Add bookmark support0.17

Fixes #203

2 files changed, 34 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf35f3c..54815a6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,8 @@ String values are now shown as literals by default.
 Fixed an issue with modes that override after-change-major-mode-hook,
 such as `global-hi-lock-mode`.
 
+Added bookmark support.
+
 # v0.16
 
 Improved wording when looking at aliases.
diff --git a/helpful.el b/helpful.el
index 9dfd4be..49ad48d 100644
--- a/helpful.el
+++ b/helpful.el
@@ -2482,6 +2482,25 @@ or :foo."
   (or (fboundp symbol)
       (helpful--variable-p symbol)))
 
+(defun helpful--bookmark-jump (bookmark)
+  "Create and switch to helpful bookmark BOOKMARK."
+  (let ((callable-p (bookmark-prop-get bookmark 'callable-p))
+        (sym (bookmark-prop-get bookmark 'sym))
+        (position (bookmark-prop-get bookmark 'position)))
+    (if callable-p
+        (helpful-callable sym)
+      (helpful-variable sym))
+    (goto-char position)))
+
+(defun helpful--bookmark-make-record ()
+  "Create a bookmark record for helpful buffers.
+
+See docs of `bookmark-make-record-function'."
+  `((sym . ,helpful--sym)
+    (callable-p . ,helpful--callable-p)
+    (position    . ,(point))
+    (handler     . helpful--bookmark-jump)))
+
 (defun helpful--convert-c-name (symbol var)
   "Convert SYMBOL from a C name to an Elisp name.
 E.g. convert `Fmake_string' to `make-string' or
@@ -2620,13 +2639,25 @@ See also `helpful-max-buffers'."
     map)
   "Keymap for `helpful-mode'.")
 
+(declare-function bookmark-prop-get "bookmark" (bookmark prop))
+(declare-function bookmark-make-record-default "bookmark"
+                  (&optional no-file no-context posn))
+;; Ensure this variable is defined even if bookmark.el isn't loaded
+;; yet. This follows the pattern in help-mode.el.gz.
+;; TODO: find a cleaner solution.
+(defvar bookmark-make-record-function)
+
 (define-derived-mode helpful-mode special-mode "Helpful"
   "Major mode for *Helpful* buffers."
   (add-hook 'xref-backend-functions #'elisp--xref-backend nil t)
 
   (setq imenu-create-index-function #'helpful--imenu-index)
   ;; Prevent imenu converting "Source Code" to "Source.Code".
-  (setq-local imenu-space-replacement " "))
+  (setq-local imenu-space-replacement " ")
+
+  ;; Enable users to bookmark helpful buffers.
+  (set (make-local-variable 'bookmark-make-record-function)
+       #'helpful--bookmark-make-record))
 
 (provide 'helpful)
 ;;; helpful.el ends here