From 22758e8c9214f2086fe0c0a424c993f0a52a5780 Mon Sep 17 00:00:00 2001
From: Amin Bandali <bandali@kelar.org>
Date: Thu, 19 May 2022 21:57:45 -0400
Subject: Add ffs (form feed slides) mode for GNU Emacs

This is what I used for preparing and  presenting my LibrePlanet 2022
talk, 'The Net beyond the web' back in March. :)
---
 .emacs.d/lisp/ffs/ffs.el | 419 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 419 insertions(+)
 create mode 100644 .emacs.d/lisp/ffs/ffs.el

(limited to '.emacs.d/lisp/ffs/ffs.el')

diff --git a/.emacs.d/lisp/ffs/ffs.el b/.emacs.d/lisp/ffs/ffs.el
new file mode 100644
index 0000000..99f2097
--- /dev/null
+++ b/.emacs.d/lisp/ffs/ffs.el
@@ -0,0 +1,419 @@
+;;; 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 ().
+
+;; 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" s))
+            (setq f #'ffs-previous-slide))
+           ((eq l 'add-below)
+            (forward-page)
+            (insert (format "\n%s" 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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