Add battery_widget base code.

init.lua

@@ -0,0 +1,72 @@
+local upower = require('lgi').require('UPowerGlib')
+local textbox = require 'wibox.widget.textbox'
+
+local string = { format = string.format }
+local math = { floor = math.floor }
+
+local setmetatable = setmetatable -- luacheck ignore: setmetatable
+
+local battery_widget = {}
+local mt = {}
+
+--- Helper function to convert seconds into a human readable clock string.
+--
+-- This translates the given seconds parameter into a human readable string
+-- following the notation `HH:MM` (where HH is the number of hours and MM the
+-- number of minutes).
+-- @tparam number seconds The umber of seconds to translate.
+-- @treturn string The human readable generated clock string.
+function battery_widget.to_clock(seconds)
+    if seconds <= 0 then
+        return '00:00';
+    else
+        local hours = string.format('%02.f', math.floor(seconds/3600));
+        local mins = string.format('%02.f', math.floor(seconds/60 - hours*60));
+        return hours .. ':' .. mins
+    end
+end
+
+--- Update the battery widget with the given device.
+--
+-- This method can be called by the user but it was designed to be used
+-- automatically by UPower thanks to the `UPowerGlib.Device` notify signal.
+-- @tparam battery_widget self The battery_widget instance to update.
+-- @tparam UPowerGlib.Device device The device to use for the update.
+function battery_widget.update (self, device)
+    local text
+
+    if device.state == upower.DeviceState.CHARGING  then
+        text = 'Full in ' .. battery_widget.to_clock(device.time_to_full)
+    elseif device.state == upower.DeviceState.DISCHARGING then
+        text = string.format('%3d', device.percentage) .. '%'
+    else
+        text = 'N/A'
+    end
+
+    self:set_markup(text)
+end
+
+--- battery_widget constructor.
+--
+-- This function creates a new `battery_widget` instance. This widget watches
+-- the `display_device` status and report.
+-- @treturn battery_widget The battery_widget instance build.
+function battery_widget.new ()
+    local widget = textbox()
+
+    widget.update = battery_widget.update
+
+    local display_device = upower.Client():get_display_device()
+    display_device.on_notify = function (device) widget:update(device) end
+
+    widget:update(display_device)
+
+    return widget
+end
+
+
+function mt.__call(self, ...)
+    return battery_widget.new(...)
+end
+
+return setmetatable(battery_widget, mt)