Visual C++ and MFC Programming 2nd Edition

Chapter 18: Progress-Based Controls Visual C++ and MFC Fundamentals

The nSBCode argument is the type of scrolling that is being performed. Its possible

values are:

Value Description Role

SB_THUMBTRACK The thumb is being dragged to a

specific position

SB_UP The thumb has been positioned to the

maximum value of the scroll bar, to

the extreme right

Used to position the thumb to the

highest value of the range, unless the

thumb is already positioned there

SB_LINEUP The thumb is scrolling up, one line at

a time

Used to increase the position of the

thumb, usually by adding 1, unless

the thumb is already positioned there

SB_PAGEUP The thumb is scrolling up, one page

at a time

Refers to the page size of the

SCROLLINFO value to increase the

current position by one page

SB_PAGEDOWN The thumb is scrolling to the bottom,

one page at a time

Refers to the page size of the

SCROLLINFO value to decrease the

current position by one page

SB_LINEDOWN The thumb is scrolling to the bottom,

one line at a time

Used to decrease the position of the

thumb, usually by subtracting 1 to the

current value, unless the thumb is

already positioned there

SB_BOTTOM The thumb has been positioned to the

minimum value of the scroll bar, to

the bottom side of the scroll bar

Used to position the thumb to the

lowest value of the range

SB_THUMBPOSITION Absolute postion

SB_ENDSCROLL End Scroll Used to determine the end of the

scrolling

The nPos argument is used in connection with the SB_THUMBTRACK and the

SB_THUMBPOSITION values of the nSBCode argument. The value of nPos specifies

how much scrolling should be done.

The pScrollBar argument can be used to identify the particular scroll bar control needs to

be dealt with on this OnHScroll() event.

Practical Learning: Using the Scroll Bar Events

1. Generate the WM_VSCROLL message of the dialog box and implement it as
   follows:

void CPreviewerDlg::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)

{

// TODO: Add your message handler code here and/or call default

int CurPos = pScrollBar->GetScrollPos();

switch (nSBCode)

{

case SB_TOP:

CurPos = 0;

break;

case SB_LINEUP:

if (CurPos > 0)