libspnav example controlling mouse using spaceball (uinput)

Makefile

CFLAGS ?= -O3 -flto

simple_uinput: proto.h spnav_config.h spnav.h proto.c spnav.c simple.c
	$(CC) $(CFLAGS) -o $@ $^

spnav_config.h:
	touch $@

proto.h spnav.h proto.c spnav.c:
	curl -L -O --compressed --url "https://github.com/FreeSpacenav/libspnav/raw/master/src/{proto.c,proto.h,spnav.c,spnav.h}"

.PHONY: clean
clean:
	-rm proto.h spnav.h proto.c spnav.c spnav_config.h simple_uinput

simple.c

/* libspnav uinput example
 * Control mouse using spaceball (X, Z axis) + 2D mouse wheel (RX, RZ axis)
 * based on https://github.com/FreeSpacenav/libspnav/blob/master/examples/simple/simple.c
 */
#include "spnav.h"
#include <linux/input-event-codes.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

#include <fcntl.h>
#include <linux/uinput.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>

static void print_dev_info(void);

static int fd; // uinput fd

static void sig(int s)
{
    spnav_close();
    ioctl(fd, UI_DEV_DESTROY);
    close(fd);
    exit(0);
}

static bool emit(int fd, int type, int code, int val)
{
    struct input_event ie;

    ie.type = type;
    ie.code = code;
    ie.value = val;
    /* timestamp values below are ignored */
    ie.time.tv_sec = 0;
    ie.time.tv_usec = 0;

    return write(fd, &ie, sizeof(ie)) == sizeof(ie);
}

static bool emit_motion(int fd, int x, int y, int wheel, int hwheel)
{
    static struct input_event ie[5] = {
        { .type = EV_REL,
            .code = REL_X },
        { .type = EV_REL,
            .code = REL_Y },
        { .type = EV_REL,
            .code = REL_WHEEL_HI_RES },
        { .type = EV_REL,
            .code = REL_HWHEEL_HI_RES },
        { .type = EV_SYN,
            .code = SYN_REPORT,
            .value = 0 }
    };
    ie[0].value = x;
    ie[1].value = y;
    ie[2].value = wheel;
    ie[3].value = hwheel;

    return write(fd, &ie, sizeof(ie)) == sizeof(ie);
}

int main(void)
{

    struct uinput_setup usetup;
    const int buttons = 12;
    const int button_keys[] = {
        BTN_SIDE, // back // 1
        BTN_FORWARD, // 2
        KEY_F15, // 3
        KEY_F16, // 4
        KEY_F17, // 5
        KEY_F18, // 6
        BTN_LEFT, // 7
        BTN_MIDDLE, // 8
        BTN_RIGHT, // 9
        KEY_F22, // A
        KEY_F23, // B
        KEY_LEFTCTRL // C
    };

    fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK);
    if (fd < 0) {
        perror("Can't open /dev/uinput");
        return 1;
    }

    /* enable button events */
    ioctl(fd, UI_SET_EVBIT, EV_KEY);
    for (int i = 0; i < 12; i++)
        ioctl(fd, UI_SET_KEYBIT, button_keys[i]);

    /* enable motion events */
    ioctl(fd, UI_SET_EVBIT, EV_REL);
    ioctl(fd, UI_SET_RELBIT, REL_X);
    ioctl(fd, UI_SET_RELBIT, REL_Y);
    ioctl(fd, UI_SET_RELBIT, REL_HWHEEL_HI_RES);
    ioctl(fd, UI_SET_RELBIT, REL_WHEEL_HI_RES);

    spnav_event sev;

    signal(SIGINT, sig);

    if (spnav_open() == -1) {
        fprintf(stderr, "failed to connect to spacenavd\n");
        return 1;
    }

    print_dev_info();
    memset(&usetup, 0, sizeof(usetup));
    usetup.id.bustype = BUS_USB;
    usetup.id.vendor = 0x1234; /* sample vendor */
    usetup.id.product = 0x5678; /* sample product */
    spnav_dev_name(usetup.name, sizeof usetup.name);

    spnav_sensitivity(0.25);

    ioctl(fd, UI_DEV_SETUP, &usetup);
    ioctl(fd, UI_DEV_CREATE);

    /* If the spaceball is idle wait for next event. Otherwise poll and emit motioen event every 10ms.
     */
    bool idle = true;
    while (true) {
        int result;
        if (idle)
            result = spnav_wait_event(&sev);
        else // no wait
            result = spnav_poll_event(&sev);

        if (!result) {
            if (idle)
                break;

            // repeat last motion every 10ms (low latency)
            sev.type = SPNAV_EVENT_MOTION;
            for (int i = 0; i < 10 && !result; i++) {
                usleep(1000); // 1ms

                result = spnav_poll_event(&sev);
            }
        }

        if (sev.type == SPNAV_EVENT_MOTION) {
            if (sev.motion.x || sev.motion.z || sev.motion.rx || sev.motion.rz) {
                idle = false;
                if (!emit_motion(fd, sev.motion.x, -sev.motion.z, -sev.motion.rx, sev.motion.rz)) {
                    perror("uinput");
                    break;
                }

            } else {
                idle = true;
            }

        } else if (sev.type == SPNAV_EVENT_BUTTON) {
            printf("got button %s event b(%d)\n",
                sev.button.press ? "press" : "release", sev.button.bnum);
            if (sev.button.bnum < buttons) {
                if (button_keys[sev.button.bnum])
                    emit(fd, EV_KEY, button_keys[sev.button.bnum], sev.button.press);
                if (!emit(fd, EV_SYN, SYN_REPORT, 0)) {
                    perror("uinput");
                    break;
                }
            }
        }
    }

    spnav_close();

    ioctl(fd, UI_DEV_DESTROY);
    close(fd);

    return 0;
}

static void print_dev_info(void)
{
    int proto;
    char buf[256];

    if ((proto = spnav_protocol()) == -1) {
        fprintf(stderr, "failed to query protocol version\n");
        return;
    }
    printf("spacenav AF_UNIX protocol version: %d\n", proto);

    spnav_client_name("simple example");

    if (proto >= 1) {
        spnav_dev_name(buf, sizeof buf);
        printf("Device: %s\n", buf);
        spnav_dev_path(buf, sizeof buf);
        printf("Path: %s\n", buf);
        printf("Buttons: %d\n", spnav_dev_buttons());
        printf("Axes: %d\n", spnav_dev_axes());
    }

    putchar('\n');
}