Mocking window.location in Jest

· Concepts · Patrick Smith

It’s sometimes necessary to mock window.location in Jest tests. This could because you want to know when window.location.reload() is called, or one of its other methods (.assign(), .replace()).

Here’s some code to achieve this:

const savedLocation = window.location;

beforeEach(() => {
  delete window.location;
  window.location = Object.assign(new URL("https://example.org"), {
    ancestorOrigins: "",
    assign: jest.fn(),
    reload: jest.fn(),
    replace: jest.fn()
  });
});
afterEach(() => {
  window.location = savedLocation;
});

You could then detect whether your implementation called .reload():

it("reloads the page", () => {
  expect(window.location.reload).toHaveBeenCalled();
});

If you wanted to reuse this in multiple tests, you could wrap this in a reusable function:

function mockWindowLocation() {
  const savedLocation = window.location;

  beforeEach(() => {
    delete window.location;
    window.location = Object.assign(new URL("https://example.org"), {
      ancestorOrigins: "",
      assign: jest.fn(),
      reload: jest.fn(),
      replace: jest.fn()
    });
  });
  afterEach(() => {
    window.location = savedLocation;
  });
}

The Apple Experience Augmented — Part 2: Developer Experience

· Concepts, Product, UX · Patrick Smith

Apple has been iterating for years on a curious set of APIs called ARKit that has been largely ignored by the iPhone & iPad developer community, which hints that more compelling hardware is coming to take full advantage. CEO Tim Cook has openly said AR is the ‘next big thing’.

Rumors suggest Apple is developing an augmented reality (AR) glasses product. This product would likely act as an iPhone periphery, at least initially, similar to how Apple Watch once relied on a host iPhone to provide the main computational grunt. Well informed supply chain analyst Ming-Chi Kuo has said the AR glasses “will primarily take a display role offloading computing, networking, and positioning to the iPhone.”

Apple has recently introduced M1 Macs powered by Apple Silicon. These Macs are notable because they bring a marked improvement in battery life and performance. But they also bring Apple’s developer devices finally in line with the more capable hardware of their consumer devices.

Apple’s head of software engineering Craig Federigi talked with Ars Technica about the advantages of M1’s unified memory architecture:

Where old-school GPUs would basically operate on the entire frame at once, we operate on tiles that we can move into extremely fast on-chip memory, and then perform a huge sequence of operations with all the different execution units on that tile. It’s incredibly bandwidth-efficient in a way that these discrete GPUs are not.

Ars Technica interview with Apple executives

Tiled rendering will be needed by the upcoming AR glasses product, with the increased throughput allowing both high resolutions and high frame rates. High frame rates are required as “frame rates below 90 frames per second (FPS) is likely to induce disorientation, nausea, and other negative user effects”. The iPad Pro can already achieve 120 frames per second, so it’s likely the AR glasses’ display would reach similar rates.

So how would you develop apps for such a device? Let’s look at how developing software for the iPhone works today.

Developers buy Macs and install Xcode which allows them to write, compile, and deploy iPhone (and iPad, Mac, Watch & TV) apps. To actually experience the user experience of their apps, developers either push the app to their own iPhone and launch it like any other app, or they run it directly on their Mac within the Simulator. They choose which device they want to simulate and then see an interactive representation of the device’s screen running their app within a window on their Mac.

Screenshot showing the run destination menu in the toolbar where you choose a real device, choose a simulated device, or create a custom simulator.
Could you one day choose AR Glasses from the list here?

Currently this has worked by compiling the iPhone or iPad software for Intel chips, allowing the app to be run ‘natively’ on the Mac. Macs are powerful enough to run several of these simulators at once, however checking graphic intensive experiences such as 3D or animation sometimes means avoiding the simulator and trying the app directly on the target device. On the whole the simulator does a capable enough job to preview the experience of an app.

(An iPad version of Xcode has been speculated for years, been even with their improved keyboards and fancy trackpads, nothing has been released. The Mac maintains its role as the developer device for Apple’s platforms.)

How will this work for the AR glasses? Will Xcode provide an AR glasses Simulator for Mac? Would that appear as a window on screen with a preview for each eye? Or would you need to push the app to an actual device to preview?

If a simulator was provided, the pre-Apple-Silicon technology of an Intel chip and AMD GPU would not be able to reproduce the capabilities of a unified memory architecture, tiled rendering, and the neural engine. It would either run poorly, at low frame rates, or some capabilities might not even be possible at all. An Intel Mac can simulate software but it cannot simulate hardware. A Mac with related Apple Silicon hardware would allow a much better simulation experience.

Instead of seeing a preview of the AR display on your Mac’s screen, consider if the product could pair directly to your Mac. The developer could see a live preview of their work. The Mac could act as a host device instead of the iPhone, providing the computation, powerful graphics, machine learning, and networking needs of the AR glasses.

With the same set of frameworks brought over allowing iPhone & iPad apps to be installed and run on the Mac, both software and hardware will be ready to run AR-capable apps designed for iPhone. The Mac is now a superset of iPhone, and so what the iPhone can do, the Mac can also do. App makers now have a unified developer architecture.

Perhaps AR-capable apps from the iPhone App Store could even be installed by normal users directly on their Mac. With augmented reality perhaps the glasses will augment the device you currently use, whether that’s the iPhone in your pocket or the Mac on your desk. And allow switching back-and-forth as easily as a pair of AirPods (which would likely be used together with AR glasses).

There’s one last picture I want to leave you with. Swift Playgrounds works by showing a live preview of interactive UI alongside editable code. Change the code and your app immediate updates. The Simulator has been integrated into the app developer experience.

Now imagine Swift Playgrounds for AR — as I edit my code do my connected AR glasses instantly update?

The Apple Experience Augmented — Part 1: User Experience

· Concepts, Product, UX · Patrick Smith

I want to cover what the user experience of an AR Glasses product from Apple could look like, and how it might integrate with today’s products. First, let’s survey Apple’s current devices and their technologies for input & output:

iPhone input methods

  • Multitouch: use your fingers naturally for UI interactions, typing text, drawing, scrolling
  • Voice: request commands from Siri such as change volume or app-switching, dictate instead of typing

iPad input methods

  • Multitouch: use your fingers naturally for UI interactions, typing text, scrolling, drawing
  • External Keyboard: faster and more precise typing than multitouch
  • Pencil: finer control than multitouch, especially for drawing
  • Trackpad: finer control than multitouch, especially for UI interactions
  • Voice: request commands from Siri such as changing volume or app-switching, dictating text

Mac input methods

  • Keyboard: dedicated for typing text, also running commands
  • Trackpad / Mouse: move and click pointer for UI interactions, scrolling, drawing
  • Function keys: change device preferences such as volume, screen/keyboard brightness; app-switching
  • Touchbar: change volume, screen/keyboard brightness; enhances current app with quick controls
  • Voice: request commands from Siri such as changing volume or app-switching, dictating text

Apple Watch input methods

  • Touch: use your fingers for UI interactions, awkward typing text, scrolling
  • Digital Crown: change volume, scrolling, navigate back
  • Voice: request commands from Siri such as changing volume or app-switching, dictating text

AirPods input methods

  • Voice: request commands from Siri such as changing volume, dictating text
  • Tap: once to play/pause, double to skip forward, triple to skip backward

So what would a rumoured Apple Glasses product bring?

Apple’s Design Principles

Deference to Content

The most sparse approach might be to rely on voice for all input. Siri would become a central part of the experience, and be the primary way for switching apps and changing volume and dictating text. Siri currently can be activated from multiple devices, such as personal hand-held devices such as iPhone or shared devices such as HomePod. So it makes sense that the glasses would augment this experience, providing visual feedback that accompanies the current audible feedback.

Contrast Siri’s visual behaviour between iPadOS 13 and 14:

The Siri screen showing that Siri is asked to “Set an alarm for 8 a.m.,” and in response, Siri replies “The alarm’s set for 8 AM.” A notification from the Clock app shows that an alarm is turned on for 8:00 a.m.
Siri in iPadOS 13 takes over the entire screen
Siri on the Home Screen. A notification from the Clock app shows that an alarm is turned on for 8:00 a.m. A button at the bottom right of the screen is used to continue speaking to Siri.
Siri in iPadOS 14 layers discretely over your screen with a compact design

This provides a glimpse of the philosophy of the Apple Glasses. Instead of completely taking over what the user current sees, Siri will augment what you are currently doing with a discrete compact design.

This also relates to the Defer to Content design principle that has been present since iOS 7 which was the opening statement from Apple’s current design leadership. So we can imagine a similar experience with the Glasses, but where the content is everything the user sees, whether that’s digital or physical.

Content from a traditional app could be enhanced via augmentation. A photo or video in a social media feed might take over the user’s view, similar to going into full screen. Text might automatically scroll or be spoken aloud to the user. Content might take over briefly, and then be easily dismissed to allow the user to get back to their life.

Widgets such as weather or notifications such as received messages might be brought in from the outside to the centre. I can imagine a priority system from the viewer’s central vision to the extremes of their field-of-view). Content could be pinned to the periphery and be glanced at, while periodically in the background it receives updates.

If worn together with a set of AirPods, an even more immersive experience would be provided, with the AirPod’s tap input for playing and skipping. The active noise cancellation mode would probably pair well with a similar mode for the glasses, blocking the outside world for maximum immersion. Its counterpart transparency mode would allow the user to reduce the audible and visual augmentation to a minimum.

Clarity

So with a Glasses product, what is the content? It’s the world around you. But what if the world sometimes is an iPhone or Mac you use regularly through your day? Do the Glasses visually augment that experience?

With AirPods you can hop from an iPhone to a Mac to an iPad, and automatically switch the device that is paired. Wouldn’t it make sense for the AirPods and Glasses to perform as synchronised swimmers and pair automatically together to the same device that someone decides to use?

Can the Glasses recognise your device as being yours and know it precise location in the Glasses’ field-of-view? That sounds like what the U1 chip that was brought to iPhone 11 would do, as 9to5Mac describes it “provides precise location and spatial awareness, so a U1-equipped device can detect its exact position relative to other devices in the same room.”

Perhaps instead of tapping your iPhone screen to wake it, you can simply rest your eyes on it for a moment and it will wake up. The eyes could be tracked by the Glasses and become an input device of their own. If precise enough they could move the cursor on an iPad or Mac. The cursor capabilities of iPadOS 13.4 brought a new design language with UI elements growing and moving as they were focused on, and subtly magnetised to the cursor as it floated across the screen.

The cursor becomes the object of focus.

Similar affordances could allow a Glasses user’s eyes to replace the cursor, with the realtime feedback of movement and size increase enough to let the user know exactly what is in focus. The Mac might not need touch if the eyes could offer control.

In the physical world, a similar effect to Portrait mode from iPhone could allow objects in the world to also be focused on. The targeted object would remain sharp, and everything around it would become blurred, literally putting it into focus.

AirTags could enhance physical objects by providing additional information to their neighbour. Instead of barcodes or QR codes, the product itself could advertise its attributes and make it available for purchase via Apple Pay.

Use Depth to Communicate

If the Glasses not just show you the world around you but see the world around you, then your hands gesturing signals in the air could also be a method of input. Simple gestures could play or pause, skip ahead or back, change the volume. The could also be used to scroll content or interact with UI seen through the Glasses.

These gestures would close the loop between input and output. The iPad’s multitouch display works so well because of direct manipulation: your fingers physically touch the UI your eyes see. As your fingers interact and move, the visuals move with it. The two systems of touch input and flat-panel-display output become one to the user. Hand gestures would allow direct manipulation of the content seen through the Glasses.

Speculated Apple ‘Glasses’ input methods

  • Voice via AirPods or nearby device: request commands from Siri such as changing volume, dictating text
  • Eyes: interact with devices that have a cursor, focus on elements whether digital or physical
  • Air Gestures: use your hands for UI interactions, scrolling, changing the volume, playing, pausing, skipping
  • U1: recognise nearby Apple devices and interact with them
  • Plus whatever device you are currently using (if any)

So the Glasses could offer a range of novel input methods from a user’s eyes to their hands, or it could simply rely on the ubiquitous voice-driven world that most Apple devices now provide. The U1 chip seems to hint at an interaction between Glasses and hand-held device, perhaps modest like simply recognising it, or perhaps augmenting its input and output allowing a new way to interact with iPhones, iPads, and Macs. The Glasses accompanies what the user already sees and interacts with every day, enhancing it visually but deferring to the outside world when it needs. It could offer an immersive experience for content such as video and games, or future formats that Apple and other AR-device-makers hope will become popular.

Vary variables not rules in CSS media queries

· CSS · Patrick Smith

A common pattern you’ll see when implementing responsive design with CSS is to redefine rules in media queries:

h1 {
  font-size: 2rem;
}

@media (min-width: 720px) {
  h1 {
    font-size: 2.5rem;
  }
}

@media (min-width: 1200px) {
  h1 {
    font-size: 3rem;
  }
}

Here we are writing our media queries mobile first. This means the styles for small devices (like phones) are defined first, such as our font size of 2rem for h1 elements. Then a wider device is targeted with a media query that increases the font size of h1 elements to 2.5rem when the viewport width is 720px or greater. And then another one, increasing to 3rem for viewports 1200px or wider.

So what are the issues with this approach?

First, these media queries can get bloated. You’ll find that you’ll define your base rules first using a mobile-first approach, and then repeat those rules with overrides within media queries. You could put all of these rules for the same media query together underneath, or could you have the media query override live next to its mobile-first rule and rely on some sort of CSS optimiser or compression so the repetition doesn’t contribute to an increase in file size.

Second, knowing what to override can lead to complex code. Perhaps you only need to override the rules for nav a and not for nav elements within your media queries. These specifics lead to harder to understand code.

nav {
  background-color: lightskyblue;
}
nav a {
  display: block;
  padding: 0.5rem;
}

@media (min-width: 720px) {
  /* We override the rule for `nav a` but not for `nav` */
  nav a {
    padding: 1rem;
  }
}

Perhaps you used quite complex selectors that now need to be repeated for each media query. SCSS allows the media query to be written nested inside the rule, avoiding the need to repeat it as an author. But this still adds a layer of complexity that can make understanding which rule applies in what case that much harder.

Here’s the above two examples but written to take advantage of SCSS’s nesting of media queries:

h1 {
  font-size: 2rem;

  @media (min-width: 720px) {
    font-size: 2.5rem;
  }
  @media (min-width: 1200px) {
    font-size: 3rem;
  }
}

nav {
  background-color: lightskyblue;
  
  a {
    display: block;
    padding: 0.5rem;

    @media (min-width: 720px) {
      padding: 1rem;
    }
  }
}

The result is very direct — these rules have these specific media query overrides. But there a lot of indentation going on, and things get hard to read once you add more rules and more overrides.

In summary, by redefining our rules inside media queries they have a lot of responsibility. They contain knowledge about our selectors. They override some rules but usually not all of them.

Varying CSS custom properties

So what’s the alternative? If we start using custom properties (aka CSS variables), which we can do if we no longer support Internet Explorer, then our media queries can take on a lot less responsibility and thereby be a lot simpler.

/* Define our variables, with mobile-first values */

:root {
  --heading-1-size: 2rem;
  --nav-link-padding: 0.5rem;
}

/* Override just the variables for different viewports */

@media (min-width: 720px) {
  :root {
    --heading-1-size: 2.5rem;
    --nav-link-padding: 1rem;
  }
}

@media (min-width: 1200px) {
  :root {
    --heading-1-size: 3rem;
  }
}

/* Define all our rules, consuming those variables */

h1 {
  font-size: var(--heading-1-size);
}

nav {
  background-color: lightskyblue;
}
nav a {
  display: block;
  padding: var(--nav-link-padding);
}

Making our variables responsive lets our rules be a lot simpler. Everything is flatter without the multiple levels of indentation. And we don’t need to use SCSS to attempt to reduce repetition, we can just stick with CSS!

This works not only for viewport width checks but also for media queries that check for dark mode or reduced motion or which features are supported.

:root {
  --text-color: white;
}

@media (prefers-color-scheme: light) { /* We respect a user's browser preference */
  :root {
    --text-color: black;
  }
}

[data-mode=light] { /* We allow users to switch light/dark mode */
  --text-color: black;
}

p, h1, h2, h3, h4, figure, ul, ol {
  color: var(--text-color);
}

Our CSS rules can be none the wiser to what value a --text-color is under the hood, which is set to white by default and black when the user prefers a light color scheme. Our variables vary and our rules stay the same.

Tips for concatenating URLs in JavaScript

· JavaScript · Patrick Smith

You might have a base URL from configuration, that you then concatenate with paths to produce a full URL. Say an API URL you fetch from.

But should you provide the base URL with or without a trailing slash? e.g. Should you have https://api.example.org/ or https://api.example.org?

If you simply combine the strings together, you can end up with double slashes:

const baseURL = 'https://api.example.org/';

const productsURL = baseURL + '/products';
// 'https://api.example.org//products'

We could try and check for the double slash, but that’s a pain:

const productsURL = baseURL +
(baseURL.endsWith('/') ? 'products' : '/products');

Would you just rather not worry about this? Turns out we can with the built-in URL class. It’s supported in all modern browsers (not IE).

const baseURL = 'https://api.example.org/';

const productsURL = new URL('/products', baseURL).toString();
// 'https://api.example.org/products'

Isn’t that better? It’s also available in Node.js and Deno, so we can use the same technique everywhere.