CODEWITHSUNDEEP
c#plot
BigBug
BigBug

Reputation: 6290

Plotting a point

I have code which will draw a graph that scales if the user attempts to resize the form(by dragging the form's corners). The form will get an x and y co-ordinate in a textbox. When a button is pushed, i want to plot the point which they have indicated. However, the Click event contains the parameters Object Sender and EventArgs e. The OnPaint method (which i am overriding in order to draw the graph) has the parameter PaintEventArgs.

Due to this, when the button is clicked i cannot do the following code: 

g.DrawString("♫", new Font("Calibri", 12), new SolidBrush(Color.HotPink), (PlotArea.X + (7 - xMin)* PlotArea.Width/(xMax - xMin)), (PlotArea.Bottom - (6 - yMin) * PlotArea.Height / (yMax - yMin)));

This is because "g" is of type PaintEventArgs. How do i get around this so that in the onClick method i can plot the co-ordinate?

My code is as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace PlotIt
{
    public partial class Form1 : Form
    {
        public static List<TheList> GraphPoints = new List<TheList>();

        //Define the drawing area
        private Rectangle PlotArea;
        //Unit defined in world coordinate system:
        private float xMin = 0f;
        private float xMax = 10f;
        private float yMin = 0f;
        private float yMax = 10f;
        //Define the offset in pixel:
        private int offset = 150;
        Graphics g;

        Boolean buttonPressed = false; 
        public Form1()
        {
            InitializeComponent();
            this.SetStyle(ControlStyles.ResizeRedraw, true);
            this.BackColor = Color.White;

        }

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

            //Calculate the location and size of the drawing area
            //within which we want to draw the graphics:
            Rectangle rect = ClientRectangle;

            PlotArea = new Rectangle(rect.Location, rect.Size);
            PlotArea.Inflate(-offset, -offset);

            g.DrawRectangle(Pens.Black, PlotArea);

            Pen aPen = new Pen(Color.Green, 3);
            g.DrawLine(aPen, Point2D(new PointF(5, 0)), Point2D(new PointF(5, 10)));
            g.DrawLine(aPen, Point2D(new PointF(0, 5)), Point2D(new PointF(10, 5)));

            aPen.Dispose();
            g.Dispose();


        }



        private PointF Point2D(PointF ptf)
        {
            PointF aPoint = new PointF();

            aPoint.X = PlotArea.X + (ptf.X - xMin) * PlotArea.Width / (xMax - xMin);

            aPoint.Y = PlotArea.Bottom - (ptf.Y - yMin) * PlotArea.Height / (yMax - yMin);

            return aPoint;
        }



        private void btnPlotGraph_Click(object sender, EventArgs e)
        {



            g.DrawString("♫", new Font("Calibri", 12), new SolidBrush(Color.HotPink),    (PlotArea.X + (7 - xMin)* PlotArea.Width/(xMax - xMin)), (PlotArea.Bottom - (6 - yMin) * PlotArea.Height / (yMax - yMin)));
        }



    }

}

Upvotes: 1

Views: 821

Answers (2)

Scott Rippey
Scott Rippey

Reputation: 15810

There is a more appropriate way to do this.

In yourClick event, you should store the coordinates, and then call this.Invalidate().

This will cause your form to redraw itself, firing the Paint event.

It is also possible to create a graphics object manually, but it is a better practice to ask the form to refresh itself by calling Invalidate.

Upvotes: 2

Mark Hall
Mark Hall

Reputation: 54552

Look into the Control.CreateGraphics Method. That should allow you to get the Graphic object you need.

Graphics g = this.CreateGraphics();
g.DrawString("♫", new Font("Calibri", 12), new SolidBrush(Color.HotPink), (PlotArea.X + (7 - xMin)* PlotArea.Width/(xMax - xMin)), (PlotArea.Bottom - (6 - yMin) * PlotArea.Height / (yMax - yMin)));
g.Dispose();

Upvotes: 2

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