Install interface of last item in Library/Boards Manager may not be accessible

[per1234]

Describe the problem

The IDE's Library Manager and Boards Manager list the libraries and boards platforms that are available.

Since there are >5000 libraries, and even the primary package index alone contains a significant number of boards platforms, the length of the list will often exceed the vertical display area of the view, meaning the user will scroll down to reach items lower on the list.

When the mouse pointer is hovered over one of the list items, a version menu and "INSTALL" button are added at the bottom of the item.

🐛 The interface elements are not accessible for the last item on the list when the list height is equal to or greater than the vertical dimensions of the view.

To reproduce

1. Open the Library Manager view in the Arduino IDE.
2. Type servo in the "Filter your search..." field.
   ⓘ This is only an arbitrary example of a list that exceeds the height of the view.
3. Scroll to the bottom of the list.
4. Hover the mouse pointer over the last item on the list
   🐛 The version menu and "INSTALL" button are not accessible.
5. Use the mouse wheel to scroll the list down farther.
   🐛 The list does not scroll down farther.

Expected behavior

The installation interface is accessible on all Library Manager and Boards Manager items.

Arduino IDE version

2.0.0-rc9.2.snapshot-20cc34c

Operating system

Windows, Linux

Operating system version

Windows 10, Ubuntu 20.04

Additional context

I bisected the introduction to 5cb9166 (does not occur with the build for 7828cc1)

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Even prior to the regression, the scrollbar didn't scroll the list down far enough for the interface to be visible on hover. However, previously you could use the mouse wheel to scroll it farther to reach the interface.

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After the changes made in #1385 to fix other scrolling-related issues, I find that it is sometimes possible to reach the interface, but not reliably:

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Related:

• Scrollbar does not reach end of Library Manager list #1380
• Scrollbar trails increasingly behind mouse pointer position while scrolling Library Manager #1381

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest nightly build
• My report contains all necessary details