[Xmonad] how to install?

[Jason Creighton]

On Sat, Apr 14, 2007 at 07:09:57AM -0700, David Roundy wrote:
> On Fri, Apr 13, 2007 at 06:04:46PM -0600, Jason Creighton wrote:
> > I poked around the cabal docs for a bit, and I didn't see any obvious
> > way to get cabal to check for the presence of certain headers. Also, if
> > the headers weren't there, we couldn't really do anything anyway, other
> > than fail with a friendlier error.
> 
> Argh! That seems crazy.  How can cabal not have support for looking for
> libraries? It's not so hard to write, but this seems like it'd be
> critical--certainly it'll be critical if we're going to use cabal for darcs
> (as Eric is in the process of doing).

I Am Not A Cabal Expert. Please take what I say with a grain of salt. :)

But it does appear to me that, for right now anyway, the answer is "use
autoconf or similar":
http://www.haskell.org/ghc/docs/latest/html/Cabal/authors.html#system-dependent

> > I wonder if the Xinerama module should be a separate package anyway.
> > What do you guys think about that?
> 
> It could be, but then we'd still depend on the module, unless cabal
> supports optional package dependencies.  I'd rather have a compile-time
> check whether xinerama is present, and preferably if it's not present then
> we should emit a warning (WARNING: compiling without xinerama support!!!)
> and compile an X11-extras with the same API, but which assumes just one
> screen.  It doesn't seem like it should be that hard, and reducing the
> number of libraries required would definitely be a Good Thing.  Most people
> don't actually have two monitors.

Yes, that could work. I'm working on doing this with a simple
"configure" (just a plain shell script, no autoconf (yet?)) script. I'll let
y'all know how it turns out.

This brings up another minor issue: Right now, Graphics.X11.Xinerama
exports:

XineramaScreenInfo data structure
xineramaIsActive :: Display -> IO Bool
xineramaQueryExtension :: Display -> IO (Maybe (CInt, CInt))
xineramaQueryVersion :: Display -> IO (Maybe (CInt, CInt))
xineramaQueryScreens :: Display -> IO (Maybe [XineramaScreenInfo])
getScreenInfo :: Display -> IO [Rectangle]

The xinerama* functions are as direct as possible wrappers around their
C equivalents. getScreenInfo is a helpful wrapper around
xineramaQueryScreens that fakes out a single display when Xinerama is
not active. (That's right: Even if the X11 servers supports Xienrama, if
it's not currently being used, all the Xinerama-functions fail. Yay.)

So the upshot of this is, if we do autoconfig magic (which I think we
probably should do), we can only export getScreenInfo and forget about
providing a low-level interface to Xinerama. I do not think this is a
major concern. The other functions are fairly useless: xineramaIsActive
does what you'd expect, xineramaQueryExtension returns X11 extension
numbers, which I think would only be useful for low-level X11
programming, and xineramaQueryVersion returns the major and minor
version numbers of the Xinerama protocol being used.

Again, I do not see these as major issues. Xmonad only uses
getScreenInfo, and I don't know of anybody else that even uses the
Xinerama wrapper. If, in the future, somebody comes up with a valid use
case for them, we can cross that bridge when we come to it.

So if nobody objects, I'm going to continue to work on autoconfig magic
to make a "getScreenInfo" that works even in the face of non-existent
Xinerama.

Jason Creighton