Update Model System Editing

src/XTMF2.GUI/Controls/ScriptSyntaxOverlay.cs

@@ -0,0 +1,88 @@
+/*
+    Copyright 2026 University of Toronto
+
+    This file is part of XTMF2.
+
+    XTMF2 is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    XTMF2 is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with XTMF2.  If not, see <http://www.gnu.org/licenses/>.
+*/
+using System;
+using System.Globalization;
+using System.Text;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Media;
+
+namespace XTMF2.GUI.Controls;
+
+/// <summary>
+/// A transparent, non-interactive overlay control that paints syntax-highlighted
+/// tokens over the scripted-parameter <see cref="Avalonia.Controls.TextBox"/>. It is added to
+/// <see cref="Control.VisualChildren"/> after the TextBox so it renders on top of it.
+/// </summary>
+internal sealed class ScriptSyntaxOverlay : Control
+{
+    private static readonly Typeface OverlayTypeface = new("Segoe UI, Arial, sans-serif");
+
+    public (string text, IBrush brush)[] Tokens { get; set; } = Array.Empty<(string, IBrush)>();
+
+    /// <summary>
+    /// Scaled font size to use when drawing; updated by <see cref="ModelSystemCanvas.ArrangeOverride"/>
+    /// on every layout pass so the text matches the current zoom level.
+    /// </summary>
+    public double FontSize { get; set; } = 10.0;
+
+    public ScriptSyntaxOverlay()
+    {
+        IsHitTestVisible = false;
+        IsVisible        = false;
+    }
+
+    public override void Render(DrawingContext ctx)
+    {
+        if (Tokens.Length == 0) return;
+
+        // 4 px left-pad matches the TextBox inner padding so the first character
+        // lines up with the native cursor position.
+        const double leftPad = 4.0;
+
+        // Build the full expression string from all token segments so that
+        // Avalonia measures it in one pass.  Per-token width accumulation is
+        // unreliable: FormattedText.Width excludes trailing whitespace, so any
+        // whitespace-only token advances x by 0 and every subsequent token is
+        // shifted left.  Drawing as a single FormattedText with SetForegroundBrush
+        // span colouring avoids the issue entirely.
+        var sb = new StringBuilder();
+        foreach (var (seg, _) in Tokens)
+            sb.Append(seg);
+        string fullText = sb.ToString();
+
+        var ft = new FormattedText(
+            fullText,
+            CultureInfo.InvariantCulture,
+            FlowDirection.LeftToRight,
+            OverlayTypeface,
+            FontSize,
+            Brushes.White); // default; overridden per span below
+
+        int offset = 0;
+        foreach (var (seg, brush) in Tokens)
+        {
+            ft.SetForegroundBrush(brush, offset, seg.Length);
+            offset += seg.Length;
+        }
+
+        double ty = (Bounds.Height - ft.Height) / 2.0;
+        ctx.DrawText(ft, new Point(leftPad, ty));
+    }
+}

src/XTMF2.GUI/ViewModels/CommentBlockViewModel.cs

@@ -42,18 +42,23 @@ public sealed partial class CommentBlockViewModel : ObservableObject, ICanvasEle
     private readonly ModelSystemSession _session;
     private readonly User _user;
 
-    // ── Coordinates read directly from the underlying model ──────────────
+    // ── Coordinates read directly from the underlying model (or preview during drag) ─
+    private double? _previewX;
+    private double? _previewY;
+    private double? _previewW;
+    private double? _previewH;
+
     /// <inheritdoc/>
-    public double X => (double)UnderlyingBlock.Location.X;
+    public double X => _previewX ?? (double)UnderlyingBlock.Location.X;
 
     /// <inheritdoc/>
-    public double Y => (double)UnderlyingBlock.Location.Y;
+    public double Y => _previewY ?? (double)UnderlyingBlock.Location.Y;
 
     /// <summary>Rendered width; falls back to <see cref="DefaultWidth"/> when the model value is 0.</summary>
-    public double Width  => UnderlyingBlock.Location.Width  is 0 ? DefaultWidth  : (double)UnderlyingBlock.Location.Width;
+    public double Width  => _previewW ?? (UnderlyingBlock.Location.Width  is 0 ? DefaultWidth  : (double)UnderlyingBlock.Location.Width);
 
     /// <summary>Rendered height; falls back to <see cref="DefaultHeight"/> when the model value is 0.</summary>
-    public double Height => UnderlyingBlock.Location.Height is 0 ? DefaultHeight : (double)UnderlyingBlock.Location.Height;
+    public double Height => _previewH ?? (UnderlyingBlock.Location.Height is 0 ? DefaultHeight : (double)UnderlyingBlock.Location.Height);
 
     // ICanvasElement: Name maps to Comment so the property panel can reuse SelectedElementEditName.
     /// <inheritdoc/>
@@ -94,6 +99,34 @@ private void OnModelPropertyChanged(object? sender, PropertyChangedEventArgs e)
         }
     }
 
+    /// <summary>
+    /// Updates the visual position without touching the session (for drag preview).
+    /// Call <see cref="CommitMove"/> on mouse-up to persist the change.
+    /// </summary>
+    public void MoveToPreview(double x, double y)
+    {
+        _previewX = x;
+        _previewY = y;
+        OnPropertyChanged(nameof(X));
+        OnPropertyChanged(nameof(Y));
+        OnPropertyChanged(nameof(CenterX));
+        OnPropertyChanged(nameof(CenterY));
+    }
+
+    /// <summary>
+    /// Commits the current preview position to the session (call once on mouse-up).
+    /// Does nothing if no preview is active.
+    /// </summary>
+    public void CommitMove()
+    {
+        if (_previewX is null) return;
+        var x = _previewX.Value;
+        var y = _previewY!.Value;
+        _previewX = null;
+        _previewY = null;
+        MoveTo(x, y);
+    }
+
     /// <summary>
     /// Move the comment block to a new canvas position, persisting the change via the session
     /// (supports undo/redo).
@@ -108,6 +141,45 @@ public void MoveTo(double x, double y)
         // OnModelPropertyChanged("Location") fires automatically and propagates X/Y changes.
     }
 
+    /// <summary>
+    /// Update the comment text, persisting the change via the session (supports undo/redo).
+    /// Whitespace-only text is ignored.
+    /// </summary>
+    public void SetText(string text)
+    {
+        if (string.IsNullOrWhiteSpace(text)) return;
+        _session.SetCommentBlockText(_user, UnderlyingBlock, text, out _);
+    }
+
+    /// <summary>
+    /// Updates the visual size without touching the session (for resize-drag preview).
+    /// Call <see cref="CommitResize"/> on mouse-up to persist the change.
+    /// Width is clamped to a minimum of 60; height to a minimum of 30.
+    /// </summary>
+    public void ResizeToPreview(double w, double h)
+    {
+        _previewW = Math.Max(60.0, w);
+        _previewH = Math.Max(30.0, h);
+        OnPropertyChanged(nameof(Width));
+        OnPropertyChanged(nameof(Height));
+        OnPropertyChanged(nameof(CenterX));
+        OnPropertyChanged(nameof(CenterY));
+    }
+
+    /// <summary>
+    /// Commits the current preview size to the session (call once on mouse-up).
+    /// Does nothing if no resize preview is active.
+    /// </summary>
+    public void CommitResize()
+    {
+        if (_previewW is null) return;
+        var w = _previewW.Value;
+        var h = _previewH!.Value;
+        _previewW = null;
+        _previewH = null;
+        ResizeTo(w, h);
+    }
+
     /// <summary>
     /// Resize the comment block, persisting the change via the session (supports undo/redo).
     /// Width is clamped to a minimum of 60; height to a minimum of 30.

src/XTMF2.GUI/ViewModels/GhostNodeViewModel.cs

@@ -38,18 +38,23 @@ public sealed partial class GhostNodeViewModel : ObservableObject, ICanvasElemen
     private readonly ModelSystemSession _session;
     private readonly User _user;
 
-    // ── Coordinates read directly from the underlying model ──────────────
+    // ── Coordinates read directly from the underlying model (or preview during drag) ─
+    private double? _previewX;
+    private double? _previewY;
+    private double? _previewW;
+    private double? _previewH;
+
     /// <inheritdoc/>
-    public double X => (double)UnderlyingGhostNode.Location.X;
+    public double X => _previewX ?? (double)UnderlyingGhostNode.Location.X;
 
     /// <inheritdoc/>
-    public double Y => (double)UnderlyingGhostNode.Location.Y;
+    public double Y => _previewY ?? (double)UnderlyingGhostNode.Location.Y;
 
     /// <summary>Rendered width; falls back to 120 when the model value is 0.</summary>
-    public double Width  => UnderlyingGhostNode.Location.Width  is 0 ? 120.0 : (double)UnderlyingGhostNode.Location.Width;
+    public double Width  => _previewW ?? (UnderlyingGhostNode.Location.Width  is 0 ? 120.0 : (double)UnderlyingGhostNode.Location.Width);
 
     /// <summary>Rendered height; falls back to 50 when the model value is 0.</summary>
-    public double Height => UnderlyingGhostNode.Location.Height is 0 ? 50.0  : (double)UnderlyingGhostNode.Location.Height;
+    public double Height => _previewH ?? (UnderlyingGhostNode.Location.Height is 0 ? 50.0  : (double)UnderlyingGhostNode.Location.Height);
 
     /// <inheritdoc/>
     public double CenterX => X + Width / 2.0;
@@ -88,6 +93,34 @@ private void OnModelPropertyChanged(object? sender, PropertyChangedEventArgs e)
         }
     }
 
+    /// <summary>
+    /// Updates the visual position without touching the session (for drag preview).
+    /// Call <see cref="CommitMove"/> on mouse-up to persist the change.
+    /// </summary>
+    public void MoveToPreview(double x, double y)
+    {
+        _previewX = x;
+        _previewY = y;
+        OnPropertyChanged(nameof(X));
+        OnPropertyChanged(nameof(Y));
+        OnPropertyChanged(nameof(CenterX));
+        OnPropertyChanged(nameof(CenterY));
+    }
+
+    /// <summary>
+    /// Commits the current preview position to the session (call once on mouse-up).
+    /// Does nothing if no preview is active.
+    /// </summary>
+    public void CommitMove()
+    {
+        if (_previewX is null) return;
+        var x = _previewX.Value;
+        var y = _previewY!.Value;
+        _previewX = null;
+        _previewY = null;
+        MoveTo(x, y);
+    }
+
     /// <summary>
     /// Move the ghost node to a new canvas position, persisting via the session
     /// (supports undo/redo).
@@ -101,6 +134,35 @@ public void MoveTo(double x, double y)
             new Rectangle((float)x, (float)y, w, h), out _);
     }
 
+    /// <summary>
+    /// Updates the visual size without touching the session (for resize-drag preview).
+    /// Call <see cref="CommitResize"/> on mouse-up to persist the change.
+    /// Width is clamped to a minimum of 120; height to a minimum of 28.
+    /// </summary>
+    public void ResizeToPreview(double w, double h)
+    {
+        _previewW = Math.Max(120.0, w);
+        _previewH = Math.Max(28.0,  h);
+        OnPropertyChanged(nameof(Width));
+        OnPropertyChanged(nameof(Height));
+        OnPropertyChanged(nameof(CenterX));
+        OnPropertyChanged(nameof(CenterY));
+    }
+
+    /// <summary>
+    /// Commits the current preview size to the session (call once on mouse-up).
+    /// Does nothing if no resize preview is active.
+    /// </summary>
+    public void CommitResize()
+    {
+        if (_previewW is null) return;
+        var w = _previewW.Value;
+        var h = _previewH!.Value;
+        _previewW = null;
+        _previewH = null;
+        ResizeTo(w, h);
+    }
+
     /// <summary>
     /// Resize the ghost node, persisting via the session.
     /// Width is clamped to a minimum of 120; height to a minimum of 28.

src/XTMF2.GUI/ViewModels/ModelSystemEditorViewModel.cs

@@ -129,6 +129,31 @@ public string CurrentBoundaryLabel
     /// <summary>Observable view-models for the model system's variable list.</summary>
     public ObservableCollection<ModelSystemVariableViewModel> ModelSystemVariables { get; } = new();
 
+    /// <summary>Text typed into the variables filter box; filters <see cref="FilteredModelSystemVariables"/>.</summary>
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(FilteredModelSystemVariables))]
+    private string _variableFilter = string.Empty;
+
+    /// <summary>
+    /// Sorted (by name) and filtered (by <see cref="VariableFilter"/>) view of
+    /// <see cref="ModelSystemVariables"/>. Matches on name or boundary path.
+    /// </summary>
+    public IEnumerable<ModelSystemVariableViewModel> FilteredModelSystemVariables
+    {
+        get
+        {
+            var q = ModelSystemVariables.AsEnumerable();
+            if (!string.IsNullOrWhiteSpace(VariableFilter))
+            {
+                var f = VariableFilter.Trim();
+                q = q.Where(v =>
+                    v.Name.Contains(f, StringComparison.OrdinalIgnoreCase) ||
+                    v.BoundaryPath.Contains(f, StringComparison.OrdinalIgnoreCase));
+            }
+            return q.OrderBy(v => v.Name, StringComparer.OrdinalIgnoreCase);
+        }
+    }
+
     /// <summary>The currently selected link, if any. Mutually exclusive with <see cref="SelectedElement"/>.</summary>
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(NothingSelected))]
@@ -193,6 +218,12 @@ partial void OnNodeSearchSelectionChanged(NodeViewModel? value)
     /// </summary>
     public bool SelectedElementIsNode => SelectedElement is NodeViewModel;
 
+    /// <summary>True when the selected element is a <see cref="CommentBlockViewModel"/>.</summary>
+    public bool SelectedElementIsComment => SelectedElement is CommentBlockViewModel;
+
+    /// <summary>True when the selected element is NOT a <see cref="CommentBlockViewModel"/>, used to hide the rename box for comments.</summary>
+    public bool SelectedElementIsNotComment => SelectedElement is not CommentBlockViewModel;
+
     /// <summary>
     /// True when the selected node is a BasicParameter or ScriptedParameter,
     /// used to gate the parameter value editor in the property panel.
@@ -256,6 +287,8 @@ partial void OnSelectedElementChanged(ICanvasElement? value)
         OnPropertyChanged(nameof(SelectedElementFieldLabel));
         OnPropertyChanged(nameof(SelectedElementTypeName));
         OnPropertyChanged(nameof(SelectedElementIsNode));
+        OnPropertyChanged(nameof(SelectedElementIsComment));
+        OnPropertyChanged(nameof(SelectedElementIsNotComment));
         OnPropertyChanged(nameof(SelectedElementIsParameter));
         SelectedElementParameterValue =
             value is NodeViewModel pnvm && pnvm.IsParameterNode
@@ -1216,6 +1249,7 @@ private void OnModelSystemVariablesChanged(object? sender,
         // Full rebuild keeps the code simple; the list is expected to be small.
         SyncModelSystemVariables();
         OnPropertyChanged(nameof(HasNoModelSystemVariables));
+        OnPropertyChanged(nameof(FilteredModelSystemVariables));
     }
 
     /// <summary>Commit the name/comment currently in <see cref="SelectedElementEditName"/> back to the model.</summary>
@@ -1306,15 +1340,16 @@ private async Task RunModelSystem()
         }
         else
         {
-            // Multiple starts: ask the user to type the start name (listing the options).
-            var startList = string.Join(", ", availableStarts.Select(s => s.Name));
-            var startDialog = new InputDialog(
+            // Multiple starts: show a ComboBox so the user can pick one.
+            var startNames = availableStarts.Select(s => s.Name).ToList();
+            var startDialog = new StartPickerDialog(
                 title: "Select Start",
-                prompt: $"Available starts: {startList}\nEnter the start to execute:",
-                defaultText: availableStarts[0].Name);
+                prompt: "Select the start to execute:",
+                startNames: startNames,
+                defaultStart: startNames[0]);
             await startDialog.ShowDialog(ParentWindow);
             if (startDialog.WasCancelled) return;
-            startToExecute = startDialog.InputText?.Trim() ?? availableStarts[0].Name;
+            startToExecute = startDialog.SelectedStartName ?? startNames[0];
             if (string.IsNullOrEmpty(startToExecute)) return;
         }