docs/README-ios.md
author Sam Lantinga <slouken@libsdl.org>
Mon, 29 Oct 2018 19:58:59 -0700
changeset 12371 41b93d8303d6
parent 12368 9bb50edccc46
permissions -rw-r--r--
Backed out changeset 9bb50edccc46, SDL_JOYSTICK_HIDAPI is only used on iOS for Steam Controller support, which is not publicly available.
     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 1.  Open SDL.xcodeproj (located in Xcode-iOS/SDL) in Xcode.
    13 2.  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. cd (PATH WHERE THE SDL CODE IS)/build-scripts
    29 2. ./iosbuild.sh
    30 
    31 If everything goes fine, you should see a build/ios directory, inside there's
    32 two directories "lib" and "include". 
    33 "include" contains a copy of the SDL headers that you'll need for your project,
    34 make sure to configure XCode to look for headers there.
    35 "lib" contains find two files, libSDL2.a and libSDL2main.a, you have to add both 
    36 to your XCode project. These libraries contain three architectures in them,
    37 armv6 for legacy devices, armv7, and i386 (for the simulator).
    38 By default, iosbuild.sh will autodetect the SDK version you have installed using 
    39 xcodebuild -showsdks, and build for iOS >= 3.0, you can override this behaviour 
    40 by setting the MIN_OS_VERSION variable, ie:
    41 
    42 MIN_OS_VERSION=4.2 ./iosbuild.sh
    43 
    44 ==============================================================================
    45 Using the Simple DirectMedia Layer for iOS
    46 ==============================================================================
    47 
    48 FIXME: This needs to be updated for the latest methods
    49 
    50 Here is the easiest method:
    51 1.  Build the SDL library (libSDL2.a) and the iPhone SDL Application template.
    52 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.
    53 3.  Start a new project using the template.  The project should be immediately ready for use with SDL.
    54 
    55 Here is a more manual method:
    56 1.  Create a new iOS view based application.
    57 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.
    58 3.  Include the SDL header files in your project.
    59 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.
    60 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.
    61 
    62 ==============================================================================
    63 Notes -- Retina / High-DPI and window sizes
    64 ==============================================================================
    65 
    66 Window and display mode sizes in SDL are in "screen coordinates" (or "points",
    67 in Apple's terminology) rather than in pixels. On iOS this means that a window
    68 created on an iPhone 6 will have a size in screen coordinates of 375 x 667,
    69 rather than a size in pixels of 750 x 1334. All iOS apps are expected to
    70 size their content based on screen coordinates / points rather than pixels,
    71 as this allows different iOS devices to have different pixel densities
    72 (Retina versus non-Retina screens, etc.) without apps caring too much.
    73 
    74 By default SDL will not use the full pixel density of the screen on
    75 Retina/high-dpi capable devices. Use the SDL_WINDOW_ALLOW_HIGHDPI flag when
    76 creating your window to enable high-dpi support.
    77 
    78 When high-dpi support is enabled, SDL_GetWindowSize() and display mode sizes
    79 will still be in "screen coordinates" rather than pixels, but the window will
    80 have a much greater pixel density when the device supports it, and the
    81 SDL_GL_GetDrawableSize() or SDL_GetRendererOutputSize() functions (depending on
    82 whether raw OpenGL or the SDL_Render API is used) can be queried to determine
    83 the size in pixels of the drawable screen framebuffer.
    84 
    85 Some OpenGL ES functions such as glViewport expect sizes in pixels rather than
    86 sizes in screen coordinates. When doing 2D rendering with OpenGL ES, an
    87 orthographic projection matrix using the size in screen coordinates
    88 (SDL_GetWindowSize()) can be used in order to display content at the same scale
    89 no matter whether a Retina device is used or not.
    90 
    91 ==============================================================================
    92 Notes -- Application events
    93 ==============================================================================
    94 
    95 On iOS the application goes through a fixed life cycle and you will get
    96 notifications of state changes via application events. When these events
    97 are delivered you must handle them in an event callback because the OS may
    98 not give you any processing time after the events are delivered.
    99 
   100 e.g.
   101 
   102     int HandleAppEvents(void *userdata, SDL_Event *event)
   103     {
   104         switch (event->type)
   105         {
   106         case SDL_APP_TERMINATING:
   107             /* Terminate the app.
   108                Shut everything down before returning from this function.
   109             */
   110             return 0;
   111         case SDL_APP_LOWMEMORY:
   112             /* You will get this when your app is paused and iOS wants more memory.
   113                Release as much memory as possible.
   114             */
   115             return 0;
   116         case SDL_APP_WILLENTERBACKGROUND:
   117             /* Prepare your app to go into the background.  Stop loops, etc.
   118                This gets called when the user hits the home button, or gets a call.
   119             */
   120             return 0;
   121         case SDL_APP_DIDENTERBACKGROUND:
   122             /* This will get called if the user accepted whatever sent your app to the background.
   123                If the user got a phone call and canceled it, you'll instead get an SDL_APP_DIDENTERFOREGROUND event and restart your loops.
   124                When you get this, you have 5 seconds to save all your state or the app will be terminated.
   125                Your app is NOT active at this point.
   126             */
   127             return 0;
   128         case SDL_APP_WILLENTERFOREGROUND:
   129             /* This call happens when your app is coming back to the foreground.
   130                Restore all your state here.
   131             */
   132             return 0;
   133         case SDL_APP_DIDENTERFOREGROUND:
   134             /* Restart your loops here.
   135                Your app is interactive and getting CPU again.
   136             */
   137             return 0;
   138         default:
   139             /* No special processing, add it to the event queue */
   140             return 1;
   141         }
   142     }
   143     
   144     int main(int argc, char *argv[])
   145     {
   146         SDL_SetEventFilter(HandleAppEvents, NULL);
   147     
   148         ... run your main loop
   149     
   150         return 0;
   151     }
   152 
   153     
   154 ==============================================================================
   155 Notes -- Accelerometer as Joystick
   156 ==============================================================================
   157 
   158 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.
   159 
   160 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.
   161 
   162 ==============================================================================
   163 Notes -- OpenGL ES
   164 ==============================================================================
   165 
   166 Your SDL application for iOS uses OpenGL ES for video by default.
   167 
   168 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().
   169 
   170 If your application doesn't use OpenGL's depth buffer, you may find significant performance improvement by setting SDL_GL_DEPTH_SIZE to 0.
   171 
   172 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.
   173 
   174 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:
   175 
   176 - The drawable Renderbuffer must be bound to the GL_RENDERBUFFER binding point when SDL_GL_SwapWindow() is called.
   177 - The drawable Framebuffer Object must be bound while rendering to the screen and when SDL_GL_SwapWindow() is called.
   178 - 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.
   179 
   180 The above objects can be obtained via SDL_GetWindowWMInfo() (in SDL_syswm.h).
   181 
   182 ==============================================================================
   183 Notes -- Keyboard
   184 ==============================================================================
   185 
   186 The SDL keyboard API has been extended to support on-screen keyboards:
   187 
   188 void SDL_StartTextInput()
   189 	-- enables text events and reveals the onscreen keyboard.
   190 
   191 void SDL_StopTextInput()
   192 	-- disables text events and hides the onscreen keyboard.
   193 
   194 SDL_bool SDL_IsTextInputActive()
   195 	-- returns whether or not text events are enabled (and the onscreen keyboard is visible)
   196 
   197 
   198 ==============================================================================
   199 Notes -- Reading and Writing files
   200 ==============================================================================
   201 
   202 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.
   203 
   204 Once your application is installed its directory tree looks like:
   205 
   206     MySDLApp Home/
   207         MySDLApp.app
   208         Documents/
   209         Library/
   210             Preferences/
   211         tmp/
   212 
   213 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".  
   214 
   215 More information on this subject is available here:
   216 http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/Introduction/Introduction.html
   217 
   218 ==============================================================================
   219 Notes -- iPhone SDL limitations
   220 ==============================================================================
   221 
   222 Windows:
   223 	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).
   224 
   225 Textures:
   226 	The optimal texture formats on iOS are SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_ABGR8888, SDL_PIXELFORMAT_BGR888, and SDL_PIXELFORMAT_RGB24 pixel formats.
   227 
   228 Loading Shared Objects:
   229 	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.
   230 
   231 ==============================================================================
   232 Game Center 
   233 ==============================================================================
   234 
   235 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:
   236 
   237     int SDL_iPhoneSetAnimationCallback(SDL_Window * window, int interval, void (*callback)(void*), void *callbackParam);
   238 
   239 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.
   240 
   241 e.g.
   242 
   243     extern "C"
   244     void ShowFrame(void*)
   245     {
   246         ... do event handling, frame logic and rendering ...
   247     }
   248     
   249     int main(int argc, char *argv[])
   250     {
   251         ... initialize game ...
   252     
   253     #if __IPHONEOS__
   254         // Initialize the Game Center for scoring and matchmaking
   255         InitGameCenter();
   256     
   257         // Set up the game to run in the window animation callback on iOS
   258         // so that Game Center and so forth works correctly.
   259         SDL_iPhoneSetAnimationCallback(window, 1, ShowFrame, NULL);
   260     #else
   261         while ( running ) {
   262             ShowFrame(0);
   263             DelayFrame();
   264         }
   265     #endif
   266         return 0;
   267     }
   268 
   269 ==============================================================================
   270 Deploying to older versions of iOS
   271 ==============================================================================
   272 
   273 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
   274 
   275 In order to do that you need to download an older version of Xcode:
   276 https://developer.apple.com/download/more/?name=Xcode
   277 
   278 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
   279 
   280 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
   281 
   282 Open your project and set your deployment target to the desired version of iOS
   283 
   284 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