Simple Runtime Control Sizing and Dragging Class

Public Class PickBox
    '/ summary
    '/ This class implements sizing and moving functions for
    '/	runtime editing of graphic controls
    '/ summary
    '////////////////////////////////////////////////////////////////
    ' PRIVATE CONSTANTS AND VARIABLES
    '////////////////////////////////////////////////////////////////

    Private Const BOX_SIZE As Integer = 8
    Private BOX_COLOR As Color = Color.White
    Private m_container As ContainerControl
    Private m_control As Control
    Private lbl(8) As Label
    Private startl As Integer
    Private startt As Integer
    Private startw As Integer
    Private starth As Integer
    Private startx As Integer
    Private starty As Integer
    Private dragging As Boolean
    Private arrArrow() As Cursor = New Cursor() {Cursors.SizeNWSE, Cursors.SizeNS, _
Cursors.SizeNESW, Cursors.SizeWE, Cursors.SizeNWSE, Cursors.SizeNS, _
Cursors.SizeNESW, Cursors.SizeWE}

    Private oldCursor As Cursor

    Private Const MIN_SIZE As Integer = 20

    '
    ' Constructor creates 8 sizing handles & wires mouse events
    ' to each that implement sizing functions
    '
    Public Sub New()
        Dim i As Integer
        For i = 0 To 8 - 1 Step i + 1
            lbl(i) = New Label
            lbl(i).TabIndex = i
            lbl(i).FlatStyle = 0
            lbl(i).BorderStyle = BorderStyle.FixedSingle
            lbl(i).BackColor = BOX_COLOR
            lbl(i).Cursor = arrArrow(i)
            lbl(i).Text = ""
            lbl(i).BringToFront()
            AddHandler lbl(i).MouseDown, AddressOf Me.lbl_MouseDown
            AddHandler lbl(i).MouseMove, AddressOf Me.lbl_MouseMove
            AddHandler lbl(i).MouseUp, AddressOf Me.lbl_MouseUp
        Next
    End Sub

    '////////////////////////////////////////////////////////////////
    ' PUBLIC METHODS
    '////////////////////////////////////////////////////////////////

    '
    ' Wires a Click event handler to the passed Control
    ' that attaches a pick box to the control when it is clicked
    '
    Public Sub WireControl(ByVal ctl As Control)
        AddHandler ctl.Click, AddressOf SelectControl
    End Sub


    '///////////////////////////////////////////////////////////////
    ' PRIVATE METHODS
    '///////////////////////////////////////////////////////////////

    '
    ' Attaches a pick box to the sender Control
    '
    Private Sub SelectControl(ByVal sender As Object, ByVal e As EventArgs)

        If TypeOf m_control Is Control Then
            m_control.Cursor = oldCursor

            'Remove event any pre-existing event handlers appended by this class
            RemoveHandler m_control.MouseDown, AddressOf Me.ctl_MouseDown
            RemoveHandler m_control.MouseMove, AddressOf Me.ctl_MouseMove
            RemoveHandler m_control.MouseUp, AddressOf Me.ctl_MouseUp

            m_control = Nothing
        End If

        m_control = CType(sender, Control)
        'Add event handlers for moving the selected control around
        AddHandler m_control.MouseDown, AddressOf Me.ctl_MouseDown
        AddHandler m_control.MouseMove, AddressOf Me.ctl_MouseMove
        AddHandler m_control.MouseUp, AddressOf Me.ctl_MouseUp
        AddHandler m_control.Parent.Click, AddressOf Me.Parent_Click

        'Add sizing handles to Control's container (Form or PictureBox)
        Dim i As Integer
        For i = 0 To 8 - 1 Step i + 1
            m_control.Parent.Controls.Add(lbl(i))
            lbl(i).BringToFront()
        Next

        'Position sizing handles around Control
        MoveHandles()

        'Display sizing handles
        ShowHandles()

        oldCursor = m_control.Cursor
        m_control.Cursor = Cursors.SizeAll

    End Sub

    Public Sub Remove()
        HideHandles()
        m_control.Cursor = oldCursor
    End Sub

    Private Sub ShowHandles()
        If Not m_control Is Nothing Then
            Dim i As Integer
            For i = 0 To 8 - 1 Step i + 1
                lbl(i).Visible = True
            Next
        End If
    End Sub

    Private Sub HideHandles()
        Dim i As Integer
        For i = 0 To 8 - 1 Step i + 1
            lbl(i).Visible = False
        Next
    End Sub

    Private Sub MoveHandles()
        Dim sX As Integer = m_control.Left - BOX_SIZE
        Dim sY As Integer = m_control.Top - BOX_SIZE
        Dim sW As Integer = m_control.Width + BOX_SIZE
        Dim sH As Integer = m_control.Height + BOX_SIZE
        Dim hB As Integer = BOX_SIZE / 2
        Dim arrPosX = New Integer() {sX + hB, sX + sW / 2, sX + sW - hB, _
            sX + sW - hB, sX + sW - hB, sX + sW / 2, sX + hB, sX + hB}

        Dim arrPosY = New Integer() {sY + hB, sY + hB, sY + hB, sY + sH / 2, _
            sY + sH - hB, sY + sH - hB, sY + sH - hB, sY + sH / 2}

        Dim i As Integer
        For i = 0 To 8 - 1 Step i + 1
            lbl(i).SetBounds(arrPosX(i), arrPosY(i), BOX_SIZE, BOX_SIZE)
        Next
    End Sub

    '///////////////////////////////////////////////////////////////
    ' MOUSE EVENTS THAT IMPLEMENT SIZING OF THE PICKED CONTROL
    '///////////////////////////////////////////////////////////////

    '
    ' Store control position and size when mouse button pushed over
    ' any sizing handle
    '
    Private Sub lbl_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs)
        dragging = True
        startl = m_control.Left
        startt = m_control.Top
        startw = m_control.Width
        starth = m_control.Height
        HideHandles()
    End Sub

    '
    ' Size the picked control in accordance with sizing handle being dragged
    '	0   1   2
    '   7       3
    '   6   5   4
    '
    Private Sub lbl_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs)
        Dim l As Integer = m_control.Left
        Dim w As Integer = m_control.Width
        Dim t As Integer = m_control.Top
        Dim h As Integer = m_control.Height
        If dragging Then
            Select Case (CType(sender, Label)).TabIndex
                Case 0
                    ' Dragging top-left sizing box
                    If startl + e.X < startl + startw - MIN_SIZE Then
                        l = startl + e.X
                    Else
                        l = startl + startw - MIN_SIZE
                    End If
                    If startt + e.Y < startt + starth - MIN_SIZE Then
                        t = startt + e.Y
                    Else
                        t = startt + starth - MIN_SIZE
                    End If

                    w = startl + startw - m_control.Left
                    h = startt + starth - m_control.Top
                    Exit Select
                Case 1
                    ' Dragging top-center sizing box
                    If startt + e.Y < startt + starth - MIN_SIZE Then
                        t = startt + e.Y
                    Else
                        t = startt + starth - MIN_SIZE
                    End If
                    h = startt + starth - m_control.Top
                    Exit Select
                Case 2
                    ' Dragging top-right sizing box
                    If startw + e.X > MIN_SIZE Then
                        w = startw + e.X
                    Else
                        w = MIN_SIZE
                    End If
                    If startt + e.Y < startt + starth - MIN_SIZE Then
                        t = startt + e.Y
                    Else
                        t = startt + starth - MIN_SIZE
                    End If
                    h = startt + starth - m_control.Top
                    Exit Select
                Case 3
                    ' Dragging right-middle sizing box
                    If startw + e.X > MIN_SIZE Then
                        w = startw + e.X
                    Else
                        w = MIN_SIZE
                    End If
                    Exit Select
                Case 4
                    ' Dragging right-bottom sizing box
                    If startw + e.X > MIN_SIZE Then
                        w = startw + e.X
                    Else
                        w = MIN_SIZE
                    End If
                    If starth + e.Y > MIN_SIZE Then
                        h = starth + e.Y
                    Else
                        h = MIN_SIZE
                    End If
                    Exit Select
                Case 5
                    ' Dragging center-bottom sizing box
                    If starth + e.Y > MIN_SIZE Then
                        h = starth + e.Y
                    Else
                        h = MIN_SIZE
                    End If
                    Exit Select
                Case 6
                    ' Dragging left-bottom sizing box
                    If startl + e.X < startl + startw - MIN_SIZE Then
                        l = startl + e.X
                    Else
                        l = startl + startw - MIN_SIZE
                    End If
                    w = startl + startw - m_control.Left
                    If starth + e.Y > MIN_SIZE Then
                        h = starth + e.Y
                    Else
                        h = MIN_SIZE
                    End If
                    Exit Select
                Case 7
                    ' Dragging left-middle sizing box
                    If startl + e.X < startl + startw - MIN_SIZE Then
                        l = startl + e.X
                    Else
                        l = startl + startw - MIN_SIZE
                    End If
                    w = startl + startw - m_control.Left
                    Exit Select
            End Select
            If l < 0 Then
                l = 0
            Else
                l = l
            End If
            If t < 0 Then
                t = 0
            Else
                t = t
            End If
            m_control.SetBounds(l, t, w, h)
        End If
    End Sub

    '
    ' Display sizing handles around picked control once sizing has completed
    '
    Private Sub lbl_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs)
        dragging = False
        MoveHandles()
        ShowHandles()
    End Sub

    '///////////////////////////////////////////////////////////////
    ' MOUSE EVENTS THAT MOVE THE PICKED CONTROL AROUND THE FORM
    '///////////////////////////////////////////////////////////////

    '
    ' Get mouse pointer starting position on mouse down and hide sizing handles
    '
    Private Sub ctl_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs)
        dragging = True
        startx = e.X
        starty = e.Y
        HideHandles()
    End Sub

    '
    ' Reposition the dragged control
    '
    Private Sub ctl_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs)
        If dragging Then
            Dim l As Integer = m_control.Left + e.X - startx
            Dim t As Integer = m_control.Top + e.Y - starty
            Dim w As Integer = m_control.Width
            Dim h As Integer = m_control.Height
            If l < 0 Then
                l = 0
            Else
                If l + w > m_control.Parent.ClientRectangle.Width Then
                    l = m_control.Parent.ClientRectangle.Width - w
                Else
                    l = l
                End If
            End If
            If t < 0 Then
                t = 0
            Else
                If t + h > m_control.Parent.ClientRectangle.Height Then
                    t = m_control.Parent.ClientRectangle.Height - h
                Else
                    t = t
                End If
            End If

            m_control.Left = l
            m_control.Top = t
        End If
    End Sub

    '
    ' Display sizing handles around picked control once dragging has completed
    '
    Private Sub ctl_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs)
        dragging = False
        MoveHandles()
        ShowHandles()
    End Sub

    Private Sub Parent_Click(ByVal sender As Object, ByVal e As EventArgs)
        Remove()
    End Sub
End Class