Merge pull request #283 from tedd/forge-content-alignment-10780616145795732953

🏗️ Forge: Control Content Alignment Parity Integration

Author: tedd

.jules/forge.md

@@ -130,6 +130,12 @@
 ## 2026-03-09 - ScrollViewer ScrollBarVisibility Attached Properties
 **Observation:** Discovered a parity deficit where `ScrollViewer.HorizontalScrollBarVisibility` and `VerticalScrollBarVisibility` were implemented as standard C# properties rather than dependency properties, and specifically, they were not attached properties. This violates WPF architecture where scroll bar visibility is a canonical attached property used widely in templates and styles on elements containing a ScrollViewer (such as ListBox).
 **Strategic Action:** Refactored `HorizontalScrollBarVisibility` and `VerticalScrollBarVisibility` to be registered via `DependencyProperty.RegisterAttached`, implementing the required static `Get...` and `Set...` methods while maintaining instance property wrappers, bringing it into strict 1:1 behavioral and structural mapping with WPF standard API.
+
+## 2026-03-09 - Control Content Alignment Parity Integration
+**Observation:** Discovered a parity deficit where the `Control` class lacked `HorizontalContentAlignment` and `VerticalContentAlignment` dependency properties. Consequently, components utilizing control templates and `ContentPresenter` (like `ContentControl`, `Button`, `GroupBox`, `Expander`) could not leverage declarative bindings to adjust the internal alignment of their content, restricting standard WPF layout paradigms.
+**Strategic Action:**
+- Registered `HorizontalContentAlignment` and `VerticalContentAlignment` dependency properties on the `Control` base class.
+- Modified default `ControlTemplate` implementations within `ContentControl`, `Button`, `GroupBox`, and `Expander` to bind the generated `ContentPresenter`'s `HorizontalAlignment` and `VerticalAlignment` directly to these new inherited parent properties, bridging a significant component styling parity gap.
 ## 2026-03-09 - DataContext Propagation Parity Integration
 **Observation:** Discovered a core architectural deficit where layout container controls (e.g., `Border`, `DialogBox`, `Table`, `TuiWindow`, `Grid`) were manually overriding `OnDataContextChanged` to explicitly assign a local `DataContext` value onto their content or child elements. This manual set operation inadvertently overwrote and masked standard logical/visual tree inheritance tracking, breaking WPF/XAML isomorphism by treating inherited context mutations as local overrides.
 **Strategic Action:**

src/Tedd.TUI/Button.cs

@@ -61,6 +61,16 @@ public Button()
             contentTemplateBinding.RelativeSource = RelativeSource.TemplatedParent;
             cp.SetBinding(ContentPresenter.ContentTemplateProperty, contentTemplateBinding);
 
+            // Bind HorizontalAlignment to parent.HorizontalContentAlignment
+            var hAlignBinding = new Binding("HorizontalContentAlignment");
+            hAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            cp.SetBinding(UIElement.HorizontalAlignmentProperty, hAlignBinding);
+
+            // Bind VerticalAlignment to parent.VerticalContentAlignment
+            var vAlignBinding = new Binding("VerticalContentAlignment");
+            vAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            cp.SetBinding(UIElement.VerticalAlignmentProperty, vAlignBinding);
+
             border.Content = cp;
             return border;
         });

src/Tedd.TUI/ContentControl.cs

@@ -40,6 +40,16 @@ public ContentControl()
             templateBinding.RelativeSource = RelativeSource.TemplatedParent;
             cp.SetBinding(ContentPresenter.ContentTemplateProperty, templateBinding);
 
+            // Bind HorizontalAlignment to parent.HorizontalContentAlignment
+            var hAlignBinding = new Binding("HorizontalContentAlignment");
+            hAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            cp.SetBinding(UIElement.HorizontalAlignmentProperty, hAlignBinding);
+
+            // Bind VerticalAlignment to parent.VerticalContentAlignment
+            var vAlignBinding = new Binding("VerticalContentAlignment");
+            vAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            cp.SetBinding(UIElement.VerticalAlignmentProperty, vAlignBinding);
+
             return cp;
         });
     }

src/Tedd.TUI/Control.cs

@@ -42,6 +42,24 @@ public Thickness BorderThickness
         set => SetValue(BorderThicknessProperty, value);
     }
 
+    public static readonly DependencyProperty HorizontalContentAlignmentProperty =
+        DependencyProperty.Register("HorizontalContentAlignment", typeof(HorizontalAlignment), typeof(Control), HorizontalAlignment.Stretch);
+
+    public HorizontalAlignment HorizontalContentAlignment
+    {
+        get => (HorizontalAlignment)GetValue(HorizontalContentAlignmentProperty);
+        set => SetValue(HorizontalContentAlignmentProperty, value);
+    }
+
+    public static readonly DependencyProperty VerticalContentAlignmentProperty =
+        DependencyProperty.Register("VerticalContentAlignment", typeof(VerticalAlignment), typeof(Control), VerticalAlignment.Stretch);
+
+    public VerticalAlignment VerticalContentAlignment
+    {
+        get => (VerticalAlignment)GetValue(VerticalContentAlignmentProperty);
+        set => SetValue(VerticalContentAlignmentProperty, value);
+    }
+
     // Tracks, per DependencyObject, which dependency properties currently have values applied by active triggers
     private System.Collections.Generic.Dictionary<DependencyObject, System.Collections.Generic.HashSet<DependencyProperty>>? _activeTriggerProperties;
 

src/Tedd.TUI/Expander.cs

@@ -79,6 +79,16 @@ public Expander()
             var contentTemplateBinding = new Binding("ContentTemplate") { RelativeSource = RelativeSource.TemplatedParent };
             contentPresenter.SetBinding(ContentPresenter.ContentTemplateProperty, contentTemplateBinding);
 
+            // Bind HorizontalAlignment to parent.HorizontalContentAlignment
+            var hAlignBinding = new Binding("HorizontalContentAlignment");
+            hAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            contentPresenter.SetBinding(UIElement.HorizontalAlignmentProperty, hAlignBinding);
+
+            // Bind VerticalAlignment to parent.VerticalContentAlignment
+            var vAlignBinding = new Binding("VerticalContentAlignment");
+            vAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            contentPresenter.SetBinding(UIElement.VerticalAlignmentProperty, vAlignBinding);
+
             contentPresenter.Visibility = expander.IsExpanded;
 
             stack.Children.Add(contentPresenter);

src/Tedd.TUI/GroupBox.cs

@@ -63,6 +63,16 @@ public GroupBox()
             contentTemplateBinding.RelativeSource = RelativeSource.TemplatedParent;
             cp.SetBinding(ContentPresenter.ContentTemplateProperty, contentTemplateBinding);
 
+            // Bind HorizontalAlignment to parent.HorizontalContentAlignment
+            var hAlignBinding = new Binding("HorizontalContentAlignment");
+            hAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            cp.SetBinding(UIElement.HorizontalAlignmentProperty, hAlignBinding);
+
+            // Bind VerticalAlignment to parent.VerticalContentAlignment
+            var vAlignBinding = new Binding("VerticalContentAlignment");
+            vAlignBinding.RelativeSource = RelativeSource.TemplatedParent;
+            cp.SetBinding(UIElement.VerticalAlignmentProperty, vAlignBinding);
+
             border.Content = cp;
 
             var titleCp = new ContentPresenter();