Steps to replicate the issue (include links if applicable):

• Setup MediaWiki-Docker
• Setup ProofreadPage per this guide
• Add $wgProofreadPageEnableEditInSequence = true; to your LocalSettings.php file (inside the mediawiki/ directory)
• Create this page Index:War and Peace.djvu (by saving the page)
• Navigate to Page:War and Peace.djvu/2 and click on Edit pages in sequence
• Click on the Preview button on the top banner.

What happens?:

• Only a part of the grey loading animation is visible

What should have happened instead?:

• The animation should take all of the left pane

Deliverables

To complete this task:

• Go through everything on the "How to become a MediaWiki hacker" page. https://www.mediawiki.org/wiki/How_to_become_a_MediaWiki_hacker
• Get the source code (linked from the extension's page on mediawiki.org) from Gerrit/Git: https://www.mediawiki.org/wiki/Download_from_Git
• Assign this task to yourself.
• Create a patch and reference this task in the commit message according to the guidelines mentioned here https://www.mediawiki.org/wiki/Gerrit/Commit_message_guidelines
• Verify the issue has been fixed by reproducing the change locally using the replication instructions.
• Upload the patch to Gerrit.

Notes

• The preview animation/code is being controlled by modules/page.editinsequence/PreviewWidget.js