Prerequisites
Vertical tabs ON, latest Nightly build.
STR

1. Set the pinned tabs area height to maximum on a fairly narrow sidebar width.
2. Resizing the sidebar up
3. Resizing the sidebar down.

Expected result
Since I have set max height for the pinned tabs are, we should remember the setting on resizing down. The height of the pinned tabs area should always be maximized for a given sidebar width, ensuring that all pins are visible at all times.

Actual result*
Upon resizing the sidebar down, the pinned tabs area height I set is not remembered. Instead the heigh of the pinned tabs corresponds to the number of rows of pinned tabs displayed at the maximum width of the sidebar I reached in step 2. For instance, if I made the sidebar wide enough to display all my pins in one row, my pinned tabs area in step 3 will be limited to one row.

Screen recording of the issue

We agreed to interpret pulling the splitter down to give the pinned tabs area max height as a reset of the pref with the user-set height. When it is done, we will go back to auto-adjusting the height of the pinned tabs area based on the contents (number of pinned tabs).

Also noting that we should not be overriding the custom user-preferred height when we are adjusting the height to prevent a gap/space between pinned and unpinned tabs.

please assign (outreachy may 26 applicant)

Hi, Kelly. care to add a label for outreachy :)

Here is a revision like you asked, https://phabricator.services.mozilla.com/D290058

Backed out for causing bc failures at browser_vertical_tabs.js
Backout link
Push with failures
Failure log(s)
Failure line: TEST-UNEXPECTED-FAIL | browser/components/sidebar/tests/browser/browser_vertical_tabs.js | test_toggle_vertical_tabs - Tabstrip now has three tabs - Got 4, expected 3

:japandi you'll need to resolve the test failure described in comment 8 above before we can re-land this

:kcochrane I have already. while you were Out of Work April 1-3

Gotcha, attempting to re-land now

https://hg.mozilla.org/mozilla-central/rev/540afacae380

Backed out for causing bc failures @browser_vertical_tabs.js.

• Backout link
• Push with failures
• Failure Log

https://hg.mozilla.org/mozilla-central/rev/6ec3ef3b55c3