Pebble on-screen accelerometer data display

accel-display.c

#include <pebble.h>

static Window *window;
static TextLayer *x_accel_layer, *y_accel_layer, *z_accel_layer;

static char accel_layer_text[3][15];

static void process_accel_data(AccelData *data, uint32_t num_samples)
{
  memset(accel_layer_text, 0, sizeof(accel_layer_text));
  snprintf(accel_layer_text[0], 14, "X: %4d", data[num_samples - 1].x);
  snprintf(accel_layer_text[1], 14, "Y: %4d", data[num_samples - 1].y);
  snprintf(accel_layer_text[2], 14, "Z: %4d", data[num_samples - 1].z);

  text_layer_set_text(x_accel_layer, accel_layer_text[0]);
  text_layer_set_text(y_accel_layer, accel_layer_text[1]);
  text_layer_set_text(z_accel_layer, accel_layer_text[2]);
}

static void window_load(Window *window) {
  Layer *window_layer = window_get_root_layer(window);
  GRect bounds = layer_get_bounds(window_layer);

  x_accel_layer = text_layer_create((GRect) { .origin = { 0, 47 }, .size = { bounds.size.w, 20 } });
  y_accel_layer = text_layer_create((GRect) { .origin = { 0, 72 }, .size = { bounds.size.w, 20 } });
  z_accel_layer = text_layer_create((GRect) { .origin = { 0, 97 }, .size = { bounds.size.w, 20 } });

  text_layer_set_text_alignment(x_accel_layer, GTextAlignmentCenter);
  text_layer_set_text_alignment(y_accel_layer, GTextAlignmentCenter);
  text_layer_set_text_alignment(z_accel_layer, GTextAlignmentCenter);

  layer_add_child(window_layer, text_layer_get_layer(x_accel_layer));
  layer_add_child(window_layer, text_layer_get_layer(y_accel_layer));
  layer_add_child(window_layer, text_layer_get_layer(z_accel_layer));

  accel_data_service_subscribe(1, process_accel_data);
}

static void window_unload(Window *window) {
  accel_data_service_unsubscribe();

  text_layer_destroy(x_accel_layer);
  text_layer_destroy(y_accel_layer);
  text_layer_destroy(z_accel_layer);
}

static void init(void) {
  window = window_create();
  window_set_window_handlers(window, (WindowHandlers) {
    .load = window_load,
    .unload = window_unload,
  });
  const bool animated = true;
  window_stack_push(window, animated);
}

static void deinit(void) {
  window_destroy(window);
}

int main(void) {
  init();

  APP_LOG(APP_LOG_LEVEL_DEBUG, "Done initializing, pushed window: %p", window);

  app_event_loop();
  deinit();
}