用滚动条函数!GetScrollInfo
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
);
Parameters
hwnd
Handle to a scroll bar control or a window with a standard scroll bar, depending on the value of the fnBar parameter.
fnBar
Specifies the type of scroll bar for which to retrieve parameters. This parameter can be one of the following values: 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.
lpsi
Pointer to a SCROLLINFO structure. Before calling GetScrollInfo, set the cbSize member of the structure to sizeof(SCROLLINFO), and set the fMask member to specify the scroll bar parameters to retrieve. Before returning, the function copies the specified parameters to the appropriate members of the structure.
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. Return Values
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, callGetLastError.Res
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;
.
.
.
}
QuickInfo
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.SCROLLINFO
The SCROLLINFO structure contains scroll bar parameters to be set by the SetScrollInfo function (or SBM_SETSCROLLINFO message), or retrieved by the GetScrollInfo function (or SBM_GETSCROLLINFO message). typedef struct tagSCROLLINFO { // si
UINT cbSize;
UINT fMask;
int nMin;
int nMax;
UINT nPage;
int nPos;
int nTrackPos;
} SCROLLINFO;
typedef SCROLLINFO FAR *LPSCROLLINFO;
Members
cbSize
Specifies the size, in bytes, of this structure.
fMask
Specifies the scroll bar parameters to set or retrieve. This member can be a combination of the following values: Value Meaning
SIF_ALL Combination of SIF_PAGE, SIF_POS, SIF_RANGE, and SIF_TRACKPOS.
SIF_DISABLENOSCROLL This value is used only when setting a scroll bar's parameters. If the scroll bar's new parameters make the scroll bar unnecessary, disable the scroll bar instead of removing it.
SIF_PAGE The nPage member contains the page size for a proportional scroll bar.
SIF_POS The nPos member contains the scroll box position, which is not updated while the user drags the scroll box.
SIF_RANGE The nMin and nMax members contain the minimum and maximum values for the scrolling range.
SIF_TRACKPOS The nTrackPos member contains the current position of the scroll box while the user is dragging it.
nMin
Specifies the minimum scrolling position.
nMax
Specifies the maximum scrolling position.
nPage
Specifies the page size. A scroll bar uses this value to determine the appropriate size of the proportional scroll box.
nPos
Specifies the position of the scroll box.
nTrackPos
Specifies the immediate position of a scroll box that the user is dragging. An application can retrieve this value while processing the SB_THUMBTRACK notification message. An application cannot set the immediate scroll position; the SetScrollInfo function ignores this member.
QuickInfo
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.
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
);
Parameters
hwnd
Handle to a scroll bar control or a window with a standard scroll bar, depending on the value of the fnBar parameter.
fnBar
Specifies the type of scroll bar for which to retrieve parameters. This parameter can be one of the following values: 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.
lpsi
Pointer to a SCROLLINFO structure. Before calling GetScrollInfo, set the cbSize member of the structure to sizeof(SCROLLINFO), and set the fMask member to specify the scroll bar parameters to retrieve. Before returning, the function copies the specified parameters to the appropriate members of the structure.
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. Return Values
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, callGetLastError.Res
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;
.
.
.
}
QuickInfo
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.SCROLLINFO
The SCROLLINFO structure contains scroll bar parameters to be set by the SetScrollInfo function (or SBM_SETSCROLLINFO message), or retrieved by the GetScrollInfo function (or SBM_GETSCROLLINFO message). typedef struct tagSCROLLINFO { // si
UINT cbSize;
UINT fMask;
int nMin;
int nMax;
UINT nPage;
int nPos;
int nTrackPos;
} SCROLLINFO;
typedef SCROLLINFO FAR *LPSCROLLINFO;
Members
cbSize
Specifies the size, in bytes, of this structure.
fMask
Specifies the scroll bar parameters to set or retrieve. This member can be a combination of the following values: Value Meaning
SIF_ALL Combination of SIF_PAGE, SIF_POS, SIF_RANGE, and SIF_TRACKPOS.
SIF_DISABLENOSCROLL This value is used only when setting a scroll bar's parameters. If the scroll bar's new parameters make the scroll bar unnecessary, disable the scroll bar instead of removing it.
SIF_PAGE The nPage member contains the page size for a proportional scroll bar.
SIF_POS The nPos member contains the scroll box position, which is not updated while the user drags the scroll box.
SIF_RANGE The nMin and nMax members contain the minimum and maximum values for the scrolling range.
SIF_TRACKPOS The nTrackPos member contains the current position of the scroll box while the user is dragging it.
nMin
Specifies the minimum scrolling position.
nMax
Specifies the maximum scrolling position.
nPage
Specifies the page size. A scroll bar uses this value to determine the appropriate size of the proportional scroll box.
nPos
Specifies the position of the scroll box.
nTrackPos
Specifies the immediate position of a scroll box that the user is dragging. An application can retrieve this value while processing the SB_THUMBTRACK notification message. An application cannot set the immediate scroll position; the SetScrollInfo function ignores this member.
QuickInfo
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.
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The SetScrollInfo function sets the parameters of a scroll bar, including the minimum and maximum scrolling positions, the page size, and the position of the scroll box (thumb). The function also redraws the scroll bar, if requested.int SetScrollInfo(
HWND hwnd, // handle to window with scroll bar
int fnBar, // scroll bar flag
LPSCROLLINFO lpsi,
// pointer to structure with scroll parameters
BOOL fRedraw // redraw flag
);
Parameters
hwnd
Handle to a scroll bar control or a window with a standard scroll bar, depending on the value of the fnBar parameter.
fnBar
Specifies the type of scroll bar for which to set parameters. This parameter can be one of the following values: Value Meaning
SB_CTL Sets the parameters of a scroll bar control. The hwnd parameter must be the handle to the scroll bar control.
SB_HORZ Sets the parameters of the given window's standard horizontal scroll bar.
SB_VERT Sets the parameters of the given window's standard vertical scroll bar.
lpsi
Pointer to a SCROLLINFO structure. Before calling SetScrollInfo, set the cbSize member of the structure to sizeof(SCROLLINFO), set the fMask member to indicate the parameters to set, and specify the new parameter values in the appropriate members.
The fMask member can be a combination of the following values: Value Meaning
SIF_DISABLENOSCROLL Disables the scroll bar instead of removing it, if the scroll bar's new parameters make the scroll bar unnecessary.
SIF_PAGE Sets the scroll page to the value specified in the nPage member of the SCROLLINFO structure pointed to by lpsi.
SIF_POS Sets the scroll position to the value specified in the nPos member of the SCROLLINFO structure pointed to by lpsi.
SIF_RANGE Sets the scroll range to the value specified in the nMin and nMax members of the SCROLLINFO structure pointed to by lpsi. fRedraw
Specifies whether the scroll bar is redrawn to reflect the changes to the scroll bar. If this parameter is TRUE, the scroll bar is redrawn, otherwise, it is not redrawn.
Return Values
The return value is the current position of the scroll box. Res
The SetScrollInfo function performs range checking on the values specified by the nPage and nPos members of the SCROLLINFO structure. The nPage member must specify a value from 0 to nMax - nMin +1. The nPos member must specify a value between nMin and nMax - max(nPage – 1, 0). If either value is beyond its range, the function sets it to a value that is just within the range. Windows CE: In Windows CE 2.0, if you pass a null pointer in the lpsi parameter, SetScrollInfo returns zero, rather than the current position of the scroll box. QuickInfo
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.