iOS

# Building the Simple DirectMedia Layer for iOS 11.0+

Please note that building SDL requires at least Xcode 12.2 and the iOS 14.2 SDK.

Instructions:

1. Open SDL.xcodeproj (located in Xcode/SDL) in Xcode.
2. Select your desired target, and hit build.

# Using the Simple DirectMedia Layer for iOS with the SDL3 xcFramework

The recommended way to use SDL for iOS is by including the SDL3.xcframework which is now a build target of the SDL.xcodeproj file. An xcframework is a new (Xcode 11) uber-framework which can handle any combination of processor type and target OS platform. You can either build the SDL3.xcframework yourself or download the latest release disk image asset (*.dmg).

In the past, iOS devices were always an ARM variant processor, and the simulator was always i386 or x86_64, and thus libraries could be combined into a single framework for both simulator and device. With the introduction of the Apple Silicon ARM-based machines, regular frameworks would collide as CPU type was no longer sufficient to differentiate the platform. So Apple created the new xcframework library package.

The xcframework target builds into a Products directory alongside the SDL.xcodeproj file, as SDL3.xcframework. This can be brought in to any iOS project and will function properly for both simulator and device, no matter their CPUs. Note that Intel Macs cannot cross-compile for Apple Silicon Macs. If you need AS compatibility, perform this build on an Apple Silicon Mac.

This target requires Xcode 11 or later. The target will simply fail to build if attempted on older Xcodes.

In addition, on Apple platforms, main() cannot be in a dynamically loaded library. However, unlike in SDL2, in SDL3 SDL_main is implemented inline in SDL_main.h, so you don't need to link against a static libSDL3main.lib, and you don't need to copy a .c file from the SDL3 source either. This means that iOS apps which used the statically-linked libSDL3.lib and now link with the xcframwork can just #include <SDL3/SDL_main.h> in the source file that contains their standard int main(int argc, char *argv[]) function to get a header-only SDL_main implementation that calls the SDL_RunApp() with your standard main function.

To use the SDL3.xcframework follow these steps:

1. Run Xcode and create a new project using the iOS Game template, selecting the Objective C language and Metal game technology.
2. In the main view, delete all files except for Assets and LaunchScreen
3. Select the project in the main view, go to the "General" tab, scroll down to "Frameworks, Libraries, and Embedded Content", and drag and drop the SDL3.xcframework
4. Still in "Frameworks, Libraries, and Embedded Content", select "Embed & Sign" for the SDL3.xcframework.
5. Add the source files that you would normally have for an SDL program, making sure to have #include <SDL3/SDL_main.h> at the top of the file containing your main() function.
6. Add any assets that your application needs.
7. Enjoy!

Using an xcFramework is similar to using a regular framework. However, issues have been seen with the build system not seeing the headers in the xcFramework. To remedy this, add the path to the xcFramework in your app's target ==> Build Settings ==> Framework Search Paths and mark it recursive (this is critical). Also critical is to remove "*.framework" from Build Settings ==> Sub-Directories to Exclude in Recursive Searches. Clean the build folder, and on your next build the build system should be able to see any of these in your code, as expected:

#include "SDL3/SDL_main.h" #include <SDL3/SDL.h> #include <SDL3/SDL_main.h>

# Using the Simple DirectMedia Layer for iOS by adding the SDL3 Xcode project

To maintain compatibility with older Xcode versions than version 11 you can add the SDL3 Xcode project file to your project:

1. Run Xcode and create a new project using the iOS Game template, selecting the Objective C language and Metal game technology.
2. In the main view, delete all files except for Assets and LaunchScreen
3. Right click the project in the main view, select "Add Files...", and add the SDL project, Xcode/SDL/SDL.xcodeproj
4. Select the project in the main view, go to the "Info" tab and under "Custom iOS Target Properties" remove the line "Main storyboard file base name"
5. Select the project in the main view, go to the "Build Settings" tab, select "All", and edit "Header Search Path" and drag over the SDL "Public Headers" folder from the left
6. Select the project in the main view, go to the "Build Phases" tab, select "Link Binary With Libraries", and add SDL3.framework from "Framework-iOS"
7. Select the project in the main view, go to the "General" tab, scroll down to "Frameworks, Libraries, and Embedded Content", and select "Embed & Sign" for the SDL library.
8. Add the source files that you would normally have for an SDL program, making sure to have #include <SDL3/SDL_main.h> at the top of the file containing your main() function.
9. Add any assets that your application needs.
10. Enjoy!

Notes for distributing your iOS app on the AppStore when using the embedded SDL3 Xcode project: Embedding the SDL3 Xcode project makes SDL3.framework a target of your app, so it will be included in the archive created during the "Archive" step required for App Store submission. As this prevents successful distribution, remove the framework via a script in the Build Phase after the "Embed & Sign" step.

1. Select the project in the main view, go to the "Build Phases" tab, click on the big '+' in this tab and click "New Run Script Phase".
2. Scroll down to "Run Script" (after the "Embed SDL3 Framework") and enter the following script:
   if [ -d "$INSTALL_ROOT/Library" ]; then
   echo "Removing SDL3.framework from INSTALL_ROOT for archiving"
   rm -rf "$INSTALL_ROOT/Library"
   fi
3. Below the script entry uncheck the "Run Script:" options "For install builds only" and "Based on dependency analysis"

TODO: Add information regarding App Store requirements such as icons, etc.

# Notes – Retina / High-DPI and window sizes

Window and display mode sizes in SDL are in points rather than in pixels. On iOS this means that a window created on an iPhone 6 will have a size in points of 375 x 667, rather than a size in pixels of 750 x 1334. All iOS apps are expected to size their content based on points rather than pixels, as this allows different iOS devices to have different pixel densities (Retina versus non-Retina screens, etc.) without apps caring too much.

SDL_GetWindowSize() and mouse coordinates are in points rather than pixels, but the window will have a much greater pixel density when the device supports it, and the SDL_GetWindowSizeInPixels() can be called to determine the size in pixels of the drawable screen framebuffer.

The SDL 2D rendering API will automatically handle this for you, by default providing a rendering area in points, and you can call SDL_SetRenderLogicalPresentation() to gain access to the higher density resolution.

Some OpenGL ES functions such as glViewport expect sizes in pixels rather than sizes in points. When doing 2D rendering with OpenGL ES, an orthographic projection matrix using the size in points (SDL_GetWindowSize()) can be used in order to display content at the same scale no matter whether a Retina device is used or not.

# Notes – Application events

On iOS the application goes through a fixed life cycle and you will get notifications of state changes via application events. When these events are delivered you must handle them in an event callback because the OS may not give you any processing time after the events are delivered.

e.g.

    bool HandleAppEvents(void *userdata, SDL_Event *event)
    {
        switch (event->type)
        {
        case SDL_EVENT_TERMINATING:
            /* Terminate the app.
               Shut everything down before returning from this function.
            */
            return false;
        case SDL_EVENT_LOW_MEMORY:
            /* You will get this when your app is paused and iOS wants more memory.
               Release as much memory as possible.
            */
            return false;
        case SDL_EVENT_WILL_ENTER_BACKGROUND:
            /* Prepare your app to go into the background.  Stop loops, etc.
               This gets called when the user hits the home button, or gets a call.
            */
            return false;
        case SDL_EVENT_DID_ENTER_BACKGROUND:
            /* This will get called if the user accepted whatever sent your app to the background.
               If the user got a phone call and canceled it, you'll instead get an SDL_EVENT_DID_ENTER_FOREGROUND event and restart your loops.
               When you get this, you have 5 seconds to save all your state or the app will be terminated.
               Your app is NOT active at this point.
            */
            return false;
        case SDL_EVENT_WILL_ENTER_FOREGROUND:
            /* This call happens when your app is coming back to the foreground.
               Restore all your state here.
            */
            return false;
        case SDL_EVENT_DID_ENTER_FOREGROUND:
            /* Restart your loops here.
               Your app is interactive and getting CPU again.
            */
            return false;
        default:
            /* No special processing, add it to the event queue */
            return true;
        }
    }

    int main(int argc, char *argv[])
    {
        SDL_SetEventFilter(HandleAppEvents, NULL);

        ... run your main loop

        return 0;
    }

Note that if you are using main callbacks instead of a standard C main() function, your SDL_AppEvent() callback will run as these events arrive and you do not need to use SDL_SetEventFilter.

# Notes – Keyboard

The SDL keyboard API has been extended to support on-screen keyboards:

void SDL_StartTextInput() – enables text events and reveals the onscreen keyboard.

void SDL_StopTextInput() – disables text events and hides the onscreen keyboard.

bool SDL_TextInputActive() – returns whether or not text events are enabled (and the onscreen keyboard is visible)

# Notes – Mouse

iOS now supports Bluetooth mice on iPad, but by default will provide the mouse input as touch. In order for SDL to see the real mouse events, you should set the key UIApplicationSupportsIndirectInputEvents to true in your Info.plist

From iOS 17 onward, the key now defaults to true.

# Notes – Reading and Writing files

Each application installed on iPhone resides in a sandbox which includes its own application home directory. Your application may not access files outside this directory.

When your SDL based iPhone application starts up, it sets the working directory to the main bundle, where your application resources are stored. You cannot write to this directory. Instead, you should write document files to the directory returned by SDL_GetUserFolder(SDL_FOLDER_DOCUMENTS) and preferences to the directory returned by SDL_GetPrefPath().

More information on this subject is available here: http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html

# Notes – iPhone SDL limitations

Windows: Full-size, single window applications only. You cannot create multi-window SDL applications for iPhone OS. The application window will fill the display, though you have the option of turning on or off the menu-bar (pass SDL_CreateWindow() the flag SDL_WINDOW_BORDERLESS).

Textures: The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_XBGR8888, and SDL_PIXELFORMAT_RGB24 pixel formats.

# Notes – CoreBluetooth.framework

SDL_JOYSTICK_HIDAPI is disabled by default. It can give you access to a lot more game controller devices, but it requires permission from the user before your app will be able to talk to the Bluetooth hardware. "Made For iOS" branded controllers do not need this as we don't have to speak to them directly with raw bluetooth, so many apps can live without this.

You'll need to link with CoreBluetooth.framework and add something like this to your Info.plist:

<key>NSBluetoothPeripheralUsageDescription</key> <string>MyApp would like to remain connected to nearby bluetooth Game Controllers and Game Pads even when you're not using the app.</string>

# Game Center

Game Center integration might require that you break up your main loop in order to yield control back to the system. In other words, instead of running an endless main loop, you run each frame in a callback function, using:

    bool SDL_SetiOSAnimationCallback(SDL_Window * window, int interval, SDL_iOSAnimationCallback callback, void *callbackParam);

This will set up the given function to be called back on the animation callback, and then you have to return from main() to let the Cocoa event loop run.

e.g.

    extern "C"
    void ShowFrame(void*)
    {
        ... do event handling, frame logic and rendering ...
    }

    int main(int argc, char *argv[])
    {
        ... initialize game ...

    #ifdef SDL_PLATFORM_IOS
        // Initialize the Game Center for scoring and matchmaking
        InitGameCenter();

        // Set up the game to run in the window animation callback on iOS
        // so that Game Center and so forth works correctly.
        SDL_SetiOSAnimationCallback(window, 1, ShowFrame, NULL);
    #else
        while ( running ) {
            ShowFrame(0);
            DelayFrame();
        }
    #endif
        return 0;
    }

Note that if you are using main callbacks instead of a standard C main() function, your SDL_AppIterate() callback is already doing this and you don't need to use SDL_SetiOSAnimationCallback.

# Deploying to older versions of iOS

SDL supports deploying to older versions of iOS than are supported by the latest version of Xcode, all the way back to iOS 11.0

In order to do that you need to download an older version of Xcode: https://developer.apple.com/download/more/?name=Xcode

Open the package contents of the older Xcode and your newer version of Xcode and copy over the folders in Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

Then open the file Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/SDKSettings.plist and add the versions of iOS you want to deploy to the key Root/DefaultProperties/DEPLOYMENT_TARGET_SUGGESTED_VALUES

Open your project and set your deployment target to the desired version of iOS

Finally, remove GameController from the list of frameworks linked by your application and edit the build settings for "Other Linker Flags" and add -weak_framework GameController