[BUG] `add_markers` on a viewer clears the markers in the other viewers

[eteq]

Jdaviz component

Imviz

Description

I have a workflow where I create multiple viewers to look at subsets of my data. I want to put a different set of markers on each of the viewers. It's already in an astropy table so I can just imviz.viewrers[viewer-name].add_markers(...). But to my surprise, doing this in one viewer clears the markers in the previous viewer!

This is very counter-intuitive and breaks several use cases so I'm assuming it's a bug. But if it's intended behavior, this can be viewed as a request to change the behavior 😉

How to Reproduce

1. Install jdaviz from coda-forge
2. Add at least one new viewer view imviz.create_image_viewer
3. Do viewer.add_markers(...) sequentially on the first and then second viewer.

Expected behavior

I should see two separate set of markers on each viewer

[pllim]

Did you try using different marker names?

If you have existing markers under the same marker name, the old ones get replaced, not appended. Ginga implementation is the same here:

https://github.com/astropy/astrowidgets/blob/be9dc866b1546458f92c566b63c03beb651c56a8/astrowidgets/ginga.py#L765

Here is Jdaviz implementation:

jdaviz/jdaviz/core/astrowidgets_api.py

Line 510 in ac021d7

jglue.data_collection[marker_name] = t_glue

In Jdaviz though, the markers are added as Data, which is app-level, not viewer level.

To make things even more confusing, the Markers plugin (that does not use Astrowidgets), I think, is at viewer level but only defined in bqplot figure level and not available via glue. Can Astrowidgets implementation go this route? Sure. But that might complicate get_markers (which I don't think we have finalized yet).