Imports System.Drawing.Drawing2D
Imports System.Drawing.Text

Public Class CustomVScrollBar
    Inherits Control

    Dim Thumb As Rectangle
    Dim _ColorScheme As ColorScheme

    Dim _thumby As Integer
    Dim _vis As Double = 1
    Dim _thumbsize As Integer = 20
    Dim _val As Double

    Dim Pressed As Boolean = False

    Public Event Scroll()

    Property VisibleRatio As Double
        Get
            Return _vis
        End Get
        Set(ByVal value As Double)
            _vis = value
            _thumbsize = CInt(Height * _vis)
            Invalidate()
        End Set
    End Property

    Property Value As Double
        Get
            Return _val
        End Get
        Set(ByVal value As Double)
            _val = value
            Invalidate()
            RaiseEvent Scroll()
        End Set
    End Property

    Public Property ColorScheme As ColorScheme
        Get
            Return _ColorScheme
        End Get
        Set(value As ColorScheme)
            _ColorScheme = value
            Invalidate()
        End Set
    End Property

    Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
        If e.Button = MouseButtons.Left Then
            If Thumb.Contains(e.Location) Then
                Pressed = True
            Else
                If e.Y < Thumb.Y Then _thumby = CInt(_val - 10) Else _thumby = CInt(_val + 10)
                _val = Math.Min(Math.Max(_thumby, 0), 100)
                Invalidate()
                RaiseEvent Scroll()
            End If
        End If
    End Sub
    Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
        Pressed = False
    End Sub
    Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)
        If Pressed Then
            Dim ThumbPosition As Integer = CInt(e.Y - (_thumbsize / 2))
            Dim ThumbBounds As Integer = Height - _thumbsize
            _thumby = CInt((ThumbPosition / ThumbBounds) * 100)
            _val = Math.Min(Math.Max(_thumby, 0), 100)
            Invalidate()
            RaiseEvent Scroll()
        End If
    End Sub

    Sub New()
        SetStyle(ControlStyles.OptimizedDoubleBuffer Or ControlStyles.AllPaintingInWmPaint Or ControlStyles.ResizeRedraw Or ControlStyles.UserPaint Or ControlStyles.Selectable Or ControlStyles.SupportsTransparentBackColor, True)
        DoubleBuffered = True
    End Sub

    Protected Overrides Sub OnPaint(e As System.Windows.Forms.PaintEventArgs)
        Thumb = New Rectangle(0, 0, Width, _thumbsize)
        Thumb.Y = CInt(((_val) / 100) * (Height - _thumbsize))

        Dim _BaseColor As Color
        Dim _ThumbColor As Color

        If _ColorScheme = ColorScheme.Dark Then
            _BaseColor = Color.FromArgb(64, 64, 64)
            _ThumbColor = Color.FromArgb(70, 70, 70)
        Else
            _BaseColor = Color.White
            _ThumbColor = Color.WhiteSmoke
        End If

        If Not VisibleRatio >= 1 Then
            Dim g = e.Graphics
            With g
                .TextRenderingHint = TextRenderingHint.ClearTypeGridFit
                .SmoothingMode = SmoothingMode.HighQuality
                .PixelOffsetMode = PixelOffsetMode.HighQuality
                .Clear(_BaseColor)
                .FillRectangle(New SolidBrush(_ThumbColor), Thumb)
                .DrawLine(New Pen(Color.SteelBlue, 2), New Point(CInt(Thumb.Width / 2), Thumb.Y + 4), New Point(CInt(Thumb.Width / 2), Thumb.Bottom - 4))
                .InterpolationMode = InterpolationMode.HighQualityBicubic
            End With
        End If
    End Sub
End Class