Accessibility on OS X

Session 207 WWDC 2014

OS X is known for its unsurpassed level of accessibility. Find out about an all-new OS X accessibility API to make adding accessibility support to your apps even easier. Discover how to add support for VoiceOver, Switch Control, automation and other assistive-technology clients to work with your OS X applications. Learn advanced techniques to make complex controls accessible with only a few lines of code.

Welcome, welcome to Session 207: Accessibility on OS X.

My name is Patti Hoa.

I'm a software engineer on the OS X Accessibility team.

Today my colleague Chris Dolan and I are extremely excited to tell you about this brand new API was have installed for you that's designed to make your life simpler.

But before I talk about that, I want to just touch up on the importance of accessibility, and what it means for your application to be accessible to everyone.

Then I'll show you some examples of how to use this new API to make some UI's accessible, and then I'll also show you some tools that you can use to verify your changes.

Then in the latter half of this session, Chris will come up and give you a live demo of making a game accessible.

So, at Apple, we really care about providing the best platform for all users to have that great and wonderful experience when using your application.

And when I say all users, I mean users with various ranges of abilities.

That includes those who may be visually challenged, and may...

(excuse me) ...those who may be visually challenged and have trouble seeing the colors and the graphics on the application: those who are deaf and hard-of-hearing, who may not be able to hear the sound feedback in the application; those who may have mobility limitation, and may not be able to use the physical mouse or keyboard.

Well to achieve the goal of making sure that everyone could have equal access, at Apple we work really hard to provide tons of accessibility solutions built right into OS X, and that includes products such as: VoiceOver, designed for the visually impaired user; Switch Control, designed for mobility impaired users who may only be able to use a single switch to operate the computer; Closed Captioning for the deaf and hard of hearing; and tons and tons of other great accessibility features built right into OS X.

But all of these features are simply tools for the user to use your application.

After all, it's your application that they're looking at, whether or not it's to read an article or to watch a movie.

It is your application that they're interacting with, whether it's to play a game or to write a term paper.

It's your application at the end of the day that they're looking forward to use every day.

So how do you make sure that your application is accessible to everyone?

Well we've built a foundation for you to build your application.

And we have this what we call "Accessibility API" that you can implement to make sure your application's accessible to everyone.

So, I want to spend the rest of this session telling you about this API, but the first thing I want to tell you is to give you the big picture of how this Accessibility API works in the system.

So first there's your application, and then we have what we call assistive softwares, such as VoiceOver and Switch Control, that help users to perceive, understand, and interact with your application.

And that happens through a channel, on what we call...

Accessibility API.

And so, that's what I want to talk to you about today: it's this Accessibility API which, for OS X Yosemite, we created from the ground up this brand new API.

I'm excited to tell you about this.

So, when we were first designing this API we had a few things in mind...

Actually, just one goal, and that is to simplify to make it easy for you to use.

And to show you just how easy it is to use this API, I'll walk you through a few examples.

So what you see on the screen first is a window that contains, like, a media player controller.

So what we're going to do is focus on the UIs in the middle.

What I see here is: a rewind, play, and forward button.

Well how did I come to that conclusion?

Because visually you can see three distinct icons, and each of those icons represents something.

Well if you're not sighted, and you depend on assistive software like VoiceOver to help you perceive what's on the screen...

Well, this is what a VoiceOver user would probably see.

Just a bunch of buttons.

They wouldn't know what to do with them.

Even worse, if you implemented them as custom views, they'll see nothing.

Not terribly accessible is it?

Well today I'm going to show you how to make these UIs accessible.

So what we'll do first is we'll focus on just one button in the middle: the Play button.

If you say you're using AppKit control you're in luck, because you get most of that accessibility for free.

By default, AppKit will already fill in all the accessibility information for that piece of UI knowing that it's a button.

However, AppKit is not psychic.

It's not going to be able to know what the function of that button will do.

That's something only you, the developer, will know...

and so that's where you come in: to help label this button.

So, there's two ways you could do it.

You could go into Xcode Identity Inspector.

Under the Accessibility Identity section, you could just add a description: "Play."

So this, you could do that in your zip file.

Or, if you'd like to do this programmatically, you could simply go into your initialization code and in your button cells simply set the accessibility label property to be the localized string that you want it to be.

And with just that alone, now a VoiceOver user could be able to be perceived this as a Play button.

What makes it so easy?

Well with the new API which is a method-based API we've converted all the attributes into properties.

So just like any objective-C property, you could now get and set the property directly on the object itself.

So you no longer have to subclass.

So whenever possible, use AppKit Control.

But for any reason you can't use AppKit Control and you have to do your own stuff, like creating a custom view for each of the UIs, well in this case, obviously VoiceOver will not be able to see anything on the screen.

So now you're wondering, "Great, is there a lot more I have to do?"

Well the good thing is: it's just as easy if you use this brand new API.

You could continue to use the accessibility property I just mentioned.

I gave you an example of tweaking one of the properties the label property.

There's tons of properties you could use.

But one of the challenges for the developers is knowing exactly which property you have to implement.

So now we've introduced an accessibility protocol that's designed to take that guesswork out of the equation.

The protocols will guide you through that whole implementation process so you know exactly which property you have to implement, and we have protocols that should cover most of the commonly used types of UIs out there.

So how do you go about implementing this?

Well first you have to pick a protocol.

So, we have a list of protocols you could choose from.

So you should pick one that corresponds to the look and feel of your UI; the way or the function of that UI.

So in our case we have the example I was showing you earlier with the Play button.

It looks and behaves like a button.

So we're going to pick the button protocol.

So, in your interface file simply say, adhere to the NSAccessibilityButton.

So now you add that; you compile.

The good thing is, now accessibility compiler [1]will tell you...

will give you some warning and tell you what you need to implement.

So in this case, you have to implement the accessibilityPerformPress and accessibilityLabel methods.

So let's go ahead and do that.

So in your implementation file, simply for the accessibilityLabel method just return a localized string of the word "play".

For the accessibilityPerformPress, we simply need to perform the action of pressing that button.

So what's next?

There is no next step.

That's all.

That's just how easy it is to implement accessibility even for a custom view.

So what makes it so easy?

Well it's because AppKit's doing a lot of work on your behalf.

By simply using this protocol, AppKit will infer that these elements are accessibility elements.

And depending on which protocol you use, AppKit will auto-populate information like what the role is.

So if, for example, if I use the NSAccessibility button protocol, AppKit will automatically infer that the role for this is "button."

So as you can see how easy it is to use, I also want to kind of give you a little bit more detail about these protocols.

First of all there's the base protocol, which is what we call the NSAccessibilityElement protocol.

It has a few required methods like the frame and the accessibility parent.

Those are basic information that all accessibility elements should have.

And then you build on top of that.

We have all the other protocols, like the button protocol I just talked about, which has two required methods, the accessibilityLabel and the accessibilityPerformPress.

And as you saw earlier, Xcode compiler already warned us about those methods.

So that's just how easy it is to implement a custom view.

By the way, the protocols are optional.

So you don't have to implement if you don't want to, but it's really, really handy.

So let's go through another example that's a little bit more complicated.

On the screen you see six different image shapes.

The way the developer may have implemented is simply a custom view where they're doing their own drawing.

So if you have something like this, someone like a VoiceOver user will still need to be able to know that there's six distinct UIs sitting on the screen.

So you have to give an accessibility representation for each of the images that's being displayed on the screen.

So how do you do that for UIs that you're rendering yourself and you don't have an NSView backing?

Well, for those of you who are familiar with the old sample code, we have something called [inaudible] element[2].

And now with the new API we have a formalized version of that called NSAccessibilityElement.

You can use this class to support all those UIs that do not have a backing in NSView.

So let's see how you'd go about implementing this.

So for the example earlier with the image the six shape images for each of those images you want to create an NSAccessibilityElement instance for that.

So you create one of those instances, and then you set up some of the accessibility properties for that, such as who the parent is, what the role is...

Well, in this case we're just going to say these are image role.

And then give it a unique label, and then set up what the frame is.

So when that custom view containing custom view is being asked for the accessibilityChildren, then this is where you return your array of NSAccessibilityElements.

And one thing I do want to note is: you should keep these accessibility elements alive as long as they are on-screen.

That's because assistive software like VoiceOver could be asking for information about these objects at any time through IPC calls.

So as long as they're on the screen, cache them around.

Okay so that was pretty simple, even for something like that, where you are rendering your own UI.

So there might be a few of you in the audience who may have already implemented accessibility with the old API in your application and you're wondering, "well how does this apply to me?"

Well, if you already added accessibility into your application, there is no extra work for you.

Your old API code will continue to work just fine because the new API is binary and source compatible, so you don't have to worry.

But if you do like to try out the new API, and we do encourage you to do so, you could continue to do so.

The old code will continue to work alongside the new code.

So I just told you why you should make your application accessible, and I ran through a few examples of how to use this brand new API to make some UIs accessible.

You saw how quickly and easily we were able to solve the three examples I've shown you.

And it really is fast, and it will shave some time for you to develop in making sure your app is accessible.

So with some extra time you may have on your hands, I really hope you could take some of that time to do some testing.

Because after all, you know, the code you add?

You want to make sure that it will be usable by everyone.

So how do you go about making sure that your app is accessible after you make those changes?

Well, we have two tools you could use.

The first is Accessibility Inspector.

This is a tool that displays all of the accessibility information for any piece of UI that's currently under the mouse.

And with the newest version of the Inspector, we will now display the accessibility properties of that UI.

So, this is really helpful, so you know exactly which properties you may need to tweak.

The second tool we have is called VoiceOver.

VoiceOver is a screen reader designed for the visually challenged users to be able to explore and interact with the content of the screen.

And the users will get feedback through speech or braille.

So how do you go about using this?

First you've got to turn it on.

If you just remember the shortcut: command F5, that will turn it on.

Or you can go into the Accessibility Pref Pane.

There's an Enable VoiceOver checkbox.

Simply check that and you can turn VoiceOver on.

So the very first time you turn VoiceOver on, it's going to prompt you to see if you want to go through a tutorial.

So if you just click on the Learn More button, than it will run through a tutorial with you.

So I really encourage you to try that.

Run through the tutorial.

Now, VoiceOver is a very powerful tool, so it has hundreds of commands.

Well, today I'm going to show you just five simple commands you can use to be proficient in testing with VoiceOver.

The first of that is how you navigate from one piece of UI to another: and that's "control, option, right arrow."

So just remember that once you have VoiceOver turned on, any time you press control and option, any other key you press at the same time will automatically turn into a VoiceOver command.

So we have "control, option, right arrow" to go to next, and if you want to reverse, you do "control, option, left arrow."

And if you want to press a button or activate something, simply do "control, option, space."

This is very similar to pressing a space bar on something that has a keyboard focus.

And then we have two more commands.

One is Enter Group which is "control, option, shift, down arrow" and Leave Group: "control, option, shift, up arrow."

So what is "group?"

Well VoiceOver has this concept of "group" and it goes like this: If you have, on the screen...

what I have on the screen is just some window with lots of UIs.

Well, to be able to navigate quickly to a certain piece of UI at any moment, VoiceOver has this concept of grouping.

On the screen you see three different groups: one is the toolbar; the other one is the table of folders; and also the collection view of images.

To be able to interact...

or, you know, enter and exit these groups, like I said earlier you could just press the Enter Group or Leave Group command.

So with just these five VoiceOver commands alone, you should be pretty good in testing with VoiceOver.

So now that I have shown you the tools and run you through some examples using the API to implement some of the UI examples I've shown you earlier, I would like to bring up Chris Dolan to come up to give you a live demo of making the Tic Tac Toe game accessible.

[ Applause ]


Thanks Patti.

Hi, my name is Chris, and I'm a software engineer on the OS X Accessibility Team.

And I'm really excited to show you just how simple and just how easy it is to add accessibility to your app with our brand new API.

So to do this, I've written a little test app here, and it's a very simple game of Tic Tac Toe.

So in this case the board is full, the game is over, and it says the O player has won.

I can come in and restart the game, place some pieces on the board...

I can even turn on the AI opponent and play against that.

This is a very simple application, and I want to use this kind of as our launching point to show you how you would implement all the different techniques, that Patti just told you, in this application.

But before I do that, I want to give you an idea of what this application looks like to someone who's using VoiceOver.

So, they may have just heard from social media that this is the great new app to have, or that you wrote it and they want to check it out, and this is their first experience with it.

I want you to keep that in mind.

So I'm going to use the keyboard command to turn on VoiceOver.

So here, two things have happened when I turn VoiceOver on.

You are currently on a text element.

The first is that the caption panel has shown up in the bottom corner.

And all this does is it has all of the text that's currently being spoken.

So this is really, really helpful if I'm collaborating with someone who's using VoiceOver, and they often have their speech cranked up really, really fast.

So here I can read all of the text that's being spoken, and it helps me when I'm collaborating.

The second thing you'll see is that there's a black box drawn around the X wins label.

And we call this the VoiceOver cursor.

You can kind of think of it as an alternate keyboard focus.

So just like I can press space on a keyboard-focused element to do something with that element, when I press one of the many VoiceOver commands (keyboard commands) it normally acts on the currently VoiceOver-focused element.

So now what I'd like to do is turn on a mode in VoiceOver called Trackpad Commander.

And all it allows me to do is just explore the UI with my finger.

Just like VoiceOver on iOS, I can move around the interface and VoiceOver will speak the descriptions of all the items underneath my finger.

I'm going to turn that on.

Trackpad Commander on.

And now I'm just gonna explore around the interface, and you'll see a blue circle wherever my finger is.

Close button.

Minimize button.

Dimmed, zoom button.

Great. So the toolbar is looking good.

But you'll notice anywhere where there's no elements there's this sound being played [beeping].

It says this is empty space [beeping].

Tic Tac Toe.

Okay. Title is good.

[Beeping] empty space here.

X wins.

Okay the label shows up fine.

[Beeping] more empty space.

Ah, we've hit our first problem [beeping].

There's nothing being reported here for accessibility for this checkbox.

So this is one of the problems we'll have to fix.


Difficulty's fine.


As well as the level.

Button, button.


2. Button, button.

Delete. 1.41%.

So we saw there's a problem with the buttons.

It just says "button."

So if I'm not a sighted user, I don't understand what's going on with this button; what does it do when I click it?

[Beeping] More empty space.

And again, the Restart Game button's the same way; there's absolutely no information for accessibility there.

What about the grid?

Well I had the same problem here.

The grid isn't even being reported to accessibility.

VoiceOver off.

So as you can see, the user experience for this application is quite poor when using VoiceOver.

A lot of the major functionality for this app just doesn't show up.

I can't play a piece.

I can't restart the game.

I can't play against the AI because I can't click that checkbox.

So what I'd like to do is take you through each of these individual elements and show you how to make them accessible.

So here's my Xcode project.

And before we even talk about the code, I just want to orient you to, kind of, the layout of this project.

So over here...

this is a classic MVC style app.

I have all of my models, and these are the files that encapsulate, you know, the Tic Tac Toe board...

and the game rules...

and what it means to win the game.

We're not going to touch any of the model files here.

This is the game state.

We don't need that.

The next folder is all of the views.

So we have a lot of custom UI in this application and we need views to back them.

These are all of the files that we use to do that.

This is where we're going to be spending a majority of our time in the code.

We also have the controller section.

The AppDelegate is currently empty.

And the Tic Tac Toe view controller is the thing that hooks up all the UI interactions with the monologue jacks.

The last thing I want to point out is the main menu nib.

This is the one and only nib for this entire project.

And this is actually where we're going to start.

So the first elements we're going to work on are the plus and minus buttons here for the difficulty.

If you remember, this is one of the items that we could land on, but there was no contextual information about what these buttons did.

So I'd like to show you how to add accessibility to that in two different ways.

The first is actually quite simple.

I'm just going to select that element in Interface Builder.

And then up in the top right I can open up the panel.

And the third icon from the left is the Identity Inspector.

And in here is the Accessibility Identity information.

So this is where I'm going to add the description for this button.

So what does this button do?

Well, when I click it, it decreases the difficulty.

So I'm just going to type that in here.

Great. And that's all I had to do.

Very simple.

So what about if I decide that I want to do the same thing, but in code?

Well it turns out that's really simple too.

So I can go over to my view controller.

And in my awakeFromNib, here I can pull out the button cell.

And I have an outlet to that button.

And then I can use one of the new accessibility properties to just set the accessibility label.

And remember, you always want to localize these strings.

Okay. And this is the increase difficulty button.

So I'm just going to add that in.

Okay. Just like that.

That's all I need to do.

And with that, now when a VoiceOver user lands on these plus and minus buttons, they'll be read as the increase difficulty or the decrease difficulty buttons.

So why did we get that accessibility for free?

Why did they even show up in the first place?

Well, this custom class is actually a subclass of NSButton.

So we've done a lot of work behind the scenes to bake accessibility in to all of the standard AppKit controls.

So whenever possible, try to use those because we've done as much work as possible for you.

The one thing we needed to do is just add a description which is quite simple.

So now that we've worked on the "plus" and "minus" buttons, let's move on to the Restart Game button.

You might recall that this was one of the items that...

nothing was reported there for accessibility.

Let's take a look at why.

So I have a class for this button.

And the first thing I immediately notice is that it's an NSView subclass.

I'm doing a lot of extra work behind the scenes to make this view act and look like a button.

This includes all of my own keyboard and mouse event handling, as well as all of my own drawing.

I'm doing a ton of extra work here.

Well, how do I add accessibility to this element?

It turns out it's also quite simple.

All I need to do is pick the accessibility protocol that best represents this object.

The protocol for this is the NSAccessibilityButton protocol.

Now that I've conformed to that protocol, I can move into my implemenntation file.

And the first thing I see is I get two new warnings.

So this is really, really helpful for me, because now I know exactly what I need to implement to add accessibility to this custom control.

The two methods here are accessibilityLabel and accessibilityPerformPress.

So let's take those one at a time.

I have a section here for Accessibility.

The first one is accessibilityLabel.

Great. Now what do I want to be returned here?

I happen to know that this button is only ever used to draw the Restart Game button.

So the label for this is just going to be "restart game."

That's it.

So now I can go back up to the top of my file.

I notice that warning has gone away.

So I only have one more method to implement.

And that's accessibilityPerformPress.

Let's do that.


So what should happen here?

Well, when I use the mouse to interact with this button when I click it something happens, right?

That same something should happen when an accessibility client says, "hey, I want to activate this item."

So in my case, I happen to have a method called pressDown...

or performPress rather.

And performPress is what gets called when the mouse handling logic says "yes, this button has been pressed."

So I want to call that same, exact method.

And now you notice that accessibilityPerformPress return is a Boolean.

This is a yes-or-no, "did I handle this?"

event. And I'm always handling it, so yes, I return "YES."

And with that I can go back up to the top of my file and I see all of my warnings have gone away.

So that's it.

The protocol has guided me through what I needed to do to add accessibility.

I implemented that and I'm finished.

So now that this lower right section's finished, I want to work on the Artificial Intelligence checkbox.

If you recall again, this was another element that wasn't visible to accessibility at all.

So I have my header file here for the checkbox.

And again I see the same situation I had with the button.

It's an NSView subclass.

So I do a lot of work to make it look and act like a checkbox.

So in this case, I need to pick a protocol.

And the protocol for this is the NSAccessibilityCheckBox protocol.

And now when I go into my implementation file I get a few new warnings.

So this tells me what I need to do to make the checkbox accessible.

So the three warnings I have here are accessibilityValue.


And accessibilityPerformPress.

So I'm going to take those one at a time.

So the first one, we've seen this one before, is accessibilityLabel, so I'm going to do that first.

So what should be the label for this checkbox?

Well this is a control that I designed and I thought I might reuse in other places.

So I actually have an iVar around that keeps the checkbox text.

This is the string that actually gets rendered in and drawn in the drawInRect method.

So I can just return the checkbox text here.

Great. So one of my warnings has gone away.

The next one I want to work on is accessibilityPerformPress.

So just like the button, when I interact with this control using the mouse, something happens that changes the checked state.

I need that same something to happen when the accessibility clients say "hey, I want to interact with this element."

So that's the accessibilityPerformPress.

And I have a method called toggleCheckedState.

And this is what gets called from the mouse handling logic.

And just like with the button, I return "YES," I did in fact handle this action.

So now if I go back up to the top I see that I still have one more method I need to implement.

And this is accessibilityValue.

And at this point I ask myself, well, "what is the value for a checkbox?

What am I supposed to return?"

We've worked really, really hard to try to answer all of these questions in one place.

We tried to make NSAccessibilityProtocol file the one-stop-shop for this.

This is where all the protocols are implemented or defined.

So in another tab I have this protocol's file.

And there is the NSAccessibilityCheckbox protocol right here.

And I see under the required methods the AccessibilityValue returns an NSNumber.

Okay, so that answers my first question.

And it says I return "yes" if checked, or "no" if unchecked.

Great. So now that I have this information, I can come down here and implement that method.

So here I have another iVar around, which is "am I checked or not.?"

I can use that to return "yes" or "no."

Oh return.

All right.

Okay. So now I can go back up to the top of my file.

I see all the warnings have gone away.

So this is all I need to do to implement an accessible CheckBox.

So now the entire right-hand side of our application has added some basic accessibility to it.

So let's work on the next part, which is the grid, and this is perhaps the most difficult part.

Again, I'm going to back into my project, and I have a view representing the board it's the board view.

And here I notice: it's, again, an NSView.

I'm doing all of my own drawing here.

And in fact this class draws the board and all of the pieces.

So I need to make this accessible.

And I need to pick a protocol now.

So what protocol do I need?

Well the way that I like to think about the Tic Tac Toe board is it's really a collection of squares, right?

Every time I interact with the board, it's not so much a board I want to play this square; I want to put my piece there; I want to get three in a row to win; I want to block my opponent from getting three in a row.

And so this board is really a collection to me.

And the way that that's...

the protocol that you can use to represent that is the NSAccessibilityGroup protocol.

It's a collection of things.

Great. So now I go to my implementation file.

And I notice I have no warnings showing up.

Okay. I have no warnings.

So what does this mean?

Well I have no required methods that I need to implement for the accessibilityGroup protocol.

But just like with what we saw with the other elements, I can still add accessibility to it.

So what's the first thing I want to do?

Well, the board view when I land on it it's a group and I want some label to describe it.

So just like with all the other controls I'm going to add a label here.

An accessibilityLabel is very simple.

So what am I going to return here?

Well just, it's the Tic Tac Toe board.

So when the VoiceOver cursor lands on this, it says this is the "Tic Tac Toe board" group.

Okay, so I have a group that contains things.

Well what are these things?

They're individual squares.

But each of those squares doesn't have a backing view to them.

So I need to create some object to represent it to accessibility.

And the way that we've done this is with the NSAccessibilityElement.

Patti showed you in the slides how you'd create an instance of this inline.

And what I've chosen to do here is just create a subclass of it in another file.

So I have a subclass here called the TicTacToeSquare AccessibilityElement.

And it's a subclass of NSAccessibilityElement.

It has one initializer, which takes a row, a column, and a delegate.

And it has three properties: a row, a column, and a delegate.

So the delegate method or the delegate is just a class that can answer questions about "hey, what pieces are at this location on the board?

Is the game over?

Is it still in progress?"

So it can answer a lot of the questions that this piece is going to need to ask.

So I have this element representing it.

Well, I'm going to pick a protocol now to use to implement it.

So what best encapsulates what a square does?

Well when I click on it, something happens.

I place my piece there.

I put my piece there.

I play it, right?

And elements where you click them to interact with them and they do something are buttons.

So I can conform to the accessibilityButtonProtocol here.

And now when I move into my implementation file, I'll get a bunch of warnings for the items that I need to implement.

So the four warnings I get here are accessibilityParent, Label, PerformPress, and Frame need to be implemented.

So I'm going to take these one at a time.

For the frame and for the parent, I'm just going to return whatever my superclass' implementation is.

So at some point these will need to be set, so keep that in mind.

The accessibilityLabel is a little bit more interesting.

And this is the description for a particular square.

So what I'm going to do is ask my delegate for "hey, what's this square at my row and column?"

And this is actually an instance of the model object representing a square on the board.

And then I can ask the board, using one of its class methods, "what's the description for this square?"

So this is going to return something like, "this is an X square at the top right."

Or an "O square in the center."

Or an "empty square at the bottom left."

And so when I land on this element, that's what I want to be spoken out.

And then the last method I need to implement is accessibilityPerformPress.

So when this item is pressed, what should it do?

Well, I want to play my piece there; I want to play that square; I want to make my mark there.

And my delegate knows how to play a square at a row and column.

So I'm just going to ask it to do that and again, return "yes, I handled this event."

So with that I can go back up to the top of my file and I see that all the warnings have gone away.

So that's great.

I have, now, a class that represents an individual square for accessibility that doesn't have a backing view.

So now I need to go back to my group.

I need to create instances of this class to represent each square.

So I'm back in my board view.

And I want to say, "this group has children of these elements."

And the way to do that with our API is to override the accessibilityChildren method.

So I'm going to walk through it looks like a lot of code; I promise it's not I'm going to walk through, line-by-line, what this does.

The first thing is, I'm overriding the accessibilityChildren array.

So, I'm the accessibility ChildrenGetter and returning an array from it.

I have iVar around.

So if I've already created my children, I don't need to create them again.

And if I haven't, I create an array to hold all of the accessibility Children.

And then I set up two variables that I'm going to be using during my computations.

Now what I need to do is create an instance of that accessibility element for every square on the board.

So I'm going to iterate over all the rows and all the columns...

and then instantiate one of those accessibility elements for the square.

Now remember that the parent and the frame were just returned as whatever the super-classes' implementation was.

So I need to make sure that they're set somewhere, and that's what I'm going to do it here.

So I can set the accessibility parent using a property.

And I just set it to myself because the parent of a square is the board.

And then I need to set the frame.

Typically the accessibility frame has always been given in screen coordinates.

And It's important for us because that's what we use to draw the VoiceOver cursor around a particular element.

And we were thinking about this with the new API and saying, you know, it'd be really cool if we could just say, here's my frame relative to my parent.

And then I don't have to do any work, when the window moves or my parent moves around, to recalculate my frame in screen space.

So we've added this nice convenience property to NSAccessibilityElement and it's called accessibiltyFrame InParentSpace.

It does exactly that.

I can calculate the actual rect that I'm using during the for drawing.

That's given in my parent space.

And I can set that as the accessibilityFrame InParentSpace.

And now whenever something moves, we have enough information on our end to recalculate where the frame is, and you don't have to do any of that bookkeeping.

So now that we've created this accessibility element for each square, we want to make sure that we add them all to the array.

And then as Patti said, you want to make sure that you cache these elements.

So at any point in your applications lifetime where this item is being drawn onscreen, the accessibility element representing it has to be there for accessibility to be able to query.

And then lastly, remember we overrode the getter here so we need to make sure we actually return these children.

So with that I can go back up to the top of my file...

and I finally just made this really complicated UI accessible with not too much extra work.

I see that all of my warnings have gone away (well we didn't have any warnings here, for example).

But this has now added a basic level accessibility to my app.

And so let's take a look at what that looks like now.

And the way I'm going to verify that my changes worked, is by using one of the tools Patti mentioned.

It's called Accessibility Inspector.

And you can launch it from the Xcode menu under Open Developer Tool and Accessibility Inspector.

Again, what this does is it shows you the accessibility information for the item under the mouse.

So here, there's three sections that are showing up.

The very top is the accessibility Hierarchy.

So if this is analogous to...

it's kind of like the view Hierarchy.

If your accessibility elements aren't in the accessibility Hierarchy, they're not going to be available to accessibility clients.

Much like a view that's not in the view Hierarchy won't be shown.

The next section is the Attributes.

So these are all the properties that we have now added onto accessibility elements, and you can see each of their values.

And there's also some more complicated ones like Parameterized Attributes.

So the very first thing that we worked on was the "plus and minus" one.

And remember this was to increase and decrease the difficulty.

And we needed to just add a label there.

It was a standard AppKit control.

And what I can see is that the access...

down here is showing up as decreased difficulty.

So this is good.

And we know that this element is now labeled.

It's going to be spoken when it's navigated with VoiceOver.

Same thing with the Increase difficulty button.

The label is there, which is good.

What about the Restart Game button?

Well remember this wasn't even available to accessibility, and now we see that it's in the Hierarchy as an accessibility button.

And it also has a label of "Restart Game."

So this is great.

it's going to be read out as a Restart Game button.

Similarly with a checkbox, it's now in the view Hierarchy (which is awesome) so it will show up to accessibility clients.

It says it's a checkbox.

It has a label of AI opponent.

And now the grid.

So the grid shows up as a group.

And one of the accessibility properties is the accessibility Children.

And we see that it has nine items and they're all buttons.

So if you take a look at just one button, it says it's in the Hierarchy, as well as it has a label for "it's the empty top left."

The next one says "empty top."

"Empty top right."

And you'll notice here also there's an action section on the bottom saying PerformPress.

And it says, this is what this element supports for actions.

So that's actually really great.

Okay so now that I've audited my app with Accessibility Inspector, I'm fairly certain that the accessibility I've implemented is correct.

So now I'm going to turn on VoiceOver; I'm going to audit it using VoiceOver.

VoiceOver on.

Tic Tac Toe.

Window. AI Opponent.


Checkbox has keyboard focus.

Great. So we can now land on this element.

Check. AI Opponent.


I can activate it.


Decrease difficulty, button.

Press. Press.

Press. Decrease difficulty, button.

The buttons are labeled, and they support the actions.

2. Increase difficulty.

Restart Game, button.

Press. Restart Game, button.

I can press to restart the game if I had the game in progress.

Tic Tac Toe board ,group.

I also land on the board group.

Interact with Tic Tac Toe board group.

9 items. Empty top left, button.

And I can move into this group to see the different pieces.

Empty top, button.

Now if I place a piece there using the Activate option.

Press X top, button.

Empty top left, button.

Press X top left, button.

VoiceOver off.

I can play a full game of Tic Tac Toe now.

So this is really exciting, and I hope you've seen that with just a few lines of code we can really walk you through what you need to do to add accessibility to something like this.

And I hope you really see that the level of accessibility is quite drastic.

Before, there was hardly any, and now there's almost full support.

So there's a couple more things that you can do here to make this app even more accessible.

I'm just going to point out one.

Suppose for example that I'm playing this game with a user who's using VoiceOver and they're on the checkbox.

And focus is on the checkbox.

They can activate the item using "command, option, space."

But I can also go in and click that checkbox with my mouse.

So how does a VoiceOver user know if I've changed the state of something out from underneath them?

Well we've solved this problem using Accessibility Notifications.

And there's always been some questions about, "which ones do I use?

When do I use them?"

And we really tried to answer that with the new protocols file.

So again, this is your one-stop-shop, and you can really go back there.

Here in the checkbox protocol declaration, there's a comment which tells me about the notifications I need to post.

So in this case it says, "the AccessibilityValueChanged Notification needs to be posted whenever accessibilityValue changes."

Recall that's the checked or unchecked state.

So if at any point it changes for any reason, I need to send this notification.

And it's really easy to do.

So I'm going to go back to my checkbox view.

And if you recall, we had the toggleCheckedState and this is what got activated when you used the AccessibilityActivate action.

And here's where I need to post that notification.

So I can do that with NSAccessibility PostNotificaton.

The element this notification should be associated with is the checkbox itself.

And then the notification type is an NSAccessibility ValueChangedNotification.

That's it.

So again, some of the more advanced accessibility items now don't actually take that much more code either.

And so now if you were to run this app again, and you were collaborating with the VoiceOver user, and you clicked that button they would now be announced ah, the new state would now be announced to them.

So that's the end of the demo.

And I hope what you've seen is that we've tried to make it as easy as possible for you to add accessibility with our new API.

I should also mention that we have a sample app you may have seen this in the past we call it Accessibility UIExamples.

And what it is, is a collection of all different types of elements.

So here there's a button, text, images.

We also have more complicated UI like layout areas, collapsible outline views, table views.

And what we've done is implemented each of these using different methods.

So for example, subclassing from standard AppKit controls, making it a subclass of NSView, but also OpenGL CALayers we have examples for all of those.

And for this release we've gone through, we've ripped out the accessibility that we had, and added it right back in with the new API.

And what we found was a drastic code savings: many, many fewer lines of code.

And what we hope to do is have this available as a reference for you.

Say "hey, I want to learn how to use this protocol," you have an example in a concrete implementation that we've done.

This is available, along with the Tic Tac Toe app, on today.

Please go check it out.

Download it.

We also have, in this particular example, a nice readme file that has kind of a developer quickstart on how to use our API.

So with that, in summary, we really took this release to think about "how could we make it easier to add accessibility to your application?"

What we came away with was a brand new, really easy-to-use API.

And it's really easy to use because all of the accessibility attributes are now properties on the objects.

So they're really easy to set.

We also have the accessibility protocols, which guide you through the items that you need to implement in order to make your custom UI accessible.

And then lastly we formalize the faux UI element class into NSAccessibility Element.

And it's there for you to be an accessibility backing object when there's no UI view for it, or NSView backing it.

We'd like to encourage you to test with VoiceOver.

It ships with every Mac and it's a great way for you to see what our customers are going to experience using that assistive technology with your application.

If you'd like to just kind of debug a little bit more, we have Accessibility Inspector there to really get in at what exactly is going on with your accessibility element.

And lastly, we wanted to support you in this transition to the new API.

And we really want to encourage you to use it.

And so we've built up these really great developer examples that we've now released, and we hope you can use as a reference for your implementation.

If you'd like more information about our team, or accessibility, or frameworks in general, please feel free to reach out to our App Frameworks Evangelist, Jake Behrens.

His email is

And if you have more technical questions, you can take a look at the documentation on, as well as ask questions on the dev forums.

If you liked this session, and you're interested in finding out how accessibility works on our other platforms, there's an "Accessibility on iOS" session in this room, right after this presentation.

And then a Web Accessibility presentation on Friday at 9:00 am.

Thank you so much for coming to our session.

We really appreciate you being here.

And from all of us at Apple, we hope you have a fantastic rest of WWDC.

Thank you very much.

[1]Cannot tell if speaker is saying "accessibility compiler" or "-Xcompiler".

[2]I think she's saying "forUIElement".

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