'In the form's code module
Option Explicit
Private Sub Form_Load()
'Save handle to the form.
gHW = Me.hwnd
'Begin subclassing.
Hook
End Sub
Private Sub Form_Unload(Cancel As Integer)
'Stop subclassing.
Unhook
End Sub
'In a module
Option Explicit
Private Const GWL_WNDPROC = -4
Private Const WM_GETMINMAXINFO = &H24
Private Type POINTAPI
x As Long
y As Long
End Type
Private Type MINMAXINFO
ptReserved As POINTAPI
ptMaxSize As POINTAPI
ptMaxPosition As POINTAPI
ptMinTrackSize As POINTAPI
ptMaxTrackSize As POINTAPI
End Type
Global lpPrevWndProc As Long
Global gHW As Long
Private Declare Function DefWindowProc Lib "user32" Alias _
"DefWindowProcA" (ByVal hwnd As Long, ByVal wMsg As Long, _
ByVal wParam As Long, ByVal lParam 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 SetWindowLong Lib "user32" Alias _
"SetWindowLongA" (ByVal hwnd As Long, _
ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Sub CopyMemoryToMinMaxInfo Lib "KERNEL32" Alias _
"RtlMoveMemory" (hpvDest As MINMAXINFO, ByVal hpvSource As Long, _
ByVal cbCopy As Long)
Private Declare Sub CopyMemoryFromMinMaxInfo Lib "KERNEL32" Alias _
"RtlMoveMemory" (ByVal hpvDest As Long, hpvSource As MINMAXINFO, _
ByVal cbCopy As Long)
Public Sub Hook()
'Start subclassing.
lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _
AddressOf WindowProc)
End Sub
Public Sub Unhook()
Dim temp As Long
'Cease subclassing.
temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)
End Sub
Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
Dim MinMax As MINMAXINFO
'Check for request for min/max window sizes.
If uMsg = WM_GETMINMAXINFO Then
'necesary for the caption of an MDI child (when maximized)
'(Thanks to Marvin Chinchilla for this information)
WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg, _
wParam, lParam)
'Retrieve default MinMax settings
CopyMemoryToMinMaxInfo MinMax, lParam, Len(MinMax)
'Specify new minimum size for window.
MinMax.ptMinTrackSize.x = 200
MinMax.ptMinTrackSize.y = 200
'Specify new maximum size for window.
MinMax.ptMaxTrackSize.x = 250
MinMax.ptMaxTrackSize.y = 250
'Copy local structure back.
CopyMemoryFromMinMaxInfo lParam, MinMax, Len(MinMax)
WindowProc = DefWindowProc(hw, uMsg, wParam, lParam)
Else
WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg, _
wParam, lParam)
End If
End Function
