ladybird/Documentation/EmacsConfiguration.md

Emacs Project Configuration

Emacs can be configured with lsp-mode and clangd to work well.

clangd

The official clangd extension can be used for C++ comprehension. You can use the following .clangd file placed in the project root:

CompileFlags:
  CompilationDatabase: Build/ladybird

Diagnostics:
  UnusedIncludes: None
  MissingIncludes: None

Run cmake (Meta/ladybird.sh run ladybird or similar) at least once for this to work, as it will generate the Build/ladybird/compile_commands.json that is needed by clangd.

lsp-mode

(use-package lsp-mode
  :hook ((c++-mode) . lsp-deferred)
  :commands lsp
  :config
  (setq lsp-clients-clangd-args '("-j=4" "-background-index" "--log=error" "--clang-tidy" "--enable-config"))
  ;; Optionally, set the location of clangd -- See notes below for options.
  (setq lsp-clangd-binary-path "/usr/bin/clangd"))

clangd

There are a few different ways to specify which clangd to use:

• By default, without configuration lsp-mode will try to find and use your system clangd. This is the easiest solution, but your system clangd might be out of date.
• You can manually specify any clangd binary with lsp-clangd-binary-path, as shown in the use-package example above.
• You can have lsp-mode manage your clangd installation with emacs' lsp-install-server. This will install a clangd binary for you.
• You can build the LLVM toolchain, including clangd, from Ladybird's repository. This is an advanced option that is not currently documented.

clang-format

There are multiple packages to handle auto formatting with clang-format, within emacs. Choose what works best for your setup:

• format-all-mode
• clang-format-plus

Alternatively, this can be done without additional packages, using lsp-mode. You can use the following .dir-locals.el file placed in the project root:

((c++-mode
  (eval add-hook 'before-save-hook #'lsp-format-buffer nil t)))