bat: expose information on battery wear and tear

Modern batteries should expose information about their design capacity
which we can compare to current capacity and deduce how much 'wear'
the battery got and expose that as a negative value percentage.

Feature sent in August took a while to convince the maintainer many
modern batteries provide this information.

Signed-off-by: Adrian C. (anrxc) <anrxc@sysphere.org>

README

@@ -159,11 +159,12 @@ vicious.widgets.uptime
     for 5 minutes and 6th for 15 minutes
 
 vicious.widgets.bat
-  - provides state, charge, and remaining time for a requested battery
+  - provides state, charge, remaining time and wear for a requested
+    battery
   - takes battery ID as an argument, i.e. "BAT0"
   - returns 1st value as state of requested battery, 2nd as charge
-    level in percent and 3rd as remaining (charging or discharging)
-    time
+    level in percent, 3rd as remaining (charging or discharging)
+    time and 4th as the wear level in percent
 
 vicious.widgets.mem
   - provides RAM and Swap usage statistics

widgets/bat.lua

@@ -1,6 +1,7 @@
 ---------------------------------------------------
 -- Licensed under the GNU General Public License v2
 --  * (c) 2010, Adrian C. <anrxc@sysphere.org>
+--  * (c) 2013, NormalRa  <normalrawr@gmail.com>
 ---------------------------------------------------
 
 -- {{{ Grab environment
@@ -15,7 +16,7 @@ local math = {
 -- }}}
 
 
--- Bat: provides state, charge, and remaining time for a requested battery
+-- Bat: provides state, charge, remaining time, and wear for a requested battery
 -- vicious.widgets.bat
 local bat = {}
 
@@ -35,7 +36,7 @@ local function worker(format, warg)
 
     -- Check if the battery is present
     if battery.present ~= "1\n" then
-        return {battery_state["Unknown\n"], 0, "N/A"}
+        return {battery_state["Unknown\n"], 0, "N/A", 0}
     end
 
 
@@ -45,14 +46,17 @@ local function worker(format, warg)
     -- Get capacity information
     if battery.charge_now then
         remaining, capacity = battery.charge_now, battery.charge_full
+        capacity_design = battery.charge_full_design or capacity
     elseif battery.energy_now then
         remaining, capacity = battery.energy_now, battery.energy_full
+        capacity_design = battery.energy_full_design or capacity
     else
-        return {battery_state["Unknown\n"], 0, "N/A"}
+        return {battery_state["Unknown\n"], 0, "N/A", 0}
     end
 
-    -- Calculate percentage (but work around broken BAT/ACPI implementations)
+    -- Calculate capacity and wear percentage (but work around broken BAT/ACPI implementations)
     local percent = math.min(math.floor(remaining / capacity * 100), 100)
+    local wear = math.floor(100 - capacity / capacity_design * 100)
 
 
     -- Get charge information
@@ -61,7 +65,7 @@ local function worker(format, warg)
     elseif battery.power_now then
         rate = tonumber(battery.power_now)
     else
-        return {state, percent, "N/A"}
+        return {state, percent, "N/A", wear}
     end
 
     -- Calculate remaining (charging or discharging) time
@@ -73,7 +77,7 @@ local function worker(format, warg)
         elseif state == "-" then
             timeleft = tonumber(remaining) / tonumber(rate)
         else
-            return {state, percent, time}
+            return {state, percent, time, wear}
         end
 
         -- Calculate time
@@ -83,7 +87,7 @@ local function worker(format, warg)
         time = string.format("%02d:%02d", hoursleft, minutesleft)
     end
 
-    return {state, percent, time}
+    return {state, percent, time, wear}
 end
 -- }}}