FRLayoutAlgorithm.java: fix bug of ignoring layout height boundary while calculating node coordinates

jung-algorithms/src/main/java/edu/uci/ics/jung/layout/algorithms/FRLayoutAlgorithm.java

@@ -189,10 +189,11 @@ protected synchronized void calcPositions(N node) {
       positionX = layoutModel.getWidth() - borderWidth - random.nextDouble() * borderWidth * 2.0;
     }
 
-    if (positionY < borderWidth) {
-      positionY = borderWidth + random.nextDouble() * borderWidth * 2.0;
-    } else if (positionY > layoutModel.getWidth() - borderWidth * 2) {
-      positionY = layoutModel.getWidth() - borderWidth - random.nextDouble() * borderWidth * 2.0;
+    double borderHeight = layoutModel.getHeight() / 50.0;
+    if (positionY < borderHeight) {
+      positionY = borderHeight + random.nextDouble() * borderHeight * 2.0;
+    } else if (positionY > layoutModel.getHeight() - borderHeight * 2) {
+      positionY = layoutModel.getHeight() - borderHeight - random.nextDouble() * borderHeight * 2.0;
     }
 
     layoutModel.set(node, positionX, positionY);

jung-algorithms/src/test/java/edu/uci/ics/jung/layout/spatial/FRLayoutLocationsTest.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025, the JUNG Project and the Regents of the University
+ * of California.  All rights reserved.
+ *
+ * This software is open-source under the BSD license; see
+ * https://github.com/jrtom/jung/blob/master/LICENSE for a description.
+ */
+package edu.uci.ics.jung.layout.spatial;
+
+import com.google.common.graph.GraphBuilder;
+import com.google.common.graph.MutableGraph;
+import edu.uci.ics.jung.layout.algorithms.FRLayoutAlgorithm;
+import edu.uci.ics.jung.layout.model.LayoutModel;
+import edu.uci.ics.jung.layout.model.LoadingCacheLayoutModel;
+import edu.uci.ics.jung.layout.model.Point;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Tests the fix for incorrect Y-coordinate distribution in FRLayoutAlgorithm. Previously, nodes
+ * were arranged in a square (width × width), ignoring the configured layout height.
+ *
+ * <p>To verify the fix: 1. Generate enough nodes to exceed the layout bounds. 2. Ensure all nodes
+ * are positioned within the specified width * height area after layout.
+ *
+ * @author melanxoluk
+ */
+public class FRLayoutLocationsTest {
+  private static final int layoutWidth = 2000;
+  private static final int layoutHeight = 500;
+  private static final int iterations = 200;
+  private static final int nodes = 20;
+
+  @Test
+  public void testTargetCoordinates() {
+    MutableGraph<Integer> graph = GraphBuilder.directed().build();
+    LoadingCacheLayoutModel.Builder<Integer, ?> builder =
+        LoadingCacheLayoutModel.<Integer>builder()
+            .setGraph(graph)
+            .setSize(layoutWidth, layoutHeight);
+
+    LayoutModel<Integer> layoutModel = new FRLayoutsTest.TestLayoutModel<>(builder, iterations);
+
+    for (int i = 0; i < nodes; i++) {
+      graph.addNode(i);
+      layoutModel.set(i, Point.of(i, i));
+    }
+
+    FRLayoutAlgorithm algorithm = new FRLayoutAlgorithm();
+    layoutModel.accept(algorithm);
+
+    Assert.assertTrue(
+        "All points should has coordinates into target layout size",
+        layoutModel.getLocations().values().stream()
+            .allMatch(it -> it.y <= layoutHeight && it.x <= layoutWidth));
+  }
+}

jung-algorithms/src/test/java/edu/uci/ics/jung/layout/spatial/FRLayoutsTest.java

@@ -142,7 +142,7 @@ private static boolean closeEnough(Map<String, Point> left, Map<String, Point> r
    *
    * @param <T>
    */
-  private static class TestLayoutModel<T> extends LoadingCacheLayoutModel<T> {
+  public static class TestLayoutModel<T> extends LoadingCacheLayoutModel<T> {
 
     // how many steps
     private int steps;