Fixes #3522. Adds IDesignable: Ability for Views to load design-time/demo data

Terminal.Gui/View/ISupportsDesignMode.cs

@@ -0,0 +1,14 @@
+namespace Terminal.Gui;
+
+/// <summary>
+/// Indicates that the view supports design mode.
+/// </summary>
+public interface ISupportsDesignMode
+{
+    /// <summary>
+    /// Call this to tell the View to load "demo data"
+    /// </summary>
+    /// <param name="ctx">Optional arbitrary context.</param>
+    /// <returns><see langword="true"/> if the view succesfully loaded demo data.</returns>
+    public bool LoadDemoData (object ctx = null);
+}

Terminal.Gui/Views/Button.cs

@@ -25,7 +25,7 @@ namespace Terminal.Gui;
 ///         invoked repeatedly while the button is pressed.
 ///     </para>
 /// </remarks>
-public class Button : View
+public class Button : View, ISupportsDesignMode
 {
     private readonly Rune _leftBracket;
     private readonly Rune _leftDefault;
@@ -177,4 +177,12 @@ protected override void UpdateTextFormatterText ()
             }
         }
     }
+
+    /// <inheritdoc />
+    public bool LoadDemoData (object ctx = null)
+    {
+        Title = "_Button";
+
+        return true;
+    }
 }

Terminal.Gui/Views/ComboBox.cs

@@ -11,7 +11,7 @@
 namespace Terminal.Gui;
 
 /// <summary>Provides a drop-down list of items the user can select from.</summary>
-public class ComboBox : View
+public class ComboBox : View, ISupportsDesignMode
 {
     private readonly ComboListView _listview;
     private readonly int _minimumHeight = 2;
@@ -243,7 +243,7 @@ public virtual bool Expand ()
     public event EventHandler Expanded;
 
     /// <inheritdoc/>
-    protected internal override bool OnMouseEvent  (MouseEvent me)
+    protected internal override bool OnMouseEvent (MouseEvent me)
     {
         if (me.Position.X == Viewport.Right - 1
             && me.Position.Y == Viewport.Top
@@ -813,7 +813,7 @@ public bool HideDropdownListOnClick
             set => _hideDropdownListOnClick = WantContinuousButtonPressed = value;
         }
 
-        protected internal override bool OnMouseEvent  (MouseEvent me)
+        protected internal override bool OnMouseEvent (MouseEvent me)
         {
             var res = false;
             bool isMousePositionValid = IsMousePositionValid (me);
@@ -983,4 +983,14 @@ private void SetInitialProperties (ComboBox container, bool hideDropdownListOnCl
             AddCommand (Command.LineUp, () => _container.MoveUpList ());
         }
     }
+
+    /// <inheritdoc />
+    public bool LoadDemoData (object ctx = null)
+    {
+        var source = new ObservableCollection<string> (["Combo Item 1", "Combo Item two", "Combo Item Quattro", "Last Combo Item"]);
+        SetSource (source);
+        Height = Dim.Auto (DimAutoStyle.Content, minimumContentDim: source.Count + 1);
+
+        return true;
+    }
 }

Terminal.Gui/Views/ListView.cs

@@ -101,7 +101,7 @@ void Render (
 ///         first item that starts with what the user types will be selected.
 ///     </para>
 /// </remarks>
-public class ListView : View
+public class ListView : View, ISupportsDesignMode
 {
     private bool _allowsMarking;
     private bool _allowsMultipleSelection = true;
@@ -921,6 +921,15 @@ public void ResumeSuspendCollectionChangedEvent ()
             Source.SuspendCollectionChangedEvent = false;
         }
     }
+
+    /// <inheritdoc />
+    public bool LoadDemoData (object ctx = null)
+    {
+        var source = new ListWrapper<string> (["List Item 1", "List Item two", "List Item Quattro", "Last List Item"]);
+        Source = source;
+
+        return true;
+    }
 }
 
 /// <summary>

Terminal.Gui/Views/Menu/MenuBar.cs

@@ -34,7 +34,7 @@ namespace Terminal.Gui;
 ///         duplicates a shortcut (e.g. _File and Alt-F), the hot key wins.
 ///     </para>
 /// </remarks>
-public class MenuBar : View
+public class MenuBar : View, ISupportsDesignMode
 {
     // Spaces before the Title
     private static readonly int _leftPadding = 1;
@@ -1591,4 +1591,179 @@ private MenuBar GetMouseGrabViewInstance (View view)
     }
 
     #endregion Mouse Handling
+
+
+    /// <inheritdoc />
+    public bool LoadDemoData (object ctx = null)
+    {
+        Func<string, bool> actionFn = (Func<string, bool>)ctx;
+
+        if (actionFn is null)
+        {
+            actionFn = (s) => true;
+        }
+
+        Menus =
+        [
+            new MenuBarItem (
+                             "_File",
+                             new MenuItem []
+                             {
+                                 new (
+                                      "_New",
+                                      "",
+                                      () => actionFn ("New"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.N
+                                     ),
+                                 new (
+                                      "_Open",
+                                      "",
+                                      () => actionFn ("Open"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.O
+                                     ),
+                                 new (
+                                      "_Save",
+                                      "",
+                                      () => actionFn ("Save"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.S
+                                     ),
+                                 null,
+
+                                 // Don't use Application.Quit so we can disambiguate between quitting and closing the toplevel
+                                 new (
+                                      "_Quit",
+                                      "",
+                                      () => actionFn ("Quit"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.Q
+                                     )
+                             }
+                            ),
+            new MenuBarItem (
+                             "_Edit",
+                             new MenuItem []
+                             {
+                                 new (
+                                      "_Copy",
+                                      "",
+                                      () => actionFn ("Copy"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.C
+                                     ),
+                                 new (
+                                      "C_ut",
+                                      "",
+                                      () => actionFn ("Cut"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.X
+                                     ),
+                                 new (
+                                      "_Paste",
+                                      "",
+                                      () => actionFn ("Paste"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask | KeyCode.V
+                                     ),
+                                 new MenuBarItem (
+                                                  "_Find and Replace",
+                                                  new MenuItem []
+                                                  {
+                                                      new (
+                                                           "F_ind",
+                                                           "",
+                                                           () => actionFn ("Find"),
+                                                           null,
+                                                           null,
+                                                           KeyCode.CtrlMask | KeyCode.F
+                                                          ),
+                                                      new (
+                                                           "_Replace",
+                                                           "",
+                                                           () => actionFn ("Replace"),
+                                                           null,
+                                                           null,
+                                                           KeyCode.CtrlMask | KeyCode.H
+                                                          ),
+                                                      new MenuBarItem (
+                                                                       "_3rd Level",
+                                                                       new MenuItem []
+                                                                       {
+                                                                           new (
+                                                                                "_1st",
+                                                                                "",
+                                                                                () => actionFn (
+                                                                                                "1"
+                                                                                               ),
+                                                                                null,
+                                                                                null,
+                                                                                KeyCode.F1
+                                                                               ),
+                                                                           new (
+                                                                                "_2nd",
+                                                                                "",
+                                                                                () => actionFn (
+                                                                                                "2"
+                                                                                               ),
+                                                                                null,
+                                                                                null,
+                                                                                KeyCode.F2
+                                                                               )
+                                                                       }
+                                                                      ),
+                                                      new MenuBarItem (
+                                                                       "_4th Level",
+                                                                       new MenuItem []
+                                                                       {
+                                                                           new (
+                                                                                "_5th",
+                                                                                "",
+                                                                                () => actionFn (
+                                                                                                "5"
+                                                                                               ),
+                                                                                null,
+                                                                                null,
+                                                                                KeyCode.CtrlMask
+                                                                                | KeyCode.D5
+                                                                               ),
+                                                                           new (
+                                                                                "_6th",
+                                                                                "",
+                                                                                () => actionFn (
+                                                                                                "6"
+                                                                                               ),
+                                                                                null,
+                                                                                null,
+                                                                                KeyCode.CtrlMask
+                                                                                | KeyCode.D6
+                                                                               )
+                                                                       }
+                                                                      )
+                                                  }
+                                                 ),
+                                 new (
+                                      "_Select All",
+                                      "",
+                                      () => actionFn ("Select All"),
+                                      null,
+                                      null,
+                                      KeyCode.CtrlMask
+                                      | KeyCode.ShiftMask
+                                      | KeyCode.S
+                                     )
+                             }
+                            ),
+            new MenuBarItem ("_About", "Top-Level", () => actionFn ("About"))
+        ];
+        return true;
+    }
 }

Terminal.Gui/Views/ProgressBar.cs

@@ -35,7 +35,7 @@ public enum ProgressBarFormat
 ///         <see cref="Pulse"/> method is called. Call <see cref="Pulse"/> repeatedly as progress is made.
 ///     </para>
 /// </remarks>
-public class ProgressBar : View
+public class ProgressBar : View, ISupportsDesignMode
 {
     private int [] _activityPos;
     private bool _bidirectionalMarquee = true;
@@ -277,4 +277,13 @@ private void SetInitialProperties ()
         _fraction = 0;
         Initialized += ProgressBar_Initialized;
     }
+
+    /// <inheritdoc />
+    public bool LoadDemoData (object ctx = null)
+    {
+        Width = Dim.Fill ();
+        Height = Dim.Auto (DimAutoStyle.Text, minimumContentDim: 1);
+        Fraction = 0.75f;
+        return true;
+    }
 }

Terminal.Gui/Views/RadioGroup.cs

@@ -1,7 +1,7 @@
 namespace Terminal.Gui;
 
 /// <summary>Displays a group of labels each with a selected indicator. Only one of those can be selected at a given time.</summary>
-public class RadioGroup : View
+public class RadioGroup : View, ISupportsDesignMode
 {
     private int _cursor;
     private List<(int pos, int length)> _horizontal;
@@ -229,32 +229,6 @@ public string [] RadioLabels
         }
     }
 
-    /// <inheritdoc/>
-    public override string Text
-    {
-        get
-        {
-            if (_radioLabels.Count == 0)
-            {
-                return string.Empty;
-            }
-
-            // Return labels as a CSV string
-            return string.Join (",", _radioLabels);
-        }
-        set
-        {
-            if (string.IsNullOrEmpty (value))
-            {
-                RadioLabels = [];
-            }
-            else
-            {
-                RadioLabels = value.Split (',').Select (x => x.Trim ()).ToArray ();
-            }
-        }
-    }
-
     /// <summary>The currently selected item from the list of radio labels</summary>
     /// <value>The selected.</value>
     public int SelectedItem
@@ -487,4 +461,11 @@ private void SetContentSize ()
                 break;
         }
     }
+
+    /// <inheritdoc />
+    public bool LoadDemoData (object ctx = null)
+    {
+        RadioLabels = new [] { "Option _1", "Option _2", "Option _3" };
+        return true;
+    }
 }