SetScrollPos

The SetScrollPos function sets the position of the scroll box (thumb) in the specified scroll bar and, if requested, redraws the scroll bar to reflect the new position of the scroll box.

The SetScrollPos function is provided for backward compatibility. New applications should use the SetScrollInfo function.

int SetScrollPos(
  HWND hWnd,     // handle to window with scroll bar
  int nBar,      // scroll bar flag
  int nPos,      // new position of scroll box
  BOOL bRedraw   // redraw flag
);
 

Parameters

hWnd

Handle to a scroll bar control or a window with a standard scroll bar, depending on the value of the nBar parameter.

nBar

Specifies the scroll bar to be set. This parameter can be one of the following values:

Value	Meaning
SB_CTL	Sets the position of the scroll box in a scroll bar control. The hWnd parameter must be the handle to the scroll bar control.
SB_HORZ	Sets the position of the scroll box in a window's standard horizontal scroll bar.
SB_VERT	Sets the position of the scroll box in a window's standard vertical scroll bar.

nPos

Specifies the new position of the scroll box. The position must be within the scrolling range. For more information about the scrolling range, see the SetScrollRange function.

bRedraw

Specifies whether the scroll bar is redrawn to reflect the new scroll box position. If this parameter is TRUE, the scroll bar is redrawn. If it is FALSE, the scroll bar is not redrawn.

Return Values

If the function succeeds, the return value is the previous position of the scroll box.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

If the scroll bar is redrawn by a subsequent call to another function, setting the bRedraw parameter to FALSE is useful.

Because the messages that indicate scroll bar position, WM_HSCROLL and WM_VSCROLL, are limited to 16 bits of position data, applications that rely solely on those messages for position data have a practical maximum value of 65,535 for the SetScrollPos function's nPos parameter.

However, because the SetScrollInfo, SetScrollPos, SetScrollRange, GetScrollInfo, GetScrollPos, and GetScrollRange functions support 32-bit scroll bar position data, there is a way to circumvent the 16-bit barrier of the WM_HSCROLL and WM_VSCROLL messages. See GetScrollInfo for a description of the technique.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 2.0 or later.
  Header: Declared in winuser.h.
  Import Library: Use user32.lib.

See Also

Scroll Bars Overview, Scroll Bar Functions, GetScrollInfo, GetScrollPos, GetScrollRange, SetScrollInfo, SetScrollRange