wmstatus: rework battery reporting

Report "USB" and USB devices as well (SpaceMouse, Intuos),
make use of the "capacity" field everywhere.

Present read errors to the user, rather than spam the log.

wmstatus.c

@@ -1022,13 +1022,14 @@ read_value (int dir, const char *filename, struct error **e)
 		return NULL;
 	}
 
+	errno = 0;
 	struct str s = str_make ();
-	bool success = read_line (fp, &s);
+	bool success = read_line (fp, &s) && !ferror (fp);
 	fclose (fp);
 
 	if (!success)
 	{
-		error_set (e, "%s: %s", filename, "read failed");
+		error_set (e, "%s: %s", filename, errno ? strerror (errno) : "EOF");
 		return NULL;
 	}
 	return str_steal (&s);
@@ -1043,42 +1044,61 @@ read_number (int dir, const char *filename, struct error **e)
 
 	unsigned long number = 0;
 	if (!xstrtoul (&number, value, 10))
-		error_set (e, "%s: %s", filename, "doesn't contain an unsigned number");
+		error_set (e, "%s: %s", filename, "doesn't contain a valid number");
 	free (value);
 	return number;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
-static char *
+static int
-read_battery_status (int dir, struct error **e)
+read_battery_charge (int dir)
 {
-	char *result = NULL;
 	struct error *error = NULL;
+	double capacity, now, full;
+	if ((capacity = read_number (dir, "capacity",    &error), !error))
+		return capacity;
 
-	char *status;
+	error_free (error);
-	double charge_now;
+	if ((now      = read_number (dir, "charge_now",  &error), !error)
-	double charge_full;
+	 && (full     = read_number (dir, "charge_full", &error), !error))
+		return now / full * 100 + 0.5;
 
-	if ((status      = read_value  (dir, "status",      &error), error)
+	error_free (error);
-	 || (charge_now  = read_number (dir, "charge_now",  &error), error)
+	return -1;
-	 || (charge_full = read_number (dir, "charge_full", &error), error))
+}
-		error_propagate (e, error);
+
-	else
+static char *
-	{
+read_battery_status (int dir, char **type)
+{
+	// We present errors to the user, don't fill up the session's log.
+	struct error *error = NULL;
 	struct str s = str_make ();
-		str_append (&s, status);
 
 	// Dell is being unreasonable and seems to set charge_now
 	// to charge_full_design when the battery is fully charged
-		unsigned percentage = charge_now / charge_full * 100 + 0.5;
+	int charge = read_battery_charge (dir);
-		if (percentage < 100)
+	if (charge >= 0 && charge <= 100)
-			str_append_printf (&s, " (%u%%)", percentage);
+		str_append_printf (&s, "%u%%", charge);
-		result = str_steal (&s);
-	}
 
+	char *status = NULL;
+	char *model_name = read_value (dir, "model_name", NULL);
+	if (model_name)
+	{
+		model_name[strcspn (model_name, " ")] = 0;
+		cstr_set (type, model_name);
+	}
+	else if ((status = read_value (dir, "status", &error), !error))
+	{
+		str_append_printf (&s, " (%s)", status);
 		free (status);
-	return result;
+	}
+	else
+	{
+		str_append_printf (&s, " (%s)", strerror (errno));
+		error_free (error);
+	}
+	return str_steal (&s);
 }
 
 static char *
@@ -1094,14 +1114,13 @@ try_power_supply (int dir, struct error **e)
 
 	bool is_relevant =
 		!strcmp (type, "Battery") ||
+		!strcmp (type, "USB") ||
 		!strcmp (type, "UPS");
 
 	char *result = NULL;
 	if (is_relevant)
 	{
-		char *status = read_battery_status (dir, &error);
+		char *status = read_battery_status (dir, &type);
-		if (error)
-			error_propagate (e, error);
 		if (status)
 			result = xstrdup_printf ("%s %s", type, status);
 		free (status);
@@ -1122,8 +1141,8 @@ make_battery_status (void)
 	}
 
 	struct dirent *entry;
-	char *status = NULL;
+	struct strv batteries = strv_make ();
-	while (!status && (entry = readdir (power_supply)))
+	while ((entry = readdir (power_supply)))
 	{
 		const char *device_name = entry->d_name;
 		if (device_name[0] == '.')
@@ -1137,8 +1156,11 @@ make_battery_status (void)
 		}
 
 		struct error *error = NULL;
-		status = try_power_supply (dir, &error);
+		char *status = try_power_supply (dir, &error);
 		close (dir);
+
+		if (status)
+			strv_append_owned (&batteries, status);
 		if (error)
 		{
 			print_error ("%s: %s", device_name, error->message);
@@ -1146,7 +1168,10 @@ make_battery_status (void)
 		}
 	}
 	closedir (power_supply);
-	return status;
+
+	char *result = batteries.len ? strv_join (&batteries, " ") : NULL;
+	strv_free (&batteries);
+	return result;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -