Scroll behavior issues

[monodop]

I originally wanted to report a weird interaction between floating elements and scrolling elements underneath, but I think overall drag scrolling is a bit weird at the moment, because:

• floating elements with pointer capture does not affect obscured scrollable elements below

• it does not matter where you started your click, scrolling works on all scrollable elements as long as the mouse button is held down. I don't have a touchscreen to test on, but I think it this would be especially problematic in that environment.

• if you drag past the scrollable area, the offset from your original starting point will change

• drag scrolling doesn't seem to very accurately follow the cursor (this example also shows awkward behavior with nested scroll areas)

In my opinion, drag scrolling should probably track which element was clicked during the start of the scroll, and the coordinates of that interaction, in order to determine where the scroll position should be.