Why use Protected Overide Sub OnPaint rather than the standard Paint_Event ?

Question

I notice many good programmers use this following method rather than the usual Paint_Event when painting to the form.
Protected Overrides Sub OnPaint(e As PaintEventArgs)
Dim g As Graphics = e.Graphics
g.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
g.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
MyBase.OnPaint(e)
End Sub
Can anybody share the reasons why? Thanks 
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Answer 1

OK Crazypennie, maybe you are right. I tend to rant on a bit sometimes.
Also, maybe the jumpy graphics is made worse because the animation output is not synced with the video hardware refresh rate. We can get around that slightly by using a very high fps. 
Hi Leon,
I tried modifying your code using a GraphicsFrame class that I wrote a little while back, the class utilizes the bufferedcontext/bufferedgraphics, instead of using the forms graphics directly. In theory, all objects should be rendered to the buffer before
the forms graphics object. Is this less glitchy/faster on your pc? It seemed less glitchy/faster on mine..., and previous benchmarks show that using buffered graphics in this manner improved render time.
You can read the discussion on
this thread.
Option Strict On
Option Explicit On
Option Infer Off
Public Class Form11 ' drawing Code by Paul Ishak Apr 2015 A spinning pie chart. My timing code.
Private Angle As Single = 100
Private NextIncrement As Single = 1
Private Randomizer As New Random(Now.Millisecond)
Private SliceColors As New List(Of Color)
Private SlicesOnWheel As Integer = 24
Private Velocity As Single = 0
Private WheelRadius As Integer = 300
Private WheelLocation As New Point(50, 50)
Private SW As New Stopwatch
Private SFlag As Boolean ' wheel is currently spinning
Private CntMS As Integer ' count the milliseconds
Protected Overrides Sub OnPaint(e As PaintEventArgs)
Dim gFrame As New GraphicsFrame(e.Graphics, Me.ClientRectangle.Size)
Dim g As Graphics = gFrame.Graphics
g.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
g.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
g.Clear(Me.BackColor)
Dim sliceAngle As Single = CSng(360 / SlicesOnWheel)
Dim rect As New Rectangle(WheelLocation, New Size(WheelRadius, WheelRadius))
Dim curveWidth As Integer = CInt(WheelRadius - (WheelRadius / (2.0! * 0.9)))
Dim rect2 As New Rectangle(rect.Left + curveWidth, rect.Top + curveWidth, rect.Width - curveWidth * 2, rect.Height - curveWidth * 2)
Dim inc As UInteger = UInteger.MaxValue \ 360
For I As Single = 0 To 359 Step sliceAngle
g.FillPie(New SolidBrush(SliceColors(CInt(I / sliceAngle))), rect, I + NormalizeAngle(Angle), sliceAngle)
g.DrawPie(Pens.White, rect, I + NormalizeAngle(Angle), sliceAngle)
Next
g.FillEllipse(Brushes.Black, rect2)
g.DrawEllipse(Pens.White, rect2)
g.DrawEllipse(Pens.White, rect)
MyBase.OnPaint(e)
If SFlag Then
If Me.Text = " " Then Me.Text = "" Else Me.Text = " "
End If
gFrame.Render()
gFrame.Dispose()
MyBase.OnPaint(e)
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnSpin.Click
If Not SFlag Then
Velocity = Randomizer.Next(3, 5)
NextIncrement = Velocity
SFlag = True
CntMS = 0 : SW.Reset() : SW.Start()
If Me.Text = " " Then Me.Text = "" Else Me.Text = " "
End If
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.DoubleBuffered = True
SliceColors.Add(Color.Black)
SliceColors.Add(Color.LightBlue)
SliceColors.Add(Color.SeaGreen)
SliceColors.Add(Color.Yellow)
SliceColors.Add(Color.Red)
SliceColors.Add(Color.LightBlue)
SliceColors.Add(Color.Orange)
SliceColors.Add(Color.Violet)
SliceColors.Add(Color.Yellow)
SliceColors.Add(Color.Black)
SliceColors.Add(Color.Green)
SliceColors.Add(Color.Black)
SliceColors.Add(Color.Green)
SliceColors.Add(Color.Red)
SliceColors.Add(Color.Blue)
SliceColors.Add(Color.SeaGreen)
SliceColors.Add(Color.Pink)
SliceColors.Add(Color.Black)
SliceColors.Add(Color.Purple)
SliceColors.Add(Color.SkyBlue)
SliceColors.Add(Color.Aqua)
SliceColors.Add(Color.White)
SliceColors.Add(Color.Red)
SliceColors.Add(Color.Blue)
SliceColors.Add(Color.Pink)
SliceColors.Add(Color.SeaGreen)
SliceColors.Add(Color.Orange)
ClientSize = New Size(375, 375)
Me.Show()
btnSpin.Refresh()
End Sub
Public Function NormalizeAngle(value As Single) As Single
Return value Mod 360.0!
End Function
Private Sub Form11_TextChanged(sender As Object, e As EventArgs) Handles Me.TextChanged
If Not SFlag Then Exit Sub
Angle = NormalizeAngle(Angle + NextIncrement)
NextIncrement = CSng(NextIncrement - 0.0033)
If NextIncrement <= 0.0033 Then
SFlag = False : SW.Stop() : Exit Sub
End If
Invalidate()
CntMS += 5 ' <<< set timer interval here <<<
Do Until SW.ElapsedMilliseconds > CntMS
Loop
End Sub
End Class
Public Class GraphicsFrame
Implements IDisposable
Private disposedValue As Boolean
Private BackBuffer As System.Drawing.BufferedGraphics = Nothing
Public ReadOnly Property Graphics() As System.Drawing.Graphics
Get
Return Me.BackBuffer.Graphics
End Get
End Property
Public Sub New(ByVal canvas As System.Windows.Forms.Control)
BufferedGraphicsManager.Current.MaximumBuffer = New Size(canvas.ClientRectangle.Width + 1, canvas.ClientRectangle.Height + 1)
Me.BackBuffer = BufferedGraphicsManager.Current.Allocate(canvas.CreateGraphics, New Rectangle(0, 0, canvas.ClientRectangle.Width, canvas.ClientRectangle.Height))
End Sub
Public Sub New(ByVal canvasGraphics As Graphics, maximumBuffer As Size)
BufferedGraphicsManager.Current.MaximumBuffer = New Size(maximumBuffer.Width + 1, maximumBuffer.Height + 1)
Me.BackBuffer = BufferedGraphicsManager.Current.Allocate(canvasGraphics, New Rectangle(0, 0, maximumBuffer.Width, maximumBuffer.Height))
End Sub
Public Sub New(ByVal handle As IntPtr, maximumBuffer As Size)
BufferedGraphicsManager.Current.MaximumBuffer = New Size(maximumBuffer.Width + 1, maximumBuffer.Height + 1)
Me.BackBuffer = BufferedGraphicsManager.Current.Allocate(Graphics.FromHwnd(handle), New Rectangle(0, 0, maximumBuffer.Width, maximumBuffer.Height))
End Sub
Public Sub New(ByVal canvas As Image)
BufferedGraphicsManager.Current.MaximumBuffer = New Size(canvas.Width + 1, canvas.Height + 1)
Me.BackBuffer = BufferedGraphicsManager.Current.Allocate(Graphics.FromImage(canvas), New Rectangle(0, 0, canvas.Width, canvas.Height))
End Sub
Public Sub New(ByVal canvas As Bitmap)
BufferedGraphicsManager.Current.MaximumBuffer = New Size(canvas.Size.Width + 1, canvas.Size.Height + 1)
Me.BackBuffer = BufferedGraphicsManager.Current.Allocate(Graphics.FromImage(canvas), New Rectangle(0, 0, canvas.Width, canvas.Height))
End Sub
Public Sub Render()
If Not BackBuffer Is Nothing Then BackBuffer.Render()
End Sub
Protected Overridable Sub Dispose(disposing As Boolean)
If Not Me.disposedValue Then
If disposing Then
Me.BackBuffer = Nothing
GC.Collect()
End If
End If
Me.disposedValue = True
End Sub
Public Sub Dispose() Implements IDisposable.Dispose
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
End Class
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