移植SDL到android

参考：http://blog.youkuaiyun.com/banyao2006/archive/2011/01/10/6126247.aspx

环境：
- Cygwin 1.7
- Android NDK：android-ndk-r4b-windows
- SDL：1.2.14

1.下载SDL 1.2.14，将其解压到ndk的samples目录，并将文件夹改为SDL。
   那么源码的位置是：/home/Administrator/android-ndk-r4b-windows/android-ndk-r4b/samples/SDL
2 .修改SDL中的Makefile.minimal，内容如下：

# Makefile to build the SDL library
PREBUILT = /home/Administrator/android-ndk-r4b-windows/android-ndk-r4b/build/prebuilt/windows/arm-eabi-4.4.0
INCLUDE = -I./include  -I/home/Administrator/android-ndk-r4b-windows/android-ndk-r4b/build/platforms/android-8/arch-arm/usr/include -I/usr/include
CFLAGS  = -g -O2 $(INCLUDE)
CC  = $(PREBUILT)/bin/arm-eabi-gcc
AR  = $(PREBUILT)/bin/arm-eabi-ar
RANLIB  = $(PREBUILT)/bin/arm-eabi-ranlib

CONFIG_H = include/SDL_config.h
TARGET  = libSDL.a
SOURCES = src/*.c src/audio/*.c src/cdrom/*.c  src/cpuinfo/*.c src/events/*.c src/file/*.c src/joystick/*.c src/stdlib/*.c src/thread/*.c src/timer/*.c src/video/*.c src/audio/dsp/*.c src/audio/dma/*.c src/video/fbcon/*.c src/joystick/dummy/*.c src/cdrom/dummy/*.c  src/thread/generic/*.c src/timer/unix/*.c src/loadso/dummy/*.c \

OBJECTS = $(shell echo $(SOURCES) | sed -e 's,\.c,\.o,g')
all: $(TARGET)
$(TARGET): $(CONFIG_H) $(OBJECTS)
    $(AR) crv $@ $^
    $(RANLIB) $@
$(CONFIG_H):
    cp $(CONFIG_H).default $(CONFIG_H)
clean:
    rm -f $(TARGET) $(OBJECTS)

3.修改SDL/include/SDL_config_minimal.h，内容如下：

#ifndef _SDL_config_minimal_h
#define _SDL_config_minimal_h

#include "SDL_platform.h"

/* This is the minimal configuration that can be used to build SDL */

#include <stdarg.h>
/*
typedef signed char int8_t;
typedef unsigned char uint8_t;
typedef signed short int16_t;
typedef unsigned short uint16_t;
typedef signed int int32_t;
typedef unsigned int uint32_t;
typedef unsigned int size_t;
typedef unsigned long uintptr_t;
*/
#define SDL_AUDIO_DRIVER_OSS    1
#define SDL_CDROM_DISABLED  1
#define SDL_JOYSTICK_DISABLED   1
#define SDL_LOADSO_DISABLED 1
#define SDL_THREADS_DISABLED    1
#define SDL_TIMER_UNIX  1
#define SDL_VIDEO_DRIVER_FBCON  1
#define HAVE_STDIO_H 1
#endif /* _SDL_config_minimal_h */

4.修改SDL_fbvideo.c
  由于Android的framebuffer设备是 /dev/graphics/fb0 (Linux是 /dev/fb0)，所以我们需要修改 ./src/video/fbcon/SDL_fbvideo.c。
  将文件中所有的/dev/fb0全都替换成/dev/graphics/fb0
5.进行编译
  在 Cygwin下進入SDL的根目录，执行：
    make -f Makefile.minimal
  编译成功之后，会产生libSDL.a

编译中可能遇到的问题:
1. compiler认为SDL_dummy_enum的size不合法：

./include/SDL_stdinc.h:151: error: size of array 'SDL_dummy_enum' is negative

 解决办法：將SDL_stdinc.h的151行注释掉：

//SDL_COMPILE_TIME_ASSERT(enum, sizeof(SDL_DUMMY_ENUM) == sizeof(int));

2.重新make的时候，可能会有问题，最好先clean，然后make
3.修改文件之后，要转换成unix格式，要注意换行和空格符'\'。