(feat): add org-roam-buffer-preview-function (#1388)

Instead of storing preview content in the database, now provide a
function to fetch these on the fly. This paves the way for future
improvements (e.g. showing more lines)

org-roam-buffer.el

@@ -36,6 +36,8 @@
 (require 's)
 (require 'f)
 (require 'ol)
+(require 'org-element)
+(require 'org-roam-macs)
 
 (defvar org-roam-directory)
 (defvar org-link-frame-setup)
@@ -98,6 +100,13 @@ Has an effect if and only if `org-roam-buffer-position' is `top' or `bottom'."
   :type 'hook
   :group 'org-roam)
 
+(defcustom org-roam-buffer-preview-function #'org-roam-buffer--preview
+  "Function to obtain preview contents for a given link.
+The function takes in two arguments, the FILE containing the
+link, and the POINT of the link."
+  :type 'function
+  :group 'org-roam)
+
 (defcustom org-roam-buffer-window-parameters nil
   "Additional window parameters for the `org-roam-buffer' side window.
 For example: (setq org-roam-buffer-window-parameters '((no-other-window . t)))"
@@ -124,6 +133,16 @@ For example: (setq org-roam-buffer-window-parameters '((no-other-window . t)))"
                       'font-lock-face
                       'org-document-title)))
 
+(defun org-roam-buffer--preview (file point)
+  "Get preview content for FILE at POINT."
+  (org-roam--with-temp-buffer file
+    (goto-char point)
+    (let ((elem (org-element-at-point)))
+      (or (org-element-property :raw-value elem)
+          (when-let ((begin (org-element-property :begin elem))
+                     (end (org-element-property :end elem)))
+            (string-trim (buffer-substring-no-properties begin end)))))))
+
 (defun org-roam-buffer--pluralize (string number)
   "Conditionally pluralize STRING if NUMBER is above 1."
   (let ((l (pcase number
@@ -171,7 +190,7 @@ ORIG-PATH is the path where the CONTENT originated."
                                                     "file")))
               (dolist (backlink bls)
                 (pcase-let ((`(,file-from _ ,props) backlink))
-                  (insert (if-let ((content (plist-get props :content)))
+                  (insert (if-let ((content (funcall org-roam-buffer-preview-function file-from (plist-get props :point))))
                               (propertize (org-roam-buffer-expand-links content file-from)
                                           'help-echo "mouse-1: visit backlinked note"
                                           'file-from file-from
@@ -208,7 +227,7 @@ ORIG-PATH is the path where the CONTENT originated."
                               (org-roam-buffer-expand-links file-from))
                         "Top")
                       "\n"
-                      (if-let ((content (plist-get prop :content)))
+                      (if-let ((content (funcall org-roam-buffer-preview-function file-from (plist-get prop :point))))
                           (propertize
                            (s-trim (s-replace "\n" " " (org-roam-buffer-expand-links content file-from)))
                            'help-echo "mouse-1: visit backlinked note"

org-roam.el

@@ -602,17 +602,8 @@ it as FILE-PATH."
           (goto-char (org-element-property :begin link))
           (let* ((type (org-roam--collate-types (org-element-property :type link)))
                  (path (org-element-property :path link))
-                 (element (org-element-at-point))
-                 (begin (or (org-element-property :contents-begin element)
-                            (org-element-property :begin element)))
-                 (end (or (org-element-property :contents-end element)
-                          (org-element-property :end element)))
-                 (content (or (org-element-property :raw-value element)
-                              (when (and begin end)
-                                (string-trim (buffer-substring-no-properties begin end)))))
                  (properties (list :outline (org-roam--get-outline-path)
-                                   :content content
+                                   :point (point)))
-                                   :point begin))
                  (names (pcase type
                           ("id"
                            (when-let ((file-path (org-roam-id-get-file path)))