# X.org

The Nix expressions for the X.org packages reside in `pkgs/servers/x11/xorg/default.nix`. This file is automatically generated from lists of tarballs in an X.org release. As such it should not be modified directly; rather, you should modify the lists, the generator script or the file `pkgs/servers/x11/xorg/overrides.nix`, in which you can override or add to the derivations produced by the generator.

The generator is invoked as follows:

    $ cd pkgs/servers/x11/xorg
    $ cat tarballs-7.5.list extra.list old.list \
      | perl ./generate-expr-from-tarballs.pl

For each of the tarballs in the `.list` files, the script downloads it, unpacks it, and searches its `configure.ac` and `*.pc.in` files for dependencies. This information is used to generate `default.nix`. The generator caches downloaded tarballs between runs. Pay close attention to the `NOT FOUND: name` messages at the end of the run, since they may indicate missing dependencies. (Some might be optional dependencies, however.)

A file like `tarballs-7.5.list` contains all tarballs in a X.org release. It can be generated like this:

    $ export i="mirror://xorg/X11R7.4/src/everything/"
    $ cat $(PRINT_PATH=1 nix-prefetch-url $i | tail -n 1) \
      | perl -e 'while (<>) { if (/(href|HREF)="([^"]*.bz2)"/) { print "$ENV{'i'}$2\n"; }; }' \
      | sort > tarballs-7.4.list

`extra.list` contains libraries that aren’t part of X.org proper, but are closely related to it, such as `libxcb`. `old.list` contains some packages that were removed from X.org, but are still needed by some people or by other packages (such as `imake`).

If the expression for a package requires derivation attributes that the generator cannot figure out automatically (say, `patches` or a `postInstall` hook), you should modify `pkgs/servers/x11/xorg/overrides.nix`.