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TEC 2021-09-15 17:38:12 +08:00
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#+title: pdftotext.el
#+author: tecosaur
Sometimes it would be nice to treat a PDF as a text buffer, so you can do
fancier searches etc. than =pdf-tools= would allow for. Other times, you may be
limited to a terminal (e.g. Emacs over ssh), and want to peek at a PDF.
In both cases, =pdftotext= can be rather helpful. This package just provides a
mode that makes use of it. You'll also need =fmt= for line re-wrapping.

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;;; pdftotext.el --- View PDFs as text using pdftotext and fmt -*- lexical-binding: t; -*-
;;
;; Copyright (C) 2021 TEC
;;
;; Author: TEC <https://github.com/tecosaur>
;; Maintainer: TEC <tec@tecosaur.com>
;; Created: September 15, 2021
;; Modified: September 15, 2021
;; Version: 0.0.1
;; Keywords: convenience tools
;; Homepage: https://github.com/tecosaur/pdftotext
;; Package-Requires: ((emacs "27.1"))
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;;
;; View PDFs as text using pdftotext and fmt.
;;
;;; Code:
(defun pdftotext--update (&optional _window)
(when (eq major-mode 'pdftotext-mode)
(let* ((converted-file
(expand-file-name
(concat
(file-name-base buffer-file-name)
"-"
(substring (secure-hash 'md5 (expand-file-name buffer-file-name)) 0 6)
".txt")
temporary-file-directory))
(width (number-to-string (- (min (window-width) fill-column)
(if display-line-numbers display-line-numbers-width 0))))
(width-adjusted-file (concat (file-name-sans-extension converted-file) "-w" width ".txt")))
(unless (and (file-exists-p converted-file)
(> (time-convert (file-attribute-modification-time (file-attributes converted-file)) 'integer)
(time-convert (file-attribute-modification-time (file-attributes buffer-file-name)) 'integer)))
(call-process "pdftotext" nil nil nil "-layout" "-eol" "unix" buffer-file-name converted-file))
(unless (and (file-exists-p width-adjusted-file)
(>= (time-convert (file-attribute-modification-time (file-attributes width-adjusted-file)) 'integer)
(time-convert (file-attribute-modification-time (file-attributes converted-file)) 'integer)))
(call-process "fmt" nil (list :file width-adjusted-file) nil "-w" width converted-file))
(unless (and (boundp 'pdftotext--file)
(string= pdftotext--file width-adjusted-file))
(let ((pos (when (boundp 'pdftotext--file) (pdftotext--position-info))))
(with-silent-modifications
(let ((inhibit-read-only t)
(coding-system-for-read 'utf-8))
(erase-buffer)
(insert-file-contents width-adjusted-file)
(while (re-search-forward "\n?\f\n?" nil t)
(replace-match "\n\f\n"))
(goto-char (point-min)))
(setq-local pdftotext--file width-adjusted-file))
(setq-default saved-pos pos)
(when pos (ignore-errors (pdftotext--goto-pos pos))))))))
;; The mode uses so-long to reduce the initial buffer load time
;; however it feels like there should be a better solution?
;;;###autoload
(define-derived-mode pdftotext-mode so-long-mode "PDF Text"
"Major mode for viewing the plaintext version of a PDF."
(set-buffer-multibyte t)
(read-only-mode t)
(add-hook 'before-save-hook (lambda () (user-error "Will not overwrite PDF with plaintext version")))
(dolist (hook '(window-configuration-change-hook
window-size-change-functions
display-line-numbers-mode-hook))
(add-hook hook 'pdftotext--update))
(pdftotext--update)
(text-mode)
(setq mode-name "PDF Text"))
;; In `pdftotext--update' there's mention of position saving and
;; restoring. This needs to be implemented, and it's a bit difficult since the line
;; numbers and buffer positions are liable to change. So, instead we can try to
;; take note of some markers (such as the line breaks) and try to make our way to
;; them.
;; Unfortunately while in isolated testing this position restoring works well, for
;; some reason as it's currently used it doesn't seem to work at all.
(defun pdftotext--position-info ()
(list :page-no (let ((current-point (point))
(page-no 0))
(save-excursion
(while (search-forward "\f" current-point t)
(setq page-no (1+ page-no))))
page-no)
:par-start (save-excursion
(forward-paragraph -1)
(forward-line 1)
(thing-at-point 'line t))
:previous-line-content (save-excursion
(forward-line -1)
(thing-at-point 'line t))))
(defun pdftotext--goto-pos (pos)
(goto-char (point-min))
(search-forward "\f" nil nil (plist-get pos :page-no))
(re-search-forward (replace-regexp-in-string " +" "[ \n]+" (regexp-quote (plist-get pos :par-start))))
(unless (string= (plist-get pos :par-start)
(plist-get pos :previous-line-content))
(re-search-forward (replace-regexp-in-string " +" "[ \n]+" (regexp-quote (plist-get pos :previous-line-content)))
(save-excursion (forward-paragraph 1) (point)))))
(defconst pdftotext-auto-mode-alist-entry
'("\\.[pP][dD][fF]\\'" . pdftotext-mode)
"The entry to use for `auto-mode-alist'.")
(defconst pdftotext-magic-mode-alist-entry
'("%PDF" . pdftotext-mode)
"The entry to use for `magic-mode-alist'.")
;;;###autoload
(defun pdftotext-install ()
"Add a \".pdf\" associaton for all future buffers."
(interactive)
(add-to-list 'auto-mode-alist pdftotext-auto-mode-alist-entry)
(add-to-list 'magic-mode-alist pdftotext-magic-mode-alist-entry)
(when (featurep 'pdf-tools)
(setq-default auto-mode-alist
(remove pdf-tools-auto-mode-alist-entry auto-mode-alist))
(setq-default magic-mode-alist
(remove pdf-tools-magic-mode-alist-entry magic-mode-alist))))
(defun pdftotext-uninstall ()
"Remove the \".pdf\" associaton for all future buffers."
(interactive)
(setq-default auto-mode-alist
(remove pdftotext-auto-mode-alist-entry auto-mode-alist))
(setq-default magic-mode-alist
(remove pdftotext-magic-mode-alist-entry auto-mode-alist)))
(provide 'pdftotext)
;;; pdftotext.el ends here