+;;; ffs.el --- Form Feed Slides mode -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2022 Amin Bandali <bandali@gnu.org>
+
+;; Author: Amin Bandali <bandali@gnu.org>
+;; Version: 0.1.0
+;; Keywords: outlines, tools
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; A simple mode for doing simple plain text presentations where the
+;; slides are separated using the form feed character (\f).
+
+;; Configuration: TODO
+
+;; Usage:
+
+;; Put this file, ffs.el, in a directory in your `load-path', then add
+;; something like the following to your init file:
+;;
+;; (require 'ffs)
+;; (global-set-key (kbd "C-c f s") #'ffs)
+
+;; Then, open a text file/buffer that you would like you to use as the
+;; source of your presentation and type `M-x ffs RET' or a keyboard
+;; shortcut you defined (like the above example) to start ffs, at
+;; which point you should be able to see "ffs" appear as one of the
+;; currently enabled minor modes in your mode-line. Once ffs is
+;; enabled, you can invoke its various commands. To see a list of
+;; available commands, you can either type `M-x ffs- TAB' (to get a
+;; completion of commands starting with the "ffs-" prefix), or see the
+;; definition of `ffs-minor-mode-map' near the end of this file.
+
+;;; Code:
+
+(defgroup ffs nil
+ "Minor mode for form feed-separated plain text presentations."
+ :version "29.1"
+ :prefix "ffs-")
+
+(defcustom ffs-default-face-height 370
+ "The value of the `height' property for the `default' face to use
+during the ffs presentation."
+ :group 'ffs
+ :type '(choice (const nil)
+ (integer :value 300)))
+
+(defcustom ffs-edit-buffer-name "*ffs-edit*"
+ "The name of the ffs-edit buffer used when editing a slide."
+ :group 'ffs
+ :type 'string)
+
+(defvar ffs--slides-buffer nil
+ "The main ffs presentation slides buffer.
+When the user enables ffs in a buffer using `\\[ffs]', we store a
+reference to that buffer in this variable.
+
+As a special case, in a speaker notes buffer selected by the user
+using `\\[ffs-find-speaker-notes-file]' from the main ffs slides
+buffer, this variable will point to the main ffs slides buffer
+rather than the speaker notes buffer.")
+
+(defvar ffs--notes-buffer nil
+ "The ffs speaker notes buffer (only if selected).
+When the user chooses (and opens) a speaker notes file using
+`\\[ffs-find-speaker-notes-file]', a reference to the file's
+corresponding buffer is stored in this variable, local to the
+main ffs presentation slides buffer (`ffs--slides-buffer').")
+
+(defvar ffs--old-mode-line-format nil
+ "The old value of `mode-line-format' before enabling
+`ffs--no-mode-line-minor-mode'.")
+
+(defvar ffs--old-cursor-type nil
+ "The old value of `cursor-type' before enabling
+`ffs--no-cursor-minor-mode'.")
+
+(defvar ffs--old-default-face-height nil
+ "The old value of the `default' face's `height' property before
+starting the ffs presentation.")
+
+(define-minor-mode ffs--no-mode-line-minor-mode
+ "Minor mode for hiding the mode-line."
+ :lighter nil
+ (if ffs--no-mode-line-minor-mode
+ (progn
+ (unless ffs--old-mode-line-format
+ (setq-local ffs--old-mode-line-format mode-line-format))
+ (setq-local mode-line-format nil))
+ (setq-local mode-line-format ffs--old-mode-line-format)
+ (when ffs--old-mode-line-format
+ ffs--old-mode-line-format nil))
+ (redraw-display))
+
+(define-minor-mode ffs--no-cursor-minor-mode
+ "Minor mode for hiding the cursor."
+ :lighter nil
+ (if ffs--no-cursor-minor-mode
+ (progn
+ (unless ffs--old-cursor-type
+ (setq-local ffs--old-cursor-type cursor-type))
+ (setq-local cursor-type nil))
+ (setq-local cursor-type ffs--old-cursor-type)
+ (when ffs--old-cursor-type
+ ffs--old-cursor-type nil)))
+
+(defun ffs--toggle-dark-mode ()
+ "Swap the frame background and foreground colours."
+ (interactive)
+ (let ((bg (frame-parameter nil 'background-color))
+ (fg (frame-parameter nil 'foreground-color)))
+ (set-background-color fg)
+ (set-foreground-color bg)))
+
+(defun ffs--goto-previous (buffer)
+ "Go to the previous slide in the given BUFFER."
+ (interactive)
+ (with-current-buffer buffer
+ (let ((n (buffer-narrowed-p)))
+ (when n
+ (goto-char (point-min))
+ (widen)
+ (backward-page))
+ (backward-page)
+ (when n (narrow-to-page)))))
+
+(defun ffs-goto-previous ()
+ "Go to the previous slide in the main ffs presentation and the
+speaker notes buffer (if any)."
+ (interactive)
+ (ffs--goto-previous ffs--slides-buffer)
+ (when ffs--notes-buffer
+ (ffs--goto-previous ffs--notes-buffer)
+ (redraw-display)))
+
+(defun ffs--goto-next (buffer)
+ "Go to the next slide in the given BUFFER."
+ (interactive)
+ (with-current-buffer buffer
+ (let ((n (buffer-narrowed-p))
+ (e (= (- (point-max) (point-min)) 0)))
+ (when n
+ (goto-char (point-min))
+ (widen))
+ (unless e (forward-page))
+ (when n (narrow-to-page)))))
+
+(defun ffs-goto-next ()
+ "Go to the next slide in the main ffs presentation and the
+speaker notes buffer (if any)."
+ (interactive)
+ (ffs--goto-next ffs--slides-buffer)
+ (when ffs--notes-buffer
+ (ffs--goto-next ffs--notes-buffer)
+ (redraw-display)))
+
+(defun ffs--goto-first (buffer)
+ "Go to the first slide in the given BUFFER."
+ (interactive)
+ (with-current-buffer buffer
+ (let ((n (buffer-narrowed-p)))
+ (when n (widen))
+ (goto-char (point-min))
+ (when n (narrow-to-page)))))
+
+(defun ffs-goto-first ()
+ "Go to the first slide in the main ffs presentation and the
+speaker notes buffer (if any)."
+ (interactive)
+ (ffs--goto-first ffs--slides-buffer)
+ (when ffs--notes-buffer
+ (ffs--goto-first ffs--notes-buffer)
+ (redraw-display)))
+
+(defun ffs--goto-last (buffer)
+ "Go to the last slide in the given BUFFER."
+ (interactive)
+ (let ((n (buffer-narrowed-p)))
+ (when n (widen))
+ (goto-char (point-max))
+ (when n (narrow-to-page))))
+
+(defun ffs-goto-last ()
+ "Go to the last slide in the main ffs presentation and the
+speaker notes buffer (if any)."
+ (interactive)
+ (ffs--goto-last ffs--slides-buffer)
+ (when ffs--notes-buffer
+ (ffs--goto-last ffs--notes-buffer)
+ (redraw-display)))
+
+(defun ffs-start ()
+ "Start the presentation."
+ (interactive)
+ (ffs-minor-mode 1)
+ (ffs--no-mode-line-minor-mode 1)
+ (ffs--no-cursor-minor-mode 1)
+ (when (integerp ffs-default-face-height)
+ (setq-local
+ ffs--old-default-face-height
+ (face-attribute 'default :height))
+ (face-remap-add-relative
+ 'default :height ffs-default-face-height))
+ (show-paren-local-mode -1)
+ (display-battery-mode -1)
+ (flyspell-mode -1)
+ (narrow-to-page))
+
+(defun ffs-quit ()
+ "Quit the presentation."
+ (interactive)
+ (let ((n (buffer-narrowed-p))
+ (e (= (- (point-max) (point-min)) 0)))
+ (when (integerp ffs-default-face-height)
+ (face-remap-add-relative
+ 'default :height ffs--old-default-face-height))
+ (show-paren-local-mode 1)
+ (display-battery-mode 1)
+ (flyspell-mode 1)
+ (ffs--no-mode-line-minor-mode -1)
+ (ffs--no-cursor-minor-mode -1)
+ (if n
+ (progn
+ (goto-char (point-min))
+ (widen))
+ (ffs-minor-mode -1))
+ (when e (forward-char -1))))
+
+(defun ffs-edit (&optional add-above-or-below)
+ "Pop to a new buffer to edit a slide.
+If ADD-ABOVE-OR-BELOW is nil or not given, we are editing an
+existing slide. Otherwise, if it is `add-above' then the new
+slide will be added above/before the current slide, and if it is
+`add-below' then the new slide will be added below/after the
+current slide. The logic is implemented in `ffs-edit-done'."
+ (interactive)
+ (let* ((b (current-buffer))
+ (m major-mode)
+ (n (buffer-narrowed-p))
+ (s (if add-above-or-below ; if we are adding a new slide
+ "\n" ; start with just a newline
+ (unless n (narrow-to-page))
+ (prog1 (buffer-string)
+ (unless n (widen))))))
+ (pop-to-buffer-same-window
+ (get-buffer-create ffs-edit-buffer-name))
+ (funcall m)
+ (ffs-edit-minor-mode 1)
+ (insert s)
+ (goto-char (point-min))
+ (set-buffer-modified-p nil)
+ (setq-local
+ ffs--edit-source-buffer b
+ ffs--new-location add-above-or-below)
+ (message
+ (substitute-command-keys "Edit, then use `\\[ffs-edit-done]' \
+to apply your changes or `\\[ffs-edit-discard]' to discard them."))))
+
+(defun ffs-new-above ()
+ "Add a new slide above/before the current slide."
+ (interactive)
+ (ffs-edit 'add-above))
+
+(defun ffs-new-below ()
+ "Add a new slide below/after the current slide."
+ (interactive)
+ (ffs-edit 'add-below))
+
+(defun ffs-edit-discard ()
+ "Discard current ffs-edit buffer and return to the presentation."
+ (interactive)
+ (let ((b (current-buffer)))
+ (quit-windows-on b)
+ (kill-buffer b)))
+
+(defun ffs-edit-done ()
+ "Apply the ffs-edit changes and return to the presentation."
+ (interactive)
+ (let* (f
+ (str (buffer-string))
+ (s (if (string-suffix-p "\n" str)
+ str
+ (concat str "\n")))
+ (l ffs--new-location))
+ (with-current-buffer ffs--edit-source-buffer
+ (let ((inhibit-read-only t))
+ (save-excursion
+ (cond
+ ((eq l 'add-above)
+ (backward-page)
+ (insert (format "\n%s\f" s))
+ (setq f #'ffs-previous-slide))
+ ((eq l 'add-below)
+ (forward-page)
+ (insert (format "\n%s\f" s))
+ (setq f #'ffs-next-slide))
+ ((null l)
+ (narrow-to-page)
+ (delete-region (point-min) (point-max))
+ (insert s)
+ (widen))))))
+ (ffs-edit-discard)
+ (when (functionp f)
+ (funcall f))))
+
+(defun ffs--undo (&optional arg)
+ "Like `undo', but it works even when the buffer is read-only."
+ (interactive "P")
+ (let ((inhibit-read-only t))
+ (undo arg)))
+
+(defun ffs-find-speaker-notes-file (file)
+ "Prompt user for a speaker notes file, open it in a new frame."
+ (interactive "Fspeakers notes buffer: ")
+ (let ((b (current-buffer)))
+ (save-excursion
+ (find-file-other-frame file)
+ (ffs-minor-mode 1)
+ (setq-local
+ ffs--slides-buffer b
+ ffs--notes-buffer (current-buffer)))
+ (setq-local ffs--notes-buffer (get-file-buffer file))))
+
+(defun ffs-export-slides-to-pdf ()
+ (interactive)
+ (with-current-buffer ffs--slides-buffer
+ (ffs-goto-first)
+ (let ((c 1)
+ (fringe fringe-mode))
+ (fringe-mode 0)
+ (while (not (eobp))
+ (let ((fn (format "%s-%03d.pdf"
+ (file-name-sans-extension (buffer-name))
+ c))
+ (data (x-export-frames nil 'pdf)))
+ (with-temp-file fn
+ (insert data)))
+ (setq c (+ c 1))
+ (ffs-goto-next))
+ (fringe-mode fringe))))
+
+(defvar ffs-edit-minor-mode-map
+ (let ((map (make-sparse-keymap)))
+ (define-key map (kbd "C-c C-k") #'ffs-edit-discard)
+ (define-key map (kbd "C-c C-c") #'ffs-edit-done)
+ map)
+ "Keymap for `ffs-edit-minor-mode'.")
+
+(define-minor-mode ffs-edit-minor-mode
+ "Minor mode for editing a single ffs slide.
+When done editing the slide, run \\[ffs-edit-done] to apply your
+changes, or \\[ffs-edit-discard] to discard them."
+ :group 'ffs
+ :lighter " ffs-edit"
+ :keymap ffs-edit-minor-mode-map
+ (defvar-local ffs--edit-source-buffer nil
+ "The ffs presentation buffer of the slide being edited.")
+ (defvar-local ffs--new-location nil
+ "The location where the new slide should be inserted.
+See the docstring for `ffs-edit' for more details."))
+
+(defvar ffs-minor-mode-map
+ (let ((map (make-sparse-keymap)))
+ (define-key map (kbd "p") #'ffs-goto-previous)
+ (define-key map (kbd "n") #'ffs-goto-next)
+ (define-key map (kbd "DEL") #'ffs-goto-previous)
+ (define-key map (kbd "SPC") #'ffs-goto-next)
+ (define-key map (kbd "[") #'ffs-goto-previous)
+ (define-key map (kbd "]") #'ffs-goto-next)
+ (define-key map (kbd "<") #'ffs-goto-first)
+ (define-key map (kbd ">") #'ffs-goto-last)
+ (define-key map (kbd "s") #'ffs-start)
+ (define-key map (kbd "q") #'ffs-quit)
+ (define-key map (kbd "e") #'ffs-edit)
+ (define-key map (kbd "O") #'ffs-new-above)
+ (define-key map (kbd "o") #'ffs-new-below)
+ (define-key map (kbd "m") #'ffs--no-mode-line-minor-mode)
+ (define-key map (kbd "c") #'ffs--no-cursor-minor-mode)
+ (define-key map (kbd "d") #'ffs--toggle-dark-mode)
+ (define-key map (kbd "N") #'narrow-to-page)
+ (define-key map (kbd "W") #'widen)
+ (define-key map [remap undo] #'ffs--undo)
+ (define-key map (kbd "C-c n") #'ffs-find-speaker-notes-file)
+ map)
+ "Keymap for `ffs-minor-mode'.")
+
+(define-minor-mode ffs-minor-mode
+ "Minor mode for form feed-separated plain text presentations."
+ :group 'ffs
+ :lighter " ffs"
+ :keymap ffs-minor-mode-map
+ (setq-local
+ ffs--old-mode-line-format mode-line-format
+ ffs--old-cursor-type cursor-type
+ ffs--old-default-face-height
+ (face-attribute 'default :height))
+ (setq buffer-read-only ffs-minor-mode))
+
+(defun ffs ()
+ "Enable `ffs-minor-mode' for presenting the current buffer."
+ (interactive)
+ (ffs-minor-mode 1)
+ (setq-local ffs--slides-buffer (current-buffer)))
+
+(provide 'ffs)
+;;; ffs.el ends here
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