Add alt text to documentation

[isabela-pf]

References

No issues solely address missing alt text in documentation, but #9399 mentions in in "Issue Area 6" as does its break out issue #9682. This PR does not fix either of those issues in their entirety.

Code changes

Changes in this PR

1. Add an alt attribute to select images (..alt.. for .rst and the space in ![] for .md)
2. Provide a description of the image in that attribute
3. In cases where alt text is intentionally left blank, add a comment

No other changes to the documentation are being made. It's worth noting this is does not cover all the images in JupyterLab's documentation.

User-facing changes

There are no visual changes in this PR. Alt text is not visible unless a link is broken or otherwise fails to load. For users of assistive tech like screen readers, their experience should now have the image described to them instead of reading the image file name as before.

Backwards-incompatible changes

As far as I know, nothing about this is backwards incompatible.

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Thanks in advance for the review! If you have any questions about reviewing alt text, let me know and I'd be happy to tell you what I prioritize.

This alt text was contributed by wonderful volunteers at the SciPy 2022 sprints! They teamed up to make progress on so many images. I am just the messenger.

If you are curious how this was done, feel free to check out our working PR.

[jupyterlab-probot]

Thanks for making a pull request to jupyterlab!
To try out this branch on binder, follow this link:

[isabela-pf]

I turn away from this PR for a week and come back with two people to thank! I so appreciate all the help with this.

@fcollonval many thanks for cleaning up the PR! @krassowski thank you for your thorough review and testing out the comments!

I think I caught everything, but do let me know if there's more to fix.

[krassowski]

Thank you!

Edit: the test failure is relevant:

/home/runner/work/jupyterlab/jupyterlab/docs/source/index.rst:20: WARNING: exception while evaluating only directive expression: chunk after expression
/home/runner/work/jupyterlab/jupyterlab/docs/source/user/running.rst:18: WARNING: exception while evaluating only directive expression: chunk after expression

[krassowski]

New line is needed between .. only:: comment directive and the block.

[krassowski]

@meeseeksdev please backport to 3.4.x

[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 3.4.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 31b7832e1de55475da3e5fd7931e9156e8e75103

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

git commit -am 'Backport PR #12879: Add alt text to documentation'

4. Push to a named branch:

git push YOURFORK 3.4.x:auto-backport-of-pr-12879-on-3.4.x

5. Create a PR against branch 3.4.x, I would have named this PR:

"Backport PR #12879 on branch 3.4.x (Add alt text to documentation)"

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.

[krassowski]

Thanks @isabela-pf!