Avoid whitespace-mode breaking standard-display-unicode-special-glyphs

* lisp/whitespace.el (whitespace-display-char-on): Copy from
'standard-display-table' if 'buffer-display-table' is nil.  This
avoids overwriting display-table customizations by features that
modify 'standard-display-table' for global effects.  (Bug#78522)

(cherry picked from commit fc96cc1feb488dfeffd760d63872515f04033894)

diff --git a/lisp/whitespace.el b/lisp/whitespace.el
index 1042575956289437e1406e57e7c8f985d80b2d3e..58ba0db8c9083620e986198f8ceed54813c98e7a 100644 (file)
--- a/lisp/whitespace.el
+++ b/lisp/whitespace.el
@@ -2480,7 +2480,8 @@ purposes)."
        ;; Assure `buffer-display-table' is unique
        ;; when two or more windows are visible.
        (setq buffer-display-table
-             (copy-sequence buffer-display-table)))
+             (copy-sequence (or buffer-display-table
+                                 standard-display-table))))
       (unless buffer-display-table
        (setq buffer-display-table (make-display-table)))
       (dolist (entry whitespace-display-mappings)