FunKey S >> C/C++

Screen Tearing

---

main.c

#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <time.h>
  
#define FB_SIZE (240 * 240 * 2)
  
static int fb_dev = -1;
static uint16_t *fb_mem = NULL;
struct fb_var_screeninfo vinfo={0};
  
static int fb_init(void)
{
    fb_dev = open("/dev/fb0", O_RDWR);
    if (fb_dev < 0) {
        printf("failed to open /dev/fb0\n");
        return -1;
    }
  
    if (ioctl(fb_dev, FBIOGET_VSCREENINFO, &vinfo) < 0) {
        close(fb_dev);
        printf("failed to ioctl /dev/fb0\n");
        return -1;
    }
    
    fb_mem = (uint16_t *)mmap(NULL, FB_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fb_dev, 0);
    if (fb_mem == (void *)-1) {
        close(fb_dev);
        printf("failed to mmap /dev/fb0\n");
        return -1;
    }
    memset(fb_mem, 0 , FB_SIZE);
    return 0;
}
  
static int fb_uninit(void)
{
    munmap(fb_mem, FB_SIZE);
    fb_mem = NULL;
  
    close(fb_dev);
    fb_dev = -1;
    return 0;
}
  
int main(int argc, char **argv)
{
    int x = 0, y = 0;
    uint16_t *p = NULL, cc = 0, ret = 0;
    uint16_t col[] = {0xf800, 0x07e0, 0x001f};
  
    fb_init();
    while (1) {
        p = fb_mem;
        for (y = 0; y < 240; y++) {
            for (x = 0; x < 240; x++) {
                *p++= col[cc % 3];
            }
        }
        usleep(1000000 / 60);
        cc += 1;
    }
    fb_uninit();
    return 0;
}

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