[xmonad] Understanding how to build and run xmonad

[Weeble]

I've been using xmonad for over a year and I love it, but I am deathly
afraid of editing my configuration or upgrading to new versions
because I find it a deeply confusing and error-prone experience. I
would love to understand it all a bit more so that I am better able to
make proper use of xmonad and to benefit from all the good work people
are doing on it.

My latest trauma comes after getting exasperated with no full-screen
in Google Chrome. Reading a page on the bug-tracker[1] led me to guess
that the problem might be fixed if I upgraded to a more recent version
of xmonad. Unfortunately, I could not remember how I originally
installed xmonad - was it via apt-get, cabal or by fetching the source
from darcs and building it by hand? Do some or all of these result in
the same thing? Are some or all of these completely incompatible with
each other? What about cabal-install and ghc? I am 80% certain that I
installed ghc with apt-get. Does cabal come with it? I tried running
"cabal update" and it complained about something being too new or too
old. I fear I got myself into a terrible mess trying to install or
uninstall things and I'm not terribly sure how to get to a known good
state from there. It may be that I have here a very poor foundation
for everything that follows, but I think I somehow got to a point
where I could continue...

I discovered that I have a darcs repository for xmonad and
XMonadContrib. I went into each of these and did "darcs pull" and
answered "a" when it asked which patches I wanted. I did "cabal
install" in each in turn. xmonad built and installed itself somewhere,
but XMonadContrib gave me an error:

~/xmonad/XMonadContrib$ cabal install
Resolving dependencies...
Configuring xmonad-0.9.2...
Preprocessing library xmonad-0.9.2...
Preprocessing executables for xmonad-0.9.2...
Building xmonad-0.9.2...
[1 of 8] Compiling XMonad.StackSet  ( XMonad/StackSet.hs,
dist/build/XMonad/StackSet.o )
[2 of 8] Compiling XMonad.Core      ( XMonad/Core.hs, dist/build/XMonad/Core.o )
[3 of 8] Compiling XMonad.Layout    ( XMonad/Layout.hs,
dist/build/XMonad/Layout.o )
[4 of 8] Compiling XMonad.Operations ( XMonad/Operations.hs,
dist/build/XMonad/Operations.o )
[5 of 8] Compiling XMonad.ManageHook ( XMonad/ManageHook.hs,
dist/build/XMonad/ManageHook.o )
[6 of 8] Compiling XMonad.Config    ( XMonad/Config.hs,
dist/build/XMonad/Config.o )
[7 of 8] Compiling XMonad.Main      ( dist/build/XMonad/Main.hs,
dist/build/XMonad/Main.o )
[8 of 8] Compiling XMonad           ( XMonad.hs, dist/build/XMonad.o )
Registering xmonad-0.9.2...
[ 1 of 10] Compiling XMonad.StackSet  ( XMonad/StackSet.hs,
dist/build/xmonad/xmonad-tmp/XMonad/StackSet.o )
[ 2 of 10] Compiling XMonad.Core      ( XMonad/Core.hs,
dist/build/xmonad/xmonad-tmp/XMonad/Core.o )
[ 3 of 10] Compiling XMonad.Layout    ( XMonad/Layout.hs,
dist/build/xmonad/xmonad-tmp/XMonad/Layout.o )
[ 4 of 10] Compiling XMonad.Operations ( XMonad/Operations.hs,
dist/build/xmonad/xmonad-tmp/XMonad/Operations.o )
[ 5 of 10] Compiling XMonad.ManageHook ( XMonad/ManageHook.hs,
dist/build/xmonad/xmonad-tmp/XMonad/ManageHook.o )
[ 6 of 10] Compiling XMonad.Config    ( XMonad/Config.hs,
dist/build/xmonad/xmonad-tmp/XMonad/Config.o )
[ 7 of 10] Compiling XMonad.Main      (
dist/build/xmonad/xmonad-tmp/XMonad/Main.hs,
dist/build/xmonad/xmonad-tmp/XMonad/Main.o )
[ 8 of 10] Compiling Paths_xmonad     (
dist/build/autogen/Paths_xmonad.hs,
dist/build/xmonad/xmonad-tmp/Paths_xmonad.o )
[ 9 of 10] Compiling XMonad           ( XMonad.hs,
dist/build/xmonad/xmonad-tmp/XMonad.o )
[10 of 10] Compiling Main             ( Main.hs,
dist/build/xmonad/xmonad-tmp/Main.o )
Linking dist/build/xmonad/xmonad ...
Installing library in /home/weeble/.cabal/lib/xmonad-0.9.2/ghc-6.12.1
Installing executable(s) in /home/weeble/.cabal/bin
Registering xmonad-0.9.2...
Configuring xmonad-contrib-0.9.1...
Preprocessing library xmonad-contrib-0.9.1...
Building xmonad-contrib-0.9.1...
[  1 of 212] Compiling XMonad.Util.StringProp (
XMonad/Util/StringProp.hs, dist/build/XMonad/Util/StringProp.o )
[  2 of 212] Compiling XMonad.Util.Replace ( XMonad/Util/Replace.hs,
dist/build/XMonad/Util/Replace.o )
[  3 of 212] Compiling XMonad.Util.CustomKeys (
XMonad/Util/CustomKeys.hs, dist/build/XMonad/Util/CustomKeys.o )
[  4 of 212] Compiling XMonad.Layout.ThreeColumns (
XMonad/Layout/ThreeColumns.hs, dist/build/XMonad/Layout/ThreeColumns.o
)
[  5 of 212] Compiling XMonad.Layout.StackTile (
XMonad/Layout/StackTile.hs, dist/build/XMonad/Layout/StackTile.o )
[  6 of 212] Compiling XMonad.Layout.Spiral ( XMonad/Layout/Spiral.hs,
dist/build/XMonad/Layout/Spiral.o )
[  7 of 212] Compiling XMonad.Layout.Roledex (
XMonad/Layout/Roledex.hs, dist/build/XMonad/Layout/Roledex.o )
[  8 of 212] Compiling XMonad.Layout.ResizableTile (
XMonad/Layout/ResizableTile.hs,
dist/build/XMonad/Layout/ResizableTile.o )
[  9 of 212] Compiling XMonad.Layout.OneBig ( XMonad/Layout/OneBig.hs,
dist/build/XMonad/Layout/OneBig.o )
[ 10 of 212] Compiling XMonad.Layout.MultiToggle (
XMonad/Layout/MultiToggle.hs, dist/build/XMonad/Layout/MultiToggle.o )
[ 11 of 212] Compiling XMonad.Layout.MultiColumns (
XMonad/Layout/MultiColumns.hs, dist/build/XMonad/Layout/MultiColumns.o
)
[ 12 of 212] Compiling XMonad.Layout.MosaicAlt (
XMonad/Layout/MosaicAlt.hs, dist/build/XMonad/Layout/MosaicAlt.o )
[ 13 of 212] Compiling XMonad.Layout.Mosaic ( XMonad/Layout/Mosaic.hs,
dist/build/XMonad/Layout/Mosaic.o )
[ 14 of 212] Compiling XMonad.Layout.LayoutBuilder (
XMonad/Layout/LayoutBuilder.hs,
dist/build/XMonad/Layout/LayoutBuilder.o )
[ 15 of 212] Compiling XMonad.Layout.HintedGrid (
XMonad/Layout/HintedGrid.hs, dist/build/XMonad/Layout/HintedGrid.o )
[ 16 of 212] Compiling XMonad.Layout.Simplest (
XMonad/Layout/Simplest.hs, dist/build/XMonad/Layout/Simplest.o )
[ 18 of 212] Compiling XMonad.Layout.Groups ( XMonad/Layout/Groups.hs,
dist/build/XMonad/Layout/Groups.o )
[ 19 of 212] Compiling XMonad.Layout.GridVariants (
XMonad/Layout/GridVariants.hs, dist/build/XMonad/Layout/GridVariants.o
)
[ 20 of 212] Compiling XMonad.Layout.Grid ( XMonad/Layout/Grid.hs,
dist/build/XMonad/Layout/Grid.o )
[ 21 of 212] Compiling XMonad.Layout.FixedColumn (
XMonad/Layout/FixedColumn.hs, dist/build/XMonad/Layout/FixedColumn.o )
[ 22 of 212] Compiling XMonad.Layout.Dishes ( XMonad/Layout/Dishes.hs,
dist/build/XMonad/Layout/Dishes.o )
[ 24 of 212] Compiling XMonad.Layout.Cross ( XMonad/Layout/Cross.hs,
dist/build/XMonad/Layout/Cross.o )
[ 25 of 212] Compiling XMonad.Layout.Column ( XMonad/Layout/Column.hs,
dist/build/XMonad/Layout/Column.o )
[ 26 of 212] Compiling XMonad.Layout.Circle ( XMonad/Layout/Circle.hs,
dist/build/XMonad/Layout/Circle.o )
[ 27 of 212] Compiling XMonad.Hooks.XPropManage (
XMonad/Hooks/XPropManage.hs, dist/build/XMonad/Hooks/XPropManage.o )
[ 28 of 212] Compiling XMonad.Util.Timer ( XMonad/Util/Timer.hs,
dist/build/XMonad/Util/Timer.o )

XMonad/Util/Timer.hs:38:2: Not in scope: `xfork'
cabal: Error: some packages failed to install:
xmonad-contrib-0.9.1 failed during the building phase. The exception was:
ExitFailure 1

Have I done something wrong? At first I had even more problems, but I
believe they were caused by my reckless use of "cabal install
$SOMETHING" to try to fix previous problems, but which just ended up
stacking more and more errors about conflicting versions. I got rid of
these by doing "ghc-pkg list" and "ghc-pkg unregister --user
$SOMETHING" for everything that turned up in the list of user
packages.

I have a few questions:
1. How can I get rid of everything and start again?
2. What do ghc-pkg and cabal install actually do, and where do they
put things? Does one of them call the other?
3. When I install xmonad, where does it go?
4. What is the relationship between the xmonad executable and my xmonad.hs file?
5. When does xmonad.hs get read and processed? Every time xmonad runs?
Every time I edit it? Only when I do something to specifically request
it?
6. When there's an error in my xmonad.hs, what am I left with? Does
xmonad behave as it did with the last known good xmonad.hs? Or does it
use some sort of safe configuration?
7. What should I do in the future to avoid getting myself in a mess?
Assuming that I will from time to time want to at least try out the
latest version from darcs, what should I get using apt-get, what
should I get with cabal, what (if anything) should I download source
distributions for and what should I get from darcs?

Wow, that' a lot of stuff, and I'm not even asking about debugging
changes to my xmonad.hs. I'll leave that for another day when I've got
a better handle on all this basic getting-it-all-up-and-running stuff.
Many thanks for your patience.

Weeble.

[1] - http://code.google.com/p/xmonad/issues/detail?id=339