Inconsistent use of space and placement with tooltips

[skyper]

Looking at #19585, I found a strange behavior of tooltips at least in relation editor and changeset manager. In relation panel tooltips are disabled for some reason.

What steps will reproduce the problem?

1. Have a relation with some members with quite some tags (30+)
2. In relation manager, mouse hover over the member list

What is the expected result?

1. If possible show all tags by using the full screen height
2. No jumps but a centered placement

What happens instead?

1. Context is cut of
2. Jumps in placement of tooltips as it usually is placed below if enough space is available.
3. Sometime the full screen height is used but it is unpredictable

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

Please find attached session​ with two more or less identical layers. The first is better for the jumping effect and the second makes it easier to notice the full screen height. Use the route_master (#69754).

In changeset manager, CS #97252806 is a good example. After downloading the context, mouse hover over the objects in content tab to notice the same issues.

Do not know if this is related to #19585 as I stopped using Metal LaF.

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2021-01-11 00:39:15 +0100 (Mon, 11 Jan 2021)
Revision:17454
Build-Date:2021-01-11 02:30:53
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (17454 en) Linux Debian GNU/Linux 10 (buster)
Java version: 11.0.9.1+1-post-Debian-1deb10u2, Debian, OpenJDK 64-Bit Server VM
Look and Feel: com.formdev.flatlaf.FlatDarkLaf
Java package: openjdk-11-jre:amd64-11.0.9.1+1-1~deb10u2
Environment variable LANG: en_US.utf8
libcommons-compress-java: libcommons-compress-java:all-1.18-2+deb10u1
libcommons-logging-java: libcommons-logging-java:all-1.2-2
fonts-noto: fonts-noto:all-20181227-1
liboauth-signpost-java: liboauth-signpost-java:all-1.2.1.2-2
Dataset consistency test: No problems found

Plugins:
+ flatlaf (35679)

[skyper]

example session with two layers