Add variant for erc-match invisibility spec

* lisp/erc/erc-match.el (erc-match-mode, erc-match-enable,
erc-match-disable): Arrange for possibly adding or removing
`erc-match' from `buffer-invisibility-spec'.
(erc-match--hide-fools-offset-bounds): Add new variable to serve as
switch for activating invisibility on a modified interval that's
offset toward `point-min' by one character.
(erc-hide-fools): Optionally offset start and end of invisible region
by minus one.
(erc-match--modify-invisibility-spec): New housekeeping function to
set up and tear down offset spec.  (Bug#60936.)

1 files changed, 23 insertions, 4 deletions

diff --git a/lisp/erc/erc-match.el b/lisp/erc/erc-match.el
index 7ec9078d493..82b821503a8 100644
--- a/lisp/erc/erc-match.el
+++ b/lisp/erc/erc-match.el
@@ -53,8 +53,11 @@ they are hidden or highlighted.  This is controlled via the variables
 you can decide whether the entire message or only the sending nick is
 highlighted."
   ((add-hook 'erc-insert-modify-hook #'erc-match-message 'append)
+   (add-hook 'erc-mode-hook #'erc-match--modify-invisibility-spec)
    (erc--modify-local-map t "C-c C-k" #'erc-go-to-log-matches-buffer))
   ((remove-hook 'erc-insert-modify-hook #'erc-match-message)
+   (remove-hook 'erc-mode-hook #'erc-match--modify-invisibility-spec)
+   (erc-match--modify-invisibility-spec)
    (erc--modify-local-map nil "C-c C-k" #'erc-go-to-log-matches-buffer)))
 
 ;; Remaining customizations
@@ -649,13 +652,22 @@ See `erc-log-match-format'."
                                         (get-buffer (car buffer-cons))))))
     (switch-to-buffer buffer-name)))
 
+(defvar-local erc-match--hide-fools-offset-bounds nil)
+
 (defun erc-hide-fools (match-type _nickuserhost _message)
  "Hide foolish comments.
 This function should be called from `erc-text-matched-hook'."
- (when (eq match-type 'fool)
-   (erc-put-text-properties (point-min) (point-max)
-                            '(invisible intangible)
-                            (current-buffer))))
+  (when (eq match-type 'fool)
+    (if erc-match--hide-fools-offset-bounds
+        (let ((beg (point-min))
+              (end (point-max)))
+          (save-restriction
+            (widen)
+            (put-text-property (1- beg) (1- end) 'invisible 'erc-match)))
+      ;; The docs say `intangible' is deprecated, but this has been
+      ;; like this for ages.  Should verify unneeded and remove if so.
+      (erc-put-text-properties (point-min) (point-max)
+                               '(invisible intangible)))))
 
 (defun erc-beep-on-match (match-type _nickuserhost _message)
   "Beep when text matches.
@@ -663,6 +675,13 @@ This function is meant to be called from `erc-text-matched-hook'."
   (when (member match-type erc-beep-match-types)
     (beep)))
 
+(defun erc-match--modify-invisibility-spec ()
+  "Add an ellipsis property to the local spec."
+  (if erc-match-mode
+      (add-to-invisibility-spec 'erc-match)
+    (erc-with-all-buffers-of-server nil nil
+      (remove-from-invisibility-spec 'erc-match))))
+
 (provide 'erc-match)
 
 ;;; erc-match.el ends here