Imports System.Runtime.InteropServices
Imports AcadApp = Autodesk.AutoCAD.ApplicationServices.Application
Imports AcAp = Autodesk.AutoCAD.ApplicationServices
Imports AcCm = Autodesk.AutoCAD.Colors
Imports AcDb = Autodesk.AutoCAD.DatabaseServices
Imports AcEd = Autodesk.AutoCAD.EditorInput
Imports AcGe = Autodesk.AutoCAD.Geometry
Imports AcGi = Autodesk.AutoCAD.GraphicsInterface
Imports AcLy = Autodesk.AutoCAD.LayerManager
Imports AcPl = Autodesk.AutoCAD.PlottingServices
Imports AcPu = Autodesk.AutoCAD.Publishing
Imports AcRx = Autodesk.AutoCAD.Runtime
Imports AcWi = Autodesk.AutoCAD.Windows

Public Class Zoom
    <DllImport("acad.exe", CallingConvention:=CallingConvention.Cdecl, EntryPoint:="?acedVportTableRecords2Vports@@YA?AW4ErrorStatus@Acad@@XZ")> _
    Private Shared Function acedVportTableRecords2Vports() As Boolean
    End Function

    <DllImport("acad.exe", CallingConvention:=CallingConvention.Cdecl, EntryPoint:="?acedVports2VportTableRecords@@YA?AW4ErrorStatus@Acad@@XZ")> _
    Private Shared Function acedVports2VportTableRecords() As Boolean
    End Function

    <DllImport("acad.exe", CallingConvention:=CallingConvention.Cdecl, EntryPoint:="?acedSetCurrentView@@YA?AW4ErrorStatus@Acad@@PAVAcDbViewTableRecord@@PAVAcDbViewport@@@Z")> _
    Public Shared Function acedSetCurrentView(ByVal viewTableRec As IntPtr, ByVal viewport As IntPtr) As IntPtr
    End Function

    <AcRx.CommandMethod("ZC")> _
    Public Sub Center()

        'The following line would need to be called if running function 
        'from inside of application context
        'Dim DL As AcAp.DocumentLock = AcadApp.DocumentManager.MdiActiveDocument.LockDocument(AcAp.DocumentLockMode.Write, "CrosshairAlignmentMagLevel", "CrosshairAlignmentMagLevel", True)

        Dim DB As AcDb.Database = AcadApp.DocumentManager.MdiActiveDocument.Database
        Dim myT As AcDb.Transaction = DB.TransactionManager.StartTransaction
        Try
            Dim Ed As AcEd.Editor = AcadApp.DocumentManager.MdiActiveDocument.Editor
            Dim PPO As New AcEd.PromptPointOptions("Select a point: ")
            Dim PPR As AcEd.PromptPointResult = Nothing
            PPR = Ed.GetPoint(PPO)
            If PPR.Status <> Autodesk.AutoCAD.EditorInput.PromptStatus.OK Then
                myT.Dispose()
                Return
            End If
            Dim NewCenterPoint3D As AcGe.Point3d = PPR.Value

            'Must convert the 3D coordinate to 2D
            Dim NewCenterPoint2D As New AcGe.Point2d(NewCenterPoint3D.X, NewCenterPoint3D.Y)

            If DB.TileMode = True Then
                'In Modelspace
                'You must first force the Vport information to the record objects or you will
                'be getting stale information.
                acedVports2VportTableRecords()

                Dim VPTR As AcDb.ViewportTableRecord = Nothing
                Dim VPT As AcDb.ViewportTable = myT.GetObject(DB.ViewportTableId, AcDb.OpenMode.ForRead)
                For Each OID As AcDb.ObjectId In VPT
                    If OID.IsErased = False Then
                        'The first unerased viewport should be the current one!
                        VPTR = myT.GetObject(OID, Autodesk.AutoCAD.DatabaseServices.OpenMode.ForRead)
                        Exit For
                    End If
                Next
                VPT.Dispose()

                If VPTR Is Nothing Then
                    myT.Dispose()
                    Return
                End If

                Dim V As New AcDb.ViewTableRecord
                V.IsPaperspaceView = False
                V.Height = VPTR.Height
                V.Width = VPTR.Width
                V.CenterPoint = NewCenterPoint2D
                acedSetCurrentView(V.UnmanagedObject, Nothing)
                VPTR.Dispose()
                V.Dispose()
            Else
                'In paperspace or a floating modelspace viewport
                '
                'Unlike modelspace PAPERSPACE is an AcDbViewport
                'not an AcDbViewportTableRecord
                Dim PSVport As AcDb.Viewport
                PSVport = myT.GetObject(Ed.CurrentViewportObjectId, Autodesk.AutoCAD.DatabaseServices.OpenMode.ForWrite)
                PSVport.ViewCenter = NewCenterPoint2D
            End If

            myT.Commit()
        Catch ex As Exception
            AcadApp.ShowAlertDialog(ex.ToString)
        Finally
            myT.Dispose()
        End Try

        'Dispose of the lock if it was required
        'DL.Dispose()

        AcadApp.UpdateScreen()
    End Sub

    Public Sub Window()

    End Sub

    Public Sub Extents()

    End Sub

    Public Sub Entity()

    End Sub
End Class