SDL  2.0
docs/README-android.md
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1 Android
2 ================================================================================
3 
4 Matt Styles wrote a tutorial on building SDL for Android with Visual Studio:
5 http://trederia.blogspot.de/2017/03/building-sdl2-for-android-with-visual.html
6 
7 The rest of this README covers the old style build process.
8 
9 ================================================================================
10  Requirements
11 ================================================================================
12 
13 Android SDK (version 16 or later)
14 https://developer.android.com/sdk/index.html
15 
16 Android NDK r7 or later
17 https://developer.android.com/tools/sdk/ndk/index.html
18 
19 Minimum API level supported by SDL: 10 (Android 2.3.3)
20 Joystick support is available for API level >= 12 devices.
21 
22 ================================================================================
23  How the port works
24 ================================================================================
25 
26 - Android applications are Java-based, optionally with parts written in C
27 - As SDL apps are C-based, we use a small Java shim that uses JNI to talk to
28  the SDL library
29 - This means that your application C code must be placed inside an Android
30  Java project, along with some C support code that communicates with Java
31 - This eventually produces a standard Android .apk package
32 
33 The Android Java code implements an "Activity" and can be found in:
34 android-project/src/org/libsdl/app/SDLActivity.java
35 
36 The Java code loads your game code, the SDL shared library, and
37 dispatches to native functions implemented in the SDL library:
38 src/core/android/SDL_android.c
39 
40 Your project must include some glue code that starts your main() routine:
41 src/main/android/SDL_android_main.c
42 
43 
44 ================================================================================
45  Building an app
46 ================================================================================
47 
48 For simple projects you can use the script located at build-scripts/androidbuild.sh
49 
50 There's two ways of using it:
51 
52  androidbuild.sh com.yourcompany.yourapp < sources.list
53  androidbuild.sh com.yourcompany.yourapp source1.c source2.c ...sourceN.c
54 
55 sources.list should be a text file with a source file name in each line
56 Filenames should be specified relative to the current directory, for example if
57 you are in the build-scripts directory and want to create the testgles.c test, you'll
58 run:
59 
60  ./androidbuild.sh org.libsdl.testgles ../test/testgles.c
61 
62 One limitation of this script is that all sources provided will be aggregated into
63 a single directory, thus all your source files should have a unique name.
64 
65 Once the project is complete the script will tell you where the debug APK is located.
66 If you want to create a signed release APK, you can use the project created by this
67 utility to generate it.
68 
69 Finally, a word of caution: re running androidbuild.sh wipes any changes you may have
70 done in the build directory for the app!
71 
72 
73 For more complex projects, follow these instructions:
74 
75 1. Copy the android-project directory wherever you want to keep your projects
76  and rename it to the name of your project.
77 2. Move or symlink this SDL directory into the "<project>/jni" directory
78 3. Edit "<project>/jni/src/Android.mk" to include your source files
79 4. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
80 
81 If you want to use the Eclipse IDE, skip to the Eclipse section below.
82 
83 5. Create "<project>/local.properties" and use that to point to the Android SDK directory, by writing a line with the following form:
84 
85  sdk.dir=PATH_TO_ANDROID_SDK
86 
87 6. Run 'ant debug' in android/project. This compiles the .java and eventually
88  creates a .apk with the native code embedded
89 7. 'ant debug install' will push the apk to the device or emulator (if connected)
90 
91 Here's an explanation of the files in the Android project, so you can customize them:
92 
93  android-project/
94  AndroidManifest.xml - package manifest. Among others, it contains the class name
95  of the main Activity and the package name of the application.
96  build.properties - empty
97  build.xml - build description file, used by ant. The actual application name
98  is specified here.
99  default.properties - holds the target ABI for the application, android-10 and up
100  project.properties - holds the target ABI for the application, android-10 and up
101  local.properties - holds the SDK path, you should change this to the path to your SDK
102  jni/ - directory holding native code
103  jni/Android.mk - Android makefile that can call recursively the Android.mk files
104  in all subdirectories
105  jni/SDL/ - (symlink to) directory holding the SDL library files
106  jni/SDL/Android.mk - Android makefile for creating the SDL shared library
107  jni/src/ - directory holding your C/C++ source
108  jni/src/Android.mk - Android makefile that you should customize to include your
109  source code and any library references
110  res/ - directory holding resources for your application
111  res/drawable-* - directories holding icons for different phone hardware. Could be
112  one dir called "drawable".
113  res/layout/main.xml - Usually contains a file main.xml, which declares the screen layout.
114  We don't need it because we use the SDL video output.
115  res/values/strings.xml - strings used in your application, including the application name
116  shown on the phone.
117  src/org/libsdl/app/SDLActivity.java - the Java class handling the initialization and binding
118  to SDL. Be very careful changing this, as the SDL library relies
119  on this implementation.
120 
121 
122 ================================================================================
123  Build an app with static linking of libSDL
124 ================================================================================
125 
126 This build uses the Android NDK module system.
127 
128 Instructions:
129 1. Copy the android-project directory wherever you want to keep your projects
130  and rename it to the name of your project.
131 2. Rename "<project>/jni/src/Android_static.mk" to "<project>/jni/src/Android.mk"
132  (overwrite the existing one)
133 3. Edit "<project>/jni/src/Android.mk" to include your source files
134 4. create and export an environment variable named NDK_MODULE_PATH that points
135  to the parent directory of this SDL directory. e.g.:
136 
137  export NDK_MODULE_PATH="$PWD"/..
138 
139 5. Edit "<project>/src/org/libsdl/app/SDLActivity.java" and remove the call to
140  System.loadLibrary("SDL2").
141 6. Run 'ndk-build' (a script provided by the NDK). This compiles the C source
142 
143 
144 ================================================================================
145  Customizing your application name
146 ================================================================================
147 
148 To customize your application name, edit AndroidManifest.xml and replace
149 "org.libsdl.app" with an identifier for your product package.
150 
151 Then create a Java class extending SDLActivity and place it in a directory
152 under src matching your package, e.g.
153 
154  src/com/gamemaker/game/MyGame.java
155 
156 Here's an example of a minimal class file:
157 
158  --- MyGame.java --------------------------
159  package com.gamemaker.game;
160 
161  import org.libsdl.app.SDLActivity;
162 
163  /**
164  * A sample wrapper class that just calls SDLActivity
165  */
166 
167  public class MyGame extends SDLActivity { }
168 
169  ------------------------------------------
170 
171 Then replace "SDLActivity" in AndroidManifest.xml with the name of your
172 class, .e.g. "MyGame"
173 
174 ================================================================================
175  Customizing your application icon
176 ================================================================================
177 
178 Conceptually changing your icon is just replacing the "ic_launcher.png" files in
179 the drawable directories under the res directory. There are four directories for
180 different screen sizes. These can be replaced with one dir called "drawable",
181 containing an icon file "ic_launcher.png" with dimensions 48x48 or 72x72.
182 
183 You may need to change the name of your icon in AndroidManifest.xml to match
184 this icon filename.
185 
186 ================================================================================
187  Loading assets
188 ================================================================================
189 
190 Any files you put in the "assets" directory of your android-project directory
191 will get bundled into the application package and you can load them using the
192 standard functions in SDL_rwops.h.
193 
194 There are also a few Android specific functions that allow you to get other
195 useful paths for saving and loading data:
196 * SDL_AndroidGetInternalStoragePath()
197 * SDL_AndroidGetExternalStorageState()
198 * SDL_AndroidGetExternalStoragePath()
199 
200 See SDL_system.h for more details on these functions.
201 
202 The asset packaging system will, by default, compress certain file extensions.
203 SDL includes two asset file access mechanisms, the preferred one is the so
204 called "File Descriptor" method, which is faster and doesn't involve the Dalvik
205 GC, but given this method does not work on compressed assets, there is also the
206 "Input Stream" method, which is automatically used as a fall back by SDL. You
207 may want to keep this fact in mind when building your APK, specially when large
208 files are involved.
209 For more information on which extensions get compressed by default and how to
210 disable this behaviour, see for example:
211 
212 http://ponystyle.com/blog/2010/03/26/dealing-with-asset-compression-in-android-apps/
213 
214 ================================================================================
215  Pause / Resume behaviour
216 ================================================================================
217 
218 If SDL is compiled with SDL_ANDROID_BLOCK_ON_PAUSE defined (the default),
219 the event loop will block itself when the app is paused (ie, when the user
220 returns to the main Android dashboard). Blocking is better in terms of battery
221 use, and it allows your app to spring back to life instantaneously after resume
222 (versus polling for a resume message).
223 
224 Upon resume, SDL will attempt to restore the GL context automatically.
225 In modern devices (Android 3.0 and up) this will most likely succeed and your
226 app can continue to operate as it was.
227 
228 However, there's a chance (on older hardware, or on systems under heavy load),
229 where the GL context can not be restored. In that case you have to listen for
230 a specific message, (which is not yet implemented!) and restore your textures
231 manually or quit the app (which is actually the kind of behaviour you'll see
232 under iOS, if the OS can not restore your GL context it will just kill your app)
233 
234 ================================================================================
235  Threads and the Java VM
236 ================================================================================
237 
238 For a quick tour on how Linux native threads interoperate with the Java VM, take
239 a look here: https://developer.android.com/guide/practices/jni.html
240 
241 If you want to use threads in your SDL app, it's strongly recommended that you
242 do so by creating them using SDL functions. This way, the required attach/detach
243 handling is managed by SDL automagically. If you have threads created by other
244 means and they make calls to SDL functions, make sure that you call
245 Android_JNI_SetupThread() before doing anything else otherwise SDL will attach
246 your thread automatically anyway (when you make an SDL call), but it'll never
247 detach it.
248 
249 ================================================================================
250  Using STL
251 ================================================================================
252 
253 You can use STL in your project by creating an Application.mk file in the jni
254 folder and adding the following line:
255 
256  APP_STL := stlport_static
257 
258 For more information check out CPLUSPLUS-SUPPORT.html in the NDK documentation.
259 
260 ================================================================================
261  Additional documentation
262 ================================================================================
263 
264 The documentation in the NDK docs directory is very helpful in understanding the
265 build process and how to work with native code on the Android platform.
266 
267 The best place to start is with docs/OVERVIEW.TXT
268 
269 
270 ================================================================================
271  Using Eclipse
272 ================================================================================
273 
274 First make sure that you've installed Eclipse and the Android extensions as described here:
275  https://developer.android.com/tools/sdk/eclipse-adt.html
276 
277 Once you've copied the SDL android project and customized it, you can create an Eclipse project from it:
278  * File -> New -> Other
279  * Select the Android -> Android Project wizard and click Next
280  * Enter the name you'd like your project to have
281  * Select "Create project from existing source" and browse for your project directory
282  * Make sure the Build Target is set to Android 3.1 (API 12)
283  * Click Finish
284 
285 
286 ================================================================================
287  Using the emulator
288 ================================================================================
289 
290 There are some good tips and tricks for getting the most out of the
291 emulator here: https://developer.android.com/tools/devices/emulator.html
292 
293 Especially useful is the info on setting up OpenGL ES 2.0 emulation.
294 
295 Notice that this software emulator is incredibly slow and needs a lot of disk space.
296 Using a real device works better.
297 
298 ================================================================================
299  Troubleshooting
300 ================================================================================
301 
302 You can create and run an emulator from the Eclipse IDE:
303  * Window -> Android SDK and AVD Manager
304 
305 You can see if adb can see any devices with the following command:
306 
307  adb devices
308 
309 You can see the output of log messages on the default device with:
310 
311  adb logcat
312 
313 You can push files to the device with:
314 
315  adb push local_file remote_path_and_file
316 
317 You can push files to the SD Card at /sdcard, for example:
318 
319  adb push moose.dat /sdcard/moose.dat
320 
321 You can see the files on the SD card with a shell command:
322 
323  adb shell ls /sdcard/
324 
325 You can start a command shell on the default device with:
326 
327  adb shell
328 
329 You can remove the library files of your project (and not the SDL lib files) with:
330 
331  ndk-build clean
332 
333 You can do a build with the following command:
334 
335  ndk-build
336 
337 You can see the complete command line that ndk-build is using by passing V=1 on the command line:
338 
339  ndk-build V=1
340 
341 If your application crashes in native code, you can use addr2line to convert the
342 addresses in the stack trace to lines in your code.
343 
344 For example, if your crash looks like this:
345 
346  I/DEBUG ( 31): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 400085d0
347  I/DEBUG ( 31): r0 00000000 r1 00001000 r2 00000003 r3 400085d4
348  I/DEBUG ( 31): r4 400085d0 r5 40008000 r6 afd41504 r7 436c6a7c
349  I/DEBUG ( 31): r8 436c6b30 r9 435c6fb0 10 435c6f9c fp 4168d82c
350  I/DEBUG ( 31): ip 8346aff0 sp 436c6a60 lr afd1c8ff pc afd1c902 cpsr 60000030
351  I/DEBUG ( 31): #00 pc 0001c902 /system/lib/libc.so
352  I/DEBUG ( 31): #01 pc 0001ccf6 /system/lib/libc.so
353  I/DEBUG ( 31): #02 pc 000014bc /data/data/org.libsdl.app/lib/libmain.so
354  I/DEBUG ( 31): #03 pc 00001506 /data/data/org.libsdl.app/lib/libmain.so
355 
356 You can see that there's a crash in the C library being called from the main code.
357 I run addr2line with the debug version of my code:
358 
359  arm-eabi-addr2line -C -f -e obj/local/armeabi/libmain.so
360 
361 and then paste in the number after "pc" in the call stack, from the line that I care about:
362 000014bc
363 
364 I get output from addr2line showing that it's in the quit function, in testspriteminimal.c, on line 23.
365 
366 You can add logging to your code to help show what's happening:
367 
368  #include <android/log.h>
369 
370  __android_log_print(ANDROID_LOG_INFO, "foo", "Something happened! x = %d", x);
371 
372 If you need to build without optimization turned on, you can create a file called
373 "Application.mk" in the jni directory, with the following line in it:
374 
375  APP_OPTIM := debug
376 
377 
378 ================================================================================
379  Memory debugging
380 ================================================================================
381 
382 The best (and slowest) way to debug memory issues on Android is valgrind.
383 Valgrind has support for Android out of the box, just grab code using:
384 
385  svn co svn://svn.valgrind.org/valgrind/trunk valgrind
386 
387 ... and follow the instructions in the file README.android to build it.
388 
389 One thing I needed to do on Mac OS X was change the path to the toolchain,
390 and add ranlib to the environment variables:
391 export RANLIB=$NDKROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/darwin-x86/bin/arm-linux-androideabi-ranlib
392 
393 Once valgrind is built, you can create a wrapper script to launch your
394 application with it, changing org.libsdl.app to your package identifier:
395 
396  --- start_valgrind_app -------------------
397  #!/system/bin/sh
398  export TMPDIR=/data/data/org.libsdl.app
399  exec /data/local/Inst/bin/valgrind --log-file=/sdcard/valgrind.log --error-limit=no $*
400  ------------------------------------------
401 
402 Then push it to the device:
403 
404  adb push start_valgrind_app /data/local
405 
406 and make it executable:
407 
408  adb shell chmod 755 /data/local/start_valgrind_app
409 
410 and tell Android to use the script to launch your application:
411 
412  adb shell setprop wrap.org.libsdl.app "logwrapper /data/local/start_valgrind_app"
413 
414 If the setprop command says "could not set property", it's likely that
415 your package name is too long and you should make it shorter by changing
416 AndroidManifest.xml and the path to your class file in android-project/src
417 
418 You can then launch your application normally and waaaaaaaiiittt for it.
419 You can monitor the startup process with the logcat command above, and
420 when it's done (or even while it's running) you can grab the valgrind
421 output file:
422 
423  adb pull /sdcard/valgrind.log
424 
425 When you're done instrumenting with valgrind, you can disable the wrapper:
426 
427  adb shell setprop wrap.org.libsdl.app ""
428 
429 ================================================================================
430  Graphics debugging
431 ================================================================================
432 
433 If you are developing on a compatible Tegra-based tablet, NVidia provides
434 Tegra Graphics Debugger at their website. Because SDL2 dynamically loads EGL
435 and GLES libraries, you must follow their instructions for installing the
436 interposer library on a rooted device. The non-rooted instructions are not
437 compatible with applications that use SDL2 for video.
438 
439 The Tegra Graphics Debugger is available from NVidia here:
440 https://developer.nvidia.com/tegra-graphics-debugger
441 
442 ================================================================================
443  Why is API level 10 the minimum required?
444 ================================================================================
445 
446 API level 10 is the minimum required level at runtime (that is, on the device)
447 because SDL requires some functionality for running not
448 available on older devices. Since the incorporation of joystick support into SDL,
449 the minimum SDK required to *build* SDL is version 12. Devices running API levels
450 10-11 are still supported, only with the joystick functionality disabled.
451 
452 Support for native OpenGL ES and ES2 applications was introduced in the NDK for
453 API level 4 and 8. EGL was made a stable API in the NDK for API level 9, which
454 has since then been obsoleted, with the recommendation to developers to bump the
455 required API level to 10.
456 As of this writing, according to https://developer.android.com/about/dashboards/index.html
457 about 90% of the Android devices accessing Google Play support API level 10 or
458 higher (March 2013).
459 
460 ================================================================================
461  A note regarding the use of the "dirty rectangles" rendering technique
462 ================================================================================
463 
464 If your app uses a variation of the "dirty rectangles" rendering technique,
465 where you only update a portion of the screen on each frame, you may notice a
466 variety of visual glitches on Android, that are not present on other platforms.
467 This is caused by SDL's use of EGL as the support system to handle OpenGL ES/ES2
468 contexts, in particular the use of the eglSwapBuffers function. As stated in the
469 documentation for the function "The contents of ancillary buffers are always
470 undefined after calling eglSwapBuffers".
471 Setting the EGL_SWAP_BEHAVIOR attribute of the surface to EGL_BUFFER_PRESERVED
472 is not possible for SDL as it requires EGL 1.4, available only on the API level
473 17+, so the only workaround available on this platform is to redraw the entire
474 screen each frame.
475 
476 Reference: http://www.khronos.org/registry/egl/specs/EGLTechNote0001.html
477 
478 ================================================================================
479  Known issues
480 ================================================================================
481 
482 - The number of buttons reported for each joystick is hardcoded to be 36, which
483 is the current maximum number of buttons Android can report.
484 
void loop()
Definition: checkkeys.c:152
one
Definition: e_pow.c:78
GLdouble s
Definition: SDL_opengl.h:2063
SDL_PRINTF_FORMAT_STRING const char int SDL_PRINTF_FORMAT_STRING const char int SDL_PRINTF_FORMAT_STRING const char int SDL_PRINTF_FORMAT_STRING const char const char SDL_SCANF_FORMAT_STRING const char return SDL_ThreadFunction const char void return Uint32 return Uint32 SDL_AssertionHandler void SDL_SpinLock SDL_atomic_t int int return SDL_atomic_t return void void void return void return int return SDL_AudioSpec SDL_AudioSpec return int int return return int SDL_RWops int SDL_AudioSpec Uint8 Uint32 * e
GLsizei GLenum * sources
GLint GLint GLint GLint GLint x
Definition: SDL_opengl.h:1574
GLuint GLsizei const GLchar * message
GLint level
Definition: SDL_opengl.h:1572
static int available()
Definition: video.c:356
static screen_context_t context
Definition: video.c:25
GLfloat f
GLuint start
Definition: SDL_opengl.h:1571
GLenum src
GLuint const GLchar * name
GLuint res
GLfixed GLfixed GLint GLint GLfixed points
static SDL_AudioDeviceID device
Definition: loopwave.c:37
GLenum GLsizei GLsizei GLint * values
int Run(void *data)
Definition: testlock.c:65
GLsizei const GLint * box
Definition: gl2ext.h:2208
int done
Definition: checkkeys.c:28
GLsizei GLsizei GLchar * source
GLenum GLenum variable
int paused
Definition: testoverlay2.c:149
#define I(x, y, z)
Definition: SDL_test_md5.c:76
GLsizei GLenum GLsizei GLsizei GLuint memory
Definition: gl2ext.h:1474
static SDL_Thread * threads[6]
Definition: testlock.c:25
EGLOutputPortEXT port
Definition: eglext.h:752
GLsizei const GLchar *const * path
#define main
Definition: SDL_main.h:104
GLhandleARB obj
GLboolean GLboolean GLboolean GLboolean a
GLuint in
EGLDeviceEXT * devices
Definition: eglext.h:621
GLsizei const GLchar *const * strings
GLdouble GLdouble t
Definition: SDL_opengl.h:2071
GLbyte by