From 8c9c47f6e3f94d263a5f5e88e28ed583179f2770 Mon Sep 17 00:00:00 2001
From: Daniel Borchmann <daniel@algebra20.de>
Date: Sat, 29 Apr 2023 17:25:36 +0200
Subject: [PATCH] Prominently display of active filters in agenda view

Displaying the current filters in the mode line alone often goes unnoticed for
me, so I need a more direct display.  Let's add it to the first structural
header.
---
 init.el             | 20 ++++++++++++++------
 site-lisp/db-org.el | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/init.el b/init.el
index 4d9af23..6ed5303 100644
--- a/init.el
+++ b/init.el
@@ -742,6 +742,7 @@
              endless/org-ispell
              db/org-agenda-list-deadlines
              db/org-agenda-skip-tag
+             db/org-agenda-insert-active-filters
              hydra-org-agenda-view/body
              db/org-agenda-insert-efforts
              db/org-eval-subtree-no-confirm
@@ -1134,9 +1135,6 @@
               org-agenda-search-headline-for-time nil
               org-agenda-search-view-always-boolean t
 
-              ;; Show daily efforts directly in the agenda
-              org-agenda-finalize-hook '(db/org-agenda-insert-efforts)
-
               org-agenda-clock-consistency-checks
               '(:max-duration 9999999
                 :min-duration 0
@@ -1257,15 +1255,25 @@
                                (org-agenda-skip-deadline-prewarning-if-scheduled t)))))))
 
   :config (progn
-            ;; avoid important buffers to end up in `org-agenda-new-buffers’ by
+            ;; Avoid important buffers to end up in `org-agenda-new-buffers’ by
             ;; opening them manually
             (mapc #'find-file-noselect org-agenda-files)
 
-            (add-hook 'org-agenda-mode-hook #'hl-line-mode 'append)
-
+            ;; Check that all expected agenda files are being displayed.
             (advice-add 'org-agenda
                         :before #'db/check-special-org-files-in-agenda)
 
+            (add-hook 'org-agenda-mode-hook #'hl-line-mode 'append)
+
+            ;; Show daily efforts directly in the agenda
+            (add-hook 'org-agenda-finalize-hook #'db/org-agenda-insert-efforts)
+
+            ;; Prominently display active filters on top of agenda view; also
+            ;; update current agenda view when updating filters to make sure our
+            ;; display is always correct.
+            (add-hook 'org-agenda-finalize-hook #'db/org-agenda-insert-active-filters)
+            (add-hook 'org-agenda-filter-hook #'org-agenda-redo-all)
+
             (define-advice org-agenda-redo-all (:around (old-func &rest r) goto-top-and-execute)
               "Avoid recentering the Org agenda buffer after redo by moving
 point to the beginning of buffer first."
diff --git a/site-lisp/db-org.el b/site-lisp/db-org.el
index a72cec8..8eaaa70 100644
--- a/site-lisp/db-org.el
+++ b/site-lisp/db-org.el
@@ -112,6 +112,40 @@ deadlines."
       (setq buffer-read-only t)
       (message ""))))
 
+(defun db/org-agenda-insert-active-filters (&optional match)
+  "Insert string showing the current agenda filters.
+
+The filter display is added after the structural header.
+
+If no agenda filters are active, nothing will be inserted.
+
+Add this function to `org-agenda-finalize-hook' to enable this."
+  ;; First delete any present active filter display, as it might be obsolete.
+  (save-excursion
+    (when-let ((pos (text-property-any
+                     (point) (point-max) 'db/active-filter-display t)))
+      (goto-char pos)
+      (kill-line)))
+
+  ;; Insert current active filters if there are any.
+  (when (org-agenda-filter-any)
+    (save-excursion
+      (when-let ((pos (text-property-any
+                       (point) (point-max) 'org-agenda-structural-header t)))
+        (goto-char pos)
+        (end-of-line)
+
+        ;; Current filter display shamelessly stolen from `org-agenda-filter'.
+        ;; Is there a function to do this?
+        (let* ((cf (mapconcat #'identity org-agenda-category-filter ""))
+	       (tf (mapconcat #'identity org-agenda-tag-filter ""))
+	       (ef (replace-regexp-in-string "^\\+" "" (or (car org-agenda-effort-filter) "")))
+	       (rf (replace-regexp-in-string "^\\+" "" (or (car org-agenda-regexp-filter) "")))
+	       (ff (concat cf tf ef (when (not (equal rf "")) (concat "/" rf "/")))))
+          (insert-and-inherit
+           (propertize (format " [%s]" ff)
+                       'db/active-filter-display t)))))))
+
 (defun db/org-agenda-skip-tag (tag &optional others)
   ;; https://stackoverflow.com/questions/10074016/org-mode-filter-on-tag-in-agenda-view
   "Skip all entries that correspond to TAG.