TS_READ

Section: tslib (3)
Updated:
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NAME

ts_read, ts_read_raw, ts_read_mt, ts_read_raw_mt - read tslib touch samples

SYNOPSIS

#include <tslib.h>

int ts_read(struct tsdev *dev, struct ts_sample *samp, int nr);

int ts_read_raw(struct tsdev *dev, struct ts_sample *samp, int nr);

int ts_read_mt(struct tsdev *dev, struct ts_sample_mt **samp, int slots, int nr);

int ts_read_raw_mt(struct tsdev *dev, struct ts_sample_mt **samp, int slots, int nr);

DESCRIPTION

ts_read() reads nr input samples with tslib's filters applied. struct ts_sample is define as follows:

struct ts_sample {
        int             x;
        int             y;
        unsigned int    pressure;
        struct timeval  tv;
};

ts_read_mt() reads nr * slots input samples with tslib's filters applied. struct ts_sample_mt is defined as follows:

struct ts_sample_mt {
        /* most recent ABS_MT_* event codes.
         * see linux/input.h for descriptions */
        int             x;
        int             y;
        unsigned int    pressure;
        int             slot;
        int             tracking_id;

        int             tool_type;
        int             tool_x;
        int             tool_y;
        unsigned int    touch_major;
        unsigned int    width_major;
        unsigned int    touch_minor;
        unsigned int    width_minor;
        int             orientation;
        int             distance;
        int             blob_id;

        struct timeval  tv;

        /* BTN_TOUCH state */
        short           pen_down;

        /* the TSLIB_MT_VALID bit is set in valid if this sample
         * contains new data;
         * valid is set to 0 otherwise */
        short           valid;
};

The user has to provide the amount of memory described in nr and slots to hold them.

ts_read_raw() and ts_read_raw_mt() do the same thing without tslib's filters applied.

RETURN VALUE

The number of actually read samples is returned. Especially when opened in non-blocking mode, see ts_setup() , that can be less than requested in the call. On failure, a negative error number is returned.

EXAMPLE

The following program continuously reads tslib multitouch input samples and prints slot and position values to stdout as the touch screen is touched.

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>

#include <tslib.h>

#define READ_SAMPLES 1
#define MAX_SLOTS 5

int main(int argc, char **argv)
{
        struct tsdev *ts;
        struct ts_sample_mt **samp_mt = NULL;
        int i, j;
        int ret;

        ts = ts_setup(NULL, 0);
        if (!ts)
                return -1;

        samp_mt = malloc(READ_SAMPLES * sizeof(struct ts_sample_mt **));
        if (!samp_mt)
                return -1;

        for (i = 0; i < READ_SAMPLES; i++) {
                samp_mt[i] = calloc(MAX_SLOTS, sizeof(struct ts_sample_mt));
                if (!samp_mt[i])
                        return -1;
        }

        while(1) {
                ret = ts_read_mt(ts, samp_mt, MAX_SLOTS, READ_SAMPLES);
                for (i = 0; i < ret; i++) {
                        printf("sample nr %d, i);
                        for (j = 0; i < MAX_SLOTS; j++) {
                                if (!(samp_mt[i][j].valid & TSLIB_MT_VALID))
                                        continue;

                                printf("slot %d: X:%d Y: %d,
                                       samp_mt[i][j].slot,
                                       samp_mt[i][j].x,
                                       samp_mt[i][j].y);
                        }
                }
        }
}