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1iOS
2======
3
4Building the Simple DirectMedia Layer for iOS 9.0+
5==============================================================================
6
7Requirements: Mac OS X 10.9 or later and the iOS 9.0 or newer SDK.
8
9Instructions:
10
111. Open SDL.xcodeproj (located in Xcode/SDL) in Xcode.
122. Select your desired target, and hit build.
13
14
15Using the Simple DirectMedia Layer for iOS
16==============================================================================
17
181. Run Xcode and create a new project using the iOS Game template, selecting the Objective C language and Metal game technology.
192. In the main view, delete all files except for Assets and LaunchScreen
203. Right click the project in the main view, select "Add Files...", and add the SDL project, Xcode/SDL/SDL.xcodeproj
214. 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"
225. 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
236. Select the project in the main view, go to the "Build Phases" tab, select "Link Binary With Libraries", and add SDL2.framework from "Framework-iOS"
247. 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.
258. In the main view, expand SDL -> Library Source -> main -> uikit and drag SDL_uikit_main.c into your game files
269. Add the source files that you would normally have for an SDL program, making sure to have #include "SDL.h" at the top of the file containing your main() function.
2710. Add any assets that your application needs.
2811. Enjoy!
29
30
31TODO: Add information regarding App Store requirements such as icons, etc.
32
33
34Notes -- Retina / High-DPI and window sizes
35==============================================================================
36
37Window and display mode sizes in SDL are in "screen coordinates" (or "points",
38in Apple's terminology) rather than in pixels. On iOS this means that a window
39created on an iPhone 6 will have a size in screen coordinates of 375 x 667,
40rather than a size in pixels of 750 x 1334. All iOS apps are expected to
41size their content based on screen coordinates / points rather than pixels,
42as this allows different iOS devices to have different pixel densities
43(Retina versus non-Retina screens, etc.) without apps caring too much.
44
45By default SDL will not use the full pixel density of the screen on
46Retina/high-dpi capable devices. Use the SDL_WINDOW_ALLOW_HIGHDPI flag when
47creating your window to enable high-dpi support.
48
49When high-dpi support is enabled, SDL_GetWindowSize() and display mode sizes
50will still be in "screen coordinates" rather than pixels, but the window will
51have a much greater pixel density when the device supports it, and the
52SDL_GL_GetDrawableSize() or SDL_GetRendererOutputSize() functions (depending on
53whether raw OpenGL or the SDL_Render API is used) can be queried to determine
54the size in pixels of the drawable screen framebuffer.
55
56Some OpenGL ES functions such as glViewport expect sizes in pixels rather than
57sizes in screen coordinates. When doing 2D rendering with OpenGL ES, an
58orthographic projection matrix using the size in screen coordinates
59(SDL_GetWindowSize()) can be used in order to display content at the same scale
60no matter whether a Retina device is used or not.
61
62
63Notes -- Application events
64==============================================================================
65
66On iOS the application goes through a fixed life cycle and you will get
67notifications of state changes via application events. When these events
68are delivered you must handle them in an event callback because the OS may
69not give you any processing time after the events are delivered.
70
71e.g.
72
73 int HandleAppEvents(void *userdata, SDL_Event *event)
74 {
75 switch (event->type)
76 {
77 case SDL_APP_TERMINATING:
78 /* Terminate the app.
79 Shut everything down before returning from this function.
80 */
81 return 0;
82 case SDL_APP_LOWMEMORY:
83 /* You will get this when your app is paused and iOS wants more memory.
84 Release as much memory as possible.
85 */
86 return 0;
87 case SDL_APP_WILLENTERBACKGROUND:
88 /* Prepare your app to go into the background. Stop loops, etc.
89 This gets called when the user hits the home button, or gets a call.
90 */
91 return 0;
92 case SDL_APP_DIDENTERBACKGROUND:
93 /* This will get called if the user accepted whatever sent your app to the background.
94 If the user got a phone call and canceled it, you'll instead get an SDL_APP_DIDENTERFOREGROUND event and restart your loops.
95 When you get this, you have 5 seconds to save all your state or the app will be terminated.
96 Your app is NOT active at this point.
97 */
98 return 0;
99 case SDL_APP_WILLENTERFOREGROUND:
100 /* This call happens when your app is coming back to the foreground.
101 Restore all your state here.
102 */
103 return 0;
104 case SDL_APP_DIDENTERFOREGROUND:
105 /* Restart your loops here.
106 Your app is interactive and getting CPU again.
107 */
108 return 0;
109 default:
110 /* No special processing, add it to the event queue */
111 return 1;
112 }
113 }
114
115 int main(int argc, char *argv[])
116 {
117 SDL_SetEventFilter(HandleAppEvents, NULL);
118
119 ... run your main loop
120
121 return 0;
122 }
123
124
125Notes -- Accelerometer as Joystick
126==============================================================================
127
128SDL for iPhone supports polling the built in accelerometer as a joystick device. For an example on how to do this, see the accelerometer.c in the demos directory.
129
130The main thing to note when using the accelerometer with SDL is that while the iPhone natively reports accelerometer as floating point values in units of g-force, SDL_JoystickGetAxis() reports joystick values as signed integers. Hence, in order to convert between the two, some clamping and scaling is necessary on the part of the iPhone SDL joystick driver. To convert SDL_JoystickGetAxis() reported values BACK to units of g-force, simply multiply the values by SDL_IPHONE_MAX_GFORCE / 0x7FFF.
131
132
133Notes -- OpenGL ES
134==============================================================================
135
136Your SDL application for iOS uses OpenGL ES for video by default.
137
138OpenGL ES for iOS supports several display pixel formats, such as RGBA8 and RGB565, which provide a 32 bit and 16 bit color buffer respectively. By default, the implementation uses RGB565, but you may use RGBA8 by setting each color component to 8 bits in SDL_GL_SetAttribute().
139
140If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
141
142Finally, if your application completely redraws the screen each frame, you may find significant performance improvement by setting the attribute SDL_GL_RETAINED_BACKING to 0.
143
144OpenGL ES on iOS doesn't use the traditional system-framebuffer setup provided in other operating systems. Special care must be taken because of this:
145
146- The drawable Renderbuffer must be bound to the GL_RENDERBUFFER binding point when SDL_GL_SwapWindow() is called.
147- The drawable Framebuffer Object must be bound while rendering to the screen and when SDL_GL_SwapWindow() is called.
148- If multisample antialiasing (MSAA) is used and glReadPixels is used on the screen, the drawable framebuffer must be resolved to the MSAA resolve framebuffer (via glBlitFramebuffer or glResolveMultisampleFramebufferAPPLE), and the MSAA resolve framebuffer must be bound to the GL_READ_FRAMEBUFFER binding point, before glReadPixels is called.
149
150The above objects can be obtained via SDL_GetWindowWMInfo() (in SDL_syswm.h).
151
152
153Notes -- Keyboard
154==============================================================================
155
156The SDL keyboard API has been extended to support on-screen keyboards:
157
158void SDL_StartTextInput()
159 -- enables text events and reveals the onscreen keyboard.
160
161void SDL_StopTextInput()
162 -- disables text events and hides the onscreen keyboard.
163
164SDL_bool SDL_IsTextInputActive()
165 -- returns whether or not text events are enabled (and the onscreen keyboard is visible)
166
167
168Notes -- Mouse
169==============================================================================
170
171iOS 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
172
173
174Notes -- Reading and Writing files
175==============================================================================
176
177Each application installed on iPhone resides in a sandbox which includes its own Application Home directory. Your application may not access files outside this directory.
178
179Once your application is installed its directory tree looks like:
180
181 MySDLApp Home/
182 MySDLApp.app
183 Documents/
184 Library/
185 Preferences/
186 tmp/
187
188When your SDL based iPhone application starts up, it sets the working directory to the main bundle (MySDLApp Home/MySDLApp.app), where your application resources are stored. You cannot write to this directory. Instead, I advise you to write document files to "../Documents/" and preferences to "../Library/Preferences".
189
190More information on this subject is available here:
191http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
192
193
194Notes -- xcFramework
195==============================================================================
196
197The SDL.xcodeproj file now includes a target to build SDL2.xcframework. An xcframework is a new (Xcode 11) uber-framework which can handle any combination of processor type and target OS platform.
198
199In 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.
200
201The xcframework target builds into a Products directory alongside the SDL.xcodeproj file, as SDL2.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.
202
203This target requires Xcode 11 or later. The target will simply fail to build if attempted on older Xcodes.
204
205In addition, on Apple platforms, main() cannot be in a dynamically loaded library. This means that iOS apps which used the statically-linked libSDL2.lib and now link with the xcframwork will need to define their own main() to call SDL_UIKitRunApp(), like this:
206
207#ifndef SDL_MAIN_HANDLED
208#ifdef main
209#undef main
210#endif
211
212int
213main(int argc, char *argv[])
214{
215 return SDL_UIKitRunApp(argc, argv, SDL_main);
216}
217#endif /* !SDL_MAIN_HANDLED */
218
219Using 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:
220
221#include "SDL_main.h"
222#include <SDL.h>
223#include <SDL_main.h>
224
225
226Notes -- iPhone SDL limitations
227==============================================================================
228
229Windows:
230 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).
231
232Textures:
233 The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
234
235Loading Shared Objects:
236 This is disabled by default since it seems to break the terms of the iOS SDK agreement for iOS versions prior to iOS 8. It can be re-enabled in SDL_config_iphoneos.h.
237
238
239Notes -- CoreBluetooth.framework
240==============================================================================
241
242SDL_JOYSTICK_HIDAPI is disabled by default. It can give you access to a lot
243more game controller devices, but it requires permission from the user before
244your app will be able to talk to the Bluetooth hardware. "Made For iOS"
245branded controllers do not need this as we don't have to speak to them
246directly with raw bluetooth, so many apps can live without this.
247
248You'll need to link with CoreBluetooth.framework and add something like this
249to your Info.plist:
250
251<key>NSBluetoothPeripheralUsageDescription</key>
252<string>MyApp would like to remain connected to nearby bluetooth Game Controllers and Game Pads even when you're not using the app.</string>
253
254
255Game Center
256==============================================================================
257
258Game 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:
259
260 int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
261
262This 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.
263
264e.g.
265
266 extern "C"
267 void ShowFrame(void*)
268 {
269 ... do event handling, frame logic and rendering ...
270 }
271
272 int main(int argc, char *argv[])
273 {
274 ... initialize game ...
275
276 #ifdef __IPHONEOS__
277 // Initialize the Game Center for scoring and matchmaking
278 InitGameCenter();
279
280 // Set up the game to run in the window animation callback on iOS
281 // so that Game Center and so forth works correctly.
282 SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
283 #else
284 while ( running ) {
285 ShowFrame(0);
286 DelayFrame();
287 }
288 #endif
289 return 0;
290 }
291
292
293Deploying to older versions of iOS
294==============================================================================
295
296SDL supports deploying to older versions of iOS than are supported by the latest version of Xcode, all the way back to iOS 8.0
297
298In order to do that you need to download an older version of Xcode:
299https://developer.apple.com/download/more/?name=Xcode
300
301Open 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
302
303Then 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
304
305Open your project and set your deployment target to the desired version of iOS
306
307Finally, 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
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