SDL学习笔记7--用SDL显示图像数据

这篇文章实际和学习笔记3和4差不多，未来需要深入理解window, render, texture, surface等概念。

#include "SDL.h"

struct
{
    Uint32  pixformat;
    int     w, h;
    Uint8   *data;
}frame;

int screen_width  = 0;
int screen_height = 0;
int status = 0; // 1: request to stop; 2: stop
SDL_Texture *p_texture = NULL;
SDL_Renderer *p_render = NULL;

static void quit(int rc)
{
    SDL_Quit();
    exit(rc);
}

void fill_color_rgba8888()
{
    static Uint8 r = 0, g = 0, b = 0, a = 0;

    r += 10, g += 15, b += 20, a += 5;

    Uint32 *pdst = (Uint32 *)frame.data;
    Uint32 color = (r << 24) | (g << 16) | (b << 8) | a;
    for (int i = 0; i < frame.w*frame.h; i++)
    {
        *pdst++ = color;
    }
}

int SDLCALL video_process(void * data)
{
    int ret; 
    while (1)
    {
        if (1 == status)    // request to stop
        {
            status = 2;
            break;
        }
        fill_color_rgba8888();

        ret = SDL_UpdateTexture(p_texture, NULL, frame.data, frame.w * 4);
        ret = SDL_RenderClear(p_render);
        SDL_RenderCopy(p_render, p_texture, NULL, NULL);
        SDL_RenderPresent(p_render);

        SDL_Delay(1000);
    }

    return 0;
}

int video_test()
{

    // 1. init
    if (SDL_Init(SDL_INIT_VIDEO) < 0)
    {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize SDL Timer SubSystem: %s\n", SDL_GetError());
        quit(1);
    }

    screen_width = screen_height = 500;
    frame.w = frame.h = 300;
    frame.pixformat = SDL_PIXELFORMAT_RGBA8888;
    frame.data = (Uint8 *)calloc(frame.w*frame.h*4, 1); // 4: pixsize

    SDL_Window *p_screen;
    p_screen = SDL_CreateWindow("video test",SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
        screen_width, screen_height, SDL_WINDOW_RESIZABLE);
    if (NULL == p_screen)
    {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create window: %s\n", SDL_GetError());
        quit(2);
    }

    p_render = SDL_CreateRenderer(p_screen, -1, 0);
    if (NULL == p_render)
    {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create renderer: %s\n", SDL_GetError());
        quit(3);
    }
    
    p_texture = SDL_CreateTexture(p_render, frame.pixformat, SDL_TEXTUREACCESS_STREAMING, frame.w, frame.h);
    if (NULL == p_texture)
    {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create texture: %s\n", SDL_GetError());
        quit(4);
    }

    // 2. disp
    SDL_Thread *video_thread = SDL_CreateThread(video_process, NULL, NULL);

    // 3. event loop
    SDL_Event event;
    while (status != 2)
    {
        SDL_WaitEvent(&event);
        switch (event.type)
        {
        case SDL_QUIT:
            status = 1;
            break;
        }
    }
    
    // 4. exit
    SDL_DestroyTexture(p_texture);
    SDL_DestroyRenderer(p_render);
    SDL_DestroyWindow(p_screen);
    free(frame.data);
    SDL_Quit();

    return 0;
}