Public Class Form1
    Private mShapeContainer As clsShapeContainer
    Private isMouseDown As Boolean = False

    Private gFx As Graphics ' backbuffer
    Private backBuffer As Bitmap
    Private panelGraphics As Graphics


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ' Genera array di figure
        Dim x As Integer = 0, y As Integer = 0
        For i As Integer = 0 To 20
            mShapeContainer.AddEllipse(x, y)
            x += 30

            If x >= (Panel1.Width - 30) Then
                x = 0
                y += 30
            End If
            If y >= (Panel1.Height - 30) Then
                'y = 0
                x = 0
            End If
        Next
        Panel1.Invalidate()
    End Sub



    Private Sub Panel1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Panel1.Paint
        Debug.WriteLine("Panel1.Paint")
        If (panelGraphics Is Nothing) Then
            panelGraphics = Panel1.CreateGraphics
            panelGraphics.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias
        End If

       
        'Clear Back Buffer
        gFx.Clear(Color.White)
        'Draw in back buffer 
        Draw(gFx)
        'Flip backBuffer to screen
        panelGraphics.DrawImage(backBuffer, 0, 0)
    End Sub

    Public Sub Draw(ByRef g As Graphics)

        For Each shape As clsShape In mShapeContainer.Shapes
            shape.Draw(g)
        Next

    End Sub

    Private Sub Panel1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseDown
        For I As Integer = mShapeContainer.Shapes.Count - 1 To 0 Step -1

            With mShapeContainer
                If .Shapes(I).Rectangle.Contains(e.Location) Then
                    .SelectedShape = .Shapes(I)
                    isMouseDown = True
                    Exit For
                End If
            End With
        Next
    End Sub



    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        mShapeContainer = New clsShapeContainer(Me.Panel1)

        backBuffer = New Bitmap(Me.Panel1.Width, Me.Panel1.Height)
        gFx = Graphics.FromImage(backbuffer)
        gFx.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        mShapeContainer.ZoomIn()
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        mShapeContainer.ZoomOut()
    End Sub

    Private Sub Panel1_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseUp
        isMouseDown = False
    End Sub

    Private Sub Panel1_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel1.MouseMove
        If isMouseDown Then
            With mShapeContainer
                If .SelectedShape IsNot Nothing Then
                    .SelectedShape.Move(e.Location)                   
                End If
            End With
        End If
    End Sub