Graphing/Base/Forms/SetZoomForm.cs

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

namespace Graphing.Forms
{
    public partial class SetZoomForm : Form
    {
        private double minZoomRange;
        private double maxZoomRange;

        private double zoomLevel;

        private readonly GraphForm form;

        public SetZoomForm(GraphForm form)
        {
            InitializeComponent();

            minZoomRange = 1 / (form.ZoomLevel * 2);
            maxZoomRange = 2 / form.ZoomLevel;
            zoomLevel = 1 / form.ZoomLevel;

            ZoomTrackBar.Value = (int)(ZoomToFactor(zoomLevel) * (ZoomTrackBar.Maximum - ZoomTrackBar.Minimum) + ZoomTrackBar.Minimum);

            this.form = form;
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            ZoomMaxValue.Text = maxZoomRange.ToString("0.00");
            ZoomMinValue.Text = minZoomRange.ToString("0.00");

            ValueLabel.Text = $"{zoomLevel:0.00}x";

            base.OnPaint(e);

            form.ZoomLevel = 1 / zoomLevel;
            form.Invalidate(false);
        }

        private double FactorToZoom(double factor)
        {
            return minZoomRange + (factor * factor) * (maxZoomRange - minZoomRange);
        }
        private double ZoomToFactor(double zoom)
        {
            double sqrValue = (zoom - minZoomRange) / (maxZoomRange - minZoomRange);
            return Math.Sign(sqrValue) * Math.Sqrt(Math.Abs(sqrValue));
        }

        private void ZoomTrackBar_Scroll(object? sender, EventArgs e)
        {
            double factor = (ZoomTrackBar.Value - ZoomTrackBar.Minimum) / (double)(ZoomTrackBar.Maximum - ZoomTrackBar.Minimum);
            zoomLevel = FactorToZoom(factor);

            Invalidate(true);
        }

        private void ZoomMinValue_TextChanged(object? sender, EventArgs e)
        {
            double original = minZoomRange;
            try
            {
                double value;
                if (string.IsNullOrWhiteSpace(ZoomMinValue.Text) ||
                    ZoomMinValue.Text.EndsWith('.'))
                {
                    return;
                }
                else
                {
                    value = double.Parse(ZoomMinValue.Text);
                    if (value < 1e-2 || value > 1e3 || value > maxZoomRange) throw new();
                }

                minZoomRange = value;
                ZoomTrackBar.Value = (int)Math.Clamp(ZoomToFactor(zoomLevel) * (ZoomTrackBar.Maximum - ZoomTrackBar.Minimum) + ZoomTrackBar.Minimum, ZoomTrackBar.Minimum, ZoomTrackBar.Maximum);
                double factor = (ZoomTrackBar.Value - ZoomTrackBar.Minimum) / (double)(ZoomTrackBar.Maximum - ZoomTrackBar.Minimum);
                double newZoom = FactorToZoom(factor);

                zoomLevel = newZoom;
                if (newZoom != factor) Invalidate(true);
            }
            catch
            {
                minZoomRange = original;
                ZoomMinValue.Text = minZoomRange.ToString("0.00");
            }
        }

        private void ZoomMaxValue_TextChanged(object sender, EventArgs e)
        {
            double original = maxZoomRange;
            try
            {
                double value;
                if (string.IsNullOrWhiteSpace(ZoomMaxValue.Text) ||
                    ZoomMaxValue.Text.EndsWith('.'))
                {
                    return;
                }
                else
                {
                    value = double.Parse(ZoomMaxValue.Text);
                    if (value < 1e-2 || value > 1e3 || value < minZoomRange) throw new();
                }

                maxZoomRange = value;
                ZoomTrackBar.Value = (int)Math.Clamp(ZoomToFactor(zoomLevel) * (ZoomTrackBar.Maximum - ZoomTrackBar.Minimum) + ZoomTrackBar.Minimum, ZoomTrackBar.Minimum, ZoomTrackBar.Maximum);
                double factor = (ZoomTrackBar.Value - ZoomTrackBar.Minimum) / (double)(ZoomTrackBar.Maximum - ZoomTrackBar.Minimum);
                double newZoom = FactorToZoom(factor);

                zoomLevel = newZoom;
                if (newZoom != factor) Invalidate(true);
            }
            catch
            {
                maxZoomRange = original;
                ZoomMaxValue.Text = maxZoomRange.ToString("0.00");
            }
        }
    }
}