The GetScrollInfo function retrieves the parameters of a scroll bar, including the minimum and maximum scrolling positions, the page size, and the position of the scroll box (thumb).
BOOL GetScrollInfo(
HWND hwnd, // handle to window with scroll bar
int fnBar, // scroll bar flag
LPSCROLLINFO lpsi // pointer to structure for scroll parameters
);
Value | Meaning |
---|---|
SB_CTL | Retrieves the parameters for a scroll bar control. The hwnd parameter must be the handle to the scroll bar control. |
SB_HORZ | Retrieves the parameters for the given window's standard horizontal scroll bar. |
SB_VERT | Retrieves the parameters for the given window's standard vertical scroll bar. |
The fMask member can be a combination of the following values:
Value | Meaning |
---|---|
SIF_PAGE | Copies the scroll page to the nPage member of the SCROLLINFO structure pointed to by lpsi. |
SIF_POS | Copies the scroll position to the nPos member of the SCROLLINFO structure pointed to by lpsi. |
SIF_RANGE | Copies the scroll range to the nMin and nMax members of the SCROLLINFO structure pointed to by lpsi. |
SIF_TRACKPOS | Copies the current scroll box tracking position to the nTrackPos member of the SCROLLINFO structure pointed to by lpsi. |
If the function retrieved any values, the return value is nonzero.
If the function does not retrieve any values, the return value is zero. To get extended error information, call GetLastError.
The GetScrollInfo function enables applications to use 32-bit scroll positions. Although the messages that indicate scroll-bar position, WM_HSCROLL and WM_VSCROLL, provide only 16 bits of position data, the functions SetScrollInfo and GetScrollInfo provide 32 bits of scroll-bar position data. Thus, an application can call GetScrollInfo while processing either the WM_HSCROLL or WM_VSCROLL messages to obtain 32-bit scroll-bar position data.
To get the 32-bit position of the scroll box (thumb) during a SB_THUMBTRACK notification in a WM_HSCROLL or WM_VSCROLL message, call GetScrollInfo with the SIF_TRACKPOS value in the fMask member of the SCROLLINFO structure. The function returns the tracking position of the scroll box in the nTrackPos member of the SCROLLINFO structure. This allows you to get the position of the scroll box as the user moves it. The following sample code illustrates the technique.
SCROLLINFO si;
case WM_HSCROLL:
switch(LOWORD(wparam)) {
case SB_THUMBTRACK:
// Initialize SCROLLINFO structure
ZeroMemory(&si, sizeof(SCROLLINFO));
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_TRACKPOS;
// Call GetScrollInfo to get current tracking
// position in si.nTrackPos
if (!GetScrollInfo(hwnd, SB_HORZ, &si) )
return 1; // GetScrollInfo failed
break;
.
.
.
}
Windows NT: Requires version 3.51 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Import Library: Use user32.lib.
Scroll Bars Overview, Scroll Bar Functions, SCROLLINFO, SetScrollInfo, WM_HSCROLL, WM_VSCROLL