从C中在Linux上的framebuffer上绘制文本

sudo apt-get install libsdl2-dev

int fbfd = 0;

struct fb_var_screeninfo vinfo;

struct fb_fix_screeninfo finfo;

char *fbp = 0;

long int screensize = 0;

int x = 0, y = 0;

int font_size = 24;

SDL_Window *window;

SDL_Renderer *renderer;

SDL_Texture *texture;

SDL_Surface *surface;

TTF_Font *font;

SDL_Color color = {255, 255, 255};

SDL_Rect dst_rect = {0, 0, 0, 0};

const char *text = "Hello, world!";

// 初始化SDL

if (SDL_Init(SDL_INIT_VIDEO) < 0) {

    printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());

    exit(1);

}

// 初始化TTF

if (TTF_Init() < 0) {

    printf("TTF could not initialize! SDL_Error: %s\n", SDL_GetError());

    exit(1);

}

// 打开framebuffer设备

fbfd = open(FBDEV, O_RDWR);

if (fbfd == -1) {

    perror("Error: cannot open framebuffer device");

    exit(1);

}

// 获取屏幕信息

if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {

    perror("Error reading fixed information");

    exit(1);

}

if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {

    perror("Error reading variable information");

    exit(1);

}

// 计算屏幕大小

screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;

// 映射到用户内存

fbp = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);

if (fbp == (char *)-1) {

    perror("Error: failed to map framebuffer device to memory");

    exit(1);

}

// 创建SDL窗口

window = SDL_CreateWindow("Draw Text on Framebuffer", 0, 0, vinfo.xres, vinfo.yres, SDL_WINDOW_FULLSCREEN_DESKTOP);

if (!window) {

    fprintf(stderr, "SDL_CreateWindow failed: %s\n", SDL_GetError());

    exit(1);

}

// 创建渲染器

renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);

if (!renderer) {

    fprintf(stderr, "SDL_CreateRenderer failed: %s\n", SDL_GetError());

    exit(1);

}

// 加载字体

font = TTF_OpenFont(FONT_PATH, font_size);

if (!font) {

    fprintf(stderr, "TTF_OpenFont failed: %s\n", TTF_GetError());

    exit(1);

}

// 创建文本纹理

surface = TTF_RenderText_Blended(font, text, color);

if (!surface) {

    fprintf(stderr, "TTF_RenderText_Blended failed: %s\n", TTF_GetError());

    exit(1);

}

// 创建纹理

texture = SDL_CreateTextureFromSurface(renderer, surface);

if (!texture) {

    fprintf(stderr, "SDL_CreateTextureFromSurface failed: %s\n", SDL_GetError());

    exit(1);

}

// 设置绘制位置

dst_rect.x = x;

dst_rect.y = y;

dst_rect.w = surface->w;

dst_rect.h = surface->h;

// 清除屏幕

SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);

SDL_RenderClear(renderer);

// 绘制文本

SDL_RenderCopy(renderer, texture, NULL, &dst_rect);

SDL_RenderPresent(renderer);

// 等待用户退出

SDL_Event event;

while (1) {

    if (SDL_PollEvent(&event)) {

        if (event.type == SDL_QUIT) {

            break;

        }

    }

}

// 释放资源

SDL_DestroyTexture(texture);

SDL_FreeSurface(surface);

TTF_CloseFont(font);

SDL_DestroyRenderer(renderer);

SDL_DestroyWindow(window);

TTF_Quit();

SDL_Quit();

munmap(fbp, screensize);

close(fbfd