8269921: TextFlow: listeners on bounds can throw NPE while computing text bounds

Reviewed-by: kcr, angorya

Author: FlorianKirmaier

modules/javafx.graphics/src/main/java/javafx/scene/text/Text.java

@@ -357,7 +357,7 @@ void layoutSpan(GlyphList[] runs) {
     BaseBounds getSpanBounds() {
         if (spanBoundsInvalid) {
             GlyphList[] runs = getRuns();
-            if (runs.length != 0) {
+            if (runs != null && runs.length != 0) {
                 float left = Float.POSITIVE_INFINITY;
                 float top = Float.POSITIVE_INFINITY;
                 float right = 0;

tests/system/src/test/java/test/javafx/scene/text/TextFlowCrashTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package test.javafx.scene.text;
+
+import javafx.application.Platform;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import javafx.stage.Stage;
+import javafx.scene.Node;
+import javafx.scene.Scene;
+import javafx.scene.control.Label;
+import javafx.scene.control.ListCell;
+import javafx.scene.control.ListView;
+import javafx.scene.control.ScrollPane;
+import javafx.scene.text.Text;
+import javafx.scene.text.TextFlow;
+import javafx.scene.layout.VBox;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import test.util.Util;
+
+public class TextFlowCrashTest {
+
+    private boolean exceptionWasThrown;
+
+    @BeforeAll
+    public static void initFX() throws Exception {
+        CountDownLatch startupLatch = new CountDownLatch(1);
+        Platform.startup(() -> {
+            Platform.setImplicitExit(false);
+            startupLatch.countDown();
+        });
+        assertTrue(startupLatch.await(15, TimeUnit.SECONDS), "Timeout waiting for FX runtime to start");
+    }
+
+    @Test
+    public void testTextflowCrash() {
+        Util.runAndWait(() -> {
+            Stage stage = new Stage();
+            VBox root = new VBox();
+            addBoundsListener(root);
+            Platform.runLater(() -> {
+                root.getChildren().add(getBuggyNode());
+            });
+            stage.setScene(new Scene(root,
+                    200,
+                    200));
+            stage.show();
+        });
+
+        Util.runAndWait(() -> {
+            assertFalse(exceptionWasThrown);
+        });
+    }
+
+    public ScrollPane getBuggyNode() {
+        ListView<String> listView = new ListView();
+        listView.getItems().add("AAA");
+        listView.setCellFactory((view) -> {
+            ListCell cell = new ListCell();
+            TextFlow flow = new TextFlow();
+            flow.getChildren().add(new Text("a"));
+            Text text2 = new Text("b");
+            text2.sceneProperty().addListener((p,o,n) -> {
+                try {
+                    text2.getBoundsInParent();
+                } catch (Throwable e) {
+                    exceptionWasThrown = true;
+                    throw e;
+                }
+            });
+            flow.getChildren().add(text2);
+            cell.setGraphic(flow);
+            addBoundsListener(cell);
+            return cell;
+        });
+        ScrollPane scrollPane = new ScrollPane(listView);
+        addBoundsListener(listView);
+        addBoundsListener(scrollPane);
+        return scrollPane;
+    }
+
+    public void addBoundsListener(Node node) {
+        node.boundsInParentProperty().addListener((p,o,n) -> {
+        });
+    }
+}