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diff --git a/nixos/modules/services/editors/emacs.md b/nixos/modules/services/editors/emacs.md new file mode 100644 index 000000000000..c072b3664ad1 --- /dev/null +++ b/nixos/modules/services/editors/emacs.md @@ -0,0 +1,399 @@ +# Emacs {#module-services-emacs} + +<!-- + Documentation contributors: + Damien Cassou @DamienCassou + Thomas Tuegel @ttuegel + Rodney Lorrimar @rvl + Adam Hoese @adisbladis + --> + +[Emacs](https://www.gnu.org/software/emacs/) is an +extensible, customizable, self-documenting real-time display editor — and +more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp +programming language with extensions to support text editing. + +Emacs runs within a graphical desktop environment using the X Window System, +but works equally well on a text terminal. Under +macOS, a "Mac port" edition is available, which +uses Apple's native GUI frameworks. + +Nixpkgs provides a superior environment for +running Emacs. It's simple to create custom builds +by overriding the default packages. Chaotic collections of Emacs Lisp code +and extensions can be brought under control using declarative package +management. NixOS even provides a +{command}`systemd` user service for automatically starting the Emacs +daemon. + +## Installing Emacs {#module-services-emacs-installing} + +Emacs can be installed in the normal way for Nix (see +[](#sec-package-management)). In addition, a NixOS +*service* can be enabled. + +### The Different Releases of Emacs {#module-services-emacs-releases} + +Nixpkgs defines several basic Emacs packages. +The following are attributes belonging to the {var}`pkgs` set: + + {var}`emacs` + : The latest stable version of Emacs using the [GTK 2](http://www.gtk.org) + widget toolkit. + + {var}`emacs-nox` + : Emacs built without any dependency on X11 libraries. + + {var}`emacsMacport` + : Emacs with the "Mac port" patches, providing a more native look and + feel under macOS. + +If those aren't suitable, then the following imitation Emacs editors are +also available in Nixpkgs: +[Zile](https://www.gnu.org/software/zile/), +[mg](http://homepage.boetes.org/software/mg/), +[Yi](http://yi-editor.github.io/), +[jmacs](https://joe-editor.sourceforge.io/). + +### Adding Packages to Emacs {#module-services-emacs-adding-packages} + +Emacs includes an entire ecosystem of functionality beyond text editing, +including a project planner, mail and news reader, debugger interface, +calendar, and more. + +Most extensions are gotten with the Emacs packaging system +({file}`package.el`) from +[Emacs Lisp Package Archive (ELPA)](https://elpa.gnu.org/), +[MELPA](https://melpa.org/), +[MELPA Stable](https://stable.melpa.org/), and +[Org ELPA](http://orgmode.org/elpa.html). Nixpkgs is +regularly updated to mirror all these archives. + +Under NixOS, you can continue to use +`package-list-packages` and +`package-install` to install packages. You can also +declare the set of Emacs packages you need using the derivations from +Nixpkgs. The rest of this section discusses declarative installation of +Emacs packages through nixpkgs. + +The first step to declare the list of packages you want in your Emacs +installation is to create a dedicated derivation. This can be done in a +dedicated {file}`emacs.nix` file such as: + +[]{#ex-emacsNix} + +```nix +/* +This is a nix expression to build Emacs and some Emacs packages I like +from source on any distribution where Nix is installed. This will install +all the dependencies from the nixpkgs repository and build the binary files +without interfering with the host distribution. + +To build the project, type the following from the current directory: + +$ nix-build emacs.nix + +To run the newly compiled executable: + +$ ./result/bin/emacs +*/ + +# The first non-comment line in this file indicates that +# the whole file represents a function. +{ pkgs ? import <nixpkgs> {} }: + +let + # The let expression below defines a myEmacs binding pointing to the + # current stable version of Emacs. This binding is here to separate + # the choice of the Emacs binary from the specification of the + # required packages. + myEmacs = pkgs.emacs; + # This generates an emacsWithPackages function. It takes a single + # argument: a function from a package set to a list of packages + # (the packages that will be available in Emacs). + emacsWithPackages = (pkgs.emacsPackagesFor myEmacs).emacsWithPackages; +in + # The rest of the file specifies the list of packages to install. In the + # example, two packages (magit and zerodark-theme) are taken from + # MELPA stable. + emacsWithPackages (epkgs: (with epkgs.melpaStablePackages; [ + magit # ; Integrate git <C-x g> + zerodark-theme # ; Nicolas' theme + ]) + # Two packages (undo-tree and zoom-frm) are taken from MELPA. + ++ (with epkgs.melpaPackages; [ + undo-tree # ; <C-x u> to show the undo tree + zoom-frm # ; increase/decrease font size for all buffers %lt;C-x C-+> + ]) + # Three packages are taken from GNU ELPA. + ++ (with epkgs.elpaPackages; [ + auctex # ; LaTeX mode + beacon # ; highlight my cursor when scrolling + nameless # ; hide current package name everywhere in elisp code + ]) + # notmuch is taken from a nixpkgs derivation which contains an Emacs mode. + ++ [ + pkgs.notmuch # From main packages set + ]) +``` + +The result of this configuration will be an {command}`emacs` +command which launches Emacs with all of your chosen packages in the +{var}`load-path`. + +You can check that it works by executing this in a terminal: +```ShellSession +$ nix-build emacs.nix +$ ./result/bin/emacs -q +``` +and then typing `M-x package-initialize`. Check that you +can use all the packages you want in this Emacs instance. For example, try +switching to the zerodark theme through `M-x load-theme <RET> zerodark <RET> y`. + +::: {.tip} +A few popular extensions worth checking out are: auctex, company, +edit-server, flycheck, helm, iedit, magit, multiple-cursors, projectile, +and yasnippet. +::: + +The list of available packages in the various ELPA repositories can be seen +with the following commands: +[]{#module-services-emacs-querying-packages} +``` +nix-env -f "<nixpkgs>" -qaP -A emacs.pkgs.elpaPackages +nix-env -f "<nixpkgs>" -qaP -A emacs.pkgs.melpaPackages +nix-env -f "<nixpkgs>" -qaP -A emacs.pkgs.melpaStablePackages +nix-env -f "<nixpkgs>" -qaP -A emacs.pkgs.orgPackages +``` + +If you are on NixOS, you can install this particular Emacs for all users by +adding it to the list of system packages (see +[](#sec-declarative-package-mgmt)). Simply modify your file +{file}`configuration.nix` to make it contain: +[]{#module-services-emacs-configuration-nix} +``` +{ + environment.systemPackages = [ + # [...] + (import /path/to/emacs.nix { inherit pkgs; }) + ]; +} +``` + +In this case, the next {command}`nixos-rebuild switch` will take +care of adding your {command}`emacs` to the {var}`PATH` +environment variable (see [](#sec-changing-config)). + +<!-- fixme: i think the following is better done with config.nix +https://nixos.org/nixpkgs/manual/#sec-modify-via-packageOverrides +--> + +If you are not on NixOS or want to install this particular Emacs only for +yourself, you can do so by adding it to your +{file}`~/.config/nixpkgs/config.nix` (see +[Nixpkgs manual](https://nixos.org/nixpkgs/manual/#sec-modify-via-packageOverrides)): +[]{#module-services-emacs-config-nix} +``` +{ + packageOverrides = super: let self = super.pkgs; in { + myemacs = import /path/to/emacs.nix { pkgs = self; }; + }; +} +``` + +In this case, the next `nix-env -f '<nixpkgs>' -iA +myemacs` will take care of adding your emacs to the +{var}`PATH` environment variable. + +### Advanced Emacs Configuration {#module-services-emacs-advanced} + +If you want, you can tweak the Emacs package itself from your +{file}`emacs.nix`. For example, if you want to have a +GTK 3-based Emacs instead of the default GTK 2-based binary and remove the +automatically generated {file}`emacs.desktop` (useful if you +only use {command}`emacsclient`), you can change your file +{file}`emacs.nix` in this way: + +[]{#ex-emacsGtk3Nix} +``` +{ pkgs ? import <nixpkgs> {} }: +let + myEmacs = (pkgs.emacs.override { + # Use gtk3 instead of the default gtk2 + withGTK3 = true; + withGTK2 = false; + }).overrideAttrs (attrs: { + # I don't want emacs.desktop file because I only use + # emacsclient. + postInstall = (attrs.postInstall or "") + '' + rm $out/share/applications/emacs.desktop + ''; + }); +in [...] +``` + +After building this file as shown in [the example above](#ex-emacsNix), you +will get an GTK 3-based Emacs binary pre-loaded with your favorite packages. + +## Running Emacs as a Service {#module-services-emacs-running} + +NixOS provides an optional +{command}`systemd` service which launches +[Emacs daemon](https://www.gnu.org/software/emacs/manual/html_node/emacs/Emacs-Server.html) +with the user's login session. + +*Source:* {file}`modules/services/editors/emacs.nix` + +### Enabling the Service {#module-services-emacs-enabling} + +To install and enable the {command}`systemd` user service for Emacs +daemon, add the following to your {file}`configuration.nix`: +``` +services.emacs.enable = true; +services.emacs.package = import /home/cassou/.emacs.d { pkgs = pkgs; }; +``` + +The {var}`services.emacs.package` option allows a custom +derivation to be used, for example, one created by +`emacsWithPackages`. + +Ensure that the Emacs server is enabled for your user's Emacs +configuration, either by customizing the {var}`server-mode` +variable, or by adding `(server-start)` to +{file}`~/.emacs.d/init.el`. + +To start the daemon, execute the following: +```ShellSession +$ nixos-rebuild switch # to activate the new configuration.nix +$ systemctl --user daemon-reload # to force systemd reload +$ systemctl --user start emacs.service # to start the Emacs daemon +``` +The server should now be ready to serve Emacs clients. + +### Starting the client {#module-services-emacs-starting-client} + +Ensure that the emacs server is enabled, either by customizing the +{var}`server-mode` variable, or by adding +`(server-start)` to {file}`~/.emacs`. + +To connect to the emacs daemon, run one of the following: +``` +emacsclient FILENAME +emacsclient --create-frame # opens a new frame (window) +emacsclient --create-frame --tty # opens a new frame on the current terminal +``` + +### Configuring the {var}`EDITOR` variable {#module-services-emacs-editor-variable} + +<!--<title>{command}`emacsclient` as the Default Editor</title>--> + +If [](#opt-services.emacs.defaultEditor) is +`true`, the {var}`EDITOR` variable will be set +to a wrapper script which launches {command}`emacsclient`. + +Any setting of {var}`EDITOR` in the shell config files will +override {var}`services.emacs.defaultEditor`. To make sure +{var}`EDITOR` refers to the Emacs wrapper script, remove any +existing {var}`EDITOR` assignment from +{file}`.profile`, {file}`.bashrc`, +{file}`.zshenv` or any other shell config file. + +If you have formed certain bad habits when editing files, these can be +corrected with a shell alias to the wrapper script: +``` +alias vi=$EDITOR +``` + +### Per-User Enabling of the Service {#module-services-emacs-per-user} + +In general, {command}`systemd` user services are globally enabled +by symlinks in {file}`/etc/systemd/user`. In the case where +Emacs daemon is not wanted for all users, it is possible to install the +service but not globally enable it: +``` +services.emacs.enable = false; +services.emacs.install = true; +``` + +To enable the {command}`systemd` user service for just the +currently logged in user, run: +``` +systemctl --user enable emacs +``` +This will add the symlink +{file}`~/.config/systemd/user/emacs.service`. + +## Configuring Emacs {#module-services-emacs-configuring} + +The Emacs init file should be changed to load the extension packages at +startup: +[]{#module-services-emacs-package-initialisation} +``` +(require 'package) + +;; optional. makes unpure packages archives unavailable +(setq package-archives nil) + +(setq package-enable-at-startup nil) +(package-initialize) +``` + +After the declarative emacs package configuration has been tested, +previously downloaded packages can be cleaned up by removing +{file}`~/.emacs.d/elpa` (do make a backup first, in case you +forgot a package). + +<!-- + todo: is it worth documenting customizations for + server-switch-hook, server-done-hook? + --> + +### A Major Mode for Nix Expressions {#module-services-emacs-major-mode} + +Of interest may be {var}`melpaPackages.nix-mode`, which +provides syntax highlighting for the Nix language. This is particularly +convenient if you regularly edit Nix files. + +### Accessing man pages {#module-services-emacs-man-pages} + +You can use `woman` to get completion of all available +man pages. For example, type `M-x woman <RET> nixos-rebuild <RET>.` + +### Editing DocBook 5 XML Documents {#sec-emacs-docbook-xml} + +Emacs includes +[nXML](https://www.gnu.org/software/emacs/manual/html_node/nxml-mode/Introduction.html), +a major-mode for validating and editing XML documents. When editing DocBook +5.0 documents, such as [this one](#book-nixos-manual), +nXML needs to be configured with the relevant schema, which is not +included. + +To install the DocBook 5.0 schemas, either add +{var}`pkgs.docbook5` to [](#opt-environment.systemPackages) +([NixOS](#sec-declarative-package-mgmt)), or run +`nix-env -f '<nixpkgs>' -iA docbook5` +([Nix](#sec-ad-hoc-packages)). + +Then customize the variable {var}`rng-schema-locating-files` to +include {file}`~/.emacs.d/schemas.xml` and put the following +text into that file: +[]{#ex-emacs-docbook-xml} +```xml +<?xml version="1.0"?> +<!-- + To let emacs find this file, evaluate: + (add-to-list 'rng-schema-locating-files "~/.emacs.d/schemas.xml") +--> +<locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0"> + <!-- + Use this variation if pkgs.docbook5 is added to environment.systemPackages + --> + <namespace ns="http://docbook.org/ns/docbook" + uri="/run/current-system/sw/share/xml/docbook-5.0/rng/docbookxi.rnc"/> + <!-- + Use this variation if installing schema with "nix-env -iA pkgs.docbook5". + <namespace ns="http://docbook.org/ns/docbook" + uri="../.nix-profile/share/xml/docbook-5.0/rng/docbookxi.rnc"/> + --> +</locatingRules> +``` |