clFormWindow.bas

VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
END
Attribute VB_Name = "clFormWindow"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
Option Compare Database
Option Explicit


'*************************************************************
' Class module: clFormWindow                                 *
'*************************************************************
' Moves and resizes a window in the coordinate system        *
' of its parent window.                                      *
' N.B.: This class was developed for use on Access forms     *
'       and has not been tested for use with other window    *
'       types.                                               *
'*************************************************************



'*************************************************************
' Type declarations
'*************************************************************

Private Type RECT       'RECT structure used for API calls.
    Left As Long
    Top As Long
    Right As Long
    Bottom As Long
End Type


Private Type POINTAPI   'POINTAPI structure used for API calls.
    X As Long
    Y As Long
End Type



'*************************************************************
' Member variables
'*************************************************************

Private m_hWnd As Long          'Handle of the window.
Private m_rctWindow As RECT     'Rectangle describing the sides of the last polled location of the window.



'*************************************************************
' Private error constants for use with RaiseError procedure
'*************************************************************

Private Const m_ERR_INVALIDHWND = 1
Private Const m_ERR_NOPARENTWINDOW = 2



'*************************************************************
' API function declarations
'*************************************************************

#If VBA7 Then
    Private Declare PtrSafe Function apiIsWindow Lib "user32" Alias "IsWindow" (ByVal hWnd As LongPtr) As Long
    Private Declare PtrSafe Function apiMoveWindow Lib "user32" Alias "MoveWindow" (ByVal hWnd As LongPtr, ByVal X As Long, ByVal Y As Long, _
        ByVal nWidth As Long, ByVal nHeight As Long, ByVal bRepaint As Long) As Long
    Private Declare PtrSafe Function apiGetWindowRect Lib "user32" Alias "GetWindowRect" (ByVal hWnd As LongPtr, lpRect As RECT) As Long
    Private Declare PtrSafe Function apiScreenToClient Lib "user32" Alias "ScreenToClient" (ByVal hWnd As LongPtr, lpPoint As POINTAPI) As Long
    Private Declare PtrSafe Function apiGetParent Lib "user32" Alias "GetParent" (ByVal hWnd As LongPtr) As Long
#Else
    Private Declare Function apiIsWindow Lib "user32" Alias "IsWindow" (ByVal hWnd As Long) As Long
    Private Declare Function apiMoveWindow Lib "user32" Alias "MoveWindow" (ByVal hWnd As Long, ByVal X As Long, ByVal Y As Long, _
        ByVal nWidth As Long, ByVal nHeight As Long, ByVal bRepaint As Long) As Long
    Private Declare Function apiGetWindowRect Lib "user32" Alias "GetWindowRect" (ByVal hWnd As Long, lpRect As RECT) As Long
    Private Declare Function apiScreenToClient Lib "user32" Alias "ScreenToClient" (ByVal hWnd As Long, lpPoint As POINTAPI) As Long
    Private Declare Function apiGetParent Lib "user32" Alias "GetParent" (ByVal hWnd As Long) As Long
#End If




'*************************************************************
' Private procedures
'*************************************************************

Private Sub RaiseError(ByVal lngErrNumber As Long, ByVal strErrDesc As String)
'Raises a user-defined error to the calling procedure.

    Err.Raise vbObjectError + lngErrNumber, "clFormWindow", strErrDesc
    
End Sub


Private Sub UpdateWindowRect()
'Places the current window rectangle position (in pixels, in coordinate system of parent window) in m_rctWindow.

    Dim ptCorner As POINTAPI
    
    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        apiGetWindowRect m_hWnd, m_rctWindow   'm_rctWindow now holds window coordinates in screen coordinates.
        
        If Not Me.Parent Is Nothing Then
            'If there is a parent window, convert top, left of window from screen coordinates to parent window coordinates.
            With ptCorner
                .X = m_rctWindow.Left
                .Y = m_rctWindow.Top
            End With
        
            apiScreenToClient Me.Parent.hWnd, ptCorner
        
            With m_rctWindow
                .Left = ptCorner.X
                .Top = ptCorner.Y
            End With
    
            'If there is a parent window, convert bottom, right of window from screen coordinates to parent window coordinates.
            With ptCorner
                .X = m_rctWindow.Right
                .Y = m_rctWindow.Bottom
            End With
        
            apiScreenToClient Me.Parent.hWnd, ptCorner
        
            With m_rctWindow
                .Right = ptCorner.X
                .Bottom = ptCorner.Y
            End With
        End If
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If
    
End Sub




'*************************************************************
' Public read-write properties
'*************************************************************

Public Property Get hWnd() As Long
'Returns the value the user has specified for the window's handle.

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        hWnd = m_hWnd
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If
    
End Property


Public Property Let hWnd(ByVal lngNewValue As Long)
'Sets the window to use by specifying its handle.
'Only accepts valid window handles.

    If lngNewValue = 0 Or apiIsWindow(lngNewValue) Then
        m_hWnd = lngNewValue
    Else
        RaiseError m_ERR_INVALIDHWND, "The value passed to the hWnd property is not a valid window handle."
    End If
    
End Property

'----------------------------------------------------

Public Property Get Left() As Long
'Returns the current position (in pixels) of the left edge of the window in the coordinate system of its parent window.

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        Left = m_rctWindow.Left
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If
    
End Property


Public Property Let Left(ByVal lngNewValue As Long)
'Moves the window such that its left edge falls at the position indicated
'(measured in pixels, in the coordinate system of its parent window).

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        With m_rctWindow
            apiMoveWindow m_hWnd, lngNewValue, .Top, .Right - .Left, .Bottom - .Top, True
        End With
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If
    
End Property

'----------------------------------------------------

Public Property Get Top() As Long
'Returns the current position (in pixels) of the top edge of the window in the coordinate system of its parent window.

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        Top = m_rctWindow.Top
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

End Property


Public Property Let Top(ByVal lngNewValue As Long)
'Moves the window such that its top edge falls at the position indicated
'(measured in pixels, in the coordinate system of its parent window).

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        With m_rctWindow
            apiMoveWindow m_hWnd, .Left, lngNewValue, .Right - .Left, .Bottom - .Top, True
        End With
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

End Property

'----------------------------------------------------

Public Property Get Width() As Long
'Returns the current width (in pixels) of the window.
    
    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        With m_rctWindow
            Width = .Right - .Left
        End With
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

End Property


Public Property Let Width(ByVal lngNewValue As Long)
'Changes the width of the window to the value provided (in pixels).

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        With m_rctWindow
            apiMoveWindow m_hWnd, .Left, .Top, lngNewValue, .Bottom - .Top, True
        End With
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

End Property

'----------------------------------------------------

Public Property Get Height() As Long
'Returns the current height (in pixels) of the window.
    
    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        With m_rctWindow
            Height = .Bottom - .Top
        End With
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

End Property


Public Property Let Height(ByVal lngNewValue As Long)
'Changes the height of the window to the value provided (in pixels).

    If m_hWnd = 0 Or apiIsWindow(m_hWnd) Then
        UpdateWindowRect
        With m_rctWindow
            apiMoveWindow m_hWnd, .Left, .Top, .Right - .Left, lngNewValue, True
        End With
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

End Property



'*************************************************************
' Public read-only properties
'*************************************************************

Public Property Get Parent() As clFormWindow
'Returns the parent window as a clFormWindow object.
'For forms, this should be the Access MDI window.

    Dim fwParent As New clFormWindow
    Dim lngHWnd As Long
    
    If m_hWnd = 0 Then
        Set Parent = Nothing
    ElseIf apiIsWindow(m_hWnd) Then
        lngHWnd = apiGetParent(m_hWnd)
        fwParent.hWnd = lngHWnd
        Set Parent = fwParent
    Else
        RaiseError m_ERR_INVALIDHWND, "The window handle " & m_hWnd & " is no longer valid."
    End If

    Set fwParent = Nothing
    
End Property