Re-add support for pdf-tools, now via generics

* doc-view-follow-pdf-tools.el: New file providing support for
'doc-view-follow-mode' when using pdf-tools.
(doc-view-follow-supported-p, doc-view-follow-setup)
(doc-view-follow-teardown, doc-view-follow-set-page)
(doc-view-follow-get-page): New generic function implementations.

1 files changed, 57 insertions, 0 deletions

diff --git a/doc-view-follow-pdf-tools.el b/doc-view-follow-pdf-tools.el
new file mode 100644
index 0000000..d4c4092
--- /dev/null
+++ b/doc-view-follow-pdf-tools.el
@@ -0,0 +1,57 @@
+;;; doc-view-follow-pdf-tools.el --- Support for doc-view-follow-mode with pdf-tools  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025  Free Software Foundation, Inc.
+
+;; Author: Paul D. Nelson <ultrono@gmail.com>
+;; Keywords: convenience
+
+;; 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:
+
+;; Support for `doc-view-follow-mode' with `pdf-tools'.
+
+;;; Code:
+
+(require 'doc-view-follow)
+(require 'pdf-view)
+
+(declare-function doc-view-follow-sync-pages "doc-view-follow")
+
+(cl-defmethod doc-view-follow-supported-p (&context (major-mode pdf-view-mode))
+  "When MAJOR-MODE is `pdf-view-mode', return t."
+  t)
+
+(cl-defmethod doc-view-follow-setup (&context (major-mode pdf-view-mode))
+  "When MAJOR-MODE is `pdf-view-mode', setup `doc-view-follow-mode'."
+  (add-hook 'pdf-view-after-change-page-hook
+            #'doc-view-follow-sync-pages nil 'local))
+
+(cl-defmethod doc-view-follow-teardown (&context (major-mode pdf-view-mode))
+  "When MAJOR-MODE is `pdf-view-mode', teardown `doc-view-follow-mode'."
+  (remove-hook 'pdf-view-after-change-page-hook
+               #'doc-view-follow-sync-pages 'local))
+
+(cl-defmethod doc-view-follow-set-page (page &context (major-mode pdf-view-mode))
+  "When MAJOR-MODE is `pdf-view-mode', go to PAGE in the document buffer."
+  (let ((pdf-view-inhibit-redisplay nil)
+        (page (max 1 (min page (pdf-cache-number-of-pages)))))
+    (pdf-view-goto-page page)))
+
+(cl-defmethod doc-view-follow-get-page (&context (major-mode pdf-view-mode))
+  "When MAJOR-MODE is `pdf-view-mode', return the current page number."
+  (pdf-view-current-page))
+
+(provide 'doc-view-follow-pdf-tools)
+;;; doc-view-follow-pdf-tools.el ends here