I can't keep my balls from flickering

I have made this little bouncing ball app that basically moves a circle shape around the screen from inside a Timer_Tick event. The problem is that the ball "flickers" when it moves. What's the best way to stop that? If you want code, I can post it, just ask
kevin

Is the ball an image or PictureBox?

If so, it might help to actually draw it on to the parent window instead, via PaintPicture or the BitBlt API (so in essence -- using a backbuffer).

it is a shape control loaded using

VB Code:

strShapeName = "NewShape" & CStr(i)
        Me.Controls.Add "VB.Shape", strShapeName
        Set bBall(i).Bouncer = Me.Controls(strShapeName)

And you're just changing the Left and Top properties in a Timer?

What's the Timer's interval?

Have you tried the Ellipse method (of the Form) instead?

Quote:

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Originally Posted by Megatron

And you're just changing the Left and Top properties in a Timer?

What's the Timer's interval?

Have you tried the Ellipse method (of the Form) instead?

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the interval can be shorter than the time required by the code (<15ms) or bigger. I turn off the timer at the beginning of the Tick event the turn it off at the end.

edit: check that, its not the time required by code, its the resolution of the timer

I don't know what the Elliplse method is...can you briefly elaborate?
kevin

bump

Try setting the forms AutoRedraw property to true but I dont think it will help...

The fact is the shape control isnt designed to be moved a lot because it is slow, your best bet if you want to stop the flickering is too have a look as mentioned above at BitBlt or DirectX for drawing.

Bitblt Link in my sig and also try the Games and GFX forum for links to more guides!

Hope it Helps

VB Code:

Imports System.Windows.Forms
Imports System.Drawing
 
 
Namespace Utilities
 
 
 
    Public Class Win32
        Public Declare Function BitBlt Lib "gdi32" Alias "BitBlt" (ByVal hDestDC As Integer, ByVal x As Integer, _
            ByVal y As Integer, ByVal nWidth As Integer, ByVal nHeight As Integer, ByVal hSrcDC As Integer, _
              ByVal xSrc As Integer, ByVal ySrc As Integer, _
              ByVal dwRop As Integer) As Integer
        Public Declare Function GetWindowDC Lib "user32" Alias "GetWindowDC" (ByVal hwnd As Integer) As Integer
        Public Declare Function ReleaseDC Lib "user32" Alias "ReleaseDC" (ByVal hwnd As Integer, ByVal hdc As Integer) As Integer
        Public Const SRCCOPY As Integer = &HCC0020
 
    End Class
 
    
 
    Public Class ControlFunctions
 
        Public Shared Function CreateBitmap(ByVal Control As Control) As Bitmap
            If Control.Width > 0 AndAlso Control.Height > 0 Then
                Dim gDest As Graphics
                Dim hdcDest As IntPtr
                Dim hdcSrc As Integer
                Dim hWnd As Integer = Control.Handle.ToInt32
                CreateBitmap = New Bitmap(Control.Width, Control.Height)
                gDest = gDest.FromImage(CreateBitmap)
                hdcSrc = Win32.GetWindowDC(hWnd)
                hdcDest = gDest.GetHdc
                Win32.BitBlt(hdcDest.ToInt32, 0, 0, Control.Width, Control.Height, hdcSrc, 0, 0, Win32.SRCCOPY)
                gDest.ReleaseHdc(hdcDest)
                Win32.ReleaseDC(hWnd, hdcSrc)
            End If
        End Function
 
    End Class
 
 
    Public Class UpdateFlashPreventer
        Sub New()
 
        End Sub
 
        Sub New(ByVal controlToUpdate As Control)
            _control = controlToUpdate
        End Sub
 
        Private _control As Control
        Private pic As PictureBox
        Public Property Control() As Control
            Get
                Return _control
            End Get
            Set(ByVal Value As Control)
                _control = Value
            End Set
        End Property
 
        Private _inUpdate As Boolean
        Public ReadOnly Property InUpdate() As Boolean
            Get
                Return _inUpdate
            End Get
        End Property
 
        Public Sub BeginUpdate()
            If Not _control Is Nothing Then
                If Not _control.Parent Is Nothing Then
                    _inUpdate = True
                    pic = New PictureBox
                    pic.Size = _control.Size
                    pic.Image = ControlFunctions.CreateBitmap(_control)
                    pic.Location = _control.Location
                    pic.Anchor = _control.Anchor
                    pic.Dock = _control.Dock
                    _control.Parent.Controls.Add(pic)
                    pic.BringToFront()
                    pic.Refresh()
                End If
            End If
        End Sub
 
        Public Sub EndUpdate()
            If pic Is Nothing AndAlso Not _control Is Nothing Then
                If TypeOf _control.Parent.Controls(0) Is PictureBox Then
                    pic = CType(_control.Parent.Controls(0), PictureBox)
                End If
            End If
            If Not _control Is Nothing AndAlso Not _control.Parent Is Nothing AndAlso Not pic Is Nothing Then
                pic.SendToBack()
                _control.Parent.Controls.Remove(pic)
                pic.Dispose()
                pic = Nothing
                Me._inUpdate = False
            End If
        End Sub
 
    End Class

to use, place a panel control (called BallPanel) on your form and set its dockstyle to fill, and add YourBallPictureBox into the

VB Code:

Private Sub TimerTick() handles .....
        panel
        Dim flickerPreventer As New UpdateFlashPreventer(Me.BallPanel)
        flickerPreventer.BeginUpdate()
        Me.YourBallPictureBox.left = whateverX
        Me.YourBallPictureBox.left = whateverY
        flickerPreventer.EndUpdate()
 
 
    End Sub

Wrong language PeteD. This is the Classic VB section, not VB.NET. ;) :p

VB Code:

Dim dirX As Long
Dim dirY As Long
Dim speed As Long
Dim Xval As Long
Dim Yval As Long
Private Sub Form_Load()
dirX = -1
dirY = 1
speed = 10
Me.ScaleMode = vbPixels
End Sub
 
Private Sub Timer1_Timer()
Cls
Xval = Xval + (speed) * dirX
Yval = Yval + (speed) * dirY
 
If Xval < 0 Or Xval > Me.ScaleWidth Then dirX = dirX * -1
If Yval < 0 Or Yval > Me.ScaleHeight Then dirY = dirY * -1
 
Me.Circle (Xval, Yval), 20
End Sub

This will draw a circle and make it move. Hope it helps

Andrew, this thread is an old thread. Plus you forgot AutoRedraw = True ;)