1686414 - Scrollbar thumb surpasses the mouse cursor when clicking and holding on scrollbar

Status: VERIFIED FIXED

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

Description

[Bogdan Maris, Desktop Test Engineering]

Attachment: Gif showing the issue

Affected versions

• Latest Nightly 86.0a1
• Firefox 85.0b7
• Firefox 84.0.2

Affected platforms

• Windows 10 64bit
• macOS 11
• Ubuntu 18.04 64bit

Steps to reproduce

1. Start Firefox
2. Visit a webpage that has lots of content so the scrollbar appears and the scroll elevator is small. (eg theverge.com)
3. Scroll to the top or the bottom of the page
4. Click and hold on the scrollbar outside of the scroll elevator

Expected result

• Scroll elevator stops at the exact place where the mouse cursor is.

Actual result

• Scroll elevator stops at a different place where the mouse cursor is.

Regression range

• Not a regression, using mozregression I went to nightly from 2014 and those still have this issue.

Additional notes

• .Gif attached showing the issue.

Comment 1

[Botond Ballo [:botond]]

I love the name "scroll elevator"!

(But I'm changing it to "scrollbar thumb" for consistency with other bugs and how we refer to it in the code.)

Comment 2

[Timothy Nikkel (:tnikkel)]

The first place I'd look is in layout/xul/nsSliderFrame.cpp, we call StopRepeat and StartRepeat, the repeat might happen too many times?

Comment 3

[Wayne Mery (:wsmwk)]

(I think) I only see this when Firefox is heavily loaded - like it's load or timer dependent

Some older bugs:

• Bug 115232 - clicking on scroll bar can cause thumb to advance twice, overshooting the desired screen
• Bug 441955 - Click in scrollbar registers multiple times
• Bug 496725 - repetitive scrolling with single mouse click in scrollbar
• Bug 1331390 - Over scrolling when mouse down on scrollbar if smooth scroll is enabled (already cited)

Comment 4

[Botond Ballo [:botond]]

Bogdan, could you kindly check if the issue is resolved in the latest nightly? I expect it has been fixed by bug 1331390 but it would be nice to confirm.

Comment 5

[Bogdan Maris, Desktop Test Engineering]

(In reply to Botond Ballo [:botond] from comment #4)

Bogdan, could you kindly check if the issue is resolved in the latest nightly? I expect it has been fixed by bug 1331390 but it would be nice to confirm.

I can confirm that this is no longer an issue on latest Nightly 117.0a1 from today across platforms (Windows 10, macOS 13 and Ubuntu 22.04). I'll mark it as verified fixed.