The main module of Taffybar

This is a system status bar meant for use with window manager like XMonad. It is similar to xmobar, but with more visual flare and a different widget set. Contributed widgets are more than welcome. The bar is drawn using gtk and cairo. It is actually the simplest possible thing that could plausibly work: you give Taffybar a list of GTK widgets and it will render them in a horizontal bar for you (taking care of ugly details like reserving strut space so that window managers don't put windows over it).

This is the real main module. The default bar should be customized to taste in the config file (~.configtaffybar/taffybar.hs). Typically, this means adding widgets to the default config. A default configuration file is included in the distribution, but the essentials are covered here.

The config file is just a Haskell source file that is compiled at startup (if it has changed) to produce a custom executable with the desired set of widgets. You will want to import this module along with the modules of any widgets you want to add to the bar. Note, you can define any widgets that you want in your config file or other libraries. Taffybar only cares that you give it some GTK widgets to display.

Below is a fairly typical example:

 import System.Taffybar
 import System.Taffybar.Systray
 import System.Taffybar.XMonadLog
 import System.Taffybar.SimpleClock
 import System.Taffybar.Widgets.PollingGraph
 import System.Information.CPU

 cpuCallback = do
   (_, systemLoad, totalLoad) <- cpuLoad
   return [ totalLoad, systemLoad ]

 main = do
   let cpuCfg = defaultGraphConfig { graphDataColors = [ (0, 1, 0, 1), (1, 0, 1, 0.5)]
                                   , graphLabel = Just "cpu"
                                   }
       clock = textClockNew Nothing "<span fgcolor='orange'>%a %b %_d %H:%M</span>" 1
       log = xmonadLogNew
       tray = systrayNew
       cpu = pollingGraphNew cpuCfg 0.5 cpuCallback
   defaultTaffybar defaultTaffybarConfig { startWidgets = [ log ]
                                         , endWidgets = [ tray, clock, cpu ]
                                         }

This configuration creates a bar with four widgets. On the left is the XMonad log. The rightmost widget is the system tray, with a clock and then a CPU graph. The clock is formatted using standard strftime-style format strings (see the clock module). Note that the clock is colored using Pango markup (again, see the clock module).

The CPU widget plots two graphs on the same widget: total CPU use in green and then system CPU use in a kind of semi-transparent purple on top of the green.

It is important to note that the widget lists are *not* [Widget]. They are actually [IO Widget] since the bar needs to construct them after performing some GTK initialization.

The XMonadLog widget differs from its counterpart in xmobar: it listens for updates over DBus instead of reading from stdin. This makes it easy to restart Taffybar independently of XMonad. XMonad does not come with a DBus logger, so here is an example of how to make it work. Note: this requires the dbus-core (>0.9) package, which is installed as a dependency of Taffybar.

 import XMonad.Hooks.DynamicLog
 import DBus.Client.Simple
 import System.Taffybar.XMonadLog ( dbusLog )

 main = do
   client <- connectSession
   let pp = defaultPP
   xmonad defaultConfig { logHook = dbusLog client pp }

The complexity is handled in the System.Tafftbar.XMonadLog module.

• If you start xmonad using a graphical login manager like gdm or kdm, DBus should be started automatically for you.
• If you start xmonad with a different graphical login manager that does not start DBus for you automatically, put the line eval `dbus-launch --auto-syntax` into your ~/.xsession *before* xmonad and taffybar are started. This command sets some environment variables that the two must agree on.
• If you start xmonad via startx or a similar command, add the above command to ~/.xinitrc

While taffybar is based on GTK+, it ignores your GTK+ theme. The default theme that it uses is in ~/.cabal/share/taffybar-<version>/taffybar.rc. You can customize this theme by copying it to ~/.config/taffybar/taffybar.rc. For an idea of the customizations you can make, see https://live.gnome.org/GnomeArt/Tutorials/GtkThemes.