GetScrollPos

GetScrollPos

The GetScrollPos function retrieves the current position of the scroll box (thumb) in the specified scroll bar. The current position is a relative value that depends on the current scrolling range. For example, if the scrolling range is 0 through 100 and the scroll box is in the middle of the bar, the current position is 50.

int GetScrollPos(

HWND hWnd,	// handle of window with scroll bar
int nBar	// scroll bar flags
);

Parameters

hWnd

Identifies 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 examined. This parameter can be one of the following values:

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

Return Values

If the function succeeds, the return value is the current position of the scroll box/

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

Remarks

The GetScrollPos function enables applications to use 32-bit scroll positions. Although the messages that indicate scroll bar position, WM_HSCROLL and WM_VSCROLL, are limited to 16 bits of position data, the functions SetScrollPos, SetScrollRange, GetScrollPos, and GetScrollRange support 32-bit scroll bar position data. Thus, an application can call GetScrollPos while processing either the WM_HSCROLL or WM_VSCROLL messages to obtain 32-bit scroll bar position data.

The limitation on this technique applies to real-time scrolling of a window's content. An application implements such scrolling by processing the WM_HSCROLL or WM_VSCROLL messages that carry the SB_THUMBTRACK notification message, thereby tracking the position of the scroll box, also known as the thumb, while the user moves it. Unfortunately, there is no function to retrieve the thumb's 32-bit position while the user moves it. GetScrollPos provides static position data only; an application can therefore only obtain 32-bit position data before or after a scroll has taken place.