1606358 - unable to drag scroll bar thumb for div with height 68px and many rows of content

Status: NEW

(Core :: Layout: Scrolling and Overflow, defect, P3)

Description

[Jeff]

Attachment: ScrollThumbIssue.html

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0

Steps to reproduce:

1.Create a div
2.Add 90 lines of content (see attached file)
3.size div height to the following
<div style="height: 68px; width: 60px; overflow-y:scroll; white-space: nowrap;">
4 try to drag the scroll bar thumb vertically down or up using mouse

jsbin to try https://jsbin.com/rorivif/edit?html,output

in jsbin optionally change div style="height:69px;" and you can now move the scrollbar thumb but does not page well, jumps to last item. Also interesting if you use vert scroll down arrow, then you can use vert scroll thumb to drag up.

Actual results:

vertical scrollbar thumb does not move on firefox/windows

Expected results:

vertical scrollbar thumb allows user to page down/up in content

Comment 1

[Patrick (he/him)]

Able to reproduce this issue on Beta 72 and Nightly 73.0a1 (2019-12-31) .

Comment 2

[Botond Ballo [:botond]]

Works on Linux, probably because the lack of scrollbar buttons frees up more space for the thumb.

I'm guessing this is an edge case related to the scrollbar being very short and there not being much space to render / drag the scrollbar.

Comment 3

[Jonathan Kew [:jfkthame]]

Setting the element height of the testcase to 26px on macOS results in a similar issue: I see a scrollbar thumb, but it occupies the full height of the scrollbar and can't be moved anywhere.

Comment 4

[Patrick (he/him)]

Bug appears to be regression - last good build 2019-03-28, first bad build 2019-03-29
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=00c5ef76d951a834ccf87c83d04e0878f6c2c515&tochange=bd1e28b0143bdcff0798b0e6a4f54791c41192e8
Suspect regressing bug 1539684

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1539684