一份很有价值的子类化的源代码！

一份很有价值的子类化的源代码！

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--- 一份很有价值的子类化的源代码！ (http://www.webasp.net/article/12/11931.htm)

-- 作者：未知
-- 发布日期： 2004-07-19

' 新建一个 ActiveX DLL 工程，名称 SmartSubClassLib

' 以下代码放在标准模块里，模块名 mSmartSubClass

' ----------------------------------------------------
' Module mSmartSubClass
'
' Version... 1.0
' Date...... 24 April 2001
'
' Copyright (C) 2001 Andr閟 Pons (andres@vbsmart.com)
' ----------------------------------------------------

'API declarations:
Option Explicit

Public Const SSC_OLDPROC = "SSC_OLDPROC"
Public Const SSC_OBJADDR = "SSC_OBJADDR"

Private Declare Function GetProp Lib "user32" Alias "GetPropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String) As Long

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
Destination As Any, _
Source As Any, _
ByVal Length As Long)

'
' Function StartSubclassWindowProc()
'
' This is the first windowproc that receives messages
' for all subclassed windows.
' The aim of this function is to just collect the message
' and deliver it to the right SmartSubClass instance.
'
Public Function SmartSubClassWindowProc( _
ByVal hWnd As Long, _
ByVal uMsg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long

Dim lRet As Long
Dim oSmartSubClass As SmartSubClass

'Get the memory address of the class instance...
lRet = GetProp(hWnd, SSC_OBJADDR)

If lRet <> 0 Then
'oSmartSubClass will point to the class instance
'without incrementing the class reference counter...
CopyMemory oSmartSubClass, lRet, 4

'Send the message to the class instance...
SmartSubClassWindowProc = oSmartSubClass.WindowProc(hWnd, _
uMsg, wParam, lParam)

'Remove the address from memory...
CopyMemory oSmartSubClass, 0&, 4
End If

End Function

' 以下代码放在类模块里，模块名 SmartSubClass

' ----------------------------------------------------
' Class SmartSubClass
'
' Version... 1.0
' Date...... 24 April 2001
'
' Copyright (C) 2001 Andr閟 Pons (andres@vbsmart.com)
' ----------------------------------------------------

Option Explicit

'Public event:
Public Event NewMessage( _
ByVal hWnd As Long, _
ByRef uMsg As Long, _
ByRef wParam As Long, _
ByRef lParam As Long, _
ByRef Cancel As Boolean)

'Private variables:
Private m_hWnds() As Long

'API declarations:
Private Const GWL_WNDPROC = (-4)

Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" ( _
ByVal hWnd As Long, _
ByVal nIndex As Long) As Long

Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" ( _
ByVal hWnd As Long, _
ByVal nIndex As Long, _
ByVal dwNewLong As Long) As Long

Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" ( _
ByVal lpPrevWndFunc As Long, _
ByVal hWnd As Long, _
ByVal Msg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long

Private Declare Function GetProp Lib "user32" Alias "GetPropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String) As Long

Private Declare Function SetProp Lib "user32" Alias "SetPropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String, _
ByVal hData As Long) As Long

Private Declare Function RemoveProp Lib "user32" Alias "RemovePropA" ( _
ByVal hWnd As Long, _
ByVal lpString As String) As Long

Private Declare Function IsWindow Lib "user32" ( _
ByVal hWnd As Long) As Long

'
' Function SubClassHwnd
'
' This is the core function in this class.
' You can use it to both subclass and unsubclass a window.
' Once a window is subclassed the event NewMessage will
' be raised every time a message is sent to the window.
'
Public Function SubClassHwnd(ByVal hWnd As Long, _
ByVal bSubClass As Boolean) As Boolean

Dim lRet As Long

lRet = 0

'Make sure that hWnd is a valid window handler...
If IsWindow(hWnd) Then

If bSubClass Then
'We are subclassing a window...

'Make sure that the window wasn't already subclassed...
If GetProp(hWnd, SSC_OLDPROC) = 0 Then

'Now we subclass the window by changing its windowproc
lRet = SetWindowLong(hWnd, GWL_WNDPROC, _
AddressOf SmartSubClassWindowProc)

'Check if we've managed to subclass...
If lRet <> 0 Then
'Store the old windowproc and the memory
' address of this class...
SetProp hWnd, SSC_OLDPROC, lRet
SetProp hWnd, SSC_OBJADDR, ObjPtr(Me)

'Add the window to an internal list of
' subclassed windows...
pAddHwndToList hWnd
End If
End If
Else
'We are unsubclassing a window...

'Get the old windowproc...
lRet = GetProp(hWnd, SSC_OLDPROC)

If lRet <> 0 Then
'Unsubclass the window...
lRet = SetWindowLong(hWnd, GWL_WNDPROC, lRet)
End If

'Remove any extra information...
RemoveProp hWnd, SSC_OLDPROC
RemoveProp hWnd, SSC_OBJADDR

'Remove the window from the internal list...
pRemoveHwndFromList hWnd
End If
Else
'If hWnd is not a valid window,
'make sure that there isn't stored garbage...
RemoveProp hWnd, SSC_OLDPROC
RemoveProp hWnd, SSC_OBJADDR

pRemoveHwndFromList hWnd
End If

SubClassHwnd = (lRet <> 0)

End Function

'
' Function WindowProc
'
' This is the link between the windowproc and the class instance.
' Every time SmartSubClassWindowProc receives a window message,
' it will post it to the right class instance.
'
Friend Function WindowProc( _
ByVal hWnd As Long, _
ByVal uMsg As Long, _
ByVal wParam As Long, _
ByVal lParam As Long) As Long

Dim lRet As Long
Dim bCancel As Boolean

bCancel = False

WindowProc = 0

'Raise the event NewMessage...
'This will tell the owner of the class variable that a
'new message is ready to be processed.
'The owner will be able to cancel the message by setting
'the variable bCancel to True.
RaiseEvent NewMessage(hWnd, uMsg, wParam, lParam, bCancel)

'If the event hasn't been canceled by the owner
'we need to send it to the original windowproc
If Not bCancel Then

lRet = GetProp(hWnd, SSC_OLDPROC)

If lRet <> 0 Then
'Send the message to the original windowproc...
WindowProc = CallWindowProc(lRet, hWnd, uMsg, wParam, lParam)
End If

End If

End Function

'
' Every instance of the class mantains an internal
' list of subclassed windows.
'
Private Sub Class_Initialize()
ReDim m_hWnds(0) As Long
End Sub

'
' When the class terminates it makes sure that
' there are no remainig subclassed windows.
'
Private Sub Class_Terminate()
Dim i As Long
For i = UBound(m_hWnds) To 1 Step -1
If m_hWnds(i) > 0 Then
SubClassHwnd m_hWnds(i), False
End If
Next i
End Sub

'
' Private Function pFindHwndInList()
'
' This functions searches for a specific window
' in its internal list. If it doesn't find the
' window it returns 0.
'
Private Function pFindHwndInList(ByVal hWnd As Long) As Long
Dim i As Long
Dim lPos As Long
lPos = 0
For i = 1 To UBound(m_hWnds)
If m_hWnds(i) = hWnd And m_hWnds(i) > 0 Then
lPos = i
Exit For
End If
Next i
pFindHwndInList = lPos
End Function

'
' Private Sub pAddHwndToList()
'
' This procedure adds a window handle to the internal list...
'
Private Sub pAddHwndToList(ByVal hWnd As Long)
Dim lPos As Long
If pFindHwndInList(hWnd) = 0 Then
lPos = pFindNextPositionAvailableInList
If lPos <> 0 Then
m_hWnds(lPos) = hWnd
Else
lPos = UBound(m_hWnds) + 1
ReDim Preserve m_hWnds(lPos) As Long

m_hWnds(lPos) = hWnd
End If
End If
End Sub

'
' Private Sub pRemoveHwndFromList()
'
' This procedure removes a window handle from the internal list...
'
Private Sub pRemoveHwndFromList(ByVal hWnd As Long)
Dim lPos As Long
lPos = pFindHwndInList(hWnd)
If lPos <> 0 Then
If lPos = UBound(m_hWnds) Then
ReDim Preserve m_hWnds(lPos - 1) As Long
Else
m_hWnds(lPos) = -1
End If
End If
End Sub

'
' Private Function pFindNextPositionAvailableInList()
'
' This functions searches for an "empty" entry in the
' internal list of window handles. When an entry is
' removed its is marked as empty by setting its value to -1.
'
' If there are no positions available, the function returns 0.
'
Private Function pFindNextPositionAvailableInList() As Long
Dim i As Long
Dim lPos As Long
lPos = 0
For i = 1 To UBound(m_hWnds)
If m_hWnds(i) <= 0 Then
lPos = i
Exit For
End If
Next i
pFindNextPositionAvailableInList = lPos
End Function

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