GraphEditor : Data loss of "nodedef" associations for "nodegraphs" on save

[kwokcb]

Issue

If you load in a document where a nodegraph has a nodedef reference it is lost on save.
Basically it is no longer an implementation (functional) graph.

Steps

1. Load in: "resources\Materials\TestSuite\pbrlib\multioutput\multishaderoutput.mtlx
2. Write to disk.

Change

  <nodegraph name="NG_multi" nodedef="ND_multi">

becomes

  <nodegraph name="NG_multi" >

You will see validation errors in the console.

[minhpham1810]

Hi! I'm a student in the CodePath AI301 program, and I'd like to work on this issue.

I traced the likely cause to Graph::savePosition() in MaterialXGraphEditor/Graph.cpp, where the nodedef attribute is removed from every current UI element before the document is written. This also affects top-level NodeGraph elements, causing their functional nodedef association to be lost.

My plan is to preserve the attribute for mx::NodeGraph elements, use mx::InterfaceElement::NODE_DEF_ATTRIBUTE instead of the raw string, and add a regression test based on multishaderoutput.mtlx.

Would this approach be acceptable? If so, I’d be happy to open a PR.

[kwokcb]

Hi @minhpham1810 ,
Thanks for diagnosing.

It looks like savePosition() is used in a number of places which I think still may need this nodedef removal so
I think it may need to be conditionally performed. Maybe it only needs to be done on functional graphs from data libraries ?

@lfl-eholthouser pinging you for input on the required logic here. Thx.

---

I don't think it's possible to write an regression test currently:

• As a suggestion a -s/--save <document_name>.mtlx could be added as a command line option.
  ( similar to how there is a --captureFilename option but your just performing a document save vs render + image save.
• A load + save could be performed with a data integrity test on the saved file.