@pagarcia wrote:
Hello,
I need help to handle a custom CRhinoUndoEventHandler.
My plugin adds custom mesh objects into the document, each of them having an instance of custom ON_UserData attached. The commands receive some user interaction as input, update the user data and replace the object with an updated mesh.
From Dale's SampleCustomUndo I see that my
CRhinoUndoEventHandlershould have as member an instance of my data (which will store its "old" version before the user does Undo), and inside the virtualUndoI should code the way of doing Undo operation. Inside my plugin, I'd useAddCustomUndoEventwith the current data before running any command.However, I have three crucial questions:
1) When I write data, I don't know whether it's my ON_UserData or the linked CRhinoMeshObject that "lives" in the document, or both.
2) For me, my custom user data and the mesh object are the same: when an instance of user data is updated, its corresponding mesh is updated and replaces the old one. In the undo event handler, where do I perform the operation of replacing the last mesh with the old one?
In the header I read "Never change any setting in the Rhino document or application", which leads me to confusion (whether the operation of replacing a mesh is a change of settings, etc).
3) In Dale's sample I see that the operations coded in
Undomodify an instance of data (adoublevalue) that is a private member ofCRhinoUtilityPlugIn. Why is this necessary? I assume that it is for easy tracking of the data to be "undone", but what's the way to do it with multiple objects that are in the document?For example, I have a command that takes as input 2 custom meshes A and B and as output gives two new meshes C and D, being C the updated version of A and D the updated version of B. If the user does Undo and I want to recover A/B from C/D, I don't know how to track them properly from the members in the undo handler and the document.
Any idea or hint will be very appreciated!
Pablo
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