lcd触摸拖动的c语言代码实现

以下是一个基本的LCD触摸拖动的C语言代码实现：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/input.h>
#include <linux/fb.h>
#include <sys/mman.h>

#define FBDEVNAME "/dev/fb0"
#define EVENTNAME "/dev/input/event0"

int main(void)
{
    int fbfd;
    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;
    char *fbp = 0;
    int x, y, dx, dy;
    int prev_x = 0, prev_y = 0, curr_x = 0, curr_y = 0;
    int touch_down = 0, touch_up = 1;

    int evfd;
    struct input_event ev;

    fbfd = open(FBDEVNAME, O_RDWR);
    if (!fbfd) {
        printf("Error: cannot open framebuffer device.\n");
        exit(1);
    }

    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
        printf("Error: reading fixed information.\n");
        exit(2);
    }

    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
        printf("Error: reading variable information.\n");
        exit(3);
    }

    fbp = (char *)mmap(0, finfo.smem_len, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
    if ((int)fbp == -1) {
        printf("Error: failed to map framebuffer device to memory.\n");
        exit(4);
    }

    evfd = open(EVENTNAME, O_RDONLY);
    if (!evfd) {
        printf("Error: cannot open input device.\n");
        exit(1);
    }

    while (1) {
        if (read(evfd, &ev, sizeof(struct input_event)) < sizeof(struct input_event)) {
            printf("Error: failed to read input event.\n");
            exit(1);
        }

        if (ev.type == EV_ABS) {
            if (ev.code == ABS_X) {
                curr_x = ev.value;
            } else if (ev.code == ABS_Y) {
                curr_y = ev.value;
            } else if (ev.code == ABS_MT_POSITION_X) {
                curr_x = ev.value;
            } else if (ev.code == ABS_MT_POSITION_Y) {
                curr_y = ev.value;
            } else if (ev.code == ABS_MT_TRACKING_ID) {
                if (ev.value == -1) {
                    touch_down = 0;
                    touch_up = 1;
                } else {
                    touch_down = 1;
                    touch_up = 0;
                }
            }
        } else if (ev.type == EV_SYN && touch_down && !touch_up) {
            dx = curr_x - prev_x;
            dy = curr_y - prev_y;

            x += dx;
            y += dy;

            if (x < 0) {
                x = 0;
            }
            if (x > vinfo.xres - 1) {
                x = vinfo.xres - 1;
            }
            if (y < 0) {
                y = 0;
            }
            if (y > vinfo.yres - 1) {
                y = vinfo.yres - 1;
            }

            *((unsigned short*)(fbp + (x + y * vinfo.xres) * 2)) = 0xFFFF;

            prev_x = curr_x;
            prev_y = curr_y;
        }
    }

    munmap(fbp, finfo.smem_len);
    close(fbfd);
    close(evfd);

    return 0;
}

该代码使用了Linux的输入系统和帧缓冲系统来实现LCD触摸拖动功能。它使用了evdev驱动程序来读取触摸屏幕输入事件，并将触摸坐标映射到帧缓冲内存中的像素坐标。最后，它在指定的像素坐标处绘制了一个白色的像素点。