在 Lisp 退出时执行代码

Question

我写了一个 lisp，它涉及设置一个变量，然后在循环内选择点。一旦我决定完成点的选择，我希望能够在按下退出键时将该变量恢复到原来的状态。例如。

(defun c:df ()
(setq oom (getvar "osmode")) ;store current state


(setq type(getint "\nEnter Type: 1 For Horizontal, 2 For Vertical : "))

(setq startpt (getpoint "\nChoose Start Point : ")) 
(setq ptx (+ (nth 0 startpt)10))
(setq pty (+ (nth 1 startpt)10))

(setvar "osmode" 2); change state state

(while 

     (setq nextpt (getpoint "'Pick Mid: ")) ;make selection



     (if (null nextpt) ((princ "\nNull Value Error.") return))

     (if (= type 1) (command "dimlinear" startpt nextpt "H" (list 0 pty) )) 
     (if (= type 2) (command "dimlinear" startpt nextpt "V" ptx ))

     (setq ptx (+ 5 ptx))   
     (setq pty (+ 5 pty))
)

;do after escape key is pressed.

(setvar "osmode" oom) ;revert state back to original.
)

我发现可能与“用户输入错误”有关的线索，但无法真正发挥作用。据我所知，当按下转义时，lisp 只是退出并且没有完成执行。

提前致谢。

Answer 1

AutoLISP 将取消视为错误。因此，您可以通过错误处理来管理取消。AutoLISP 提供了*error*可以在本地重新定义的函数。

此外，我想提出几点建议：

• 不要将type符号用于变量，它是内置 AutoLISP 函数的名称

• 在本地声明变量（必须是*error*函数）

• 使用getkword和initget让用户选择一个选项。

  (defun c:df (/ *error* oom option startpt ptx pty nextpt) ; local variables
  
    ;; *error* local redefinition
    (defun *error* (msg)
      (if (/= msg "Function cancelled")
        (princ (strcat "\nError: " msg))
      )
      (if oom
        (setvar "osmode" oom)
      )
      (princ)
    )
  
    (setq oom (getvar "osmode"))          ;store current state
  
    (initget 1 "Horizontal Vertical")
    (setq option (getkword "\nChoose an option [Horizontal/Vertical]: "))
  
    (if (setq startpt (getpoint "\nChoose Start Point : "))
      (progn
        (setq ptx (+ (car startpt) 10))
        (setq pty (+ (cadr startpt) 10))
  
        (setvar "osmode" 2)               ; change state state
  
        (while (setq nextpt (getpoint "'Pick Mid: ")) ;make selection
           (if (= option "Horizontal")
             (command "_dimlinear" startpt nextpt "H" (list 0 pty))
             (command "_dimlinear" startpt nextpt "V" (list ptx 0))
           )
  
           (setq ptx (+ 5 ptx))
           (setq pty (+ 5 pty))
        )
  
        (setvar "osmode" oom)             ;revert state back to original.
      )
    )
    (princ)
  )