fix: DetermineWinding used absolute area, always returned CCW

Shape.Area() returns Math.Abs(signedArea), so DetermineWinding always
detected CCW regardless of actual winding. Use ToPolygon().RotationDirection()
which uses the signed area correctly.

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

CLAUDE.md

@@ -24,10 +24,10 @@ Eight projects form a layered architecture:
 Domain model, geometry, and CNC primitives organized into namespaces:
 
 - **Root** (`namespace OpenNest`): Domain model — `Nest` → `Plate[]` → `Part[]` → `Drawing` → `Program`. A `Nest` is the top-level container. Each `Plate` has a size, material, quadrant, spacing, and contains placed `Part` instances. Each `Part` references a `Drawing` (the template) and has its own location/rotation. A `Drawing` wraps a CNC `Program`. Also contains utilities: `PartGeometry`, `Align`, `Sequence`, `Timing`.
-- **CNC** (`CNC/`, `namespace OpenNest.CNC`): `Program` holds a list of `ICode` instructions (G-code-like: `RapidMove`, `LinearMove`, `ArcMove`, `SubProgramCall`). Programs support absolute/incremental mode conversion, rotation, offset, bounding box calculation, and cloning.
+- **CNC** (`CNC/`, `namespace OpenNest.CNC`): `Program` holds a list of `ICode` instructions (G-code-like: `RapidMove`, `LinearMove`, `ArcMove`, `SubProgramCall`) and an optional `Variables` dictionary of `VariableDefinition` entries. Programs support absolute/incremental mode conversion, rotation, offset, bounding box calculation, and cloning. `VariableDefinition` stores a named variable's expression, resolved value, and flags (`Inline`, `Global`). `ProgramVariableManager` manages numbered machine variables for post-processor output.
 - **Geometry** (`Geometry/`, `namespace OpenNest.Geometry`): Spatial primitives (`Vector`, `Box`, `Size`, `Spacing`, `BoundingBox`, `IBoundable`) and higher-level shapes (`Line`, `Arc`, `Circle`, `Polygon`, `Shape`) used for intersection detection, area calculation, and DXF conversion. Also contains `Intersect` (intersection algorithms), `ShapeBuilder` (entity chaining), `GeometryOptimizer` (line/arc merging), `SpatialQuery` (directional distance, ray casting, box queries), `ShapeProfile` (perimeter/area analysis), `NoFitPolygon`, `InnerFitPolygon`, `ConvexHull`, `ConvexDecomposition`, `RotatingCalipers`, and `Collision` (overlap detection with Sutherland-Hodgman polygon clipping and hole subtraction).
 - **Converters** (`Converters/`, `namespace OpenNest.Converters`): Bridges between CNC and Geometry — `ConvertProgram` (CNC→Geometry), `ConvertGeometry` (Geometry→CNC), `ConvertMode` (absolute↔incremental).
-- **Math** (`Math/`, `namespace OpenNest.Math`): `Angle` (radian/degree conversion), `Tolerance` (floating-point comparison), `Trigonometry`, `Generic` (swap utility), `EvenOdd`, `Rounding` (factor-based rounding). Note: `OpenNest.Math` shadows `System.Math` — use `System.Math` fully qualified where both are needed.
+- **Math** (`Math/`, `namespace OpenNest.Math`): `Angle` (radian/degree conversion), `Tolerance` (floating-point comparison), `Trigonometry`, `Generic` (swap utility), `EvenOdd`, `Rounding` (factor-based rounding), `ExpressionEvaluator` (arithmetic expression parser for G-code variable expressions with `$name` references). Note: `OpenNest.Math` shadows `System.Math` — use `System.Math` fully qualified where both are needed.
 - **CNC/CuttingStrategy** (`CNC/CuttingStrategy/`, `namespace OpenNest.CNC`): `ContourCuttingStrategy` orchestrates cut ordering, lead-ins/lead-outs, and tabs. Includes `LeadIn`/`LeadOut` hierarchies (line, arc, clean-hole variants), `Tab` hierarchy (normal, machine, breaker), and `CuttingParameters`/`AssignmentParameters`/`SequenceParameters` configuration.
 - **Collections** (`Collections/`, `namespace OpenNest.Collections`): `ObservableList<T>`, `DrawingCollection`.
 - **CutOffs** (`namespace OpenNest`): `CutOff` (axis-aligned cut line with position, axis, optional start/end limits), `CutOffAxis` enum (`Horizontal`, `Vertical`), `CutOffSettings` (clearance, overtravel, min segment length, direction), `CutDirection` enum (`TowardOrigin`, `AwayFromOrigin`). Cut-offs generate CNC `Program` objects with trimmed line segments that avoid parts.
@@ -116,3 +116,4 @@ Always keep `README.md` and `CLAUDE.md` up to date when making changes that affe
 - `Compactor` performs post-fill gravity compaction — after filling, parts are pushed toward a plate edge using directional distance calculations to close gaps between irregular shapes.
 - `FillScore` uses lexicographic comparison (count > utilization > compactness) to rank fill results consistently across all fill strategies.
 - **Cut-off materialization lifecycle**: `CutOff` objects live on `Plate.CutOffs`. Each generates a `Drawing` (with `IsCutOff = true`) whose `Program` contains trimmed line segments. `Plate.RegenerateCutOffs(settings)` removes old cut-off Parts, recomputes programs, and re-adds them to `Plate.Parts`. Regeneration triggers: cut-off add/remove/move, part drag complete, fill complete, plate transform. Cut-off Parts are excluded from quantity tracking, utilization, overlap detection, and nest file serialization (programs are regenerated from definitions on load).
+- **User-defined G-code variables**: Programs can contain named variable definitions (`name = expression [inline] [global]`) referenced in coordinates with `$name`. Variables resolve to doubles at parse time for geometry/nesting. `VariableRefs` on `Motion`/`Feedrate` track the symbolic link so post processors can emit machine variable references. Cincinnati post maps non-inline variables to numbered machine variables (`#200+`) with descriptive comments. Global variables share a number across programs; local variables get per-drawing numbers. `ProgramReader` uses a two-pass parse (collect definitions, then parse G-code with substitution). `NestWriter` serializes definitions and `$references` back to text for round-trip fidelity.

OpenNest.Core/CNC/CuttingStrategy/ContourCuttingStrategy.cs

@@ -70,8 +70,8 @@ namespace OpenNest.CNC.CuttingStrategy
         private void EmitContour(Program program, Shape shape, Vector point, Entity entity, ContourType? forceType = null)
         {
             var contourType = forceType ?? DetectContourType(shape);
-            var normal = ComputeNormal(point, entity, contourType);
             var winding = DetermineWinding(shape);
+            var normal = ComputeNormal(point, entity, contourType, winding);
 
             var leadIn = SelectLeadIn(contourType);
             var leadOut = SelectLeadOut(contourType);
@@ -143,29 +143,33 @@ namespace OpenNest.CNC.CuttingStrategy
             return ContourType.Internal;
         }
 
-        public static double ComputeNormal(Vector point, Entity entity, ContourType contourType)
+        public static double ComputeNormal(Vector point, Entity entity, ContourType contourType,
+            RotationType winding = RotationType.CW)
         {
             double normal;
 
             if (entity is Line line)
             {
-                // Perpendicular to line direction
+                // Perpendicular to line direction: tangent + π/2 = left side.
+                // Left side = outward for CW winding; for CCW winding, outward
+                // is on the right side, so flip.
                 var tangent = line.EndPoint.AngleFrom(line.StartPoint);
                 normal = tangent + Math.Angle.HalfPI;
+                if (winding == RotationType.CCW)
+                    normal += System.Math.PI;
             }
             else if (entity is Arc arc)
             {
-                // Radial direction from center to point
+                // Radial direction from center to point.
+                // Flip when the arc direction differs from the contour winding —
+                // that indicates a concave feature where radial points inward.
                 normal = point.AngleFrom(arc.Center);
-
-                // For CCW arcs the radial points the wrong way — flip it.
-                // CW arcs are convex features (corners) where radial = outward.
-                // CCW arcs are concave features (slots) where radial = inward.
-                if (arc.Rotation == RotationType.CCW)
+                if (arc.Rotation != winding)
                     normal += System.Math.PI;
             }
             else if (entity is Circle circle)
             {
+                // Radial outward — always correct regardless of winding
                 normal = point.AngleFrom(circle.Center);
             }
             else
@@ -182,9 +186,10 @@ namespace OpenNest.CNC.CuttingStrategy
 
         public static RotationType DetermineWinding(Shape shape)
         {
-            // Use signed area: positive = CCW, negative = CW
-            var area = shape.Area();
-            return area >= 0 ? RotationType.CCW : RotationType.CW;
+            if (shape.Entities.Count == 1 && shape.Entities[0] is Circle circle)
+                return circle.Rotation;
+
+            return shape.ToPolygon().RotationDirection();
         }
 
         private LeadIn ClampLeadInForCircle(LeadIn leadIn, Circle circle, Vector contourPoint, double normalAngle)

OpenNest.Core/CNC/Program.cs

@@ -1,6 +1,7 @@
 using OpenNest.Converters;
 using OpenNest.Geometry;
 using OpenNest.Math;
+using System;
 using System.Collections.Generic;
 
 namespace OpenNest.CNC
@@ -9,6 +10,8 @@ namespace OpenNest.CNC
     {
         public List<ICode> Codes;
 
+        public Dictionary<string, VariableDefinition> Variables { get; } = new(StringComparer.OrdinalIgnoreCase);
+
         private Mode mode;
 
         public Program(Mode mode = Mode.Absolute)
@@ -454,6 +457,9 @@ namespace OpenNest.CNC
 
             pgm.Codes.AddRange(codes);
 
+            foreach (var kvp in Variables)
+                pgm.Variables[kvp.Key] = kvp.Value;
+
             return pgm;
         }
 

OpenNest.IO/NestWriter.cs

@@ -305,6 +305,15 @@ namespace OpenNest.IO
             var writer = new StreamWriter(stream);
             writer.AutoFlush = true;
 
+            // Emit variable definitions before G-code
+            foreach (var v in program.Variables.Values)
+            {
+                var line = $"{v.Name} = {v.Expression}";
+                if (v.Inline) line += " inline";
+                if (v.Global) line += " global";
+                writer.WriteLine(line);
+            }
+
             writer.WriteLine(program.Mode == Mode.Absolute ? "G90" : "G91");
 
             for (var i = 0; i < drawing.Program.Length; ++i)
@@ -316,6 +325,13 @@ namespace OpenNest.IO
             stream.Position = 0;
         }
 
+        private string FormatCoord(double value, string axis, Dictionary<string, string> variableRefs)
+        {
+            if (variableRefs != null && variableRefs.TryGetValue(axis, out var varName))
+                return $"${varName}";
+            return System.Math.Round(value, OutputPrecision).ToString(CoordinateFormat);
+        }
+
         private string GetCodeString(ICode code)
         {
             switch (code.Type)
@@ -324,16 +340,16 @@ namespace OpenNest.IO
                     {
                         var sb = new StringBuilder();
                         var arcMove = (ArcMove)code;
+                        var refs = arcMove.VariableRefs;
 
-                        var x = System.Math.Round(arcMove.EndPoint.X, OutputPrecision).ToString(CoordinateFormat);
-                        var y = System.Math.Round(arcMove.EndPoint.Y, OutputPrecision).ToString(CoordinateFormat);
-                        var i = System.Math.Round(arcMove.CenterPoint.X, OutputPrecision).ToString(CoordinateFormat);
-                        var j = System.Math.Round(arcMove.CenterPoint.Y, OutputPrecision).ToString(CoordinateFormat);
+                        var x = FormatCoord(arcMove.EndPoint.X, "X", refs);
+                        var y = FormatCoord(arcMove.EndPoint.Y, "Y", refs);
+                        var i = FormatCoord(arcMove.CenterPoint.X, "I", refs);
+                        var j = FormatCoord(arcMove.CenterPoint.Y, "J", refs);
 
-                        if (arcMove.Rotation == RotationType.CW)
-                            sb.Append(string.Format("G02X{0}Y{1}I{2}J{3}", x, y, i, j));
-                        else
-                            sb.Append(string.Format("G03X{0}Y{1}I{2}J{3}", x, y, i, j));
+                        sb.Append(arcMove.Rotation == RotationType.CW
+                            ? $"G02X{x}Y{y}I{i}J{j}"
+                            : $"G03X{x}Y{y}I{i}J{j}");
 
                         if (arcMove.Layer != LayerType.Cut)
                             sb.Append(GetLayerString(arcMove.Layer));
@@ -354,10 +370,9 @@ namespace OpenNest.IO
                     {
                         var sb = new StringBuilder();
                         var linearMove = (LinearMove)code;
+                        var refs = linearMove.VariableRefs;
 
-                        sb.Append(string.Format("G01X{0}Y{1}",
-                            System.Math.Round(linearMove.EndPoint.X, OutputPrecision).ToString(CoordinateFormat),
-                            System.Math.Round(linearMove.EndPoint.Y, OutputPrecision).ToString(CoordinateFormat)));
+                        sb.Append($"G01X{FormatCoord(linearMove.EndPoint.X, "X", refs)}Y{FormatCoord(linearMove.EndPoint.Y, "Y", refs)}");
 
                         if (linearMove.Layer != LayerType.Cut)
                             sb.Append(GetLayerString(linearMove.Layer));
@@ -371,15 +386,16 @@ namespace OpenNest.IO
                 case CodeType.RapidMove:
                     {
                         var rapidMove = (RapidMove)code;
+                        var refs = rapidMove.VariableRefs;
 
-                        return string.Format("G00X{0}Y{1}",
-                            System.Math.Round(rapidMove.EndPoint.X, OutputPrecision).ToString(CoordinateFormat),
-                            System.Math.Round(rapidMove.EndPoint.Y, OutputPrecision).ToString(CoordinateFormat));
+                        return $"G00X{FormatCoord(rapidMove.EndPoint.X, "X", refs)}Y{FormatCoord(rapidMove.EndPoint.Y, "Y", refs)}";
                     }
 
                 case CodeType.SetFeedrate:
                     {
                         var setFeedrate = (Feedrate)code;
+                        if (setFeedrate.VariableRef != null)
+                            return $"F${setFeedrate.VariableRef}";
                         return "F" + setFeedrate.Value;
                     }
 

OpenNest.IO/ProgramReader.cs

@@ -1,7 +1,11 @@
 using OpenNest.CNC;
 using OpenNest.Geometry;
+using OpenNest.Math;
+using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Text;
 
 namespace OpenNest.IO
@@ -15,6 +19,7 @@ namespace OpenNest.IO
         private CodeSection section;
         private Program program;
         private StreamReader reader;
+        private Dictionary<string, double> resolvedVariables;
 
         public ProgramReader(Stream stream)
         {
@@ -24,11 +29,38 @@ namespace OpenNest.IO
 
         public Program Read()
         {
+            // First pass: read all lines, collect variable definitions
+            var allLines = new List<string>();
+            var variableDefs = new Dictionary<string, (string expression, bool inline, bool global)>(
+                StringComparer.OrdinalIgnoreCase);
+            var codeLines = new List<string>();
             string line;
 
             while ((line = reader.ReadLine()) != null)
             {
-                block = ParseBlock(line);
+                allLines.Add(line);
+                if (TryParseVariableDefinition(line, out var name, out var expression, out var isInline, out var isGlobal))
+                    variableDefs[name] = (expression, isInline, isGlobal);
+                else
+                    codeLines.Add(line);
+            }
+
+            // Evaluate variables with topological sort for dependency ordering
+            resolvedVariables = ResolveVariables(variableDefs);
+
+            // Store evaluated variables on the program
+            foreach (var kvp in variableDefs)
+            {
+                var name = kvp.Key;
+                var (expression, isInline, isGlobal) = kvp.Value;
+                var value = resolvedVariables[name];
+                program.Variables[name] = new VariableDefinition(name, expression, value, isInline, isGlobal);
+            }
+
+            // Second pass: parse G-code lines with variable substitution
+            foreach (var codeLine in codeLines)
+            {
+                block = ParseBlock(codeLine);
                 ProcessCurrentBlock();
             }
 
@@ -39,10 +71,43 @@ namespace OpenNest.IO
         {
             var block = new CodeBlock();
             Code code = null;
-            for (int i = 0; i < line.Length; ++i)
+            for (var i = 0; i < line.Length; ++i)
             {
                 var c = line[i];
-                if (char.IsLetter(c))
+                if (c == '$' && code != null && resolvedVariables != null)
+                {
+                    // Read the maximal variable name (letters, digits, underscores)
+                    var start = i + 1;
+                    while (start < line.Length && (char.IsLetterOrDigit(line[start]) || line[start] == '_'))
+                        start++;
+                    var maxName = line.Substring(i + 1, start - i - 1);
+
+                    // Try longest match first, then progressively shorter to handle
+                    // cases like X$widthY0 where "widthY" isn't a variable but "width" is
+                    string lookupKey = null;
+                    var nameLen = maxName.Length;
+                    while (nameLen > 0)
+                    {
+                        var candidate = maxName.Substring(0, nameLen);
+                        lookupKey = resolvedVariables.Keys
+                            .FirstOrDefault(k => string.Equals(k, candidate, StringComparison.OrdinalIgnoreCase));
+                        if (lookupKey != null)
+                            break;
+                        nameLen--;
+                    }
+
+                    if (lookupKey != null)
+                    {
+                        code.Value = resolvedVariables[lookupKey].ToString(CultureInfo.InvariantCulture);
+                        code.VariableRef = lookupKey;
+                        i += nameLen; // advance past the matched variable name
+                    }
+                    else
+                    {
+                        i = start - 1; // no match, skip the whole thing
+                    }
+                }
+                else if (char.IsLetter(c))
                     block.Add((code = new Code(c)));
                 else if (c == ':')
                 {
@@ -125,7 +190,10 @@ namespace OpenNest.IO
                         break;
 
                     case 'F':
-                        program.Codes.Add(new Feedrate() { Value = double.Parse(code.Value) });
+                        var feedrate = new Feedrate() { Value = double.Parse(code.Value) };
+                        if (code.VariableRef != null)
+                            feedrate.VariableRef = code.VariableRef;
+                        program.Codes.Add(feedrate);
                         code = GetNextCode();
                         break;
 
@@ -143,6 +211,7 @@ namespace OpenNest.IO
             double y = 0;
             var layer = LayerType.Cut;
             var suppressed = false;
+            string xRef = null, yRef = null;
 
             while (section == CodeSection.Line)
             {
@@ -157,10 +226,12 @@ namespace OpenNest.IO
                 {
                     case 'X':
                         x = double.Parse(code.Value);
+                        xRef = code.VariableRef;
                         break;
 
                     case 'Y':
                         y = double.Parse(code.Value);
+                        yRef = code.VariableRef;
                         break;
 
                     case ':':
@@ -200,10 +271,13 @@ namespace OpenNest.IO
                         break;
                 }
             }
+
+            var refs = BuildVariableRefs(("X", xRef), ("Y", yRef));
+
             if (isRapid)
-                program.Codes.Add(new RapidMove(x, y));
+                program.Codes.Add(new RapidMove(x, y) { VariableRefs = refs });
             else
-                program.Codes.Add(new LinearMove(x, y) { Layer = layer, Suppressed = suppressed });
+                program.Codes.Add(new LinearMove(x, y) { Layer = layer, Suppressed = suppressed, VariableRefs = refs });
         }
 
         private void ReadArc(RotationType rotation)
@@ -214,6 +288,7 @@ namespace OpenNest.IO
             double j = 0;
             var layer = LayerType.Cut;
             var suppressed = false;
+            string xRef = null, yRef = null, iRef = null, jRef = null;
 
             while (section == CodeSection.Arc)
             {
@@ -229,18 +304,22 @@ namespace OpenNest.IO
                 {
                     case 'X':
                         x = double.Parse(code.Value);
+                        xRef = code.VariableRef;
                         break;
 
                     case 'Y':
                         y = double.Parse(code.Value);
+                        yRef = code.VariableRef;
                         break;
 
                     case 'I':
                         i = double.Parse(code.Value);
+                        iRef = code.VariableRef;
                         break;
 
                     case 'J':
                         j = double.Parse(code.Value);
+                        jRef = code.VariableRef;
                         break;
 
                     case ':':
@@ -286,7 +365,8 @@ namespace OpenNest.IO
                 CenterPoint = new Vector(i, j),
                 Rotation = rotation,
                 Layer = layer,
-                Suppressed = suppressed
+                Suppressed = suppressed,
+                VariableRefs = BuildVariableRefs(("X", xRef), ("Y", yRef), ("I", iRef), ("J", jRef))
             });
         }
 
@@ -351,6 +431,179 @@ namespace OpenNest.IO
             return block[codeIndex];
         }
 
+        private static bool TryParseVariableDefinition(string line, out string name, out string expression,
+            out bool isInline, out bool isGlobal)
+        {
+            name = null;
+            expression = null;
+            isInline = false;
+            isGlobal = false;
+
+            var trimmed = line.Trim();
+            if (trimmed.Length == 0)
+                return false;
+
+            // Must start with a letter or underscore (not a G-code letter followed by a digit)
+            var firstChar = trimmed[0];
+            if (!char.IsLetter(firstChar) && firstChar != '_')
+                return false;
+
+            // If line starts with a known G-code letter followed by a digit, it's not a variable
+            if (trimmed.Length >= 2 && char.IsDigit(trimmed[1]))
+            {
+                var upper = char.ToUpper(firstChar);
+                if (upper is 'G' or 'M' or 'N' or 'F' or 'X' or 'Y' or 'I' or 'J' or 'T' or 'S' or 'O' or 'P' or 'R')
+                    return false;
+            }
+
+            // Must contain '='
+            var eqIndex = trimmed.IndexOf('=');
+            if (eqIndex < 1)
+                return false;
+
+            // Extract name (everything before '=', trimmed)
+            var rawName = trimmed.Substring(0, eqIndex).Trim();
+
+            // Validate name: must be identifier (letter/underscore followed by alphanumeric/underscore)
+            if (rawName.Length == 0 || (!char.IsLetter(rawName[0]) && rawName[0] != '_'))
+                return false;
+            for (var i = 1; i < rawName.Length; i++)
+            {
+                if (!char.IsLetterOrDigit(rawName[i]) && rawName[i] != '_')
+                    return false;
+            }
+
+            // Extract expression and flags from the remainder after '='
+            var remainder = trimmed.Substring(eqIndex + 1).Trim();
+
+            // Check for trailing flags: inline and/or global
+            // Parse from the end to separate expression from flags
+            var words = remainder.Split(' ', StringSplitOptions.RemoveEmptyEntries);
+            var flagStart = words.Length;
+            for (var i = words.Length - 1; i >= 0; i--)
+            {
+                var word = words[i].ToLowerInvariant();
+                if (word == "inline" || word == "global")
+                    flagStart = i;
+                else
+                    break;
+            }
+
+            // Build expression from non-flag words
+            var expressionParts = words.Take(flagStart).ToArray();
+            if (expressionParts.Length == 0)
+                return false;
+
+            expression = string.Join(" ", expressionParts);
+
+            // Parse flags
+            for (var i = flagStart; i < words.Length; i++)
+            {
+                var word = words[i].ToLowerInvariant();
+                if (word == "inline") isInline = true;
+                else if (word == "global") isGlobal = true;
+            }
+
+            name = rawName;
+            return true;
+        }
+
+        private static Dictionary<string, double> ResolveVariables(
+            Dictionary<string, (string expression, bool inline, bool global)> variableDefs)
+        {
+            if (variableDefs.Count == 0)
+                return new Dictionary<string, double>(StringComparer.OrdinalIgnoreCase);
+
+            // Build dependency graph
+            var dependencies = new Dictionary<string, List<string>>(StringComparer.OrdinalIgnoreCase);
+            foreach (var kvp in variableDefs)
+            {
+                var deps = new List<string>();
+                var expr = kvp.Value.expression;
+                for (var i = 0; i < expr.Length; i++)
+                {
+                    if (expr[i] == '$')
+                    {
+                        var start = i + 1;
+                        while (start < expr.Length && (char.IsLetterOrDigit(expr[start]) || expr[start] == '_'))
+                            start++;
+                        var refName = expr.Substring(i + 1, start - i - 1);
+                        // Find the canonical name (case-insensitive match)
+                        var canonical = variableDefs.Keys
+                            .FirstOrDefault(k => string.Equals(k, refName, StringComparison.OrdinalIgnoreCase));
+                        if (canonical != null)
+                            deps.Add(canonical);
+                        i = start - 1;
+                    }
+                }
+                dependencies[kvp.Key] = deps;
+            }
+
+            // Topological sort (Kahn's algorithm)
+            var inDegree = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+            foreach (var name in variableDefs.Keys)
+                inDegree[name] = 0;
+            foreach (var kvp in dependencies)
+            {
+                foreach (var dep in kvp.Value)
+                {
+                    if (inDegree.ContainsKey(dep))
+                        inDegree[kvp.Key]++;
+                }
+            }
+
+            var queue = new Queue<string>();
+            foreach (var kvp in inDegree)
+            {
+                if (kvp.Value == 0)
+                    queue.Enqueue(kvp.Key);
+            }
+
+            var resolved = new Dictionary<string, double>(StringComparer.OrdinalIgnoreCase);
+            var order = new List<string>();
+
+            while (queue.Count > 0)
+            {
+                var current = queue.Dequeue();
+                order.Add(current);
+
+                // Evaluate this variable
+                var expr = variableDefs[current].expression;
+                var value = ExpressionEvaluator.Evaluate(expr, resolved);
+                resolved[current] = value;
+
+                // Reduce in-degree of dependents
+                foreach (var kvp in dependencies)
+                {
+                    if (kvp.Value.Contains(current, StringComparer.OrdinalIgnoreCase))
+                    {
+                        inDegree[kvp.Key]--;
+                        if (inDegree[kvp.Key] == 0 && !order.Contains(kvp.Key))
+                            queue.Enqueue(kvp.Key);
+                    }
+                }
+            }
+
+            if (order.Count != variableDefs.Count)
+                throw new InvalidOperationException("Circular dependency detected among variables.");
+
+            return resolved;
+        }
+
+        private static Dictionary<string, string> BuildVariableRefs(params (string axis, string varRef)[] refs)
+        {
+            Dictionary<string, string> result = null;
+            foreach (var (axis, varRef) in refs)
+            {
+                if (varRef != null)
+                {
+                    result ??= new Dictionary<string, string>();
+                    result[axis] = varRef;
+                }
+            }
+            return result;
+        }
+
         public void Close()
         {
             reader.Close();
@@ -374,6 +627,8 @@ namespace OpenNest.IO
 
             public string Value { get; set; }
 
+            public string VariableRef { get; set; }
+
             public override string ToString()
             {
                 return Id + Value;

OpenNest.Posts.Cincinnati/CincinnatiFeatureWriter.cs

@@ -29,6 +29,29 @@ public sealed class FeatureContext
     /// so part-relative programs become plate-absolute under G90.
     /// </summary>
     public Vector PartLocation { get; set; } = Vector.Zero;
+
+    /// <summary>
+    /// Maps (drawingId, variableName) to assigned machine variable numbers.
+    /// Used to emit #number references instead of literal values for user variables.
+    /// </summary>
+    public Dictionary<(int drawingId, string varName), int> UserVariableMapping { get; set; }
+
+    /// <summary>
+    /// The drawing ID for the current part, used to look up user variable mappings.
+    /// </summary>
+    public int DrawingId { get; set; }
+
+    /// <summary>
+    /// True if this feature is a cut-off line. Used to substitute plate-edge
+    /// coordinates with sheet width/length variables.
+    /// </summary>
+    public bool IsCutOff { get; set; }
+
+    /// <summary>Plate width (Y extent for vertical cutoffs).</summary>
+    public double PlateWidth { get; set; }
+
+    /// <summary>Plate length (X extent for horizontal cutoffs).</summary>
+    public double PlateLength { get; set; }
 }
 
 /// <summary>
@@ -63,7 +86,7 @@ public sealed class CincinnatiFeatureWriter
         var piercePoint = FindPiercePoint(ctx.Codes);
 
         // 1. Rapid to pierce point (with line number if configured)
-        WriteRapidToPierce(writer, ctx.FeatureNumber, piercePoint, offset);
+        WriteRapidToPierce(writer, ctx, piercePoint, offset);
 
         // 2. Part name comment on first feature of each part
         if (ctx.IsFirstFeatureOfPart && !string.IsNullOrEmpty(ctx.PartName))
@@ -112,7 +135,9 @@ public sealed class CincinnatiFeatureWriter
                     kerfEmitted = true;
                 }
 
-                sb.Append($"G1 X{_fmt.FormatCoord(linear.EndPoint.X + offset.X)} Y{_fmt.FormatCoord(linear.EndPoint.Y + offset.Y)}");
+                var xCoord = FormatCoordWithVars(linear.EndPoint.X + offset.X, "X", linear.VariableRefs, ctx);
+                var yCoord = FormatCoordWithVars(linear.EndPoint.Y + offset.Y, "Y", linear.VariableRefs, ctx);
+                sb.Append($"G1 X{xCoord} Y{yCoord}");
 
                 // Feedrate — etch always uses process feedrate
                 var feedVar = ctx.IsEtch ? "#148" : GetLinearFeedVariable(linear.Layer);
@@ -138,7 +163,9 @@ public sealed class CincinnatiFeatureWriter
 
                 // G2 = CW, G3 = CCW
                 var gCode = arc.Rotation == RotationType.CW ? "G2" : "G3";
-                sb.Append($"{gCode} X{_fmt.FormatCoord(arc.EndPoint.X + offset.X)} Y{_fmt.FormatCoord(arc.EndPoint.Y + offset.Y)}");
+                var xCoord = FormatCoordWithVars(arc.EndPoint.X + offset.X, "X", arc.VariableRefs, ctx);
+                var yCoord = FormatCoordWithVars(arc.EndPoint.Y + offset.Y, "Y", arc.VariableRefs, ctx);
+                sb.Append($"{gCode} X{xCoord} Y{yCoord}");
 
                 // Convert absolute center to incremental I/J
                 var i = arc.CenterPoint.X - currentPos.X;
@@ -177,6 +204,52 @@ public sealed class CincinnatiFeatureWriter
             WriteM47(writer, ctx);
     }
 
+    /// <summary>
+    /// Formats a coordinate value, using a #number variable reference if the motion
+    /// has a VariableRef for this axis and the variable is mapped (non-inline).
+    /// For cut-off features, plate-edge coordinates are substituted with
+    /// the sheet width/length variables.
+    /// Inline variables fall through to literal formatting.
+    /// </summary>
+    private string FormatCoordWithVars(double value, string axis,
+        Dictionary<string, string> variableRefs, FeatureContext ctx)
+    {
+        // User-defined variable references take priority
+        if (variableRefs != null
+            && variableRefs.TryGetValue(axis, out var varName)
+            && ctx.UserVariableMapping != null
+            && ctx.UserVariableMapping.TryGetValue((ctx.DrawingId, varName), out var varNum))
+        {
+            return $"#{varNum}";
+        }
+
+        // Cut-off plate-edge substitution
+        if (ctx.IsCutOff)
+        {
+            var sheetVar = MatchCutOffSheetVariable(value, axis, ctx);
+            if (sheetVar != null)
+                return sheetVar;
+        }
+
+        return _fmt.FormatCoord(value);
+    }
+
+    /// <summary>
+    /// For cut-off coordinates, checks if the value matches a plate edge dimension
+    /// and returns the sheet variable reference (e.g., "#110") if so.
+    /// </summary>
+    private string MatchCutOffSheetVariable(double value, string axis, FeatureContext ctx)
+    {
+        // Vertical cutoffs travel along Y — the Y endpoint at the plate edge = sheet width
+        // Horizontal cutoffs travel along X — the X endpoint at the plate edge = sheet length
+        if (axis == "Y" && Tolerance.IsEqualTo(value, ctx.PlateWidth))
+            return $"#{_config.SheetWidthVariable}";
+        if (axis == "X" && Tolerance.IsEqualTo(value, ctx.PlateLength))
+            return $"#{_config.SheetLengthVariable}";
+
+        return null;
+    }
+
     private Vector FindPiercePoint(List<ICode> codes)
     {
         foreach (var code in codes)
@@ -195,14 +268,16 @@ public sealed class CincinnatiFeatureWriter
         return Vector.Zero;
     }
 
-    private void WriteRapidToPierce(TextWriter writer, int featureNumber, Vector piercePoint, Vector offset)
+    private void WriteRapidToPierce(TextWriter writer, FeatureContext ctx, Vector piercePoint, Vector offset)
     {
         var sb = new StringBuilder();
 
         if (_config.UseLineNumbers)
-            sb.Append($"N{featureNumber} ");
+            sb.Append($"N{ctx.FeatureNumber} ");
 
-        sb.Append($"G0 X{_fmt.FormatCoord(piercePoint.X + offset.X)} Y{_fmt.FormatCoord(piercePoint.Y + offset.Y)}");
+        var xCoord = FormatCoordWithVars(piercePoint.X + offset.X, "X", null, ctx);
+        var yCoord = FormatCoordWithVars(piercePoint.Y + offset.Y, "Y", null, ctx);
+        sb.Append($"G0 X{xCoord} Y{yCoord}");
 
         writer.WriteLine(sb.ToString());
     }

OpenNest.Posts.Cincinnati/CincinnatiPartSubprogramWriter.cs

@@ -66,7 +66,6 @@ public sealed class CincinnatiPartSubprogramWriter
             _featureWriter.Write(w, ctx);
         }
 
-        w.WriteLine("G0 X0 Y0");
         w.WriteLine($"M99 (END OF {drawingName})");
     }
 

OpenNest.Posts.Cincinnati/CincinnatiPostConfig.cs

@@ -253,6 +253,11 @@ namespace OpenNest.Posts.Cincinnati
             new() { MaxRadius = 4.500, FeedratePercent = 0.80, VariableNumber = 125 }
         };
 
+        [Category("A. Variables")]
+        [DisplayName("User Variable Start")]
+        [Description("Starting variable number for user-defined variables (#200, #201, etc.).")]
+        public int UserVariableStart { get; set; } = 200;
+
         [Category("A. Variables")]
         [DisplayName("Sheet Width Variable")]
         [Description("Variable number for sheet width.")]

OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -70,7 +70,10 @@ namespace OpenNest.Posts.Cincinnati
                 .Where(p => p.Parts.Count > 0)
                 .ToList();
 
-            // 3. Resolve gas and library files
+            // 3. Register user variables from drawing programs
+            var userVarMapping = RegisterUserVariables(vars, plates);
+
+            // 4. Resolve gas and library files
             var resolver = new MaterialLibraryResolver(Config);
             var gas = MaterialLibraryResolver.ResolveGas(nest, Config);
             var etchLibrary = resolver.ResolveEtchLibrary(Config.DefaultEtchGas);
@@ -79,42 +82,41 @@ namespace OpenNest.Posts.Cincinnati
             var firstPlate = plates.FirstOrDefault();
             var initialCutLibrary = resolver.ResolveCutLibrary(nest.Material?.Name ?? "", nest.Thickness, gas);
 
-            // 4. Build part sub-program registry (if enabled)
+            // 5. Build part sub-program registry (if enabled)
             Dictionary<(int, long), int> partSubprograms = null;
             List<(int subNum, string name, Program program)> subprogramEntries = null;
 
             if (Config.UsePartSubprograms)
                 (partSubprograms, subprogramEntries) = CincinnatiPartSubprogramWriter.BuildRegistry(plates, Config.PartSubprogramStart);
 
-            // 5. Create writers
+            // 6. Create writers
             var preamble = new CincinnatiPreambleWriter(Config);
             var sheetWriter = new CincinnatiSheetWriter(Config, vars);
 
-            // 6. Build material description from nest
+            // 7. Build material description from nest
             var material = nest.Material;
             var materialDesc = material != null
                 ? $"{material.Name}{(string.IsNullOrEmpty(material.Grade) ? "" : $", {material.Grade}")}"
                 : "";
 
-            // 7. Write to stream
+            // 8. Write to stream
             using var writer = new StreamWriter(outputStream, Encoding.UTF8, 1024, leaveOpen: true);
 
             // Main program
-            preamble.WriteMainProgram(writer, nest.Name ?? "NEST", materialDesc, plates.Count, initialCutLibrary);
+            preamble.WriteMainProgram(writer, nest.Name ?? "NEST", materialDesc, plates, initialCutLibrary);
 
             // Variable declaration subprogram
             preamble.WriteVariableDeclaration(writer, vars);
 
-            // Sheet subprograms
+            // Sheet subprograms (one per unique layout, quantity handled via L count in main)
             for (var i = 0; i < plates.Count; i++)
             {
                 var plate = plates[i];
-                var sheetIndex = i + 1;
+                var layoutIndex = i + 1;
                 var subNumber = Config.SheetSubprogramStart + i;
                 var cutLibrary = resolver.ResolveCutLibrary(nest.Material?.Name ?? "", nest.Thickness, gas);
-                var isLastSheet = i == plates.Count - 1;
-                sheetWriter.Write(writer, plate, nest.Name ?? "NEST", sheetIndex, subNumber,
-                    cutLibrary, etchLibrary, partSubprograms, isLastSheet);
+                sheetWriter.Write(writer, plate, nest.Name ?? "NEST", layoutIndex, subNumber,
+                    cutLibrary, etchLibrary, partSubprograms, userVarMapping);
             }
 
             // Part sub-programs (if enabled)
@@ -142,6 +144,103 @@ namespace OpenNest.Posts.Cincinnati
             Post(nest, fs);
         }
 
+        private Dictionary<(int drawingId, string varName), int> RegisterUserVariables(
+            ProgramVariableManager vars, List<Plate> plates)
+        {
+            var mapping = new Dictionary<(int drawingId, string varName), int>();
+            var nextNumber = Config.UserVariableStart;
+
+            // Track global variables by name so they share a single number
+            var globalNumbers = new Dictionary<string, int>(System.StringComparer.OrdinalIgnoreCase);
+
+            // Collect unique drawings from all plates
+            var seenDrawings = new HashSet<int>();
+            foreach (var plate in plates)
+            {
+                foreach (var part in plate.Parts)
+                {
+                    var drawing = part.BaseDrawing;
+                    if (drawing.IsCutOff || !seenDrawings.Add(drawing.Id))
+                        continue;
+
+                    foreach (var kvp in drawing.Program.Variables)
+                    {
+                        var varDef = kvp.Value;
+
+                        // Skip inline variables — they emit literal values
+                        if (varDef.Inline)
+                            continue;
+
+                        if (varDef.Global)
+                        {
+                            if (!globalNumbers.TryGetValue(varDef.Name, out var globalNum))
+                            {
+                                globalNum = nextNumber++;
+                                globalNumbers[varDef.Name] = globalNum;
+
+                                // Register once in the variable manager
+                                var commentName = ToPascalCase(varDef.Name);
+                                var expression = FormatVariableValue(varDef.Value);
+                                vars.GetOrCreate(commentName, globalNum, expression);
+                            }
+
+                            mapping[(drawing.Id, varDef.Name)] = globalNum;
+                        }
+                        else
+                        {
+                            var num = nextNumber++;
+                            mapping[(drawing.Id, varDef.Name)] = num;
+
+                            // Register with drawing name prefix in the comment
+                            var drawingLabel = ToPascalCase(drawing.Name);
+                            var varLabel = ToPascalCase(varDef.Name);
+                            var commentName = $"{drawingLabel}{varLabel}";
+                            var expression = FormatVariableValue(varDef.Value);
+                            vars.GetOrCreate(commentName, num, expression);
+                        }
+                    }
+                }
+            }
+
+            return mapping;
+        }
+
+        /// <summary>
+        /// Converts a variable name from snake_case or camelCase to PascalCase.
+        /// Examples: "sheet_width" → "SheetWidth", "holeSpacing" → "HoleSpacing"
+        /// </summary>
+        private static string ToPascalCase(string name)
+        {
+            var sb = new StringBuilder(name.Length);
+            var capitalizeNext = true;
+
+            foreach (var c in name)
+            {
+                if (c == '_')
+                {
+                    capitalizeNext = true;
+                    continue;
+                }
+
+                if (capitalizeNext)
+                {
+                    sb.Append(char.ToUpper(c));
+                    capitalizeNext = false;
+                }
+                else
+                {
+                    sb.Append(c);
+                }
+            }
+
+            return sb.ToString();
+        }
+
+        private static string FormatVariableValue(double value)
+        {
+            return value.ToString("0.####", System.Globalization.CultureInfo.InvariantCulture);
+        }
+
         private ProgramVariableManager CreateVariableManager()
         {
             var vars = new ProgramVariableManager();

OpenNest.Posts.Cincinnati/CincinnatiPreambleWriter.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using OpenNest;
 using OpenNest.CNC;
@@ -23,7 +24,7 @@ public sealed class CincinnatiPreambleWriter
     /// </summary>
     /// <param name="initialLibrary">Resolved G89 library file for the initial process setup.</param>
     public void WriteMainProgram(TextWriter w, string nestName, string materialDescription,
-        int sheetCount, string initialLibrary)
+        List<Plate> plates, string initialLibrary)
     {
         w.WriteLine(CoordinateFormatter.Comment($"NEST {nestName}"));
         w.WriteLine(CoordinateFormatter.Comment($"CONFIGURATION - {_config.ConfigurationName}"));
@@ -54,10 +55,16 @@ public sealed class CincinnatiPreambleWriter
 
         w.WriteLine("GOTO1 (GOTO SHEET NUMBER)");
 
-        for (var i = 1; i <= sheetCount; i++)
+        for (var i = 0; i < plates.Count; i++)
         {
-            var subNum = _config.SheetSubprogramStart + (i - 1);
-            w.WriteLine($"N{i} M98 P{subNum} (SHEET {i})");
+            var layoutNumber = i + 1;
+            var subNum = _config.SheetSubprogramStart + i;
+            var qty = System.Math.Max(plates[i].Quantity, 1);
+            var lParam = qty > 1 ? $" L{qty}" : "";
+            var sheetLabel = qty > 1
+                ? $"LAYOUT {layoutNumber} - {qty} SHEETS"
+                : $"LAYOUT {layoutNumber}";
+            w.WriteLine($"N{layoutNumber} M98 P{subNum}{lParam} ({sheetLabel})");
         }
 
         w.WriteLine("M42");

OpenNest.Posts.Cincinnati/CincinnatiSheetWriter.cs

@@ -35,10 +35,10 @@ public sealed class CincinnatiSheetWriter
     /// Optional mapping of (drawingId, rotationKey) to sub-program number.
     /// When provided, non-cutoff parts are emitted as M98 calls instead of inline features.
     /// </param>
-    public void Write(TextWriter w, Plate plate, string nestName, int sheetIndex, int subNumber,
+    public void Write(TextWriter w, Plate plate, string nestName, int layoutIndex, int subNumber,
         string cutLibrary, string etchLibrary,
         Dictionary<(int, long), int> partSubprograms = null,
-        bool isLastSheet = false)
+        Dictionary<(int drawingId, string varName), int> userVarMapping = null)
     {
         if (plate.Parts.Count == 0)
             return;
@@ -51,11 +51,10 @@ public sealed class CincinnatiSheetWriter
 
         // 1. Sheet header
         w.WriteLine("(*****************************************************)");
-        w.WriteLine($"( START OF {nestName}.{sheetIndex:D3} )");
+        w.WriteLine($"( START OF {nestName}.{layoutIndex:D3} )");
         w.WriteLine($":{subNumber}");
-        w.WriteLine($"( Sheet {sheetIndex} )");
-        w.WriteLine($"( Layout {sheetIndex} )");
-        w.WriteLine($"( SHEET NAME = {_fmt.FormatCoord(length)} X {_fmt.FormatCoord(width)} )");
+        w.WriteLine($"( Layout {layoutIndex} )");
+        w.WriteLine($"( SHEET NAME = {_fmt.FormatCoord(width)} X {_fmt.FormatCoord(length)} )");
         w.WriteLine($"( Total parts on sheet = {partCount} )");
         w.WriteLine($"#{_config.SheetWidthVariable}={_fmt.FormatCoord(width)} (SHEET WIDTH FOR CUTOFFS)");
         w.WriteLine($"#{_config.SheetLengthVariable}={_fmt.FormatCoord(length)} (SHEET LENGTH FOR CUTOFFS)");
@@ -88,23 +87,22 @@ public sealed class CincinnatiSheetWriter
 
         // 4. Emit parts
         if (partSubprograms != null)
-            WritePartsWithSubprograms(w, allParts, cutLibrary, etchLibrary, sheetDiagonal, partSubprograms);
+            WritePartsWithSubprograms(w, allParts, cutLibrary, etchLibrary, sheetDiagonal, width, length, partSubprograms, userVarMapping);
         else
-            WritePartsInline(w, allParts, cutLibrary, etchLibrary, sheetDiagonal);
+            WritePartsInline(w, allParts, cutLibrary, etchLibrary, sheetDiagonal, width, length, userVarMapping);
 
         // 5. Footer
         w.WriteLine("M42");
-        w.WriteLine("G0 X0 Y0");
-        var emitM50 = _config.PalletExchange == PalletMode.EndOfSheet
-            || (_config.PalletExchange == PalletMode.StartAndEnd && isLastSheet);
-        if (emitM50)
-            w.WriteLine($"N{sheetIndex + 1} M50");
-        w.WriteLine($"M99 (END OF {nestName}.{sheetIndex:D3})");
+        if (_config.PalletExchange != PalletMode.None)
+            w.WriteLine("M50");
+        w.WriteLine($"M99 (END OF {nestName}.{layoutIndex:D3})");
     }
 
     private void WritePartsWithSubprograms(TextWriter w, List<Part> allParts,
         string cutLibrary, string etchLibrary, double sheetDiagonal,
-        Dictionary<(int, long), int> partSubprograms)
+        double plateWidth, double plateLength,
+        Dictionary<(int, long), int> partSubprograms,
+        Dictionary<(int drawingId, string varName), int> userVarMapping)
     {
         var lastPartName = "";
         var featureIndex = 0;
@@ -154,7 +152,12 @@ public sealed class CincinnatiSheetWriter
                         LibraryFile = isEtch ? etchLibrary : cutLibrary,
                         CutDistance = cutDistance,
                         SheetDiagonal = sheetDiagonal,
-                        PartLocation = part.Location
+                        PartLocation = part.Location,
+                        UserVariableMapping = userVarMapping,
+                        DrawingId = part.BaseDrawing.Id,
+                        IsCutOff = part.BaseDrawing.IsCutOff,
+                        PlateWidth = plateWidth,
+                        PlateLength = plateLength
                     };
 
                     _featureWriter.Write(w, ctx);
@@ -202,7 +205,9 @@ public sealed class CincinnatiSheetWriter
     }
 
     private void WritePartsInline(TextWriter w, List<Part> allParts,
-        string cutLibrary, string etchLibrary, double sheetDiagonal)
+        string cutLibrary, string etchLibrary, double sheetDiagonal,
+        double plateWidth, double plateLength,
+        Dictionary<(int drawingId, string varName), int> userVarMapping)
     {
         // Split and classify features, ordering etch before cut per part
         var features = new List<(Part part, List<ICode> codes, bool isEtch)>();
@@ -242,7 +247,12 @@ public sealed class CincinnatiSheetWriter
                 LibraryFile = isEtch ? etchLibrary : cutLibrary,
                 CutDistance = cutDistance,
                 SheetDiagonal = sheetDiagonal,
-                PartLocation = part.Location
+                PartLocation = part.Location,
+                UserVariableMapping = userVarMapping,
+                DrawingId = part.BaseDrawing.Id,
+                IsCutOff = part.BaseDrawing.IsCutOff,
+                PlateWidth = plateWidth,
+                PlateLength = plateLength
             };
 
             _featureWriter.Write(w, ctx);

OpenNest.Tests/CNC/ProgramVariableTests.cs

@@ -101,4 +101,35 @@ public class ProgramVariableTests
         move.Offset(5.0, 0);
         Assert.Null(move.VariableRefs);
     }
+
+    [Fact]
+    public void Program_Variables_EmptyByDefault()
+    {
+        var pgm = new Program();
+        Assert.Empty(pgm.Variables);
+    }
+
+    [Fact]
+    public void Program_Variables_CaseInsensitive()
+    {
+        var pgm = new Program();
+        pgm.Variables["Diameter"] = new VariableDefinition("Diameter", "0.3", 0.3);
+        Assert.True(pgm.Variables.ContainsKey("diameter"));
+    }
+
+    [Fact]
+    public void Program_Clone_DeepCopiesVariables()
+    {
+        var pgm = new Program();
+        pgm.Variables["diameter"] = new VariableDefinition("diameter", "0.3", 0.3);
+        pgm.Codes.Add(new LinearMove(1.0, 0));
+
+        var clone = (Program)pgm.Clone();
+
+        Assert.Single(clone.Variables);
+        Assert.Equal(0.3, clone.Variables["diameter"].Value);
+        // Verify it's a separate dictionary
+        clone.Variables.Remove("diameter");
+        Assert.Single(pgm.Variables);
+    }
 }

OpenNest.Tests/Cincinnati/CincinnatiPostProcessorTests.cs

@@ -38,7 +38,7 @@ public class CincinnatiPostProcessorTests
 
         // Sheet subprogram
         Assert.Contains(":101", output);
-        Assert.Contains("( Sheet 1 )", output);
+        Assert.Contains("( Layout 1 )", output);
         Assert.Contains("G84", output);
         Assert.Contains("M99", output);
     }
@@ -150,8 +150,8 @@ public class CincinnatiPostProcessorTests
         var output = Encoding.UTF8.GetString(ms.ToArray());
 
         // Should only have one sheet subprogram call in main
-        Assert.Contains("N1 M98 P101 (SHEET 1)", output);
-        Assert.DoesNotContain("SHEET 2", output);
+        Assert.Contains("N1 M98 P101 (LAYOUT 1)", output);
+        Assert.DoesNotContain("LAYOUT 2", output);
     }
 
     [Fact]
@@ -258,8 +258,7 @@ public class CincinnatiPostProcessorTests
         Assert.Contains(":200", output);
         Assert.Contains("G84", output);
 
-        // Sub-program ends with G0 X0 Y0 and M99
-        Assert.Contains("G0 X0 Y0", output);
+        // Sub-program ends with M99
         Assert.Contains("M99 (END OF Square)", output);
 
         // G92 restore after M98 call

OpenNest.Tests/Cincinnati/CincinnatiPreambleWriterTests.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.IO;
 using System.Text;
 using OpenNest.CNC;
@@ -19,7 +20,8 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "TestNest", "Mild Steel, 10GA", 2, "MS135N2PANEL.lib");
+        var plates = new List<Plate> { new(48, 96), new(48, 96) };
+        writer.WriteMainProgram(sw, "TestNest", "Mild Steel, 10GA", plates, "MS135N2PANEL.lib");
 
         var output = sb.ToString();
         Assert.Contains("( NEST TestNest )", output);
@@ -29,8 +31,8 @@ public class CincinnatiPreambleWriterTests
         Assert.Contains("G89 PMS135N2PANEL.lib", output);
         Assert.Contains("M98 P100 (Variable Declaration)", output);
         Assert.Contains("GOTO1 (GOTO SHEET NUMBER)", output);
-        Assert.Contains("N1 M98 P101 (SHEET 1)", output);
-        Assert.Contains("N2 M98 P102 (SHEET 2)", output);
+        Assert.Contains("N1 M98 P101 (LAYOUT 1)", output);
+        Assert.Contains("N2 M98 P102 (LAYOUT 2)", output);
         Assert.Contains("M30 (END OF MAIN)", output);
     }
 
@@ -42,7 +44,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.Contains("G21 G90", sb.ToString());
     }
@@ -55,7 +57,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.Contains("G20 G90", sb.ToString());
     }
@@ -68,7 +70,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.Contains("G121 (SMART RAPIDS)", sb.ToString());
     }
@@ -81,7 +83,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.DoesNotContain("G121", sb.ToString());
     }
@@ -94,7 +96,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.Contains("M50", sb.ToString());
     }
@@ -107,7 +109,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.DoesNotContain("M50", sb.ToString());
     }
@@ -120,7 +122,7 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.Contains("G61", sb.ToString());
     }
@@ -133,11 +135,33 @@ public class CincinnatiPreambleWriterTests
         using var sw = new StringWriter(sb);
         var writer = new CincinnatiPreambleWriter(config);
 
-        writer.WriteMainProgram(sw, "Test", "", 1, "");
+        writer.WriteMainProgram(sw, "Test", "", new List<Plate> { new(48, 96) }, "");
 
         Assert.DoesNotContain("G61", sb.ToString());
     }
 
+    [Fact]
+    public void WriteMainProgram_EmitsLCount_WhenQuantityGreaterThanOne()
+    {
+        var config = new CincinnatiPostConfig { PostedUnits = Units.Inches };
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var writer = new CincinnatiPreambleWriter(config);
+
+        var plates = new List<Plate>
+        {
+            new(48, 96) { Quantity = 5 },
+            new(72, 48) { Quantity = 2 },
+            new(36, 48) { Quantity = 1 }
+        };
+        writer.WriteMainProgram(sw, "Test", "", plates, "");
+
+        var output = sb.ToString();
+        Assert.Contains("N1 M98 P101 L5 (LAYOUT 1 - 5 SHEETS)", output);
+        Assert.Contains("N2 M98 P102 L2 (LAYOUT 2 - 2 SHEETS)", output);
+        Assert.Contains("N3 M98 P103 (LAYOUT 3)", output);
+    }
+
     [Fact]
     public void WriteVariableDeclaration_EmitsSubprogram()
     {

OpenNest.Tests/Cincinnati/CincinnatiSheetWriterTests.cs

@@ -28,7 +28,7 @@ public class CincinnatiSheetWriterTests
 
         var output = sb.ToString();
         Assert.Contains(":101", output);
-        Assert.Contains("( Sheet 1 )", output);
+        Assert.Contains("( Layout 1 )", output);
         Assert.Contains("#110=", output);
         Assert.Contains("#111=", output);
         Assert.Contains("G92 X#5021 Y#5022", output);
@@ -55,7 +55,6 @@ public class CincinnatiSheetWriterTests
 
         var output = sb.ToString();
         Assert.Contains("M42", output);
-        Assert.Contains("G0 X0 Y0", output);
         Assert.Contains("M50", output);
     }
 
@@ -143,7 +142,7 @@ public class CincinnatiSheetWriterTests
     }
 
     [Fact]
-    public void WriteSheet_StartAndEnd_NoM50OnNonLastSheet()
+    public void WriteSheet_StartAndEnd_EmitsM50()
     {
         var config = new CincinnatiPostConfig
         {
@@ -157,33 +156,33 @@ public class CincinnatiSheetWriterTests
         using var sw = new StringWriter(sb);
         var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
 
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "", isLastSheet: false);
-
-        var output = sb.ToString();
-        Assert.DoesNotContain("M50", output);
-    }
-
-    [Fact]
-    public void WriteSheet_StartAndEnd_M50OnLastSheet()
-    {
-        var config = new CincinnatiPostConfig
-        {
-            PalletExchange = PalletMode.StartAndEnd,
-            PostedAccuracy = 4
-        };
-        var plate = new Plate(48.0, 96.0);
-        plate.Parts.Add(new Part(new Drawing("TestPart", CreateSimpleProgram())));
-
-        var sb = new StringBuilder();
-        using var sw = new StringWriter(sb);
-        var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
-
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "", isLastSheet: true);
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "");
 
         var output = sb.ToString();
         Assert.Contains("M50", output);
     }
 
+    [Fact]
+    public void WriteSheet_NoPalletExchange_OmitsM50()
+    {
+        var config = new CincinnatiPostConfig
+        {
+            PalletExchange = PalletMode.None,
+            PostedAccuracy = 4
+        };
+        var plate = new Plate(48.0, 96.0);
+        plate.Parts.Add(new Part(new Drawing("TestPart", CreateSimpleProgram())));
+
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
+
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "");
+
+        var output = sb.ToString();
+        Assert.DoesNotContain("M50", output);
+    }
+
     [Fact]
     public void WriteSheet_EndOfSheet_AlwaysEmitsM50()
     {
@@ -199,7 +198,7 @@ public class CincinnatiSheetWriterTests
         using var sw = new StringWriter(sb);
         var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
 
-        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "", isLastSheet: false);
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "");
 
         var output = sb.ToString();
         Assert.Contains("M50", output);

OpenNest.Tests/Cincinnati/UserVariablePostTests.cs

@@ -0,0 +1,207 @@
+using System.IO;
+using System.Linq;
+using System.Text;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.IO;
+using OpenNest.Posts.Cincinnati;
+
+namespace OpenNest.Tests.Cincinnati;
+
+public class UserVariablePostTests
+{
+    [Fact]
+    public void UserVariables_EmittedInDeclarationSubprogram()
+    {
+        var output = PostNestWithVariables("width = 48.0\nG90\nG01X$widthY0");
+
+        Assert.Contains("#200=48", output);
+        Assert.Contains("WIDTH", output.ToUpper());
+    }
+
+    [Fact]
+    public void UserVariables_InlineVariable_NotEmittedAsNumbered()
+    {
+        var output = PostNestWithVariables("kerf = 0.06 inline\nG90\nG01X1Y0");
+
+        Assert.DoesNotContain("#200", output);
+    }
+
+    [Fact]
+    public void UserVariables_CoordinateUsesNumberedVariable()
+    {
+        var output = PostNestWithVariables("width = 48.0\nG90\nG01X$widthY0");
+
+        Assert.Contains("X#200", output);
+    }
+
+    [Fact]
+    public void UserVariables_InlineVariable_CoordinateUsesLiteral()
+    {
+        var output = PostNestWithVariables("kerf = 0.06 inline\nG90\nG01X$kerfY0");
+
+        Assert.Contains("X0.06", output);
+        // G1 coordinate lines should not use X#nnn variable references for inline vars
+        var g1Lines = output.Split('\n').Where(l => l.TrimStart().StartsWith("G1 ")).ToList();
+        Assert.All(g1Lines, line => Assert.DoesNotContain("X#", line));
+    }
+
+    [Fact]
+    public void UserVariables_GlobalVariables_SharedAcrossDrawings()
+    {
+        var pgm1 = ParseProgram("sheet_width = 48.0 global\nG90\nG01X$sheet_widthY0");
+        var pgm2 = ParseProgram("sheet_width = 48.0 global\nG90\nG01X$sheet_widthY0");
+
+        var drawing1 = new Drawing("Part1", pgm1);
+        var drawing2 = new Drawing("Part2", pgm2);
+        var nest = new Nest { Name = "Test" };
+        nest.Drawings.Add(drawing1);
+        nest.Drawings.Add(drawing2);
+        var plate = new Plate(new Size(100, 100));
+        plate.Parts.Add(new Part(drawing1, new Vector(0, 0)));
+        plate.Parts.Add(new Part(drawing2, new Vector(50, 0)));
+        nest.Plates.Add(plate);
+
+        var config = new CincinnatiPostConfig { UserVariableStart = 200 };
+        var post = new CincinnatiPostProcessor(config);
+        var output = PostToString(post, nest);
+
+        // Both should use the same #200 — only one declaration
+        var declarationCount = output.Split('\n')
+            .Count(l => l.Contains("#200=") && l.ToUpper().Contains("SHEET WIDTH"));
+        Assert.Equal(1, declarationCount);
+    }
+
+    [Fact]
+    public void UserVariables_LocalVariables_GetSeparateNumbers()
+    {
+        var pgm1 = ParseProgram("diameter = 0.3\nG90\nG01X$diameterY0");
+        var pgm2 = ParseProgram("diameter = 0.5\nG90\nG01X$diameterY0");
+
+        var drawing1 = new Drawing("TubeA", pgm1);
+        var drawing2 = new Drawing("TubeB", pgm2);
+        var nest = new Nest { Name = "Test" };
+        nest.Drawings.Add(drawing1);
+        nest.Drawings.Add(drawing2);
+        var plate = new Plate(new Size(100, 100));
+        plate.Parts.Add(new Part(drawing1, new Vector(0, 0)));
+        plate.Parts.Add(new Part(drawing2, new Vector(50, 0)));
+        nest.Plates.Add(plate);
+
+        var config = new CincinnatiPostConfig { UserVariableStart = 200 };
+        var post = new CincinnatiPostProcessor(config);
+        var output = PostToString(post, nest);
+
+        // Two separate declarations with different numbers
+        Assert.Contains("#200=0.3", output);
+        Assert.Contains("#201=0.5", output);
+        Assert.Contains("TUBE A", output.ToUpper());
+        Assert.Contains("TUBE B", output.ToUpper());
+    }
+
+    [Fact]
+    public void UserVariables_StartNumberConfigurable()
+    {
+        var config = new CincinnatiPostConfig { UserVariableStart = 300 };
+        var output = PostNestWithVariables("width = 48.0\nG90\nG01X$widthY0", config);
+
+        Assert.Contains("#300=48", output);
+    }
+
+    [Fact]
+    public void CutOff_VerticalCut_UsesSheetWidthVariable()
+    {
+        // Create a plate with a vertical cutoff
+        var config = new CincinnatiPostConfig { SheetWidthVariable = 110, SheetLengthVariable = 111 };
+        var nest = new Nest { Name = "Test" };
+        var plate = new Plate(new Size(48, 96));
+
+        // Add a simple part so the plate isn't empty
+        var partPgm = new Program();
+        partPgm.Codes.Add(new RapidMove(0, 0));
+        partPgm.Codes.Add(new LinearMove(10, 0));
+        partPgm.Codes.Add(new LinearMove(10, 10));
+        partPgm.Codes.Add(new LinearMove(0, 10));
+        partPgm.Codes.Add(new LinearMove(0, 0));
+        var drawing = new Drawing("Part1", partPgm);
+        nest.Drawings.Add(drawing);
+        plate.Parts.Add(new Part(drawing, new Vector(0, 0)));
+
+        // Add a vertical cutoff that goes full width (Y=0 to Y=48)
+        var cutoff = new CutOff(new Vector(20, 0), CutOffAxis.Vertical);
+        plate.CutOffs.Add(cutoff);
+        plate.RegenerateCutOffs(new CutOffSettings());
+
+        nest.Plates.Add(plate);
+
+        var post = new CincinnatiPostProcessor(config);
+        var output = PostToString(post, nest);
+
+        // The cutoff line end at Y=48 (sheet width) should use #110
+        Assert.Contains("Y#110", output);
+    }
+
+    [Fact]
+    public void CutOff_SegmentedCut_OnlyEdgeUsesVariable()
+    {
+        // Create a plate with a part in the middle and a vertical cutoff
+        var config = new CincinnatiPostConfig { SheetWidthVariable = 110 };
+        var nest = new Nest { Name = "Test" };
+        var plate = new Plate(new Size(48, 96));
+
+        // Part in the middle — cutoff will be segmented around it
+        var partPgm = new Program();
+        partPgm.Codes.Add(new RapidMove(0, 0));
+        partPgm.Codes.Add(new LinearMove(10, 0));
+        partPgm.Codes.Add(new LinearMove(10, 10));
+        partPgm.Codes.Add(new LinearMove(0, 10));
+        partPgm.Codes.Add(new LinearMove(0, 0));
+        var drawing = new Drawing("Part1", partPgm);
+        nest.Drawings.Add(drawing);
+        plate.Parts.Add(new Part(drawing, new Vector(15, 20)));  // Part at Y=20-30, should create gap
+
+        var cutoff = new CutOff(new Vector(20, 0), CutOffAxis.Vertical);
+        plate.CutOffs.Add(cutoff);
+        plate.RegenerateCutOffs(new CutOffSettings());
+
+        nest.Plates.Add(plate);
+
+        var post = new CincinnatiPostProcessor(config);
+        var output = PostToString(post, nest);
+
+        // The last segment endpoint at Y=48 should use #110
+        Assert.Contains("Y#110", output);
+    }
+
+    private static string PostNestWithVariables(string gcode, CincinnatiPostConfig config = null)
+    {
+        var program = ParseProgram(gcode);
+        var drawing = new Drawing("TestPart", program);
+        var nest = new Nest { Name = "Test" };
+        nest.Drawings.Add(drawing);
+        var plate = new Plate(new Size(100, 100));
+        plate.Parts.Add(new Part(drawing, new Vector(0, 0)));
+        nest.Plates.Add(plate);
+
+        config ??= new CincinnatiPostConfig { UserVariableStart = 200 };
+        var post = new CincinnatiPostProcessor(config);
+        return PostToString(post, nest);
+    }
+
+    private static string PostToString(CincinnatiPostProcessor post, Nest nest)
+    {
+        var ms = new MemoryStream();
+        post.Post(nest, ms);
+        ms.Position = 0;
+        return new StreamReader(ms).ReadToEnd();
+    }
+
+    private static Program ParseProgram(string gcode)
+    {
+        var stream = new MemoryStream(Encoding.UTF8.GetBytes(gcode));
+        var reader = new ProgramReader(stream);
+        var program = reader.Read();
+        reader.Close();
+        return program;
+    }
+}

OpenNest.Tests/IO/NestWriterVariableTests.cs

@@ -0,0 +1,91 @@
+using System.IO;
+using System.Linq;
+using System.Text;
+using OpenNest.CNC;
+using OpenNest.Geometry;
+using OpenNest.IO;
+
+namespace OpenNest.Tests.IO;
+
+public class NestWriterVariableTests
+{
+    [Fact]
+    public void RoundTrip_VariableDefinitions_Preserved()
+    {
+        var nest = CreateNestWithVariableProgram(
+            "width = 48.0 global\ndiameter = 0.3\nG90\nG01X$widthY$diameter");
+
+        var loaded = RoundTrip(nest);
+        var pgm = loaded.Drawings.First().Program;
+
+        Assert.Equal(2, pgm.Variables.Count);
+        Assert.Equal(48.0, pgm.Variables["width"].Value);
+        Assert.True(pgm.Variables["width"].Global);
+        Assert.Equal(0.3, pgm.Variables["diameter"].Value);
+        Assert.False(pgm.Variables["diameter"].Global);
+    }
+
+    [Fact]
+    public void RoundTrip_VariableRefs_Preserved()
+    {
+        var nest = CreateNestWithVariableProgram(
+            "width = 48.0\nG90\nG01X$widthY0");
+
+        var loaded = RoundTrip(nest);
+        var pgm = loaded.Drawings.First().Program;
+
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.Equal(48.0, linear.EndPoint.X);
+        Assert.NotNull(linear.VariableRefs);
+        Assert.Equal("width", linear.VariableRefs["X"]);
+    }
+
+    [Fact]
+    public void RoundTrip_InlineFlag_Preserved()
+    {
+        var nest = CreateNestWithVariableProgram(
+            "kerf = 0.06 inline\nG90\nG01X1Y0");
+
+        var loaded = RoundTrip(nest);
+        var pgm = loaded.Drawings.First().Program;
+
+        Assert.True(pgm.Variables["kerf"].Inline);
+    }
+
+    [Fact]
+    public void RoundTrip_NoVariables_WorksAsNormal()
+    {
+        var nest = CreateNestWithVariableProgram("G90\nG01X1Y2");
+
+        var loaded = RoundTrip(nest);
+        var pgm = loaded.Drawings.First().Program;
+
+        Assert.Empty(pgm.Variables);
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.Equal(1.0, linear.EndPoint.X);
+    }
+
+    private static Nest CreateNestWithVariableProgram(string gcode)
+    {
+        var stream = new MemoryStream(Encoding.UTF8.GetBytes(gcode));
+        var reader = new ProgramReader(stream);
+        var program = reader.Read();
+        reader.Close();
+
+        var drawing = new Drawing("TestPart", program);
+        var nest = new Nest { Name = "Test" };
+        nest.Drawings.Add(drawing);
+        var plate = new Plate(new Size(100, 100));
+        plate.Parts.Add(new Part(drawing, new Vector(0, 0)));
+        nest.Plates.Add(plate);
+        return nest;
+    }
+
+    private static Nest RoundTrip(Nest nest)
+    {
+        var ms = new MemoryStream();
+        new NestWriter(nest).Write(ms);
+        ms.Position = 0;
+        return new NestReader(ms).Read();
+    }
+}

OpenNest.Tests/IO/ProgramReaderVariableTests.cs

@@ -0,0 +1,136 @@
+using System.IO;
+using System.Text;
+using OpenNest.CNC;
+using OpenNest.IO;
+
+namespace OpenNest.Tests.IO;
+
+public class ProgramReaderVariableTests
+{
+    private Program Parse(string gcode)
+    {
+        var stream = new MemoryStream(Encoding.UTF8.GetBytes(gcode));
+        var reader = new ProgramReader(stream);
+        var program = reader.Read();
+        reader.Close();
+        return program;
+    }
+
+    [Fact]
+    public void Parse_SimpleVariable_StoredInVariables()
+    {
+        var pgm = Parse("diameter = 0.3\nG90\nG01X1Y0");
+        Assert.True(pgm.Variables.ContainsKey("diameter"));
+        Assert.Equal(0.3, pgm.Variables["diameter"].Value);
+        Assert.Equal("0.3", pgm.Variables["diameter"].Expression);
+    }
+
+    [Fact]
+    public void Parse_VariableWithInlineFlag()
+    {
+        var pgm = Parse("kerf = 0.06 inline\nG90\nG01X1Y0");
+        Assert.True(pgm.Variables["kerf"].Inline);
+        Assert.False(pgm.Variables["kerf"].Global);
+    }
+
+    [Fact]
+    public void Parse_VariableWithGlobalFlag()
+    {
+        var pgm = Parse("sheet_width = 48.0 global\nG90\nG01X1Y0");
+        Assert.True(pgm.Variables["sheet_width"].Global);
+        Assert.False(pgm.Variables["sheet_width"].Inline);
+    }
+
+    [Fact]
+    public void Parse_VariableWithBothFlags()
+    {
+        var pgm = Parse("speed = 200 global inline\nG90\nG01X1Y0");
+        Assert.True(pgm.Variables["speed"].Global);
+        Assert.True(pgm.Variables["speed"].Inline);
+    }
+
+    [Fact]
+    public void Parse_VariableReference_SubstitutedInCoordinate()
+    {
+        var pgm = Parse("width = 48.0\nG90\nG01X$widthY0");
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.Equal(48.0, linear.EndPoint.X);
+        Assert.Equal(0.0, linear.EndPoint.Y);
+    }
+
+    [Fact]
+    public void Parse_VariableReference_TrackedInVariableRefs()
+    {
+        var pgm = Parse("width = 48.0\nG90\nG01X$widthY0");
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.NotNull(linear.VariableRefs);
+        Assert.Equal("width", linear.VariableRefs["X"]);
+        Assert.False(linear.VariableRefs.ContainsKey("Y"));
+    }
+
+    [Fact]
+    public void Parse_VariableExpression_WithReference()
+    {
+        var pgm = Parse("diameter = 0.6\nradius = $diameter / 2\nG90\nG02X1Y0I$radiusJ0");
+        Assert.Equal(0.3, pgm.Variables["radius"].Value, 10);
+        var arc = (ArcMove)pgm.Codes[0];
+        Assert.Equal(0.3, arc.CenterPoint.X, 10);
+        Assert.Equal("radius", arc.VariableRefs["I"]);
+    }
+
+    [Fact]
+    public void Parse_FeedVariable_TrackedOnFeedrate()
+    {
+        var pgm = Parse("speed = 100\nG90\nF$speed\nG01X1Y0");
+        var feedrate = (Feedrate)pgm.Codes[0];
+        Assert.Equal(100.0, feedrate.Value);
+        Assert.Equal("speed", feedrate.VariableRef);
+    }
+
+    [Fact]
+    public void Parse_VariablesCollectedInPrepass_OrderIndependent()
+    {
+        var pgm = Parse("radius = $diameter / 2\ndiameter = 0.6\nG90\nG01X$radiusY0");
+        Assert.Equal(0.3, pgm.Variables["radius"].Value, 10);
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.Equal(0.3, linear.EndPoint.X, 10);
+    }
+
+    [Fact]
+    public void Parse_NoVariables_WorksAsNormal()
+    {
+        var pgm = Parse("G90\nG01X1.5Y2.5");
+        Assert.Empty(pgm.Variables);
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.Equal(1.5, linear.EndPoint.X);
+        Assert.Null(linear.VariableRefs);
+    }
+
+    [Fact]
+    public void Parse_RapidMove_WithVariableRef()
+    {
+        var pgm = Parse("start_x = 5.0\nG90\nG00X$start_xY0");
+        var rapid = (RapidMove)pgm.Codes[0];
+        Assert.Equal(5.0, rapid.EndPoint.X);
+        Assert.Equal("start_x", rapid.VariableRefs["X"]);
+    }
+
+    [Fact]
+    public void Parse_ArcMove_VariableOnMultipleAxes()
+    {
+        var pgm = Parse("r = 0.5\nG90\nG03X1Y0I$rJ$r");
+        var arc = (ArcMove)pgm.Codes[0];
+        Assert.Equal(0.5, arc.CenterPoint.X);
+        Assert.Equal(0.5, arc.CenterPoint.Y);
+        Assert.Equal("r", arc.VariableRefs["I"]);
+        Assert.Equal("r", arc.VariableRefs["J"]);
+    }
+
+    [Fact]
+    public void Parse_CaseInsensitive_VariableReference()
+    {
+        var pgm = Parse("Diameter = 0.3\nG90\nG01X$diameterY0");
+        var linear = (LinearMove)pgm.Codes[0];
+        Assert.Equal(0.3, linear.EndPoint.X);
+    }
+}

OpenNest/Actions/ActionLeadIn.cs

@@ -102,7 +102,7 @@ namespace OpenNest.Actions
                     snapPoint = closest;
                     snapEntity = entity;
                     snapContourType = info.ContourType;
-                    snapNormal = ContourCuttingStrategy.ComputeNormal(closest, entity, info.ContourType);
+                    snapNormal = ContourCuttingStrategy.ComputeNormal(closest, entity, info.ContourType, info.Winding);
                     hasSnap = true;
                     hoveredContour = info;
                 }
@@ -282,7 +282,7 @@ namespace OpenNest.Actions
             {
                 snapPoint = bestPoint;
                 snapEntity = bestEntity;
-                snapNormal = ContourCuttingStrategy.ComputeNormal(bestPoint, bestEntity, snapContourType);
+                snapNormal = ContourCuttingStrategy.ComputeNormal(bestPoint, bestEntity, snapContourType, hoveredContour.Winding);
                 activeSnapType = bestType;
             }
 
@@ -356,7 +356,8 @@ namespace OpenNest.Actions
                 contours.Add(new ShapeInfo
                 {
                     Shape = profile.Perimeter,
-                    ContourType = ContourType.External
+                    ContourType = ContourType.External,
+                    Winding = ContourCuttingStrategy.DetermineWinding(profile.Perimeter)
                 });
             }
 
@@ -366,7 +367,8 @@ namespace OpenNest.Actions
                 contours.Add(new ShapeInfo
                 {
                     Shape = cutout,
-                    ContourType = ContourCuttingStrategy.DetectContourType(cutout)
+                    ContourType = ContourCuttingStrategy.DetectContourType(cutout),
+                    Winding = ContourCuttingStrategy.DetermineWinding(cutout)
                 });
             }
         }
@@ -483,6 +485,7 @@ namespace OpenNest.Actions
         {
             public Shape Shape { get; set; }
             public ContourType ContourType { get; set; }
+            public RotationType Winding { get; set; }
         }
     }
 }

README.md

@@ -22,6 +22,7 @@ OpenNest takes your part drawings, lets you define your sheet (plate) sizes, and
 - **Lead-In/Lead-Out & Tabs** — Configurable approach paths, exit paths, and holding tabs for CNC cutting, with snap-to-endpoint/midpoint placement
 - **Contour & Program Editing** — Inline G-code editor with contour reordering, direction arrows, and cut direction reversal
 - **G-code Output** — Post-process nested layouts to G-code via plugin post-processors
+- **User-Defined Variables** — Define named variables in G-code (`diameter = 0.3`) referenced with `$name` syntax; Cincinnati post emits numbered machine variables (`#200`) so operators can adjust values at the control
 - **Built-in Shapes** — 12 parametric shapes (circles, rectangles, L-shapes, T-shapes, flanges, etc.) for quick testing or simple parts
 - **Interactive Editing** — Zoom, pan, select, clone, push, and manually arrange parts on the plate view
 - **Pluggable Engine Architecture** — Swap between built-in nesting engines or load custom engines from plugin DLLs
@@ -212,7 +213,7 @@ Custom post-processors implement the `IPostProcessor` interface and are auto-dis
 Nest files (`.nest`) are ZIP archives containing:
 
 - `nest.json` — JSON metadata: nest info, plate defaults, drawings (with bend data), and plates (with parts and cut-offs)
-- `programs/program-N` — G-code text for each drawing's cut program
+- `programs/program-N` — G-code text for each drawing's cut program (may include variable definitions and `$name` references)
 - `bestfits/bestfit-N` — Cached best-fit pair evaluation results (optional)
 
 ## Roadmap