[eureka]

Originally Posted by nick-tech

Thank you NiJuLe for your quick response. It's almost what I want, but i'd like to see the charge/discharge rate permanently in the status bar, just like the charge percentage. Is there a way to get that working?

Here are three files.

/etc/init/battery_current_indicator.conf

Spoiler:

# Copyright © 2015  eureka
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
# DEALINGS IN THE SOFTWARE.

start on started pillow
stop on stopping pillow

pre-start script
  # Wait for pillow on 'started pillow' event.
  if [ "x${JOB}" == "xpillow" -a "x${UPSTART_EVENTS}" == "xstarted" ]; then
    lipc-wait-event com.lab126.pillow stateChange
    sleep 2
  fi
end script

post-start exec /bin/sh /var/local/battery_current/battery_current_indicator.sh enable

pre-stop exec /bin/sh /var/local/battery_current/battery_current_indicator.sh disable

exec /usr/bin/lua /var/local/battery_current/battery_current_lipc_publisher.lua

/var/local/battery_current/battery_current_indicator.sh

Spoiler:

#!/bin/sh

# Copyright © 2015  eureka
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
# DEALINGS IN THE SOFTWARE.

# Format given standard input (remove newlines and escape double quotes)
# for using it in JSON message passed to lipc-set-prop.
format_js_script () {
  local line
  local js_script

  while IFS="" read -r line; do js_script="${js_script}${line}"; done

  echo "${js_script}" | sed -e 's,",\\",g'
}

[ "x${1}" = "xdisable" ] && ENABLE_INDICATOR=false || ENABLE_INDICATOR=true

# Construct JavaScript code executed in context of Pillow container.
# It's glued into one big line (newlines are removed), so syntax semicolons
# are required and any comments must be block comments (not line comments).
SCRIPT=`format_js_script << 'JAVASCRIPT' \
        | sed -e "s/__ENABLE_INDICATOR__/${ENABLE_INDICATOR}/"
  /* JavaScript code begins here. */
  (function () {
    var _enableIndicator = __ENABLE_INDICATOR__,
        _originalEventsCallback = StatusBar && StatusBar.eventsCallback,
        _batteryIconId = BatteryState.batteryIconDiv,
        _batteryIconEl = _batteryIconId
                         && document.getElementById(_batteryIconId),
        _batteryCurrentId = "batteryCurrent",
        _batteryCurrentEl = document.getElementById(_batteryCurrentId);

    /* Stock battery icon element not found or LIPC events handler function is
     * not defined under expected name, return immediately. */
    if (!_batteryIconEl || !_originalEventsCallback) {
      return;
    }

    /* Custom element displaying battery current already present in DOM.
     * Either return early if disabling was not requested or execute
     * disabling procedures and then return.
     */
    if (_batteryCurrentEl !== null) {
      if (_enableIndicator) {
        return;
      }
      _batteryCurrentEl.parentNode.removeChild(_batteryCurrentEl);
      return;
    }

    /* Setup element for displaying battery current. */
    _batteryCurrentEl = document.createElement("div");
    _batteryCurrentEl.id = _batteryCurrentId;
    _batteryCurrentEl.style.paddingTop = "2pt";
    _batteryCurrentEl.style.paddingRight = "3pt";
    _batteryCurrentEl.textContent = "_ mA";

    /* It is not possible to unsubscribe from LIPC event in Pillow container
     * (or, at least, I did not find a way to do it).
     *
     * Here part of event handler is attached to 'window' object. It is
     * persisted between disabling and enabling indicator and shows that
     * subscribing was already done.
     */
    if (typeof window.__updateBatteryCurrent__ !== "function") {
      window.__updateBatteryCurrent__ = function (batteryCurrentValue) {
        var batteryCurrentEl = document.getElementById(_batteryCurrentId);

        if (batteryCurrentEl === null) {
          /* Indicator was disabled. */
          return;
        }

        batteryCurrentEl.textContent =
          batteryCurrentValue
          ? (batteryCurrentValue + " mA")
          : "? ma";
      };

      StatusBar.eventsCallback = function (eventDataJson) {
        var eventData = JSON.parse(eventDataJson),
            eventSrcOk =
              eventData
              && (eventData.eventSrc === "com.example.batterycurrent"),
            eventNameOk =
              eventData
              && (eventData.eventName === "currentChanged"),
            eventValues = eventData && eventData.eventValues;

        if (eventSrcOk && eventNameOk && eventValues) {
          window.__updateBatteryCurrent__(eventValues[0]);
        }

        _originalEventsCallback(eventDataJson);
      };

      nativeBridge.registerEventsWatchCallback(StatusBar.eventsCallback);
      nativeBridge.subscribeToEvent(
        "com.example.batterycurrent",
        "currentChanged"
      );
    }

    /* Insert battery current element left of stock battery icon. */
    _batteryIconEl.parentNode.insertBefore(_batteryCurrentEl, _batteryIconEl);

    /* Get initial battery current value and display it. */
    window.__updateBatteryCurrent__(nativeBridge.getIntLipcProperty(
      "com.example.batterycurrent",
      "ma"
    ));
  })();
  /* JavaScript code ends here. */
`

MESSAGE='{
  "pillowId": "default_status_bar",
  "function": "'${SCRIPT}'"
}'

lipc-set-prop -s com.lab126.pillow interrogatePillow "${MESSAGE}"

/var/local/battery_current/battery_current_lipc_publisher.lua

Spoiler:

#!/usr/bin/lua

-- Copyright © 2015  eureka
--
-- Permission is hereby granted, free of charge, to any person obtaining a
-- copy of this software and associated documentation files (the "Software"),
-- to deal in the Software without restriction, including without limitation
-- the rights to use, copy, modify, merge, publish, distribute, sublicense,
-- and/or sell copies of the Software, and to permit persons to whom the
-- Software is furnished to do so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in
-- all copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-- FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-- DEALINGS IN THE SOFTWARE.

require("liblipclua")

------------------------------------------------------------------------------
-- Configuration
------------------------------------------------------------------------------

-- Script registers itself as a LIPC publisher under this name.
local LIPC_PUBLISHER_NAME = "com.example.batterycurrent"

-- Battery current will be exported through this LIPC int property.
local LIPC_PROPERTY_NAME = "ma"

-- Changed battery current value is broadcasted by script as a LIPC event with
-- this name.
-- (Set it to nil to disable event sending.)
local LIPC_EVENT_NAME = "currentChanged"

-- Glob pattern of path to file with data of battery current.
--
-- Part of data file path is changed between device models, so real path
-- is found in runtime by glob pattern.
local DATA_FILE_GLOB = "/sys/devices/system/*_battery/*_battery0/battery_current"

-- Time period between re-reading data from data file.
local DATA_REFRESH_PERIOD = 1 -- second(s)

------------------------------------------------------------------------------
-- Supporting functions
------------------------------------------------------------------------------

local function exit_with_message(exit_code, message)
  io.stderr:write(message .. "\n")
  io.stderr:flush()
  os.exit(exit_code)
end

-- Call 'ls' command with passed glob pattern and return found path to file.
local function find_file_path (file_glob)
  local cmd = "ls " .. file_glob
  local output, err_message = io.popen(cmd, "r")
  if output == nil then
    error(err_message)
  end
  local file_path = output:read()
  output:close()
  if file_path == nil then
    error("Can't read output of '" .. cmd .. "'")
  elseif file_path:sub(1, 4) == "ls: " then
    error("Can't find file by glob pattern '" .. file_glob .. "'")
  end
  return file_path
end

-- Return battery current value read from first file line.
local function read_current_from_file (file_path)
  local file, err_message = io.open(file_path)
  if file == nil then
    error(err_message)
  end
  local result = file:read("*n")
  file:close()
  if result == nil then
    error("Can't read number from file '" .. file_path .. "'")
  end
  return result
end

------------------------------------------------------------------------------
-- Program setup
------------------------------------------------------------------------------

local data_file_found, data_file_path = pcall(find_file_path, DATA_FILE_GLOB)
if not data_file_found then
  exit_with_message(1, data_file_path)
end

local lipc_handle, lipc_err_msg, lipc_err_num = lipc.init(LIPC_PUBLISHER_NAME)
if not lipc_handle then
  exit_wit_message(
    lipc_err_num,
    "Failed to initialize LIPC: ("
    .. tostring(lipc_err_num) .. ") "
    .. lipc_err_msg)
else
  lipc.set_error_handler(function(msg) io.stderr:write(msg .. "\n") end)
end

local ma_property = lipc_handle:register_int_property(LIPC_PROPERTY_NAME, "r")

------------------------------------------------------------------------------
-- Main loop
------------------------------------------------------------------------------

local ma_value_read_ok, ma_value, prev_ma_value
while true do
  -- Read battery current value.
  ma_value_read_ok, ma_value = pcall(read_current_from_file, data_file_path)
  if not ma_value_read_ok then
    lipc_handle:close()
    exit_with_message(1, ma_value)
  end
  -- Set LIPC property value.
  ma_property.value = ma_value
  -- Send LIPC event when value is changed.
  if LIPC_EVENT_NAME ~= nil and ma_value ~= prev_ma_value then
    lipc_handle:send_event(LIPC_EVENT_NAME, {ma_value})
    prev_ma_value = ma_value
  end
  -- Use event loop timeout as a pause duration.
  lipc.run_event_loop(DATA_REFRESH_PERIOD)
end
lipc_handle:close()

Put them on their paths. Then indicator could be enabled with start battery_current_indicator or disabled with stop battery_current_indicator. It will also be enabled automatically on pillow (re)start (i.e. on reboot too).

Battery current will be displayed as 78 mA or -98 mA left of stock battery icon in status bar. Sysfs value will be continuously polled in intervals of 1 second and status bar indicator will be refreshed on value change.

It was tested on Kindle Touch 5.3.7.2.