CODEWITHSUNDEEP
c#winforms
user3832863
user3832863

Reputation: 97

The simplest Paint program isn't working in C# Windows Forms

I'm plowing through the Dietle C# book one page at a time and I'm stuck.

On page 555, there's the most basic drawing program you can imagine. As you move your mouse around, it's supposed to draw an ellipse on the screen.

Well, mine doesn't.

I've checked everything possible. I've gone onto the Dietel website and downloaded the code and tried that. I think I'm doing something wrong outside of the text-based programming. I mean, there are settings and stuff in the properties windows.

I think I got it all right, but nothing seems to work. But obviously I don't have it all right or it would work.

The full code is a bit longer than what I have below, but even this simplified code doesn't work. It's supposed to draw ellipses any time you have the mouse on the screen. Studio Express does a nice job of catching a lot of syntax errors, but of course it can't catch logic errors. Any ideas as to what's wrong?

using System;
using System.Drawing;
using System.Windows.Forms;

namespace WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            using (Graphics graphics = CreateGraphics())
            {
                graphics.FillEllipse(
                    new SolidBrush(Color.Blue), e.X, e.Y, 20, 20);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
    }
}

Upvotes: 2

Views: 1110

Answers (3)

Florian Schmidinger
Florian Schmidinger

Reputation: 4692

I would do it like this:

public partial class Form1 : Form
{
    private List<IDrawAble> shapes = new List<IDrawAble>();

    private MyEllipse currentlyDrawing;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        currentlyDrawing = new MyEllipse() { X1 = e.X, Y1 = e.Y, X2 = e.X, Y2 = e.Y };
        Invalidate();
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        shapes.Add(currentlyDrawing);
        currentlyDrawing = null;
        Invalidate();
    }

    private void Form1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.Clear(Color.White);
        foreach (var item in shapes)
        {
            item.Draw(e.Graphics);
        }
        if (currentlyDrawing != null)
        {
            currentlyDrawing.Draw(e.Graphics);
        }
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        if (currentlyDrawing != null)
        {
            currentlyDrawing.X2 = e.X;
            currentlyDrawing.Y2 = e.Y;
            Invalidate();
        }
    }
}

class MyEllipse : IDrawAble
{
    public int X1 { get; set; }
    public int Y1 { get; set; }
    public int X2 { get; set; }
    public int Y2 { get; set; }


    public void Draw(Graphics g)
    {
        g.FillEllipse(new SolidBrush(Color.Blue), X1, Y1, X2 - X1, Y2 - Y1);
    }
}

interface IDrawAble
{
    void Draw(Graphics g);
}

Make sure all eventhandlers are hooked to the events of the form. To get rid of the flickering set the DoubleBuffered Property of the Form to true.

Upvotes: 2

Sharif Sk
Sharif Sk

Reputation: 1

What is it doing now?

Just to Add.

  1. Make sure your event MouseMove is mapped with the Method Form1_MouseMove

  2. In the Method Hieght and weight are 20 which means it is circle and not eclipse.

  3. for to debug first replace e.X and e.Y with number in below snippet it is 0

       SolidBrush redBrush = new SolidBrush(Color.Red);

    // Create location and size of ellipse. 
    float x = 0.0F;
    float y = 0.0F;
    float width = 200.0F;
    float height = 100.0F;         


    using (Graphics graphics = CreateGraphics())
    {
        graphics.FillEllipse(redBrush, x, y, width, height);
    }

Upvotes: 0

Ibki
Ibki

Reputation: 91

MouseMove Event??

public Form1()
{
     InitializeComponent();
     this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.Form1_MouseMove);
}

Upvotes: 2

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