VB.net PaintEventArgs Handling.

I am working on a graphics intensive project and would like to create a class that includes a number of drawing routines. These routines could then be called from any number of places in the code. Here's an example of the type of function that I'd like to include in the class:

  Private Sub DrawEllipseGeom(
    ByVal numX As Integer,
    ByVal numY As Integer,
    ByVal numWidth As Integer,
    ByVal numHeight As Integer,
    ByVal colColor As Color,
    ByVal LineWidth As Long)

    Dim penDraw As New Pen(Drawing.Color.Black)
    Dim PenColor As Color = colColor
    penDraw.Color = PenColor
    penDraw.Width = LineWidth
 
    e.graphics.DrawEllipse(penDraw, numX, numY, numWidth, numHeight)
    Me.Invalidate()
    penDraw.Dispose()
  End Sub

The problem I'm trying to solve concerns passing e as PaintEventArgs to the functions in the class. Is there a way to do this or do I need to rethink my approach? I understand that the example above is trivial, but some of the functions will create multiple paths, perform transformations, etc. I would prefer not to have to recreate the code on each form by overriding the paint on each form.

Any ideas?

Thank you for reading my post.
LVL 46
fritz_the_blankAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

AndyAinscowFreelance programmer / ConsultantCommented:
>>The problem I'm trying to solve concerns passing e as PaintEventArgs to the functions in the class

Why is that a problem?
fritz_the_blankAuthor Commented:
Thank you for answering. Let's say that I'd like to fire the code above from a button. The function expects e as PaintEventArgs as a parameter. I can't seem to pass that to the function via a click event.
AndyAinscowFreelance programmer / ConsultantCommented:
Have a look at:
https://msdn.microsoft.com/en-us/library/5y289054(v=vs.110).aspx

I've not tried it but this might be what you want
   ' Create a Graphics object for the Control.
   Dim g As Graphics = Me.CreateGraphics()
   MyCustomDrawingRoutine(g)
  g.Dispose()
CompTIA Network+

Prepare for the CompTIA Network+ exam by learning how to troubleshoot, configure, and manage both wired and wireless networks.

fritz_the_blankAuthor Commented:
Thank you for your comment.

I'm able to do that, but there's a big difference between using .CreateGraphics and e. as PaintEventArgs. I need to be able to create paths and figures from a variety of functions and have them work with the same event handler. This allows me to create layers, manipulate them, stack them, and then finally output them in the order needed.
AndyAinscowFreelance programmer / ConsultantCommented:
If you use Invalidate in the button click then a paint event will be fired.  You might have to then call your routines from the paint event after all.

However I don't understand your problem.  the PaintEventArgs contains the graphics object, the rectangle needing redrawing and nothing else for drawing.
fritz_the_blankAuthor Commented:
I'm sorry. Let me provide some code...

I override the paint handler like this:

  Private Sub frmDrawTestPaint(ByVal sender As Object, ByVal e As PaintEventArgs) Handles MyBase.Paint
    Dim g As Graphics = e.Graphics
  End Sub

Now, what I'd like to do is to pass g to different subroutines or functions.
AndyAinscowFreelance programmer / ConsultantCommented:
As mentioned in an earlier comment - you pass it like you would any other parameter a function requires

  Private Sub frmDrawTestPaint(ByVal sender As Object, ByVal e As PaintEventArgs) Handles MyBase.Paint
    Dim g As Graphics = e.Graphics
MyCustomDrawingRoutine(g)
  End Sub
fritz_the_blankAuthor Commented:
Andy--

Thank you for staying with me! I've been away from programming for a while, and I haven't had time to study event handling in .Net as yet. So, let's say I call the routine from a form button:

  Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
     frmDrawTestPaint(Me, e)
  End Sub

I receive an error indicating that the mouse click event cannot be converted to a paint event. That makes sense, but I don't know how to get around that.
AndyAinscowFreelance programmer / ConsultantCommented:
An Invalidate will flag for a repaint.  As you want to run a function after the button click then something like the following (air code) is along the lines of what you want.
private bRunFunction as boolean = false

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
     bRunFunction = true
     Invalidate
  End Sub

Sub Paint(.....)
  if bRunFunction then MyCustomDrawRoutine(e.Graphics)   'or e if you wanted other things in the PaintEventArgs
end sub

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
fritz_the_blankAuthor Commented:
Thank you very much. That's just what I needed.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Visual Basic.NET

From novice to tech pro — start learning today.