From ad5f2a9041ee14d0a85aab00e0c8a9f5082d5b6b Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Sat, 31 Oct 2026 05:50:22 -0400
Subject: [PATCH] feat(cad-converter): add a Hole Table window that counts and
 colors holes by size

---
 OpenNest.Core/Dimensions/HoleTable.cs         | 105 ++++++++++++
 OpenNest.Tests/Dimensions/HoleTableTests.cs   | 101 ++++++++++++
 .../Forms/CadConverterHoleTableTests.cs       |  86 ++++++++++
 OpenNest/Controls/EntityView.Holes.cs         |  49 ++++++
 OpenNest/Controls/EntityView.cs               |   3 +-
 OpenNest/Forms/CadConverterForm.Designer.cs   |  16 ++
 OpenNest/Forms/CadConverterForm.cs            |  39 +++++
 OpenNest/Forms/HoleTableForm.cs               | 149 ++++++++++++++++++
 docs/dimensions.md                            |  19 +++
 9 files changed, 566 insertions(+), 1 deletion(-)
 create mode 100644 OpenNest.Core/Dimensions/HoleTable.cs
 create mode 100644 OpenNest.Tests/Dimensions/HoleTableTests.cs
 create mode 100644 OpenNest.WinForms.Tests/Forms/CadConverterHoleTableTests.cs
 create mode 100644 OpenNest/Controls/EntityView.Holes.cs
 create mode 100644 OpenNest/Forms/HoleTableForm.cs

diff --git a/OpenNest.Core/Dimensions/HoleTable.cs b/OpenNest.Core/Dimensions/HoleTable.cs
new file mode 100644
index 00000000..ff105ee3
--- /dev/null
+++ b/OpenNest.Core/Dimensions/HoleTable.cs
@@ -0,0 +1,105 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using OpenNest.Converters;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Dimensions
+{
+    /// <summary>One hole diameter in a <see cref="HoleTable"/> and every hole cut at that size.</summary>
+    public sealed class HoleSize
+    {
+        public HoleSize(double diameter, IReadOnlyList<Vector> centers, IReadOnlyList<Guid> entityIds)
+        {
+            Diameter = diameter;
+            Centers = centers;
+            EntityIds = entityIds;
+        }
+
+        /// <summary>The diameter, rounded to <see cref="HoleTable.Decimals"/> places.</summary>
+        public double Diameter { get; }
+
+        public int Quantity => Centers.Count;
+
+        public IReadOnlyList<Vector> Centers { get; }
+
+        /// <summary>The IDs of every entity that makes up a hole of this size.</summary>
+        public IReadOnlyList<Guid> EntityIds { get; }
+
+        public string DiameterText => "\u00D8" + Diameter.ToString("0.0000", System.Globalization.CultureInfo.InvariantCulture);
+    }
+
+    /// <summary>
+    /// Counts the round holes in a drawing by diameter. A round hole is a cut circle, or a closed
+    /// contour made only of arcs on one center and radius, that lies inside another cut contour, so
+    /// the outline of a round part is not a hole. Marks (scribe, etch, rapids, break cuts) are not
+    /// holes. Pass the entities as they will be cut (visible, with roles applied).
+    /// </summary>
+    public static class HoleTable
+    {
+        /// <summary>Holes whose diameters agree to this many decimal places share a row.</summary>
+        public const int Decimals = 4;
+
+        public static IReadOnlyList<HoleSize> Build(IEnumerable<Entity> entities)
+        {
+            var cut = entities
+                .Where(e => SpecialLayers.IsMaterial(e.Layer) && !ScribeLayerRepair.IsMarkLayer(e.Layer))
+                .ToList();
+            if (cut.Count == 0)
+                return Array.Empty<HoleSize>();
+
+            var shapes = ShapeBuilder.GetShapes(cut);
+            var holes = new List<(double Diameter, Vector Center, List<Guid> Ids)>();
+            foreach (var shape in shapes)
+            {
+                if (!TryRound(shape, out var center, out var radius))
+                    continue;
+                var box = shape.BoundingBox;
+                var area = box.Area();
+                if (!shapes.Any(other => !ReferenceEquals(other, shape)
+                        && other.BoundingBox.Area() > area + Tolerance.Epsilon
+                        && other.BoundingBox.Contains(box)))
+                    continue;
+                holes.Add((System.Math.Round(radius * 2, Decimals), center, shape.Entities.Select(e => e.Id).ToList()));
+            }
+
+            return holes
+                .GroupBy(h => h.Diameter)
+                .OrderBy(g => g.Key)
+                .Select(g => new HoleSize(
+                    g.Key,
+                    g.Select(h => h.Center).ToList(),
+                    g.SelectMany(h => h.Ids).ToList()))
+                .ToList();
+        }
+
+        private static bool TryRound(Shape shape, out Vector center, out double radius)
+        {
+            center = default;
+            radius = 0;
+            if (shape.Entities.Count == 1 && shape.Entities[0] is Circle circle)
+            {
+                center = circle.Center;
+                radius = circle.Radius;
+                return radius > 0;
+            }
+
+            if (shape.Entities.Count == 0 || !shape.Entities.All(e => e is Arc) || !shape.IsClosed())
+                return false;
+
+            var arcs = shape.Entities.Cast<Arc>().ToList();
+            var first = arcs[0];
+            var tolerance = Tolerance.ChainTolerance;
+            if (arcs.Any(a => a.Center.DistanceTo(first.Center) > tolerance
+                    || System.Math.Abs(a.Radius - first.Radius) > tolerance))
+                return false;
+            if (System.Math.Abs(arcs.Sum(a => a.SweepAngle()) - Angle.TwoPI) > 1e-6)
+                return false;
+
+            center = first.Center;
+            radius = first.Radius;
+            return radius > 0;
+        }
+    }
+}
diff --git a/OpenNest.Tests/Dimensions/HoleTableTests.cs b/OpenNest.Tests/Dimensions/HoleTableTests.cs
new file mode 100644
index 00000000..41bbc136
--- /dev/null
+++ b/OpenNest.Tests/Dimensions/HoleTableTests.cs
@@ -0,0 +1,101 @@
+using OpenNest.Dimensions;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Tests.Dimensions;
+
+public class HoleTableTests
+{
+    private static readonly Layer Cut = new("0") { IsVisible = true };
+
+    private static List<Entity> Rectangle(double width, double height) =>
+    [
+        new Line(0, 0, width, 0) { Layer = Cut },
+        new Line(width, 0, width, height) { Layer = Cut },
+        new Line(width, height, 0, height) { Layer = Cut },
+        new Line(0, height, 0, 0) { Layer = Cut },
+    ];
+
+    private static Circle Hole(double x, double y, double diameter, Layer layer = null) =>
+        new(x, y, diameter / 2) { Layer = layer ?? Cut };
+
+    [Fact]
+    public void Build_GroupsHolesByDiameter_SmallestFirst_WithEveryEntityId()
+    {
+        var a = Hole(1, 1, 0.5);
+        var b = Hole(3, 1, 0.5);
+        var c = Hole(5, 1, 0.25);
+        var entities = Rectangle(10, 4);
+        entities.AddRange([a, b, c]);
+
+        var table = HoleTable.Build(entities);
+
+        Assert.Equal(2, table.Count);
+        Assert.Equal(0.25, table[0].Diameter, 12);
+        Assert.Equal(1, table[0].Quantity);
+        Assert.Equal([c.Id], table[0].EntityIds);
+        Assert.Equal(0.5, table[1].Diameter, 12);
+        Assert.Equal(2, table[1].Quantity);
+        Assert.Equal(new[] { a.Id, b.Id }.Order(), table[1].EntityIds.Order());
+        Assert.Equal("\u00D80.5000", table[1].DiameterText);
+    }
+
+    [Fact]
+    public void Build_CountsAHoleDrawnAsTwoArcs_AsOneHole()
+    {
+        var top = new Arc(5, 2, 0.375, 0, Angle.ToRadians(180)) { Layer = Cut };
+        var bottom = new Arc(5, 2, 0.375, Angle.ToRadians(180), Angle.TwoPI) { Layer = Cut };
+        var entities = Rectangle(10, 4);
+        entities.AddRange([top, bottom]);
+
+        var table = HoleTable.Build(entities);
+
+        var size = Assert.Single(table);
+        Assert.Equal(0.75, size.Diameter, 12);
+        Assert.Equal(1, size.Quantity);
+        Assert.Equal(new[] { top.Id, bottom.Id }.Order(), size.EntityIds.Order());
+    }
+
+    [Fact]
+    public void Build_SharesARow_WhenDiametersAgreeToFourPlaces()
+    {
+        var entities = Rectangle(10, 4);
+        entities.AddRange([Hole(1, 1, 0.25001), Hole(3, 1, 0.24999), Hole(5, 1, 0.2502)]);
+
+        var table = HoleTable.Build(entities);
+
+        Assert.Equal([2, 1], table.Select(s => s.Quantity));
+        Assert.Equal(0.25, table[0].Diameter, 12);
+        Assert.Equal(0.2502, table[1].Diameter, 12);
+    }
+
+    [Fact]
+    public void Build_DoesNotCountTheOutlineOfARoundPart_OrMarks_OrSlots()
+    {
+        var outline = Hole(0, 0, 6);
+        var hole = Hole(0, 0, 1);
+        var etched = Hole(1.5, 0, 0.5, SpecialLayers.Scribe);
+        var slot = new List<Entity>
+        {
+            new Arc(-2, 1, 0.25, Angle.ToRadians(90), Angle.ToRadians(270)) { Layer = Cut },
+            new Line(-2, 0.75, -1, 0.75) { Layer = Cut },
+            new Arc(-1, 1, 0.25, Angle.ToRadians(270), Angle.ToRadians(90)) { Layer = Cut },
+            new Line(-1, 1.25, -2, 1.25) { Layer = Cut },
+        };
+        var entities = new List<Entity> { outline, hole, etched };
+        entities.AddRange(slot);
+
+        var table = HoleTable.Build(entities);
+
+        var size = Assert.Single(table);
+        Assert.Equal(1, size.Diameter, 12);
+        Assert.Equal([hole.Id], size.EntityIds);
+    }
+
+    [Fact]
+    public void Build_IsEmpty_WithNoGeometry()
+    {
+        Assert.Empty(HoleTable.Build([]));
+        Assert.Empty(HoleTable.Build(Rectangle(4, 4)));
+    }
+}
diff --git a/OpenNest.WinForms.Tests/Forms/CadConverterHoleTableTests.cs b/OpenNest.WinForms.Tests/Forms/CadConverterHoleTableTests.cs
new file mode 100644
index 00000000..8045a502
--- /dev/null
+++ b/OpenNest.WinForms.Tests/Forms/CadConverterHoleTableTests.cs
@@ -0,0 +1,86 @@
+using System.Drawing;
+using System.Reflection;
+using System.Windows.Forms;
+using OpenNest.Bending;
+using OpenNest.Controls;
+using OpenNest.Forms;
+using OpenNest.Geometry;
+using OpenNest.IO;
+
+namespace OpenNest.WinForms.Tests.Forms;
+
+/// <summary>
+/// The CAD Converter's Hole Table on a 10 x 6 plate with two 0.5 holes and one 0.25 hole.
+/// </summary>
+public class CadConverterHoleTableTests
+{
+    [Fact]
+    public void Holes_ListsEachSizeWithItsQuantity_AndColorsItsHolesOnTheView() => ArchUnitsTests.RunSta(() =>
+    {
+        using var form = new CadConverterForm();
+        Show(form);
+        form.LoadDrawings([Part()]);
+        var view = Field<EntityView>(form, "entityView1");
+        var item = Field<FileListControl>(form, "fileList").SelectedItem!;
+        var circles = item.Entities.OfType<Circle>().ToList();
+        var large = circles.Where(c => c.Radius > 0.2).Select(c => c.Id).ToList();
+        var small = circles.Single(c => c.Radius < 0.2).Id;
+
+        Assert.Null(view.HoleColors);
+        Field<Button>(form, "btnHoleTable").PerformClick();
+
+        var table = Assert.Single(form.OwnedForms.OfType<HoleTableForm>());
+        Assert.True(table.Visible);
+        var grid = table.Controls.OfType<DataGridView>().Single();
+        Assert.Equal(
+            new[] { ("\u00D80.2500", "1"), ("\u00D80.5000", "2") },
+            grid.Rows.Cast<DataGridViewRow>().Select(r => (r.Cells[1].Value!.ToString()!, r.Cells[2].Value!.ToString()!)));
+
+        // Each size's holes take its row's swatch color; the outline keeps its own.
+        Assert.Equal(3, view.HoleColors!.Count);
+        Assert.Equal(grid.Rows[0].Cells[0].Style.BackColor, view.HoleColors[small]);
+        Assert.All(large, id => Assert.Equal(grid.Rows[1].Cells[0].Style.BackColor, view.HoleColors[id]));
+        Assert.NotEqual(view.HoleColors[small], view.HoleColors[large[0]]);
+
+        // A hole set to Display is no longer cut, so it leaves the table.
+        Invoke(form, "OnEntityActionRequested", null,
+            new EntityActionEventArgs(EntityAction.Display, [circles.First(c => c.Id == large[0])]));
+        Assert.Equal("1", grid.Rows[1].Cells[2].Value!.ToString());
+        Assert.False(view.HoleColors.ContainsKey(large[0]));
+
+        // Closing the table restores the view's normal colors.
+        table.Close();
+        Application.DoEvents();
+        Assert.Null(view.HoleColors);
+        form.Close();
+    });
+
+    private static Drawing Part()
+    {
+        var entities = new List<Entity>
+        {
+            new Line(0, 0, 10, 0), new Line(10, 0, 10, 6), new Line(10, 6, 0, 6), new Line(0, 6, 0, 0),
+            new Circle(2, 3, 0.25), new Circle(5, 3, 0.25), new Circle(8, 3, 0.125),
+        };
+        var layer = new Layer("0") { IsVisible = true };
+        foreach (var e in entities)
+            e.Layer = layer;
+        return CadImporter.BuildDrawing(new CadImportResult { Entities = entities, Name = "holes" }, entities,
+            new List<Bend>(), 1, null, null);
+    }
+
+    private static void Show(Form form)
+    {
+        form.WindowState = FormWindowState.Normal;
+        form.StartPosition = FormStartPosition.Manual;
+        form.Location = new Point(0, 0);
+        form.Size = new System.Drawing.Size(1200, 800);
+        form.Show();
+    }
+
+    private static T Field<T>(object owner, string name) =>
+        (T)typeof(CadConverterForm).GetField(name, BindingFlags.Instance | BindingFlags.NonPublic)!.GetValue(owner)!;
+
+    private static void Invoke(CadConverterForm form, string name, params object?[] args) =>
+        typeof(CadConverterForm).GetMethod(name, BindingFlags.Instance | BindingFlags.NonPublic)!.Invoke(form, args);
+}
diff --git a/OpenNest/Controls/EntityView.Holes.cs b/OpenNest/Controls/EntityView.Holes.cs
new file mode 100644
index 00000000..9965fb6f
--- /dev/null
+++ b/OpenNest/Controls/EntityView.Holes.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using OpenNest.Geometry;
+
+namespace OpenNest.Controls
+{
+    public partial class EntityView
+    {
+        private const float HolePenWidth = 2.5f;
+        private readonly Dictionary<int, Pen> holePenCache = new Dictionary<int, Pen>();
+        private IReadOnlyDictionary<Guid, Color> holeColors;
+
+        /// <summary>
+        /// While the Hole Table is open, the color of each hole's entities by entity ID: holes are
+        /// drawn in their size's color with a heavier line. Null draws every entity normally.
+        /// </summary>
+        public IReadOnlyDictionary<Guid, Color> HoleColors
+        {
+            get => holeColors;
+            set
+            {
+                holeColors = value;
+                Invalidate();
+            }
+        }
+
+        private Pen HolePen(Entity entity)
+        {
+            if (holeColors == null || !holeColors.TryGetValue(entity.Id, out var color))
+                return null;
+
+            var argb = color.ToArgb();
+            if (!holePenCache.TryGetValue(argb, out var pen))
+            {
+                pen = new Pen(color, HolePenWidth);
+                holePenCache[argb] = pen;
+            }
+            return pen;
+        }
+
+        private void DisposeHolePens()
+        {
+            foreach (var pen in holePenCache.Values)
+                pen.Dispose();
+            holePenCache.Clear();
+        }
+    }
+}
diff --git a/OpenNest/Controls/EntityView.cs b/OpenNest/Controls/EntityView.cs
index 777fe5b8..aa3c7abc 100644
--- a/OpenNest/Controls/EntityView.cs
+++ b/OpenNest/Controls/EntityView.cs
@@ -142,7 +142,7 @@ namespace OpenNest.Controls
                     simplifierHighlightSet != null && simplifierHighlightSet.Contains(entity);
                 var pen = isHighlighted
                     ? GetEntityPen(Color.FromArgb(60, entity.Color))
-                    : GetEntityPen(entity.Color);
+                    : HolePen(entity) ?? GetEntityPen(entity.Color);
                 DrawEntity(e.Graphics, entity, pen);
             }
 
@@ -514,6 +514,7 @@ namespace OpenNest.Controls
             if (disposing)
             {
                 ClearPenCache();
+                DisposeHolePens();
                 gridPen.Dispose();
                 labelFont.Dispose();
                 dimensionFont.Dispose();
diff --git a/OpenNest/Forms/CadConverterForm.Designer.cs b/OpenNest/Forms/CadConverterForm.Designer.cs
index 70a1af1d..5740c793 100644
--- a/OpenNest/Forms/CadConverterForm.Designer.cs
+++ b/OpenNest/Forms/CadConverterForm.Designer.cs
@@ -32,6 +32,7 @@ namespace OpenNest.Forms
             btnSplit = new System.Windows.Forms.Button();
             btnSimplify = new System.Windows.Forms.Button();
             btnExportDxf = new System.Windows.Forms.Button();
+            btnHoleTable = new System.Windows.Forms.Button();
             chkShowOriginal = new System.Windows.Forms.CheckBox();
             chkLabels = new System.Windows.Forms.CheckBox();
             lblDetect = new System.Windows.Forms.Label();
@@ -171,6 +172,7 @@ namespace OpenNest.Forms
             detailBar.Controls.Add(btnSplit);
             detailBar.Controls.Add(btnSimplify);
             detailBar.Controls.Add(btnExportDxf);
+            detailBar.Controls.Add(btnHoleTable);
             detailBar.Controls.Add(chkShowOriginal);
             detailBar.Controls.Add(chkLabels);
             detailBar.Controls.Add(lblDetect);
@@ -286,6 +288,19 @@ namespace OpenNest.Forms
             btnExportDxf.Text = "Export DXF";
             btnExportDxf.Click += OnExportDxfClick;
             // 
+            // btnHoleTable
+            // 
+            btnHoleTable.AutoSize = true;
+            btnHoleTable.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
+            btnHoleTable.Font = new System.Drawing.Font("Segoe UI", 9F);
+            btnHoleTable.Location = new System.Drawing.Point(530, 6);
+            btnHoleTable.Margin = new System.Windows.Forms.Padding(0, 0, 10, 0);
+            btnHoleTable.Name = "btnHoleTable";
+            btnHoleTable.Size = new System.Drawing.Size(60, 27);
+            btnHoleTable.TabIndex = 8;
+            btnHoleTable.Text = "Holes...";
+            btnHoleTable.Click += OnHoleTableClick;
+            // 
             // chkShowOriginal
             // 
             chkShowOriginal.AutoSize = true;
@@ -431,6 +446,7 @@ namespace OpenNest.Forms
         private System.Windows.Forms.Button btnSplit;
         private System.Windows.Forms.Button btnSimplify;
         private System.Windows.Forms.Button btnExportDxf;
+        private System.Windows.Forms.Button btnHoleTable;
         private System.Windows.Forms.CheckBox chkShowOriginal;
         private System.Windows.Forms.CheckBox chkLabels;
         private System.Windows.Forms.ComboBox cboBendDetector;
diff --git a/OpenNest/Forms/CadConverterForm.cs b/OpenNest/Forms/CadConverterForm.cs
index 3dd9344f..46e5225c 100644
--- a/OpenNest/Forms/CadConverterForm.cs
+++ b/OpenNest/Forms/CadConverterForm.cs
@@ -263,6 +263,7 @@ namespace OpenNest.Forms
 
             entityView1.ZoomToFit();
             CheckSimplifiable(item);
+            RefreshHoleTable();
         }
 
         private void CheckSimplifiable(FileListItem item)
@@ -323,6 +324,7 @@ namespace OpenNest.Forms
             entityView1.Entities.Clear();
             entityView1.DimensionLayouts = Array.Empty<DimensionLayout>();
             entityView1.Invalidate();
+            RefreshHoleTable();
         }
 
         private void OnFilterChanged(object sender, EventArgs e)
@@ -337,6 +339,7 @@ namespace OpenNest.Forms
             SyncSuppressedState(item);
             RefreshBreakoffs(item);
             RefreshTabbedCutouts(item);
+            RefreshHoleTable();
             staleProgram = true;
         }
 
@@ -1287,6 +1290,42 @@ namespace OpenNest.Forms
 
             lblEntityCount.Text = $"{entities.Count} entities";
             ResetSimplifyButton();
+            RefreshHoleTable();
+        }
+
+        private HoleTableForm holeTable;
+
+        private void OnHoleTableClick(object sender, EventArgs e)
+        {
+            if (holeTable == null || holeTable.IsDisposed)
+            {
+                holeTable = new HoleTableForm();
+                var corner = entityView1.PointToScreen(new Point(entityView1.Width, 0));
+                holeTable.Location = new Point(corner.X - holeTable.Width - 12, corner.Y + 12);
+                holeTable.FormClosed += (_, _) =>
+                {
+                    holeTable = null;
+                    entityView1.HoleColors = null;
+                };
+                holeTable.Show(this);
+            }
+            else
+            {
+                holeTable.Activate();
+            }
+
+            RefreshHoleTable();
+        }
+
+        // Lists the current drawing's round holes as they will be cut and colors them on the view.
+        private void RefreshHoleTable()
+        {
+            if (holeTable == null || holeTable.IsDisposed)
+                return;
+
+            var item = CurrentItem;
+            var sizes = item == null ? Array.Empty<HoleSize>() : HoleTable.Build(VisibleEntities(item));
+            entityView1.HoleColors = holeTable.ShowSizes(sizes, item?.Name);
         }
 
         private void OnShowOriginalChanged(object sender, EventArgs e)
diff --git a/OpenNest/Forms/HoleTableForm.cs b/OpenNest/Forms/HoleTableForm.cs
new file mode 100644
index 00000000..fcfff7d3
--- /dev/null
+++ b/OpenNest/Forms/HoleTableForm.cs
@@ -0,0 +1,149 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Windows.Forms;
+using OpenNest.Dimensions;
+
+namespace OpenNest.Forms
+{
+    /// <summary>
+    /// A small tool window listing the current drawing's round holes by diameter, with the
+    /// quantity of each and the color its holes are drawn in on the CAD view.
+    /// </summary>
+    public class HoleTableForm : Form
+    {
+        // Bright on the CAD view's dark background and clear of the reserved colors: magenta
+        // (etch), cyan (display), yellow (bends) and white (ordinary cut entities).
+        private static readonly Color[] Palette =
+        {
+            Color.FromArgb(255, 85, 85),
+            Color.FromArgb(90, 220, 90),
+            Color.FromArgb(80, 160, 255),
+            Color.FromArgb(255, 170, 40),
+            Color.FromArgb(0, 205, 175),
+            Color.FromArgb(190, 140, 255),
+            Color.FromArgb(255, 140, 190),
+            Color.FromArgb(175, 215, 60),
+            Color.FromArgb(205, 135, 85),
+        };
+
+        private readonly DataGridView grid;
+        private readonly Label summary;
+
+        public HoleTableForm()
+        {
+            Text = "Hole Table";
+            FormBorderStyle = FormBorderStyle.SizableToolWindow;
+            ShowInTaskbar = false;
+            StartPosition = FormStartPosition.Manual;
+            Font = new Font("Segoe UI", 9F);
+            ClientSize = new Size(240, 260);
+            MinimumSize = new Size(200, 150);
+
+            grid = new DataGridView
+            {
+                Dock = DockStyle.Fill,
+                ReadOnly = true,
+                AllowUserToAddRows = false,
+                AllowUserToDeleteRows = false,
+                AllowUserToResizeRows = false,
+                RowHeadersVisible = false,
+                SelectionMode = DataGridViewSelectionMode.FullRowSelect,
+                AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill,
+                BackgroundColor = SystemColors.Window,
+                BorderStyle = BorderStyle.None,
+                TabStop = false,
+            };
+            grid.Columns.Add(new DataGridViewTextBoxColumn
+            {
+                Name = "Color",
+                HeaderText = "",
+                FillWeight = 20,
+                SortMode = DataGridViewColumnSortMode.NotSortable,
+            });
+            grid.Columns.Add(new DataGridViewTextBoxColumn
+            {
+                Name = "Size",
+                HeaderText = "Diameter",
+                FillWeight = 50,
+                SortMode = DataGridViewColumnSortMode.NotSortable,
+            });
+            grid.Columns.Add(new DataGridViewTextBoxColumn
+            {
+                Name = "Quantity",
+                HeaderText = "Qty",
+                FillWeight = 30,
+                SortMode = DataGridViewColumnSortMode.NotSortable,
+                DefaultCellStyle = { Alignment = DataGridViewContentAlignment.MiddleRight },
+            });
+
+            summary = new Label
+            {
+                Dock = DockStyle.Bottom,
+                Height = 40,
+                Padding = new Padding(4, 2, 4, 2),
+                ForeColor = SystemColors.GrayText,
+            };
+
+            Controls.Add(grid);
+            Controls.Add(summary);
+        }
+
+        /// <summary>The color of the hole size at <paramref name="index"/> in the table.</summary>
+        public static Color ColorFor(int index)
+        {
+            if (index < Palette.Length)
+                return Palette[index];
+
+            // Past the palette, step the hue by the golden angle so neighbors stay apart.
+            var hue = (index * 137.508) % 360;
+            return FromHsv(hue, 0.6, 1.0);
+        }
+
+        /// <summary>
+        /// Shows <paramref name="sizes"/> and returns each hole entity's color for the CAD view.
+        /// </summary>
+        public IReadOnlyDictionary<Guid, Color> ShowSizes(IReadOnlyList<HoleSize> sizes, string drawingName)
+        {
+            var colors = new Dictionary<Guid, Color>();
+            grid.Rows.Clear();
+            for (var i = 0; i < sizes.Count; i++)
+            {
+                var color = ColorFor(i);
+                var row = grid.Rows[grid.Rows.Add("", sizes[i].DiameterText, sizes[i].Quantity)];
+                var swatch = row.Cells[0].Style;
+                swatch.BackColor = color;
+                swatch.SelectionBackColor = color;
+                foreach (var id in sizes[i].EntityIds)
+                    colors[id] = color;
+            }
+            grid.ClearSelection();
+
+            var total = sizes.Sum(s => s.Quantity);
+            Text = string.IsNullOrEmpty(drawingName) ? "Hole Table" : $"Hole Table - {drawingName}";
+            summary.Text = sizes.Count == 0
+                ? "No round holes. Slots and other shapes are not listed."
+                : $"{total} hole{(total == 1 ? "" : "s")}, {sizes.Count} size{(sizes.Count == 1 ? "" : "s")}. "
+                    + "Round holes only, in drawing units.";
+            return colors;
+        }
+
+        private static Color FromHsv(double hue, double saturation, double value)
+        {
+            var c = value * saturation;
+            var x = c * (1 - System.Math.Abs((hue / 60) % 2 - 1));
+            var m = value - c;
+            var (r, g, b) = (int)(hue / 60) switch
+            {
+                0 => (c, x, 0.0),
+                1 => (x, c, 0.0),
+                2 => (0.0, c, x),
+                3 => (0.0, x, c),
+                4 => (x, 0.0, c),
+                _ => (c, 0.0, x),
+            };
+            return Color.FromArgb((int)((r + m) * 255), (int)((g + m) * 255), (int)((b + m) * 255));
+        }
+    }
+}
diff --git a/docs/dimensions.md b/docs/dimensions.md
index 6076439f..ce6fc5b1 100644
--- a/docs/dimensions.md
+++ b/docs/dimensions.md
@@ -50,4 +50,23 @@ they do not appear on plates, in PDFs or in DXF export.
   with an `R` prefix and diameter labels with `Ø`.
 - Split pieces start with no dimensions, like breakoffs and tabbed cutouts.
 
+## Hole table
+
+**Holes...** in the CAD Converter's bottom bar opens a small Hole Table window beside the
+view. It lists the drawing's round holes by diameter, smallest first, with the quantity of
+each and a color swatch. While it is open, every hole on the view is drawn in its size's color
+with a heavier line; closing the window restores the normal colors. The table follows the
+selected file and updates when entities are cut, etched, set to display, excluded or
+simplified.
+
+- A round hole is a cut circle, or a closed contour made only of arcs on one center and
+  radius, that lies inside another cut contour. The outline of a round part is not a hole.
+  Slots and other shapes are not listed.
+- Holes are read from the entities as they will be cut (visible, with roles applied), before
+  breakoffs and tabbed cutouts. Etched, display-only, excluded and hidden circles are not
+  listed.
+- Diameters are rounded to four decimals, in the drawing's units; holes that agree to four
+  decimals share a row. `HoleTable` (`OpenNest.Core/Dimensions`) builds the rows.
+- The table is a view only: it stores nothing in the drawing and never affects the program.
+
 File format: see [drawing dimensions](nest-file-format.md#drawing-dimensions).