101 lines
4.1 KiB
EmacsLisp
101 lines
4.1 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
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;; content of the current buffer both horizontally and vertically.
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;;; Code:
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(require 'face-remap)
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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--original-header-line-format nil
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"Stores the original `header-line-format` to restore upon disabling.")
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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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(defvar-local center-content--header-line-face-remap-cookie nil
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"Cookie for the face remapping of `header-line`.")
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(defun center-content--content-pixel-size ()
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"Return the size of the content of the visible text in pixels."
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(window-text-pixel-size (selected-window) (window-start) (window-end)))
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(defun center-content--calculate-left-margin (content-width)
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"Calculate the left margin relative to CONTENT-WIDTH."
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(let ((window-width (window-pixel-width))
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(column-width (string-pixel-width " ")))
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(/ (max 0 (- window-width content-width)) (* 2 column-width))))
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(defun center-content--calculate-top-margin (content-height)
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"Calculate the top margin relative to CONTENT-HEIGHT."
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(let ((window-height (window-pixel-height))
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(line-height (default-line-height)))
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(/ (max 0 (- window-height content-height)) (* 2 line-height))))
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(defun center-content--enable ()
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"Enable horizontal and vertical centering of content."
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(let* ((content-size (center-content--content-pixel-size))
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(left-margin (center-content--calculate-left-margin (car content-size)))
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(top-margin (center-content--calculate-top-margin (cdr content-size))))
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;; Apply horizontal centering using overlay
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(let ((overlay (make-overlay (point-min) (point-max))))
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(overlay-put overlay 'line-prefix
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(propertize " " 'display `(space :width ,left-margin)))
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(setq center-content--horizontal-overlay overlay))
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;; Apply vertical centering using header-line-format
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;; Save and remap the header-line face to match the default face
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(setq center-content--original-header-line-format header-line-format)
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(setq center-content--header-line-face-remap-cookie
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(face-remap-add-relative 'header-line 'default))
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(setq header-line-format
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(propertize " " 'display `(height ,top-margin)))
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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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;; Restore the header-line face remapping
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(when center-content--header-line-face-remap-cookie
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(face-remap-remove-relative center-content--header-line-face-remap-cookie)
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(setq center-content--header-line-face-remap-cookie nil))
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;; Restore the header-line-format
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(setq header-line-format center-content--original-header-line-format)
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(setq center-content--original-mode-line-format 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-header-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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