Another proposal: Only when mouse cursor is on current screen edge, the selection root scrollable element can be scrolled on its edge. However, this would test harder than current patch. And it may confuse users to change the behavior depending on the window position/size in screen.
Another proposal: Only when mouse cursor is on current screen edge, the selection root scrollable element can be scrolled on its edge. However, this would test harder than current patch. And it may confuse users to change the behavior depending on the window position/size in screen.