Internal concepts
A buffer contains text to display on screen, and might be associated to a file, but might not be.
Buffers are regular CLOS objects with many slots:
name
temporary (boolean)
filename
directory
read-only-p
major-mode
minor-modes
point
last-write-date
…
A text-buffer is a class and type for text buffers.
The variable *current-buffer* holds the current buffer, the one we
are visiting in Lem. There will always be at least one buffer, even if
it is the primordial one named *tmp*.
We don’t directly access a buffer’s slots, but we use small wrapper functions, such as:
buffer-name
buffer-filename
buffer-directory
…
They are setf-able, and work by default on the current-buffer.
Other manipulation functions include:
(current-buffer)
(ensure-buffer)
(get-buffer)
;; If 'buffer-or-name' is a buffer, it is returned. If it is a string, it returns the buffer with that name.
See:
See:
(buffer-list)
(delete-buffer)
(get-next-buffer)
(get-previous-buffer)
(defun get-file-buffer (filename)
;; "Return the buffer corresponding to 'filename' or NIL if not found."
etc
A buffer object might hold any other data in its variables slot (to
get with buffer-variables), a hash-table that associates a variable
key to its values.
The function buffer-value buffer name &optional default is used to
access these variables. It is setf-able.
This feature attaches “attached-window” to the bottom of a specific window. An “attached-window” has an “attached-buffer”. When you attach an attached-window to a specific window, that window becomes the parent window from the perspective of the attached-window. The attached window remains visible even when the parent window is scrolled.
It’s like a comment input form on slack or discord.
They were initially added for the Claude Code integration.
The point is the cursor’s location.
You may use these functions:
(current-point)
(copy-point)
(point=) ;; and other comparison functions
(point-max)
(move-point point new-point)
The macro (save-excursion …) will run its body and preserve the
point position from before the macro was called.
(save-excursion
(move-point (current-point) point)
(prompt-for-string
"Say hi: "))
See:
Each created point creates an object in memory. After being used, a
point should be discarded. You can use make-point and
delete-point, or use the macro with-point.
(with-point ((p3 expr1)
(p1 expr2 :left-inserting)
(p2 expr3 :right-inserting))
...)
Prompts are these interactive pop-up windows that allow you to search and TAB-complete commands, files, etc.
Some prompt functions are already defined for a diversity of use-cases:
prompt-for-y-or-n-p
prompt-for-string
prompt-for-integer
prompt-for-buffer
prompt-for-file
prompt-for-directory
prompt-for-command
prompt-for-library
prompt-for-encodings
Each may define a prompt string, an initial value, a completion
function, a :test-function (as in the Lisp built-ins :test key
parameter), and a history-symbol
Their signature are usually:
(prompt-for-string string
:initial-value string
:history-symbol '*symbol*
:completion-function #'function
:test-function #'function)
See:
This is enough to prompt for a string:
(prompt-for-string "New string: ")
A use in the wild might look like:
(prompt-for-string (or prompt "Branch: ")
:initial-value current-branch
:history-symbol '*legit-branches-history*
:completion-function (lambda (x) (completion-strings x candidates))
:test-function (lambda (name) (member name candidates :test #'string=)))
We may use prompts that open at the current point, on the current line, and have no borders: they are not a pop-up window.
;; in directory-mode
(defun prompt-for-rename-file (point)
"Open an inlined prompt at point to rename the file."
(let ((file (current-file point)))
(save-excursion
(move-point (current-point) point)
(prompt-for-string
"New name: "
:initial-value (if file (file-namestring file) "")
:test-function (lambda (string)
(not (alexandria:emptyp string)))
:gravity :cursor
:use-border nil))))