I looked all over for how to set the default plot to file path and had not much success until I stumbled across this post:
http://forums.autodesk.com/t5/Visual-LISP-AutoLISP-and-General/vla-get-defaultplottofilepath/m-p/215...
With this information I was able to set the default plot to file path in the options dialog using only VLisp.
(VLA-PUT-DEFAULTPLOTOTFILEPATH o_prefs <new path>) o_prefs is defined in code below.
I'm still crawling along in my uncderstanding of the object model and how to get at it. Everything seems very difficult because I have no good reference of the available functions and how to use them. I know many of you will see what I am so excited to have discovered as elementary, and I know it is, but that's where I am and I suspect there must be others like me, so, for them, here it is:
I discovered something regarding the options dialog that I thought might help others as well. It sure will help me. (the following code is from the above linked original post, I've added some notes):
;;make sure vl- functions work
(VL-LOAD-COM)
;;get the acad application
(SETQ acad (VLAX-GET-ACAD-OBJECT))
;;get the application preferences,
(SETQ prefs (VLA-GET-PREFERENCES acad))
;;
;;HERE IS WHAT I THOUGHT MIGHT HELP SOMEBODY
;;
;;prefs object has the following properties which provide
;;access to the tabs in the Options Dialog:
; Application (RO) = #<VLA-OBJECT ...>
; Display (RO) = #<VLA-OBJECT ...>
; Drafting (RO) = #<VLA-OBJECT ...>
; Files (RO) = #<VLA-OBJECT ...>
; OpenSave (RO) = #<VLA-OBJECT ...>
; Output (RO) = #<VLA-OBJECT ...>
; Profiles (RO) = #<VLA-OBJECT ...>
; Selection (RO) = #<VLA-OBJECT ...>
; System (RO) = #<VLA-OBJECT ...>
; User (RO) = #<VLA-OBJECT ...>
;;get at the preferences on any of the tabs using
;;(VLA-GET-<name> <object>)
;;for example:
(SETQ o_prefs (VLA-GET-OUTPUT prefs))
;;HTH someone
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