feat: implement contour list display and entity loading

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest/Controls/ProgramEditorControl.cs

@@ -18,6 +18,10 @@ namespace OpenNest.Controls
         public ProgramEditorControl()
         {
             InitializeComponent();
+
+            contourList.DrawItem += OnDrawContourItem;
+            contourList.MeasureItem += OnMeasureContourItem;
+            contourList.SelectedIndexChanged += OnContourSelectionChanged;
         }
 
         public Program Program { get; private set; }
@@ -28,7 +32,21 @@ namespace OpenNest.Controls
 
         public void LoadEntities(List<Entity> entities)
         {
-            // Will be implemented in Task 3
+            var shapes = ShapeBuilder.GetShapes(entities);
+            if (shapes.Count == 0)
+            {
+                Clear();
+                return;
+            }
+
+            contours = ContourInfo.Classify(shapes);
+            Program = BuildProgram(contours);
+            isDirty = false;
+            isLoaded = true;
+
+            PopulateContourList();
+            UpdateGcodeText();
+            RefreshPreview();
         }
 
         public void Clear()
@@ -42,5 +60,123 @@ namespace OpenNest.Controls
             isDirty = false;
             isLoaded = false;
         }
+
+        private static Program BuildProgram(List<ContourInfo> contours)
+        {
+            var pgm = new Program();
+            foreach (var contour in contours)
+            {
+                var sub = ConvertGeometry.ToProgram(contour.Shape);
+                pgm.Merge(sub);
+            }
+            pgm.Mode = Mode.Incremental;
+            return pgm;
+        }
+
+        private void PopulateContourList()
+        {
+            contourList.Items.Clear();
+            foreach (var contour in contours)
+                contourList.Items.Add(contour);
+        }
+
+        private void UpdateGcodeText()
+        {
+            gcodeEditor.Text = Program?.ToString() ?? string.Empty;
+        }
+
+        private void RefreshPreview()
+        {
+            preview.ClearPenCache();
+            preview.Entities.Clear();
+
+            for (var i = 0; i < contours.Count; i++)
+            {
+                var contour = contours[i];
+                var selected = contourList.SelectedIndices.Contains(i);
+                var color = GetContourColor(contour.Type, selected);
+
+                foreach (var entity in contour.Shape.Entities)
+                {
+                    entity.Color = color;
+                    preview.Entities.Add(entity);
+                }
+            }
+
+            preview.ZoomToFit();
+            preview.Invalidate();
+        }
+
+        private static Color GetContourColor(ContourClassification type, bool selected)
+        {
+            if (selected)
+                return Color.White;
+
+            return type switch
+            {
+                ContourClassification.Perimeter => Color.FromArgb(80, 180, 120),
+                ContourClassification.Hole => Color.FromArgb(100, 140, 255),
+                ContourClassification.Etch => Color.FromArgb(255, 170, 50),
+                ContourClassification.Open => Color.FromArgb(200, 200, 100),
+                _ => Color.Gray,
+            };
+        }
+
+        private void OnMeasureContourItem(object sender, MeasureItemEventArgs e)
+        {
+            e.ItemHeight = 42;
+        }
+
+        private void OnDrawContourItem(object sender, DrawItemEventArgs e)
+        {
+            if (e.Index < 0 || e.Index >= contours.Count) return;
+
+            var contour = contours[e.Index];
+            var selected = (e.State & DrawItemState.Selected) != 0;
+            var bounds = e.Bounds;
+
+            // Background
+            using var bgBrush = new SolidBrush(selected
+                ? Color.FromArgb(230, 238, 255)
+                : Color.White);
+            e.Graphics.FillRectangle(bgBrush, bounds);
+
+            // Accent bar
+            var accentColor = GetContourColor(contour.Type, false);
+            using var accentBrush = new SolidBrush(accentColor);
+            e.Graphics.FillRectangle(accentBrush, bounds.X, bounds.Y + 4, 3, bounds.Height - 8);
+
+            // Direction icon
+            var icon = contour.Type switch
+            {
+                ContourClassification.Perimeter or ContourClassification.Hole =>
+                    contour.DirectionLabel == "CW" ? "\u21BB" : "\u21BA",
+                ContourClassification.Etch => "\u2014",
+                _ => "\u2014",
+            };
+            using var iconFont = new Font("Segoe UI", 14f);
+            using var iconBrush = new SolidBrush(accentColor);
+            e.Graphics.DrawString(icon, iconFont, iconBrush, bounds.X + 8, bounds.Y + 6);
+
+            // Label
+            using var labelFont = new Font("Segoe UI", 9f, FontStyle.Bold);
+            using var labelBrush = new SolidBrush(Color.FromArgb(40, 40, 40));
+            e.Graphics.DrawString(contour.Label, labelFont, labelBrush, bounds.X + 32, bounds.Y + 4);
+
+            // Info line
+            var info = $"{contour.DirectionLabel} \u00B7 {contour.DimensionLabel}";
+            using var infoFont = new Font("Segoe UI", 8f);
+            using var infoBrush = new SolidBrush(Color.Gray);
+            e.Graphics.DrawString(info, infoFont, infoBrush, bounds.X + 32, bounds.Y + 22);
+
+            // Separator
+            using var sepPen = new Pen(Color.FromArgb(230, 230, 230));
+            e.Graphics.DrawLine(sepPen, bounds.X + 8, bounds.Bottom - 1, bounds.Right - 8, bounds.Bottom - 1);
+        }
+
+        private void OnContourSelectionChanged(object sender, EventArgs e)
+        {
+            RefreshPreview();
+        }
     }
 }