.self.mouseDown(with:)), with: newMouseDownEvent!) } But that's worse, it crashes with the following error: FAULT: NSInternalInconsistencyException: -[HIRunLoopSemaphore wait:] has been invoked on a secondary thread; the problem is likely in a much shallower frame in the backtrace; { NSAssertFile = "HIRunLoop.mm"; NSAssertLine = 709; }   How to eliminate the priority inversion risk (not just silencing the warning) ?

When building in Xcode on MacOS Tahoe, it seems it is no longer possible to dynamically specify a "small" size toolbar for NSToolbar/NSToolbarItem. It works in MacOS code compiled and linked on earlier systems. I don't want to use "SFSymbol", or "templates". I have over 60 custom-made .png toolbars, in individual Image Set files, at the previous requisite sizes of 24x24 / 48x48, and 32x32 / 64x64. Sure -- I can configure an NSToolbar with whatever size .png assets I want. I just can't dynamically switch between the two groups of sizes. According to the Apple Coding Assistant, the only solution is to change the image names of each of the NSToolbarItems at runtime. OK -- but even when attempting that, the NSToolbarItems refuse to take on their smaller size... ...unless: they are attached to a custom view NSToolbarItem with an NSButton of style "Bevel". I have about 10 of those, and YES -- I CAN change those to a "small" size. Is this REALLY what I'm forced to do?! The Apple Coding Assistant just runs me around in circles, making coding suggestions that include properties that don't exists. I've gone around and around on these issues for over a week -- it can't be this hard, right? Is there no way to make multiple NSToolbar objects, one for "large" and one for "small"?

NSWindow objects with custom styleMask configurations seem to behave erratically in macOS Tahoe 26.3 RC. For example an NSWindow is not resizable after issuing .styleMask.remove(.titled) or some NSWindow-s become totally unresponsive (the NSWindow becomes transparent to mouse events) with custom styleMask-s. This is a radical change compared to how all previous macOS versions or the 26.3 beta3 worked and seriously affects apps that might use custom NSWindows - this includes some system utilities, OSD/HUD apps etc, actually breaking some apps. Such fundamental compatibility altering changes should not be introduced in an RC stage (if this is intentional and not a bug) imho.

Since we started building our application on Tahoe, all NSPopupButtons in the UI stop truncating when the window they're in is moved to a different screen. Even though their frame is correct, if the selected item string is longer than what can fit, they just draw outside of their bounds, overlapping other neighbouring controls. This is reproducible only in our app target even though they are not subclassed or overridden in any way. The same window copied to a test app doesn't have the issue. Initially good After dragging to another screen Frame is correct in the View Hierarchy debugger, but the contents are incorrect. Very simple constraint setup, with content compression resistance set lower to allow resizing below the intrinsic content size. This is what happens on this simple test window. The rest of the popups in more complex windows are all bad right away, without requiring you to move them to a different screen. When built on Sequoia, all is well regardless of which OS the app is run on. Looking for ideas on how to troubleshoot this and figure out what's triggering it.

I have a mac app using AppKit. I have a view that extends under the toolbar. It is very slightly blurred but still disturbs the readability of the toolbar items. In another window, I have a view that sits inside a NSScrollView and there the content is much more blurred and a bit dimmed under the toolbar. Is there a way to make the not scrolled view behave like the one in the NSScrollView?

In an NSTableView (Appkit), I need to colour a cell background when it is selected. That works OK, except that the colour does not span the full cell width, nor even the text itself: The tableView structure is very basic: I see there is a TextCell at the end that cannot be deleted. What is this ? And the colouring as well: func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? { let p = someDataSource[row] if let cellView = tableView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "Cell"), owner: self) { (cellView as! NSTableCellView).textField?.stringValue = p if selected[row] { (cellView as! NSTableCellView).backgroundColor = theLightBlueColor } else { (cellView as! NSTableCellView).backgroundColor = .clear } return cellView } } I've tried to change size constraints in many ways, to no avail. For instance, I changed Layout to Autoresising : I tried to change TableCellView size to 170 vs 144: Or increase tableColum Width. I have looked at what other object in the NSTableView hierarchy should be coloured without success. Nothing works. What am I missing ?