Make payment scrolling smoother with smaller increment

[jim618]

I find the payment window scrolling a bit jerky. It might look better with a smaller scroll increment so that it is smoother (albeit slower).

[jim618]

Experimenting you only got a smooth scrool with a very small increment (4 pixels or so) which is too slow to be useful. Settting the scroll increment to be the row height works quite well and you can still navigate long lists so I have set it to that.

Awaiting review and closing.

[gary-rowe]

Works well. Closing.