SDL

SDL（original form lazy foo)

一些问题

1.ubuntu下，对于 lesson1：hello_SDL,如果使用命令行安装SDL编译程序时可能报错：no available video device，需去官网下载tar文件手动安装
2.ubuntu下，对于lesson6：Extension Libraries and Loading Other Image Formats，如果下载tar文件手动安装后，运行程序报错：没有找到共享库，试试用命令行下载安装

1.hello_SDL

#include <SDL.h>
#include <stdio.h>
const int SCREEN_WIDTH = 640;//宽度
const int SCREEN_HEIGHT = 480;//高度
int main( int argc, char* args[] )
{
    SDL_Window* window = NULL;//将要render的 window
    SDL_Surface* screenSurface = NULL;//window中包含的surface
    SDL_Init( SDL_INIT_VIDEO );//初始化SDL
    window = SDL_CreateWindow( "fuck you", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN );//创建windows，参数列表：窗口名称，窗口位置，窗口大小，flag（具体初看SDL wiki）
    screenSurface = SDL_GetWindowSurface( window );//获取window surface
    SDL_FillRect( screenSurface, NULL, SDL_MapRGB( screenSurface->format, 0xFF, 0xFF, 0xFF ) );//把surface填充为白色
    SDL_UpdateWindowSurface( window );//update the surface
    SDL_Delay( 2000 );
    SDL_DestroyWindow( window );
    SDL_Quit();//quit SDL system
    return 0;
}

2.get an image on the screen

#include<SDL.h>
#include<cstdio>
const int HEIGHT=460;
const int WIDTH=640;
void init();
void loadimage();
void close();
SDL_Window* window=NULL;
SDL_Surface* surface=NULL;
SDL_Surface* image=NULL;
void init()//初始化，创建窗口，获取surface
{
    SDL_Init(SDL_INIT_VIDEO);
    window=SDL_CreateWindow("fuck you",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,WIDTH,HEIGHT,SDL_WINDOW_SHOWN);
    surface=SDL_GetWindowSurface(window);
}
void loadimage()//load .bmp image
{
    image=SDL_LoadBMP("hello_world.bmp");
}
void close()
{
    SDL_FreeSurface(image);//释放image的内存
    image=NULL;
    SDL_DestroyWindow(window);//同时也释放了surface
    window=NULL;
    SDL_Quit();
}
int main(int argc,char* argv[])
{
    init();
    loadimage();
    SDL_BlitSurface(image,NULL,surface,NULL);//NULL：覆盖整个表面
    SDL_UpdateWindowSurface(window);//This is the function you use to reflect any changes to the surface on the screen.     
    SDL_Delay(2000);
    close();
    return 0;
}

3.event driven programme

#include<SDL.h>
#include<cstdio>
const int HEIGHT=460;
const int WIDTH=640;
void init();
void loadimage();
void close();
SDL_Window* window=NULL;
SDL_Surface* surface=NULL;
SDL_Surface* image=NULL;
void init()
{
    SDL_Init(SDL_INIT_VIDEO);
    window=SDL_CreateWindow("fuck you",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,WIDTH,HEIGHT,SDL_WINDOW_SHOWN);
    surface=SDL_GetWindowSurface(window);
}
void loadimage()
{
    image=SDL_LoadBMP("hello_world.bmp");
}
void close()
{
    SDL_FreeSurface(image);
    image=NULL;
    SDL_DestroyWindow(window);
    window=NULL;
    SDL_Quit();
}
int main(int argc,char* argv[])
{
    init();
    loadimage();
    SDL_BlitSurface(image,NULL,surface,NULL);
    SDL_UpdateWindowSurface(window);    
    SDL_Delay(2000);
//===================================
    bool quit=false;
    SDL_Event e;
    while(!quit)
    {
        while(SDL_PollEvent(&e) != 0)/* poll for currently pending events,如果事件（Event队列中没有任何事件则返回0，如果有则返回true（Returns 1 if there is a pending event or 0 if there are none available. ）*/
        {
            if(e.type == SDL_QUIT){
                quit=true;}
        }
    }
//========================================================
    close();
    return 0;
}

4.KEY PRESSES

#include<iostream>
#include<SDL.h>
#include<string>
const int WIDTH=640;
const int HEIGHT=480;
enum key_presses
{
    KEY_PRESS_DEFUALT,
    KEY_PRESS_UP,
    KEY_PRESS_DOWN,
    KEY_PRESS_LEFT,
    KEY_PRESS_RIGHT,
    KEY_PRESS_TOTAL,
};
bool init();
bool load_image();
bool close();
SDL_Window* window=NULL;
SDL_Surface* window_surface=NULL;
SDL_Surface* new_surface=NULL;
SDL_Surface* all_surface[KEY_PRESS_TOTAL];
bool init()
{
    bool success=true;
    SDL_Init(SDL_INIT_VIDEO);
    window=SDL_CreateWindow("fuck you",SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,WIDTH,HEIGHT,SDL_WINDOW_SHOWN);
    window_surface=SDL_GetWindowSurface(window);
    if(
        window==NULL ||
        window_surface==NULL){
            std::cout << "failed to initialize";
            success=false;}
    return success;
}
bool loadimage()
{
    bool success=true;
    all_surface[KEY_PRESS_DEFUALT]=SDL_LoadBMP("press.bmp");
    all_surface[KEY_PRESS_UP]=SDL_LoadBMP("up.bmp");
    all_surface[KEY_PRESS_DOWN]=SDL_LoadBMP("down.bmp");
    all_surface[KEY_PRESS_LEFT]=SDL_LoadBMP("left.bmp");
    all_surface[KEY_PRESS_RIGHT]=SDL_LoadBMP("right.bmp");
    for(int i=0;i<=4;i++)
    {
        if(all_surface[i]==NULL)
            success=false;
    }
    return success;
}
bool close()
{
     bool success=true;
    for(int i=0;i<+4;i++)
    {
        SDL_FreeSurface(all_surface[i]);            
        all_surface[i]=NULL;
    }
    SDL_DestroyWindow(window);
    window=NULL;
    if(window != NULL)
        success=false;
    return true;
}
int main(int argc,char* argv[])
{
    init();
    loadimage();
    SDL_Event e;
    bool quit=false;
    new_surface=all_surface[KEY_PRESS_DEFUALT];
    while(!quit)
    {
        while(SDL_PollEvent(&e) != 0)
        {
            if(e.type==SDL_QUIT){
                quit=true;}
            else if(e.type==SDL_KEYDOWN)
            {
                switch(e.key.keysym.sym)
                {
                case(SDLK_UP):
                    new_surface=all_surface[KEY_PRESS_UP];
                    break;
                case(SDLK_DOWN):
                    new_surface=all_surface[KEY_PRESS_DOWN];
                    break;
                case(SDLK_LEFT):
                    new_surface=all_surface[KEY_PRESS_LEFT];
                    break;
                case(SDLK_RIGHT):
                    new_surface=all_surface[KEY_PRESS_RIGHT];
                    break;
                default:
                    new_surface=all_surface[KEY_PRESS_DEFUALT];
                    break;
                }
            }
        }
        SDL_BlitSurface(new_surface,NULL,window_surface,NULL);
        SDL_UpdateWindowSurface(window);
    }
    close();
    return 0;
}

5.Optimized Surface Loading and Soft Stretching

optimizedSurface = SDL_ConvertSurface( loadedSurface, gScreenSurface->format, NULL );
//参看SDL wiki和 lazy foo's productions

//Apply the image stretched
                SDL_Rect stretchRect;
                stretchRect.x = 0;
                stretchRect.y = 0;
                stretchRect.w = SCREEN_WIDTH;
                stretchRect.h = SCREEN_HEIGHT;
                SDL_BlitScaled( gStretchedSurface, NULL, gScreenSurface, &stretchRect );

后来测试了一下直接SDL_BlitScaled(...,NULL,...,NULL)就够了，其他什么都不用

6.略

7.Texture Loading and Rendering

SDL_Texture ： A structure that contains an efficient, driver-specific representation of pixel data. 
SDL_Renderer ： A structure that contains a rendering state. 

 When we deal with SDL textures you need an SDL_Renderer to render it to the screen

 SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) : 参看SDL wiki
 SDL_CreateRenderer( gWindow, -1, SDL_RENDERER_ACCELERATED ) ： 参看SDL wiki
 SDL_SetRenderDrawColor( gRenderer, 0xFF, 0xFF, 0xFF, 0xFF ) ： Use this function to set the color used for drawing operations (Rect, Line and Clear). 



 SDL_Surface* loadedSurface = IMG_Load( path.c_str() );
 newTexture = SDL_CreateTextureFromSurface( gRenderer, loadedSurface ) ：

                //Clear screen
                SDL_RenderClear( gRenderer );
                //Render texture to screen
                SDL_RenderCopy( gRenderer, gTexture, NULL, NULL );
                //Update screen
                SDL_RenderPresent( gRenderer );