限制Form Resize的最大值

Option Explicit

'以下程式在module1.bas
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex As Long) As Long
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

Declare Sub CopyMemory Lib "KERNEL32" Alias "RtlMoveMemory" ( _
lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)
Public Const GWL_WNDPROC = (-4)
Public Const WM_GETMINMAXINFO = &H24
Type POINTAPI
x As Long
y As Long
End Type
Type MINMAXINFO
ptReserved As POINTAPI
ptMaxSize As POINTAPI
ptMaxPosition As POINTAPI
ptMinTrackSize As POINTAPI
ptMaxTrackSize As POINTAPI
End Type

Public preWinProc As Long

Public Function wndproc(ByVal hwnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
Dim lwd As Long, hwd As Long
If Msg = WM_GETMINMAXINFO Then
Dim maxmin As MINMAXINFO
CopyMemory maxmin, ByVal lParam, Len(maxmin)
maxmin.ptMaxTrackSize.x = 500 '设定最大Resize的宽度
maxmin.ptMaxTrackSize.y = 400 '设定最大Resize的高度
'maxmin.ptMinTrackSize.x = 300 '设定最大小Resize的宽度
'maxmin.ptMinTrackSize.y = 300 '设定最大小Resize的高度
CopyMemory ByVal lParam, maxmin, Len(maxmin)
End If
'将之送往原来的Window Procedure
wndproc = CallWindowProc(preWinProc, hwnd, Msg, wParam, lParam)
End Function

'以下在Form
Sub Form_Load()
Dim ret As Long
'记录原本的Window Procedure的位址
preWinProc = GetWindowLong(Me.hwnd, GWL_WNDPROC)
ret = SetWindowLong(Me.hwnd, GWL_WNDPROC, AddressOf wndproc)
End Sub

Private Sub Form_Unload(Cancel As Integer)
Dim ret As Long
'取消Message的截取，而使之又只送往原来的Window Procedure
ret = SetWindowLong(Me.hwnd, GWL_WNDPROC, preWinProc)
End Sub

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