Manpages - ts_read_mt.3

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

  #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);

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.

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.

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);
                          }
                  }
          }
  }

*ts_setup*(3), *ts_config*(3), *ts_open*(3), *ts_close*(3), *ts.conf*(5)