AutoRedraw = True?

[Guest makai]

what might be the equivalent of the VB6 AutoRedraw = True (on a form)?

[Derek Stone]

There isn't an equivalent. Just redraw what needs redrawing in the control's/form's Paint event.

[Guest makai]

I have spent a whole day trying to do exactly that with no progress

 

the concept seems simple - create a bitmap of the form whenever anything is written to it and then simply copy the bitmap to the form in the Paint event

 

I am not even anywhere close to getting it

[wyrd]

Paste your forms paint event here in this thread so we can have a look. It would help a lot more if we could see the code ourselves. :)

[Guest makai]

if you minimize and then restore the text is gone - trying the text generated in form activate and the button event

 

Public Class Form1
   Inherits System.Windows.Forms.Form

   Private b1 As Bitmap

   Protected Overrides Sub OnActivated(ByVal e As System.EventArgs)
       Me.Text = "AutoRedraw Test"
       Me.BackColor = System.Drawing.Color.White

       FormPrint(".NET Printing", 10, 10)
   End Sub

   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
       FormPrint("2nd Printing", 100, 100)
   End Sub

   Private Sub FormPrint(ByVal t$, ByVal x1%, ByVal y1%)
       Dim g1 As Graphics = Me.CreateGraphics()

       System.Windows.Forms.Application.DoEvents()

       g1.DrawString(t, New Font("Verdana", 12), _
           Brushes.Black, x1, y1)

       System.Windows.Forms.Application.DoEvents()

       b1 = New Bitmap(Me.Size.Width, Me.Size.Height, g1)
   End Sub

   ' Redraw the form.
   Private Sub Form1_Paint( _
       ByVal sender As Object, _
       ByVal e As System.Windows.Forms.PaintEventArgs) _
           Handles MyBase.Paint

       If Not (b1 Is Nothing) Then e.Graphics.DrawImage(b1, 0, 0)
   End Sub
End Class

[Derek Stone]

Call FormPrint in Form1_Paint.

[Guest makai]

no then I have to print everything that I already printed (something that I would not be able to do without restarting the whole program) - I just want to refresh what has already BEEN printed

 

the trick is knowing the graphics methods work in order to copy the form to a bitmap and then copying it back to the form in the paint event

 

apparently there is something to the graphics that does not work in my code

[wyrd]

I see what you're trying to do (I think).

 

You have to call the Refresh method to trigger the Paint Event... so in your FormPrint method, add this as the last line;

 

Me.Refresh()

[Guest makai]

after 2 days I finally arrived at the solution - as I suspected it is fairly simple application of the Graphics Object

 

 
Option Strict On

Public Class Form1
   Inherits System.Windows.Forms.Form

   'Bitmap holds picture of the Form
   Private b1 As Bitmap
   'Graphics object (buffer)
   Private g1 As Graphics

   Private Sub Form1_Activated(ByVal sender As Object, _
       ByVal e As System.EventArgs) Handles MyBase.Activated

       Static done As Boolean = False

       If Not done Then
           Text = "AutoRedraw Test"
           BackColor = System.Drawing.Color.White

           'Create the initial bitmap from Form
           b1 = New Bitmap(Me.Size.Width, _
               Me.Size.Height, Me.CreateGraphics())

           'Create the Graphics Object buffer
           ' which ties the bitmap to it so that
           ' when you draw something on the object
           ' the bitmap is updated
           g1 = Graphics.FromImage(b1)

           'Print something
           FormPrint(".NET Printing", 10, 10)

           'Prevent reentry to initialization
           done = True
       End If
   End Sub

   'Print something else
   Private Sub Button1_Click(ByVal sender As System.Object, _
       ByVal e As System.EventArgs) Handles Button1.Click

       FormPrint("2nd Printing", 100, 100)
   End Sub

   Private Sub FormPrint(ByVal t$, ByVal x1%, ByVal y1%)
       'Printing to the graphics buffer (not form)
       ' updates the associated bitmap b1
       g1.DrawString(t, New Font("Verdana", 12), _
           Brushes.Black, x1, y1)

       'Copy the bitmap to the form
       Me.CreateGraphics.DrawImage(b1, 0, 0)
   End Sub

   Private Sub Form1_Paint( _
       ByVal sender As Object, _
       ByVal e As System.Windows.Forms.PaintEventArgs) _
           Handles MyBase.Paint

       'Copy the bitmap to the form
       e.Graphics.DrawImage(b1, 0, 0)
   End Sub

End Class