MultiDim unexpectedly inserts entries into ChangeHistory

Workflow to reproduce the problem:

1. Start MultiDim local plugin.
2. Start ChangeHistory global plugin.
3. Load a data cube.
4. With ChangeHistory (“History” tab) in view, click on “next slice” (double-arrow) button on MultiDim and watch a new entry magically appears on ChangeHistory for that image.
5. Click on “next slice” again or “prev slice” to see another such entry.

Example screenshot:

I suspect this is caused by either block_callback('modified') or unblock_callback('modified') in MultiDim.py. I just never caught this before until now because I rarely start up ChangeHistory with data cubes, but I think this has been happening for a while.

This bug is harmless but confusing, in the sense that it does not actually change the input data cube, but merely reported that it has done so.

[ejeschke]

Ok, after looking at the particular combination of tests, I think your modification will work. I’ll merge it and submit as a PR.

[ejeschke]

I think it may be slightly difficult, due to the fact that the modified callback is in only some cases tied to changes that should be recorded in ChangeHistory and then only because the user set some particular metadata in the channel info for an image, prior to the change.

One thing we might do is to detect that the plugin is trying to set the reason_modified attribute in the channel info for an image, and throw up an error message then. We’d probably want to check very specifically for this attribute name, since there should be no real reason to disallow the plugin from otherwise adding arbitrary data to the info, as other plugins (e.g. Thumbs, etc) already do.