[TreeDataGrid] Can't select the bottom row

[clintsinger]

Describe the bug

When the horizontal scrollbar is visible the bottom row of the TreeDataGrid isn't selectable.

To Reproduce

1. Create TreeDataGrid and add enough data to show scrollbars
2. Click on the last row
3. Observe that the horizontal scrollbar blocks selecting the last row
4. Modify data / UI so that the horizontal scrollbar disappears
5. Observe that you can select the bottom row

Expected behavior

You should be able to select the bottom row even if the scrollbar is visible.

Avalonia version

Avalonia: 11.3.0, Avalonia.Controls.TreeDataGrid: 11.1.1

OS

No response

Additional context

No response

[maxkatz6]

TreeDataGrid might need to enforce padding, when scrollbar is auto hiding.
You also should be able to set padding there as a workaround.

[clintsinger]

This issue is similar to #371 in that if you don't have the theme installed then the hit testing for the row doesn't work correctly.

It would be great if it could still work without the theme. Also a bit more bottom padding would be good by default because the scrollbar and and the bottom row fight for the same space.