Refactors CheckBox to use an enum instead of bool? for state. Cleans up naming to make more correct too (Toggle v. Toggled and State vs. Checked).

Terminal.Gui/Drawing/Glyphs.cs

@@ -32,13 +32,13 @@ public class GlyphDefinitions
     #region ----------------- Single Glyphs -----------------
 
     /// <summary>Checked indicator (e.g. for <see cref="ListView"/> and <see cref="CheckBox"/>).</summary>
-    public Rune Checked { get; set; } = (Rune)'☑';
+    public Rune CheckStateChecked { get; set; } = (Rune)'☑';
 
     /// <summary>Not Checked indicator (e.g. for <see cref="ListView"/> and <see cref="CheckBox"/>).</summary>
-    public Rune UnChecked { get; set; } = (Rune)'☐';
+    public Rune CheckStateUnChecked { get; set; } = (Rune)'☐';
 
     /// <summary>Null Checked indicator (e.g. for <see cref="ListView"/> and <see cref="CheckBox"/>).</summary>
-    public Rune NullChecked { get; set; } = (Rune)'☒';
+    public Rune CheckStateNone { get; set; } = (Rune)'☒';
 
     /// <summary>Selected indicator  (e.g. for <see cref="ListView"/> and <see cref="RadioGroup"/>).</summary>
     public Rune Selected { get; set; } = (Rune)'◉';

Terminal.Gui/Views/CheckBox.cs

@@ -1,23 +1,33 @@
 #nullable enable
 namespace Terminal.Gui;
 
-/// <summary>The <see cref="CheckBox"/> <see cref="View"/> shows an on/off toggle that the user can set</summary>
+/// <summary>
+///     Represents the state of a <see cref="CheckBox"/>.
+/// </summary>
+public enum CheckState
+{
+    None,
+    Checked,
+    UnChecked
+}
+
+/// <summary>Shows a check box that can be toggled.</summary>
 public class CheckBox : View
 {
     private readonly Rune _charChecked;
-    private readonly Rune _charNullChecked;
+    private readonly Rune _charNone;
     private readonly Rune _charUnChecked;
-    private bool _allowNullChecked;
-    private bool? _checked = false;
+    private bool _allowNone;
+    private CheckState _checked = CheckState.UnChecked;
 
     /// <summary>
     ///     Initializes a new instance of <see cref="CheckBox"/>.
     /// </summary>
     public CheckBox ()
     {
-        _charNullChecked = Glyphs.NullChecked;
-        _charChecked = Glyphs.Checked;
-        _charUnChecked = Glyphs.UnChecked;
+        _charNone = Glyphs.CheckStateNone;
+        _charChecked = Glyphs.CheckStateChecked;
+        _charUnChecked = Glyphs.CheckStateUnChecked;
 
         Width = Dim.Auto (DimAutoStyle.Text);
         Height = Dim.Auto (DimAutoStyle.Text, minimumContentDim: 1);
@@ -63,16 +73,23 @@ public class CheckBox : View
     }
 
     /// <summary>
-    ///     If <see langword="true"/> allows <see cref="Checked"/> to be null, true, or false. If <see langword="false"/>
-    ///     only allows <see cref="Checked"/> to be true or false.
+    ///     If <see langword="true"/> allows <see cref="State"/> to be <see cref="CheckState.None"/>.
     /// </summary>
-    public bool AllowNullChecked
+    public bool AllowCheckStateNone
     {
-        get => _allowNullChecked;
+        get => _allowNone;
         set
         {
-            _allowNullChecked = value;
-            Checked ??= false;
+            if (_allowNone == value)
+            {
+                return;
+            }
+            _allowNone = value;
+
+            if (State == CheckState.None)
+            {
+                State = CheckState.UnChecked;
+            }
         }
     }
 
@@ -81,24 +98,24 @@ public class CheckBox : View
     /// </summary>
     /// <remarks>
     ///     <para>
-    ///        If <see langword="null"/> and <see cref="AllowNullChecked"/> is <see langword="true"/>, the <see cref="CheckBox"/>
-    ///        will display the <c>ConfigurationManager.Glyphs.NullChecked</c> character (☒).
+    ///        If <see cref="AllowCheckStateNone"/> is <see langword="true"/> and <see cref="CheckState.None"/>, the <see cref="CheckBox"/>
+    ///        will display the <c>ConfigurationManager.Glyphs.CheckStateNone</c> character (☒).
     ///     </para>
     ///     <para>
-    ///        If <see langword="false"/>, the <see cref="CheckBox"/>
-    ///        will display the <c>ConfigurationManager.Glyphs.UnChecked</c> character (☐).
+    ///        If <see cref="CheckState.UnChecked"/>, the <see cref="CheckBox"/>
+    ///        will display the <c>ConfigurationManager.Glyphs.CheckStateUnChecked</c> character (☐).
     ///     </para>
     ///     <para>
-    ///        If <see langword="false"/>, the <see cref="CheckBox"/>
-    ///        will display the <c>ConfigurationManager.Glyphs.Checked</c> character (☑).
+    ///        If <see cref="CheckState.Checked"/>, the <see cref="CheckBox"/>
+    ///        will display the <c>ConfigurationManager.Glyphs.CheckStateChecked</c> character (☑).
     ///     </para>
     /// </remarks>
-    public bool? Checked
+    public CheckState State
     {
         get => _checked;
         set
         {
-            if (value is null && !AllowNullChecked)
+            if (_checked == value || (value is CheckState.None && !AllowCheckStateNone))
             {
                 return;
             }
@@ -109,36 +126,39 @@ public class CheckBox : View
         }
     }
 
-    /// <summary>Called when the <see cref="Checked"/> property changes. Invokes the cancelable <see cref="Toggle"/> event.</summary>
+    /// <summary>Called when the <see cref="State"/> property changes. Invokes the cancelable <see cref="Toggle"/> event.</summary>
     /// <remarks>
     /// </remarks>
     /// <returns>If <see langword="true"/> the <see cref="Toggle"/> event was canceled.</returns>
+    /// <remarks>
+    ///     Toggling cycles through the states <see cref="CheckState.None"/>, <see cref="CheckState.Checked"/>, and <see cref="CheckState.UnChecked"/>.
+    /// </remarks>
     public bool? OnToggle ()
     {
-        bool ? oldValue = Checked;
-        CancelEventArgs<bool?> e = new (ref _checked, ref oldValue);
+        CheckState oldValue = State;
+        CancelEventArgs<CheckState> e = new (ref _checked, ref oldValue);
 
-        if (AllowNullChecked)
+        switch (State)
         {
-            switch (Checked)
-            {
-                case null:
-                    e.NewValue = true;
+            case CheckState.None:
+                e.NewValue = CheckState.Checked;
 
-                    break;
-                case true:
-                    e.NewValue = false;
+                break;
+            case CheckState.Checked:
+                e.NewValue = CheckState.UnChecked;
 
-                    break;
-                case false:
-                    e.NewValue = null;
+                break;
+            case CheckState.UnChecked:
+                if (AllowCheckStateNone)
+                {
+                    e.NewValue = CheckState.None;
+                }
+                else
+                {
+                    e.NewValue = CheckState.Checked;
+                }
 
-                    break;
-            }
-        }
-        else
-        {
-            e.NewValue = !Checked;
+                break;
         }
 
         Toggle?.Invoke (this, e);
@@ -153,7 +173,7 @@ public class CheckBox : View
             return true;
         }
 
-        Checked = e.NewValue;
+        State = e.NewValue;
 
         return true;
     }
@@ -164,7 +184,7 @@ public class CheckBox : View
     ///    This event can be cancelled. If cancelled, the <see cref="CheckBox"/> will not change its state.
     /// </para>
     /// </remarks>
-    public event EventHandler<CancelEventArgs<bool?>>? Toggle;
+    public event EventHandler<CancelEventArgs<CheckState>>? Toggle;
 
     /// <inheritdoc/>
     protected override void UpdateTextFormatterText ()
@@ -186,11 +206,12 @@ public class CheckBox : View
 
     private Rune GetCheckedState ()
     {
-        return Checked switch
+        return State switch
         {
-            true => _charChecked,
-            false => _charUnChecked,
-            var _ => _charNullChecked
+            CheckState.Checked => _charChecked,
+            CheckState.UnChecked => _charUnChecked,
+            CheckState.None => _charNone,
+            _ => throw new ArgumentOutOfRangeException ()
         };
     }
 }

Terminal.Gui/Views/ComboBox.cs

@@ -929,8 +929,8 @@ public class ComboBox : View
                     if (AllowsMarking)
                     {
                         Driver.AddRune (
-                                        Source.IsMarked (item) ? AllowsMultipleSelection ? Glyphs.Checked : Glyphs.Selected :
-                                        AllowsMultipleSelection ? Glyphs.UnChecked : Glyphs.UnSelected
+                                        Source.IsMarked (item) ? AllowsMultipleSelection ? Glyphs.CheckStateChecked : Glyphs.Selected :
+                                        AllowsMultipleSelection ? Glyphs.CheckStateUnChecked : Glyphs.UnSelected
                                        );
                         Driver.AddRune ((Rune)' ');
                     }

Terminal.Gui/Views/ListView.cs

@@ -724,8 +724,8 @@ public class ListView : View
                 if (_allowsMarking)
                 {
                     Driver.AddRune (
-                                    _source.IsMarked (item) ? AllowsMultipleSelection ? Glyphs.Checked : Glyphs.Selected :
-                                    AllowsMultipleSelection ? Glyphs.UnChecked : Glyphs.UnSelected
+                                    _source.IsMarked (item) ? AllowsMultipleSelection ? Glyphs.CheckStateChecked : Glyphs.Selected :
+                                    AllowsMultipleSelection ? Glyphs.CheckStateUnChecked : Glyphs.UnSelected
                                    );
                     Driver.AddRune ((Rune)' ');
                 }

Terminal.Gui/Views/Menu/Menu.cs

@@ -447,14 +447,14 @@ internal sealed class Menu : View
             }
 
             string textToDraw = null;
-            Rune nullCheckedChar = Glyphs.NullChecked;
+            Rune nullCheckedChar = Glyphs.CheckStateNone;
             Rune checkChar = Glyphs.Selected;
             Rune uncheckedChar = Glyphs.UnSelected;
 
             if (item.CheckType.HasFlag (MenuItemCheckStyle.Checked))
             {
-                checkChar = Glyphs.Checked;
-                uncheckedChar = Glyphs.UnChecked;
+                checkChar = Glyphs.CheckStateChecked;
+                uncheckedChar = Glyphs.CheckStateUnChecked;
             }
 
             // Support Checked even though CheckType wasn't set

Terminal.Gui/Views/TableView/CheckBoxTableSourceWrapper.cs

@@ -33,9 +33,9 @@ public abstract class CheckBoxTableSourceWrapperBase : ITableSource
     }
 
     /// <summary>
-    ///     Gets or sets the character to use for checked entries. Defaults to <see cref="GlyphDefinitions.Checked"/>
+    ///     Gets or sets the character to use for checked entries. Defaults to <see cref="GlyphDefinitions.CheckStateChecked"/>
     /// </summary>
-    public Rune CheckedRune { get; set; } = Glyphs.Checked;
+    public Rune CheckedRune { get; set; } = Glyphs.CheckStateChecked;
 
     /// <summary>
     ///     Gets or sets the character to use for checked entry when <see cref="UseRadioButtons"/> is true. Defaults to
@@ -50,9 +50,9 @@ public abstract class CheckBoxTableSourceWrapperBase : ITableSource
     public Rune RadioUnCheckedRune { get; set; } = Glyphs.UnSelected;
 
     /// <summary>
-    ///     Gets or sets the character to use for UnChecked entries. Defaults to <see cref="GlyphDefinitions.UnChecked"/>
+    ///     Gets or sets the character to use for UnChecked entries. Defaults to <see cref="GlyphDefinitions.CheckStateUnChecked"/>
     /// </summary>
-    public Rune UnCheckedRune { get; set; } = Glyphs.UnChecked;
+    public Rune UnCheckedRune { get; set; } = Glyphs.CheckStateUnChecked;
 
     /// <summary>Gets or sets whether to only allow a single row to be toggled at once (Radio button).</summary>
     public bool UseRadioButtons { get; set; }

UICatalog/Scenarios/AdornmentsEditor.cs

@@ -90,11 +90,11 @@ public class AdornmentsEditor : View
         Add (_paddingEditor);
 
         _diagPaddingCheckBox = new () { Text = "_Diagnostic Padding" };
-        _diagPaddingCheckBox.Checked = Diagnostics.FastHasFlags (ViewDiagnosticFlags.Padding);
+        _diagPaddingCheckBox.State = Diagnostics.FastHasFlags (ViewDiagnosticFlags.Padding) ? CheckState.Checked : CheckState.UnChecked;
 
         _diagPaddingCheckBox.Toggle += (s, e) =>
                                         {
-                                            if (e.NewValue == true)
+                                            if (e.NewValue == CheckState.Checked)
                                             {
                                                 Diagnostics |= ViewDiagnosticFlags.Padding;
                                             }
@@ -108,11 +108,11 @@ public class AdornmentsEditor : View
         _diagPaddingCheckBox.Y = Pos.Bottom (_paddingEditor);
 
         _diagRulerCheckBox = new () { Text = "_Diagnostic Ruler" };
-        _diagRulerCheckBox.Checked = Diagnostics.FastHasFlags (ViewDiagnosticFlags.Ruler);
+        _diagRulerCheckBox.State = Diagnostics.FastHasFlags(ViewDiagnosticFlags.Ruler) ? CheckState.Checked : CheckState.UnChecked;
 
         _diagRulerCheckBox.Toggle += (s, e) =>
                                       {
-                                          if (e.NewValue == true)
+                                          if (e.NewValue == CheckState.Checked)
                                           {
                                               Diagnostics |= ViewDiagnosticFlags.Ruler;
                                           }

UICatalog/Scenarios/BorderEditor.cs

@@ -20,7 +20,7 @@ public class BorderEditor : AdornmentEditor
 
     private void BorderEditor_AdornmentChanged (object sender, EventArgs e)
     {
-        _ckbTitle.Checked = ((Border)AdornmentToEdit).ShowTitle;
+        _ckbTitle.State = ((Border)AdornmentToEdit).ShowTitle ? CheckState.Checked : CheckState.UnChecked;
         _rbBorderStyle.SelectedItem = (int)((Border)AdornmentToEdit).LineStyle;
     }
 
@@ -51,7 +51,7 @@ public class BorderEditor : AdornmentEditor
             X = 0,
             Y = Pos.Bottom (_rbBorderStyle),
 
-            Checked = true,
+            State = CheckState.Checked,
             SuperViewRendersLineCanvas = true,
             Text = "Show Title",
             Enabled = AdornmentToEdit is { }
@@ -81,6 +81,6 @@ public class BorderEditor : AdornmentEditor
             LayoutSubviews ();
         }
 
-        void OnCkbTitleOnToggle (object sender, CancelEventArgs<bool?> args) { ((Border)AdornmentToEdit).ShowTitle = args.NewValue!.Value; }
+        void OnCkbTitleOnToggle (object sender, CancelEventArgs<CheckState> args) { ((Border)AdornmentToEdit).ShowTitle = args.NewValue == CheckState.Checked; }
     }
 }

UICatalog/Scenarios/Buttons.cs

@@ -385,7 +385,7 @@ public class Buttons : Scenario
             X = Pos.Right (repeatButton) + 1,
             Y = Pos.Top (repeatButton),
             Title = "Enabled",
-            Checked = true
+            State = CheckState.Checked
         };
         enableCB.Toggle += (s, e) => { repeatButton.Enabled = !repeatButton.Enabled; };
         main.Add (label, repeatButton, enableCB);

UICatalog/Scenarios/ContentScrolling.cs

@@ -135,12 +135,12 @@ public class ContentScrolling : Scenario
             Y = 0,
             CanFocus = false
         };
-        cbAllowNegativeX.Checked = view.ViewportSettings.HasFlag (ViewportSettings.AllowNegativeX);
+        cbAllowNegativeX.State = view.ViewportSettings.HasFlag(ViewportSettings.AllowNegativeX) ? CheckState.Checked : CheckState.UnChecked;
         cbAllowNegativeX.Toggle += AllowNegativeX_Toggle;
 
-        void AllowNegativeX_Toggle (object sender, CancelEventArgs<bool?> e)
+        void AllowNegativeX_Toggle (object sender, CancelEventArgs<CheckState> e)
         {
-            if (e.NewValue == true)
+            if (e.NewValue == CheckState.Checked)
             {
                 view.ViewportSettings |= ViewportSettings.AllowNegativeX;
             }
@@ -159,12 +159,12 @@ public class ContentScrolling : Scenario
             Y = 0,
             CanFocus = false
         };
-        cbAllowNegativeY.Checked = view.ViewportSettings.HasFlag (ViewportSettings.AllowNegativeY);
+        cbAllowNegativeY.State = view.ViewportSettings.HasFlag(ViewportSettings.AllowNegativeY) ? CheckState.Checked : CheckState.UnChecked;
         cbAllowNegativeY.Toggle += AllowNegativeY_Toggle;
 
-        void AllowNegativeY_Toggle (object sender, CancelEventArgs<bool?> e)
+        void AllowNegativeY_Toggle (object sender, CancelEventArgs<CheckState> e)
         {
-            if (e.NewValue == true)
+            if (e.NewValue == CheckState.Checked)
             {
                 view.ViewportSettings |= ViewportSettings.AllowNegativeY;
             }
@@ -182,12 +182,12 @@ public class ContentScrolling : Scenario
             Y = Pos.Bottom (cbAllowNegativeX),
             CanFocus = false
         };
-        cbAllowXGreaterThanContentWidth.Checked = view.ViewportSettings.HasFlag (ViewportSettings.AllowXGreaterThanContentWidth);
+        cbAllowXGreaterThanContentWidth.State = view.ViewportSettings.HasFlag(ViewportSettings.AllowXGreaterThanContentWidth) ? CheckState.Checked : CheckState.UnChecked;
         cbAllowXGreaterThanContentWidth.Toggle += AllowXGreaterThanContentWidth_Toggle;
 
-        void AllowXGreaterThanContentWidth_Toggle (object sender, CancelEventArgs<bool?> e)
+        void AllowXGreaterThanContentWidth_Toggle (object sender, CancelEventArgs<CheckState> e)
         {
-            if (e.NewValue == true)
+            if (e.NewValue == CheckState.Checked)
             {
                 view.ViewportSettings |= ViewportSettings.AllowXGreaterThanContentWidth;
             }
@@ -206,12 +206,12 @@ public class ContentScrolling : Scenario
             Y = Pos.Bottom (cbAllowNegativeX),
             CanFocus = false
         };
-        cbAllowYGreaterThanContentHeight.Checked = view.ViewportSettings.HasFlag (ViewportSettings.AllowYGreaterThanContentHeight);
+        cbAllowYGreaterThanContentHeight.State = view.ViewportSettings.HasFlag(ViewportSettings.AllowYGreaterThanContentHeight) ? CheckState.Checked : CheckState.UnChecked;
         cbAllowYGreaterThanContentHeight.Toggle += AllowYGreaterThanContentHeight_Toggle;
 
-        void AllowYGreaterThanContentHeight_Toggle (object sender, CancelEventArgs<bool?> e)
+        void AllowYGreaterThanContentHeight_Toggle (object sender, CancelEventArgs<CheckState> e)
         {
-            if (e.NewValue == true)
+            if (e.NewValue == CheckState.Checked)
             {
                 view.ViewportSettings |= ViewportSettings.AllowYGreaterThanContentHeight;
             }
@@ -284,12 +284,12 @@ public class ContentScrolling : Scenario
             Y = Pos.Top (labelContentSize),
             CanFocus = false
         };
-        cbClearOnlyVisible.Checked = view.ViewportSettings.HasFlag (ViewportSettings.ClearContentOnly);
+        cbClearOnlyVisible.State = view.ViewportSettings.HasFlag(ViewportSettings.ClearContentOnly) ? CheckState.Checked : CheckState.UnChecked;
         cbClearOnlyVisible.Toggle += ClearVisibleContentOnly_Toggle;
 
-        void ClearVisibleContentOnly_Toggle (object sender, CancelEventArgs<bool?> e)
+        void ClearVisibleContentOnly_Toggle (object sender, CancelEventArgs<CheckState> e)
         {
-            if (e.NewValue == true)
+            if (e.NewValue == CheckState.Checked)
             {
                 view.ViewportSettings |= ViewportSettings.ClearContentOnly;
             }
@@ -306,12 +306,12 @@ public class ContentScrolling : Scenario
             Y = Pos.Top (labelContentSize),
             CanFocus = false
         };
-        cbDoNotClipContent.Checked = view.ViewportSettings.HasFlag (ViewportSettings.ClipContentOnly);
+        cbDoNotClipContent.State = view.ViewportSettings.HasFlag (ViewportSettings.ClipContentOnly) ? CheckState.Checked : CheckState.UnChecked;
         cbDoNotClipContent.Toggle += ClipVisibleContentOnly_Toggle;
 
-        void ClipVisibleContentOnly_Toggle (object sender, CancelEventArgs<bool?> e)
+        void ClipVisibleContentOnly_Toggle (object sender, CancelEventArgs<CheckState> e)
         {
-            if (e.NewValue == true)
+            if (e.NewValue == CheckState.Checked)
             {
                 view.ViewportSettings |= ViewportSettings.ClipContentOnly;
             }

UICatalog/Scenarios/Dialogs.cs

@@ -131,7 +131,7 @@ public class Dialogs : Scenario
             Y = Pos.Bottom (numButtonsLabel),
             TextAlignment = Alignment.End,
             Text = $"_Add {char.ConvertFromUtf32 (CODE_POINT)} to button text to stress wide char support",
-            Checked = false
+            State = CheckState.UnChecked
         };
         frame.Add (glyphsNotWords);
 
@@ -230,7 +230,7 @@ public class Dialogs : Scenario
                 int buttonId = i;
                 Button button = null;
 
-                if (glyphsNotWords.Checked == true)
+                if (glyphsNotWords.State == CheckState.Checked)
                 {
                     buttonId = i;
 
@@ -281,7 +281,7 @@ public class Dialogs : Scenario
                               int buttonId = buttons.Count;
                               Button button;
 
-                              if (glyphsNotWords.Checked == true)
+                              if (glyphsNotWords.State == CheckState.Checked)
                               {
                                   button = new ()
                                   {

UICatalog/Scenarios/DynamicMenuBar.cs

@@ -142,7 +142,7 @@ public class DynamicMenuBar : Scenario
             {
                 X = Pos.Left (_lblTitle),
                 Y = Pos.Bottom (CkbIsTopLevel),
-                Checked = _menuItem == null ? !_hasParent : HasSubMenus (_menuItem),
+                State = (_menuItem == null ? !_hasParent : HasSubMenus (_menuItem)) ? CheckState.Checked : CheckState.UnChecked,
                 Text = "Has sub-menus"
             };
             Add (CkbSubMenu);
@@ -251,34 +251,34 @@ public class DynamicMenuBar : Scenario
 
             CkbIsTopLevel.Toggle += (s, e) =>
                                      {
-                                         if ((_menuItem != null && _menuItem.Parent != null && (bool)CkbIsTopLevel.Checked)
-                                             || (_menuItem == null && _hasParent && (bool)CkbIsTopLevel.Checked))
+                                         if ((_menuItem != null && _menuItem.Parent != null && CkbIsTopLevel.State == CheckState.Checked)
+                                             || (_menuItem == null && _hasParent && CkbIsTopLevel.State == CheckState.Checked))
                                          {
                                              MessageBox.ErrorQuery (
                                                                     "Invalid IsTopLevel",
                                                                     "Only menu bar can have top level menu item!",
                                                                     "Ok"
                                                                    );
-                                             CkbIsTopLevel.Checked = false;
+                                             CkbIsTopLevel.State = CheckState.UnChecked;
 
                                              return;
                                          }
 
-                                         if (CkbIsTopLevel.Checked == true)
+                                         if (CkbIsTopLevel.State == CheckState.Checked)
                                          {
-                                             CkbSubMenu.Checked = false;
+                                             CkbSubMenu.State = CheckState.UnChecked;
                                              CkbSubMenu.SetNeedsDisplay ();
                                              TextHelp.Enabled = true;
                                              TextAction.Enabled = true;
 
                                              TextShortcut.Enabled =
-                                                 CkbIsTopLevel.Checked == false && CkbSubMenu.Checked == false;
+                                                 CkbIsTopLevel.State == CheckState.UnChecked && CkbSubMenu.State == CheckState.UnChecked;
                                          }
                                          else
                                          {
                                              if ((_menuItem == null && !_hasParent) || _menuItem.Parent == null)
                                              {
-                                                 CkbSubMenu.Checked = true;
+                                                 CkbSubMenu.State = CheckState.Checked;
                                                  CkbSubMenu.SetNeedsDisplay ();
                                                  TextShortcut.Enabled = false;
                                              }
@@ -292,9 +292,9 @@ public class DynamicMenuBar : Scenario
 
             CkbSubMenu.Toggle += (s, e) =>
                                   {
-                                      if ((bool)CkbSubMenu.Checked)
+                                      if (e.NewValue == CheckState.Checked)
                                       {
-                                          CkbIsTopLevel.Checked = false;
+                                          CkbIsTopLevel.State = CheckState.UnChecked;
                                           CkbIsTopLevel.SetNeedsDisplay ();
                                           TextHelp.Text = "";
                                           TextHelp.Enabled = false;
@@ -307,7 +307,7 @@ public class DynamicMenuBar : Scenario
                                       {
                                           if (!_hasParent)
                                           {
-                                              CkbIsTopLevel.Checked = true;
+                                              CkbIsTopLevel.State = CheckState.Checked;
                                               CkbIsTopLevel.SetNeedsDisplay ();
                                               TextShortcut.Enabled = false;
                                           }
@@ -316,7 +316,7 @@ public class DynamicMenuBar : Scenario
                                           TextAction.Enabled = true;
 
                                           TextShortcut.Enabled =
-                                              CkbIsTopLevel.Checked == false && CkbSubMenu.Checked == false;
+                                              CkbIsTopLevel.State == CheckState.UnChecked && CkbSubMenu.State == CheckState.UnChecked;
                                       }
                                   };
 
@@ -324,7 +324,7 @@ public class DynamicMenuBar : Scenario
                                     {
                                         if (_menuItem != null)
                                         {
-                                            _menuItem.AllowNullChecked = (bool)CkbNullCheck.Checked;
+                                            _menuItem.AllowNullChecked = e.NewValue == CheckState.Checked;
                                         }
                                     };
 
@@ -394,14 +394,14 @@ public class DynamicMenuBar : Scenario
             TextAction.Text = menuItem != null && menuItem.Action != null
                                   ? GetTargetAction (menuItem.Action)
                                   : string.Empty;
-            CkbIsTopLevel.Checked = IsTopLevel (menuItem);
-            CkbSubMenu.Checked = HasSubMenus (menuItem);
-            CkbNullCheck.Checked = menuItem.AllowNullChecked;
-            TextHelp.Enabled = (bool)!CkbSubMenu.Checked;
-            TextAction.Enabled = (bool)!CkbSubMenu.Checked;
+            CkbIsTopLevel.State = IsTopLevel (menuItem) ? CheckState.Checked : CheckState.UnChecked;
+            CkbSubMenu.State = HasSubMenus (menuItem) ? CheckState.Checked : CheckState.UnChecked;
+            CkbNullCheck.State = menuItem.AllowNullChecked ? CheckState.Checked : CheckState.UnChecked;
+            TextHelp.Enabled = CkbSubMenu.State == CheckState.Checked;
+            TextAction.Enabled = CkbSubMenu.State == CheckState.Checked;
             RbChkStyle.SelectedItem = (int)(menuItem?.CheckType ?? MenuItemCheckStyle.NoCheck);
             TextShortcut.Text = menuItem?.ShortcutTag ?? "";
-            TextShortcut.Enabled = CkbIsTopLevel.Checked == false && CkbSubMenu.Checked == false;
+            TextShortcut.Enabled = CkbIsTopLevel.State == CheckState.UnChecked && CkbSubMenu.State == CheckState.UnChecked;
         }
 
         public DynamicMenuItem EnterMenuItem ()
@@ -414,9 +414,9 @@ public class DynamicMenuBar : Scenario
                 TextTitle.Text = m.Title;
                 TextHelp.Text = m.Help;
                 TextAction.Text = m.Action;
-                CkbIsTopLevel.Checked = false;
-                CkbSubMenu.Checked = !_hasParent;
-                CkbNullCheck.Checked = false;
+                CkbIsTopLevel.State = CheckState.UnChecked;
+                CkbSubMenu.State = !_hasParent ? CheckState.Checked : CheckState.UnChecked;
+                CkbNullCheck.State = CheckState.UnChecked;
                 TextHelp.Enabled = _hasParent;
                 TextAction.Enabled = _hasParent;
                 TextShortcut.Enabled = _hasParent;
@@ -466,13 +466,13 @@ public class DynamicMenuBar : Scenario
                     Title = TextTitle.Text,
                     Help = TextHelp.Text,
                     Action = TextAction.Text,
-                    IsTopLevel = CkbIsTopLevel?.Checked ?? false,
-                    HasSubMenu = CkbSubMenu?.Checked ?? false,
+                    IsTopLevel = CkbIsTopLevel?.State == CheckState.Checked,
+                    HasSubMenu = CkbSubMenu?.State == CheckState.UnChecked,
                     CheckStyle = RbChkStyle.SelectedItem == 0 ? MenuItemCheckStyle.NoCheck :
                                  RbChkStyle.SelectedItem == 1 ? MenuItemCheckStyle.Checked :
                                  MenuItemCheckStyle.Radio,
                     Shortcut = TextShortcut.Text,
-                    AllowNullChecked = CkbNullCheck.Checked != null && (bool)CkbNullCheck.Checked
+                    AllowNullChecked = CkbNullCheck?.State == CheckState.Checked,
                 };
             }
 
@@ -515,8 +515,8 @@ public class DynamicMenuBar : Scenario
             TextTitle.Text = "";
             TextHelp.Text = "";
             TextAction.Text = "";
-            CkbIsTopLevel.Checked = false;
-            CkbSubMenu.Checked = false;
+            CkbIsTopLevel.State = CheckState.UnChecked;
+            CkbSubMenu.State = CheckState.UnChecked;
             RbChkStyle.SelectedItem = (int)MenuItemCheckStyle.NoCheck;
             TextShortcut.Text = "";
         }
@@ -835,8 +835,8 @@ public class DynamicMenuBar : Scenario
                                          Title = _frmMenuDetails.TextTitle.Text,
                                          Help = _frmMenuDetails.TextHelp.Text,
                                          Action = _frmMenuDetails.TextAction.Text,
-                                         IsTopLevel = _frmMenuDetails.CkbIsTopLevel?.Checked ?? false,
-                                         HasSubMenu = _frmMenuDetails.CkbSubMenu?.Checked ?? false,
+                                         IsTopLevel = _frmMenuDetails.CkbIsTopLevel?.State == CheckState.UnChecked,
+                                         HasSubMenu = _frmMenuDetails.CkbSubMenu?.State == CheckState.UnChecked,
                                          CheckStyle = _frmMenuDetails.RbChkStyle.SelectedItem == 0
                                                           ? MenuItemCheckStyle.NoCheck
                                                           : _frmMenuDetails.RbChkStyle.SelectedItem == 1

UICatalog/Scenarios/Editor.cs

@@ -895,16 +895,16 @@ public class Editor : Scenario
 
         var ckbMatchCase = new CheckBox
         {
-            X = 0, Y = Pos.Top (txtToFind) + 2, Checked = _matchCase, Text = "Match c_ase"
+            X = 0, Y = Pos.Top (txtToFind) + 2, State = _matchCase ? CheckState.Checked : CheckState.UnChecked, Text = "Match c_ase"
         };
-        ckbMatchCase.Toggle += (s, e) => _matchCase = (bool)ckbMatchCase.Checked;
+        ckbMatchCase.Toggle += (s, e) => _matchCase = e.NewValue == CheckState.Checked;
         d.Add (ckbMatchCase);
 
         var ckbMatchWholeWord = new CheckBox
         {
-            X = 0, Y = Pos.Top (ckbMatchCase) + 1, Checked = _matchWholeWord, Text = "Match _whole word"
+            X = 0, Y = Pos.Top (ckbMatchCase) + 1, State = _matchWholeWord ? CheckState.Checked : CheckState.UnChecked, Text = "Match _whole word"
         };
-        ckbMatchWholeWord.Toggle += (s, e) => _matchWholeWord = (bool)ckbMatchWholeWord.Checked;
+        ckbMatchWholeWord.Toggle += (s, e) => _matchWholeWord = e.NewValue == CheckState.Checked;
         d.Add (ckbMatchWholeWord);
         return d;
     }
@@ -1153,16 +1153,16 @@ public class Editor : Scenario
 
         var ckbMatchCase = new CheckBox
         {
-            X = 0, Y = Pos.Top (txtToFind) + 2, Checked = _matchCase, Text = "Match c_ase"
+            X = 0, Y = Pos.Top (txtToFind) + 2, State = _matchCase ? CheckState.Checked : CheckState.UnChecked, Text = "Match c_ase"
         };
-        ckbMatchCase.Toggle += (s, e) => _matchCase = (bool)ckbMatchCase.Checked;
+        ckbMatchCase.Toggle += (s, e) => _matchCase = e.NewValue == CheckState.Checked;
         d.Add (ckbMatchCase);
 
         var ckbMatchWholeWord = new CheckBox
         {
-            X = 0, Y = Pos.Top (ckbMatchCase) + 1, Checked = _matchWholeWord, Text = "Match _whole word"
+            X = 0, Y = Pos.Top (ckbMatchCase) + 1, State = _matchWholeWord ? CheckState.Checked : CheckState.UnChecked, Text = "Match _whole word"
         };
-        ckbMatchWholeWord.Toggle += (s, e) => _matchWholeWord = (bool)ckbMatchWholeWord.Checked;
+        ckbMatchWholeWord.Toggle += (s, e) => _matchWholeWord = e.NewValue == CheckState.Checked;
         d.Add (ckbMatchWholeWord);
 
         return d;

UICatalog/Scenarios/FileDialogExamples.cs

@@ -31,25 +31,25 @@ public class FileDialogExamples : Scenario
         var y = 0;
         var x = 1;
 
-        _cbMustExist = new CheckBox { Checked = true, Y = y++, X = x, Text = "Must Exist" };
+        _cbMustExist = new CheckBox { State = CheckState.Checked, Y = y++, X = x, Text = "Must Exist" };
         Win.Add (_cbMustExist);
 
-        _cbUseColors = new CheckBox { Checked = FileDialogStyle.DefaultUseColors, Y = y++, X = x, Text = "Use Colors" };
+        _cbUseColors = new CheckBox { State = FileDialogStyle.DefaultUseColors ? CheckState.Checked : CheckState.UnChecked, Y = y++, X = x, Text = "Use Colors" };
         Win.Add (_cbUseColors);
 
-        _cbCaseSensitive = new CheckBox { Checked = false, Y = y++, X = x, Text = "Case Sensitive Search" };
+        _cbCaseSensitive = new CheckBox { State = CheckState.UnChecked, Y = y++, X = x, Text = "Case Sensitive Search" };
         Win.Add (_cbCaseSensitive);
 
-        _cbAllowMultipleSelection = new CheckBox { Checked = false, Y = y++, X = x, Text = "Multiple" };
+        _cbAllowMultipleSelection = new CheckBox { State = CheckState.UnChecked, Y = y++, X = x, Text = "Multiple" };
         Win.Add (_cbAllowMultipleSelection);
 
-        _cbShowTreeBranchLines = new CheckBox { Checked = true, Y = y++, X = x, Text = "Tree Branch Lines" };
+        _cbShowTreeBranchLines = new CheckBox { State = CheckState.Checked, Y = y++, X = x, Text = "Tree Branch Lines" };
         Win.Add (_cbShowTreeBranchLines);
 
-        _cbAlwaysTableShowHeaders = new CheckBox { Checked = true, Y = y++, X = x, Text = "Always Show Headers" };
+        _cbAlwaysTableShowHeaders = new CheckBox { State = CheckState.Checked, Y = y++, X = x, Text = "Always Show Headers" };
         Win.Add (_cbAlwaysTableShowHeaders);
 
-        _cbDrivesOnlyInTree = new CheckBox { Checked = false, Y = y++, X = x, Text = "Only Show Drives" };
+        _cbDrivesOnlyInTree = new CheckBox { State = CheckState.UnChecked, Y = y++, X = x, Text = "Only Show Drives" };
         Win.Add (_cbDrivesOnlyInTree);
 
         y = 0;
@@ -145,8 +145,8 @@ public class FileDialogExamples : Scenario
             OpenMode = Enum.Parse<OpenMode> (
                                              _rgOpenMode.RadioLabels [_rgOpenMode.SelectedItem]
                                             ),
-            MustExist = _cbMustExist.Checked ?? false,
-            AllowsMultipleSelection = _cbAllowMultipleSelection.Checked ?? false
+            MustExist = _cbMustExist.State == CheckState.Checked,
+            AllowsMultipleSelection = _cbAllowMultipleSelection.State == CheckState.Checked
         };
 
         fd.Style.OkButtonText = _rgCaption.RadioLabels [_rgCaption.SelectedItem];
@@ -160,19 +160,19 @@ public class FileDialogExamples : Scenario
         fd.Style.IconProvider.UseUnicodeCharacters = _rgIcons.SelectedItem == 1;
         fd.Style.IconProvider.UseNerdIcons = _rgIcons.SelectedItem == 2;
 
-        if (_cbCaseSensitive.Checked ?? false)
+        if (_cbCaseSensitive.State == CheckState.Checked)
         {
             fd.SearchMatcher = new CaseSensitiveSearchMatcher ();
         }
 
-        fd.Style.UseColors = _cbUseColors.Checked ?? false;
+        fd.Style.UseColors = _cbUseColors.State == CheckState.Checked;
 
-        fd.Style.TreeStyle.ShowBranchLines = _cbShowTreeBranchLines.Checked ?? false;
-        fd.Style.TableStyle.AlwaysShowHeaders = _cbAlwaysTableShowHeaders.Checked ?? false;
+        fd.Style.TreeStyle.ShowBranchLines = _cbShowTreeBranchLines.State == CheckState.Checked;
+        fd.Style.TableStyle.AlwaysShowHeaders = _cbAlwaysTableShowHeaders.State == CheckState.Checked;
 
         IDirectoryInfoFactory dirInfoFactory = new FileSystem ().DirectoryInfo;
 
-        if (_cbDrivesOnlyInTree.Checked ?? false)
+        if (_cbDrivesOnlyInTree.State == CheckState.Checked)
         {
             fd.Style.TreeRootGetter = () => { return Environment.GetLogicalDrives ().ToDictionary (dirInfoFactory.New, k => k); };
         }
@@ -197,7 +197,7 @@ public class FileDialogExamples : Scenario
             fd.Style.CancelButtonText = _tbCancelButton.Text;
         }
 
-        if (_cbFlipButtonOrder.Checked ?? false)
+        if (_cbFlipButtonOrder.State == CheckState.Checked)
         {
             fd.Style.FlipOkCancelButtonLayoutOrder = true;
         }
@@ -219,7 +219,7 @@ public class FileDialogExamples : Scenario
                               "Ok"
                              );
         }
-        else if (_cbAllowMultipleSelection.Checked ?? false)
+        else if (_cbAllowMultipleSelection.State == CheckState.Checked)
         {
             MessageBox.Query (
                               "Chosen!",

UICatalog/Scenarios/GraphViewExample.cs

@@ -202,7 +202,7 @@ public class GraphViewExample : Scenario
 
         if (sender is Shortcut shortcut && shortcut.CommandView is CheckBox checkBox)
         {
-            checkBox.Checked = _miDiags.Checked;
+            checkBox.State = _miDiags.Checked ?? false ? CheckState.Checked : CheckState.UnChecked;
         }
     }
 

UICatalog/Scenarios/Images.cs

@@ -28,7 +28,7 @@ public class Images : Scenario
         {
             X = Pos.Right (lblDriverName) + 2,
             Y = 0,
-            Checked = canTrueColor,
+            State = canTrueColor ? CheckState.Checked : CheckState.UnChecked,
             CanFocus = false,
             Text = "supports true color "
         };
@@ -38,11 +38,11 @@ public class Images : Scenario
         {
             X = Pos.Right (cbSupportsTrueColor) + 2,
             Y = 0,
-            Checked = !Application.Force16Colors,
+            State = !Application.Force16Colors ? CheckState.Checked : CheckState.UnChecked,
             Enabled = canTrueColor,
             Text = "Use true color"
         };
-        cbUseTrueColor.Toggle += (_, evt) => Application.Force16Colors = !evt.NewValue ?? false;
+        cbUseTrueColor.Toggle += (_, evt) => Application.Force16Colors = evt.NewValue == CheckState.UnChecked;
         Win.Add (cbUseTrueColor);
 
         var btnOpenImage = new Button { X = Pos.Right (cbUseTrueColor) + 2, Y = 0, Text = "Open Image" };

UICatalog/Scenarios/ListViewWithSelection.cs

@@ -38,7 +38,7 @@ public class ListViewWithSelection : Scenario
 
         _allowMarkingCB = new CheckBox
         {
-            X = Pos.Right (_customRenderCB) + 1, Y = 0, Text = "Allow Marking", AllowNullChecked = false
+            X = Pos.Right (_customRenderCB) + 1, Y = 0, Text = "Allow Marking", AllowCheckStateNone = false
         };
         _appWindow.Add (_allowMarkingCB);
         _allowMarkingCB.Toggle += AllowMarkingCB_Toggle;
@@ -47,7 +47,7 @@ public class ListViewWithSelection : Scenario
         {
             X = Pos.Right (_allowMarkingCB) + 1,
             Y = 0,
-            Visible = (bool)_allowMarkingCB.Checked,
+            Visible = _allowMarkingCB.State == CheckState.Checked,
             Text = "Allow Multi-Select"
         };
         _appWindow.Add (_allowMultipleCB);
@@ -108,9 +108,9 @@ public class ListViewWithSelection : Scenario
 
         var keepCheckBox = new CheckBox
         {
-            X = Pos.AnchorEnd (k.Length + 3), Y = 0, Text = k, Checked = scrollBar.AutoHideScrollBars
+            X = Pos.AnchorEnd (k.Length + 3), Y = 0, Text = k, State = scrollBar.AutoHideScrollBars ? CheckState.Checked : CheckState.UnChecked
         };
-        keepCheckBox.Toggle += (s, e) => scrollBar.KeepContentAlwaysInViewport = (bool)keepCheckBox.Checked;
+        keepCheckBox.Toggle += (s, e) => scrollBar.KeepContentAlwaysInViewport = e.NewValue == CheckState.Checked;
         _appWindow.Add (keepCheckBox);
 
         Application.Run (_appWindow);
@@ -118,9 +118,9 @@ public class ListViewWithSelection : Scenario
         Application.Shutdown ();
     }
 
-    private void _customRenderCB_Toggle (object sender, CancelEventArgs<bool?> stateEventArgs)
+    private void _customRenderCB_Toggle (object sender, CancelEventArgs<CheckState> stateEventArgs)
     {
-        if (stateEventArgs.CurrentValue == true)
+        if (stateEventArgs.CurrentValue == CheckState.Checked)
         {
             _listView.SetSource (_scenarios);
         }
@@ -132,16 +132,16 @@ public class ListViewWithSelection : Scenario
         _appWindow.SetNeedsDisplay ();
     }
 
-    private void AllowMarkingCB_Toggle (object sender, [NotNull] CancelEventArgs<bool?> stateEventArgs)
+    private void AllowMarkingCB_Toggle (object sender, [NotNull] CancelEventArgs<CheckState> stateEventArgs)
     {
-        _listView.AllowsMarking = (bool)!stateEventArgs.CurrentValue;
+        _listView.AllowsMarking = stateEventArgs.NewValue == CheckState.Checked;
         _allowMultipleCB.Visible = _listView.AllowsMarking;
         _appWindow.SetNeedsDisplay ();
     }
 
-    private void AllowMultipleCB_Toggle (object sender, [NotNull] CancelEventArgs<bool?> stateEventArgs)
+    private void AllowMultipleCB_Toggle (object sender, [NotNull] CancelEventArgs<CheckState> stateEventArgs)
     {
-        _listView.AllowsMultipleSelection = (bool)!stateEventArgs.CurrentValue;
+        _listView.AllowsMultipleSelection = stateEventArgs.NewValue == CheckState.Checked;
         _appWindow.SetNeedsDisplay ();
     }
 

UICatalog/Scenarios/Localization.cs

@@ -141,7 +141,7 @@ public class Localization : Scenario
         {
             X = Pos.Right (textField) + 1,
             Y = Pos.Bottom (textAndFileDialogLabel) + 1,
-            Checked = false,
+            State = CheckState.UnChecked,
             Text = "Allow any"
         };
         Win.Add (_allowAnyCheckBox);
@@ -183,7 +183,7 @@ public class Localization : Scenario
 
         dialog.AllowedTypes =
         [
-            _allowAnyCheckBox.Checked ?? false
+            _allowAnyCheckBox.State == CheckState.Checked
                 ? new AllowedTypeAny ()
                 : new AllowedType ("Dynamic link library", ".dll"),
             new AllowedType ("Json", ".json"),

UICatalog/Scenarios/MessageBoxes.cs

@@ -186,7 +186,7 @@ public class MessageBoxes : Scenario
 
         var ckbWrapMessage = new CheckBox
         {
-            X = Pos.Right (label) + 1, Y = Pos.Bottom (styleRadioGroup), Text = "_Wrap Message", Checked = true
+            X = Pos.Right (label) + 1, Y = Pos.Bottom (styleRadioGroup), Text = "_Wrap Message", State = CheckState.Checked
         };
         frame.Add (ckbWrapMessage);
 
@@ -237,7 +237,7 @@ public class MessageBoxes : Scenario
                                                                              titleEdit.Text,
                                                                              messageEdit.Text,
                                                                              defaultButton,
-                                                                             (bool)ckbWrapMessage.Checked,
+                                                                             ckbWrapMessage.State == CheckState.Checked,
                                                                              btns.ToArray ()
                                                                             )}";
                                                }
@@ -250,7 +250,7 @@ public class MessageBoxes : Scenario
                                                                                   titleEdit.Text,
                                                                                   messageEdit.Text,
                                                                                   defaultButton,
-                                                                                  (bool)ckbWrapMessage.Checked,
+                                                                                  ckbWrapMessage.State == CheckState.Checked,
                                                                                   btns.ToArray ()
                                                                                  )}";
                                                }

UICatalog/Scenarios/Mouse.cs

@@ -77,11 +77,11 @@ public class Mouse : Scenario
             Y = Pos.Bottom (cbWantContinuousPresses),
             Title = "_Highlight on Press"
         };
-        cbHighlightOnPress.Checked = win.HighlightStyle == (HighlightStyle.Pressed | HighlightStyle.PressedOutside);
+        cbHighlightOnPress.State = win.HighlightStyle == (HighlightStyle.Pressed | HighlightStyle.PressedOutside) ? CheckState.Checked : CheckState.UnChecked;
 
         cbHighlightOnPress.Toggle += (s, e) =>
                                       {
-                                          if (e.NewValue == true)
+                                          if (e.NewValue == CheckState.Checked)
                                           {
                                               win.HighlightStyle = HighlightStyle.Pressed | HighlightStyle.PressedOutside;
                                           }

UICatalog/Scenarios/PosAlignDemo.cs

@@ -87,13 +87,13 @@ public sealed class PosAlignDemo : Scenario
 
         if (dimension == Dimension.Width)
         {
-            endToStartCheckBox.Checked = _horizAligner.AlignmentModes.HasFlag (AlignmentModes.EndToStart);
+            endToStartCheckBox.State = _horizAligner.AlignmentModes.HasFlag (AlignmentModes.EndToStart) ? CheckState.Checked : CheckState.UnChecked;
             endToStartCheckBox.X = Pos.Align (_horizAligner.Alignment);
             endToStartCheckBox.Y = Pos.Top (alignRadioGroup);
         }
         else
         {
-            endToStartCheckBox.Checked = _vertAligner.AlignmentModes.HasFlag (AlignmentModes.EndToStart);
+            endToStartCheckBox.State = _vertAligner.AlignmentModes.HasFlag (AlignmentModes.EndToStart) ? CheckState.Checked : CheckState.UnChecked;
             endToStartCheckBox.X = Pos.Left (alignRadioGroup);
             endToStartCheckBox.Y = Pos.Align (_vertAligner.Alignment);
         }
@@ -102,18 +102,16 @@ public sealed class PosAlignDemo : Scenario
                                       {
                                           if (dimension == Dimension.Width)
                                           {
-                                              _horizAligner.AlignmentModes =
-                                                  e.NewValue is { } && e.NewValue.Value
-                                                      ? _horizAligner.AlignmentModes | AlignmentModes.EndToStart
-                                                      : _horizAligner.AlignmentModes & ~AlignmentModes.EndToStart;
+                                              _horizAligner.AlignmentModes = e.NewValue == CheckState.Checked
+                                                                                 ? _horizAligner.AlignmentModes | AlignmentModes.EndToStart
+                                                                                 : _horizAligner.AlignmentModes & ~AlignmentModes.EndToStart;
                                               UpdatePosAlignObjects (appWindow, dimension, _horizAligner);
                                           }
                                           else
                                           {
-                                              _vertAligner.AlignmentModes =
-                                                  e.NewValue is { } && e.NewValue.Value
-                                                      ? _vertAligner.AlignmentModes | AlignmentModes.EndToStart
-                                                      : _vertAligner.AlignmentModes & ~AlignmentModes.EndToStart;
+                                              _vertAligner.AlignmentModes = e.NewValue == CheckState.Checked
+                                                                                ? _vertAligner.AlignmentModes | AlignmentModes.EndToStart
+                                                                                : _vertAligner.AlignmentModes & ~AlignmentModes.EndToStart;
                                               UpdatePosAlignObjects (appWindow, dimension, _vertAligner);
                                           }
                                       };
@@ -127,13 +125,13 @@ public sealed class PosAlignDemo : Scenario
 
         if (dimension == Dimension.Width)
         {
-            ignoreFirstOrLast.Checked = _horizAligner.AlignmentModes.HasFlag (AlignmentModes.IgnoreFirstOrLast);
+            ignoreFirstOrLast.State = _horizAligner.AlignmentModes.HasFlag (AlignmentModes.IgnoreFirstOrLast) ? CheckState.Checked : CheckState.UnChecked;
             ignoreFirstOrLast.X = Pos.Align (_horizAligner.Alignment);
             ignoreFirstOrLast.Y = Pos.Top (alignRadioGroup);
         }
         else
         {
-            ignoreFirstOrLast.Checked = _vertAligner.AlignmentModes.HasFlag (AlignmentModes.IgnoreFirstOrLast);
+            ignoreFirstOrLast.State = _vertAligner.AlignmentModes.HasFlag (AlignmentModes.IgnoreFirstOrLast) ? CheckState.Checked : CheckState.UnChecked;
             ignoreFirstOrLast.X = Pos.Left (alignRadioGroup);
             ignoreFirstOrLast.Y = Pos.Align (_vertAligner.Alignment);
         }
@@ -142,18 +140,16 @@ public sealed class PosAlignDemo : Scenario
                                      {
                                          if (dimension == Dimension.Width)
                                          {
-                                             _horizAligner.AlignmentModes =
-                                                 e.NewValue is { } && e.NewValue.Value
+                                             _horizAligner.AlignmentModes = e.NewValue == CheckState.Checked
                                                      ? _horizAligner.AlignmentModes | AlignmentModes.IgnoreFirstOrLast
                                                      : _horizAligner.AlignmentModes & ~AlignmentModes.IgnoreFirstOrLast;
                                              UpdatePosAlignObjects (appWindow, dimension, _horizAligner);
                                          }
                                          else
                                          {
-                                             _vertAligner.AlignmentModes =
-                                                 e.NewValue is { } && e.NewValue.Value
-                                                     ? _vertAligner.AlignmentModes | AlignmentModes.IgnoreFirstOrLast
-                                                     : _vertAligner.AlignmentModes & ~AlignmentModes.IgnoreFirstOrLast;
+                                             _vertAligner.AlignmentModes = e.NewValue == CheckState.Checked
+                                                                               ? _vertAligner.AlignmentModes | AlignmentModes.IgnoreFirstOrLast
+                                                                               : _vertAligner.AlignmentModes & ~AlignmentModes.IgnoreFirstOrLast;
                                              UpdatePosAlignObjects (appWindow, dimension, _vertAligner);
                                          }
                                      };
@@ -167,13 +163,13 @@ public sealed class PosAlignDemo : Scenario
 
         if (dimension == Dimension.Width)
         {
-            addSpacesBetweenItems.Checked = _horizAligner.AlignmentModes.HasFlag (AlignmentModes.AddSpaceBetweenItems);
+            addSpacesBetweenItems.State = _horizAligner.AlignmentModes.HasFlag (AlignmentModes.AddSpaceBetweenItems) ? CheckState.Checked : CheckState.UnChecked;
             addSpacesBetweenItems.X = Pos.Align (_horizAligner.Alignment);
             addSpacesBetweenItems.Y = Pos.Top (alignRadioGroup);
         }
         else
         {
-            addSpacesBetweenItems.Checked = _vertAligner.AlignmentModes.HasFlag (AlignmentModes.AddSpaceBetweenItems);
+            addSpacesBetweenItems.State = _vertAligner.AlignmentModes.HasFlag (AlignmentModes.AddSpaceBetweenItems) ? CheckState.Checked : CheckState.UnChecked;
             addSpacesBetweenItems.X = Pos.Left (alignRadioGroup);
             addSpacesBetweenItems.Y = Pos.Align (_vertAligner.Alignment);
         }
@@ -182,18 +178,16 @@ public sealed class PosAlignDemo : Scenario
                                          {
                                              if (dimension == Dimension.Width)
                                              {
-                                                 _horizAligner.AlignmentModes =
-                                                     e.NewValue is { } && e.NewValue.Value
-                                                         ? _horizAligner.AlignmentModes | AlignmentModes.AddSpaceBetweenItems
-                                                         : _horizAligner.AlignmentModes & ~AlignmentModes.AddSpaceBetweenItems;
+                                                 _horizAligner.AlignmentModes = e.NewValue == CheckState.Checked
+                                                                                    ? _horizAligner.AlignmentModes | AlignmentModes.AddSpaceBetweenItems
+                                                                                    : _horizAligner.AlignmentModes & ~AlignmentModes.AddSpaceBetweenItems;
                                                  UpdatePosAlignObjects (appWindow, dimension, _horizAligner);
                                              }
                                              else
                                              {
-                                                 _vertAligner.AlignmentModes =
-                                                     e.NewValue is { } && e.NewValue.Value
-                                                         ? _vertAligner.AlignmentModes | AlignmentModes.AddSpaceBetweenItems
-                                                         : _vertAligner.AlignmentModes & ~AlignmentModes.AddSpaceBetweenItems;
+                                                 _vertAligner.AlignmentModes = e.NewValue == CheckState.Checked
+                                                                                   ? _vertAligner.AlignmentModes | AlignmentModes.AddSpaceBetweenItems
+                                                                                   : _vertAligner.AlignmentModes & ~AlignmentModes.AddSpaceBetweenItems;
                                                  UpdatePosAlignObjects (appWindow, dimension, _vertAligner);
                                              }
                                          };
@@ -221,12 +215,12 @@ public sealed class PosAlignDemo : Scenario
                           {
                               if (dimension == Dimension.Width)
                               {
-                                  _leftMargin = e.NewValue is { } && e.NewValue.Value ? 1 : 0;
+                                  _leftMargin = e.NewValue == CheckState.Checked ? 1 : 0;
                                   UpdatePosAlignObjects (appWindow, dimension, _horizAligner);
                               }
                               else
                               {
-                                  _topMargin = e.NewValue is { } && e.NewValue.Value ? 1 : 0;
+                                  _topMargin = e.NewValue == CheckState.Checked ? 1 : 0;
                                   UpdatePosAlignObjects (appWindow, dimension, _vertAligner);
                               }
                           };

UICatalog/Scenarios/ProgressBarStyles.cs

@@ -233,7 +233,7 @@ public class ProgressBarStyles : Scenario
 
         var ckbBidirectional = new CheckBox
         {
-            X = Pos.Center (), Y = Pos.Bottom (continuousPB) + 1, Text = "BidirectionalMarquee", Checked = true
+            X = Pos.Center (), Y = Pos.Bottom (continuousPB) + 1, Text = "BidirectionalMarquee", State = CheckState.Checked
         };
         container.Add (ckbBidirectional);
 
@@ -276,7 +276,7 @@ public class ProgressBarStyles : Scenario
                                                                                             && v.Title == (string)e.Value
                                                                                        );
                                       };
-        
+
 
         rbPBFormat.SelectedItemChanged += (s, e) =>
                                           {
@@ -287,10 +287,11 @@ public class ProgressBarStyles : Scenario
                                           };
 
         ckbBidirectional.Toggle += (s, e) =>
-                                    {
-                                        ckbBidirectional.Checked = marqueesBlocksPB.BidirectionalMarquee =
-                                                                       marqueesContinuousPB.BidirectionalMarquee = (bool)!e.CurrentValue;
-                                    };
+                                   {
+                                       ckbBidirectional.State = e.CurrentValue;
+                                       marqueesBlocksPB.BidirectionalMarquee =
+                                                                  marqueesContinuousPB.BidirectionalMarquee = e.CurrentValue == CheckState.Checked;
+                                   };
 
 
 

UICatalog/Scenarios/Scrolling.cs

@@ -148,7 +148,7 @@ public class Scrolling : Scenario
             X = Pos.X (scrollView),
             Y = Pos.Bottom (scrollView),
             Text = "Horizontal Scrollbar",
-            Checked = scrollView.ShowHorizontalScrollIndicator
+            State = scrollView.ShowHorizontalScrollIndicator ? CheckState.Checked : CheckState.UnChecked
         };
         app.Add (hCheckBox);
 
@@ -157,7 +157,7 @@ public class Scrolling : Scenario
             X = Pos.Right (hCheckBox) + 3,
             Y = Pos.Bottom (scrollView),
             Text = "Vertical Scrollbar",
-            Checked = scrollView.ShowVerticalScrollIndicator
+            State = scrollView.ShowVerticalScrollIndicator ? CheckState.Checked : CheckState.UnChecked
         };
         app.Add (vCheckBox);
 
@@ -165,50 +165,50 @@ public class Scrolling : Scenario
 
         var ahCheckBox = new CheckBox
         {
-            X = Pos.Left (scrollView), Y = Pos.Bottom (hCheckBox), Text = t, Checked = scrollView.AutoHideScrollBars
+            X = Pos.Left (scrollView), Y = Pos.Bottom (hCheckBox), Text = t, State = scrollView.AutoHideScrollBars ? CheckState.Checked : CheckState.UnChecked
         };
         var k = "Keep Content Always In Viewport";
 
         var keepCheckBox = new CheckBox
         {
-            X = Pos.Left (scrollView), Y = Pos.Bottom (ahCheckBox), Text = k, Checked = scrollView.AutoHideScrollBars
+            X = Pos.Left (scrollView), Y = Pos.Bottom (ahCheckBox), Text = k, State = scrollView.AutoHideScrollBars ? CheckState.Checked : CheckState.UnChecked
         };
 
         hCheckBox.Toggle += (s, e) =>
                              {
-                                 if (ahCheckBox.Checked == false)
+                                 if (ahCheckBox.State == CheckState.UnChecked)
                                  {
-                                     scrollView.ShowHorizontalScrollIndicator = (bool)hCheckBox.Checked;
+                                     scrollView.ShowHorizontalScrollIndicator = e.NewValue == CheckState.Checked;
                                  }
                                  else
                                  {
-                                     hCheckBox.Checked = true;
+                                     hCheckBox.State = CheckState.Checked;
                                      MessageBox.Query ("Message", "Disable Auto Hide Scrollbars first.", "Ok");
                                  }
                              };
 
         vCheckBox.Toggle += (s, e) =>
                              {
-                                 if (ahCheckBox.Checked == false)
+                                 if (ahCheckBox.State == CheckState.UnChecked)
                                  {
-                                     scrollView.ShowVerticalScrollIndicator = (bool)vCheckBox.Checked;
+                                     scrollView.ShowVerticalScrollIndicator = e.NewValue == CheckState.Checked;
                                  }
                                  else
                                  {
-                                     vCheckBox.Checked = true;
+                                     vCheckBox.State = CheckState.Checked;
                                      MessageBox.Query ("Message", "Disable Auto Hide Scrollbars first.", "Ok");
                                  }
                              };
 
         ahCheckBox.Toggle += (s, e) =>
                               {
-                                  scrollView.AutoHideScrollBars = (bool)ahCheckBox.Checked;
-                                  hCheckBox.Checked = true;
-                                  vCheckBox.Checked = true;
+                                  scrollView.AutoHideScrollBars = e.NewValue == CheckState.Checked;
+                                  hCheckBox.State = CheckState.Checked;
+                                  vCheckBox.State = CheckState.Checked;
                               };
         app.Add (ahCheckBox);
 
-        keepCheckBox.Toggle += (s, e) => scrollView.KeepContentAlwaysInViewport = (bool)keepCheckBox.Checked;
+        keepCheckBox.Toggle += (s, e) => scrollView.KeepContentAlwaysInViewport = e.NewValue == CheckState.Checked;
         app.Add (keepCheckBox);
 
         var count = 0;

UICatalog/Scenarios/SendKeys.cs

@@ -87,9 +87,9 @@ public class SendKeys : Scenario
                 Application.Driver.SendKeys (
                                              r,
                                              ck,
-                                             (bool)ckbShift.Checked,
-                                             (bool)ckbAlt.Checked,
-                                             (bool)ckbControl.Checked
+                                             ckbShift.State == CheckState.Checked,
+                                             ckbAlt.State == CheckState.Checked,
+                                             ckbControl.State == CheckState.Checked
                                             );
             }
 

UICatalog/Scenarios/Shortcuts.cs

@@ -117,7 +117,7 @@ public class Shortcuts : Scenario
                                                               var max = 0;
                                                               var toAlign = Application.Top.Subviews.Where (v => v is Shortcut { Orientation: Orientation.Vertical, Width: not DimAbsolute });
 
-                                                              if (e.NewValue == true)
+                                                              if (e.NewValue == CheckState.Checked)
                                                               {
                                                                   foreach (Shortcut peer in toAlign)
                                                                   {
@@ -177,7 +177,7 @@ public class Shortcuts : Scenario
                                                              {
                                                                  if (peer.CanFocus)
                                                                  {
-                                                                     peer.CommandView.CanFocus = e.NewValue == true;
+                                                                     peer.CommandView.CanFocus = e.NewValue == CheckState.Checked;
                                                                  }
                                                              }
                                                          }

UICatalog/Scenarios/SpinnerStyles.cs

@@ -53,7 +53,7 @@ public class SpinnerViewStyles : Scenario
             X = Pos.Center () - 7,
             Y = Pos.Bottom (preview),
             Enabled = false,
-            Checked = true,
+            State = CheckState.Checked,
             Text = "Ascii Only"
         };
         app.Add (ckbAscii);
@@ -63,20 +63,20 @@ public class SpinnerViewStyles : Scenario
             X = Pos.Center () + 7,
             Y = Pos.Bottom (preview),
             Enabled = false,
-            Checked = true,
+            State = CheckState.Checked,
             Text = "No Special"
         };
         app.Add (ckbNoSpecial);
 
         var ckbReverse = new CheckBox
         {
-            X = Pos.Center () - 22, Y = Pos.Bottom (preview) + 1, Checked = false, Text = "Reverse"
+            X = Pos.Center () - 22, Y = Pos.Bottom (preview) + 1, State = CheckState.UnChecked, Text = "Reverse"
         };
         app.Add (ckbReverse);
 
         var ckbBounce = new CheckBox
         {
-            X = Pos.Right (ckbReverse) + 2, Y = Pos.Bottom (preview) + 1, Checked = false, Text = "Bounce"
+            X = Pos.Right (ckbReverse) + 2, Y = Pos.Bottom (preview) + 1, State = CheckState.UnChecked, Text = "Bounce"
         };
         app.Add (ckbBounce);
 
@@ -157,16 +157,16 @@ public class SpinnerViewStyles : Scenario
                                               spinner.Visible = true;
                                               spinner.Style = (SpinnerStyle)Activator.CreateInstance (styleDict [e.Item].Value);
                                               delayField.Text = spinner.SpinDelay.ToString ();
-                                              ckbBounce.Checked = spinner.SpinBounce;
-                                              ckbNoSpecial.Checked = !spinner.HasSpecialCharacters;
-                                              ckbAscii.Checked = spinner.IsAsciiOnly;
-                                              ckbReverse.Checked = false;
+                                              ckbBounce.State = spinner.SpinBounce ? CheckState.Checked : CheckState.UnChecked;
+                                              ckbNoSpecial.State = !spinner.HasSpecialCharacters ? CheckState.Checked : CheckState.UnChecked;
+                                              ckbAscii.State = spinner.IsAsciiOnly ? CheckState.Checked : CheckState.UnChecked;
+                                              ckbReverse.State = CheckState.UnChecked;
                                           }
                                       };
 
-        ckbReverse.Toggle += (s, e) => { spinner.SpinReverse = (bool)!e.CurrentValue; };
+        ckbReverse.Toggle += (s, e) => { spinner.SpinReverse = e.NewValue == CheckState.Checked; };
 
-        ckbBounce.Toggle += (s, e) => { spinner.SpinBounce = (bool)!e.CurrentValue; };
+        ckbBounce.Toggle += (s, e) => { spinner.SpinBounce = e.NewValue == CheckState.Checked; };
 
         app.Unloaded += App_Unloaded;
 

UICatalog/Scenarios/Text.cs

@@ -105,7 +105,7 @@ public class Text : Scenario
         // single-line mode.
         var chxMultiline = new CheckBox
         {
-            X = Pos.Left (textView), Y = Pos.Bottom (textView), Checked = textView.Multiline, Text = "_Multiline"
+            X = Pos.Left (textView), Y = Pos.Bottom (textView), State = textView.Multiline ? CheckState.Checked : CheckState.UnChecked, Text = "_Multiline"
         };
         Win.Add (chxMultiline);
 
@@ -113,10 +113,10 @@ public class Text : Scenario
         {
             X = Pos.Right (chxMultiline) + 2,
             Y = Pos.Top (chxMultiline),
-            Checked = textView.WordWrap,
+            State = textView.WordWrap ? CheckState.Checked : CheckState.UnChecked,
             Text = "_Word Wrap"
         };
-        chxWordWrap.Toggle += (s, e) => textView.WordWrap = (bool)e.NewValue;
+        chxWordWrap.Toggle += (s, e) => textView.WordWrap = e.NewValue == CheckState.Checked;
         Win.Add (chxWordWrap);
 
         // TextView captures Tabs (so users can enter /t into text) by default;
@@ -126,22 +126,22 @@ public class Text : Scenario
         {
             X = Pos.Right (chxWordWrap) + 2,
             Y = Pos.Top (chxWordWrap),
-            Checked = textView.AllowsTab,
+            State = textView.AllowsTab ? CheckState.Checked : CheckState.UnChecked,
             Text = "_Capture Tabs"
         };
 
         chxMultiline.Toggle += (s, e) =>
                                 {
-                                    textView.Multiline = (bool)e.NewValue;
+                                    textView.Multiline = e.NewValue == CheckState.Checked;
 
-                                    if (!textView.Multiline && (bool)chxWordWrap.Checked)
+                                    if (!textView.Multiline && chxWordWrap.State == CheckState.Checked)
                                     {
-                                        chxWordWrap.Checked = false;
+                                        chxWordWrap.State = CheckState.UnChecked;
                                     }
 
-                                    if (!textView.Multiline && (bool)chxCaptureTabs.Checked)
+                                    if (!textView.Multiline && chxCaptureTabs.State == CheckState.Checked)
                                     {
-                                        chxCaptureTabs.Checked = false;
+                                        chxCaptureTabs.State = CheckState.UnChecked;
                                     }
                                 };
 
@@ -150,7 +150,7 @@ public class Text : Scenario
 
         chxCaptureTabs.Toggle += (s, e) =>
                                   {
-                                      if (e.NewValue == true)
+                                      if (e.NewValue == CheckState.Checked)
                                       {
                                           textView.KeyBindings.Add (keyTab, Command.Tab);
                                           textView.KeyBindings.Add (keyBackTab, Command.BackTab);
@@ -161,7 +161,7 @@ public class Text : Scenario
                                           textView.KeyBindings.Remove (keyBackTab);
                                       }
 
-                                      textView.AllowsTab = (bool)e.NewValue;
+                                      textView.AllowsTab = e.NewValue == CheckState.Checked;
                                   };
         Win.Add (chxCaptureTabs);
 

UICatalog/Scenarios/TextAlignmentAndDirection.cs

@@ -484,7 +484,7 @@ public class TextAlignmentAndDirection : Scenario
             Enabled = false
         };
 
-        justifyCheckbox.Toggle += (s, e) => ToggleJustify (e.CurrentValue is { } && (bool)e.CurrentValue);
+        justifyCheckbox.Toggle += (s, e) => ToggleJustify (e.NewValue == CheckState.Checked);
 
         justifyOptions.SelectedItemChanged += (s, e) => { ToggleJustify (false, true); };
 
@@ -500,11 +500,11 @@ public class TextAlignmentAndDirection : Scenario
             Height = 1,
             Text = "Word Wrap"
         };
-        wrapCheckbox.Checked = wrapCheckbox.TextFormatter.WordWrap;
+        wrapCheckbox.State = wrapCheckbox.TextFormatter.WordWrap ? CheckState.Checked : CheckState.UnChecked;
 
         wrapCheckbox.Toggle += (s, e) =>
                                 {
-                                    if (e.CurrentValue == true)
+                                    if (e.CurrentValue == CheckState.Checked)
                                     {
                                         foreach (Label t in multiLineLabels)
                                         {
@@ -532,11 +532,11 @@ public class TextAlignmentAndDirection : Scenario
             Height = 1,
             Text = "AutoSize"
         };
-        autoSizeCheckbox.Checked = autoSizeCheckbox.TextFormatter.AutoSize;
+        autoSizeCheckbox.State = autoSizeCheckbox.TextFormatter.AutoSize ? CheckState.Checked : CheckState.UnChecked;
 
         autoSizeCheckbox.Toggle += (s, e) =>
                                     {
-                                        if (e.CurrentValue == true)
+                                        if (e.CurrentValue == CheckState.Checked)
                                         {
                                             foreach (Label t in multiLineLabels)
                                             {
@@ -570,7 +570,7 @@ public class TextAlignmentAndDirection : Scenario
 
         directionOptions.SelectedItemChanged += (s, ev) =>
                                                 {
-                                                    bool justChecked = justifyCheckbox.Checked is { } && (bool)justifyCheckbox.Checked;
+                                                    bool justChecked = justifyCheckbox.State == CheckState.Checked;
 
                                                     if (justChecked)
                                                     {

UICatalog/Scenarios/TextFormatterDemo.cs

@@ -58,7 +58,7 @@ public class TextFormatterDemo : Scenario
             X = 0,
             Y = Pos.Bottom (blockText) + 1,
             Text = "Unicode",
-            Checked = app.HotKeySpecifier == (Rune)' '
+            State = app.HotKeySpecifier == (Rune)' ' ? CheckState.Checked : CheckState.UnChecked
         };
 
         app.Add (unicodeCheckBox);
@@ -137,8 +137,8 @@ public class TextFormatterDemo : Scenario
                                    {
                                        for (int i = 0; i < alignments.Count; i++)
                                        {
-                                           singleLines [i].Text = e.CurrentValue == true ? text : unicode;
-                                           multipleLines [i].Text = e.CurrentValue == true ? text : unicode;
+                                           singleLines [i].Text = e.CurrentValue == CheckState.Checked ? text : unicode;
+                                           multipleLines [i].Text = e.CurrentValue == CheckState.Checked ? text : unicode;
                                        }
                                    };
 

UICatalog/Scenarios/TileViewNesting.cs

@@ -91,7 +91,7 @@ public class TileViewNesting : Scenario
         }
     }
 
-    private View CreateContentControl (int number) { return (bool)_cbUseLabels.Checked ? CreateLabelView (number) : CreateTextView (number); }
+    private View CreateContentControl (int number) { return _cbUseLabels.State == CheckState.Checked ? CreateLabelView (number) : CreateTextView (number); }
 
     private View CreateLabelView (int number)
     {
@@ -126,8 +126,8 @@ public class TileViewNesting : Scenario
             Orientation = orientation
         };
 
-        toReturn.Tiles.ElementAt (0).Title = (bool)_cbTitles.Checked ? $"View {titleNumber}" : string.Empty;
-        toReturn.Tiles.ElementAt (1).Title = (bool)_cbTitles.Checked ? $"View {titleNumber + 1}" : string.Empty;
+        toReturn.Tiles.ElementAt (0).Title = _cbTitles.State == CheckState.Checked ? $"View {titleNumber}" : string.Empty;
+        toReturn.Tiles.ElementAt (1).Title = _cbTitles.State == CheckState.Checked ? $"View {titleNumber + 1}" : string.Empty;
 
         return toReturn;
     }
@@ -148,9 +148,9 @@ public class TileViewNesting : Scenario
     {
         int numberOfViews = GetNumberOfViews ();
 
-        bool? titles = _cbTitles.Checked;
-        bool? border = _cbBorder.Checked;
-        bool? startHorizontal = _cbHorizontal.Checked;
+        CheckState titles = _cbTitles.State;
+        CheckState border = _cbBorder.State;
+        CheckState startHorizontal = _cbHorizontal.State;
 
         foreach (View sub in _workArea.Subviews)
         {
@@ -164,14 +164,14 @@ public class TileViewNesting : Scenario
             return;
         }
 
-        TileView root = CreateTileView (1, (bool)startHorizontal ? Orientation.Horizontal : Orientation.Vertical);
+        TileView root = CreateTileView (1, startHorizontal == CheckState.Checked ? Orientation.Horizontal : Orientation.Vertical);
 
         root.Tiles.ElementAt (0).ContentView.Add (CreateContentControl (1));
-        root.Tiles.ElementAt (0).Title = (bool)_cbTitles.Checked ? "View 1" : string.Empty;
+        root.Tiles.ElementAt (0).Title = _cbTitles.State == CheckState.Checked ? "View 1" : string.Empty;
         root.Tiles.ElementAt (1).ContentView.Add (CreateContentControl (2));
-        root.Tiles.ElementAt (1).Title = (bool)_cbTitles.Checked ? "View 2" : string.Empty;
+        root.Tiles.ElementAt (1).Title = _cbTitles.State == CheckState.Checked ? "View 2" : string.Empty;
 
-        root.LineStyle = (bool)border ? LineStyle.Rounded : LineStyle.None;
+        root.LineStyle = border  == CheckState.Checked? LineStyle.Rounded : LineStyle.None;
 
         _workArea.Add (root);
 
@@ -215,7 +215,7 @@ public class TileViewNesting : Scenario
 
         // During splitting the old Title will have been migrated to View1 so we only need
         // to set the Title on View2 (the one that gets our new TextView)
-        newView.Tiles.ElementAt (1).Title = (bool)_cbTitles.Checked ? $"View {_viewsCreated}" : string.Empty;
+        newView.Tiles.ElementAt (1).Title = _cbTitles.State == CheckState.Checked ? $"View {_viewsCreated}" : string.Empty;
 
         // Flip orientation
         newView.Orientation = to.Orientation == Orientation.Vertical

UICatalog/Scenarios/TrueColors.cs

@@ -32,7 +32,7 @@ public class TrueColors : Scenario
         {
             X = x,
             Y = y++,
-            Checked = canTrueColor,
+            State = canTrueColor ? CheckState.Checked : CheckState.UnChecked,
             CanFocus = false,
             Text = "Driver supports true color "
         };
@@ -42,11 +42,11 @@ public class TrueColors : Scenario
         {
             X = x,
             Y = y++,
-            Checked = Application.Force16Colors,
+            State = Application.Force16Colors ? CheckState.Checked : CheckState.UnChecked,
             Enabled = canTrueColor,
             Text = "Force 16 colors"
         };
-        cbUseTrueColor.Toggle += (_, evt) => { Application.Force16Colors = evt.NewValue ?? false; };
+        cbUseTrueColor.Toggle += (_, evt) => { Application.Force16Colors = evt.NewValue == CheckState.Checked; };
         app.Add (cbUseTrueColor);
 
         y += 2;

UICatalog/Scenarios/Wizards.cs

@@ -195,7 +195,7 @@ public class Wizards : Scenario
                                            var thirdStepEnabledCeckBox = new CheckBox
                                            {
                                                Text = "Enable Step _3",
-                                               Checked = false,
+                                               State = CheckState.UnChecked,
                                                X = Pos.Left (lastNameField),
                                                Y = Pos.Bottom (lastNameField)
                                            };
@@ -242,8 +242,8 @@ public class Wizards : Scenario
                                                X = Pos.Right (progLbl), Y = Pos.Top (progLbl), Width = 40, Fraction = 0.42F
                                            };
                                            thirdStep.Add (progLbl, progressBar);
-                                           thirdStep.Enabled = (bool)thirdStepEnabledCeckBox.Checked;
-                                           thirdStepEnabledCeckBox.Toggle += (s, e) => { thirdStep.Enabled = (bool)thirdStepEnabledCeckBox.Checked; };
+                                           thirdStep.Enabled = thirdStepEnabledCeckBox.State == CheckState.Checked;
+                                           thirdStepEnabledCeckBox.Toggle += (s, e) => { thirdStep.Enabled = thirdStepEnabledCeckBox.State == CheckState.Checked; };
 
                                            // Add 4th step
                                            var fourthStep = new WizardStep { Title = "Step Four" };
@@ -320,7 +320,7 @@ public class Wizards : Scenario
                                                "The wizard is complete!\n\nPress the Finish button to continue.\n\nPressing ESC will cancel the wizard.";
 
                                            var finalFinalStepEnabledCeckBox =
-                                               new CheckBox { Text = "Enable _Final Final Step", Checked = false, X = 0, Y = 1 };
+                                               new CheckBox { Text = "Enable _Final Final Step", State = CheckState.UnChecked, X = 0, Y = 1 };
                                            lastStep.Add (finalFinalStepEnabledCeckBox);
 
                                            // Add an optional FINAL last step
@@ -329,11 +329,11 @@ public class Wizards : Scenario
 
                                            finalFinalStep.HelpText =
                                                "This step only shows if it was enabled on the other last step.";
-                                           finalFinalStep.Enabled = (bool)thirdStepEnabledCeckBox.Checked;
+                                           finalFinalStep.Enabled = thirdStepEnabledCeckBox.State == CheckState.Checked;
 
                                            finalFinalStepEnabledCeckBox.Toggle += (s, e) =>
                                                                                    {
-                                                                                       finalFinalStep.Enabled = (bool)finalFinalStepEnabledCeckBox.Checked;
+                                                                                       finalFinalStep.Enabled = finalFinalStepEnabledCeckBox.State == CheckState.Checked;
                                                                                    };
 
                                            Application.Run (wizard);

UICatalog/UICatalog.cs

@@ -475,20 +475,18 @@ internal class UICatalogApp
                     CommandView = new CheckBox ()
                     {
                         Title = "16 color mode",
-                        Checked = Application.Force16Colors,
+                        State = Application.Force16Colors ? CheckState.Checked : CheckState.UnChecked,
                         CanFocus = false,
                     },
                     HelpText = "",
                     Key = Key.F6,
                 };
 
-                ShForce16Colors.Accept += (sender, args) =>
+                ((CheckBox)ShForce16Colors.CommandView).Toggle += (sender, args) =>
                                           {
-                                              ((CheckBox)ShForce16Colors.CommandView).Checked =
-                                                  Application.Force16Colors = (bool)!((CheckBox)ShForce16Colors.CommandView).Checked!;
+                                              Application.Force16Colors = args.NewValue == CheckState.Checked;
                                               MiForce16Colors!.Checked = Application.Force16Colors;
                                               Application.Refresh ();
-
                                           };
 
                 //ShDiagnostics = new Shortcut ()
@@ -1008,7 +1006,7 @@ internal class UICatalogApp
             MiForce16Colors.Action += () =>
                                       {
                                           MiForce16Colors.Checked = Application.Force16Colors = (bool)!MiForce16Colors.Checked!;
-                                          ((CheckBox)ShForce16Colors!.CommandView!).Checked = Application.Force16Colors;
+                                          ((CheckBox)ShForce16Colors!.CommandView!).State = Application.Force16Colors ? CheckState.Checked : CheckState.UnChecked;
                                           Application.Refresh ();
                                       };
             menuItems.Add (MiForce16Colors);

UnitTests/Views/CheckBoxTests.cs

@@ -77,7 +77,7 @@ public class CheckBoxTests (ITestOutputHelper output)
         Assert.Equal ("Hello", view.TitleTextFormatter.Text);
 
         Assert.Equal ("Hello", view.Text);
-        Assert.Equal ($"{CM.Glyphs.UnChecked} Hello", view.TextFormatter.Text);
+        Assert.Equal ($"{CM.Glyphs.CheckStateUnChecked} Hello", view.TextFormatter.Text);
     }
 
     [Fact]
@@ -86,7 +86,7 @@ public class CheckBoxTests (ITestOutputHelper output)
         var view = new CheckBox ();
         view.Text = "Hello";
         Assert.Equal ("Hello", view.Text);
-        Assert.Equal ($"{CM.Glyphs.UnChecked} Hello", view.TextFormatter.Text);
+        Assert.Equal ($"{CM.Glyphs.CheckStateUnChecked} Hello", view.TextFormatter.Text);
 
         Assert.Equal ("Hello", view.Title);
         Assert.Equal ("Hello", view.TitleTextFormatter.Text);
@@ -94,35 +94,35 @@ public class CheckBoxTests (ITestOutputHelper output)
 
     [Fact]
     [SetupFakeDriver]
-    public void AllowNullChecked_Get_Set ()
+    public void AllowNoneChecked_Get_Set ()
     {
         var checkBox = new CheckBox { Text = "Check this out 你" };
 
-        Assert.False (checkBox.Checked);
+        Assert.Equal (CheckState.UnChecked, checkBox.State);
         Assert.True (checkBox.NewKeyDownEvent (Key.Space));
-        Assert.True (checkBox.Checked);
-        Assert.True (checkBox.NewMouseEvent (new() { Position = new (0, 0), Flags = MouseFlags.Button1Clicked }));
-        Assert.False (checkBox.Checked);
+        Assert.Equal (CheckState.Checked, checkBox.State);
+        Assert.True (checkBox.NewMouseEvent (new () { Position = new (0, 0), Flags = MouseFlags.Button1Clicked }));
+        Assert.Equal (CheckState.UnChecked, checkBox.State);
 
-        checkBox.AllowNullChecked = true;
+        checkBox.AllowCheckStateNone = true;
         Assert.True (checkBox.NewKeyDownEvent (Key.Space));
-        Assert.Null (checkBox.Checked);
-        checkBox.Draw();
+        Assert.Equal (CheckState.None, checkBox.State);
+        checkBox.Draw ();
 
         TestHelpers.AssertDriverContentsWithFrameAre (
                                                       @$"
-{CM.Glyphs.NullChecked} Check this out 你",
+{CM.Glyphs.CheckStateNone} Check this out 你",
                                                       output
                                                      );
-        Assert.True (checkBox.NewMouseEvent (new() { Position = new (0, 0), Flags = MouseFlags.Button1Clicked }));
-        Assert.True (checkBox.Checked);
+        Assert.True (checkBox.NewMouseEvent (new () { Position = new (0, 0), Flags = MouseFlags.Button1Clicked }));
+        Assert.Equal (CheckState.Checked, checkBox.State);
         Assert.True (checkBox.NewKeyDownEvent (Key.Space));
-        Assert.False (checkBox.Checked);
-        Assert.True (checkBox.NewMouseEvent (new() { Position = new (0, 0), Flags = MouseFlags.Button1Clicked }));
-        Assert.Null (checkBox.Checked);
+        Assert.Equal (CheckState.UnChecked, checkBox.State);
+        Assert.True (checkBox.NewMouseEvent (new () { Position = new (0, 0), Flags = MouseFlags.Button1Clicked }));
+        Assert.Equal (CheckState.None, checkBox.State);
 
-        checkBox.AllowNullChecked = false;
-        Assert.False (checkBox.Checked);
+        checkBox.AllowCheckStateNone = false;
+        Assert.Equal (CheckState.UnChecked, checkBox.State);
     }
 
     [Fact]
@@ -131,40 +131,40 @@ public class CheckBoxTests (ITestOutputHelper output)
         var ckb = new CheckBox ();
         Assert.True (ckb.Width is DimAuto);
         Assert.True (ckb.Height is DimAuto);
-        Assert.False (ckb.Checked);
-        Assert.False (ckb.AllowNullChecked);
+        Assert.Equal (CheckState.UnChecked, ckb.State);
+        Assert.False (ckb.AllowCheckStateNone);
         Assert.Equal (string.Empty, ckb.Text);
-        Assert.Equal ($"{CM.Glyphs.UnChecked} ", ckb.TextFormatter.Text);
+        Assert.Equal ($"{CM.Glyphs.CheckStateUnChecked} ", ckb.TextFormatter.Text);
         Assert.True (ckb.CanFocus);
         Assert.Equal (new (0, 0, 2, 1), ckb.Frame);
 
-        ckb = new() { Text = "Test", Checked = true };
+        ckb = new () { Text = "Test", State = CheckState.Checked };
         Assert.True (ckb.Width is DimAuto);
         Assert.True (ckb.Height is DimAuto);
-        Assert.True (ckb.Checked);
-        Assert.False (ckb.AllowNullChecked);
+        Assert.Equal (CheckState.Checked, ckb.State);
+        Assert.False (ckb.AllowCheckStateNone);
         Assert.Equal ("Test", ckb.Text);
-        Assert.Equal ($"{CM.Glyphs.Checked} Test", ckb.TextFormatter.Text);
+        Assert.Equal ($"{CM.Glyphs.CheckStateChecked} Test", ckb.TextFormatter.Text);
         Assert.True (ckb.CanFocus);
         Assert.Equal (new (0, 0, 6, 1), ckb.Frame);
 
-        ckb = new() { Text = "Test", X = 1, Y = 2 };
+        ckb = new () { Text = "Test", X = 1, Y = 2 };
         Assert.True (ckb.Width is DimAuto);
         Assert.True (ckb.Height is DimAuto);
-        Assert.False (ckb.Checked);
-        Assert.False (ckb.AllowNullChecked);
+        Assert.Equal (CheckState.UnChecked, ckb.State);
+        Assert.False (ckb.AllowCheckStateNone);
         Assert.Equal ("Test", ckb.Text);
-        Assert.Equal ($"{CM.Glyphs.UnChecked} Test", ckb.TextFormatter.Text);
+        Assert.Equal ($"{CM.Glyphs.CheckStateUnChecked} Test", ckb.TextFormatter.Text);
         Assert.True (ckb.CanFocus);
         Assert.Equal (new (1, 2, 6, 1), ckb.Frame);
 
-        ckb = new() { Text = "Test", X = 3, Y = 4, Checked = true };
+        ckb = new () { Text = "Test", X = 3, Y = 4, State = CheckState.Checked };
         Assert.True (ckb.Width is DimAuto);
         Assert.True (ckb.Height is DimAuto);
-        Assert.True (ckb.Checked);
-        Assert.False (ckb.AllowNullChecked);
+        Assert.Equal (CheckState.Checked, ckb.State);
+        Assert.False (ckb.AllowCheckStateNone);
         Assert.Equal ("Test", ckb.Text);
-        Assert.Equal ($"{CM.Glyphs.Checked} Test", ckb.TextFormatter.Text);
+        Assert.Equal ($"{CM.Glyphs.CheckStateChecked} Test", ckb.TextFormatter.Text);
         Assert.True (ckb.CanFocus);
         Assert.Equal (new (3, 4, 6, 1), ckb.Frame);
     }
@@ -176,14 +176,14 @@ public class CheckBoxTests (ITestOutputHelper output)
         var ckb = new CheckBox ();
         ckb.Toggle += (s, e) => toggled = true;
 
-        Assert.False (ckb.Checked);
+        Assert.Equal (CheckState.UnChecked, ckb.State);
         Assert.False (toggled);
         Assert.Equal (Key.Empty, ckb.HotKey);
 
         ckb.Text = "_Test";
         Assert.Equal (Key.T, ckb.HotKey);
         Assert.True (ckb.NewKeyDownEvent (Key.T));
-        Assert.True (ckb.Checked);
+        Assert.Equal (CheckState.Checked, ckb.State);
         Assert.True (toggled);
 
         ckb.Text = "T_est";
@@ -191,28 +191,28 @@ public class CheckBoxTests (ITestOutputHelper output)
         Assert.Equal (Key.E, ckb.HotKey);
         Assert.True (ckb.NewKeyDownEvent (Key.E.WithAlt));
         Assert.True (toggled);
-        Assert.False (ckb.Checked);
+        Assert.Equal (CheckState.UnChecked, ckb.State);
 
         toggled = false;
         Assert.Equal (Key.E, ckb.HotKey);
         Assert.True (ckb.NewKeyDownEvent (Key.E));
         Assert.True (toggled);
-        Assert.True (ckb.Checked);
+        Assert.Equal (CheckState.Checked, ckb.State);
 
         toggled = false;
         Assert.True (ckb.NewKeyDownEvent (Key.Space));
         Assert.True (toggled);
-        Assert.False (ckb.Checked);
+        Assert.Equal (CheckState.UnChecked, ckb.State);
 
         toggled = false;
         Assert.True (ckb.NewKeyDownEvent (Key.Space));
         Assert.True (toggled);
-        Assert.True (ckb.Checked);
+        Assert.Equal (CheckState.Checked, ckb.State);
 
         toggled = false;
         Assert.False (ckb.NewKeyDownEvent (Key.Enter));
         Assert.False (toggled);
-        Assert.True (ckb.Checked);
+        Assert.Equal (CheckState.Checked, ckb.State);
     }
 
     [Fact]
@@ -263,7 +263,7 @@ public class CheckBoxTests (ITestOutputHelper output)
         var expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│    {CM.Glyphs.UnChecked} Check this out 你     │
+│    {CM.Glyphs.CheckStateUnChecked} Check this out 你     │
 │                            │
 └────────────────────────────┘
 ";
@@ -271,13 +271,13 @@ public class CheckBoxTests (ITestOutputHelper output)
         Rectangle pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
         Assert.Equal (new (0, 0, 30, 5), pos);
 
-        checkBox.Checked = true;
+        checkBox.State = CheckState.Checked;
         Application.Refresh ();
 
         expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│    {CM.Glyphs.Checked} Check this out 你     │
+│    {CM.Glyphs.CheckStateChecked} Check this out 你     │
 │                            │
 └────────────────────────────┘
 ";
@@ -324,8 +324,8 @@ public class CheckBoxTests (ITestOutputHelper output)
         var expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│ {CM.Glyphs.UnChecked}   Check  first  out  你  │
-│ {CM.Glyphs.UnChecked}  Check  second  out  你  │
+│ {CM.Glyphs.CheckStateUnChecked}   Check  first  out  你  │
+│ {CM.Glyphs.CheckStateUnChecked}  Check  second  out  你  │
 │                            │
 └────────────────────────────┘
 ";
@@ -333,10 +333,10 @@ public class CheckBoxTests (ITestOutputHelper output)
         Rectangle pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
         Assert.Equal (new (0, 0, 30, 6), pos);
 
-        checkBox1.Checked = true;
+        checkBox1.State = CheckState.Checked;
         Assert.Equal (new (1, 1, 25, 1), checkBox1.Frame);
         Assert.Equal (_size25x1, checkBox1.TextFormatter.Size);
-        checkBox2.Checked = true;
+        checkBox2.State = CheckState.Checked;
         Assert.Equal (new (1, 2, 25, 1), checkBox2.Frame);
         Assert.Equal (_size25x1, checkBox2.TextFormatter.Size);
         Application.Refresh ();
@@ -344,8 +344,8 @@ public class CheckBoxTests (ITestOutputHelper output)
         expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│ {CM.Glyphs.Checked}   Check  first  out  你  │
-│ {CM.Glyphs.Checked}  Check  second  out  你  │
+│ {CM.Glyphs.CheckStateChecked}   Check  first  out  你  │
+│ {CM.Glyphs.CheckStateChecked}  Check  second  out  你  │
 │                            │
 └────────────────────────────┘
 ";
@@ -381,7 +381,7 @@ public class CheckBoxTests (ITestOutputHelper output)
         var expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│ {CM.Glyphs.UnChecked} Check this out 你        │
+│ {CM.Glyphs.CheckStateUnChecked} Check this out 你        │
 │                            │
 └────────────────────────────┘
 ";
@@ -389,13 +389,13 @@ public class CheckBoxTests (ITestOutputHelper output)
         Rectangle pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
         Assert.Equal (new (0, 0, 30, 5), pos);
 
-        checkBox.Checked = true;
+        checkBox.State = CheckState.Checked;
         Application.Refresh ();
 
         expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│ {CM.Glyphs.Checked} Check this out 你        │
+│ {CM.Glyphs.CheckStateChecked} Check this out 你        │
 │                            │
 └────────────────────────────┘
 ";
@@ -432,7 +432,7 @@ public class CheckBoxTests (ITestOutputHelper output)
         var expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│       Check this out 你 {CM.Glyphs.UnChecked}  │
+│       Check this out 你 {CM.Glyphs.CheckStateUnChecked}  │
 │                            │
 └────────────────────────────┘
 ";
@@ -440,13 +440,13 @@ public class CheckBoxTests (ITestOutputHelper output)
         Rectangle pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
         Assert.Equal (new (0, 0, 30, 5), pos);
 
-        checkBox.Checked = true;
+        checkBox.State = CheckState.Checked;
         Application.Refresh ();
 
         expected = @$"
 ┌┤Test Demo 你├──────────────┐
 │                            │
-│       Check this out 你 {CM.Glyphs.Checked}  │
+│       Check this out 你 {CM.Glyphs.CheckStateChecked}  │
 │                            │
 └────────────────────────────┘
 ";
@@ -473,22 +473,22 @@ public class CheckBoxTests (ITestOutputHelper output)
     }
 
     [Theory]
-    [InlineData (true)]
-    [InlineData (false)]
-    [InlineData (null)]
-    public void Toggled_Cancel_Event_Prevents_Toggle (bool? initialState)
+    [InlineData (CheckState.Checked)]
+    [InlineData (CheckState.UnChecked)]
+    [InlineData (CheckState.None)]
+    public void Toggled_Cancel_Event_Prevents_Toggle (CheckState initialState)
     {
-        var ckb = new CheckBox { AllowNullChecked = true };
+        var ckb = new CheckBox { AllowCheckStateNone = true };
         var checkedInvoked = false;
 
         ckb.Toggle += CheckBoxToggle;
 
-        ckb.Checked = initialState;
-        Assert.Equal (initialState, ckb.Checked);
+        ckb.State = initialState;
+        Assert.Equal (initialState, ckb.State);
         bool? ret = ckb.OnToggle ();
         Assert.True (ret);
         Assert.True (checkedInvoked);
-        Assert.Equal (initialState, ckb.Checked);
+        Assert.Equal (initialState, ckb.State);
 
         return;
 

UnitTests/Views/MenuBarTests.cs

@@ -64,7 +64,7 @@ public class MenuBarTests (ITestOutputHelper output)
  Nullable Checked       
 ┌──────────────────────┐
 │ {
-    CM.Glyphs.NullChecked
+    CM.Glyphs.CheckStateNone
 } Check this out 你  │
 └──────────────────────┘",
                                                       output

UnitTests/Views/TreeTableSourceTests.cs

@@ -13,16 +13,16 @@ public class TreeTableSourceTests : IDisposable
     {
         _output = output;
 
-        _origChecked = ConfigurationManager.Glyphs.Checked;
-        _origUnchecked = ConfigurationManager.Glyphs.UnChecked;
-        ConfigurationManager.Glyphs.Checked = new Rune ('☑');
-        ConfigurationManager.Glyphs.UnChecked = new Rune ('☐');
+        _origChecked = ConfigurationManager.Glyphs.CheckStateChecked;
+        _origUnchecked = ConfigurationManager.Glyphs.CheckStateUnChecked;
+        ConfigurationManager.Glyphs.CheckStateChecked = new Rune ('☑');
+        ConfigurationManager.Glyphs.CheckStateUnChecked = new Rune ('☐');
     }
 
     public void Dispose ()
     {
-        ConfigurationManager.Glyphs.Checked = _origChecked;
-        ConfigurationManager.Glyphs.UnChecked = _origUnchecked;
+        ConfigurationManager.Glyphs.CheckStateChecked = _origChecked;
+        ConfigurationManager.Glyphs.CheckStateUnChecked = _origUnchecked;
     }
 
     [Fact]