Clicking on layer's opacity slider "toggles" instead of sliding

[blackboxlogic@…]

What steps will reproduce the problem?

1. Have JOSM open with a layer.
2. In the 'layers' pane, click the button labeled "change visibility of the selected layer"
3. In the popup, notice that there is an opacity slider, currently at 100%
4. Click in the middle of the slider to select a value near 50%

What is the expected result?

I expect the slider to slide to the position/value clicked by the user

What happens instead?

The slider acts more like a toggle, jumping in the direction of the click to the extreme value in that direction.

Please provide any additional information below. Attach a screenshot if possible.

This slider behaved as expected previously. I do not know when the behavior changed. Recently I have updated JOSM to latest and updated my JAVA version.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-02-26 10:50:27 +0100 (Wed, 26 Feb 2020)
Revision:15937
Build-Date:2020-02-26 09:52:41
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (15937 en) Windows 10 64-Bit
OS Build number: Windows 10 Home 1809 (17763)
Memory Usage: 417 MB / 2048 MB (165 MB allocated, but free)
Java version: 13.0.2+8, AdoptOpenJDK, OpenJDK 64-Bit Server VM
Screen: \Display0 3840x2160
Maximum Screen Size: 3840x2160
Program arguments: [Vienna/Subject.osm, Vienna/Reference.osm, Vienna/Conflated.Create.osm, Vienna/Conflated.Modify.osm]
Dataset consistency test: No problems found

Plugins:
+ measurement (35248)
+ todo (30306)

Last errors/warnings:
- W: extended font config - overriding 'filename.Mongolian_Baiti=monbaiti.ttf' with 'MONBAITI.TTF'

[Hb---]

Behavior of the sliders changed with r15660 as of bug #15946 in January 2020.

I see the slider moving in 10% steps to the mouse pointer when the left mouse button is hold down. Holding down a mouse button while not dragging seems to be very seldom.

[simon04]

Click in the middle of the slider to select a value near 50%

I don't think this is related to r15660 since the change in r15660 only triggers after a double-click. Also, reverting r15660 doesn't change the described behaviour.

[Hb---]

Replying to Hb---:

I see the slider moving in 10% steps to the mouse pointer ...

Occasionally the slider overshoots the mouse pointer and jumps to the extreme value as the bug reporter stated. 1.8.0_242-b08 AdoptOpenJDK x64 on Win 7 x64.