blinking issue while using invalidate

  • Thread starter Thread starter Alex Glass
  • Start date Start date
A

Alex Glass

I have been having problems using invalidate which forms when the mouse is
triggering the screen repainting. It seems that if the invalidate function
is called too frequently and unsightly blinking effect happens. Below is a
sample program which produces the effect I am trying to explain. Is there a
different way to cause the text to be repainted in response to the events
without causing the blinking?

Any suggestions or help would be greatly appreciated
-Alex Glass

' BLINK.VB
Public Class Blink

Inherits System.Windows.Forms.Form

Private mouse_pos_rect As Rectangle

Private form_size_rect As Rectangle

Private mouse_pos As String

Private form_size As String

Public Sub New()

MyBase.New()

ClientSize = New System.Drawing.Size(292, 260)

Name = "Blink"

Text = "Blink"

form_size_rect.X = 10

form_size_rect.Y = 10

form_size_rect.Height = 40

form_size_rect.Width = 300

mouse_pos_rect.X = 10

mouse_pos_rect.Y = 60

mouse_pos_rect.Height = 40

mouse_pos_rect.Width = 300

End Sub

Protected Overrides Sub OnPaint(ByVal e As
System.Windows.Forms.PaintEventArgs)

Dim g As Graphics = e.Graphics

Dim f As New Font("Arial", 30, FontStyle.Regular, GraphicsUnit.Pixel)

g.DrawString(mouse_pos, f, Brushes.Black, ToRectF(mouse_pos_rect))

g.DrawString(form_size, f, Brushes.Black, ToRectF(form_size_rect))

End Sub

Private Sub Blink_Resize(ByVal sender As Object, ByVal e As
System.EventArgs) Handles MyBase.Resize

form_size = "(" & ClientSize.Width & ", " & ClientSize.Height & ")"

Invalidate(form_size_rect)

End Sub

Private Sub Blink_MouseMove(ByVal sender As Object, ByVal e As
System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseMove

mouse_pos = "(" & e.X & ", " & e.Y & ")"

Invalidate(mouse_pos_rect)

End Sub

Private Function ToRectF(ByVal rect As Rectangle) As RectangleF

Return New RectangleF(rect.X, rect.Y, rect.Width, rect.Height)

End Function

End Class
 
Blinking occurs when you can perceive consecutive steps of drawing. In your
case the form's surface is always cleared before entering OnPaint, which
causes the nasty effect. You can improve this by enabling double-buffering,
either manual or automatic. If you want automatic, add this code in the
constructor:

this.SetStyle(
ControlStyles.AllPaintingInWmPaint |
ControlStyles.DoubleBuffer |
ControlStyles.Opaque |
ControlStyles.UserPaint,
true);
 
thanks for the help lukasz!

lukasz said:
Blinking occurs when you can perceive consecutive steps of drawing. In your
case the form's surface is always cleared before entering OnPaint, which
causes the nasty effect. You can improve this by enabling double-buffering,
either manual or automatic. If you want automatic, add this code in the
constructor:

this.SetStyle(
ControlStyles.AllPaintingInWmPaint |
ControlStyles.DoubleBuffer |
ControlStyles.Opaque |
ControlStyles.UserPaint,
true);


is there
Click to expand...
 
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