Did tangent line conversion, reworked some of the UI, and started shifting.

Base/Abstract/IEquationConvertible.cs

@@ -0,0 +1,8 @@
+using Graphing.Graphables;
+
+namespace Graphing.Abstract;
+
+public interface IEquationConvertible
+{
+    public Equation ToEquation();
+}

Base/Abstract/ITranslatable.cs

@@ -0,0 +1,3 @@
+namespace Graphing.Abstract;
+
+public interface ITranslatable { }

Base/Abstract/ITranslatableX.cs

@@ -0,0 +1,6 @@
+namespace Graphing.Abstract;
+
+public interface ITranslatableX : ITranslatable
+{
+    public double OffsetX { get; set; }
+}

Base/Abstract/ITranslatableXY.cs

@@ -0,0 +1,3 @@
+namespace Graphing.Abstract;
+
+public interface ITranslatableXY : ITranslatableX, ITranslatableY { }

Base/Abstract/ITranslatableY.cs

@@ -0,0 +1,6 @@
+namespace Graphing.Abstract;
+
+public interface ITranslatableY : ITranslatable
+{
+    public double OffsetY { get; set; }
+}

Base/Base.csproj.user

@@ -16,6 +16,9 @@
     <Compile Update="Forms\SetZoomForm.cs">
       <SubType>Form</SubType>
     </Compile>
+    <Compile Update="Forms\TranslateForm.cs">
+      <SubType>Form</SubType>
+    </Compile>
     <Compile Update="Forms\ViewCacheForm.cs">
       <SubType>Form</SubType>
     </Compile>

Base/Forms/GraphForm.Designer.cs

@@ -38,13 +38,18 @@ namespace Graphing.Forms
             ButtonViewportSetCenter = new ToolStripMenuItem();
             ButtonViewportReset = new ToolStripMenuItem();
             ButtonViewportResetWindow = new ToolStripMenuItem();
-            MenuColors = new ToolStripMenuItem();
-            MenuEquations = new ToolStripMenuItem();
-            MenuEquationsDerivative = new ToolStripMenuItem();
-            MenuEquationsIntegral = new ToolStripMenuItem();
+            MenuElements = new ToolStripMenuItem();
+            MenuElementsColors = new ToolStripMenuItem();
+            MenuElementsRemove = new ToolStripMenuItem();
+            MenuOperations = new ToolStripMenuItem();
+            MenuOperationsDerivative = new ToolStripMenuItem();
+            MenuOperationsIntegral = new ToolStripMenuItem();
+            MenuConvert = new ToolStripMenuItem();
+            MenuConvertEquation = new ToolStripMenuItem();
             MenuMisc = new ToolStripMenuItem();
             MenuMiscCaches = new ToolStripMenuItem();
             MiscMenuPreload = new ToolStripMenuItem();
+            MenuOperationsTranslate = new ToolStripMenuItem();
             GraphMenu.SuspendLayout();
             SuspendLayout();
             // 
@@ -64,7 +69,7 @@ namespace Graphing.Forms
             // GraphMenu
             // 
             GraphMenu.ImageScalingSize = new Size(32, 32);
-            GraphMenu.Items.AddRange(new ToolStripItem[] { MenuViewport, MenuColors, MenuEquations, MenuMisc });
+            GraphMenu.Items.AddRange(new ToolStripItem[] { MenuViewport, MenuElements, MenuOperations, MenuConvert, MenuMisc });
             GraphMenu.Location = new Point(0, 0);
             GraphMenu.Name = "GraphMenu";
             GraphMenu.Size = new Size(1449, 42);
@@ -106,30 +111,56 @@ namespace Graphing.Forms
             ButtonViewportResetWindow.Text = "Reset Window Size";
             ButtonViewportResetWindow.Click += ButtonViewportResetWindow_Click;
             // 
-            // MenuColors
+            // MenuElements
             // 
-            MenuColors.Name = "MenuColors";
-            MenuColors.Size = new Size(101, 38);
-            MenuColors.Text = "Colors";
+            MenuElements.DropDownItems.AddRange(new ToolStripItem[] { MenuElementsColors, MenuElementsRemove });
+            MenuElements.Name = "MenuElements";
+            MenuElements.Size = new Size(131, 38);
+            MenuElements.Text = "Elements";
             // 
-            // MenuEquations
+            // MenuElementsColors
             // 
-            MenuEquations.DropDownItems.AddRange(new ToolStripItem[] { MenuEquationsDerivative, MenuEquationsIntegral });
-            MenuEquations.Name = "MenuEquations";
-            MenuEquations.Size = new Size(138, 38);
-            MenuEquations.Text = "Equations";
+            MenuElementsColors.Name = "MenuElementsColors";
+            MenuElementsColors.Size = new Size(359, 44);
+            MenuElementsColors.Text = "Colors";
             // 
-            // MenuEquationsDerivative
+            // MenuElementsRemove
             // 
-            MenuEquationsDerivative.Name = "MenuEquationsDerivative";
-            MenuEquationsDerivative.Size = new Size(360, 44);
-            MenuEquationsDerivative.Text = "Compute Derivative";
+            MenuElementsRemove.Name = "MenuElementsRemove";
+            MenuElementsRemove.Size = new Size(359, 44);
+            MenuElementsRemove.Text = "Remove";
             // 
-            // MenuEquationsIntegral
+            // MenuOperations
             // 
-            MenuEquationsIntegral.Name = "MenuEquationsIntegral";
-            MenuEquationsIntegral.Size = new Size(360, 44);
-            MenuEquationsIntegral.Text = "Compute Integral";
+            MenuOperations.DropDownItems.AddRange(new ToolStripItem[] { MenuOperationsDerivative, MenuOperationsIntegral, MenuOperationsTranslate });
+            MenuOperations.Name = "MenuOperations";
+            MenuOperations.Size = new Size(151, 38);
+            MenuOperations.Text = "Operations";
+            // 
+            // MenuOperationsDerivative
+            // 
+            MenuOperationsDerivative.Name = "MenuOperationsDerivative";
+            MenuOperationsDerivative.Size = new Size(360, 44);
+            MenuOperationsDerivative.Text = "Compute Derivative";
+            // 
+            // MenuOperationsIntegral
+            // 
+            MenuOperationsIntegral.Name = "MenuOperationsIntegral";
+            MenuOperationsIntegral.Size = new Size(360, 44);
+            MenuOperationsIntegral.Text = "Compute Integral";
+            // 
+            // MenuConvert
+            // 
+            MenuConvert.DropDownItems.AddRange(new ToolStripItem[] { MenuConvertEquation });
+            MenuConvert.Name = "MenuConvert";
+            MenuConvert.Size = new Size(118, 38);
+            MenuConvert.Text = "Convert";
+            // 
+            // MenuConvertEquation
+            // 
+            MenuConvertEquation.Name = "MenuConvertEquation";
+            MenuConvertEquation.Size = new Size(273, 44);
+            MenuConvertEquation.Text = "To Equation";
             // 
             // MenuMisc
             // 
@@ -141,17 +172,23 @@ namespace Graphing.Forms
             // MenuMiscCaches
             // 
             MenuMiscCaches.Name = "MenuMiscCaches";
-            MenuMiscCaches.Size = new Size(359, 44);
+            MenuMiscCaches.Size = new Size(299, 44);
             MenuMiscCaches.Text = "View Caches";
             MenuMiscCaches.Click += MenuMiscCaches_Click;
             // 
             // MiscMenuPreload
             // 
             MiscMenuPreload.Name = "MiscMenuPreload";
-            MiscMenuPreload.Size = new Size(359, 44);
+            MiscMenuPreload.Size = new Size(299, 44);
             MiscMenuPreload.Text = "Preload Cache";
             MiscMenuPreload.Click += MiscMenuPreload_Click;
             // 
+            // MenuOperationsTranslate
+            // 
+            MenuOperationsTranslate.Name = "MenuOperationsTranslate";
+            MenuOperationsTranslate.Size = new Size(360, 44);
+            MenuOperationsTranslate.Text = "Translate";
+            // 
             // GraphForm
             // 
             AutoScaleDimensions = new SizeF(13F, 32F);
@@ -172,17 +209,22 @@ namespace Graphing.Forms
 
         private Button ResetViewportButton;
         private MenuStrip GraphMenu;
-        private ToolStripMenuItem MenuColors;
         private ToolStripMenuItem MenuViewport;
         private ToolStripMenuItem ButtonViewportSetZoom;
         private ToolStripMenuItem ButtonViewportSetCenter;
         private ToolStripMenuItem ButtonViewportReset;
         private ToolStripMenuItem ButtonViewportResetWindow;
-        private ToolStripMenuItem MenuEquations;
-        private ToolStripMenuItem MenuEquationsDerivative;
-        private ToolStripMenuItem MenuEquationsIntegral;
+        private ToolStripMenuItem MenuOperations;
+        private ToolStripMenuItem MenuOperationsDerivative;
+        private ToolStripMenuItem MenuOperationsIntegral;
         private ToolStripMenuItem MenuMisc;
         private ToolStripMenuItem MenuMiscCaches;
         private ToolStripMenuItem MiscMenuPreload;
+        private ToolStripMenuItem MenuConvert;
+        private ToolStripMenuItem MenuConvertEquation;
+        private ToolStripMenuItem MenuElements;
+        private ToolStripMenuItem MenuElementsColors;
+        private ToolStripMenuItem MenuElementsRemove;
+        private ToolStripMenuItem MenuOperationsTranslate;
     }
 }

Base/Forms/GraphForm.cs

@@ -255,9 +255,15 @@ public partial class GraphForm : Form
         Invalidate(false);
     }
 
-    public void Graph(params Graphable[] able)
+    public void Graph(params Graphable[] newAbles)
     {
-        ables.AddRange(able);
+        ables.AddRange(newAbles);
+        RegenerateMenuItems();
+        Invalidate(false);
+    }
+    public void Ungraph(params Graphable[] ables)
+    {
+        this.ables.RemoveAll(x => ables.Contains(x));
         RegenerateMenuItems();
         Invalidate(false);
     }
@@ -348,9 +354,12 @@ public partial class GraphForm : Form
 
     private void RegenerateMenuItems()
     {
-        MenuColors.DropDownItems.Clear();
-        MenuEquationsDerivative.DropDownItems.Clear();
-        MenuEquationsIntegral.DropDownItems.Clear();
+        MenuElementsColors.DropDownItems.Clear();
+        MenuElementsRemove.DropDownItems.Clear();
+        MenuOperationsDerivative.DropDownItems.Clear();
+        MenuOperationsIntegral.DropDownItems.Clear();
+        MenuConvertEquation.DropDownItems.Clear();
+        MenuOperationsTranslate.DropDownItems.Clear();
 
         foreach (Graphable able in ables)
         {
@@ -360,7 +369,15 @@ public partial class GraphForm : Form
                 Text = able.Name
             };
             colorItem.Click += (o, e) => GraphColorPickerButton_Click(able);
-            MenuColors.DropDownItems.Add(colorItem);
+            MenuElementsColors.DropDownItems.Add(colorItem);
+
+            ToolStripMenuItem removeItem = new()
+            {
+                ForeColor = able.Color,
+                Text = able.Name
+            };
+            removeItem.Click += (o, e) => Ungraph(able);
+            MenuElementsRemove.DropDownItems.Add(removeItem);
 
             if (able is IDerivable derivable)
             {
@@ -370,7 +387,7 @@ public partial class GraphForm : Form
                     Text = able.Name
                 };
                 derivativeItem.Click += (o, e) => Graph(derivable.Derive());
-                MenuEquationsDerivative.DropDownItems.Add(derivativeItem);
+                MenuOperationsDerivative.DropDownItems.Add(derivativeItem);
             }
             if (able is IIntegrable integrable)
             {
@@ -380,20 +397,48 @@ public partial class GraphForm : Form
                     Text = able.Name
                 };
                 integralItem.Click += (o, e) => Graph(integrable.Integrate());
-                MenuEquationsIntegral.DropDownItems.Add(integralItem);
+                MenuOperationsIntegral.DropDownItems.Add(integralItem);
+            }
+            if (able is IEquationConvertible equConvert)
+            {
+                ToolStripMenuItem equItem = new()
+                {
+                    ForeColor = able.Color,
+                    Text = able.Name
+                };
+                equItem.Click += (o, e) =>
+                {
+                    Ungraph(able);
+                    Graph(equConvert.ToEquation());
+                };
+                MenuConvertEquation.DropDownItems.Add(equItem);
+            }
+            if (able is ITranslatable translatable)
+            {
+                ToolStripMenuItem transItem = new()
+                {
+                    ForeColor = able.Color,
+                    Text = able.Name
+                };
+                transItem.Click += (o, e) => ElementsOperationsTranslate_Click(able, translatable);
+                MenuOperationsTranslate.DropDownItems.Add(transItem);
             }
         }
     }
 
     private void ButtonViewportSetZoom_Click(object? sender, EventArgs e)
     {
-        SetZoomForm picker = new(this)
+        SetZoomForm zoomer = new(this)
         {
             StartPosition = FormStartPosition.Manual,
         };
-        picker.Location = new Point(Location.X + ClientRectangle.Width + 10,
-                                    Location.Y + (ClientRectangle.Height - picker.ClientRectangle.Height) / 2);
-        picker.ShowDialog();
+        zoomer.Location = new Point(Location.X + ClientRectangle.Width + 10,
+                                    Location.Y + (ClientRectangle.Height - zoomer.ClientRectangle.Height) / 2);
+        if (zoomer.Location.X + zoomer.Width > Screen.FromControl(this).WorkingArea.Width)
+        {
+            zoomer.StartPosition = FormStartPosition.WindowsDefaultLocation;
+        }
+        zoomer.ShowDialog();
     }
     private void ButtonViewportSetCenter_Click(object? sender, EventArgs e)
     {
@@ -446,4 +491,19 @@ public partial class GraphForm : Form
         foreach (Graphable able in Graphables) able.Preload(xRange, yRange, step);
         Invalidate(false);
     }
+
+    private void ElementsOperationsTranslate_Click(Graphable ableRaw, ITranslatable ableTrans)
+    {
+        TranslateForm shifter = new(this, ableRaw, ableTrans)
+        {
+            StartPosition = FormStartPosition.Manual,
+        };
+        shifter.Location = new Point(Location.X + ClientRectangle.Width + 10,
+                                     Location.Y + (ClientRectangle.Height - shifter.ClientRectangle.Height) / 2);
+        if (shifter.Location.X + shifter.Width > Screen.FromControl(this).WorkingArea.Width)
+        {
+            shifter.StartPosition = FormStartPosition.WindowsDefaultLocation;
+        }
+        shifter.ShowDialog();
+    }
 }

Base/Forms/TranslateForm.Designer.cs

@@ -0,0 +1,46 @@
+namespace Graphing.Forms
+{
+    partial class TranslateForm
+    {
+        /// <summary>
+        /// Required designer variable.
+        /// </summary>
+        private System.ComponentModel.IContainer components = null;
+
+        /// <summary>
+        /// Clean up any resources being used.
+        /// </summary>
+        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing && (components != null))
+            {
+                components.Dispose();
+            }
+            base.Dispose(disposing);
+        }
+
+        #region Windows Form Designer generated code
+
+        /// <summary>
+        /// Required method for Designer support - do not modify
+        /// the contents of this method with the code editor.
+        /// </summary>
+        private void InitializeComponent()
+        {
+            SuspendLayout();
+            // 
+            // TranslateForm
+            // 
+            AutoScaleDimensions = new System.Drawing.SizeF(13F, 32F);
+            AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
+            ClientSize = new System.Drawing.Size(674, 629);
+            FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedToolWindow;
+            Name = "TranslateForm";
+            Text = "TranslateForm";
+            ResumeLayout(false);
+        }
+
+        #endregion
+    }
+}

Base/Forms/TranslateForm.cs

@@ -0,0 +1,25 @@
+using Graphing.Abstract;
+using System.Windows.Forms;
+
+namespace Graphing.Forms;
+
+public partial class TranslateForm : Form
+{
+    private readonly GraphForm refForm;
+
+    // These variables both represent the same graphable.
+    private readonly Graphable ableRaw;
+    private readonly ITranslatable ableTrans;
+
+    public TranslateForm(GraphForm graph, Graphable ableRaw, ITranslatable ableTrans)
+    {
+        refForm = graph;
+        this.ableRaw = ableRaw;
+        this.ableTrans = ableTrans;
+
+        if (ableTrans is ITranslatableX transX) transX.OffsetX = 1;
+        if (ableTrans is ITranslatableY transY) transY.OffsetY = 1;
+
+        graph.Invalidate(false);
+    }
+}

Base/Forms/TranslateForm.resx

@@ -0,0 +1,120 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!--
+    Microsoft ResX Schema 
+
+    Version 2.0
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
+    associated with the data types.
+
+    Example:
+
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+
+    There are any number of "resheader" rows that contain simple
+    name/value pairs.
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
+    mimetype set.
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
+    extensible. For a given mimetype the value must be set accordingly:
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
+    read any of the formats listed below.
+
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+</root>

Base/Graphables/Equation.cs

@@ -6,13 +6,18 @@ using System.Collections.Generic;
 
 namespace Graphing.Graphables;
 
-public class Equation : Graphable, IIntegrable, IDerivable
+public class Equation : Graphable, IIntegrable, IDerivable, ITranslatableXY
 {
     private static int equationNum;
 
+    public double OffsetX { get; set; }
+    public double OffsetY { get; set; }
+
     protected readonly EquationDelegate equ;
     protected readonly List<Float2> cache;
 
+    public event Action<GraphForm> OnInvalidate;
+
     public Equation(EquationDelegate equ)
     {
         equationNum++;
@@ -20,6 +25,11 @@ public class Equation : Graphable, IIntegrable, IDerivable
 
         this.equ = equ;
         cache = [];
+
+        OffsetX = 0;
+        OffsetY = 0;
+
+        OnInvalidate = delegate { };
     }
 
     public override IEnumerable<IGraphPart> GetItemsToRender(in GraphForm graph)
@@ -46,6 +56,7 @@ public class Equation : Graphable, IIntegrable, IDerivable
             previousX = currentX;
             previousY = currentY;
         }
+        OnInvalidate.Invoke(graph);
         return lines;
     }
 
@@ -61,16 +72,18 @@ public class Equation : Graphable, IIntegrable, IDerivable
     public override void EraseCache() => cache.Clear();
     protected double GetFromCache(double x, double epsilon)
     {
-        (double dist, double nearest, int index) = NearestCachedPoint(x);
-        if (dist < epsilon) return nearest;
+        (double dist, double nearest, int index) = NearestCachedPoint(x - OffsetX);
+        if (dist < epsilon) return nearest + OffsetY;
         else
         {
-            double result = equ(x);
-            cache.Insert(index + 1, new(x, result));
-            return result;
+            double result = equ(x - OffsetX);
+            cache.Insert(index + 1, new(x - OffsetX, result));
+            return result + OffsetY;
         }
     }
 
+    public double GetValueAt(double x) => GetFromCache(x, 0);
+
     protected (double dist, double y, int index) NearestCachedPoint(double x)
     {
         if (cache.Count == 0) return (double.PositiveInfinity, double.NaN, -1);

Base/Graphables/TangentLine.cs

@@ -1,11 +1,12 @@
-using Graphing.Forms;
+using Graphing.Abstract;
+using Graphing.Forms;
 using Graphing.Parts;
 using System;
 using System.Collections.Generic;
 
 namespace Graphing.Graphables;
 
-public class TangentLine : Graphable
+public class TangentLine : Graphable, IEquationConvertible, ITranslatableX
 {
     public double Position
     {
@@ -18,8 +19,13 @@ public class TangentLine : Graphable
     }
     private double _position; // Private because it has exactly the same functionality as `Position`.
 
+    public double OffsetX
+    {
+        get => Position;
+        set => Position = value;
+    }
+
     protected readonly Equation parent;
-    protected readonly EquationDelegate parentEqu;
 
     protected readonly double length;
 
@@ -35,10 +41,16 @@ public class TangentLine : Graphable
         Name = $"Tangent Line of {parent.Name}";
 
         slopeCache = [];
-        parentEqu = parent.GetDelegate();
-        Position = position;
         this.length = length;
         this.parent = parent;
+        Position = position;
+
+        parent.OnInvalidate += (graph) =>
+        {
+            // I don't love this but it works.
+            EraseCache();
+            Position = _position; // Done for side effects.
+        };
     }
 
     public override IEnumerable<IGraphPart> GetItemsToRender(in GraphForm graph)
@@ -63,8 +75,8 @@ public class TangentLine : Graphable
 
         const double step = 1e-3;
 
-        double initial = parentEqu(x);
-        Float2 result = new((parentEqu(x + step) - initial) / step, initial);
+        double initial = parent.GetValueAt(x);
+        Float2 result = new((parent.GetValueAt(x + step) - initial) / step, initial);
         slopeCache.Add(x, result);
         return result;
     }
@@ -112,4 +124,14 @@ public class TangentLine : Graphable
         // that can be changed.
         for (double x = xRange.x; x <= xRange.y; x += step) DerivativeAtPoint(x);
     }
+
+    public Equation ToEquation()
+    {
+        double slope = currentSlope.x, x1 = Position, y1 = currentSlope.y;
+        return new(x => slope * (x - x1) + y1)
+        {
+            Name = Name,
+            Color = Color
+        };
+    }
 }

Base/Properties/PublishProfiles/FolderProfile.pubxml.user

@@ -4,7 +4,7 @@ https://go.microsoft.com/fwlink/?LinkID=208121.
 -->
 <Project>
   <PropertyGroup>
-    <History>True|2024-03-20T12:39:01.6402921Z;True|2024-03-13T10:31:43.4569441-04:00;False|2024-03-13T10:30:01.4347009-04:00;False|2024-03-13T10:27:31.9554551-04:00;</History>
+    <History>True|2024-03-20T12:48:45.8740885Z;True|2024-03-20T08:48:35.6948867-04:00;True|2024-03-20T08:39:01.6402921-04:00;True|2024-03-13T10:31:43.4569441-04:00;False|2024-03-13T10:30:01.4347009-04:00;False|2024-03-13T10:27:31.9554551-04:00;</History>
     <LastFailureDetails />
   </PropertyGroup>
 </Project>