From 1fbb9216a075d808e37417aa90d5ec5cf137fc42 Mon Sep 17 00:00:00 2001
From: xivk <ben@anyways.eu>
Date: Tue, 14 Nov 2023 10:32:35 +0100
Subject: [PATCH] Fixed obscure issue when lon/lat diff are exactly the same.

---
 NetTopologySuite.IO.VectorTiles.Common.props  |  2 +-
 .../Tilers/Shared.cs                          | 16 ++++++++--------
 .../Tilers/LineStringTilerTests.cs            | 19 +++++++++++++++++--
 3 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/NetTopologySuite.IO.VectorTiles.Common.props b/NetTopologySuite.IO.VectorTiles.Common.props
index 22eaaad..19e5054 100644
--- a/NetTopologySuite.IO.VectorTiles.Common.props
+++ b/NetTopologySuite.IO.VectorTiles.Common.props
@@ -6,7 +6,7 @@
     <LangVersion>latest</LangVersion>
     <Authors>NetTopologySuite - Team</Authors>
     <Owners>NetTopologySuite - Team</Owners>
-    <PackageVersion>1.0.2</PackageVersion>
+    <PackageVersion>1.0.3</PackageVersion>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <RepositoryUrl>https://github.com/NetTopologySuite/NetTopologySuite.IO.VectorTiles</RepositoryUrl>
 	<PackageIcon>icon.png</PackageIcon>
diff --git a/src/NetTopologySuite.IO.VectorTiles/Tilers/Shared.cs b/src/NetTopologySuite.IO.VectorTiles/Tilers/Shared.cs
index 182a6f1..8a9455c 100644
--- a/src/NetTopologySuite.IO.VectorTiles/Tilers/Shared.cs
+++ b/src/NetTopologySuite.IO.VectorTiles/Tilers/Shared.cs
@@ -19,20 +19,20 @@ internal static class Shared
         {
             double xDiff = x2 - x1;
             double yDiff = y2 - y1;
-            
-            if (Math.Abs(xDiff) <= double.Epsilon && 
+
+            if (Math.Abs(xDiff) <= double.Epsilon &&
                 Math.Abs(yDiff) <= double.Epsilon) yield break;
-            
-            if (Math.Abs(xDiff) > Math.Abs(yDiff))
+
+            if (Math.Abs(xDiff) >= Math.Abs(yDiff))
             { // we take x as denominator.
                 int yPrevious = (int)Math.Floor(y1);
                 int xPrevious = (int)Math.Floor(x1);
                 int xLast = (int) Math.Floor(x2);
                 int yLast = (int) Math.Floor(y2);
-                
+
                 double slope = (yDiff / xDiff);
                 double y0 = y1 - (slope * x1);
-                
+
                 // with an increment of 1 we calculate y.
                 bool right = xDiff > 0;
                 // var up = (yDiff > 0);
@@ -42,12 +42,12 @@ internal static class Shared
                 yield return (xPrevious, yPrevious);
                 for (int x = start; x != end + xStep; x += xStep)
                 {
-                    // REMARK: this can be more efficient but this way numerically more stable. 
+                    // REMARK: this can be more efficient but this way numerically more stable.
                     // we prefer correctness over performance here.
                     // calculate next y.
                     double y = x * slope + y0;
                     int yRounded = (int)Math.Floor(y);
-                    
+
                     if (yPrevious != yRounded)
                     {
                         // we have moved to a new y
diff --git a/test/NetTopologySuite.IO.VectorTiles.Tests/Tilers/LineStringTilerTests.cs b/test/NetTopologySuite.IO.VectorTiles.Tests/Tilers/LineStringTilerTests.cs
index 2809600..5e09f59 100644
--- a/test/NetTopologySuite.IO.VectorTiles.Tests/Tilers/LineStringTilerTests.cs
+++ b/test/NetTopologySuite.IO.VectorTiles.Tests/Tilers/LineStringTilerTests.cs
@@ -133,7 +133,7 @@ public void LineStringTiler_Cut_LineString_CutAt21_ShouldBeCutIn0OrMore()
                 }
             }
         }
-        
+
         [Fact]
         public void LineStringTiler_Cut_LineString_CutAt22_ShouldBeCutIn0OrMore()
         {
@@ -200,7 +200,7 @@ public void LineStringTiler_Tiles_LineStringInMultipleTiles_Zoom13_ShouldBeInEac
             });
 
             var tiles = lineString.Tiles(13).ToList();
-            
+
             Assert.Equal(5, tiles.Count);
             Assert.Equal(44869043UL, tiles[0]);
             Assert.Equal(44860851UL, tiles[1]);
@@ -208,5 +208,20 @@ public void LineStringTiler_Tiles_LineStringInMultipleTiles_Zoom13_ShouldBeInEac
             Assert.Equal(44852660UL, tiles[3]);
             Assert.Equal(44852661UL, tiles[4]);
         }
+
+        [Fact]
+        public void LineStringTile_Tiles_Regression_ExactLonLatDiff_Zoom14_ShouldReturnTiles()
+        {
+            var reader = new WKTReader();
+            var lineString =
+                reader.Read(
+                        "LINESTRING (-61.122810782967036 -34.2440222744931, -61.144767342032964 -34.225843342865723)")
+                    as
+                    LineString;
+
+
+            var tiles = lineString.Tiles(14).ToList();
+            Assert.NotEmpty(tiles);
+        }
     }
 }