The nsIScrollable is an interface that can be implemented by a control that
supports scrolling. This is a generic interface without concern for the
type of content that may be inside.
Get or set the default scrollbar state for all documents in
this shell.
Get information about whether the vertical and horizontal scrollbars are
currently visible. If you are only interested in one of the visibility
settings pass nullptr in for the one you aren’t interested in.
Constants declaring the two scroll orientations a scrollbar can be in.
ScrollOrientation_X - Horizontal scrolling. When passing this
in to a method you are requesting or setting data for the
horizontal scrollbar.
ScrollOrientation_Y - Vertical scrolling. When passing this
in to a method you are requesting or setting data for the
vertical scrollbar.
Constants declaring the states of the scrollbars.
ScrollPref_Auto - bars visible only when needed.
ScrollPref_Never - bars never visible, even when scrolling still possible.
ScrollPref_Always - bars always visible, even when scrolling is not possible