Find and delete empty text

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;;; ============================================================================
;;; CXEMPTYTXT - Find and delete empty text
;;; Version 1.0.0
;;; CADXChange LISP tools - https://cadxchange.net/resources/lisp/cxemptytxt
;;; Tested in: AutoCAD (full version). Other programs that run AutoLISP may work but are not tested.
;;; Copyright (c) CADXChange. Free for personal and commercial use; do not resell or
;;; republish it as a collection. Terms: https://cadxchange.net/legal/lisp-terms
;;; ============================================================================

;; The TEXT and MTEXT objects in NAMES that show nothing (empty, only spaces, or only formatting codes).
;; With DEL true they are erased as well. Returns the entity names found.
(defun cx:emptytxt-run (names del / out mt)
  (foreach e names
    (setq mt (= (cx:dxf 0 (entget e)) "MTEXT"))
    (if (= (cx:trim (cx:text-plain (cx:text-get e) mt nil)) "")
      (setq out (cons e out))))
  (setq out (reverse out))
  (if del (foreach e out (entdel e)))
  out)

(defun c:CXEMPTYTXT ( / *error* cx:sv ss found)
  (setq *error* cx:err)
  (setq ss (ssget "X" (list '(0 . "TEXT,MTEXT") (cons 410 (getvar "CTAB")))))
  (if ss
    (progn
      (setq found (cx:emptytxt-run (cx:ss->list ss) nil))
      (cond
        ((null found) (princ "\nNo empty text found."))
        ((= (cx:ask-kw (strcat (itoa (length found)) " found. Action") "Delete Select" "Select") "Delete")
         (cx:start '(("CMDECHO" . 0)))
         (cx:emptytxt-run found T)
         (princ (strcat "\n" (itoa (length found)) " object(s) deleted."))
         (cx:end))
        (T
         (sssetfirst nil (cx:list->ss found))
         (princ (strcat "\n" (itoa (length found)) " object(s) selected."))))))
  (princ))


;;; ---- Shared helpers (used by the command above; identical in every CADXChange tool) ----

(defun cx:dxf (code ed)
  (cdr (assoc code ed)))

;; Remove spaces and tabs at both ends.
(defun cx:trim (s / a b)
  (setq a 1 b (strlen s))
  (while (and (<= a b) (member (substr s a 1) '(" " "\t"))) (setq a (1+ a)))
  (while (and (>= b a) (member (substr s b 1) '(" " "\t"))) (setq b (1- b)))
  (substr s a (max 0 (1+ (- b a)))))

;; Split a TEXT (MT = nil) or MTEXT (MT = T) string into ((T . "plain") (C . "format code") ...).
;; Codes are %%c-style symbols, and in MTEXT also \P, \f...; \H...; \S...; {, } and the like.
(defun cx:fmt-tokens (str mt / out plain i n c d j k)
  (setq out nil plain "" i 1 n (strlen str))
  (while (<= i n)
    (setq c (substr str i 1) k 0)
    (cond
      ((and (= c "%") (= (substr str (1+ i) 1) "%") (< (1+ i) n))
       (setq k (if (wcmatch (substr str (+ i 2) 1) "#") 5 3)))
      ((and mt (= c "\\"))
       (setq d (substr str (1+ i) 1))
       (cond
         ((= d "") (setq k 1))
         ((member d '("P" "X" "x" "L" "l" "O" "o" "K" "k" "~" "\\" "{" "}")) (setq k 2))
         ((member d '("U" "u")) (setq k 7))
         (T
          (setq j i)
          (while (and (<= j n) (/= (substr str j 1) ";")) (setq j (1+ j)))
          (setq k (if (<= j n) (1+ (- j i)) 2)))))
      ((and mt (or (= c "{") (= c "}"))) (setq k 1)))
    (if (> k 0)
      (progn
        (if (/= plain "") (setq out (cons (cons 'T plain) out) plain ""))
        (setq out (cons (cons 'C (substr str i k)) out) i (+ i k)))
      (setq plain (strcat plain c) i (1+ i))))
  (if (/= plain "") (setq out (cons (cons 'T plain) out)))
  (reverse out))

;; The visible text of a TEXT or MTEXT string. In MTEXT, \P becomes a line break (KEEPNL = T: the two characters \P are kept).
(defun cx:text-plain (str mt keepnl / out)
  (setq out "")
  (foreach tk (cx:fmt-tokens str mt)
    (cond
      ((= (car tk) 'T) (setq out (strcat out (cdr tk))))
      ((= (cdr tk) "\\P") (setq out (strcat out (if keepnl "\\P" "\n"))))
      ((= (cdr tk) "\\~") (setq out (strcat out " ")))
      ((member (cdr tk) '("\\\\" "\\{" "\\}")) (setq out (strcat out (substr (cdr tk) 2))))))
  out)

;; The text of a TEXT, ATTRIB, ATTDEF or MTEXT (MTEXT keeps its codes).
(defun cx:text-get (ename / ed s)
  (setq ed (entget ename))
  (if (= (cx:dxf 0 ed) "MTEXT")
    (progn
      (setq s "")
      (foreach p ed (if (= (car p) 3) (setq s (strcat s (cdr p)))))
      (strcat s (cx:dxf 1 ed)))
    (cx:dxf 1 ed)))

;; Close the undo step and put the system variables back.
(defun cx:end ()
  (foreach v cx:sv (setvar (car v) (cdr v)))
  (command "_.UNDO" "_End")
  (setq cx:sv nil)
  (princ))

;; Error handler: restores everything, stays quiet on Esc.
(defun cx:err (msg)
  (if (> (getvar "CMDACTIVE") 0) (command))
  (cx:end)
  (if (and msg (not (wcmatch (strcase msg) "*BREAK*,*CANCEL*,*EXIT*")))
    (princ (strcat "\nError: " msg)))
  (princ))

;; Selection set to a list of entity names.
(defun cx:ss->list (ss / i out)
  (setq i 0)
  (if ss
    (repeat (sslength ss)
      (setq out (cons (ssname ss i) out)
            i   (1+ i))))
  (reverse out))

;; Replace every OLD in STR by NEW (case sensitive).
(defun cx:replace (str old new / n out pos)
  (setq n (strlen old) out "" pos 1)
  (if (= n 0)
    str
    (progn
      (while (<= pos (1+ (- (strlen str) n)))
        (if (= (substr str pos n) old)
          (setq out (strcat out new) pos (+ pos n))
          (setq out (strcat out (substr str pos 1)) pos (1+ pos))))
      (strcat out (substr str pos)))))

;; Ask for one of the keywords in BITS ("Yes No"), default DEF; returns the keyword.
(defun cx:ask-kw (msg bits def / v)
  (initget 0 bits)
  (setq v (getkword (strcat "\n" msg " [" (cx:replace bits " " "/") "] <" def ">: ")))
  (if v v def))

;; Save the system variables in VARS ((name . value) ...), set them, and open one undo step.
;; The caller declares cx:sv as a local so the saved values live exactly as long as the command.
(defun cx:start (vars)
  (setq cx:sv (mapcar (function (lambda (v) (cons (car v) (getvar (car v))))) vars))
  (command "_.UNDO" "_Begin")
  (foreach v vars (setvar (car v) (cdr v)))
  (princ))

;; A selection set holding the entity names in LST.
(defun cx:list->ss (lst / ss)
  (setq ss (ssadd))
  (foreach e lst (ssadd e ss))
  ss)

(princ "\nCXEMPTYTXT loaded. Type CXEMPTYTXT to start.")
(princ)

More commands: Clean-up

• CXBYLAYERSet color, linetype and lineweight back to ByLayer
• CXZEROLENFind and delete zero-length lines and polylines
• CXFONTCHKList text styles whose font file is missing
• CXFONTSUBReplace one font file by another in all text styles
• CXPURGEPurge the drawing until nothing more goes
• CXDELTYPEDelete every object of the type you pick
• CXDIMRESETReset typed-over dimension text to the measured value
• CXDUPDELDelete exact duplicate objects
• CXOBJCOUNTCount the objects by type