README-ios.txt
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     1 ==============================================================================
       
     2 Building the Simple DirectMedia Layer for iPhone OS 2.0
       
     3 ==============================================================================
       
     4 
       
     5 Requirements: Mac OS X v10.5 or later and the iPhone SDK.
       
     6 
       
     7 Instructions:
       
     8 1.  Open SDL.xcodeproj (located in Xcode-iOS/SDL) in XCode.
       
     9 2.  Select your desired target, and hit build.
       
    10 
       
    11 There are three build targets:
       
    12 - libSDL.a:
       
    13 	Build SDL as a statically linked library
       
    14 - testsdl
       
    15 	Build a test program (there are known test failures which are fine)
       
    16 - Template:
       
    17 	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.
       
    18 
       
    19 ==============================================================================
       
    20 Build SDL for iOS from the command line
       
    21 ==============================================================================
       
    22 
       
    23 1. cd (PATH WHERE THE SDL CODE IS)/build-scripts
       
    24 2. ./iosbuild.sh
       
    25 
       
    26 If everything goes fine, you should see a build/ios directory, inside there's
       
    27 two directories "lib" and "include". 
       
    28 "include" contains a copy of the SDL headers that you'll need for your project,
       
    29 make sure to configure XCode to look for headers there.
       
    30 "lib" contains find two files, libSDL2.a and libSDL2main.a, you have to add both 
       
    31 to your XCode project. These libraries contain three architectures in them,
       
    32 armv6 for legacy devices, armv7, and i386 (for the simulator).
       
    33 By default, iosbuild.sh will autodetect the SDK version you have installed using 
       
    34 xcodebuild -showsdks, and build for iOS >= 3.0, you can override this behaviour 
       
    35 by setting the MIN_OS_VERSION variable, ie:
       
    36 
       
    37 MIN_OS_VERSION=4.2 ./iosbuild.sh
       
    38 
       
    39 ==============================================================================
       
    40 Using the Simple DirectMedia Layer for iOS
       
    41 ==============================================================================
       
    42 
       
    43 FIXME: This needs to be updated for the latest methods
       
    44 
       
    45 Here is the easiest method:
       
    46 1.  Build the SDL libraries (libSDL.a and libSDLSimulator.a) and the iPhone SDL Application template.
       
    47 1.  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.
       
    48 2.  Start a new project using the template.  The project should be immediately ready for use with SDL.
       
    49 
       
    50 Here is a more manual method:
       
    51 1.  Create a new iPhone view based application.
       
    52 2.  Build the SDL static libraries (libSDL.a and libSDLSimulator.a) for iPhone 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 iPhone and in the iPhone Simulator.
       
    53 3.  Include the SDL header files in your project.
       
    54 4.  Remove the ApplicationDelegate.h and ApplicationDelegate.m files -- SDL for iPhone provides its own UIApplicationDelegate.  Remove MainWindow.xib -- SDL for iPhone produces its user interface programmatically.
       
    55 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.
       
    56 
       
    57 ==============================================================================
       
    58 Notes -- Application events
       
    59 ==============================================================================
       
    60 
       
    61 On iOS the application goes through a fixed life cycle and you will get
       
    62 notifications of state changes via application events. When these events
       
    63 are delivered you must handle them in an event callback because the OS may
       
    64 not give you any processing time after the events are delivered.
       
    65 
       
    66 e.g.
       
    67 
       
    68 int HandleAppEvents(void *userdata, SDL_Event *event)
       
    69 {
       
    70     switch (event->type)
       
    71     {
       
    72     case SDL_APP_TERMINATING:
       
    73         /* Terminate the app.
       
    74            Shut everything down before returning from this function.
       
    75         */
       
    76         return 0;
       
    77     case SDL_APP_LOWMEMORY:
       
    78         /* You will get this when your app is paused and iOS wants more memory.
       
    79            Release as much memory as possible.
       
    80         */
       
    81         return 0;
       
    82     case SDL_APP_WILLENTERBACKGROUND:
       
    83         /* Prepare your app to go into the background.  Stop loops, etc.
       
    84            This gets called when the user hits the home button, or gets a call.
       
    85         */
       
    86         return 0;
       
    87     case SDL_APP_DIDENTERBACKGROUND:
       
    88         /* This will get called if the user accepted whatever sent your app to the background.
       
    89            If the user got a phone call and canceled it, you'll instead get an SDL_APP_DIDENTERFOREGROUND event and restart your loops.
       
    90            When you get this, you have 5 seconds to save all your state or the app will be terminated.
       
    91            Your app is NOT active at this point.
       
    92         */
       
    93         return 0;
       
    94     case SDL_APP_WILLENTERFOREGROUND:
       
    95         /* This call happens when your app is coming back to the foreground.
       
    96            Restore all your state here.
       
    97         */
       
    98         return 0;
       
    99     case SDL_APP_DIDENTERFOREGROUND:
       
   100         /* Restart your loops here.
       
   101            Your app is interactive and getting CPU again.
       
   102         */
       
   103         return 0;
       
   104     default:
       
   105         /* No special processing, add it to the event queue */
       
   106         return 1;
       
   107     }
       
   108 }
       
   109 
       
   110 int main(int argc, char *argv[])
       
   111 {
       
   112     SDL_SetEventFilter(HandleAppEvents, NULL);
       
   113 
       
   114     ... run your main loop
       
   115 
       
   116     return 0;
       
   117 }
       
   118 
       
   119     
       
   120 ==============================================================================
       
   121 Notes -- Accelerometer as Joystick
       
   122 ==============================================================================
       
   123 
       
   124 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.
       
   125 
       
   126 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.
       
   127 
       
   128 ==============================================================================
       
   129 Notes -- OpenGL ES
       
   130 ==============================================================================
       
   131 
       
   132 Your SDL application for iPhone uses OpenGL ES for video by default.
       
   133 
       
   134 OpenGL ES for iPhone 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.
       
   135 
       
   136 If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
       
   137 
       
   138 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 1.
       
   139 
       
   140 ==============================================================================
       
   141 Notes -- Keyboard
       
   142 ==============================================================================
       
   143 
       
   144 The SDL keyboard API has been extended to support on-screen keyboards:
       
   145 
       
   146 void SDL_StartTextInput()
       
   147 	-- enables text events and reveals the onscreen keyboard.
       
   148 void SDL_StopTextInput()
       
   149 	-- disables text events and hides the onscreen keyboard.
       
   150 SDL_bool SDL_IsTextInputActive()
       
   151 	-- returns whether or not text events are enabled (and the onscreen keyboard is visible)
       
   152 
       
   153 ==============================================================================
       
   154 Notes -- Reading and Writing files
       
   155 ==============================================================================
       
   156 
       
   157 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.
       
   158 
       
   159 Once your application is installed its directory tree looks like:
       
   160 
       
   161 MySDLApp Home/
       
   162 	MySDLApp.app
       
   163 	Documents/
       
   164 	Library/
       
   165 		Preferences/
       
   166 	tmp/
       
   167 
       
   168 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".  
       
   169 
       
   170 More information on this subject is available here:
       
   171 http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
       
   172 
       
   173 ==============================================================================
       
   174 Notes -- iPhone SDL limitations
       
   175 ==============================================================================
       
   176 
       
   177 Windows:
       
   178 	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).
       
   179 
       
   180 Textures:
       
   181 	The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
       
   182 
       
   183 Loading Shared Objects:
       
   184 	This is disabled by default since it seems to break the terms of the iPhone SDK agreement.  It can be re-enabled in SDL_config_iphoneos.h.
       
   185 
       
   186 ==============================================================================
       
   187 Game Center 
       
   188 ==============================================================================
       
   189 
       
   190 Game Center integration requires 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:
       
   191     
       
   192 int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
       
   193 
       
   194 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.
       
   195 
       
   196 e.g.
       
   197 
       
   198 extern "C"
       
   199 void ShowFrame(void*)
       
   200 {
       
   201     ... do event handling, frame logic and rendering
       
   202 }
       
   203 
       
   204 int main(int argc, char *argv[])
       
   205 {
       
   206    ... initialize game ...
       
   207 
       
   208 #if __IPHONEOS__
       
   209         // Initialize the Game Center for scoring and matchmaking
       
   210         InitGameCenter();
       
   211 
       
   212         // Set up the game to run in the window animation callback on iOS
       
   213         // so that Game Center and so forth works correctly.
       
   214         SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
       
   215 #else
       
   216         while ( running ) {
       
   217                 ShowFrame(0);
       
   218                 DelayFrame();
       
   219         }
       
   220 #endif
       
   221         return 0;
       
   222 }