Is there a way to call your own undo and or redo method when your operator is being 'undone'? I already used this bpy built-in method:
bl_info = {'UNDO'}
but this didn't do the full undo.
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2 Answers
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Blender's undo system works by saving the blend file to memory, and loading it to perform the undo. If your operator doesn't fully undo, you're probably calling other operators from within its code. That's usually a bad idea; modify object properties and call functions instead.
There are no undo/redo functions that you can override.
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$\begingroup$ So there is no real workaround if you call a 'add modifier' operator from within your own operator to undo this action? $\endgroup$Bert VdB– Bert VdB2017-12-03 11:30:08 +00:00Commented Dec 3, 2017 at 11:30
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2$\begingroup$ Look at the source code of the operator. If it calls into a Python function to do the real work, you can just call that function instead of the operator itself. $\endgroup$dr. Sybren– dr. Sybren2017-12-03 23:37:17 +00:00Commented Dec 3, 2017 at 23:37
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There is a way.
- Register a
BoolPropertyto the scene, here we call itchecker. - In your operator, access
checkerviacontextand runchecker = not checker. - Define two global bool property:
checker_cacheandskip_checker_update. - In the update function of
checker, ifskip_checker_updateisFalse, sync thecheckerand thechecker_cache. - Define your own post undo function
my_undo_post(scene, _)and a pre undo functionmy_undo_pre(_, _). - In your pre undo/redo function, set
skip_checker_updateas True so the blender's undo/redo logic will change back thecheckerbecause it is registed, but thechecker_cachewill keep unchanged. - In your post undo/redo function, check if the
checkernot equalschecker_cache, if is, sync them and run your undo logic. Then turnskip_checker_updateback toFalse - Append your own pre/post undo/redo functions to blender's. E.g. run
bpy.app.handlers.undo_post.append(my_undo_post).
It's a little complex but basically works.
