~/.config/taffybar: Add memory usage widget.

Surprisingly, only calling pollingLabelNew doesn't do the job, we have
to call Graphics.UI.Gtk.widgetShowAll, too.

.config/taffybar/taffybar.hs

import System.Taffybar.XMonadLog
import System.Taffybar.SimpleClock
import System.Taffybar.Widgets.PollingGraph
import System.Taffybar.Widgets.PollingLabel
import System.Information.CPU
import System.Information.Memory (parseMeminfo, memoryUsedRatio)
import Graphics.UI.Gtk (widgetShowAll)
cpuCallback = do
    (_, systemLoad, totalLoad) <- cpuLoad
    return [ totalLoad, systemLoad ]
formatMeminfo m = "Mem: " ++ memPercentage ++ "%"
    where memPercentage = show . truncate . ((*) 100) $ memoryUsedRatio m
textMemoryNew intervalSeconds = do
    memLabel <- pollingLabelNew "" intervalSeconds (parseMeminfo >>= return . formatMeminfo)
    widgetShowAll memLabel
    return memLabel
main = do
    let cpuCfg = defaultGraphConfig {
            graphDataColors = [(0, 1, 0, 1), (1, 0, 1, 0.5)]
        log = xmonadLogNew
        tray = systrayNew
        cpu = pollingGraphNew cpuCfg 3 cpuCallback
        battery = textBatteryNew "%d%%" 30
        battery = textBatteryNew "Bat: %d%%" 30
        memory = textMemoryNew 3
    defaultTaffybar defaultTaffybarConfig {
        barHeight = 15,
        startWidgets = [log],
        endWidgets = [tray, clock, battery, cpu]
        endWidgets = [tray, clock, memory, battery, cpu]
    }