Pinned Tabs Cause Unexpected Shifting in Vertical Tabs

[jonathansampson]

Description

The scrollable region of the vertical tab view shifts unexpectedly when collapsing after the mouse has left the region.

As shown in the video below (the scroll view has a green border), when the last tab is in view, and the mouse exits the collapsing tab strip, the last tab is shifted out of view.

Recording.2025-01-14.062758.mp4

Steps to reproduce

The scrollable region of the vertical tab view shifts unexpectedly when a few things are true:

1. There are too many tabs to display within the window (i.e., the tab strip is scrollable)
2. The vertical tab strip is configured to collapse when the mouse exits the region
3. Two or more tabs are pinned to the top of the tab strip

In this scenario, when there is more than 1 tab pinned, the scrollable tab list will shift itself to hide the last n tabs, where n is the total number of pinned tabs - 1. As such, if 2 tabs are pinned, the final tab in the list will be shifted out of view. If 3 tabs are pinned, the final 2 tabs will be shifted out of view.

Actual result

The vertical tabs' scroll offset adjusts itself when the mouse exits the region, and doesn't appear to fully consider the number of pinned tabs that are fixed above the region.

Expected result

The vertical tabs' scroll offset should remain unchanged as the mouse exits the view.

Reproduces how often

Easily reproduced

Brave version (brave://version info)

1.73.105 Chromium: 131.0.6778.265 (Official Build) (64-bit)

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

Originally reported via https://x.com/keepawake2/status/1878450173942149630, but further details were fleshed out in private DMs.