Test both directions when checking for segment equality

r-flash · Oct 27, 2024 · a435a3d · a435a3d
1 parent 2615b4a
commit a435a3d
Showing 1 changed file with 19 additions and 1 deletion.
diff --git a/src/path-boolean.ts b/src/path-boolean.ts
@@ -358,6 +358,7 @@ function findVertices(
                     }
                     break;
                 case "A":
+                    // TODO: explain
                     if (edge.seg[5] === false) {
                         return [];
                     }
@@ -366,7 +367,6 @@ function findVertices(
         }
 
         const vertexPairId = `${getVertexId(startVertex)}:${getVertexId(endVertex)}`;
-        // TODO: check other direction
         if (hasOwn(vertexPairIdToEdges, vertexPairId)) {
             const existingEdge = vertexPairIdToEdges[vertexPairId].find(
                 (other) => segmentsEqual(other[0].seg, edge.seg, EPS.point),
@@ -378,6 +378,24 @@ function findVertices(
             }
         }
 
+        const vertexPairIdInv = `${getVertexId(endVertex)}:${getVertexId(startVertex)}`;
+        if (hasOwn(vertexPairIdToEdges, vertexPairIdInv)) {
+            const reversedSeg = reversePathSegment(edge.seg);
+            const existingEdge = vertexPairIdToEdges[vertexPairIdInv].find(
+                (other) => segmentsEqual(other[0].seg, reversedSeg, EPS.point),
+            );
+            if (existingEdge) {
+                if (existingEdge[0].parent === edge.parent) {
+                    // discard "there and back" pairs
+                    return [];
+                }
+
+                existingEdge[1].parent |= edge.parent;
+                existingEdge[2].parent |= edge.parent;
+                return [];
+            }
+        }
+
         const fwdEdge: MajorGraphEdge = {
             ...edge,
             incidentVertices: [startVertex, endVertex],