nixpkgs/doc/builders/packages/xorg.section.md
Corbin 874e3587ee doc/builders/packages/xorg: Use ShellSession for shell.
I was worried, but the HTML output can still be copy-and-pasted, so it's
not a problem.
2020-11-30 22:03:23 -08:00

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# X.org {#sec-xorg}
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.
## Katamari Tarballs
X.org upstream releases used to include [katamari](https://en.wiktionary.org/wiki/%E3%81%8B%E3%81%9F%E3%81%BE%E3%82%8A) releases, which included a holistic recommended version for each tarball, up until 7.7. To create a list of tarballs in a katamari release:
```ShellSession
export release="X11R7.7"
export url="mirror://xorg/$release/src/everything/"
cat $(PRINT_PATH=1 nix-prefetch-url $url | tail -n 1) \
| perl -e 'while (<>) { if (/(href|HREF)="([^"]*.bz2)"/) { print "$ENV{'url'}$2\n"; }; }' \
| sort > "tarballs-$release.list"
```
## Individual Tarballs
The upstream release process for [X11R7.8](https://x.org/wiki/Releases/7.8/) does not include a planned katamari. Instead, each component of X.org is released as its own tarball. We maintain `pkgs/servers/x11/xorg/tarballs.list` as a list of tarballs for each individual package. This list includes X.org core libraries and protocol descriptions, extra newer X11 interface libraries, like `xorg.libxcb`, and classic utilities which are largely unused but still available if needed, like `xorg.imake`.
## Generating Nix Expressions
The generator is invoked as follows:
```ShellSession
cd pkgs/servers/x11/xorg
<tarballs.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.)
## Overriding the Generator
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`.