Fixes #5088 - Margin Shadow sizing wrong

Examples/UICatalog/Scenarios/ShadowStyleDemo.cs

@@ -12,30 +12,31 @@ public override void Main ()
         using IApplication app = Application.Create ();
         app.Init ();
 
-        using Window window = new ()
-        {
-            Id = "app",
-            Title = GetQuitKeyAndName ()
-        };
+        using Window window = new ();
+        window.Id = "app";
+        window.Title = GetQuitKeyAndName ();
+        window.SchemeName = SchemeManager.SchemesToSchemeName (Schemes.Accent);
 
         AdornmentsEditor editor = new ()
         {
-            Id = "editor",
+            BorderStyle = LineStyle.Single,
             AutoSelectViewToEdit = true,
-            ShowViewIdentifier = true
-        };
-        editor.Initialized += (_, _) => editor.MarginEditor!.ExpanderButton!.Collapsed = false;
 
-        window.Add (editor);
+            // This is for giggles, to show that the editor can be moved around.
+            Arrangement = ViewArrangement.Movable,
+            Id = "editor"
+        };
+        editor.Border.Thickness = new Thickness (1, 2, 1, 1);
 
         Window shadowWindow = new ()
         {
             Id = "shadowWindow",
-            X = Pos.Right (editor),
+            X = Pos.Center (),
             Y = 0,
             Width = Dim.Percent (30),
             Height = Dim.Percent (30),
             Title = "Shadow Window",
+            SchemeName = SchemeManager.SchemesToSchemeName (Schemes.Accent),
             Arrangement = ViewArrangement.Movable | ViewArrangement.Overlapped,
             BorderStyle = LineStyle.Double,
             ShadowStyle = ShadowStyles.Transparent
@@ -51,11 +52,11 @@ public override void Main ()
         {
             Id = "buttonInWin",
             X = Pos.Center (),
-            Y = Pos.Center (), Text = "Button in Window",
+            Y = Pos.Center (),
+            Text = "Button in Window",
             ShadowStyle = ShadowStyles.Opaque
         };
         shadowWindow.Add (buttonInWin);
-        window.Add (shadowWindow);
 
         Window shadowWindow2 = new ()
         {
@@ -65,17 +66,18 @@ public override void Main ()
             Width = Dim.Percent (30),
             Height = Dim.Percent (30),
             Title = "Shadow Window #2",
+            SchemeName = SchemeManager.SchemesToSchemeName (Schemes.Error),
             Arrangement = ViewArrangement.Movable | ViewArrangement.Overlapped,
             BorderStyle = LineStyle.Double,
             ShadowStyle = ShadowStyles.Transparent
         };
-        window.Add (shadowWindow2);
 
         Button button = new ()
         {
             Id = "button",
             X = Pos.Right (editor) + 10,
-            Y = Pos.Center (), Text = "Button",
+            Y = Pos.Center (),
+            Text = "Button",
             ShadowStyle = ShadowStyles.Opaque
         };
         button.Accepting += ButtonOnAccepting;
@@ -84,7 +86,7 @@ public override void Main ()
         {
             Title = "ColorPicker to illustrate highlight (currently broken)",
             BorderStyle = LineStyle.Dotted,
-            Id = "colorPicker16",
+            Id = "colorPicker",
             X = Pos.Center (),
             Y = Pos.AnchorEnd (),
             Width = Dim.Percent (80)
@@ -93,13 +95,18 @@ public override void Main ()
         colorPicker.ValueChanged += (_, args) =>
                                     {
                                         Attribute normal = window.GetScheme ().Normal;
-                                        window.SetScheme (window.GetScheme () with { Normal = new (normal.Foreground, args.NewValue ?? Color.Black) });
+
+                                        window.SetScheme (window.GetScheme () with
+                                        {
+                                            Normal = new Attribute (normal.Foreground, args.NewValue ?? Color.Black)
+                                        });
                                     };
-        window.Add (button, colorPicker);
+        window.Add (button, colorPicker, editor, shadowWindow, shadowWindow2);
 
+        editor.ShowViewIdentifier = true;
         editor.AutoSelectViewToEdit = true;
         editor.AutoSelectSuperView = window;
-        editor.AutoSelectAdornments = false;
+        editor.AutoSelectAdornments = true;
 
         app.Run (window);
     }

Terminal.Gui/ViewBase/Adornment/Margin.cs

@@ -56,7 +56,7 @@ protected override void OnThicknessChanged ()
     /// </summary>
     public ShadowStyles? ShadowStyle
     {
-        get => field ?? Parent?.SuperView?.ShadowStyle ?? null;
+        get => field;
         set
         {
             if (field == value)
@@ -68,7 +68,11 @@ public ShadowStyles? ShadowStyle
             if (field is null)
             {
                 // null means no shadow and no thickness
-                (View as MarginView)?.SetShadow (null);
+                if (View is MarginView mv)
+                {
+                    mv.SetShadow (null);
+                    mv.ShadowSize = Size.Empty;
+                }
 
                 return;
             }

Tests/UnitTestsParallelizable/ViewBase/Adornment/ShadowTests.cs

@@ -128,7 +128,7 @@ public void Changing_ShadowStyle_Correctly_Set_ShadowWidth_ShadowHeight_Thicknes
         Assert.Equal (new Thickness (0, 0, 2, 2), view.Margin.Thickness);
 
         view.ShadowStyle = null;
-        Assert.Equal (new Size (2, 2), (view.Margin.View as MarginView)?.ShadowSize);
+        Assert.Equal (Size.Empty, (view.Margin.View as MarginView)?.ShadowSize);
         Assert.Equal (new Thickness (0, 0, 0, 0), view.Margin.Thickness);
 
         view.ShadowStyle = ShadowStyles.Opaque;
@@ -577,4 +577,62 @@ public void TransparentShadow_OverWide_Draws_Transparent_At_Driver_Output ()
                                            output,
                                            app.Driver);
     }
+
+    /// <summary>
+    ///     Proves Issue #5088: ShadowStyle getter returns an inherited value from
+    ///     SuperView even though no shadow was ever set on the view itself. Reading the
+    ///     value and writing it back should be a no-op, but instead it creates a
+    ///     MarginView and adds shadow thickness.
+    /// </summary>
+    [Fact]
+    public void ShadowStyle_Getter_Does_Not_Inherit_From_SuperView ()
+    {
+        // Explicitly give the SuperView a transparent shadow for this inheritance test.
+        Window superView = new () { Width = 20, Height = 10, ShadowStyle = ShadowStyles.Transparent };
+
+        View child = new () { Width = 5, Height = 3 };
+        superView.Add (child);
+
+        // The subview was never assigned a ShadowStyle - it must be null.
+        Assert.Null (child.Margin.ShadowStyle);
+        Assert.Null (child.ShadowStyle);
+
+        // Round-trip: reading and writing back should be a safe no-op.
+        ShadowStyles? readBack = child.ShadowStyle;
+        child.ShadowStyle = readBack;
+
+        // After the round-trip the subview must still have no shadow and no Margin thickness.
+        Assert.Null (child.ShadowStyle);
+        Assert.Equal (Thickness.Empty, child.Margin.Thickness);
+
+        // MarginView should NOT have been created by a no-op assignment.
+        Assert.Null (child.Margin.View);
+
+        child.Dispose ();
+        superView.Dispose ();
+    }
+
+    /// <summary>
+    ///     Proves that setting ShadowStyle to null resets ShadowSize on the MarginView
+    ///     to <see cref="Size.Empty"/>, so that state is consistent when no shadow is active.
+    /// </summary>
+    [Fact]
+    public void Setting_ShadowStyle_Null_Resets_ShadowSize ()
+    {
+        View view = new ();
+
+        // Set a shadow - this creates a MarginView with ShadowSize {1,1}.
+        view.ShadowStyle = ShadowStyles.Transparent;
+        var marginView = view.Margin.View as MarginView;
+        Assert.NotNull (marginView);
+        Assert.Equal (new Size (1, 1), marginView.ShadowSize);
+
+        // Now clear the shadow.
+        view.ShadowStyle = null;
+
+        // ShadowSize should be reset to Empty - no residual state.
+        Assert.Equal (Size.Empty, marginView.ShadowSize);
+
+        view.Dispose ();
+    }
 }