Draw axis if data crosses zero

[batteryviewer] / batteryviewer.c

// For vasprintf
#define _GNU_SOURCE

#include "chart.h"
#include <ctype.h>
#include <errno.h>
#include <glob.h>
#include <gtk/gtk.h>
#include <math.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *sasprintf(const char *fmt, ...) {
  char *result;
  va_list args;
  va_start(args, fmt);
  if (vasprintf(&result, fmt, args) == -1) {
    fprintf(stderr, "Can't allocate memory!?\n");
    abort();
  }
  va_end(args);
  return result;
}

struct State {
  char *voltage_filename;
  char *current_filename;
  BVChart *voltage;
  BVChart *current;
};

static float fatof(const char *filename) {
  FILE *f = fopen(filename, "r");
  if (f == NULL) {
    return NAN;
  }

  const int bufsize = 1024;
  char buf[bufsize];
  const int read = fread(buf, sizeof(char), bufsize, f);
  if (read == 0 || read == bufsize || ferror(f)) {
    fclose(f);
    return NAN;
  }
  fclose(f);

  char *end;
  errno = 0;
  float val = strtof(buf, &end);
  int parsed = end - buf;
  gboolean parsed_all = parsed == read;
  gboolean parsed_all_but_space = parsed == read - 1 && isspace(*end);
  gboolean parse_ok = parsed_all || parsed_all_but_space;
  if (errno != 0 || parsed == 0 || !parse_ok) {
    return NAN;
  }
  return val;
}

static gboolean collect_data(struct State *state) {
  float now = g_get_monotonic_time() / 1e6;
  float voltage = fatof(state->voltage_filename);
  float current = fatof(state->current_filename);
  if (!isnan(voltage)) {
    bv_chart_add_point(state->voltage, now, voltage);
    gtk_widget_queue_draw(GTK_WIDGET(state->voltage));
  }
  if (!isnan(current)) {
    bv_chart_add_point(state->current, now, current);
    gtk_widget_queue_draw(GTK_WIDGET(state->current));
  }
  return TRUE;
}

static void activate(GtkApplication *app, gpointer user_data) {

  GtkWidget *window = gtk_application_window_new(app);
  gtk_window_set_title(GTK_WINDOW(window), "BatteryViewer");
  gtk_window_set_default_size(GTK_WINDOW(window), 200, 200);

  GtkWidget *box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 1);
  gtk_container_add(GTK_CONTAINER(window), box);

  struct State *state = (struct State *)user_data;
  state->voltage = BV_CHART(bv_chart_new());
  gboolean expand = TRUE;
  gboolean fill = TRUE;
  guint padding = 0;
  gtk_box_pack_start(GTK_BOX(box), GTK_WIDGET(state->voltage), expand, fill,
                     padding);

  state->current = BV_CHART(bv_chart_new());
  gtk_box_pack_end(GTK_BOX(box), GTK_WIDGET(state->current), expand, fill,
                   padding);

  gtk_widget_show_all(window);

  g_timeout_add_seconds(1, (GSourceFunc)collect_data, user_data);
}

char *find_battery_dir() {
  glob_t globbuf = {.gl_offs = 0};
  char pattern[] = "/sys/class/power_supply/*[Bb][Aa][Tt]*";
  if (glob(pattern, GLOB_ERR, NULL, &globbuf) != 0 || globbuf.gl_pathc == 0) {
    fprintf(stderr, "Could not find battery dir %s\n", pattern);
    exit(1);
  }
  if (globbuf.gl_pathc != 1) {
    // TODO: Filter for directories that have {voltage,current}_now files.
    // TODO: Support multiple batteries
    fprintf(stderr, "Multiple batteries found. Arbitrarily choosing %s\n",
            globbuf.gl_pathv[0]);
  }
  char *dir = strdup(globbuf.gl_pathv[0]);
  globfree(&globbuf);
  return dir;
}

int main(int argc, char **argv) {
  char *battery_dir = find_battery_dir();
  struct State state = {
      .voltage_filename = sasprintf("%s/voltage_now", battery_dir),
      .current_filename = sasprintf("%s/current_now", battery_dir),
  };

  GtkApplication *app = gtk_application_new("com.scottworley.batteryviewer",
                                            G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect(app, "activate", G_CALLBACK(activate), &state);
  int status = g_application_run(G_APPLICATION(app), argc, argv);
  g_object_unref(app);

  return status;
}