Moderator Tools/Content moderation on mobile web/Diff

Diffs are a fundamental component of navigation and content moderation on Wikimedia projects. The diff page in mobile web is missing core links and actions expected of this page, and we do not believe it helps newer editors understand how Wikimedia projects work.

This work is also responding to numerous community requests to add an Undo button to mobile diffs. In the mobile web interface, editors cannot - by default - easily access mechanisms for undoing edits. With Advanced Mobile Contributions (AMC) turned on, editors can access an Undo button on page histories only, which opens the desktop undo interface. Editors should be able to undo edits from a diff.

The Moderator Tools team would like to improve the design of the mobile diff page and enable undoing edits from diffs in mobile web in the process.

'''We have some open questions about how to approach this work. Please share your thoughts on the talk page.'''

Diff
Diffs on mobile web are generated by Special:MobileDiff, a custom mobile-only view which is substantially different from the desktop diff. Differences include using in-line diffs instead of a two-column view, not including links to a page's edit history or to a user's contributions, and the lack of undo, change visibility, and other moderation actions. The only direct action a user can initiate on mobile web is to thank the user.

In-line diffs
In-line diffs show the difference between two revisions by displaying added and removed text within the same blocks of text. This saves vertical space compared to a two-column view, as content isn't repeated, but can lead to confusing diffs, especially in the case of edits which make a variety of updates to a paragraph, as opposed to adding or removing entire paragraphs of text.

Screen sizes have, on average, increased since the decision was made to use in-line diffs, and other tools (such as SWViewer, make good use of two-column diffs at mobile screen widths. We would like to explore options for providing editors with both diff styles on mobile web, or those who prefer the two-column view. While this would be a per-editor preference, we also need to decide which to display to newer editors by default.

Questions: What do you like or dislike about in-line and two-column diff views? Do you just want to use one of these, or should users be able to toggle between them?

Links
We believe that page histories, user contributions, and diffs should all link directly to each other, to enable easy navigation between revisions on Wikimedia projects. Currently, mobile diff does not include any direct links to page history or user contributions.

Questions: What other pages do you think should be linked from diffs?

Undo
Mobile editors who do not have Advanced Mobile Contributions (AMC) turned on cannot access buttons for undoing edits from page histories or diffs. Enabling AMC adds Undo and Rollback buttons to page histories, along with revision deletion functionality, but does not add these to diffs. We think it's clear that the diff page should have an undo button.

When using Undo from mobile web, the desktop edit view is shown, enabling a partial revert, where edits are made to the page while the edit is undone. This interface is clearly not designed for mobile screen widths and results in users needing to scroll far down the page to confirm undoing the edit. When we carried out data analysis, we found that just 3% of undo actions are partial reverts, with the rest being full reverts. Given this, we might imagine building a way to fully undo an edit without needing to open the page editor.

Questions: What do you think of enabling editors to fully undo an edit more quickly, without needing to use the editor?

Wireframes
We have been exploring some very early design prototypes for what an updated diff page could look like, and we'd love to hear your feedback on what you think of them.

Wireframes will be added soon.

Open questions

 * What do we need to know about diffs and undoing edits which isn't captured above?
 * Do you use any gadgets or user scripts which extend the functionality of the diff page or the process of undoing edits (on desktop or mobile)?

Related links

 * T191706 - It's not possible to undo/rollback edits from diff on Mobile
 * Community Wishlist Survey 2019/Mobile and apps/Add an undo/revert button to diff view
 * Community Wishlist Survey 2021/Mobile and apps/Undo on mobile
 * User:FR30799386/undo