Keybindings

The documentation is in progress. You can find a list of available keys and commands in default-keybindings.md, and you can get this list in Lem itself with M-x documentation-describe-bindings (new after Lem 2.0).

Lem has Emacs-like keybindings, as well as a vi emulation (M-x vi-mode).

So, to open a file, press C-x C-f (you get the file selection dialog shown above). To save it, it’s C-x C-s. To save many buffers at once, use C-x s.

To switch windows (aka splits of a screen): C-x o (‘o’ letter) and M-o. To make a window fullscreen: C-x 1. To split it vertically: C-x 3 and horizontally: C-x 2. To make the current window disappear: C-x 0 (zero).

To switch buffers: C-x b.

To run an interactive command by name: M-x (alt-x).

To show the context menu: Shift-F10.

Quit Lem with C-x C-c.

See this Emacs & Slime cheatsheet to find more: https://lispcookbook.github.io/cl-cookbook/emacs-ide.html#appendix

The command find-file-recursively, added after Lem 2.0, is not bound to a key by default. This command opens a selection prompt and lists all files under the buffer’s directory, recursively, letting you choose and open a file deep in the directory tree quickly.

The method to search all files recursively is configurable. Lem first tries with any of these external programs: fd, fdfind (which is fd installed from Debian repositories) and find (the Unix find). If none of these programs exist, it falls back to a Lisp version.

fd is an external tool, that is fast and that filters out some directories by default: “node_modules/”, “.git/” and such. The Lisp method doesn’t exclude them.

But what happens if you call this command on your HOME, or in a directory with lots and lots of files? The command has a 5 seconds timeout (by default). After that time, the process is aborted and Lem uses the simpler find-file command.

You can bind the command to a keybinding:

(lem:define-key lem:*global-keymap* "C-x F" 'lem-core/commands/file:find-file-recursively)

The variables and methods are inside the Lisp package :lem-core/commands/file.

You can change the order of the finder programs:

;; these must be keywords, not strings.
(setf *find-programs* (list :fdfind :fd :find :lisp))

or choose the one to use:

(setf *find-program* :lisp)

You can change the timeout:

(setf *find-program-timeout* 5)

and change the behaviour of the methods that return the list of files and directories. They are written as CLOS generic methods specializing on the *find-program* keyword, so you can use :before, :around or :after qualifiers.

(defmethod get-files-recursively :around ((finder (eql :lisp)))
  (let ((results (call-next-method)))
     (do-something-with-the-results)))

Use C-x b (aka M-x list-buffers). But don’t stop here, it’s a rich command.

You are presented a “modale” window. Type some text to start narrowing the buffers list matching your entry.

You can also use Space to select/deselect entries, then use a right click to choose an action to apply on the selected buffers. Default actions are to kill the selected buffers, or to save them.

Use M-x vi-mode and M-x emacs-mode.

You can also start Lem in any given, see the configuration section.

Lem has a system of abbreviation that permits to auto-complete any text that was previously entered in any text buffer.

By default, abbrev is bound to M-/

In vi’s insert-mode, it is also bound to C-p.

There is also the command abbrev-with-popup-window that shows the list of completion candidates. It is not bound by default. We can bind it to a key:

;; C-n is originally bound to next-line.
(define-key *global-keymap* "C-n" 'lem/abbrev:abbrev-with-pop-up-window)

and in vi-mode:

;; C-n is originally bound to next-line.
(define-key lem-vi-mode:*insert-keymap* "C-n" 'lem/abbrev:abbrev-with-pop-up-window)

To know what function is bound to a key binding, use C-x ? (M-x describe-key).

To see the available key bindings in the current keymap, use M-x describe-bindings.

You can use M-x describe-mode to understand in which mode the editor is in the current buffer.

You can do more and list all Lem’s existing keybindings with M-x documentation-describe-bindings. It inspects Lem and lists keybindings, grouped by modes:

• move, edit, mark, word, S-expressions, file, buffer, window, multiple-cursors, process, help, font and other.

Note: this command was added after Lem 2.0.

M-x grep

this presents the results in a two-panes window. You can edit lines in the results buffer, changes are reflected immediately on the files, and updated on the right side. You can use search and replace M-x query-replace in the results buffer.

Use M-C (Alt and capital c), M-x add-cursors-to-next-line to add a cursor to the next line.