=== Problem to solve
Scrolling down on a long timeline ([[https://tools.wmflabs.org/interaction-timeline/?wiki=testwiki&user=Test-apples&user=Test-bananas|example]]) loses of the context of which user is represented in which column. (Is apples the left column or right column?)
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===Acceptance criteria
* If the user is scrolling below the username bar an overlay should appear at the top of the page, displaying the usernames above the Timeline columns
* Should play well with the diff overlay
* There should be a nice and simple hide/show animation for the overlay.
* Include a link to '↑ Top' in the far right side of the overlay. On click, it should scroll the user to the top of the page.
* The usernames should be linked to their userpage on the selected wiki, and open in a new tab when clicked.
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===Mockup
{F12945602}