1131944 - <select> dropdown can appear in the wrong position when inside a container with position:sticky

Status: NEW

(Core :: Layout, defect)

Description

[Matthew N. [:MattN]]

Attachment: Testcase (scroll while the dropdown is open)

I regularly see the <select> dropdown in the wrong position on my bug dependency tree dashboard. I'm not sure of all of the possible ways to reproduce the issue but scrolling upwards while a <select> dropdown popup is open seems to trigger it. Once it's in the wrong position, it will remain in that wrong position upon reopening too. Click and keyboard behaviour becomes wonky when the popup is in the wrong position.

Comment 1

[Matthew N. [:MattN]]

Attachment: Video showing a mild version of the problem using the testcase

This shows a mild version of the problem using my testcase. On my bug dashboard I regularly see the dropdown vertical position off by multiple centimetres.

Comment 3

[Corey Ford [:coyotebush]]

I wonder if this could be a case of a missing MovePositionBy. See bug 911786 comment 12 to 17. Although the <select> itself doesn't need to be position: sticky to show the problem.