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分享SetWindowLongPt函数在64位C++使用中的类型转换问题
SetWindowLongPt函数在64位C++使用中的类型转换问题
我的函数使用：SetWindowLongPtr(hWnd,GWLP_USERDATA,(LONG_PTR)pWindow);
pWindow是我的一个类指针
编绎提示：warning C4244: 'argument' : conversion from 'LONG_PTR' to 'LONG', possible loss of data
求高手指点。谢谢。
我的函数使用：SetWindowLongPtr(hWnd,GWLP_USERDATA,(LONG_PTR)pWindow);
pWindow是我的一个类指针
编绎提示：warning C4244: 'argument' : conversion from 'LONG_PTR' to 'LONG', possible loss of data
求高手指点。谢谢。
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赵4老师 2012-01-16
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SetWindowLongPtr Function
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The SetWindowLongPtr function changes an attribute of the specified window. The function also sets a value at the specified offset in the extra window memory.
This function supersedes the SetWindowLong function. To write code that is compatible with both 32-bit and 64-bit versions of Microsoft Windows, use SetWindowLongPtr.
Syntax
LONG_PTR SetWindowLongPtr( HWND hWnd,
int nIndex,
LONG_PTR dwNewLong
);
Parameters
hWnd
[in] Handle to the window and, indirectly, the class to which the window belongs. The SetWindowLongPtr function fails if the window specified by the hWnd parameter does not belong to the same process as the calling thread.
nIndex
[in] Specifies the zero-based offset to the value to be set. Valid values are in the range zero through the number of bytes of extra window memory, minus the size of an integer. To set any other value, specify one of the following values.
GWL_EXSTYLE
Sets a new extended window style. For more information, see CreateWindowEx.
GWL_STYLE
Sets a new window style.
GWLP_WNDPROC
Sets a new address for the window procedure.
GWLP_HINSTANCE
Sets a new application instance handle.
GWLP_ID
Sets a new identifier of the window.
GWLP_USERDATA
Sets the user data associated with the window. This data is intended for use by the application that created the window. Its value is initially zero.
The following values are also available when the hWnd parameter identifies a dialog box.
DWLP_DLGPROC
Sets the new pointer to the dialog box procedure.
DWLP_MSGRESULT
Sets the return value of a message processed in the dialog box procedure.
DWLP_USER
Sets new extra information that is private to the application, such as handles or pointers.
dwNewLong
[in] Specifies the replacement value.
Return Value
If the function succeeds, the return value is the previous value of the specified offset.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
If the previous value is zero and the function succeeds, the return value is zero, but the function does not clear the last error information. To determine success or failure, clear the last error information by calling SetLastError(0), then call SetWindowLongPtr. Function failure will be indicated by a return value of zero and a GetLastError result that is nonzero.
Remarks
Certain window data is cached, so changes you make using SetWindowLongPtr will not take effect until you call the SetWindowPos function.
If you use SetWindowLongPtr with the GWLP_WNDPROC index to replace the window procedure, the window procedure must conform to the guidelines specified in the description of the WindowProc callback function.
If you use SetWindowLongPtr with the DWLP_MSGRESULT index to set the return value for a message processed by a dialog box procedure, the dialog box procedure should return TRUE directly afterward. Otherwise, if you call any function that results in your dialog box procedure receiving a window message, the nested window message could overwrite the return value you set by using DWLP_MSGRESULT.
Calling SetWindowLongPtr with the GWLP_WNDPROC index creates a subclass of the window class used to create the window. An application can subclass a system class, but should not subclass a window class created by another process. The SetWindowLongPtr function creates the window subclass by changing the window procedure associated with a particular window class, causing the system to call the new window procedure instead of the previous one. An application must pass any messages not processed by the new window procedure to the previous window procedure by calling CallWindowProc. This allows the application to create a chain of window procedures.
Reserve extra window memory by specifying a nonzero value in the cbWndExtra member of the WNDCLASSEX structure used with the RegisterClassEx function.
Do not call SetWindowLongPtr with the GWLP_HWNDPARENT index to change the parent of a child window. Instead, use the SetParent function.
If the window has a class style of CS_CLASSDC or CS_PARENTDC, do not set the extended window styles WS_EX_COMPOSITED or WS_EX_LAYERED.
Function Information
Minimum DLL Version user32.dll
Header Declared in Winuser.h, include Windows.h
Import library User32.lib
Minimum operating systems Windows 95, Windows NT 3.1
Unicode Implemented as ANSI and Unicode versions.
See Also
Window Class Overview, CallWindowProc, GetWindowLongPtr, RegisterClassEx, SetParent, WindowProc, WNDCLASSEX
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© 2005 Microsoft Corporation. All rights reserved.
SetWindowLongPtr Function
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The SetWindowLongPtr function changes an attribute of the specified window. The function also sets a value at the specified offset in the extra window memory.
This function supersedes the SetWindowLong function. To write code that is compatible with both 32-bit and 64-bit versions of Microsoft Windows, use SetWindowLongPtr.
Syntax
LONG_PTR SetWindowLongPtr( HWND hWnd,
int nIndex,
LONG_PTR dwNewLong
);
Parameters
hWnd
[in] Handle to the window and, indirectly, the class to which the window belongs. The SetWindowLongPtr function fails if the window specified by the hWnd parameter does not belong to the same process as the calling thread.
nIndex
[in] Specifies the zero-based offset to the value to be set. Valid values are in the range zero through the number of bytes of extra window memory, minus the size of an integer. To set any other value, specify one of the following values.
GWL_EXSTYLE
Sets a new extended window style. For more information, see CreateWindowEx.
GWL_STYLE
Sets a new window style.
GWLP_WNDPROC
Sets a new address for the window procedure.
GWLP_HINSTANCE
Sets a new application instance handle.
GWLP_ID
Sets a new identifier of the window.
GWLP_USERDATA
Sets the user data associated with the window. This data is intended for use by the application that created the window. Its value is initially zero.
The following values are also available when the hWnd parameter identifies a dialog box.
DWLP_DLGPROC
Sets the new pointer to the dialog box procedure.
DWLP_MSGRESULT
Sets the return value of a message processed in the dialog box procedure.
DWLP_USER
Sets new extra information that is private to the application, such as handles or pointers.
dwNewLong
[in] Specifies the replacement value.
Return Value
If the function succeeds, the return value is the previous value of the specified offset.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
If the previous value is zero and the function succeeds, the return value is zero, but the function does not clear the last error information. To determine success or failure, clear the last error information by calling SetLastError(0), then call SetWindowLongPtr. Function failure will be indicated by a return value of zero and a GetLastError result that is nonzero.
Remarks
Certain window data is cached, so changes you make using SetWindowLongPtr will not take effect until you call the SetWindowPos function.
If you use SetWindowLongPtr with the GWLP_WNDPROC index to replace the window procedure, the window procedure must conform to the guidelines specified in the description of the WindowProc callback function.
If you use SetWindowLongPtr with the DWLP_MSGRESULT index to set the return value for a message processed by a dialog box procedure, the dialog box procedure should return TRUE directly afterward. Otherwise, if you call any function that results in your dialog box procedure receiving a window message, the nested window message could overwrite the return value you set by using DWLP_MSGRESULT.
Calling SetWindowLongPtr with the GWLP_WNDPROC index creates a subclass of the window class used to create the window. An application can subclass a system class, but should not subclass a window class created by another process. The SetWindowLongPtr function creates the window subclass by changing the window procedure associated with a particular window class, causing the system to call the new window procedure instead of the previous one. An application must pass any messages not processed by the new window procedure to the previous window procedure by calling CallWindowProc. This allows the application to create a chain of window procedures.
Reserve extra window memory by specifying a nonzero value in the cbWndExtra member of the WNDCLASSEX structure used with the RegisterClassEx function.
Do not call SetWindowLongPtr with the GWLP_HWNDPARENT index to change the parent of a child window. Instead, use the SetParent function.
If the window has a class style of CS_CLASSDC or CS_PARENTDC, do not set the extended window styles WS_EX_COMPOSITED or WS_EX_LAYERED.
Function Information
Minimum DLL Version user32.dll
Header Declared in Winuser.h, include Windows.h
Import library User32.lib
Minimum operating systems Windows 95, Windows NT 3.1
Unicode Implemented as ANSI and Unicode versions.
See Also
Window Class Overview, CallWindowProc, GetWindowLongPtr, RegisterClassEx, SetParent, WindowProc, WNDCLASSEX
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© 2005 Microsoft Corporation. All rights reserved.
