SetScrollPos function (winuser.h)

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.

Syntax

int SetScrollPos(
  [in] HWND hWnd,
  [in] int  nBar,
  [in] int  nPos,
  [in] BOOL bRedraw
);

Parameters

[in] hWnd

Type: HWND

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

[in] nBar

Type: int

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

[in] nPos

Type: int

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.

[in] bRedraw

Type: BOOL

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 value

Type: int

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.

If the nBar parameter is SB_CTL and the window specified by the hWnd parameter is not a system scroll bar control, the system sends the SBM_SETPOS message to the window to set scroll bar information. This allows SetScrollPos to operate on a custom control that mimics a scroll bar. If the window does not handle the SBM_SETPOS message, the SetScrollPos function fails.

Requirements

See also

GetScrollInfo

GetScrollPos

GetScrollRange

Reference

SetScrollInfo

SetScrollRange