At first it seemed to me that arma2 scrollbar can be set for any control.
Having looked at the config i was a bit disappointed, scrollbar is set for a controls-group, it draws a scrollbar when it contains controls of larger size, than itself.
(see: configFile >> "RscDisplayDiary", or "AddOns\ui\config.cpp")
It is the same as it was before, in ArmA1. And the main problem is that when we want to have scrollable html-control or strucured-text-control we need to know it actual size that depends on volume of the loaded text (htmlLoad or ctrlSetStructuredText).
Not especially hoping for success, I tried to set scrollbar classes (Scrollbar, VScrollbar, HScrollbar), for other controls, but it didn't work.
Somebody knows, how it works ingame, or how it can be workaround? Any ideas.