docs/README-ios.md
author Sam Lantinga <slouken@libsdl.org>
Fri, 22 Sep 2017 11:13:34 -0700
changeset 11522 2b3a78025695
parent 11400 9eefdf672499
child 11548 973151a33ec5
permissions -rw-r--r--
Added instructions for deploying to older iOS devices (thanks Sylvain!)
     1 iOS
     2 ======
     3 
     4 ==============================================================================
     5 Building the Simple DirectMedia Layer for iOS 5.1+
     6 ==============================================================================
     7 
     8 Requirements: Mac OS X 10.8 or later and the iOS 7+ SDK.
     9 
    10 Instructions:
    11 
    12 2.  Open SDL.xcodeproj (located in Xcode-iOS/SDL) in Xcode.
    13 4.  Select your desired target, and hit build.
    14 
    15 There are three build targets:
    16 - libSDL.a:
    17 	Build SDL as a statically linked library
    18 - testsdl:
    19 	Build a test program (there are known test failures which are fine)
    20 - Template:
    21 	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.
    22 
    23 
    24 ==============================================================================
    25 Build SDL for iOS from the command line
    26 ==============================================================================
    27 
    28 1. Follow step 1 above.
    29 2. cd (PATH WHERE THE SDL CODE IS)/build-scripts
    30 3. ./iosbuild.sh
    31 
    32 If everything goes fine, you should see a build/ios directory, inside there's
    33 two directories "lib" and "include". 
    34 "include" contains a copy of the SDL headers that you'll need for your project,
    35 make sure to configure XCode to look for headers there.
    36 "lib" contains find two files, libSDL2.a and libSDL2main.a, you have to add both 
    37 to your XCode project. These libraries contain three architectures in them,
    38 armv6 for legacy devices, armv7, and i386 (for the simulator).
    39 By default, iosbuild.sh will autodetect the SDK version you have installed using 
    40 xcodebuild -showsdks, and build for iOS >= 3.0, you can override this behaviour 
    41 by setting the MIN_OS_VERSION variable, ie:
    42 
    43 MIN_OS_VERSION=4.2 ./iosbuild.sh
    44 
    45 ==============================================================================
    46 Using the Simple DirectMedia Layer for iOS
    47 ==============================================================================
    48 
    49 FIXME: This needs to be updated for the latest methods
    50 
    51 Here is the easiest method:
    52 1.  Build the SDL library (libSDL2.a) and the iPhone SDL Application template.
    53 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.
    54 3.  Start a new project using the template.  The project should be immediately ready for use with SDL.
    55 
    56 Here is a more manual method:
    57 1.  Create a new iOS view based application.
    58 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.
    59 3.  Include the SDL header files in your project.
    60 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.
    61 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.
    62 
    63 ==============================================================================
    64 Notes -- Retina / High-DPI and window sizes
    65 ==============================================================================
    66 
    67 Window and display mode sizes in SDL are in "screen coordinates" (or "points",
    68 in Apple's terminology) rather than in pixels. On iOS this means that a window
    69 created on an iPhone 6 will have a size in screen coordinates of 375 x 667,
    70 rather than a size in pixels of 750 x 1334. All iOS apps are expected to
    71 size their content based on screen coordinates / points rather than pixels,
    72 as this allows different iOS devices to have different pixel densities
    73 (Retina versus non-Retina screens, etc.) without apps caring too much.
    74 
    75 By default SDL will not use the full pixel density of the screen on
    76 Retina/high-dpi capable devices. Use the SDL_WINDOW_ALLOW_HIGHDPI flag when
    77 creating your window to enable high-dpi support.
    78 
    79 When high-dpi support is enabled, SDL_GetWindowSize() and display mode sizes
    80 will still be in "screen coordinates" rather than pixels, but the window will
    81 have a much greater pixel density when the device supports it, and the
    82 SDL_GL_GetDrawableSize() or SDL_GetRendererOutputSize() functions (depending on
    83 whether raw OpenGL or the SDL_Render API is used) can be queried to determine
    84 the size in pixels of the drawable screen framebuffer.
    85 
    86 Some OpenGL ES functions such as glViewport expect sizes in pixels rather than
    87 sizes in screen coordinates. When doing 2D rendering with OpenGL ES, an
    88 orthographic projection matrix using the size in screen coordinates
    89 (SDL_GetWindowSize()) can be used in order to display content at the same scale
    90 no matter whether a Retina device is used or not.
    91 
    92 ==============================================================================
    93 Notes -- Application events
    94 ==============================================================================
    95 
    96 On iOS the application goes through a fixed life cycle and you will get
    97 notifications of state changes via application events. When these events
    98 are delivered you must handle them in an event callback because the OS may
    99 not give you any processing time after the events are delivered.
   100 
   101 e.g.
   102 
   103     int HandleAppEvents(void *userdata, SDL_Event *event)
   104     {
   105         switch (event->type)
   106         {
   107         case SDL_APP_TERMINATING:
   108             /* Terminate the app.
   109                Shut everything down before returning from this function.
   110             */
   111             return 0;
   112         case SDL_APP_LOWMEMORY:
   113             /* You will get this when your app is paused and iOS wants more memory.
   114                Release as much memory as possible.
   115             */
   116             return 0;
   117         case SDL_APP_WILLENTERBACKGROUND:
   118             /* Prepare your app to go into the background.  Stop loops, etc.
   119                This gets called when the user hits the home button, or gets a call.
   120             */
   121             return 0;
   122         case SDL_APP_DIDENTERBACKGROUND:
   123             /* This will get called if the user accepted whatever sent your app to the background.
   124                If the user got a phone call and canceled it, you'll instead get an SDL_APP_DIDENTERFOREGROUND event and restart your loops.
   125                When you get this, you have 5 seconds to save all your state or the app will be terminated.
   126                Your app is NOT active at this point.
   127             */
   128             return 0;
   129         case SDL_APP_WILLENTERFOREGROUND:
   130             /* This call happens when your app is coming back to the foreground.
   131                Restore all your state here.
   132             */
   133             return 0;
   134         case SDL_APP_DIDENTERFOREGROUND:
   135             /* Restart your loops here.
   136                Your app is interactive and getting CPU again.
   137             */
   138             return 0;
   139         default:
   140             /* No special processing, add it to the event queue */
   141             return 1;
   142         }
   143     }
   144     
   145     int main(int argc, char *argv[])
   146     {
   147         SDL_SetEventFilter(HandleAppEvents, NULL);
   148     
   149         ... run your main loop
   150     
   151         return 0;
   152     }
   153 
   154     
   155 ==============================================================================
   156 Notes -- Accelerometer as Joystick
   157 ==============================================================================
   158 
   159 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.
   160 
   161 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.
   162 
   163 ==============================================================================
   164 Notes -- OpenGL ES
   165 ==============================================================================
   166 
   167 Your SDL application for iOS uses OpenGL ES for video by default.
   168 
   169 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().
   170 
   171 If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
   172 
   173 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.
   174 
   175 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:
   176 
   177 - The drawable Renderbuffer must be bound to the GL_RENDERBUFFER binding point when SDL_GL_SwapWindow() is called.
   178 - The drawable Framebuffer Object must be bound while rendering to the screen and when SDL_GL_SwapWindow() is called.
   179 - 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.
   180 
   181 The above objects can be obtained via SDL_GetWindowWMInfo() (in SDL_syswm.h).
   182 
   183 ==============================================================================
   184 Notes -- Keyboard
   185 ==============================================================================
   186 
   187 The SDL keyboard API has been extended to support on-screen keyboards:
   188 
   189 void SDL_StartTextInput()
   190 	-- enables text events and reveals the onscreen keyboard.
   191 
   192 void SDL_StopTextInput()
   193 	-- disables text events and hides the onscreen keyboard.
   194 
   195 SDL_bool SDL_IsTextInputActive()
   196 	-- returns whether or not text events are enabled (and the onscreen keyboard is visible)
   197 
   198 
   199 ==============================================================================
   200 Notes -- Reading and Writing files
   201 ==============================================================================
   202 
   203 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.
   204 
   205 Once your application is installed its directory tree looks like:
   206 
   207     MySDLApp Home/
   208         MySDLApp.app
   209         Documents/
   210         Library/
   211             Preferences/
   212         tmp/
   213 
   214 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".  
   215 
   216 More information on this subject is available here:
   217 http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
   218 
   219 ==============================================================================
   220 Notes -- iPhone SDL limitations
   221 ==============================================================================
   222 
   223 Windows:
   224 	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).
   225 
   226 Textures:
   227 	The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
   228 
   229 Loading Shared Objects:
   230 	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.
   231 
   232 ==============================================================================
   233 Game Center 
   234 ==============================================================================
   235 
   236 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:
   237 
   238     int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
   239 
   240 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.
   241 
   242 e.g.
   243 
   244     extern "C"
   245     void ShowFrame(void*)
   246     {
   247         ... do event handling, frame logic and rendering ...
   248     }
   249     
   250     int main(int argc, char *argv[])
   251     {
   252         ... initialize game ...
   253     
   254     #if __IPHONEOS__
   255         // Initialize the Game Center for scoring and matchmaking
   256         InitGameCenter();
   257     
   258         // Set up the game to run in the window animation callback on iOS
   259         // so that Game Center and so forth works correctly.
   260         SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
   261     #else
   262         while ( running ) {
   263             ShowFrame(0);
   264             DelayFrame();
   265         }
   266     #endif
   267         return 0;
   268     }
   269 
   270 ==============================================================================
   271 Deploying to older versions of iOS
   272 ==============================================================================
   273 
   274 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
   275 
   276 In order to do that you need to download an older version of Xcode:
   277 https://developer.apple.com/download/more/?name=Xcode
   278 
   279 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
   280 
   281 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
   282 
   283 Open your project and set your deployment target to the desired version of iOS
   284 
   285 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