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This is libSDL 1.2 and 1.3 ported to Google Android (also bunch of other libs included).
Alien Blaster game is used as working example (original sources: http://www.schwardtnet.de/alienblaster/ ).
Installation
============
This should be compiled with Android 2.2 SDK and NDK r4 - google for them and install them as described in their docs
(the application will run on Android 1.6 and above).
You'll need to install Ant too.
The most supported environnment for that port is Linux, MacOs should be okay too,
however if you'll use launchConfigure.sh script you'll have to replace "linux-x86" to "darwin-x86" inside it.
If you're developing on Windows you'd better install andLinux or Ubuntu+Wubi, to get proper Linux environment
running inside Windows, then install Linux toolchain on it. I was told andLinux compiles faster than Cygwin.
Also you'll need full set of Linux utils and symlinks support to launch ChangeAppSettings.sh (sh, grep, sed, tr).
How to compile Alien Blaster demo application
=============================================
Go to "project" directory and launch command
android update project -p .
Then go back, edit file build.sh if needed to add NDK dir to your PATH, then launch it.
Hopefully it will compile a bunch of libs under project/libs/armeabi,
create file project/bin/DemoActivity-debug.apk and install it on your device or emulator.
Then you can test it by launching Alien Blaster icon from Android applications menu.
It's designed for 640x480, so if you have smaller screen it will be resized.
Note: The game enforces horizontal screen orientation, you may open your keyboard and use it for
additional keys - the phone will just keep current screen orientation.
Note that you may use Volume up/down and Camera keys as game inputs -
you'll have to redefine them in game keyconfig menu.
Keys Home, Search and End Call will force application quit, and because
of a bug in my SDL implementation application will crash.
Back key is mapped to Escape, and Menu is mapped to Enter.
Newer Android phones like HTC Evo have no keyboard at all, so there are just 3 usable keys -
Menu, Volume Up and Volume Down (and Escape of course).
Because of that the accelerometer is configured to trigger cursor key events.
This port also supports GL ES + SDL combo - there is GLXGears demo app in project/jni/application/glxgears,
remove project/jni/application/src symlink and make new one pointing to glxgears,
also you'll have to enable Z-Buffer in ChangeAppSettings.sh.
Note that GL ES is NOT pure OpenGL - there are no glBegin() and glEnd() call and other widely used functions,
and generally it will take a lot of effort to port pure OpenGL application to GL ES.
How to compile your own application
===================================
When porting you own app, first of all ensure that your application supports
native RGB_565 pixel format and AUDIO_S8 or AUDIO_S16 audio format
(there is RGB_565 pixelformat even for OpenGL, not BGR_565 as all other OpenGL implementation have).
Colorkey images are supported using RGBA_5551 pixelformat with 1-bit alpha (SDL does conversion internally,
for you they are just RGB_565 surfaces), alpha surfaces have RGBA_4444 format.
See file project/jni/application/alienblaster/SdlForwardCompat.h
to learn how to make your application use SDL 1.3 instead of SDL 1.2 without much pain.
HTC G1/Nexus One has native screen resolution 480x320, HTC Evo has 800x480, you may toggle automatic
screen resizing in ChangeAppSettings.sh and draw to virtual 640x480 screen -
it will be HW accelerated and will not impact performance much.
SDL_ListModes()[0] will always return native screen resolution.
Also make sure that your HW textures are not wider than 1024 pixels, or it will fail to allocate such
texture on HTC G1. Software surfaces may be of any size of course (but you don't want to do expensive memcpy).
Alternatively, SDL 1.2 is available too, you may use it with SW video as usual, however if you want HW acceleration
there are few restrictions: you cannot currently blit SW surface to screen, it should be only HW surface,
also alpha-surfaces seem to not work (did not check it thoroughly) - you still can use per-surface alpha.
Basically your code should be like:
// Init HW-accelerated video
SDL_SetVideoMode( 640, 480, 16, SDL_DOUBLEBUF | SDL_HWSURFACE );
// Load graphics
SDL_Surface *sprite = IMG_Load( "sprite.png" );
// Set pink color as transparent
SDL_SetColorKey( sprite, SDL_SRCCOLORKEY, SDL_MapRGB(sprite->format, 255, 0, 255) );
// Create HW-accelerated surface
SDL_Surface * hwSprite = SDL_DisplayFormat(sprite);
// Set per-surface alpha, if necessary
SDL_SetAlpha( hwSprite, SDL_SRCALPHA, 128 );
// Blit it in HW-accelerated way
SDL_BlitSurface(hwSprite, sourceRect, SDL_GetVideoSurface(), &targetRect);
// Wrong, blitting SW surfaces to screen not supported
SDL_BlitSurface(sprite, sourceRect, SDL_GetVideoSurface(), &targetRect);
// Wrong, copying from video surface not supported
SDL_BlitSurface(SDL_GetVideoSurface(), sourceRect, sprite, &targetRect);
To compile your own app, put your app sources into project/jni/application dir, and change symlink "src"
to point to your app, then launch script ChangeAppSettings.sh - it will ask few questions and modify some Java code.
The C++ files shall have .cpp extension to be compiled, rename them if necessary.
Also you can replace icon image at project/res/drawable/icon.png.
Then you can launch build.sh.
Application data is not bundled with app itself - it should be downloaded from net on first run.
Create .ZIP file with your application data, and put it somewhere on HTTP server - ChangeAppSettings.sh
will ask you for the URL.
If you'll release new version of data files you should change download URL and update your app as well -
the app will re-download the data if URL does not match the saved URL from previous download.
If you'll add new libs - add them to project/jni/, copy Android.mk from existing lib, and
add libname to project/jni/<yourapp>/Android.mk
How to compile your own application using automake/configure scripts
====================================================================
There is limited support for "configure" scripts, I've managed to compile lbreakout2 that way,
though ./configure scripts tend to have stupid bugs in various places, avoid using that method if you can.
1. Download lbreakout2-2.6.1.tar.gz from http://lgames.sourceforge.net/, unpack it to project/jni/application dir.
2. Determine libraries needed for your app, launch ChangeAppSettings.sh, select correct libSDL version
(1.2 for lbreakout2), and correct libs (sdl_mixer sdl_image sdl_net for lbreakout2), also change name etc.
3. Launch ./build.sh, wait till it builds all .so files
4. Go to project/jni/application/lbreakout2-2.6.1 dir, and launch command
../launchConfigure.sh --disable-install --enable-sdl-net --disable-nls
5. Watch how ./configure configures, if it fails fix launchConfigure.sh, rinse and repeat.
6. Launch make, and pray. If you're lucky it will create application binary (lbreakout2-2.6.1/client/lbreakout2)
7. Move the application binary to dir project/libs/armeabi, rename it to libapplication.so (overwrite old file)
8. Run command "arm-eabi-strip --strip-debug libapplication.so", you can find arm-eabi-strip under your NDK dir.
9. Run "ant debug" or "ant release" from project dir, install to device & enjoy.
Quick guide to debug native code
================================
To debug your application add tag 'android:debuggable="true"' to 'application' element in AndroidManifest.xml,
recmpile and reinstall your app to Android 2.2 emulator or Android 2.2 device, go to "project" dir and launch command
ndk-gdb --verbose --start --force
then when it fails enter command
target remote:5039 (then it will fail again)
Note that it's extremely buggy, and I had no any success in debugging my app with ndk-gdb.
So it's best to debug with code like:
__android_log_print(ANDROID_LOG_INFO, "My App", "We somehow reached execution point #224");
and then watching "adb logcat" output.
If your application crashed, you should use following steps:
1. Gather the crash report from "adb logcat" - it should contain stack trace, if it does not then you're unlucky,
I/DEBUG ( 51): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG ( 51): Build fingerprint: 'sprint/htc_supersonic/supersonic/supersonic:2.1-update1/ERE27/194487:userdebug/test-keys'
I/DEBUG ( 51): pid: 915, tid: 924 >>> de.schwardtnet.alienblaster <<<
I/DEBUG ( 51): signal 11 (SIGSEGV), fault addr deadbaad
I/DEBUG ( 51): r0 00000000 r1 afe133f1 r2 00000027 r3 00000058
I/DEBUG ( 51): r4 afe3ae08 r5 00000000 r6 00000000 r7 70477020
I/DEBUG ( 51): r8 000000b0 r9 ffffff20 10 48552868 fp 00000234
I/DEBUG ( 51): ip 00002ee4 sp 485527f8 lr deadbaad pc afe10aac cpsr 60000030
I/DEBUG ( 51): #00 pc 00010aac /system/lib/libc.so
I/DEBUG ( 51): #01 pc 0000c00e /system/lib/libc.so
I/DEBUG ( 51): #02 pc 0000c0a4 /system/lib/libc.so
I/DEBUG ( 51): #03 pc 0002ca00 /data/data/de.schwardtnet.alienblaster/lib/libsdl.so
I/DEBUG ( 51): #04 pc 00028b6e /data/data/de.schwardtnet.alienblaster/lib/libsdl.so
I/DEBUG ( 51): #05 pc 0002d080 /data/data/de.schwardtnet.alienblaster/lib/libsdl.so
2. Go to project/bin/ndk/local/armeabi dir, find there the library mentioned in stacktrace
(libsdl.so in our example), copy the address of the first line of stacktrace (0002ca00), and execute command
gdb libsdl.so -ex "list *0x0002ca00"
It will output the exact line in your source where the application crashed.
Known bugs
==========
0. Revert to widely-used SDL 1.2, backport changes that enable hardware acceleration from SDL 1.3
Ideally ChangeAppSettings.sh should ask you what SDL version you want to use.
1. Application will crash on exit or when you're pressing "Home" button - the correct behavior for Android apps
is to stay in memory and go to foreground when you're launching app again, that's not working yet because
app will lose OpenGL context (there are rumors that it won't lose GL context in 2.1 SDK).
2. Multitouch support - it is available since 2.0 SDK, but not on 1.6 - I'll have to follow
http://devtcg.blogspot.com/2009/12/gracefully-supporting-multiple-android.html to make it compile.
3. In the future I'm planning to use accelerometer as a SDL joystick.
4. Many SDL games require keyboard, and newer phones have only touchscreen - there should be configuration screen
where you can toggle on-screen keyboard, bind existing keys like volume up/down to PgUp/PgDown for example,
and configure other actions like accelerometer tilt as keypresses.
5. Export phone vibrator to SDL - interface is available in SDL 1.3
Games to port
=============
Ur-Quan Masters (epic game, must have)
LBreakout2
Commander Genius (only data files for shareware version available for free)
OpenJazz (only data files for shareware version available for free)
OpenLieroX (will be damn hard to do, I wrote the code partially)
TeeWorlds (only if they have nice clean code)
AdvanceMAME (they already have their own port, yet it's unfinished)
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