How to Turn Your Inform Game Into an iOS App

Andrew Plotkin edited this page Dec 30, 2016 · 6 revisions

iOS Fizmo is a Z-code interpreter for iOS. It's designed to be packaged up with a single game file -- a one-game app. (This is the opposite of iOS Frotz, which is designed to host lots of game files.)

Would you like to package up your Inform game as an iOS app? Probably! Is it easy? Yye-- well, no, not easy. But it's manageable.

Let's start with:

The Requirements

You must have an Inform game compiled as a Z-code game file.

If you have a Glulx game, read this page instead.

You must have a Mac and the latest version of MacOS.

You must have Xcode installed on your Mac.

(Xcode is free; you download it from the Mac App Store or from the iOS Dev Center. Yes, it's a gigabyte and a half, it's enormous.)

You must be a registered Apple iOS developer to release an iOS app. This costs $100 per year. Visit Apple's iOS Dev Center.

(You can build a test app and test it in Xcode without being a registered iOS developer. To test it on an actual iPhone, or submit it to Apple for release, you need to pony up the fee.)

(Note that when you visit Apple's dev site, it will first ask you to register as a developer -- in general -- this is free. Once your dev account exists, you'll see the option to buy an iOS developer membership for $100.)

What Doesn't Work Yet

There is no good way to upgrade your game file once you release it.

Or rather, if you do, everybody's saved games will break. You know how, in an IF game, saved game files have to match the exact version of the game? That's still true. So if you release an update with a different game file, your players will find all their progress erased. You don't want to do that to them.

(This also applies to the hidden save file that's used to launch the app in the same state the player left it. If you update the game file, that won't work; the player will see the game start from the beginning, with an extra bonus error about "checksum doesn't match.")

I have a plan for this: I am going to build a way to include multiple versions of your game file in the app. Each saved game will cause the matching game file to be loaded up. This is of course not ideal -- it means that players will be stuck in the old version of the game until they start over -- but at least they won't see their games break.

Unfortunately, even that much of a plan is still theoretical. I will update this document when the feature is available. In the meantime, the plan is "Release your game right the first time." That's a terrible plan but it's what I've got.

Menus don't work nicely.

That is, the standard Inform menus that appear in the status window. They're not broken -- you can cycle through the menu by tapping the "P" and "N" keys on the virtual keyboard. However, players who aren't already IF fans will probably be confused by this.

Overall, it is better to rebuild your game without menus, and move your HELP and ABOUT information to the app's help screen. More on that later.

What This Document Will Not Teach You

This is not an Xcode tutorial. Xcode is Apple's development environment; it's pretty good, but you do have to spend some time getting used to it. (For what it's worth, I found it much easier than Eclipse. This is not worth a lot, I admit.)

For an introduction to Xcode, and the process of releasing an iOS app, read Apple's Start Developing iOS Apps guide. (The same guide, and all the rest of the Xcode documentation, is included inside Xcode itself. There's a reason it's a gig and a half large.)

This document is also not a Git tutorial. Git is the version control system I use. You don't have to know anything about it, really. You can download all the Fizmo source code inside Xcode, and then ignore Git thereafter.

However, if you want to pick up my improvements to the interpreter, you'll have to go back to Git. The clever way to do this is to create a Git branch, store all your changes in it, and then merge my master branch into it. The easy way is just to re-download all the source code and make your changes again. Feel free to use the easy way.

Okay, Let's Get This Show on the Elephant

Downloading the source code (and project file)

  • Launch Xcode. (I am writing this document with Xcode 4.3.2.)

  • Open the Organizer window. (Windows menu, Organizer)

  • Select the Repositories tab. (Organizer window, top bar, Repositories)

  • Press the + button in the lower left-hand corner. This brings up a pop-up menu. Select Checkout or Clone Repository...

  • The "Checkout or Clone" dialog appears. It has a field for Location. Paste in this URL:


  • Press the Clone button. (Lower right of the dialog.) Ignore the "Authentication required" warning -- it's not actually required.

  • A "Clone" dialog appears, asking for a place to create the directory iosfizmo. Navigate to wherever you want this and press the Clone button.

  • After a few moments of work, the dialog will display "Clone of 'iosfizmo' complete." Press the Open Project button. (Lower right of the dialog.)

  • You now have a project window for IosFizmo.xcodeproj.

(Note: this gets you the most current, bleeding-edge IosFizmo source code. This should work for you -- I don't plan to break the build. If you want to use the latest stable release, you'll need to do additional work.) (TODO)

Test the interpreter

  • Find the Scheme pop-up menu. (Project window, top bar, the wide pop-up menu on the left.) Click the right side of this menu and select iPhone 5.1 Simulator.

(Or whatever is the latest iPhone OS version you see. If the pop-up menu says "Edit Scheme...", "New Scheme..." and so on, you clicked the left side. Don't do that.)

  • Click the Run button. (Top bar, left end, the big triangle.)

(If you hold down this button for a moment, you'll get a pop-up menu of Run, Test, Profile, Analyze. You want Run. Or just click the button instead of holding it down.)

  • The project will go through a cycle of building and attaching to the app.

(If the project seems to get stuck on "Attaching...", wait another minute or so. When you get tired of waiting, press the Stop button (the big square), wait for it to turn grey, and then press Run again.)

  • The iOS Simulator will appear. (This is a separate app, but Xcode manages it.) You should now see Colossal Cave running in a simulated iPhone. You can play it!

  • To test on a simulated iPad, select iPad 5.1 Simulator in the Scheme menu and hit Run again.

Know your way around your iosfizmo directory

The directory contains a plethora of files. Some interesting ones:

  • IosFizmo.xcodeproj: The Xcode project file. If Xcode isn't running and you want to start working on your app, double-click this.
  • IosFizmo-Info.plist: Some important app configuration information.
  • fizmo (subdirectory): Source code for the Fizmo interpreter (Christoph Ender). This is the portable Z-code interpreter engine.
  • iosglk (subdirectory): Source code for the iOS Glk display library. This is the general iOS display library. (This directory contains its own Xcode project file, but you should ignore that.)
  • TerpSrc (subdirectory): Source code specifically for iOS Fizmo. This glues together fizmo and iosglk, and also handles the four app tabs.
  • Resources (subdirectory): All of the interface layout files (Interface Builder files -- .xib). These define the appearance of the screens and menus in the app. (Note: more resources are in iosglk/Resources.)
  • Media (subdirectory): Interface graphics for the interpreter. Buttons and icons. (Note: more graphics are in iosglk/Media.)
  • WebSite (subdirectory): HTML files for the in-app "help" and "license information" screens.
  • FizmoLocales (subdirectory): Localized text for Fizmo error messages. (These are extracted from the fizmo directory, but you don't have to worry about that.)
  • Icon.png, Icon-*.png: The iOS icons. There are a whole bunch of these, in different sizes. It's a nuisance.
  • iTunesArtwork: The cover art image. This is a PNG file, even though it lacks the .png suffix.
  • Default.png, Default-*.png: The iOS launch images. These appear as the app is starting up. (Default.png is for iPhone; the other two are for iPad.)
  • Game.z5: The game file. When you download the project, this is Colossal Cave.

Know your way around the Xcode project window

Again, this isn't a Xcode tutorial (see Apple's docs for that). But I'll go over the basic "where the hell did my files go" orientation.

The project window has three columns:

  • Left: the navigator (normally a list of files)
  • Center: the primary editor (displays the source code, image, or settings you have selected in the left column)
  • Right: the utilities (lets you edit metadata or special features of whatever's selected in the left or center column)

If you don't see these, turn on the left and right buttons in the View control (the three-button widget on the right of the top bar).

(There's also a debug area, which is a pane at the bottom of the center column. That's controlled by the center button in the View control. You shouldn't need it, so feel free to close it.)

If the center column is split in half, you have the assistant view open. You don't want that. Press the left button in the Editor control (top bar, the button with horizontal lines) and the center column should unsplit.

If the left column doesn't show a list of files (or a folder with a disclosure triangle), you have the wrong navigator selected. Look at the top of the left column, and press the leftmost button (the folder icon).

(There are many ways to rearrange this layout, in the Preferences or the View menu. Go for it if you must.)

Now that you have the columns in front of you, you can open the project tree in the left column (the disclosure triangle on the IosFizmo entry). You'll see a list of folders which is similar to the directory layout I described above. (It's not grouped exactly the same way, but you'll see TerpSrc, Resources, Media, WebSite, and so on.)

Change the project's bundle name and identifier

  • In the left column, open IosFizmo (the top-level blue project folder).

  • Under that, open Other Sources.

  • Select IosFizmo-Info.plist. A list of settings will appear in the center column.

  • Find the Bundle identifier line. By default this is com.eblong.iosfizmotest. Change it to something appropriate to your app: com.yourcompany.yourgametitle.

  • Find the Bundle display name line. This is the label that appears with your icon on the iOS home screen. By default it is Fizmo; change this to your game title.

(There isn't much room on the iOS screen, so you may need to shorten the title. Test it in the iPhone Simulator to make sure it looks good. Remember that you have to exit the app in order to see the icon!)

(If the app appears with a blank white icon after this change, try quitting the iPhone Simulator -- not just the app, but the whole simulator -- and then running the app again.)

Replace Colossal Cave with your game

The easy way to do this is simply to rename your game file (.z5, .z8, or .zblorb) to Game.z5, and copy it over the Game.z5 in the project directory. Yes, you can rename your .zblorb file to .z5 -- IosFizmo won't care.

When you start your game up, you may see a spurious error message:

Release number, serial number, or checksum doesn't match.

This is just because you tested the app earlier with Colossal Cave. The app is trying to restore your earlier session, but the session save file doesn't match. Type "restart" in the game and that will go away.

Replace the game title (the title of the app's game tab)

  • In the left column, open IosFizmo (the top-level blue project folder).

  • Under that, open Resources.

  • Select TerpLocalize.strings (at the bottom of the Resources folder). A list of string definitions will appear in the center column.

Early in that file, you'll see the line:

"" = "Adventure";
  • Change the string Adventure to your game title.

  • Test it in the iOS Simulator, to make sure your title isn't too wide for the iPhone navigation bar.

Customize the game colors (optional)

  • In the left column, open IosFizmo (the top-level blue project folder).

  • Under that, open TerpSrc.

  • Select FizmoGlkDelegate.m. This file contains some methods which customize the interpreter behavior.

  • Find the genForegroundColor method. This defines the text color for the app's three color schemes. (The scheme is selected by the user with the Colors button in the game's style (Aa) menu.)

The function looks like this:

- (UIColor *) genForegroundColor {
	switch (self.colorscheme) {
		case 1: /* quiet */
			return [UIColor colorWithRed:0.25 green:0.2 blue:0.0 alpha:1];
		case 2: /* dark */
			return [UIColor colorWithRed:0.75 green:0.75 blue:0.7 alpha:1];
		case 0: /* bright */
			return [UIColor blackColor];

You can adjust the text red, green, and blue values for each of the three schemes. (Alpha should always be 1.) blackColor is a shortcut for colorWithRed:0 green:0 blue:0 alpha:1.

  • Right below this is the genBackgroundColor method. This defines the background (paper) color for the story window. (Again, in each of the three schemes.)

  • The status bar color is handled differently.

Find the prepareStyles method, and this stanza of code:

switch (self.colorscheme) {
	case 1: /* quiet */
		styles.backgroundcolor = [UIColor colorWithRed:0.75 green:0.7 blue:0.5 alpha:1];
		styles.colors[style_Normal] = [UIColor colorWithRed:0.15 green:0.1 blue:0.0 alpha:1];
	case 2: /* dark */
		styles.backgroundcolor =  [UIColor colorWithRed:0.55 green:0.55 blue:0.5 alpha:1];
		styles.colors[style_Normal] = [UIColor blackColor];
	case 0: /* bright */
		styles.backgroundcolor = [UIColor colorWithRed:0.85 green:0.8 blue:0.6 alpha:1];
		styles.colors[style_Normal] = [UIColor colorWithRed:0.25 green:0.2 blue:0.0 alpha:1];

Each case contains lines to define the foreground and background colors.

  • If you want to customize the color of a particular style (as opposed to the whole window), you can do that too. You'll need to add code to prepareStyles to set styles.colors[style_...], for the appropriate Glk style constant.

Customize the icon and cover art

In the project directory, you'll see a whole lot of Icon...png files. You need to replace all of them.

You need to retain the name and size of every icon file. Notice that some of the icons name their own size (Icon-72.png is 72x72); some don't (Icon.png is 57x57); and some have a wacky "@2x" modifier (Icon-50@2x.png is 100x100). Don't try to figure out the reasons behind all of this; it's historical remnants all the way down. Just make new icons with the same names and sizes as the existing ones.

(The "dpi" or dots-per-inch of the PNG files does not matter -- only the overall size in pixels.)

You should also make a iTunesArtwork file. This should be a 512x512 PNG file. Notice that the filename does not have a ".png" extension.

The easiest way to do all of this is to create a large version of your artwork -- 1024x1024 pixels. Then reduce that to each of the required sizes, and copy the result into the project directory. (A 1024x1024 version will be required for the App Store submission, so you might as well have that ready.)

It's important not to put in too much detail. Even though your starting image is large, it will be reduced for display -- even in the App Store. If you put the game title in the image as a text element, it will be squished into unreadability.

You might want to make a different, simplified image for the smaller icon sizes. However, I don't bother.

By default, iOS adds a gloss-highlight to your icon when displaying it on the home screen. To turn this off, go into IosFizmo-Info.plist, find the Icon already includes gloss effects entry, and set it to YES. (I know, it seems backwards. You don't actually have to include a gloss effect; you're just telling iOS not to add more.)

Customize the launch images (optional)

In the project directory, you'll see files called Default.png, Default-Landscape.png, and Default-Portrait.png. These are flashed up briefly while the app in launching. Default.png is used for the iPhone (which launches all apps portrait-style); the others are used for the iPad.

You do not have to replace these, but you might want to. (For Dreamhold, I added a low-contrast company logo to the center area.) If you change the game's default background color, you should change the background color of the launch images.

The iOS convention is that launch images do not include content. The images I provide don't even include a blank status line. (I tried adding one, but it led to an unpleasant flicker in the launch sequence. Also, the user might have selected a different column width or font size, which changes the status line's outline. So I took it out.)

Customize the help and license information screens

The WebSite subdirectory contains two HTML files, plus a CSS file that they both include.

  • index.html appears as the content of the app's Help tab.

  • license.html appears when the user taps the License Information button in the Settings tab.

You can customize these to include information about your game. Remember that you must retain the iOS Glk and Fizmo license information in license.html.

The files are normal HTML, so you can edit and test them with normal Web tools. Note that the CSS file has a special section:

@media screen and (max-device-width: 480px) { ... }

This defines a slightly different layout for the iPhone display. (Smaller fonts and margins.)

Set up the AppID and provisioning you need to test on real hardware

You cannot do this until you have registered as an iOS developer and paid the registration fee.

  • Go to the iOS Dev Center on Apple's web site. Log in. Follow the link to the iOS Provisioning Portal.

  • Select Certificates and set up your iOS Development Certificate. (I'm not going to try to give full instructions for this. The web site is reasonably helpful.)

  • Select Devices and add your mighty collection of iPhones, iPads, iPod touches.

  • Select App IDs. Press the New App ID button (top right corner).

  • In the Create App ID form, enter your game title under Description. Leave Bundle Seed ID alone. For Bundle Identifier, enter the string that you used earlier in IosFizmo-Info.plist -- my example string was com.yourcompany.yourgametitle. Press Submit.

  • Select Provisioning. Make sure the Development tab is selected, and press the New Profile button (top right corner).

  • In the Create iOS Development Provisioning Profile form, enter (Game Title) Development for Profile Name. Check your name under Certificates. For the App ID, select the ID you just created (with your game title). Check all your devices under Devices. Press Submit.

  • You will probably see your profile listed with status Pending. Reload the web page. Now the status has changed to Active. Press the Download button.

  • Go back to Xcode. Open the Organizer window. (Windows menu, Organizer)

  • Select the Devices tab. (Organizer window, top bar, Devices)

  • Select Provisioning Profiles in the left column.

  • Drag the ".mobileprovision" file from wherever you downloaded it into the Organizer window. It should appear and be listed as Valid Profile.

  • Plug your iPhone/iPad/iPod whatever into your Mac's USB port.

  • Go back to your Xcode project window.

  • In the left column, select iosglulxe (the top-level blue project folder).

  • The main column now has a left sidebar (PROJECT and TARGETS) and a center column of build settings.

  • Select iosglulxe under PROJECT.

  • Scroll down to Code Signing Identity. This has two subheadings, Debug/Any iOS SDK and Release/Any iOS SDK. Next to each of these is a light-green pop-up menu.

  • Make sure the pop-up for Debug/Any iOS SDK is set to Automatic profile selector/iPhone Developer.

  • Find the Scheme pop-up menu. (Project window, top bar, the wide pop-up menu on the left.) Click the right side of this menu and select the device you just plugged in.

  • Press the Run button. The app should compile, install, and run on your device.

Do some beta-testing

You will have to create an "Ad Hoc" build to distribute. This will use the same App ID as your development build, but you will have to create a new Provisioning Profile (under the Distribution tab, as opposed to Development. Be sure to check Ad Hoc.) The rest of the procedure is pretty much the same.

For distributing your beta build and organizing testers, I recommend the TestFlight service.

Submit it to the App Store

You create an App Store submission in the iTunes Connect section of Apple's web site. You will need a large cover image (1024x1024) and some screenshots of your app.

To create the final build, you will need a third Provisioning Profile: the Distribution tab, but this time you check App Store.

Things to watch out for

  • Test your app on an iPhone (or the iPhone Simulator) with the font size turned up. Play a few moves while watching the status line; make sure it draws acceptably.

(When the font is large, the "window width" of the status line is quite small -- it's measured in characters, after all. You may have to adjust your status-line code to fit the tighter width.)

(Note that when you change the font size or device orientation, the status line does not redraw right away. It only redraws after you enter a move. This is inherent to the Z-machine architecture, sadly.)

Clone this wiki locally
You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.
Press h to open a hovercard with more details.