MaterialsObserver and Undo

[mgraham]

I have followed the sample code, and created a MaterialsObserver, and it works well. I can react to materials changes as needed when they occur.

However, if the user chooses to Undo a material change, the only notification I am getting is onTransactionUndo.

Is there something else I need to add to my code so that I know it is a material that has changed during the Undo action? And equally important, which material has changed.

[DanRathbun]

There are open issues in the API tracker:

• Observers for Removed events - Should fire before removal · Issue #402 · SketchUp/api-issue-tracker (github.com)

• Tracking major events in the lifetime of a Sketchup session · Issue #682 · SketchUp/api-issue-tracker (github.com)

• Improve documentation for undo handling · Issue #627 · SketchUp/api-issue-tracker (github.com)

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Basically, the only workaround is for your extension to cache data and state at a higher level. Then in the observer callback check your extension’s list of materials for missing materials or changed properties.