Add macro for walking buffer content (for example to search)

editor/editor.lisp

@@ -498,6 +498,29 @@ Additionally ensures correct line numbers on the way, as a bonus."
                                           (cursor-line (cursor buffer)))))
     (move-cursor line-number (cursor-column (cursor buffer)))))
 
+(defmacro do-buffer ((line column character &key start-line (start-column 0)
+                                              (direction :forward))
+                     buffer &body body)
+  (declare (type (member :forward :backward) direction))
+  `(loop :with ,line := ,(or start-line (if (eql direction :forward)
+                                            `(first-line ,buffer)
+                                            `(last-line ,buffer)))
+         :with ,column := ,start-column
+         :for ,character := (ignore-errors
+                             (char (line-content ,line) ,column))
+         :unless (null ,character)
+           :do (progn ,@body)
+         :do (incf ,column ,(if (eql direction :forward) 1 -1))
+         :when ,(if (eql direction :forward)
+                    `(>= ,column (line-length ,line))
+                    `(< ,column 0))
+           :do ,(if (eql direction :forward)
+                    `(setf ,line (next-line ,line)
+                           ,column 0)
+                    `(setf ,line (prev-line ,line)
+                           ,column (ignore-errors (line-length ,line))))
+         :until (null ,line)))
+
 
 
 (defun status-line-string ()