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 '************************************************************* 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 'Moves and resizes a window in the coordinate system of its parent window. Private Declare Function apiGetWindowRect Lib "user32" Alias "GetWindowRect" (ByVal hWnd As Long, lpRect As RECT) As Long 'After calling, the lpRect parameter contains the RECT structure describing the sides of the window in screen coordinates. Private Declare Function apiScreenToClient Lib "user32" Alias "ScreenToClient" (ByVal hWnd As Long, lpPoint As POINTAPI) As Long 'Converts lpPoint from screen coordinates to the coordinate system of the specified client window. Private Declare Function apiGetParent Lib "user32" Alias "GetParent" (ByVal hWnd As Long) As Long 'Returns the handle of the parent window of the specified window. '************************************************************* ' 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