ansi-color-apply-on-region.diff

--- a.el	2022-04-26 01:58:00.191401081 +0200
+++ b.el	2022-04-26 01:58:00.191401081 +0200
@@ -42,10 +42,18 @@
                      ;; Store new start position.
                      (set-marker start-marker (point)))
                    (match-beginning 0) (ansi-color--find-face codes))
-          ;; If this is a color sequence,
-          (when (eq (aref esc-seq (1- (length esc-seq))) ?m)
-            ;; update the list of ansi codes.
-            (setq codes (ansi-color-apply-sequence esc-seq codes)))))
+          (let ((last-char (aref esc-seq (1- (length esc-seq)))))
+            (pcase last-char
+              ;; A color sequence
+              (`?m
+               ;; update the list of ansi codes.
+               (setq codes (ansi-color-apply-sequence esc-seq codes)))
+              ;; A cursor back (CUB) sequence
+              (`?D
+               (let ((n (string-to-number (substring esc-seq 2 -1)))
+                     (line-start (let ((inhibit-field-text-motion t))
+                                   (line-beginning-position))))
+                 (delete-region (max line-start (- (point) n)) (point))))))))
       ;; search for the possible start of a new escape sequence
       (if (re-search-forward "\033" end-marker t)
 	  (progn