Kuba Suder's blog on Mac & iOS development


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iPad and iPhone apps on Apple Silicon Macs

Categories: Mac, UIKit, WWDC 20 0 comments Watch the video

iPhone and iPad apps can now run unmodified on macOS on ARM, the same exact binary as on iOS

Uses Catalyst APIs, so apps get a lot of behavior for free

Making a separate Catalyst build manually is still recommended for optimal result (and supports Intel Macs)

To run on the Mac, an iOS app must not:

  • depend on missing symbols, frameworks or other functionality (Xcode should help you at least in some cases)
  • depend on hardware which Macs don’t have

Compatible apps are automatically made available for Macs unless you opt out

Possible compatibility issues:


  • Macs use mouse & keyboard and not touch screens, so if an app uses touch in non-standard ways or relies on multi-touch, this might not work
  • apps that depend on sensors like accelerometer, gyroscope, compass, depth camera, precise GPS will not work
  • iOS apps expect one front and one back camera, Macs may have one, none or multiple (use AVCaptureDeviceDiscoverySession)


  • alerts and panels like open/save will look differently than on iOS, so don't assume their dimensions and position
  • if an iPad app supports multitasking, it will be fully resizable to any dimensions, including some layouts and sizes you might not expect
  • iPhone-only apps and iPad apps that don’t support multitasking will run in a fixed size window matching iOS device size
  • window resizing is live on macOS – make sure it’s optimized

System software:

  • on the Mac, user can move the app bundle to different locations, application container is also in a different location
  • APIs returning device type or model will include Mac model types
  • screen size will not be one of the standard iOS device screen sizes that you may expect

You can debug, profile and test iOS on an ARM Mac as you would expect

Distribution for Mac devices works the same as for iOS devices

Apps can reuse existing subscriptions and in-app purchases

App thinning automatically selects most appropriate resources for the given Mac

→ when making a thinned build, you can select the option to optimize for any Mac

TestFlight is (still) not available on the Mac

Meet Safari Web Extensions

Categories: Mac, Safari, WWDC 20 0 comments Watch the video

Existing extension ecosystem:

  • content blockers (iOS & macOS)
  • share extensions – can run JS on the currently opened web page and return data to the extension
  • Safari app extensions on macOS

If you’re a web developer and don’t want to learn Swift to build an extension, or you have an existing extension for Chrome/Firefox/etc., you can now use the new Safari Web Extensions API

Extensions built primarily using HTML, JS and CSS, like legacy Safari extensions

API compatible with other browsers

Improved user privacy controls

Can be sold through the App Store

Some APIs are missing, so provide feedback if you want something added

Like other extensions, Web Extensions must be packaged inside a native Mac app

Xcode 12 is required to build and run

A command-line tool is provided which wraps an exising web extension into a new app:

xcrun safari-web-extension-converter […] /path
  • lets you know if any features are not available
  • the largest icon in the manifest is used as the app icon (it’s recommended to include 512×512 and 1024×1024 icons)

To create a new extension from scratch, create a “Safari Extension App” or add a “Safari Extension” target, and choose Type = Safari Web Extension.

Extension privacy

If your extension needs access to specific sites, the user will be asked for permission to run it on that site for one day or always

Optional permissions: you can include the URL pattern under optional_permissions key and then ask for access using browser.permissions.request(…) at the moment when you require access

The Safari preferences window page of your extension shows information about what kind of access was granted to the extension

It’s best to use the activeTab permission, which grants access to the currently open page when the user interacts with your extension in some way

The hostname of the extension changes every time Safari is launched in order to prevent fingerprinting

→ use browser.runtime.getURL(“/path/to/resource”) to create URLs to assets


Access the background page through the Develop menu

Content scripts are visible in the Sources tab for the page

  • to run JS in the console in the context of a content script, choose the script from the pulldown menu in the corner

Don’t rely on code being executed when the page loads, since the extension may not have permission to run yet at this point

Communicating between components

Content script  ⭢  background page:



Background page  ⭢  extension:


Handled by the SafariWebExtensionHandler.beginRequest(with context:) delegate method

→ requires nativeMessaging permission

Extension  ⭢  background page:

Use completion handler from NSExtensionContext object in SafariWebExtensionHandler.beginRequest() to send back a response

App  ⭢  background page:

SFSafariApplication.dispatchMessage() (check that extension is turned on first)

App  ⭤  extension:

Shared NSUserDefaults from an app group, or NSXPCConnection

Adopt the new look of macOS

Categories: AppKit, Mac, WWDC 20 0 comments Watch the video

macOS has an all new design

A new toolbar with inline title, big bold controls and integration with the window’s split view

Full height sidebars with colorful icons and updated symbol iconography

New appearance for lists/tables using a new inset selection style

Most of these changes happen automatically to your app (if you’re using classes like NSToolbar and NSSplitViewController)


Sidebar: use NSSplitViewController, items configured using NSSplitViewItem.Behavior.sidebar

Use full size content window mask – NSWindow.StyleMask.fullSizeContentView, so that content is laid out in the space normally taken by the title bar

NSView properties to find the safe areas of the view: safeAreaInsets, safeAreaLayoutGuide, safeAreaRect

Also available on the storyboard (“Safe Area Layout Guide”)

New view item in the library: Window Controller with Sidebar (NSWindowController + NSSplitController)

Opting out of the full height sidebar: NSSplitViewItem.allowsFullHeightLayout

  • when sidebar is typically collapsed, or when you need more space for the toolbar

By default all sidebar icons are colored with the accent color

Use NSOutlineViewDelegate method outlineView(_: tintConfigurationForItem:) to customize

Return an instance of NSTintConfiguration:

  • .default – always uses (system) accent color
  • .monochrome – gray monochrome
  • init(preferredColor:) – use this color when default (“rainbow”) accent color is used, but follow the accent color if it’s customized
  • init(fixedColor:) – a fixed color that is always used (e.g. the yellow star in Mail’s VIP folder)

Use sidebar colors to distinguish different sections of the sidebar, or highlight a specific item like the VIP star

Or use monochrome to de-emphasize groups


There’s no longer any special material behind the toolbar items, it’s a uniform part of the content of the window

Works automatically

New toolbar styles, controlled through NSWindow.toolbarStyle

Types of NSWindowToolbarStyle:


  • the new standard – like in the new versions of system apps
  • larger controls, bold icons
  • inline title located at the leading edge of the title bar next to the sidebar
  • good choice for most windows


  • more compressed style
  • regular sized controls, smaller toolbar height
  • this is what was previously used if the window was configured to hide the title bar
  • now supports an optional inline title
  • use when user’s focus should be on the content of the window and there aren’t many elements in the toolbar


  • specifically designed for preference windows
  • automatic when you’re using NSTabViewController with the .toolbar tab style


  • what used to be the standard layout of the toolbar
  • title is centered on top of the toolbar and can expand across the window
  • large button icons with labels below
  • use when the window title is long, or the toolbar is heavily populated with items, or when you want to keep existing toolbar layout


  • default value
  • determines the toolbar style based on your window structure
  • existing apps linked on older SDKs keep their old layout

Toolbar buttons no longer have a border, a shape only appears when hovering

Controls with text fields show a slight border so that you know where you can click to focus

NSToolbarItem minSize & maxSize properties are deprecated – macOS can automatically give your controls a proper size

You can still use constraints if necessary

New NSWindow.subtitle property – shows a smaller subtitle under the window title, e.g. the message count in Mail

In .expanded style it appears next to the title

Controls like back/forward buttons should be put on the leading edge of the title bar, before the title

Set NSToolbarItem.isNavigational to position them there

Users can add and remove them from the toolbar, but can only put them in the leading edge area


  • new toolbar control for search text fields
  • appears as a text field if there’s enough space, otherwise collapsed into an icon
  • searchField property
  • works on older versions of macOS


  • a separator that extends the separator line of the window content’s split view upwards through the toolbar
  • when creating, you pass it the split view to track and the index of its divider

To position items in the title bar area of the sidebar, include an item NSToolbarItem.Identifier.sidebarSeparator and add those items *before* the sidebar separator item

The toolbar has no border below, but a slight shadow appears below it to separate it from the content when the content is scrolled

  • this happens if the scroll view fills the frame and you’re using .fullSizeContentView
  • otherwise, there will be a separator regardless of the scrolling position
  • customize toolbar separator in the window using NSWindow.titlebarSeparatorStyle, or in split view per section using NSSplitViewItem.titlebarSeparatorStyle


New modern design of controls like popup buttons, sliders, segmented controls

New multicolor system accent color – uses each app’s preferred accent color

Define the app’s global accent color in the asset catalog (can be different for light/dark mode) + set name in build options

People can still chose one of the previously available accent colors, and then that color overrides your setting so they can use that color everywhere

It’s preferred to use named colors like controlAccentColor, selectedContentBackgroundColor, keyboardFocusIndicatorColor instead of explicitly using your own color for controls

New .large control style, e.g. when you need one large action button

Works for: a few kinds of buttons, text fields, search fields, segmented controls

Also used in the unified toolbar style, and in system alerts

New inset style for table selection

Adds extra padding, taller default row heights

  • .automatic (default)
  • .fullWidth – edge to edge selection background, like previously
  • .inset
  • .sourceList – new appearance of sidebar source list

Automatic style uses .inset by default (on apps built on the latest SDK), .fullWidth in bordered scroll views, .sourceList in source lists

→ you can check the effectiveStyle property to see what style is actually used

The old SelectionHighlightStyle.sourceList setting is deprecated


System text styles are now available (Large Title, Headline, Body etc.) – but without Dynamic Type, so they have one constant size

NSFont.preferredFont(forTextStyle: options:)

NSFontDescriptor.preferredFontDescriptor(forTextStyle: options:)

Symbol images

SF Symbols is now available on the Mac

They can scale to different font sizes and weights

Toolbar and sidebar items automatically configure symbol images to match the size & style of the container

NSImage.init?(systemSymbolName: accessibilityDescription:)

It’s best to use them inside NSImageView (see symbolFont, symbolScale properties)

To customize symbol configuration, use NSImage.withSymbolConfiguration(…)

Most of existing named system images now return some kind of symbol image from SF Symbols

What’s New in AppKit for macOS

Categories: AppKit, Mac, WWDC 19 0 comments Watch the video

New system colors: NSColor.systemTeal and systemIndigo

NSColor uses tagged pointers

NSColorSampler – a magnifier tool for picking a color from somewhere on the screen

Recording the screen will now ask the user for permission

NSColor(name: “…”) { appearance … }

NSScreen.localizedName now returns e.g. “Thunderbolt Display”


CAMetal.wantsExtendedDynamicRangeContent = enables dynamic range in this layer

NSScreen.maximumExtendedDynamicRangeColorComponentValue = tells you the maximum white value (e.g. 1.3)

NSScreen.maximumPotentialExtendedDynamicRangeColorComponentValue – tells you this even when it’s not on


CAMetalLayer.preferredDevice, MTKView.preferredDevice

NSTextView.usesAdaptiveColorMappingForDarkAppearance – automatically updates colors for light/dark appearance

NSTextCheckingController + NSTextCheckingClient – for spell checking, data detection, autocorrection


NSAttributedString text scaling macOS  ⭤  iOS


NSToolbarItem.isBordered, title

NSToolbarItemGroup: segmented controls and pulldown/popup menus, collapsed representation




NSSliderTouchBarItem.minimumSliderWidth, maximumSliderWidth

NSSwitch – a new NSControl like UISwitch on iOS (avoid using for small things and in large numbers, just one for some general mode switch, like Time Machine on/off)

NSCollectionView – compositional layout, diffable data source

using custom VC initializers for injecting dependencies:

@IBSegueAction func showFoo(_ coder: NSCoder) -> NSViewController { }

NSView.isHorizontalContentSizeConstraintActive, isVertical

Open and save panels are now always out-of-process, even for non-sandboxed apps

NSWorkspace: asynchronous methods for opening URLs and applications


Using iPad with Sidecar as a tablet: tablet events come as mouse events with NSEvent.SubType.tabletPoint and pressure

NSEventType .changeMode  ⭢  on double-tap on the pencil





NSListFormatter – formats list of things, adding commas properly

Non-UI file provider action extension

Replacing kernel extensions with Network Extensions, DriverKit, Endpoint Security

Advances in macOS Security

Categories: Mac, WWDC 19 0 comments Watch the video

Defense in depth: there isn’t any single layer that can always perfectly protect you, so there are multiple layers of security, so if any single layer fails that doesn’t defeat the whole security of the system

Layers can delay the advance of the attacker, reduce the attack surface, create “choke points” that are easier to defend

Gatekeeper: designed to protect users from running malicious software, while allowing them to use the software they choose

What does Gatekeeper check:

  • does the app contain any known malicious content?
  • has the software been tampered with since it was signed?
  • does it meet the security policy configured on the computer?
  • first launch prompt  ⭢  does the user actually want to run this?

On Mojave, Gatekeeper runs the check on the 1st launch of quarantined software launched via Launch Services

Quarantine – a technology on macOS for marking files that arrived from some external source (website, airdrop, iMessage, email)

  • includes metadata about where the file came from
  • opt-in – the app has to opt-in to this, so e.g. when apps download their own updates they are usually not quarantined, except for sandboxed apps

Launch Services – a framework for finding and launching apps on macOS, used when launching apps from Finder, NSWorkspace, document handlers etc.

What does not use Launch Services: NSTask, NSBundle/dlopen, exec/posix_spawn

In macOS Catalina:

  • all new software must be notarized to pass Gatekeeper
  • all software is checked when first launched, even when launching through those non-LaunchServices methods
  • all software (even not quarantined) is checked for malicious content on every launch

"You can always choose to run any software on your system" – there will always be a way to run a specific piece of software that you want to run

“We want to make macOS just as secure as iOS, while still maintaining the flexibility that you’ve come to expect from your Mac”

Platform security is increasingly reliant on validity of code signatures; that means if code has no signature, it’s impossible to detect tampering

In a future version of macOS, unsigned code will not load by default, so:

  • sign and notarize all software
  • don’t modify signed applications and bundles
  • handle failures when loading libraries

Privacy changes:

Requires user confirmation for:

  • screen recording
  • keyboard input monitoring

Requires confirmation for access to:

  • Desktop, Documents, Downloads
  • iCloud Drive and third-party cloud storage
  • Removable and network volumes


  • *not* required for creating new files, only for reading existing files
  • tries to understand intent, e.g. doesn’t ask if user double-clicked a file in Finder, or drag&dropped it, or used an open/save panel
  • declare handled CFBundleDocumentTypes with NSIsRelatedItemType to e.g. automatically have access to a subtitles file when opening a movie file

Purpose strings are accepted, but not required (NSDesktopFolderUsageDescription etc.)

Open and save panels always run out of process

Be careful with:




Checking for readability without triggering a consent dialog: isReadableFile, isWritableFile, access()

Apps and other binaries that have previously been denied access to some kind of directory now appear automatically in the "Security & Privacy" access list, unchecked

Full disk access now required for access to Trash (except files that your app has moved there)