SDL  2.0
README-ios.md
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1 iOS
2 ======
3 
4 Building the Simple DirectMedia Layer for iOS 5.1+
5 ==============================================================================
6 
7 Requirements: Mac OS X 10.8 or later and the iOS 7+ SDK.
8 
9 Instructions:
10 
11 1. Open SDL.xcodeproj (located in Xcode/SDL) in Xcode.
12 2. Select your desired target, and hit build.
13 
14 There are three build targets:
15 - libSDL.a:
16  Build SDL as a statically linked library
17 - testsdl:
18  Build a test program (there are known test failures which are fine)
19 - Template:
20  Package a project template together with the SDL for iPhone static libraries and copies of the SDL headers. The template includes proper references to the SDL library and headers, skeleton code for a basic SDL program, and placeholder graphics for the application icon and startup screen.
21 
22 
23 Build SDL for iOS from the command line
24 ==============================================================================
25 
26 1. cd (PATH WHERE THE SDL CODE IS)/build-scripts
27 2. ./iosbuild.sh
28 
29 If everything goes fine, you should see a build/ios directory, inside there's
30 two directories "lib" and "include".
31 "include" contains a copy of the SDL headers that you'll need for your project,
32 make sure to configure XCode to look for headers there.
33 "lib" contains find two files, libSDL2.a and libSDL2main.a, you have to add both
34 to your XCode project. These libraries contain three architectures in them,
35 armv6 for legacy devices, armv7, and i386 (for the simulator).
36 By default, iosbuild.sh will autodetect the SDK version you have installed using
37 xcodebuild -showsdks, and build for iOS >= 3.0, you can override this behaviour
38 by setting the MIN_OS_VERSION variable, ie:
39 
40 MIN_OS_VERSION=4.2 ./iosbuild.sh
41 
42 Using the Simple DirectMedia Layer for iOS
43 ==============================================================================
44 
45 FIXME: This needs to be updated for the latest methods
46 
47 Here is the easiest method:
48 1. Build the SDL library (libSDL2.a) and the iPhone SDL Application template.
49 2. Install the iPhone SDL Application template by copying it to one of Xcode's template directories. I recommend creating a directory called "SDL" in "/Developer/Platforms/iOS.platform/Developer/Library/Xcode/Project Templates/" and placing it there.
50 3. Start a new project using the template. The project should be immediately ready for use with SDL.
51 
52 Here is a more manual method:
53 1. Create a new iOS view based application.
54 2. Build the SDL static library (libSDL2.a) for iOS and include them in your project. Xcode will ignore the library that is not currently of the correct architecture, hence your app will work both on iOS and in the iOS Simulator.
55 3. Include the SDL header files in your project.
56 4. Remove the ApplicationDelegate.h and ApplicationDelegate.m files -- SDL for iOS provides its own UIApplicationDelegate. Remove MainWindow.xib -- SDL for iOS produces its user interface programmatically.
57 5. Delete the contents of main.m and program your app as a regular SDL program instead. You may replace main.m with your own main.c, but you must tell Xcode not to use the project prefix file, as it includes Objective-C code.
58 
59 
60 Notes -- Retina / High-DPI and window sizes
61 ==============================================================================
62 
63 Window and display mode sizes in SDL are in "screen coordinates" (or "points",
64 in Apple's terminology) rather than in pixels. On iOS this means that a window
65 created on an iPhone 6 will have a size in screen coordinates of 375 x 667,
66 rather than a size in pixels of 750 x 1334. All iOS apps are expected to
67 size their content based on screen coordinates / points rather than pixels,
68 as this allows different iOS devices to have different pixel densities
69 (Retina versus non-Retina screens, etc.) without apps caring too much.
70 
71 By default SDL will not use the full pixel density of the screen on
72 Retina/high-dpi capable devices. Use the SDL_WINDOW_ALLOW_HIGHDPI flag when
73 creating your window to enable high-dpi support.
74 
75 When high-dpi support is enabled, SDL_GetWindowSize() and display mode sizes
76 will still be in "screen coordinates" rather than pixels, but the window will
77 have a much greater pixel density when the device supports it, and the
78 SDL_GL_GetDrawableSize() or SDL_GetRendererOutputSize() functions (depending on
79 whether raw OpenGL or the SDL_Render API is used) can be queried to determine
80 the size in pixels of the drawable screen framebuffer.
81 
82 Some OpenGL ES functions such as glViewport expect sizes in pixels rather than
83 sizes in screen coordinates. When doing 2D rendering with OpenGL ES, an
84 orthographic projection matrix using the size in screen coordinates
85 (SDL_GetWindowSize()) can be used in order to display content at the same scale
86 no matter whether a Retina device is used or not.
87 
88 
89 Notes -- Application events
90 ==============================================================================
91 
92 On iOS the application goes through a fixed life cycle and you will get
93 notifications of state changes via application events. When these events
94 are delivered you must handle them in an event callback because the OS may
95 not give you any processing time after the events are delivered.
96 
97 e.g.
98 
99  int HandleAppEvents(void *userdata, SDL_Event *event)
100  {
101  switch (event->type)
102  {
103  case SDL_APP_TERMINATING:
104  /* Terminate the app.
105  Shut everything down before returning from this function.
106  */
107  return 0;
108  case SDL_APP_LOWMEMORY:
109  /* You will get this when your app is paused and iOS wants more memory.
110  Release as much memory as possible.
111  */
112  return 0;
113  case SDL_APP_WILLENTERBACKGROUND:
114  /* Prepare your app to go into the background. Stop loops, etc.
115  This gets called when the user hits the home button, or gets a call.
116  */
117  return 0;
118  case SDL_APP_DIDENTERBACKGROUND:
119  /* This will get called if the user accepted whatever sent your app to the background.
120  If the user got a phone call and canceled it, you'll instead get an SDL_APP_DIDENTERFOREGROUND event and restart your loops.
121  When you get this, you have 5 seconds to save all your state or the app will be terminated.
122  Your app is NOT active at this point.
123  */
124  return 0;
125  case SDL_APP_WILLENTERFOREGROUND:
126  /* This call happens when your app is coming back to the foreground.
127  Restore all your state here.
128  */
129  return 0;
130  case SDL_APP_DIDENTERFOREGROUND:
131  /* Restart your loops here.
132  Your app is interactive and getting CPU again.
133  */
134  return 0;
135  default:
136  /* No special processing, add it to the event queue */
137  return 1;
138  }
139  }
140 
141  int main(int argc, char *argv[])
142  {
143  SDL_SetEventFilter(HandleAppEvents, NULL);
144 
145  ... run your main loop
146 
147  return 0;
148  }
149 
150 
151 Notes -- Accelerometer as Joystick
152 ==============================================================================
153 
154 SDL 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.
155 
156 The 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.
157 
158 
159 Notes -- OpenGL ES
160 ==============================================================================
161 
162 Your SDL application for iOS uses OpenGL ES for video by default.
163 
164 OpenGL 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().
165 
166 If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
167 
168 Finally, 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.
169 
170 OpenGL ES on iOS doesn't use the traditional system-framebuffer setup provided in other operating systems. Special care must be taken because of this:
171 
172 - The drawable Renderbuffer must be bound to the GL_RENDERBUFFER binding point when SDL_GL_SwapWindow() is called.
173 - The drawable Framebuffer Object must be bound while rendering to the screen and when SDL_GL_SwapWindow() is called.
174 - 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.
175 
176 The above objects can be obtained via SDL_GetWindowWMInfo() (in SDL_syswm.h).
177 
178 
179 Notes -- Keyboard
180 ==============================================================================
181 
182 The SDL keyboard API has been extended to support on-screen keyboards:
183 
184 void SDL_StartTextInput()
185  -- enables text events and reveals the onscreen keyboard.
186 
187 void SDL_StopTextInput()
188  -- disables text events and hides the onscreen keyboard.
189 
190 SDL_bool SDL_IsTextInputActive()
191  -- returns whether or not text events are enabled (and the onscreen keyboard is visible)
192 
193 
194 Notes -- Reading and Writing files
195 ==============================================================================
196 
197 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.
198 
199 Once your application is installed its directory tree looks like:
200 
201  MySDLApp Home/
202  MySDLApp.app
203  Documents/
204  Library/
205  Preferences/
206  tmp/
207 
208 When 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".
209 
210 More information on this subject is available here:
211 http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
212 
213 
214 Notes -- iPhone SDL limitations
215 ==============================================================================
216 
217 Windows:
218  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).
219 
220 Textures:
221  The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
222 
223 Loading Shared Objects:
224  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.
225 
226 
227 Notes -- CoreBluetooth.framework
228 ==============================================================================
229 
230 SDL_JOYSTICK_HIDAPI is disabled by default. It can give you access to a lot
231 more game controller devices, but it requires permission from the user before
232 your app will be able to talk to the Bluetooth hardware. "Made For iOS"
233 branded controllers do not need this as we don't have to speak to them
234 directly with raw bluetooth, so many apps can live without this.
235 
236 You'll need to link with CoreBluetooth.framework and add something like this
237 to your Info.plist:
238 
239 <key>NSBluetoothPeripheralUsageDescription</key>
240 <string>MyApp would like to remain connected to nearby bluetooth Game Controllers and Game Pads even when you're not using the app.</string>
241 
242 
243 Game Center
244 ==============================================================================
245 
246 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:
247 
248  int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
249 
250 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.
251 
252 e.g.
253 
254  extern "C"
255  void ShowFrame(void*)
256  {
257  ... do event handling, frame logic and rendering ...
258  }
259 
260  int main(int argc, char *argv[])
261  {
262  ... initialize game ...
263 
264  #if __IPHONEOS__
265  // Initialize the Game Center for scoring and matchmaking
266  InitGameCenter();
267 
268  // Set up the game to run in the window animation callback on iOS
269  // so that Game Center and so forth works correctly.
270  SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
271  #else
272  while ( running ) {
273  ShowFrame(0);
274  DelayFrame();
275  }
276  #endif
277  return 0;
278  }
279 
280 
281 Deploying to older versions of iOS
282 ==============================================================================
283 
284 SDL supports deploying to older versions of iOS than are supported by the latest version of Xcode, all the way back to iOS 6.1
285 
286 In order to do that you need to download an older version of Xcode:
287 https://developer.apple.com/download/more/?name=Xcode
288 
289 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
290 
291 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
292 
293 Open your project and set your deployment target to the desired version of iOS
294 
295 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