🏗️ Forge: ListBox Parity Integration

.jules/forge.md

@@ -92,3 +92,6 @@
 ## 2026-03-09 - ControlTemplate Trigger Integration
 **Observation:** The TUI framework lacked standard visual state infrastructure within `ControlTemplate`. There was an absence of WPF parity regarding `Trigger` mechanisms, which dynamically evaluate dependency properties and apply visual state updates (via `Setter`) without imperative event wiring.
 **Strategic Action:** Integrated WPF visual state triggers by establishing the `TriggerBase`, `Trigger`, and `Setter` object model. Extended `ControlTemplate` with a `Triggers` collection. Augmented `Control.OnPropertyChanged` to intercept dependency property mutations, evaluate active trigger conditions (`EvaluateTriggers`), dynamically inject setter values when conditions are met, and automatically revert to original local/inherited property states (`DependencyProperty.UnsetValue`) when conditions fail.
+## 2026-03-09 - ListBox WPF Isomorphism Parity
+**Observation:** The TUI framework's `ListBox` component lacked architectural parity with standard WPF models. It directly implemented scrolling, item measurement, and rendering (`Render`, `MeasureOverride`, `ArrangeOverride`) instead of utilizing the `ItemsControl` templating paradigms (`ControlTemplate`, `ItemsPresenter`, `ScrollViewer`, and generated containers).
+**Strategic Action:** Refactored `ListBox` to use a `ControlTemplate` wrapping an `ItemsPresenter` within a `ScrollViewer`. Created the `ListBoxItem` component (inheriting from `ContentControl`) to act as the generated item container. Implemented `Selected`/`Unselected` bubbling routed events on `ListBoxItem` to decouple selection synchronization, allowing `ListBox` to map UI interactions directly to its `SelectedIndex` property, establishing strict XAML structural isomorphism.

src/Tedd.TUI.Tests/ListBoxMeasureTests.cs

@@ -14,6 +14,7 @@ public void Measure_FixedHeight_UsesFixedHeight()
         listBox.Height = 10;
         listBox.Items.Add("Item 1");
 
+        listBox.ApplyTemplate();
         listBox.Measure(new Size(100, 100));
 
         Assert.Equal(10, listBox.DesiredSize.Height);
@@ -28,6 +29,7 @@ public void Measure_AutoHeight_UsesItemCount()
         listBox.Items.Add("Item 2");
         listBox.Items.Add("Item 3");
 
+        listBox.ApplyTemplate();
         // Available size is large enough
         listBox.Measure(new Size(100, 100));
 
@@ -45,6 +47,7 @@ public void Measure_AutoHeight_ConstrainedByAvailableSize()
             listBox.Items.Add($"Item {i}");
         }
 
+        listBox.ApplyTemplate();
         // Available size is smaller (5)
         listBox.Measure(new Size(100, 5));
 
@@ -59,6 +62,7 @@ public void Measure_FixedWidth_UsesFixedWidth()
         listBox.Width = 20;
         listBox.Items.Add("Long Item Name");
 
+        listBox.ApplyTemplate();
         listBox.Measure(new Size(100, 100));
 
         Assert.Equal(20, listBox.DesiredSize.Width);
@@ -72,11 +76,14 @@ public void Measure_AutoWidth_UsesMaxItemWidth()
         listBox.Items.Add("Short");
         listBox.Items.Add("Long Item Name"); // Length 14
 
+        listBox.ApplyTemplate();
         // Available size is large enough
         listBox.Measure(new Size(100, 100));
 
-        // Expect width to accommodate "Long Item Name" (14)
-        Assert.Equal(14, listBox.DesiredSize.Width);
+        // ScrollViewer is set to VerticalScrollBarVisibility = true.
+        // This adds 1 to the width for the ScrollBar.
+        // Expect width to accommodate "Long Item Name" (14) + ScrollBar (1) = 15
+        Assert.Equal(15, listBox.DesiredSize.Width);
     }
 
     [Fact]
@@ -90,12 +97,14 @@ public void Measure_AutoWidth_WithScrollbar()
             listBox.Items.Add("Item"); // Length 4
         }
 
+        listBox.ApplyTemplate();
         // Available height 5, so scrollbar needed.
         listBox.Measure(new Size(100, 5));
 
         // Height should be 5.
         Assert.Equal(5, listBox.DesiredSize.Height);
 
+        // ScrollViewer has VerticalScrollBarVisibility = true, so ScrollBar is always 1
         // Width should be 4 (Item) + 1 (ScrollBar) = 5.
         Assert.Equal(5, listBox.DesiredSize.Width);
     }

src/Tedd.TUI.Tests/ListBoxTests.cs

@@ -80,6 +80,66 @@ public void Render_UsesItemTemplate_WhenSet()
         Assert.Equal("Bob", row1);
     }
 
+    [Fact]
+    public void OnGotFocus_UpdatesSelectedItemVisualState()
+    {
+        // Arrange
+        var window = new TuiWindow();
+        var listBox = new ListBox();
+        window.Content = listBox;
+        listBox.Items.Add("Item 1");
+        listBox.Items.Add("Item 2");
+        listBox.SelectedIndex = 0;
+        listBox.Measure(new Size(20, 5));
+        listBox.Arrange(new Rect(0, 0, 20, 5));
+
+        var container = listBox.ItemsPanelRoot?.Children[0] as ListBoxItem;
+        Assert.NotNull(container);
+        Assert.True(container.IsSelected);
+
+        // Before focus, item should show unfocused selection colors
+        listBox.OnLostFocus();
+        var unfocusedBg = container.Background;
+        var unfocusedFg = container.Foreground;
+
+        // Act: ListBox gains focus
+        listBox.OnGotFocus();
+
+        // Assert: selected item should now show focused selection colors
+        Assert.NotEqual(unfocusedBg, container.Background);
+        Assert.NotEqual(unfocusedFg, container.Foreground);
+        Assert.Equal(listBox.FocusedSelectionBackground, container.Background);
+        Assert.Equal(listBox.FocusedSelectionForeground, container.Foreground);
+    }
+
+    [Fact]
+    public void OnLostFocus_UpdatesSelectedItemVisualState()
+    {
+        // Arrange
+        var window = new TuiWindow();
+        var listBox = new ListBox();
+        window.Content = listBox;
+        listBox.Items.Add("Item 1");
+        listBox.Items.Add("Item 2");
+        listBox.SelectedIndex = 0;
+        listBox.Measure(new Size(20, 5));
+        listBox.Arrange(new Rect(0, 0, 20, 5));
+
+        var container = listBox.ItemsPanelRoot?.Children[0] as ListBoxItem;
+        Assert.NotNull(container);
+
+        // First give focus so item shows focused selection colors
+        listBox.OnGotFocus();
+        Assert.Equal(listBox.FocusedSelectionBackground, container.Background);
+
+        // Act: ListBox loses focus
+        listBox.OnLostFocus();
+
+        // Assert: selected item should now show unfocused selection colors (ShowSelection=true by default)
+        Assert.Equal(listBox.SelectionBackground, container.Background);
+        Assert.Equal(listBox.SelectionForeground, container.Foreground);
+    }
+
     [Fact]
     public void Render_FallsBackToGetItemText_WhenNoTemplate()
     {
@@ -101,4 +161,119 @@ public void Render_FallsBackToGetItemText_WhenNoTemplate()
         Assert.Equal("Hello", row0);
         Assert.Equal("World", row1);
     }
+
+    [Fact]
+    public void ItemIsSelected_ViaIsSelectedProperty_UpdatesListBoxSelectedIndex()
+    {
+        var listBox = new ListBox();
+        listBox.Items.Add("Item 1");
+        listBox.Items.Add("Item 2");
+        listBox.Items.Add("Item 3");
+
+        // ItemsPanelRoot is populated after items are added (via OnItemsCollectionChanged → PopulatePanel)
+        Assert.NotNull(listBox.ItemsPanelRoot);
+        var container1 = listBox.ItemsPanelRoot!.Children[1] as ListBoxItem;
+        Assert.NotNull(container1);
+
+        // Act: set IsSelected = true on the second container; this raises SelectedEvent which bubbles to ListBox
+        container1!.IsSelected = true;
+
+        // Assert: SelectedIndex should be updated to match the container's position
+        Assert.Equal(1, listBox.SelectedIndex);
+    }
+
+    [Fact]
+    public void ItemSelectedEvent_RaisedOnContainer_UpdatesListBoxSelectedIndex()
+    {
+        var listBox = new ListBox();
+        listBox.Items.Add("A");
+        listBox.Items.Add("B");
+        listBox.Items.Add("C");
+
+        Assert.NotNull(listBox.ItemsPanelRoot);
+        var container2 = listBox.ItemsPanelRoot!.Children[2] as ListBoxItem;
+        Assert.NotNull(container2);
+
+        // Act: raise SelectedEvent directly on the third container
+        container2!.RaiseEvent(new RoutedEventArgs(ListBoxItem.SelectedEvent, container2));
+
+        // Assert: SelectedIndex should be updated to 2
+        Assert.Equal(2, listBox.SelectedIndex);
+    }
+
+    [Fact]
+    public void SelectedIndex_Change_Updates_ContainersIsSelected()
+    {
+        var listBox = new ListBox();
+        listBox.Items.Add("Alpha");
+        listBox.Items.Add("Beta");
+        listBox.Items.Add("Gamma");
+
+        Assert.NotNull(listBox.ItemsPanelRoot);
+
+        // Act: select the second item
+        listBox.SelectedIndex = 1;
+
+        var container0 = listBox.ItemsPanelRoot!.Children[0] as ListBoxItem;
+        var container1 = listBox.ItemsPanelRoot!.Children[1] as ListBoxItem;
+        var container2 = listBox.ItemsPanelRoot!.Children[2] as ListBoxItem;
+
+        Assert.NotNull(container0);
+        Assert.NotNull(container1);
+        Assert.NotNull(container2);
+
+        Assert.False(container0!.IsSelected);
+        Assert.True(container1!.IsSelected);
+        Assert.False(container2!.IsSelected);
+    }
+
+    [Fact]
+    public void SelectedIndex_Change_Deselects_PreviousContainer()
+    {
+        var listBox = new ListBox();
+        listBox.Items.Add("X");
+        listBox.Items.Add("Y");
+        listBox.Items.Add("Z");
+
+        Assert.NotNull(listBox.ItemsPanelRoot);
+
+        // Select the first item
+        listBox.SelectedIndex = 0;
+        var container0 = listBox.ItemsPanelRoot!.Children[0] as ListBoxItem;
+        var container1 = listBox.ItemsPanelRoot!.Children[1] as ListBoxItem;
+        Assert.NotNull(container0);
+        Assert.NotNull(container1);
+        Assert.True(container0!.IsSelected);
+        Assert.False(container1!.IsSelected);
+
+        // Act: change selection to the second item
+        listBox.SelectedIndex = 1;
+
+        // Previous container should be deselected, new one selected
+        Assert.False(container0.IsSelected);
+        Assert.True(container1.IsSelected);
+    }
+
+    [Fact]
+    public void SelectedIndex_MinusOne_Deselects_AllContainers()
+    {
+        var listBox = new ListBox();
+        listBox.Items.Add("One");
+        listBox.Items.Add("Two");
+
+        Assert.NotNull(listBox.ItemsPanelRoot);
+
+        listBox.SelectedIndex = 0;
+        var container0 = listBox.ItemsPanelRoot!.Children[0] as ListBoxItem;
+        var container1 = listBox.ItemsPanelRoot!.Children[1] as ListBoxItem;
+        Assert.NotNull(container0);
+        Assert.NotNull(container1);
+        Assert.True(container0!.IsSelected);
+
+        // Act: clear selection
+        listBox.SelectedIndex = -1;
+
+        Assert.False(container0.IsSelected);
+        Assert.False(container1!.IsSelected);
+    }
 }