95 lines
3.8 KiB
EmacsLisp
95 lines
3.8 KiB
EmacsLisp
;;; center-content.el --- Center buffer content horizontally and vertically -*- lexical-binding: t; -*-
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;;; Commentary:
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;; This package provides a minor mode `center-content-mode` that centers the content
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;; of the current buffer both horizontally and vertically. It calculates the necessary
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;; margins and applies them using overlays. The mode line is hidden to provide a clean appearance.
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;;; Code:
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(defvar-local center-content--horizontal-overlay nil
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"Overlay used to add left margin for horizontal centering.")
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(defvar-local center-content--vertical-overlay nil
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"Overlay used to add top margin for vertical centering.")
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(defvar-local center-content--original-mode-line-format nil
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"Stores the original `mode-line-format` to restore upon disabling.")
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(defun center-content--calculate-left-margin ()
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"Calculate the left margin needed to center the content horizontally."
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(let* ((window (selected-window))
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(window-width (window-pixel-width window))
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(content-width (car (window-text-pixel-size
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window
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(window-start window)
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(window-end window)))))
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(/ (max 0 (- window-width content-width)) 2)))
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(defun center-content--calculate-top-margin ()
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"Calculate the top margin needed to center the content vertically."
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(let* ((window (selected-window))
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(window-height (window-pixel-height window))
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(content-height (cdr (window-text-pixel-size window)))
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(margin (/ (max 0 (- window-height content-height)) 2)))
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margin))
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(defun center-content--enable ()
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"Enable horizontal and vertical centering of content."
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(let ((left-margin (center-content--calculate-left-margin))
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(top-margin (center-content--calculate-top-margin)))
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;; Apply horizontal centering using overlay
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(let ((horizontal-overlay (make-overlay (point-min) (point-max))))
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(overlay-put horizontal-overlay 'line-prefix
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(propertize " " 'display `(space :width (,left-margin))))
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(setq center-content--horizontal-overlay horizontal-overlay))
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;; Apply vertical centering using a before-string overlay
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(let ((overlay (make-overlay (point-min) (point-min))))
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(overlay-put overlay 'before-string
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(propertize "\n" 'display `(space :height (,top-margin))))
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;; Set low priority to avoid interfering with line-prefix
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(overlay-put overlay 'priority -50)
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(setq center-content--vertical-overlay overlay))
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;; Save and hide the mode line
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(setq center-content--original-mode-line-format mode-line-format)
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(setq mode-line-format nil)
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;; Force redisplay
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(force-mode-line-update)
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(redisplay)))
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(defun center-content--disable ()
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"Disable centering of content."
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;; Remove horizontal centering overlay
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(when (overlayp center-content--horizontal-overlay)
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(delete-overlay center-content--horizontal-overlay)
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(setq center-content--horizontal-overlay nil))
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;; Remove vertical centering overlay
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(when (overlayp center-content--vertical-overlay)
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(delete-overlay center-content--vertical-overlay)
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(setq center-content--vertical-overlay nil))
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;; Restore the original mode-line-format
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(setq mode-line-format center-content--original-mode-line-format)
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(setq center-content--original-mode-line-format nil)
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;; Force redisplay
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(force-mode-line-update)
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(redisplay))
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;;;###autoload
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(define-minor-mode center-content-mode
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"Toggle horizontal and vertical centering of buffer content.
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When enabled, the content of the buffer is centered both
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horizontally and vertically within the window. The mode line is
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hidden for a clean appearance."
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:init-value nil
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:global nil
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:lighter nil ;; Remove the lighter to keep the mode line clean
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(if center-content-mode
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(center-content--enable)
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(center-content--disable)))
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(provide 'center-content)
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;;; center-content.el ends here
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