Add TableEntity DXF round-trip (cells, alignment, merges, flow direction)

src/ACadSharp.Tests/IO/DXF/DxfWriterSingleObjectTests.cs

@@ -1,6 +1,8 @@
 using ACadSharp.Entities;
 using ACadSharp.IO;
+using ACadSharp.Objects;
 using CSMath;
+using System;
 using System.IO;
 using System.Linq;
 using Xunit;
@@ -54,6 +56,33 @@ public void WriteCasesAC1032(SingleCaseGenerator data)
 		this.writeDxfFile(data, ACadVersion.AC1032);
 	}
 
+	[Fact]
+	public void WriteFieldDateValue()
+	{
+		DateTime date = new DateTime(2026, 9, 30, 10, 15, 30, 250);
+
+		SingleCaseGenerator data = new SingleCaseGenerator();
+		data.FieldCadValues();
+
+		MText text = Assert.Single(data.Document.Entities.OfType<MText>());
+		Field field = text.XDictionary.GetEntry<CadDictionary>("ACAD_FIELD").GetEntry<Field>("TEXT");
+		CadValue dateValue = new CadValue();
+		dateValue.SetValue(date, CadValueType.Date);
+		field.Values.Add("date", dateValue);
+
+		using MemoryStream output = new MemoryStream();
+		DxfWriter.Write(output, data.Document);
+
+		using MemoryStream input = new MemoryStream(output.ToArray());
+		CadDocument result = DxfReader.Read(input);
+		Field writtenField = result.GetCadObject<Field>(field.Handle);
+
+		Assert.NotNull(writtenField);
+		Assert.True(writtenField.Values.TryGetValue("date", out CadValue value));
+		Assert.Equal(CadValueType.Date, value.ValueType);
+		Assert.Equal(date, value.Value);
+	}
+
 	[Theory]
 	[InlineData(-90, 270, -90, 270)]
 	[InlineData(180, 540, -180, 180)]

src/ACadSharp.Tests/IO/WriterSingleObjectTests.cs

@@ -101,6 +101,7 @@ static WriterSingleObjectTests()
 		Data.Add(new(nameof(SingleCaseGenerator.SingleMeshWithTextureCoordinates)));
 		Data.Add(new(nameof(SingleCaseGenerator.SingleMaterial)));
 		Data.Add(new(nameof(SingleCaseGenerator.LeaderWithArrowHead)));
+		Data.Add(new(nameof(SingleCaseGenerator.FieldCadValues)));
 	}
 
 	public WriterSingleObjectTests(ITestOutputHelper output) : base(output)
@@ -1699,6 +1700,68 @@ public void EntityTransparency()
 			};
 		}
 
+		public void FieldCadValues()
+		{
+			MText text = new MText();
+			text.Value = "cad values";
+			this.Document.Entities.Add(text);
+
+			Field field = new Field();
+			field.EvaluatorId = "_text";
+			field.FieldCode = "cad values";
+			field.FormatString = string.Empty;
+			field.Value.SetValue("cad values", CadValueType.String);
+
+			CadValue unknownEmpty = new CadValue();
+			unknownEmpty.IsEmpty = true;
+			field.Values.Add("unknown_empty", unknownEmpty);
+
+			//Unknown value that is not empty, as read from a pre R2007 dwg
+			CadValue unknown = new CadValue();
+			unknown.SetValue(0);
+			field.Values.Add("unknown", unknown);
+
+			CadValue longValue = new CadValue();
+			longValue.SetValue(42, CadValueType.Long);
+			field.Values.Add("long", longValue);
+
+			CadValue doubleValue = new CadValue();
+			doubleValue.SetValue(0.5, CadValueType.Double);
+			field.Values.Add("double", doubleValue);
+
+			CadValue stringValue = new CadValue();
+			stringValue.SetValue("text value", CadValueType.String);
+			field.Values.Add("string", stringValue);
+
+			CadValue pointValue = new CadValue();
+			pointValue.SetValue(new XYZ(1, 2, 3), CadValueType.Point3D);
+			field.Values.Add("point", pointValue);
+
+			CadDictionary dict = text.CreateExtendedDictionary();
+			CadDictionary fields = new CadDictionary("ACAD_FIELD");
+			dict.Add(fields);
+			fields.Add("TEXT", field);
+
+			this.AssertRoundtrip = (doc) =>
+			{
+				if (this.Format == CadFileFormat.DWG)
+				{
+					return;
+				}
+
+				Field result = doc.GetCadObject<Field>(field.Handle);
+
+				Assert.NotNull(result);
+				foreach (var item in field.Values)
+				{
+					Assert.True(result.Values.TryGetValue(item.Key, out CadValue value), $"Value {item.Key} not found");
+					Assert.Equal(item.Value.ValueType, value.ValueType);
+					Assert.Equal(item.Value.IsEmpty, value.IsEmpty);
+					Assert.Equal(item.Value.Value, value.Value);
+				}
+			};
+		}
+
 		public void GenerateExampleDxf()
 		{
 			this.Document.Header.UnitMode = (short)ACadSharp.Types.Units.UnitsType.Millimeters;

src/ACadSharp/CadUtils.cs

@@ -1,6 +1,8 @@
-using CSUtilities.Text;
+using CSUtilities.Converters;
+using CSUtilities.Text;
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text;
 
@@ -364,4 +366,44 @@ public static void DateToJulian(DateTime date, out int jdate, out int milisecond
 		jdate = date.Day + (int)System.Math.Floor((153.0 * (double)(month + 12 * day - 3) + 2.0) / 5.0) + 365 * year + (int)System.Math.Floor((double)year / 4.0) - (int)System.Math.Floor((double)year / 100.0) + (int)System.Math.Floor((double)year / 400.0) - 32045;
 		miliseconds = date.Millisecond + date.Second * 1000 + date.Minute * 60000 + date.Hour * 3600000;
 	}
+
+	/// <summary>
+	/// Converts a date into the 16 bytes of a SYSTEMTIME structure: year, month, day of the week, day, hour, minute, second and millisecond, each one as a little endian short.
+	/// </summary>
+	/// <param name="date">The date to convert.</param>
+	/// <returns>The 16 bytes that represent the date.</returns>
+	public static byte[] ToSystemTime(DateTime date)
+	{
+		byte[] array = new byte[16];
+		var stream = new MemoryStream(array);
+
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Year), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Month), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.DayOfWeek), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Day), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Hour), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Minute), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Second), 0, 2);
+		stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Millisecond), 0, 2);
+
+		return array;
+	}
+
+	/// <summary>
+	/// Converts the 16 bytes of a SYSTEMTIME structure into a date. The day of the week is ignored.
+	/// </summary>
+	/// <param name="array">The 16 bytes that represent the date.</param>
+	/// <returns>The date represented by the bytes.</returns>
+	public static DateTime FromSystemTime(byte[] array)
+	{
+		int year = LittleEndianConverter.Instance.ToInt16(array, 0);
+		int month = LittleEndianConverter.Instance.ToInt16(array, 2);
+		int day = LittleEndianConverter.Instance.ToInt16(array, 6);
+		int hour = LittleEndianConverter.Instance.ToInt16(array, 8);
+		int minute = LittleEndianConverter.Instance.ToInt16(array, 10);
+		int second = LittleEndianConverter.Instance.ToInt16(array, 12);
+		int millisecond = LittleEndianConverter.Instance.ToInt16(array, 14);
+
+		return new DateTime(year, month, day, hour, minute, second, millisecond);
+	}
 }

src/ACadSharp/IO/DWG/DwgStreamReaders/DwgObjectReader.Entities.cs

@@ -192,17 +192,7 @@ private void readCustomTableData(CustomDataEntry entry)
 			switch (size)
 			{
 				case 16:
-					{
-						int year = LittleEndianConverter.Instance.ToInt16(array, 0);
-						int month = LittleEndianConverter.Instance.ToInt16(array, 2);
-						int day = LittleEndianConverter.Instance.ToInt16(array, 6);
-						int hour = LittleEndianConverter.Instance.ToInt16(array, 8);
-						int minute = LittleEndianConverter.Instance.ToInt16(array, 10);
-						int second = LittleEndianConverter.Instance.ToInt16(array, 12);
-						int millisecond = LittleEndianConverter.Instance.ToInt16(array, 14);
-
-						return new System.DateTime(year, month, day, hour, minute, second, millisecond);
-					}
+					return CadUtils.FromSystemTime(array);
 				case 14:
 					{
 						int year = LittleEndianConverter.Instance.ToInt16(array, 0);

src/ACadSharp/IO/DWG/DwgStreamWriters/DwgObjectWriter.Objects.cs

@@ -829,17 +829,7 @@ private void writeDateCadValue(System.DateTime? date)
 			byte[] array;
 			if (this.R2007Plus)
 			{
-				array = new byte[16];
-				var stream = new MemoryStream(array);
-
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Year), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Month), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.DayOfWeek), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Day), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Hour), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Minute), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Second), 0, 2);
-				stream.Write(LittleEndianConverter.Instance.GetBytes((short)date.Value.Millisecond), 0, 2);
+				array = CadUtils.ToSystemTime(date.Value);
 			}
 			else
 			{

src/ACadSharp/IO/DXF/DxfStreamReader/DxfSectionReaderBase.cs

@@ -546,7 +546,18 @@ private bool readTableEntity(CadEntityTemplate template, DxfMap map, string subc
 				tmp.CurrentCell.Rotation = this._reader.ValueAsDouble;
 				return true;
 			case 170:
-				//Has data flag
+				// Per-cell alignment (set when the cell flag at code 91 has the
+				// CellAlignment override bit). Capture it on the cell-level
+				// StyleOverride so callers reading the table back via DXF can
+				// resolve alignment exactly like they do through DWG.
+				if (tmp.CurrentCell != null)
+				{
+					tmp.CurrentCell.StyleOverride.HasData = true;
+					tmp.CurrentCell.StyleOverride.CellAlignment =
+						(ACadSharp.Objects.TableStyle.CellAlignmentType)this._reader.ValueAsShort;
+					tmp.CurrentCell.StyleOverride.PropertyOverrideFlags |=
+						ACadSharp.Objects.TableStyle.CellStylePropertyFlags.Alignment;
+				}
 				return true;
 			case 171:
 				tmp.CreateCell((TableEntity.CellType)this._reader.ValueAsInt);
@@ -572,6 +583,18 @@ private bool readTableEntity(CadEntityTemplate template, DxfMap map, string subc
 			case 179:
 				//Unknown value
 				return true;
+			case 70:
+				// Table-level flow direction (0 = top to bottom, 1 = bottom to top).
+				// Stored on the table-level CellStyleOverride so callers can read it
+				// through the same API used for round-tripping the rest of the
+				// override flags.
+				if (this._reader.ValueAsShort == 1)
+				{
+					table.CellStyleOverride.HasData = true;
+					table.CellStyleOverride.TableCellStylePropertyFlags |=
+						ACadSharp.Objects.TableStyle.CellStylePropertyFlags.FlowDirectionBottomToTop;
+				}
+				return true;
 			case 301:
 				content = new TableEntity.CellContent();
 				var contentTemplate = new CadTableCellContentTemplate(content);
@@ -634,12 +657,24 @@ protected CadValueTemplate readCadValue(CadValue value)
 				case 91:
 					value.SetValue(this._reader.ValueAsInt);
 					break;
+				case 92:
+					//Size of the date data in 310
+					break;
 				case 93:
 					value.Flags = this._reader.ValueAsInt;
 					break;
 				case 140:
 					value.SetValue(this._reader.ValueAsDouble);
 					break;
+				case 310 when value.ValueType == CadValueType.Date:
+					{
+						byte[] array = this._reader.ValueAsBinaryChunk;
+						if (array.Length == 16)
+						{
+							value.SetValue(CadUtils.FromSystemTime(array));
+						}
+					}
+					break;
 				case 330:
 					template.ValueHandle = this._reader.ValueAsHandle;
 					break;