[RESOLVED] Drawing gdi+ flickering??? Heeeelp!

[Begi]

I have a Class which inherits a UserControl. The aim is to graphically display the sound input/output. The Property "Value" of Animation Class, receives the current value of the sound in realtime between 0 and 100, which i update from an outside Class via a Timer(50MSec.)

I managed it all to work but i am facing an annoying problem, the animation flickers. I raised the Thread.Priority into Highest, no effect, so i dont believe a separate Thread would do better. I researched and know now basically where the problem lies, but still cant figure out how to handle it. I have tried as in the beginning the ME.CreateGraphics Method, it flickered, then overrided OnPaint Method and painted with e.Graphics. The result was a blank control! Thanks for any help!

Here is a small demo of the code, an example

Public Class Form1
    Private [DISPLAY] As Form 'A SEPARATE FORM THAT CONTAINS THE USERCONTROL "ANIMATION" & DISPLAYS IT
    Private _Animation As Animation
    Private Shadows Sub [load]() Handles MyBase.Load
        DISPLAY = New Form
        _Animation = New Animation
        DISPLAY.Controls.Add(_Animation)
        _Animation.Dock = DockStyle.Fill
        DISPLAY.Show()
        Dim tmr As New Timer(New System.ComponentModel.Container)
        tmr.Interval = 50
        AddHandler tmr.Tick, AddressOf Looper
        tmr.Start()
    End Sub
    Private Sub Looper()
        _Animation.Value = Now.Second 'AN EXAMPLE
    End Sub
End Class

Public Class Animation
    Inherits UserControl
    Private _Value As UInt32
    'EVERYTIME VALUE IS CHANGED IT WILL REPAINT THE CONTROL
    Public Property Value As UInt32
        Get
            Return _Value
        End Get
        Set(ByVal value As UInt32)
            _Value = value
            [Refresh]()
        End Set
    End Property
    Sub New()
        ' InitilizeComponent()
        Countleds()
    End Sub
    Private LEDs As Integer
    'COUNT THE AMOUNT OF LEDS POSSIBLE TO FIT IN CONTROL
    Private Sub Countleds() Handles Me.SizeChanged

        dictOfLeds.Clear()

        LEDs = 0
        If Me.Width < SizeCurrent Then
            LEDs = 1
        Else
            Dim _MeWidth As Integer = Me.Width - SizeCurrent
            LEDs = (_MeWidth \ (SizeOld + Space)) + 1
        End If

        For i As UInteger = 1 To LEDs Step +1
            dictOfLeds.Add(i, 0)
        Next
        'MsgBox(LEDs)
    End Sub
    Private dictOfLeds As New Dictionary(Of UInt32, UInt16)
    Private Space As Integer = 2
    Private SizeCurrent = 7
    Private SizeOld As Integer = 3
    Private ColorOld As Brush = New SolidBrush(Color.Aqua)
    Private ColorCurrent As Brush = New SolidBrush(Color.Blue)
    Private _Pen As New Pen(Brushes.AliceBlue, 5.0F)
    Private _StartPoint As New Point(0, 0)
    Private _EndPoint As New Point(0, 0)
    'THIS SUB WILL BE CALLED WHENEVER THE "[Value]" Property is changed
    Private Shadows Sub [Refresh]()
        For i = LEDs To 2 Step -1
            If i = 2 Then dictOfLeds(1) = Value
            dictOfLeds(i) = dictOfLeds(i - 1)
        Next
        Me.CreateGraphics.Clear(Color.Green)
        Dim int As Integer
        For i As Integer = 1 To LEDs Step +1
            If i = 1 Then
                int = (SizeCurrent \ 2) + Space
                _Pen.Width = SizeCurrent
                _Pen.Brush = ColorCurrent
            ElseIf i = 2 Then
                int = (SizeCurrent + Space) + ((SizeOld \ 2) + Space)
                _Pen.Width = SizeOld
                _Pen.Brush = ColorOld
            ElseIf i > 2 Then
                int += SizeOld + Space
                _Pen.Width = SizeOld
                _Pen.Brush = ColorOld
            End If
            Dim _location As New Point(0, CInt(Me.Height \ 2))
            _StartPoint.X = (Me.Width) - int
            _StartPoint.Y = (_location.Y - (Me.Height / 2) + dictOfLeds.Item(i))
            _EndPoint.X = (Me.Width) - int
            _EndPoint.Y = (_location.Y + (Me.Height \ 2) + (Me.Height / 2) + dictOfLeds.Item(i))
            'Me.Invalidate() to raise Onpaint when painting via Onpaint
           
 Me.CreateGraphics.DrawLine(_Pen, _StartPoint, _EndPoint)
        Next

    End Sub
Protected Overrides Sub Onpaint(Byval sender as Object, Byval e as painteventargs)
'WHEN PASSED THE e.graphics.drawline(_pen,_startpoint, _endpoint) result was nothing
End Sub
End Class

The result looks like this in my project (not the above code). the capture looks good but in reality it flickers while refreshing!

[.paul.]

How to: Reduce Graphics Flicker with Double Buffering for Forms and Controls:

http://msdn.microsoft.com/en-us/libr...v=vs.110).aspx

[Begi]

Thanks for the reply, i have tried it out before but i coulnt see any difference, maybe because i was using Me.CreateGraphics.

Do you have any clue why when i pass the e.Graphics.Drawline(_pen, _StartPoint, _EndPoint) to OnPaint it doesnt refresh anything? I used to call it via Me.Invalidate, Me.Refresh, Me.Update but the OnPaint doesnt reflect the code given?

Anyone help!

[boops boops]

CreateGraphics causes all kinds of trouble when used for drawing. Your OnPaint sub won't have any effect if you have left out MyBase.OnPaint. I suggest you transfer all the code except Invalidate from [Refresh] to OnPaint, replacing Me.CreateGraphics by e.Graphics. Unless you need it for some other reason, you could then get rid of the shadowed Refresh sub altogether and put Me.Invalidate in the property Set clause.

To prevent flickering, put Me.DoubleBuffered = True in the UserControl's New sub.

BB

[Begi]

Thanks boops boops, that helped. Also there was an error in my code which i realised later. Putting MyBase.OnPaint(e) at the end of OnPaint() clause was not necessary.


Here is the solution for other people having flickering Controls, i also have found a manual way to buffer the drawings on Web, but setting Me.DoubleBuffered = True would be less code;

Class TEST
 Inherits Form       ' or Inherits UserControl whatever!

    Private _doBuffer As Boolean = False ' We will use the automated solution Me.DoubleBuffered = True, otherwise Me.DoubleBuffered = False if using "_doBuffer"
    Private _backBuffer As Bitmap


Sub New
 Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or ControlStyles.UserPaint Or ControlStyles.DoubleBuffer, True)
End Sub

'CALL THIS SUB WHENEVER YOU WANT TO PAINT THE STUFF ON "OnPaint()"
  PUBLIC SUB Paint_MyStuff
    Invalidate 
  End Sub

 Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
        If _backBuffer Is Nothing Then
            _backBuffer = New Bitmap(Me.ClientSize.Width, Me.ClientSize.Height)
        End If
        Dim g As Graphics = Nothing

        If _doBuffer Then
            g = Graphics.FromImage(_backBuffer)
        Else
            g = e.Graphics
        End If
        g.Clear(Me.BackColor)


'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'STUFF TO DRAW ON CONTROL;
        For i As Integer = 0 To Me.Height Step +1
            g.DrawLine(New Pen(Brushes.Blue, 1.0F), New Point(0,0), New Point(Me.Width, i))
        Next
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
       
        If _doBuffer Then
            g.Dispose()
            'Copy the back buffer to the screen
            e.Graphics.DrawImageUnscaled(_backBuffer, 0, 0)
        End If
        MyBase.OnPaint(e) '//optional but not recommended
    End Sub 'OnPaint
  

    Protected Overrides Sub OnPaintBackground(ByVal pevent As PaintEventArgs)
    'Do stuff (OPTIONAL)
    End Sub 'OnPaintBackground


    'Don't allow the background to paint
    Protected Overrides Sub OnSizeChanged(ByVal e As EventArgs)
        Me.CreateGraphics.Clear(Me.BackColor)
        
        If Not (_backBuffer Is Nothing) Then
            _backBuffer.Dispose()
            _backBuffer = Nothing
        End If
        MyBase.OnSizeChanged(e)
    End Sub 'OnSizeChanged

End Class

[Shaggy Hiker]

By the way, you shouldn't be messing with thread prioritization unless you have a REALLY good reason. Increasing the priority of a thread doesn't mean that it gets more time, it means that it gets ALL the time. Lower priority threads only get to use the CPU if there are no higher priority threads pending. In theory, boosting your app to the highest thread priority would mean that it would be at the same level as the OS noticing keypresses, and so on. That can ruin system performance and behavior because your app is dependent on getting keyboard events from the OS, but it might block the OS from even noticing keys being pressed. In practice, the impact will not be THAT bad, but it could still be pretty horrible.

[Begi]

Sounds very logically!