(Fmarkers_in): New function (bug#81153)

* src/marker.c (Fmarkers_in): New function.
(syms_of_marker): Defsubr it.
* doc/lispref/text.texi (Replacing): Add markers-in.
* test/src/marker-tests.el (marker-markers-in): New test.

doc/lispref/text.texi

@@ -4871,6 +4871,24 @@ Therefore, all else being equal, it is preferable to pass a buffer than
 a string as @var{source} argument.
 @end defun
 
+Sometimes @code{replace-region-contents} is unable to understand the
+nature of the change in which case information such as overlays and
+markers will not be preserved as well as we would like.  If this is
+important and you have enough knowledge about the change, you can
+preserve this information manually.  For example, when sorting the lines
+of a region, you can start by collecting all the overlays and markers in
+the affected region using @code{overlays-in} and @code{markers-in} as
+well as recording a description of the line on which they were found.
+After inserting the sorted lines, you can then move the objects back to
+their rightful position.
+
+@defun markers-in &optional beg end
+Return a list of all the markers found between @var{beg} and @var{end}
+in the current buffer.  @var{beg} defaults the @code{point-min} and
+@var{end} defaults to @code{point-max}.  Do not rely on the order of the
+markers in the list, because it is unspecified.
+@end defun
+
 @node Decompression
 @section Dealing With Compressed Data
 

etc/NEWS

@@ -90,6 +90,9 @@ To install the grammars, use 'M-x markdown-ts-mode-install-parsers'.
 
 * Lisp Changes in Emacs 32.1
 
++++
+** The new function 'markers-in' returns the set of markers in a region.
+
 ---
 ** New variable 'completion-frontend-properties'.
 This variable generalizes the 'completion-lazy-hilit' variable added in

src/marker.c

@@ -794,6 +794,36 @@ If TYPE is nil, it means the marker stays behind when you insert text at it.  */
   return type;
 }
 
+DEFUN ("markers-in", Fmarkers_in, Smarkers_in, 0, 2, 0,
+       doc: /* Return the list of markers in region BEG..END.
+The list includes markers at BEG and at END.  */)
+  (Lisp_Object beg, Lisp_Object end)
+{
+  Lisp_Object res = Qnil;
+  struct Lisp_Marker *tail;
+  ptrdiff_t ibeg, iend;
+  if (NILP (beg))
+    ibeg = BEGV;
+  else
+    {
+      CHECK_FIXNUM_COERCE_MARKER (beg);
+      ibeg = clip_to_bounds (BEGV, XFIXNUM (beg), ZV);
+    }
+  if (NILP (end))
+    iend = ZV;
+  else
+    {
+      CHECK_FIXNUM_COERCE_MARKER (end);
+      iend = clip_to_bounds (BEGV, XFIXNUM (end), ZV);
+    }
+
+  for (tail = BUF_MARKERS (current_buffer); tail; tail = tail->next)
+    if (ibeg <= tail->charpos && tail->charpos <= iend)
+      res = Fcons (make_lisp_ptr (tail, Lisp_Vectorlike), res);
+
+  return res;
+}
+
 #ifdef MARKER_DEBUG
 
 /* For debugging -- count the markers in buffer BUF.  */
@@ -840,4 +870,5 @@ syms_of_marker (void)
   defsubr (&Scopy_marker);
   defsubr (&Smarker_insertion_type);
   defsubr (&Sset_marker_insertion_type);
+  defsubr (&Smarkers_in);
 }

test/src/marker-tests.el

@@ -57,4 +57,17 @@
     (set-marker marker-2 marker-1)
     (should (goto-char marker-2))))
 
+(ert-deftest marker-markers-in ()
+  (with-temp-buffer
+    (insert "hello ")
+    (let ((m2 (point-marker)))
+      (insert "world")
+      (let ((m1 (point-min-marker))
+            (m3 (point-max-marker))
+            (ms (markers-in (1+ (point-min)) (1- (point-max)))))
+        (should (memq m2 ms))
+        (should-not (memq m1 ms))
+        (should-not (memq m3 ms))
+        (should (all (lambda (m) (eq (marker-buffer m) (current-buffer))) ms))))))
+
 ;;; marker-tests.el ends here