Brew MP 1.0.2
This function retrieve the rectangle of the vertical scrollbar fill area, which is
the area inside the scrollbar border area that contains the handle where
where PROP_SCROLLSTYLE is set to SCROLL_BOTH.
int IWidget_GetVScrollFillRect(IWidget *pif, AEERect *prc)
AEE_SUCCESS - The widget was able to successfully retrieve the scrollbar fill rectangle.
AEE_EFAILED - The widget was unable to retrieve the scrollbar fill rectangle.