#define private public - Expanding Drawlists (14 Nov 2017)

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---+++ [[DefinePrivatePublic20171114ExpandingDrawlists][Expanding drawlists]] (14 Nov 2017)

<summary>
Last week, someone <a href="https://ww3.cad.de/foren/ubb/Forum92/HTML/000883.shtml">posted a question to a customer forum</a> 
for <nop>CoCreate Modeling (aka PTC Creo Elements/Direct Modeling),
providing the perfect excuse for me to dabble with LISP again.
</summary>

The question centered on how to expand the results of the API call =sd-inq-vp-drawlist-objects= which returns a list of all 
currently visible objects.

<div style="float:right;">
    <img src="%ATTACHURLPATH%/drawlist.png" alt="drawlist.png"  width="200" height="234"  />
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In the example to the right, the following objects are checked, and are therefore visible:
   * Assembly "a1"
   * Part "cone" in assembly "a1"
   * Part "cube" in assembly "a1"
   * Part "backplate" in assembly "act_assy"
   * Part "housing" in assembly "act_assy"
   * Part "pistonhead" in assembly "act_assy/pst_subassy"
   * Part "shaft" in assembly "act_assy/pst_subassy"

To reduce the amount of data it has to return, =sd-inq-vp-drawlist-objects= "compresses" its result as follows:
   * If all objects below an assembly are checked (=visible), only the assembly is returned
   * In partially visible assemblies, visible objects are returned individually

So in our example, =sd-inq-vp-drawlist-objects= would return a list containing:
   * /a1
   * /act_assy/backplate
   * /act_assy/housing
   * /act_assy/pst_subassy

This representation is perfectly fine for many purposes, but in the specific circumstances of the forum post, the user 
needed a way to "uncompress" the result, and wasn't interested in the assemblies, only in parts. So in the given example,
the desired output would have been:

   * /a1/cone
   * /a1/cube
   * /act_assy/backplate
   * /act_assy/housing
   * /act_assy/pst_subassy/piston-head
   * /act_assy/pst_subassy/shaft

Assembly structures can be highly nested, of course, and so a recursive solution is needed.

My first solution revisited an approach I used in 
a [[http://www.clausbrod.de/cgi-bin/view.pl/Blog/DefinePrivatePublic20150404FlacheHierarchien][previous blog post]]
which discussed how to recurse over a hierarchy of objects and build a flat list from it.

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<pre id='vimCodeElement'>
<span class="Special">(</span><span class="Statement">in-package</span> :de.clausbrod.expanddrawlist<span class="Special">)</span>
<span class="Special">(</span><span class="Statement">use-package</span> :oli<span class="Special">)</span>

<span class="Special">(</span><span class="Statement">defun</span> flatten-assembly-mapcan<span class="Special">(</span>node<span class="Special">)</span>
  <span class="Special">(</span><span class="Statement">cons</span> node
   <span class="Special">(</span><span class="Statement">mapcan</span> <span class="Type">#'flatten-assembly-mapcan</span> <span class="Special">(</span>sd-inq-obj-children node<span class="Special">))))</span>

<span class="Special">(</span><span class="Statement">defun</span> expand-objects<span class="Special">(</span>objects<span class="Special">)</span>
  <span class="Special">(</span><span class="Statement">loop</span> for obj in objects
   <span class="Statement">nconc</span> <span class="Special">(</span><span class="Statement">remove-if-not</span> <span class="Type">#'sd-inq-part-p</span> <span class="Special">(</span>flatten-assembly-mapcan obj<span class="Special">))))</span>

<span class="Special">(</span><span class="Statement">defun</span> show-part<span class="Special">(</span>p<span class="Special">)</span>
  <span class="Special">(</span>display <span class="Special">(</span>sd-inq-obj-pathname p<span class="Special">)))</span>

<span class="Special">(</span><span class="Statement">let</span> <span class="Special">((</span>displayed-objects <span class="Special">(</span>sd-inq-vp-drawlist-objects <span class="Special">(</span>sd-inq-current-vp<span class="Special">))))</span>
  <span class="Special">(</span><span class="Statement">mapc</span> <span class="Type">#'show-part</span> <span class="Special">(</span>expand-objects displayed-objects<span class="Special">)))</span>
</div>

This worked and returns lists as described above. However, if you're actually not really interested in those intermediate lists, but instead simply
want to visit all visible parts in the assembly tree and execute some action for each of those parts, then the problem can be solved more succinctly:

<div>

<pre id='vimCodeElement'>
<span class="Special">(</span><span class="Statement">in-package</span> :de.clausbrod.expanddrawlist<span class="Special">)</span>
<span class="Special">(</span><span class="Statement">use-package</span> :oli<span class="Special">)</span>

<span class="Special">(</span><span class="Statement">defun</span> show-part<span class="Special">(</span>p<span class="Special">)</span>
  <span class="Special">(</span>display <span class="Special">(</span>sd-inq-obj-pathname p<span class="Special">)))</span>

<span class="Special">(</span><span class="Statement">defun</span> visit-parts<span class="Special">(</span>obj<span class="Special">)</span>
  <span class="Special">(</span><span class="Statement">if</span> <span class="Special">(</span>sd-inq-part-p obj<span class="Special">)</span>
      <span class="Special">(</span>show-part obj<span class="Special">)</span>
    <span class="Special">(</span><span class="Statement">mapc</span> <span class="Type">#'visit-parts</span> <span class="Special">(</span>sd-inq-obj-children obj<span class="Special">))))</span>

<span class="Special">(</span><span class="Statement">let</span> <span class="Special">((</span>displayed-objects <span class="Special">(</span>sd-inq-vp-drawlist-objects <span class="Special">(</span>sd-inq-current-vp<span class="Special">))))</span>
  <span class="Special">(</span><span class="Statement">mapc</span> <span class="Type">#'visit-parts</span> displayed-objects<span class="Special">)))</span>
</div>


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