Scrollbar inconsistently handles clicking on scrollbar region (not thumb)

[carlos-zamora]

Describe the bug

From microsoft/terminal#18063

Typically when mouse click the scrollbar(not the thumb), hold the mouse button down. The scrollbar will:
page up, , page up, page up, page up, page up,...
Then thumb will stop at the mouse pointer position.
Instead, there are 3 random behaviors.

1. Page up/down once and stop.
2. Thumb not stop. And reach the top/bottom position.
3. Thumb move across the mouse pointer position.

Video.webm

Steps to reproduce the bug

1. Go to a page with a long scroll region in the WinUI 2 gallery (I used ListView)
2. Click and hold on the scrollbar region (not the thumb)

Expected behavior

We should be consistent. I'd expect it to scroll to the pointer position.

Screenshots

No response

NuGet package version

WinUI2. Also repros in WinUI3

Windows version

No response

Additional context

No response

[karkarl]

Does this bug also repro in WinUI3? This may not meet the bar for WinUI2 servicing.

[carlos-zamora]

Yup! Just tried it in WinUI 3 controls gallery (All samples, then made the window very narrow).