Add Comment headers and scrolling comment text.

Author: JamesVaughan

src/XTMF2.GUI/Controls/ModelSystemCanvas.cs

@@ -144,7 +144,13 @@ public sealed partial class ModelSystemCanvas : Control
     private CommentBlockViewModel? _editingCommentBlock;
     /// <summary>Model-space position and size of the comment editor overlay.</summary>
     private double _editingCommentEditorX, _editingCommentEditorY, _editingCommentEditorW, _editingCommentEditorH;
-
+    // ── Inline comment header editor ───────────────────────────────
+    /// <summary>Overlay single-line TextBox used for editing the comment block header.</summary>
+    private readonly TextBox _commentHeaderEditor;
+    /// <summary>The comment block whose header is being edited, or <c>null</c> when idle.</summary>
+    private CommentBlockViewModel? _editingCommentHeaderBlock;
+    /// <summary>Model-space position and size of the comment header editor overlay.</summary>
+    private double _editingCommentHeaderEditorX, _editingCommentHeaderEditorY, _editingCommentHeaderEditorW, _editingCommentHeaderEditorH;
     // ── Inline name editor ───────────────────────────────────────────────────
     /// <summary>Overlay single-line TextBox used for renaming nodes and starts.</summary>
     private readonly TextBox _nameEditor;
@@ -167,6 +173,11 @@ public sealed partial class ModelSystemCanvas : Control
     private readonly Dictionary<(FunctionInstanceViewModel, FunctionParameterHook), NodeViewModel>
         _fiHookInlinedParam = new();
     /// <summary>
+    /// Stores the maximum scroll offset (model-space px) for each comment block, computed during
+    /// render. Used by the wheel handler to clamp scroll without recomputing the text layout.
+    /// </summary>
+    private readonly Dictionary<CommentBlockViewModel, double> _commentMaxScrollOffsets = new();
+    /// <summary>
     /// BasicParameter nodes that are visible on the canvas AND connected via a Single (or
     /// FunctionParameterHook) hook, so they can offer a "minimize to inline" button.
     /// </summary>
@@ -266,6 +277,26 @@ public ModelSystemCanvas()
         LogicalChildren.Add(_commentEditor);
         VisualChildren.Add(_commentEditor);
 
+        // Build the single-line comment header editor; Enter commits, Escape cancels.
+        _commentHeaderEditor = new TextBox
+        {
+            FontFamily = new Avalonia.Media.FontFamily("Segoe UI, Arial, sans-serif"),
+            FontSize = CommentHeaderFontSize,
+            FontWeight = Avalonia.Media.FontWeight.Bold,
+            Foreground = CommentTextBrush,
+            Background = new SolidColorBrush(Color.FromArgb(0xF2, 0xFF, 0xD5, 0x1A)),
+            BorderThickness = new Thickness(1),
+            BorderBrush = CommentBorderBrush,
+            Padding = new Thickness(6, 2, 6, 2),
+            VerticalContentAlignment = Avalonia.Layout.VerticalAlignment.Center,
+            IsVisible = false,
+        };
+        _commentHeaderEditor.LostFocus += OnCommentHeaderEditorLostFocus;
+        _commentHeaderEditor.AddHandler(InputElement.KeyDownEvent, OnCommentHeaderEditorKeyDown,
+                                        Avalonia.Interactivity.RoutingStrategies.Tunnel);
+        LogicalChildren.Add(_commentHeaderEditor);
+        VisualChildren.Add(_commentHeaderEditor);
+
         // Build the single-line name editor; Enter commits, Escape cancels.
         _nameEditor = new TextBox
         {
@@ -634,6 +665,11 @@ protected override Size MeasureOverride(Size availableSize)
         {
             _commentEditor.Measure(new Size(_editingCommentEditorW * _scale, _editingCommentEditorH * _scale));
         }
+        // Measure the comment header editor.
+        if (_editingCommentHeaderBlock is not null)
+        {
+            _commentHeaderEditor.Measure(new Size(_editingCommentHeaderEditorW * _scale, _editingCommentHeaderEditorH * _scale));
+        }
         // Measure the name editor.
         if (_editingNameElement is not null)
         {
@@ -704,6 +740,16 @@ protected override Size ArrangeOverride(Size finalSize)
                 _editingCommentEditorW * _scale,
                 _editingCommentEditorH * _scale));
         }
+        // Position the comment header editor over the header band of the block being edited.
+        if (_editingCommentHeaderBlock is not null)
+        {
+            _commentHeaderEditor.FontSize = CommentHeaderFontSize * _scale;
+            _commentHeaderEditor.Arrange(new Rect(
+                _editingCommentHeaderEditorX * _scale,
+                _editingCommentHeaderEditorY * _scale,
+                _editingCommentHeaderEditorW * _scale,
+                _editingCommentHeaderEditorH * _scale));
+        }
         // Position the name editor over the element header being renamed.
         if (_editingNameElement is not null)
         {

src/XTMF2.GUI/Controls/ModelSystemCanvas/ModelSystemCanvas.Input.cs

@@ -238,6 +238,23 @@ protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
             e.Handled = true;
             return;
         }
+        // If the pointer is over a comment block, scroll its comment body text.
+        if (_vm is not null)
+        {
+            var mpos = ToCanvasPos(e.GetPosition(this));
+            var commentHit = HitTest(mpos, testComments: true) as CommentBlockViewModel;
+            if (commentHit is not null)
+            {
+                const double scrollStep = 24.0;
+                double newOffset = commentHit.CommentScrollOffset - e.Delta.Y * scrollStep;
+                // Clamp to [0, maxScroll] using the last-rendered max (0 if not yet rendered).
+                _commentMaxScrollOffsets.TryGetValue(commentHit, out double maxScroll);
+                commentHit.CommentScrollOffset = Math.Min(Math.Max(0.0, newOffset), maxScroll);
+                InvalidateVisual();
+                e.Handled = true;
+                return;
+            }
+        }
         base.OnPointerWheelChanged(e);
     }
 
@@ -266,12 +283,14 @@ private void OnPointerPressedTunnel(object? sender, PointerPressedEventArgs e)
         bool isResizingEditedElement =
             ReferenceEquals(resizeHit, _editingParamNode) ||
             ReferenceEquals(resizeHit, _editingNameElement) ||
-            ReferenceEquals(resizeHit, _editingCommentBlock);
+            ReferenceEquals(resizeHit, _editingCommentBlock) ||
+            ReferenceEquals(resizeHit, _editingCommentHeaderBlock);
 
         if (!isResizingEditedElement)
         {
             if (_editingParamNode is not null) CommitParamEdit();
             if (_editingCommentBlock is not null) CommitCommentEdit();
+            if (_editingCommentHeaderBlock is not null) CommitCommentHeaderEdit();
             if (_editingNameElement is not null) CommitNameEdit();
         }
 
@@ -320,12 +339,14 @@ protected override void OnPointerPressed(PointerPressedEventArgs e)
                 bool isResizingEditedElement =
                     ReferenceEquals(resizeHit, _editingParamNode) ||
                     ReferenceEquals(resizeHit, _editingNameElement) ||
-                    ReferenceEquals(resizeHit, _editingCommentBlock);
+                    ReferenceEquals(resizeHit, _editingCommentBlock) ||
+                    ReferenceEquals(resizeHit, _editingCommentHeaderBlock);
 
                 if (!isResizingEditedElement)
                 {
                     if (_editingParamNode is not null) CommitParamEdit();
                     if (_editingCommentBlock is not null) CommitCommentEdit();
+                    if (_editingCommentHeaderBlock is not null) CommitCommentHeaderEdit();
                     if (_editingNameElement is not null) CommitNameEdit();
                 }
                 ClearMultiSelection();
@@ -349,6 +370,7 @@ protected override void OnPointerPressed(PointerPressedEventArgs e)
             {
                 if (_editingParamNode is not null) CommitParamEdit();
                 if (_editingCommentBlock is not null) CommitCommentEdit();
+                if (_editingCommentHeaderBlock is not null) CommitCommentHeaderEdit();
                 if (_editingNameElement is not null) CommitNameEdit();
                 minimizeHit.InlineBasicParameter();
                 InvalidateAndMeasure();
@@ -391,6 +413,7 @@ protected override void OnPointerPressed(PointerPressedEventArgs e)
                     ReferenceEquals(clickedElement, _editingParamNode) ||
                     ReferenceEquals(clickedElement, _editingNameElement) ||
                     ReferenceEquals(clickedElement, _editingCommentBlock) ||
+                    ReferenceEquals(clickedElement, _editingCommentHeaderBlock) ||
                     (clickedElement is not null && _multiSelection.Contains(clickedElement) &&
                      ((_editingParamNode is not null && _multiSelection.Contains(_editingParamNode)) || 
                       (_editingNameElement is not null && _multiSelection.Contains(_editingNameElement)) ||
@@ -401,6 +424,7 @@ protected override void OnPointerPressed(PointerPressedEventArgs e)
                 {
                     if (_editingParamNode is not null) CommitParamEdit();
                     if (_editingCommentBlock is not null) CommitCommentEdit();
+                    if (_editingCommentHeaderBlock is not null) CommitCommentHeaderEdit();
                     if (_editingNameElement is not null) CommitNameEdit();
                 }
             }
@@ -466,12 +490,16 @@ protected override void OnPointerPressed(PointerPressedEventArgs e)
                 return;
             }
 
-            // ── Double-click on a comment block: open the inline comment editor ──
+            // ── Double-click on a comment block: open the inline comment or header editor ──
             var commentHit = HitTest(mpos, testComments: true) as CommentBlockViewModel;
             if (commentHit is not null)
             {
                 _vm.SelectElementCommand.Execute(commentHit);
-                BeginCommentEdit(commentHit);
+                // Open the header editor when the click lands in the header band; otherwise the comment editor.
+                if (mpos.Y < commentHit.Y + CommentHeaderHeight)
+                    BeginCommentHeaderEdit(commentHit);
+                else
+                    BeginCommentEdit(commentHit);
                 e.Handled = true;
                 return;
             }
@@ -554,6 +582,7 @@ protected override void OnPointerPressed(PointerPressedEventArgs e)
             // Always commit any open inline edit first.
             if (_editingParamNode is not null) CommitParamEdit();
             if (_editingCommentBlock is not null) CommitCommentEdit();
+            if (_editingCommentHeaderBlock is not null) CommitCommentHeaderEdit();
             if (_editingNameElement is not null) CommitNameEdit();
 
             if (hit is not null)
@@ -672,7 +701,8 @@ protected override void OnPointerMoved(PointerEventArgs e)
             // Only sync inline editor if it's the element being resized
             if (ReferenceEquals(_resizing, _editingParamNode) || 
                 ReferenceEquals(_resizing, _editingNameElement) || 
-                ReferenceEquals(_resizing, _editingCommentBlock))
+                ReferenceEquals(_resizing, _editingCommentBlock) ||
+                ReferenceEquals(_resizing, _editingCommentHeaderBlock))
             {
                 SyncEditingElementPositions();
             }
@@ -743,14 +773,16 @@ protected override void OnPointerMoved(PointerEventArgs e)
         {
             if ((_editingParamNode is not null && _multiSelection.Contains(_editingParamNode)) || 
                 (_editingNameElement is not null && _multiSelection.Contains(_editingNameElement)) || 
-                (_editingCommentBlock is not null && _multiSelection.Contains(_editingCommentBlock)))
+                (_editingCommentBlock is not null && _multiSelection.Contains(_editingCommentBlock)) ||
+                (_editingCommentHeaderBlock is not null && _multiSelection.Contains(_editingCommentHeaderBlock)))
             {
                 SyncEditingElementPositions();
             }
         }
         else if (ReferenceEquals(_dragging, _editingParamNode) || 
                  ReferenceEquals(_dragging, _editingNameElement) || 
-                 ReferenceEquals(_dragging, _editingCommentBlock))
+                 ReferenceEquals(_dragging, _editingCommentBlock) ||
+                 ReferenceEquals(_dragging, _editingCommentHeaderBlock))
         {
             SyncEditingElementPositions();
         }

src/XTMF2.GUI/Controls/ModelSystemCanvas/ModelSystemCanvas.NameCommentEditing.cs

@@ -34,6 +34,7 @@ private void BeginNameEdit(ICanvasElement element)
     {
         CommitParamEdit();
         CommitCommentEdit();
+        CommitCommentHeaderEdit();
 
         bool isLight = Application.Current?.ActualThemeVariant == ThemeVariant.Light;
         _nameEditor.Foreground = isLight ? Brushes.Black : Brushes.White;
@@ -179,14 +180,15 @@ public void BeginCommentEditForSelected()
         }
     }
 
-    /// <summary>Shows the multi-line comment editor over <paramref name="comment"/>.</summary>
+    /// <summary>Shows the multi-line comment editor over <paramref name="comment"/>, positioned below the header band.</summary>
     private void BeginCommentEdit(CommentBlockViewModel comment)
     {
+        CommitCommentHeaderEdit();
         _editingCommentBlock = comment;
         _editingCommentEditorX = comment.X;
-        _editingCommentEditorY = comment.Y;
+        _editingCommentEditorY = comment.Y + CommentHeaderHeight;
         _editingCommentEditorW = comment.Width;
-        _editingCommentEditorH = comment.Height;
+        _editingCommentEditorH = comment.Height - CommentHeaderHeight;
         _commentEditor.Text = comment.Name;   // Name returns the underlying Comment text.
         // Pick colours based on the active theme.
         bool isLight = Application.Current?.ActualThemeVariant == ThemeVariant.Light;
@@ -252,4 +254,75 @@ private void OnCommentEditorLostFocus(object? sender, Avalonia.Interactivity.Rou
         }
     }
 
+    // ── Inline comment header editor helpers ────────────────────────────
+
+    /// <summary>Shows the single-line header editor over the header band of <paramref name="comment"/>.</summary>
+    internal void BeginCommentHeaderEdit(CommentBlockViewModel comment)
+    {
+        CommitCommentEdit();
+        _editingCommentHeaderBlock = comment;
+        _editingCommentHeaderEditorX = comment.X;
+        _editingCommentHeaderEditorY = comment.Y;
+        // Leave room for the fold corner at the top-right.
+        _editingCommentHeaderEditorW = comment.Width - CommentFoldSize;
+        _editingCommentHeaderEditorH = CommentHeaderHeight;
+        _commentHeaderEditor.Text = comment.Header;
+        bool isLight = Application.Current?.ActualThemeVariant == ThemeVariant.Light;
+        _commentHeaderEditor.Foreground = isLight ? CommentTextBrush : Brushes.White;
+        _commentHeaderEditor.Background = isLight
+            ? new SolidColorBrush(Color.FromArgb(0xF2, 0xFF, 0xD5, 0x1A))
+            : new SolidColorBrush(Color.FromRgb(0x2A, 0x20, 0x00));
+        _commentHeaderEditor.IsVisible = true;
+        InvalidateMeasure();
+        Avalonia.Threading.Dispatcher.UIThread.Post(() =>
+        {
+            _commentHeaderEditor.Focus();
+            _commentHeaderEditor.SelectAll();
+        }, Avalonia.Threading.DispatcherPriority.Render);
+    }
+
+    /// <summary>Saves the header editor text and closes the editor.</summary>
+    internal void CommitCommentHeaderEdit()
+    {
+        if (_editingCommentHeaderBlock is null) return;
+        var comment = _editingCommentHeaderBlock;
+        var text = (_commentHeaderEditor.Text ?? string.Empty).Trim();
+        _editingCommentHeaderBlock = null;
+        _commentHeaderEditor.IsVisible = false;
+        comment.SetHeader(text);
+        InvalidateAndMeasure();
+    }
+
+    /// <summary>Discards the header edit without saving.</summary>
+    private void CancelCommentHeaderEdit()
+    {
+        _editingCommentHeaderBlock = null;
+        _commentHeaderEditor.IsVisible = false;
+        InvalidateAndMeasure();
+        Focus();
+    }
+
+    private void OnCommentHeaderEditorKeyDown(object? sender, KeyEventArgs e)
+    {
+        if (e.Key is Key.Return or Key.Enter)
+        {
+            CommitCommentHeaderEdit();
+            Focus();
+            e.Handled = true;
+        }
+        else if (e.Key == Key.Escape)
+        {
+            CancelCommentHeaderEdit();
+            e.Handled = true;
+        }
+    }
+
+    private void OnCommentHeaderEditorLostFocus(object? sender, Avalonia.Interactivity.RoutedEventArgs e)
+    {
+        if (_inDragOrResize) return;
+        if (_editingCommentHeaderBlock is not null)
+        {
+            CommitCommentHeaderEdit();
+        }
+    }
 }

src/XTMF2.GUI/Controls/ModelSystemCanvas/ModelSystemCanvas.ParamEditing.cs

@@ -751,9 +751,18 @@ private void SyncEditingElementPositions()
         if (_editingCommentBlock is not null)
         {
             _editingCommentEditorX = _editingCommentBlock.X;
-            _editingCommentEditorY = _editingCommentBlock.Y;
+            _editingCommentEditorY = _editingCommentBlock.Y + CommentHeaderHeight;
             _editingCommentEditorW = _editingCommentBlock.Width;
-            _editingCommentEditorH = _editingCommentBlock.Height;
+            _editingCommentEditorH = _editingCommentBlock.Height - CommentHeaderHeight;
+        }
+
+        // Sync comment header editor position/size if editing
+        if (_editingCommentHeaderBlock is not null)
+        {
+            _editingCommentHeaderEditorX = _editingCommentHeaderBlock.X;
+            _editingCommentHeaderEditorY = _editingCommentHeaderBlock.Y;
+            _editingCommentHeaderEditorW = _editingCommentHeaderBlock.Width - CommentFoldSize;
+            _editingCommentHeaderEditorH = CommentHeaderHeight;
         }
     }