AutoCAD Visual LISP Technical Newsletter - November 1999

XDSoft

AutoCAD Visual LISP Technical Newsletter - November 1999  
This document is part of    Visual Lisp Newsletter Archive     



  
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Dear Visual LISP developer,
  

Table of Contents
=================
(1) R14->R2000 LDATA ACCESSIBILITY
(2) Reactors in Visual LISP
(3) Debugging Visual LISP code
(4) New or updated solutions
  

(1) R14->R2000 LDATA ACCESSIBILITY
==================================

Into AutoCAD 2000, you may try loading an R14 drawing with ldata. But
unfortunately you'll be denied to access to R14's ldata while using
vlax-ldata-*** functions. This is due to a version incompatibility.
The workaround is provided at the following solution URL which contains
an attachment.

/cgi-bin/solution.pl?SID=45315

After you have downloaded the attachment and extracted it's files, move
the files ldataproxy.dll and ldata.arx into the same directory of your
machine's AutoCAD 2000 executable. You will see in the demonstrative
LISP file, checkforldata.lsp, the lines:

(if (null ldata-activate) (arxload "ldata.arx") )
(ldata-activate "EN81LIFTA")

The ldata.arx implements an external lisp function: ldata-activate. This
function takes as an argument the base filename (without extension) of the
compiled R14 Visual LISP ARX application. This will recover the proxy
information and allow the vlax-ldata-*** functions to work as expected.

While in R2000, if you run the function (chkforLdata) on the R14 drawing
included, you will observe a dump of the R14-generated ldata information.

Note: The R14 ldata will not withstand a round-trip of saves. If you save
the drawing in A2000 format, next time you open the dwg, you don't need to
execute the procedure. If you save the DWG back to R14 format, though, you
won't be able to access the LDATA info anymore in R14.
  
  

(2) Reactors in Visual LISP
===========================

Visual LISP not only makes program development easier and faster, it also
provides new functionality to AutoLISP applications. For example, you can
attach reactors to entities in the AutoCAD drawing window, allowing your
application to respond to user actions on these entities.

A reactor is an object you attach to AutoCAD drawing objects in order to have
AutoCAD notify your application when events you are interested in occur. For
example, if a user moves an entity that your application has attached a
reactor to, your application will receive notification that the entity has
moved. If you design it to do so, your application can react to this
notification with appropriate actions, such as moving other entities
associated with the one moved, or perhaps updating a text tag that records
revision information on the altered drawing feature.

A reactor communicates with your application by calling a function you have
associated with the reactor. Such a function is referred to as a callback
function. There isn't anything particularly unusual about reactor callback
functions, they are like other functions you write with Visual LISP. They
become callback functions when you attach them to reactor events.

There are many types of AutoCAD reactors. Each reactor type responds to one
or more AutoCAD events. The different types of reactors are grouped into
the following categories:

+ Database Reactors
  -----------------
  Database reactors notify your application when specific events occur to
  the drawing database, such as when an object has been added to the
  database.

+ Document Reactors
  -----------------
  Document reactors notify your application of a change to the current
  drawing document, such as opening a new drawing document, activating a
  different document window, and changing a document's lock status.

+ Editor Reactors
  ---------------
  Editor reactors notify you each time an AutoCAD command is invoked;
  a drawing opens, closes, or is saved;
  a DXF file is imported or exported;
  or a system variable changes value.

+ Linker Reactors
  ---------------
  Linker reactors notify your application every time an ARX application is
  loaded or unloaded.

+ Object Reactors
  ---------------
  Object reactors notify you each time a specific object is changed, copied,
  or deleted.

With the exception of Editor reactors, there is one type of reactor for each
reactor category.

Reactors may be transient or persistent. Transient reactors are lost when a
drawing closes; this is the default reactor mode. Persistent reactors are
saved with the drawing and exist when the drawing is next opened.
Use the vlr-pers function to make a reactor persistent. To remove persistence
from a reactor and make it transient, use vlr-pers-release. Each function
takes a Reactor object as its only argument.

HOW TO MONITOR AERIAL VIEW USAGE WITH VISUAL LISP
/cgi-bin/solution.pl?SID=7578

MAKING REACTORS PERSISTENT IN A DRAWING
/cgi-bin/solution.pl?SID=10858
  

(3) Debugging Visual LISP code
==============================

In AutoCAD 2000 functions are no longer lists. You will need to use the
Visual LISP IDE to locate the point of failure in your code. While it may
require some work learning about these IDE debug features, you'll find that
it's a much better environment to debug lisp code than that old command line
dump.

What you need to do to enable this facility (since the default is as you know
otherwise), will be to open the Visual LISP IDE at the beginning of your
AutoCAD session (type VLIDE at the command line), and go to the Debug Pulldown
menu in the IDE, and Select the 'Break On Error'. Then load your lisp code and
run it. When an error in your code occurs, you'll be put back into the Visual
LISP IDE, all you'll need to do to see which line caused the error is to
select the 'Last Break' option on the Debug Toolbar, or the
'Last Break Source' on the Debug pulldown.

There's many more powerful tools available to debug your lisp code using the
Visual LISP IDE, please refer to the Visual LISP Developer's Guide
See Chapter 3 -- Debugging Programs
for more information on using the IDE and it's debug features.
  

(4) New or updated solutions
============================

CREATING AND MANIPULATING XRECORDS USING AUTOLISP
/cgi-bin/solution.pl?SID=16132

(COMMAND) FUNCTION DOES NOT WORK WITH NEW AND OPEN
/cgi-bin/solution.pl?SID=29417

HOW TO IDENTIFY UNREFERENCED LAYERS IN LISP?
/cgi-bin/solution.pl?SID=30528

CREATION & MANIPULATION OF GROUPS USING AUTOLISP IN R14
/cgi-bin/solution.pl?SID=44942

USING THE SELECTION SET SELECT METHOD IN VISUAL LISP
/cgi-bin/solution.pl?SID=12298

USING A VB ACTIVEX DLL FROM VISUAL LISP OR VB(A)
/cgi-bin/solution.pl?SID=15992

CONSTUCTING Visual LISP LWPOLYLINE VIA ACTIVEX
/cgi-bin/solution.pl?SID=16152

EXTENSION DICTIONARY TO ASSOCIATE OBJECTS
/cgi-bin/solution.pl?SID=21716

HOW TO OPEN A NEW DRAWING IN VISUAL LISP
/cgi-bin/solution.pl?SID=30445

ATTRIBUTE DIALOG IS NOT DISPLAYING WHEN ATTDIA=1
/cgi-bin/solution.pl?SID=32444

HOW DO I REPLACE THE PLOTTER AND PLOTID SYSTEM VARIABLES
/cgi-bin/solution.pl?SID=41173

USING LISP TO FILTER SPECIFIC EXTENDED ENTITY DATA
/cgi-bin/solution.pl?SID=44434

WHAT IS THE OBJECT THAT VLAX-LDATA-XXX MANIPULATED?
/cgi-bin/solution.pl?SID=44984

USING LISP TO MODIFY THE ACAD SYSTEM VARIABLE
/cgi-bin/solution.pl?SID=45047

USING AN ARX ACTIVEX SERVER TO UPDATE THE BLOCK DESCRIPTION FROM LISP
/cgi-bin/solution.pl?SID=45070

ACAD.LSP & ACADDOC.LSP DO NOT LOAD IN DOCUMENT CREATED BY (COMMAND "NEW")
/cgi-bin/solution.pl?SID=45180

USING AN ARX ACTIVEX SERVER TO DETERMINE THE LOADED LISP FILES
/cgi-bin/solution.pl?SID=45186

WORKAROUND LOAD FAILURE ACAD.LSP/ACADDOC.LSP WHEN USING COMMAND NEW/OPEN
/cgi-bin/solution.pl?SID=45304
  

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