Added a new, standalone, battery widget.

The widget reads /proc/acpi/battery/*/{info,state} and doesn't require
an external utility like 'acpi' or 'acpitool'. It returns state,
charge and remaining time information, just like the old bat (now
batat) widget. Using /sys/class/power_supply we would need to open
much more file descriptors so we use /proc for now.

bat.lua

@@ -0,0 +1,79 @@
+----------------------------------------------------------
+-- Licensed under the GNU General Public License version 2
+--  * Copyright (C) 2009 Adrian C. <anrxc_sysphere_org>
+----------------------------------------------------------
+
+-- {{{ Grab environment
+local tonumber = tonumber
+local io = { open = io.open }
+local math = { floor = math.floor }
+local string = {
+    find = string.find,
+    match = string.match,
+    format = string.format
+}
+-- }}}
+
+
+-- Bat: provides state, charge, and remaining time for a requested battery
+module("vicious.bat")
+
+
+-- {{{ Battery widget type
+function worker(format, batid)
+    -- Initialise tables
+    local battery_state = {
+        ["full"]        = "*",
+        ["unknown"]     = " ",
+        ["charged"]     = "*",
+        ["charging"]    = "+",
+        ["discharging"] = "-"
+    }
+
+    -- Get /proc/acpi/battery info
+    local finfo = io.open("/proc/acpi/battery/"..batid.."/info")
+    local infofile = finfo:read("*all")
+    finfo:close()
+
+    -- Check if the file wasn't found or the battery isn't present
+    if infofile == nil or string.find(infofile, "present:[%s]+no") then
+        return { "/", "/", "/" }
+    else
+        -- Get capacity information
+        local capacity = string.match(infofile, "last full capacity:[%s]+([%d]+).*")
+
+
+        -- Get /proc/acpi/battery state
+        local fstate = io.open("/proc/acpi/battery/"..batid.."/state")
+        local statefile = fstate:read("*all")
+        fstate:close()
+
+        -- Get state information
+        local state = string.match(statefile, "charging state:[%s]+([%a]+).*")
+        local state = battery_state[state] or battery_state["unknown"]
+
+        -- Get charge information
+        local rate = string.match(statefile, "present rate:[%s]+([%d]+).*")
+        local remaining = string.match(statefile, "remaining capacity:[%s]+([%d]+).*")
+
+
+        -- Calculate percentage
+        local percent = math.floor(remaining / capacity * 100)
+        local percent = string.format("%02d", percent)
+
+        -- Calculate remaining (charging or discharging) time
+        if state == "+" then
+            timeleft = (tonumber(capacity) - tonumber(remaining)) / tonumber(rate)
+        elseif state == "-" then
+            timeleft = tonumber(remaining) / tonumber(rate)
+        else
+            return { state, percent, "/" }
+        end
+        local hoursleft = math.floor(timeleft)
+        local minutesleft = math.floor((timeleft - hoursleft) * 60 )
+        local time = string.format("%02d:%02d", hoursleft, minutesleft)
+
+        return { state, percent, time }
+    end
+end
+-- }}}