Modern Emacs

New tools that make Emacs better and faster

Marie-Hélène Burle

March 5, 2024

Faster Emacs

Lexical binding

Introduced in version 24
Lexical binding can be used instead of dynamic binding for Emacs Lisp code
Set as a file local variable

Dynamic binding

Name resolution depends on program state (runtime context), determined at run time
Global environment for all variables

Makes modifying behaviour easy

Lexical binding

Name resolution depends on lexical context (static context), determined at compile time
Local environments of functions and let, defconst, defvar, etc. expressions

Makes compiler optimization much easier → faster Elisp code = faster Emacs

JIT native compilation

Introduced in version 28
Requires libgccjit
Build Emacs --with-native-compilation
Packages can also be compiled natively (automatic with straight)

Faster startup
Speedup of 2.5 to 5 compared to corresponding byte-compiled code

Lazy loading

Built-in since version 29
Fine-tuned loading of packages with use-package
Integrates nicely with straight

Faster startup time
More organized init file
Easier to reload configurations for single package

Perfect parsing

Accurate syntax tree

Built-in since version 29
Tree-sitter for Emacs
Code is parsed accurately instead of using regexp

Perfect syntax highlighting, indentation, and navigation
Faster

Simplest setup with treesit-auto:

(use-package treesit-auto
  :config
  (treesit-auto-add-to-auto-mode-alist 'all))

More efficient completions

History of code completion in Emacs: IDO

History of code completion in Emacs: IDO vertical

History of code completion in Emacs: HELM

History of code completion in Emacs: Ivy

With optional Counsel & Swiper

New framework

External packages
Use default Emacs functions (less code)
Faster, flexible, customizable with discrete units

Packages

Minibuffer

vertico frontend completion UI
orderless backend completion style
consult backend completion functions
marginalia annotations
embark actions on completion buffer

In buffer

corfu frontend completion UI
orderless backend completion style
cape backend completion functions
eglot backend LSP client

Compared to previous frameworks

Integrates beautifully with internal Emacs functions
Easy jump back & forth between buffer and completion buffer
Much faster than HELM
Lightning fast previews with auto-closing buffers
Easy customization

Example configuration

Vertico (frontend for completion in minibuffer)

(use-package vertico
  :init
  (vertico-mode 1)
  (vertico-multiform-mode 1)
  :config
  (setq vertico-multiform-commands
    '((consult-line buffer)
      (consult-line-thing-at-point buffer)
      (consult-recent-file buffer)
      (consult-mode-command buffer)
      (consult-complex-command buffer)
      (embark-bindings buffer)
      (consult-locate buffer)
      (consult-project-buffer buffer)
      (consult-ripgrep buffer)
      (consult-fd buffer)))
  :bind (:map vertico-map
          ("C-k" . kill-whole-line)
          ("C-u" . kill-whole-line)
          ("C-o" . vertico-next-group)
          ("<tab>" . minibuffer-complete)
          ("M-<return>" . minibuffer-force-complete-and-exit)))

;; save search history
(use-package savehist
  :init
  (savehist-mode 1))

Language Server Protocol client

Built-in since version 29

Eglot (Emacs Polyglot) allows to connect to a programming language server

Example: Julia

Need to install an LSP for Julia:

(straight-use-package 'eglot-jl)

Then run eglot-jl-init

Now eglot in a Julia buffer connects to the server

Similarly, you can install an LSP for R or Python or any language and use Eglot with R, Python, or whatever language

❤ to all Emacs developers and maintainers

In particular,

developers, maintainers, and contributors to Emacs core,
developers and maintainers to some of the mentioned packages:
Daniel Mendler
Omar Antolín Camarena
João Távora
Robb Enzmann
John Wiegley
Adam B
and all their contributors