Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

problem abstracting border drawing

Posted on 2003-10-29
12
328 Views
Last Modified: 2010-04-16
ref. the code below
have a class that draws a border around itself
want a base class that handles the border drawing

:: here the border gets drawn ::

public MyClass
{
     public MyClass()
     {
     }

     protected override void OnResize(EventArgs e)
     {
          this.Invalidate();
     }

     protected override void OnPaint(PaintEventArgs e)
     {
          Graphics g = e.Graphics;

          /* draw shape */

          /* draw border */
     }
}

:: here it never gets drawn ::

public BaseClass
{
     public BaseClass()
     {
          this.Invalidated += new InvalidateEventHandler(this.DrawBorder);
     }

     protected void DrawBorder(object sender, InvalidateEventArgs e)
     {
          Graphics g = Graphics.FromWhnd(this.Handle);

          /* draw border */
     }
}

:: solution ::

that's why I'm here :D
0
Comment
Question by:cuynen
  • 5
  • 3
  • 2
  • +1
12 Comments
 
LVL 11

Expert Comment

by:Agarici
ID: 9650310
try adding your border drawing  to the paint event
0
 
LVL 2

Author Comment

by:cuynen
ID: 9650641
:: subscribing to the Paint event ::

public BaseClass
{
     public BaseClass()
     {
          this.Paint += new PaintEventHandler(this.DrawBorder);
     }

     protected void DrawBorder(object sender, PaintEventArgs e)
     {
          Graphics g = e.Graphics;

          /* draw border */
     }
}

:: thoughts ::

it doesn't work because I've overridden the protected OnPaint method in the derived class
if I comment out the overridden method, the border is drawn
but of course then my derived class serves no purpose anymore :)
0
 
LVL 11

Accepted Solution

by:
Agarici earned 250 total points
ID: 9650742
then in the derived class call 'base.OnPaint' before doing any other drawing
0
Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 2

Author Comment

by:cuynen
ID: 9650926
so there is no way the base class can auto-draw the border after the derived is finished painting?
0
 
LVL 11

Expert Comment

by:Agarici
ID: 9650954
the 'OnPaint' method in the base class wont get called unless you call 'base.OnPaint'
0
 
LVL 10

Expert Comment

by:ptmcomp
ID: 9656224
How about this:

public MyClass
{
    public MyClass()
    {
    }

    protected override void OnResize(EventArgs e)
    {
         this.Invalidate();
    }

    protected override void OnPaint(PaintEventArgs e)
    {
         Graphics g = e.Graphics;

         /* draw shape */

        base.OnPaint(e);
    }
}


public BaseClass
{
    public BaseClass()
    {
    }

    protected override void OnPaint(PaintEventArgs e)
    {
         Graphics g = e.Graphics;

         /* draw border */
    }
}
0
 
LVL 2

Author Comment

by:cuynen
ID: 9656268
yes, that's what I had after Agarici's second comment
0
 
LVL 10

Expert Comment

by:ptmcomp
ID: 9656326
You could use cuynen's variant.
0
 
LVL 3

Expert Comment

by:WiB
ID: 9659071
Any special reason to draw the border in base class?
0
 
LVL 2

Author Comment

by:cuynen
ID: 9659335
so all subclasses will have a border drawn around them
0
 
LVL 2

Author Comment

by:cuynen
ID: 9659336
*** around their visual representation, that is
0
 
LVL 3

Expert Comment

by:WiB
ID: 9660538
The code in comment from  ptmcomp
Date: 10/31/2003 01:03AM PST  
should work perfectly.

 
0

Featured Post

Free Tool: Postgres Monitoring System

A PHP and Perl based system to collect and display usage statistics from PostgreSQL databases.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Summary: Persistence is the capability of an application to store the state of objects and recover it when necessary. This article compares the two common types of serialization in aspects of data access, readability, and runtime cost. A ready-to…
We all know that functional code is the leg that any good program stands on when it comes right down to it, however, if your program lacks a good user interface your product may not have the appeal needed to keep your customers happy. This issue can…
Nobody understands Phishing better than an anti-spam company. That’s why we are providing Phishing Awareness Training to our customers. According to a report by Verizon, only 3% of targeted users report malicious emails to management. With compan…
Finds all prime numbers in a range requested and places them in a public primes() array. I've demostrated a template size of 30 (2 * 3 * 5) but larger templates can be built such 210  (2 * 3 * 5 * 7) or 2310  (2 * 3 * 5 * 7 * 11). The larger templa…

809 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question