Handling The ScrollBar

Here is a simple example illustrating how to programmatically handle the scroll bar (and it's messages).

1. First set up the dimensions of the control:

  SCROLLINFO ScrollInfo;
  ScrollInfo.cbSize = sizeof(ScrollInfo);     // size of this structure
  ScrollInfo.fMask = SIF_ALL;                 // parameters to set
  ScrollInfo.nMin = 0;                        // minimum scrolling position
  ScrollInfo.nMax = 100;                      // maximum scrolling position
  ScrollInfo.nPage = 40;                      // the page size of the scroll box
  ScrollInfo.nPos = 50;                       // initial position of the scroll box
  ScrollInfo.nTrackPos = 0;                   // immediate position of a scroll box that the user is dragging
  m_MyScrollBar.SetScrollInfo(&ScrollInfo);

void CMyScrollBar::VScroll(UINT nSBCode, UINT nPos) 
{
  SCROLLINFO ScrollInfo;
  GetScrollInfo(&ScrollInfo);  // get information about the scroll

  switch(nSBCode)
  {
    case SB_BOTTOM:         //Scrolls to the lower right. 
      break;

    case SB_ENDSCROLL:      //Ends scroll. 
      break;

    case SB_LINEDOWN:       //Scrolls one line down. 
      SetScrollPos(GetScrollPos() + 1);
      break;

    case SB_LINEUP:         //Scrolls one line up. 
      SetScrollPos(GetScrollPos() - 1);
      break;

    case SB_PAGEDOWN:       //Scrolls one page down. 
      SetScrollPos(GetScrollPos() + ScrollInfo.nPage);
      break;

    case SB_PAGEUP:         //Scrolls one page up. 
      SetScrollPos(GetScrollPos() - ScrollInfo.nPage);
      break;

    case SB_THUMBPOSITION:  //The user has dragged the scroll box (thumb) and released the mouse button. The nPos parameter indicates the position of the scroll box at the end of the drag operation. 
      break;

    case SB_THUMBTRACK:     //The user is dragging the scroll box. This message is sent repeatedly until the user releases the mouse button. The nPos parameter indicates the position that the scroll box has been dragged to. 
      SetScrollPos(nPos);
      break;

    case SB_TOP:            //Scrolls to the upper left. 
      break;
  }
}