A TrackBar is similar to a scroll bar control. These controls will generate
WM_HSCROLL or WM_VSCROLL messages like scroll bars do. You can
use getPos()& setPos() to get the position of a track bar and
getScrollInfo() or setScrollInfo() to access other settings as
explained above. Other actions, such as setting the tick marks
along a TrackBar, are possible by sending certain messages. See
the Win32 API documentation for details. An important difference
between TrackBars and ScrollBars is that because TrackBars have
no "thumb" the pointer position can reach to MAXRANGE
but a Scrollbar position can only reach to MAXRANGE-PAGESIZE+1.