README.iOS
author David Ludwig <dludwig@pobox.com>
Mon, 19 Nov 2012 22:07:06 -0500
changeset 8343 f593baeea84c
parent 8340 e470405f3ae9
permissions -rw-r--r--
Merged with local changes
     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 AppDelegate.h and AppDelegate.m files -- SDL for iPhone provides its own UIApplicationDelegate.  Remove ViewController.h, ViewController.m, and ViewController.xib -- SDL for iPhone produces its user interface programmatically.
    55 5.  Make sure your project links to the following, iOS-provided frameworks: OpenGLES.framework, AudioToolbox.framework, and QuartzCore.framework
    56 6.  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.
    57 
    58 ==============================================================================
    59 Notes -- Accelerometer as Joystick
    60 ==============================================================================
    61 
    62 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.
    63 
    64 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.
    65 
    66 ==============================================================================
    67 Notes -- OpenGL ES
    68 ==============================================================================
    69 
    70 Your SDL application for iPhone uses OpenGL ES for video by default.
    71 
    72 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.
    73 
    74 If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
    75 
    76 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.
    77 
    78 ==============================================================================
    79 Notes -- Keyboard
    80 ==============================================================================
    81 
    82 The SDL keyboard API has been extended to support on-screen keyboards:
    83 
    84 void SDL_StartTextInput()
    85 	-- enables text events and reveals the onscreen keyboard.
    86 void SDL_StopTextInput()
    87 	-- disables text events and hides the onscreen keyboard.
    88 SDL_bool SDL_IsTextInputActive()
    89 	-- returns whether or not text events are enabled (and the onscreen keyboard is visible)
    90 
    91 ==============================================================================
    92 Notes -- Reading and Writing files
    93 ==============================================================================
    94 
    95 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.
    96 
    97 Once your application is installed its directory tree looks like:
    98 
    99 MySDLApp Home/
   100 	MySDLApp.app
   101 	Documents/
   102 	Library/
   103 		Preferences/
   104 	tmp/
   105 
   106 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".  
   107 
   108 More information on this subject is available here:
   109 http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
   110 
   111 ==============================================================================
   112 Notes -- iPhone SDL limitations
   113 ==============================================================================
   114 
   115 Windows:
   116 	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).
   117 
   118 Textures:
   119 	The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
   120 
   121 Loading Shared Objects:
   122 	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.
   123 
   124 ==============================================================================
   125 Game Center 
   126 ==============================================================================
   127 
   128 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:
   129     
   130 int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
   131 
   132 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.
   133 
   134 e.g.
   135 
   136 extern "C"
   137 void ShowFrame(void*)
   138 {
   139     ... do event handling, frame logic and rendering
   140 }
   141 
   142 int main(int argc, char *argv[])
   143 {
   144    ... initialize game ...
   145 
   146 #if __IPHONEOS__
   147         // Initialize the Game Center for scoring and matchmaking
   148         InitGameCenter();
   149 
   150         // Set up the game to run in the window animation callback on iOS
   151         // so that Game Center and so forth works correctly.
   152         SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
   153 #else
   154         while ( running ) {
   155                 ShowFrame(0);
   156                 DelayFrame();
   157         }
   158 #endif
   159         return 0;
   160 }