docs/README-ios.md
author bschaefer
Sun, 21 Feb 2016 15:19:35 -0800
changeset 10089 25fda20d0173
parent 9997 e330f785a5e7
child 10167 d3db276c1fa6
permissions -rw-r--r--
Fix API/ABI breakage in Mir 0.13/0.14.
     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 1.  Open SDL.xcodeproj (located in Xcode-iOS/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 ==============================================================================
    24 Build SDL for iOS from the command line
    25 ==============================================================================
    26 
    27 1. cd (PATH WHERE THE SDL CODE IS)/build-scripts
    28 2. ./iosbuild.sh
    29 
    30 If everything goes fine, you should see a build/ios directory, inside there's
    31 two directories "lib" and "include". 
    32 "include" contains a copy of the SDL headers that you'll need for your project,
    33 make sure to configure XCode to look for headers there.
    34 "lib" contains find two files, libSDL2.a and libSDL2main.a, you have to add both 
    35 to your XCode project. These libraries contain three architectures in them,
    36 armv6 for legacy devices, armv7, and i386 (for the simulator).
    37 By default, iosbuild.sh will autodetect the SDK version you have installed using 
    38 xcodebuild -showsdks, and build for iOS >= 3.0, you can override this behaviour 
    39 by setting the MIN_OS_VERSION variable, ie:
    40 
    41 MIN_OS_VERSION=4.2 ./iosbuild.sh
    42 
    43 ==============================================================================
    44 Using the Simple DirectMedia Layer for iOS
    45 ==============================================================================
    46 
    47 FIXME: This needs to be updated for the latest methods
    48 
    49 Here is the easiest method:
    50 1.  Build the SDL library (libSDL2.a) and the iPhone SDL Application template.
    51 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.
    52 3.  Start a new project using the template.  The project should be immediately ready for use with SDL.
    53 
    54 Here is a more manual method:
    55 1.  Create a new iOS view based application.
    56 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.
    57 3.  Include the SDL header files in your project.
    58 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.
    59 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.
    60 
    61 ==============================================================================
    62 Notes -- Retina / High-DPI and window sizes
    63 ==============================================================================
    64 
    65 Window and display mode sizes in SDL are in "screen coordinates" (or "points",
    66 in Apple's terminology) rather than in pixels. On iOS this means that a window
    67 created on an iPhone 6 will have a size in screen coordinates of 375 x 667,
    68 rather than a size in pixels of 750 x 1334. All iOS apps are expected to
    69 size their content based on screen coordinates / points rather than pixels,
    70 as this allows different iOS devices to have different pixel densities
    71 (Retina versus non-Retina screens, etc.) without apps caring too much.
    72 
    73 By default SDL will not use the full pixel density of the screen on
    74 Retina/high-dpi capable devices. Use the SDL_WINDOW_ALLOW_HIGHDPI flag when
    75 creating your window to enable high-dpi support.
    76 
    77 When high-dpi support is enabled, SDL_GetWindowSize and display mode sizes
    78 will still be in "screen coordinates" rather than pixels, but the window will
    79 have a much greater pixel density when the device supports it, and the
    80 SDL_GL_GetDrawableSize or SDL_GetRendererOutputSize functions (depending on
    81 whether raw OpenGL or the SDL_Render API is used) can be queried to determine
    82 the size in pixels of the drawable screen framebuffer.
    83 
    84 Some OpenGL ES functions such as glViewport expect sizes in pixels rather than
    85 sizes in screen coordinates. When doing 2D rendering with OpenGL ES, an
    86 orthographic projection matrix using the size in screen coordinates
    87 (SDL_GetWindowSize) can be used in order to display content at the same scale
    88 no matter whether a Retina device is used or not.
    89 
    90 ==============================================================================
    91 Notes -- Application events
    92 ==============================================================================
    93 
    94 On iOS the application goes through a fixed life cycle and you will get
    95 notifications of state changes via application events. When these events
    96 are delivered you must handle them in an event callback because the OS may
    97 not give you any processing time after the events are delivered.
    98 
    99 e.g.
   100 
   101     int HandleAppEvents(void *userdata, SDL_Event *event)
   102     {
   103         switch (event->type)
   104         {
   105         case SDL_APP_TERMINATING:
   106             /* Terminate the app.
   107                Shut everything down before returning from this function.
   108             */
   109             return 0;
   110         case SDL_APP_LOWMEMORY:
   111             /* You will get this when your app is paused and iOS wants more memory.
   112                Release as much memory as possible.
   113             */
   114             return 0;
   115         case SDL_APP_WILLENTERBACKGROUND:
   116             /* Prepare your app to go into the background.  Stop loops, etc.
   117                This gets called when the user hits the home button, or gets a call.
   118             */
   119             return 0;
   120         case SDL_APP_DIDENTERBACKGROUND:
   121             /* This will get called if the user accepted whatever sent your app to the background.
   122                If the user got a phone call and canceled it, you'll instead get an SDL_APP_DIDENTERFOREGROUND event and restart your loops.
   123                When you get this, you have 5 seconds to save all your state or the app will be terminated.
   124                Your app is NOT active at this point.
   125             */
   126             return 0;
   127         case SDL_APP_WILLENTERFOREGROUND:
   128             /* This call happens when your app is coming back to the foreground.
   129                Restore all your state here.
   130             */
   131             return 0;
   132         case SDL_APP_DIDENTERFOREGROUND:
   133             /* Restart your loops here.
   134                Your app is interactive and getting CPU again.
   135             */
   136             return 0;
   137         default:
   138             /* No special processing, add it to the event queue */
   139             return 1;
   140         }
   141     }
   142     
   143     int main(int argc, char *argv[])
   144     {
   145         SDL_SetEventFilter(HandleAppEvents, NULL);
   146     
   147         ... run your main loop
   148     
   149         return 0;
   150     }
   151 
   152     
   153 ==============================================================================
   154 Notes -- Accelerometer as Joystick
   155 ==============================================================================
   156 
   157 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.
   158 
   159 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.
   160 
   161 ==============================================================================
   162 Notes -- OpenGL ES
   163 ==============================================================================
   164 
   165 Your SDL application for iOS uses OpenGL ES for video by default.
   166 
   167 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.
   168 
   169 If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
   170 
   171 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.
   172 
   173 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:
   174 
   175 - The drawable Renderbuffer must be bound to the GL_RENDERBUFFER binding point when SDL_GL_SwapWindow is called.
   176 - The drawable Framebuffer Object must be bound while rendering to the screen and when SDL_GL_SwapWindow is called.
   177 - 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.
   178 
   179 The above objects can be obtained via SDL_GetWindowWMInfo (in SDL_syswm.h).
   180 
   181 ==============================================================================
   182 Notes -- Keyboard
   183 ==============================================================================
   184 
   185 The SDL keyboard API has been extended to support on-screen keyboards:
   186 
   187 void SDL_StartTextInput()
   188 	-- enables text events and reveals the onscreen keyboard.
   189 
   190 void SDL_StopTextInput()
   191 	-- disables text events and hides the onscreen keyboard.
   192 
   193 SDL_bool SDL_IsTextInputActive()
   194 	-- returns whether or not text events are enabled (and the onscreen keyboard is visible)
   195 
   196 
   197 ==============================================================================
   198 Notes -- Reading and Writing files
   199 ==============================================================================
   200 
   201 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.
   202 
   203 Once your application is installed its directory tree looks like:
   204 
   205     MySDLApp Home/
   206         MySDLApp.app
   207         Documents/
   208         Library/
   209             Preferences/
   210         tmp/
   211 
   212 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".  
   213 
   214 More information on this subject is available here:
   215 http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
   216 
   217 ==============================================================================
   218 Notes -- iPhone SDL limitations
   219 ==============================================================================
   220 
   221 Windows:
   222 	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).
   223 
   224 Textures:
   225 	The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
   226 
   227 Loading Shared Objects:
   228 	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.
   229 
   230 ==============================================================================
   231 Game Center 
   232 ==============================================================================
   233 
   234 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:
   235 
   236     int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
   237 
   238 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.
   239 
   240 e.g.
   241 
   242     extern "C"
   243     void ShowFrame(void*)
   244     {
   245         ... do event handling, frame logic and rendering ...
   246     }
   247     
   248     int main(int argc, char *argv[])
   249     {
   250         ... initialize game ...
   251     
   252     #if __IPHONEOS__
   253         // Initialize the Game Center for scoring and matchmaking
   254         InitGameCenter();
   255     
   256         // Set up the game to run in the window animation callback on iOS
   257         // so that Game Center and so forth works correctly.
   258         SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
   259     #else
   260         while ( running ) {
   261             ShowFrame(0);
   262             DelayFrame();
   263         }
   264     #endif
   265         return 0;
   266     }