support exporting a plot from an unopened/inactive plugin

[kecnry]

Description

This pull request fixes the case of exporting the stretch histogram from the export plugin before the plot options plugin has ever been opened. It does so by implementing an optional callback on the Plot object itself to call a plugin method to update itself, which will be called if the "parent" plugin is not considered active. In cases where no widget exists because the parent plugin has never been opened, it also renders the widget offscreen in the export plugin.

I'm not really sure the best way to test this since the previous behavior didn't result in errors, just a blank image - but open to any suggestions!

Change log entry

• Is a change log needed? If yes, is it added to CHANGES.rst? If you want to avoid merge conflicts,
  list the proposed change log here for review and add to CHANGES.rst before merge. If no, maintainer
  should add a no-changelog-entry-needed label.

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a milestone set? Set this to bugfix milestone if this is a bug fix and needs to be released ASAP; otherwise, set this to the next major release milestone. Bugfix milestone also needs an accompanying backport label.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Attention: Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.79%. Comparing base (0d7684a) to head (b89689a).
Report is 158 commits behind head on main.

Files with missing lines	Patch %	Lines
jdaviz/core/template_mixin.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2934   +/-   ##
=======================================
  Coverage   88.79%   88.79%           
=======================================
  Files         111      111           
  Lines       17236    17245    +9     
=======================================
+ Hits        15305    15313    +8     
- Misses       1931     1932    +1     

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[gibsongreen]

Great work, everything looks good to me and this is working really well!

[rosteen]

Hmm, it looks like this saved something for the histogram, but I don't think the saved plot is correct. It saved out this image:

[Deleted the images]

Edit: Actually, I tried again and it worked the second time - maybe I hadn't restarted the kernel properly after checking out this branch. Now the only surprise to me is that it didn't give me an Overwrite warning the second time I ran it 🤔

[rosteen]

This improves the current behavior, so I'm approving. I did notice that the plot as rendered by this PR doesn't have the line indicating the stretch scaling, but I don't know how big a deal that is - we may want to address it later, but if you want to address it now I can re-review.

[kecnry]

Now the only surprise to me is that it didn't give me an Overwrite warning the second time I ran it

This is a separate ticket 🐱

I did notice that the plot as rendered by this PR doesn't have the line indicating the stretch scaling

Is it possible that they're just outside the default x-limits?

[kecnry]

It also seems that sometimes on first attempt, this is still failing and clearing the selection - I'm looking into seeing if that is an easy fix now

[kecnry]

I'm going to go ahead and merge this as-is since it fixes the reported bug and should get in. If we keep running into the "selection clearing" bug (which definitely happens less with this PR than without it), that can be investigated and fixed as a follow-up.

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout v3.10.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 18bb83ea78efff030e77f58bb99d5beba7f400ce

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #2934: support exporting a plot from an unopened/inactive plugin'

4. Push to a named branch:

git push YOURFORK v3.10.x:auto-backport-of-pr-2934-on-v3.10.x

5. Create a PR against branch v3.10.x, I would have named this PR:

"Backport PR #2934 on branch v3.10.x (support exporting a plot from an unopened/inactive plugin)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.