Getting started with scottplot tutorial: getting and displaying values at the mouse

1 Effect display

ScottPlot It is a very good open source chart Library , Official routines are also relatively rich , This article gives a simple example of how to get the value at the mouse .

2 establish Demo engineering

Create a blank Winform Desktop applications

  introduce ScottPlot library

Right click solution , Click on Nuget Package management , Search full name ScottPlot：

  After the import is completed, the toolbox of the design window will appear FromsPlot Control , Drag and drop it into the design interface , Here are two more controls ：

Button Used to generate random data by clicking ,Label Used to display the value of the mouse position , The initial position is arbitrary , In the program, we let it follow the mouse to display in the appropriate position .

  Changed in the figure Label Background color and border style , It looks better like this .

 3 Code editing

Double click the added refresh Button You can quickly add monitoring and enter code editing mode .

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

namespace ScottPlotTest
{
    public partial class Form1 : Form
    {
        public const int MAX_LOG_LENGHT = 1000;

        private double[] values = new double[MAX_LOG_LENGHT];
        private int dataCnt = 0;
        private ScottPlot.Plottable.SignalPlot signalPlot;
        public Form1()
        {
            InitializeComponent();

            /*
             * 1. Set data source , Customize X Axis labels 
             */
            var plt = formsPlot1.Plot;
            plt.Title(" Real time curve ");
            plt.SetAxisLimitsY(0, 1600);
            plt.SetAxisLimitsX(0, 20);
            signalPlot = plt.AddSignal(values);
            signalPlot.MaxRenderIndex = dataCnt;
            // Generate X Axis labels 
            double[] labelPositions = new double[MAX_LOG_LENGHT];
            string[] labelsXAxis = new string[MAX_LOG_LENGHT];
            for (int i = 0; i < MAX_LOG_LENGHT; i++)
            {
                labelsXAxis[i] = i.ToString();
                labelPositions[i] = i;
            }
            plt.XTicks(labelPositions, labelsXAxis);
            formsPlot1.Refresh();

            // Mouse movement monitoring 
            formsPlot1.MouseMove += FormsPlot1_MouseMove;
        }

        protected override void OnSizeChanged(EventArgs e)
        {
            base.OnSizeChanged(e);
            /*
             * 2. Auto fit window size 
             */
            formsPlot1.Location = new Point(12, 51);
            formsPlot1.Width = Size.Width - 48;
            formsPlot1.Height = Size.Height - 108;
        }

        private void FormsPlot1_MouseMove(object sender, MouseEventArgs e)
        {
            /*
             * 3. Calculate the value at the mouse and pass Label Show 
             */
            label1.Visible = false;
            Point mouseLocation = e.Location;
            double xCoordinate = formsPlot1.Plot.GetCoordinateX(mouseLocation.X);
            int xAxis = Math.Abs((int)Math.Round(xCoordinate));
            if (xAxis < dataCnt)
            {
                int y = (int)formsPlot1.Plot.GetPixelY(values[xAxis]);
                if (Math.Abs(mouseLocation.Y - y) < 16)
                {
                    label1.Text = "Y:" + y.ToString()
                        + "\nX:" + xAxis.ToString();
                    // adjustment label To the right place 
                    mouseLocation.Y += label1.Height;
                    mouseLocation.X += 16;
                    label1.Location = mouseLocation;
                    label1.Visible = true;
                }
            }
        }

        private void Button1_Click(object sender, EventArgs e)
        {
            /*
             * 4. Generate random data 
             */
            GetData();
            formsPlot1.Plot.AxisAuto();
            formsPlot1.Refresh();
        }

        private void GetData()
        {
            Random rand = new Random();
            values[dataCnt] = 1000 + rand.Next(-100, 100);
            signalPlot.MaxRenderIndex = dataCnt;
            dataCnt++;
            if(MAX_LOG_LENGHT == dataCnt)
            {
                dataCnt = 0;
            }
        }
    }
}

The code did 4 thing ：

1. Set data source ; Customize X Axis labels , Show only integers .

2. Auto fit window size .

3. Calculate the value at the mouse and pass Label Show .

4. Generate random data .

We focus on how to get the value at the mouse , adopt GetCoordinateX() obtain X The value of the icon curve coordinate corresponding to the axis mouse pixel , Then take the nearest integer , This number is the index of the data , Here you get X-Y Value of pair . But we need the mouse to point to the data point before it displays , So the next step is through GetPixelY() obtain Y The pixel value corresponding to the axis coordinate value , In the distance 16 Display within pixels Label, Otherwise, it will not show .

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