Pattern hatches with a predefined pattern (ANSI31, …) render as a solid fill

ACadSharp.Image.Tests/EntityRenderDispatcherTests.cs

@@ -390,6 +390,24 @@ public void PatternHatchDrawsClippedLines()
         Assert.All(surface.Styles, s => Assert.Null(s.DashPattern));
     }
 
+    [Fact]
+    public void PredefinedPatternHatchDrawsItsPatternRatherThanAFill()
+    {
+        // DXF group 76 (Hatch.PatternType) is 0 = user-defined, 1 = predefined, 2 = custom. ACadSharp names the value
+        // 1 "SolidFill", but a hatch read from a file with a predefined pattern such as ANSI31 carries exactly that
+        // value with IsSolid (group 70) false. Group 70 alone says whether a hatch is a solid fill.
+        RecordingDrawingSurface surface = new();
+        ImageConfiguration configuration = new();
+        EntityRenderDispatcher dispatcher = new(configuration);
+        Hatch hatch = SquareHatch(solid: false);
+        hatch.PatternType = HatchPatternType.SolidFill;
+
+        dispatcher.Draw(CreateContext(surface, configuration), hatch);
+
+        Assert.DoesNotContain(surface.Calls, c => c.StartsWith("FillPath", StringComparison.Ordinal));
+        Assert.InRange(surface.Calls.Count(c => c.StartsWith("DrawLine", StringComparison.Ordinal)), 5, 9);
+    }
+
     [Fact]
     public void PatternHatchIsCappedWithWarning()
     {

ACadSharp.Image/Rendering/EntityRenderDispatcher.cs

@@ -1689,7 +1689,10 @@ private void DrawHatch(ImageRenderContext context, ImageStyle style, Hatch hatch
         OcsTransform? toWorld = IsWorldPlane(hatch.Normal) ? null : OcsTransform.For(hatch.Normal);
         SurfacePoint ToSurface(XYZ point) => context.ToSurfacePoint(InsertPlacement.MapOcsPoint(placement, toWorld, hatch.Elevation, point));
 
-        if (hatch.IsSolid || hatch.PatternType == HatchPatternType.SolidFill)
+        // Only the solid-fill flag (DXF group 70) says a hatch is a fill. Hatch.PatternType is DXF group 76, whose value
+        // 1 means "predefined pattern" even though ACadSharp names it SolidFill: every hatch read from a file with a
+        // stock pattern such as ANSI31 carries it, and testing for it here filled all of those solid.
+        if (hatch.IsSolid)
         {
             List<IReadOnlyList<SurfacePoint>> rings = new();
             foreach (Hatch.BoundaryPath path in hatch.Paths)