int GetScrollPos( int nBar )const
Specifies the current position of the scroll box in the scroll bar if successful; otherwise 0.
Retrieves the current position of the scroll box of a scroll bar.
The current position is a relative value that depends on the current scrolling range.
For example, if the scrolling range is 50 to 100 and the scroll box is in the middle of the bar, the current position is 75.