SDL2.0上手试用

原创

拳四郎 2013-11-09 17:02:00 ©著作权

文章分类 Android 移动开发

©著作权归作者所有：来自51CTO博客作者拳四郎的原创作品，请联系作者获取转载授权，否则将追究法律责任

前言

个人喜好原因，写OpenGL的程序都喜欢用SDL做框架，没有Qt那么臃肿，也没有glut那么坑跌,在不失灵活性的情况下保持了自己的轻量。SDL2.0在今年很早的时候时候就发布了，几天就来好好试用一下。

下面是SDL2主要的几点新特性：

全硬件加速
支持OpenGL3.0+
支持OpenGL ES
支持Android和iOS

跨平台支持Windows，MacOSX和LInux

修改了很多bug

...

编译安装

从官网下载最新版2.0.1的源码，解压后cd进目录，依次执行：

./autogen

./configura

make

sudu make install

一切顺利的话SDL2.0就安装编译好了。

库文件在 /usr/local/lib中

头文件在 /usr/local/include/SDL2 中。

加载显示一张图片

感觉SDL的1.2和2.0差别还是挺大的。看代码：

#include <iostream> #include <SDL2/SDL.h>   #include <GL/gl.h>   #include <GL/glu.h>   using namespace std; int main() {  	//Start SDL       if (SDL_Init(SDL_INIT_VIDEO) != 0)     { 		cout << "SDL_Init Error: " << SDL_GetError() << endl; 		return 1; 	} 	 	SDL_Window *win = SDL_CreateWindow("Hello World!", 100, 100, 871, 564, SDL_WINDOW_SHOWN); 	if (win == nullptr) 	{ 		cout << "SDL_CreateWindow Error: " << SDL_GetError() << endl; 		return 1; 	} 	 	SDL_Renderer *ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC); 	if (ren == nullptr) 	{ 		cout << "SDL_CreateRenderer Error: " << SDL_GetError() << endl; 		return 1; 	} 	 	SDL_Surface *bmp = SDL_LoadBMP("girl.bmp"); 	if (bmp == nullptr) 	{ 		cout << "SDL_LoadBMP Error: " << SDL_GetError() << endl; 		return 1; 	} 	 	SDL_Texture *tex = SDL_CreateTextureFromSurface(ren, bmp); 	SDL_FreeSurface(bmp); 	if (tex == nullptr) 	{ 		cout << "SDL_CreateTextureFromSurface Error: " << SDL_GetError() << endl; 		return 1; 	} 	 	SDL_RenderClear(ren); 	SDL_RenderCopy(ren, tex, NULL, NULL); 	SDL_RenderPresent(ren); 	 	SDL_Delay(2000); 	 	SDL_DestroyTexture(tex); 	SDL_DestroyRenderer(ren); 	SDL_DestroyWindow(win);     //Quit SDL           SDL_Quit();  	cout<<"Hello"<<endl; 	return 1; }

代码还是蛮简单的，先是初始化SDL，再依次初始化Window ->初始化Render ->加载图片 -> 生成纹理 ->渲染纹理 ->释放内存，记得在当前目录放一张 girl.bmp.运行结果：

基于SDL2的OpenGL编程

相对于SDL1.2中的函数接口，SDL2改变得还是比较大的，其中的设计得会更加“现代化”一些，用起来会更加方便，以前用过SDL1.2的需要重新熟悉一下。

#include <iostream> #include <SDL2/SDL.h>   #include <GL/gl.h>   #include <GL/glu.h>   using namespace std;  const int SCREEN_WIDTH = 800;   const int SCREEN_HEIGHT =600;  SDL_Window *mainwindow; /* Our window handle */ SDL_GLContext maincontext; /* Our opengl context handle */  /* A simple function that prints a message, the error code returned by SDL,  * and quits the application */ void sdldie(const char *msg) {     printf("%s: %s\n", msg, SDL_GetError());     SDL_Quit();     exit(1); }  void quit( int code )   {       SDL_Quit( );       /* Exit program. */       exit( code );   }    void checkSDLError(int line = -1) { #ifndef NDEBUG         const char *error = SDL_GetError();         if (*error != '\0')         {                 printf("SDL Error: %s\n", error);                 if (line != -1)                         printf(" + line: %i\n", line);                 SDL_ClearError();         } #endif }  void initGL( int width, int height )   {       float ratio = (float) width / (float) height;       // Our shading model--Gouraud (smooth).       glShadeModel( GL_SMOOTH );       // Set the clear color.       glClearColor( 0, 0, 0, 0 );       // Setup our viewport.       glViewport( 0, 0, width, height );       //Change to the projection matrix and set our viewing volume.       glMatrixMode( GL_PROJECTION );       glLoadIdentity();       gluPerspective( 60.0, ratio, 1.0, 100.0 );   }    void initSDL() { 	if (SDL_Init(SDL_INIT_VIDEO) < 0) /* Initialize SDL's Video subsystem */         sdldie("Unable to initialize SDL"); /* Or die on error */       /* Request opengl 3.2 context.      * SDL doesn't have the ability to choose which profile at this time of writing,      * but it should default to the core profile */     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);       /* Turn on double buffering with a 24bit Z buffer.      * You may need to change this to 16 or 32 for your system */     SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);     SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);       /* Create our window centered at 512x512 resolution */     mainwindow = SDL_CreateWindow("OpenGL in SDL2", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,         SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN|SDL_WINDOW_RESIZABLE);     if (!mainwindow) /* Die if creation failed */         sdldie("Unable to create window");       checkSDLError(__LINE__);       /* Create our opengl context and attach it to our window */     maincontext = SDL_GL_CreateContext(mainwindow);     checkSDLError(__LINE__);       /* This makes our buffer swap syncronized with the monitor's vertical refresh */     SDL_GL_SetSwapInterval(1); }  void renderGL() { 	 // Clear the color and depth buffers.       glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );       // We don't want to modify the projection matrix. */       glMatrixMode( GL_MODELVIEW );       glLoadIdentity( );       // Move down the z-axis.       glTranslatef( 0.0, 0.0, -5.0 );       //Draw a square       glBegin(GL_QUADS);       glColor3f(1.0f,0.0f,0.0f);       glVertex3f(-1.0f  , -1.0f  ,  1.0f  );       glColor3f(0.0f,1.0f,0.0f);       glVertex3f( 1.0f  , -1.0f  ,  1.0f  );       glColor3f(0.0f,0.0f,1.0f);       glVertex3f( 1.0f  ,  1.0f  ,  1.0f  );       glColor3f(1.0f,1.0f,0.0f);       glVertex3f(-1.0f  ,  1.0f  ,  1.0f  );       glEnd();       SDL_GL_SwapWindow(mainwindow); }  void resizeGL(int width,int height)   {       if ( height == 0 )       {           height = 1;       }       //Reset View       glViewport( 0, 0, (GLint)width, (GLint)height );       //Choose the Matrix mode       glMatrixMode( GL_PROJECTION );       //reset projection       glLoadIdentity();       //set perspection       gluPerspective( 45.0, (GLfloat)width/(GLfloat)height, 0.1, 100.0 );       //choose Matrix mode       glMatrixMode( GL_MODELVIEW );       glLoadIdentity();        }    void handleKeyEvent( SDL_Keysym* keysym )   {       switch( keysym->sym )       {       case SDLK_ESCAPE:           quit( 0 );           break;       case SDLK_SPACE:        cout<<"Space"<<endl;         break;       default:           break;       }   }   void handleEvents()   {       // Our SDL event placeholder.       SDL_Event event;       //Grab all the events off the queue.       while( SDL_PollEvent( &event ) ) {           switch( event.type ) {           case SDL_KEYDOWN:               // Handle key Event               handleKeyEvent( &event.key.keysym );               break;           case SDL_QUIT:               // Handle quit requests (like Ctrl-c).               quit( 0 );               break;           case SDL_WINDOWEVENT:         		if(event.window.event == SDL_WINDOWEVENT_RESIZED)         	{             	if ( mainwindow )               	{               		int tmpX,tmpY;             		SDL_GetWindowSize(mainwindow,&tmpX,&tmpY);                 	resizeGL(tmpX, tmpY);                 	 	             	}           	}         	SDL_GL_SwapWindow(mainwindow);             break;           }       }   }   /* Our program's entry point */ int main(int argc, char *argv[]) {  	initSDL(); 	initGL(SCREEN_WIDTH, SCREEN_HEIGHT); 	renderGL( );   	while(true) 	{ 		/* Process incoming events. */           handleEvents( );           /*Render scene*/         renderGL();  	}       return 0; }

需要说明的时候__LINE__这个宏，它主要是用来调试的，表示当前的代码行数，

用下面的命令来编译：

g++ test.cpp -o test -lSDL2 -lGL -lGLU -std=c++11

运行结果：

编译运行Android中的SDL2

注：最好在Ubuntu 下来进行交叉编译，测试过Opensuse，未果。

在SDL的源码文件夹中有相应的android工程模板 android-project.

首先是交叉编译。

1.创建android-project/jni/SDL文件夹

2.将SDL源码目录下的src 和include文件夹还有Android.mk拷贝到刚才创建的目录

3.在 android-project/jni/src 中创建main.c

这里从手机里面加载一张图片来显示。

#include "SDL.h"  int main(int argc, char* argv[]) {  	//Start SDL       if (SDL_Init(SDL_INIT_VIDEO) != 0)     { 		return 1; 	} 	 	SDL_Window *win = SDL_CreateWindow("Hello World!", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 512, 512, SDL_WINDOW_SHOWN);  	 	SDL_Renderer *ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC);  	 	SDL_Surface *bmp = SDL_LoadBMP("/sdcard/boss.bmp");  	 	SDL_Texture *tex = SDL_CreateTextureFromSurface(ren, bmp); 	SDL_FreeSurface(bmp); 	 	SDL_RenderClear(ren); 	SDL_RenderCopy(ren, tex, NULL, NULL); 	SDL_RenderPresent(ren); 	 	SDL_Delay(2000); 	 	SDL_DestroyTexture(tex); 	SDL_DestroyRenderer(ren); 	SDL_DestroyWindow(win); 	     //Quit SDL       SDL_Quit();  	return 1; }

修改src/Android.mk文件，将YourSourceHere.c改为main.c.

4.在手机的sdcard根目录下面放一个boss.bmp,待会加载。

5.终端cd进android-project，执行

$NDK_ROOT/ndk-build

编译正常的话可以得到下面的结果：