bug#66604: [PATCH] Gud LLDB completions

["Mattias Engdegård" <mattias.engdegard@gmail.com>]

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20 okt. 2023 kl. 19.28 skrev Gerd Möllmann <gerd.moellmann@gmail.com>:

> Look at these escape sequences that suddenly appear when attaching to a
> process! I don't even know what "<esc>[1G" and "<esc>[8G" do.

Fascinating! We should probably look into the source code producing it (libedit probably) but I wrote the attached monstrosity and it... seems to work. (Proof of concept only.)

It attempts to edit out the part of strings jumped over by CHA (CSI G), and it also edits out ED (CSI J) which is in this case just used to do exactly that immediately after CHA.


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diff --git a/lisp/progmodes/gud.el b/lisp/progmodes/gud.el
index 8518738d09e..245600a2f94 100644
--- a/lisp/progmodes/gud.el
+++ b/lisp/progmodes/gud.el
@@ -3871,6 +3871,42 @@ gud-lldb-stop
 
 (defun gud-lldb-marker-filter (string)
   "Deduce interesting stuff from process output STRING."
+  (let ((ofs 0))
+    (while (string-match (rx (* (not (in "\n\e")))
+                             (group "\e[")
+                             (? (group (+ digit)))
+                             (group (in "GJ")))
+                         string ofs)
+      (let ((bol (match-beginning 0))
+            (seq-start (match-beginning 1))
+            (arg (and (match-beginning 2)
+                      (string-to-number (match-string 2 string))))
+            (op-char (aref string (match-beginning 3)))
+            (seq-end (match-end 0)))
+        (cond ((eq op-char ?G)
+               ;; Move to absolute column. Argument is 1-based.
+               (let* ((goal-col (1- (or arg 1)))
+                      (current-col (current-column))
+                      (prefix-len (- seq-start bol))
+                      (eff-col (+ current-col prefix-len))
+                      (rel-move-left (- eff-col goal-col))
+                      (del-prefix (max 0 (min prefix-len rel-move-left)))
+                      (elide-start (- seq-start del-prefix))
+                      (elide-end seq-end)
+                      (del-chars (- rel-move-left del-prefix)))
+                 ;; FIXME: insert extra spaces if we move beyond eff-col
+                 (when (> del-chars 0)
+                   (delete-char (- del-chars)))
+                 (setq string
+                       (concat (substring string 0 elide-start)
+                               (substring string elide-end)))
+                 (setq ofs (+ bol (- prefix-len del-prefix)))))
+              ((eq op-char ?J)
+               ;; Erase in display
+               ;; FIXME
+               (setq string (concat (substring string 0 seq-start)
+                                    (substring string seq-end)))
+               (setq ofs seq-start))))))
   (cond
    ;; gud-info: (function-name args...)
    ((string-match (rx line-start (0+ blank) "gud-info:" (0+ blank)