introduce defer-setup customize optionexternals/indent-bars

2 files changed, 20 insertions, 1 deletions

diff --git a/NEWS.org b/NEWS.org
index fa1c69d..1b1f0ef 100644
--- a/NEWS.org
+++ b/NEWS.org
@@ -2,6 +2,10 @@
 #+author: J.D. Smith
 #+language: en
 
+* DEVELOPMENT
+
+- Add custom option ~indent-bars-defer-setup~ to help with late setup of indentation parameters, including file/dir-local and other helper modes like ~dtrt-indent~.
+
 * v1.0 (2025-01-19)
 
 - Implement /bar-skipping/ in multiply-nested list contexts (with ~indent-bars-no-descend-lists~ set to ~skip~).
diff --git a/indent-bars.el b/indent-bars.el
index 571e3e5..29f4a97 100644
--- a/indent-bars.el
+++ b/indent-bars.el
@@ -533,6 +533,19 @@ buffer-local automatically."
   :initialize #'custom-initialize-default
   :group 'indent-bars)
 
+(defcustom indent-bars-defer-setup nil
+  "Whether to defer indent-bars setup to `after-change-major-mode-hook'.
+Setting up `indent-bars' correctly in a buffer requires correct
+information about the indentation spacing and tabs vs. spaces.  If these
+are set after `indent-bars' is initialized, via another minor mode, or
+in file or directory-local variables, this can lead to incorrect
+behavior.  In these cases, it can be useful to defer `indent-bars' setup
+to the `after-change-major-mode-hook'.  Enable this only if you only
+experience problems, and enable `indent-bars' via major mode
+hooks (e.g. `python-base-mode')."
+  :type 'boolean
+  :group 'indent-bars)
+
 ;;;;; Color Utilities
 (defun indent-bars--background (&optional no-remap)
   "Return the background color.
@@ -1910,7 +1923,9 @@ Adapted from `highlight-indentation-mode'."
       (if (and (daemonp) (not (frame-parameter nil 'client)))
 	  (add-hook 'after-make-frame-functions #'indent-bars-setup-and-remove
 		    nil t)
-	(indent-bars-setup))
+	(if indent-bars-defer-setup
+	    (add-hook 'after-change-major-mode-hook #'indent-bars-setup nil t)
+	  (indent-bars-setup)))
     (indent-bars-teardown)))
 
 ;; Theme support