101 lines
4.2 KiB
EmacsLisp
101 lines
4.2 KiB
EmacsLisp
;;; center-content.el --- Center buffer content horizontally and vertically -*- lexical-binding: t; -*-
|
|
|
|
;;; Commentary:
|
|
|
|
;; This package provides a minor mode `center-content-mode` that centers the visible content
|
|
;; of the current buffer both horizontally and vertically. It calculates the necessary margins
|
|
;; and applies them using overlays and header line adjustments. The mode line is hidden to
|
|
;; provide a clean appearance.
|
|
|
|
;;; Code:
|
|
|
|
(defvar-local center-content--horiz-overlay nil
|
|
"Overlay used by `center-content-mode` to add left margin for horizontal centering.")
|
|
|
|
(defvar-local center-content--original-header-line-format nil
|
|
"Stores the original `header-line-format` to restore upon disabling.")
|
|
|
|
(defvar-local center-content--original-mode-line-format nil
|
|
"Stores the original `mode-line-format` to restore upon disabling.")
|
|
|
|
(defface center-content-header-line
|
|
`((t (:inherit default
|
|
:background ,(face-background 'default nil t)
|
|
:foreground ,(face-foreground 'default nil t))))
|
|
"Face for the header line in `center-content-mode`."
|
|
:group 'center-content)
|
|
|
|
(defun center-content--calculate-left-margin ()
|
|
"Calculate the left margin needed to center the content horizontally."
|
|
(let* ((window (selected-window))
|
|
(window-width (window-pixel-width window))
|
|
(content-width (car (window-text-pixel-size
|
|
window
|
|
(window-start window)
|
|
(window-end window))))
|
|
(space-width (string-pixel-width " "))
|
|
(margin (/ (max 0 (- window-width content-width)) (* 2 space-width))))
|
|
margin))
|
|
|
|
(defun center-content--calculate-top-margin ()
|
|
"Calculate the top margin needed to center the content vertically."
|
|
(let* ((window-height (window-pixel-height))
|
|
(content-height (cdr (window-text-pixel-size)))
|
|
(margin (/ (max 0 (- window-height content-height)) 2)))
|
|
margin))
|
|
|
|
(defun center-content--enable ()
|
|
"Enable horizontal and vertical centering of content."
|
|
(let ((left-margin (center-content--calculate-left-margin))
|
|
(top-margin (center-content--calculate-top-margin)))
|
|
;; Apply horizontal centering using overlay
|
|
(let ((horiz-overlay (make-overlay (point-min) (point-max))))
|
|
(overlay-put horiz-overlay 'line-prefix
|
|
(propertize " " 'display `(space :width ,left-margin)))
|
|
(setq center-content--horiz-overlay horiz-overlay))
|
|
;; Save the original header-line-format
|
|
(setq center-content--original-header-line-format header-line-format)
|
|
;; Apply vertical centering using header-line-format with custom face
|
|
(setq header-line-format
|
|
(propertize " "
|
|
'display `(height ,(max 0 (/ top-margin (frame-char-height))))
|
|
'face 'center-content-header-line))
|
|
;; Save the original mode-line-format
|
|
(setq center-content--original-mode-line-format mode-line-format)
|
|
;; Hide the mode line
|
|
(setq mode-line-format nil)))
|
|
|
|
(defun center-content--disable ()
|
|
"Disable centering of content."
|
|
;; Remove horizontal centering overlay
|
|
(when (overlayp center-content--horiz-overlay)
|
|
(delete-overlay center-content--horiz-overlay)
|
|
(setq center-content--horiz-overlay nil))
|
|
;; Restore the original header-line-format
|
|
(setq header-line-format center-content--original-header-line-format)
|
|
(setq center-content--original-header-line-format nil)
|
|
;; Restore the original mode-line-format
|
|
(setq mode-line-format center-content--original-mode-line-format)
|
|
(setq center-content--original-mode-line-format nil)
|
|
;; Force redisplay to remove any lingering effects
|
|
(force-mode-line-update)
|
|
(redisplay))
|
|
|
|
;;;###autoload
|
|
(define-minor-mode center-content-mode
|
|
"Toggle horizontal and vertical centering of buffer content.
|
|
|
|
When enabled, the visible content of the buffer is centered both
|
|
horizontally and vertically within the window. The mode line is
|
|
hidden for a clean appearance."
|
|
:init-value nil
|
|
:global nil
|
|
:lighter nil ;; Remove the lighter to keep the mode line clean
|
|
(if center-content-mode
|
|
(center-content--enable)
|
|
(center-content--disable)))
|
|
|
|
(provide 'center-content)
|
|
|
|
;;; center-content.el ends here
|