JBR-3835 Cropped messages in all Message Dialogs in Idea on Ubuntu 18.04.5 LTS with swing alerts enabled

The _NET_FRAME_EXTENTS property that is used to obtain the initial
insets of a dialog window does not immediately get its value and may be
returned as 0 if queried too soon after the window creation.

In order to avoid (incorrect) guessing of dialog's insets, make 3
attempts at getting the insets with a small but increasing pause
in between them.

src/java.desktop/unix/classes/sun/awt/X11/XWM.java

@@ -1481,9 +1481,21 @@ final class XWM
         }
         XNETProtocol net_protocol = getWM().getNETProtocol();
         if (net_protocol != null && net_protocol.active()) {
-            Insets insets = getInsetsFromProp(window, XA_NET_FRAME_EXTENTS);
-            if (insLog.isLoggable(PlatformLogger.Level.FINE)) {
-                insLog.fine("_NET_FRAME_EXTENTS: {0}", insets);
+            Insets insets = null;
+            final int MAX_RETRY_COUNT = 3;
+            for (int i = 0; i < MAX_RETRY_COUNT; i++) {
+                insets = getInsetsFromProp(window, XA_NET_FRAME_EXTENTS);
+                if (insLog.isLoggable(PlatformLogger.Level.FINE)) {
+                    insLog.fine("_NET_FRAME_EXTENTS: {0}", insets);
+                }
+                if (insets == null) {
+                    final long timeForInsetExtentToBecomeReadyMs = (i + 1)*5;
+                    insLog.fine("_NET_FRAME_EXTENTS not available (yet?), retrying in {0} ms",
+                                timeForInsetExtentToBecomeReadyMs);
+                    try {
+                        Thread.sleep(timeForInsetExtentToBecomeReadyMs);
+                    } catch (InterruptedException ignored) {}
+                }
             }
 
             if (insets != null) {

test/jdk/java/awt/Insets/DialogInsets.java

@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2021, JetBrains s.r.o.. 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.
+ *
+ * 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.
+ */
+
+/**
+ * @test
+ * @key headful
+ * @summary Verifies that JDialog's insets are the same every time the dialog is created.
+ * @requires (os.family == "linux")
+ * @run main DialogInsets
+ */
+
+import javax.swing.JDialog;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.SwingConstants;
+import javax.swing.SwingUtilities;
+import javax.swing.Timer;
+import javax.swing.WindowConstants;
+import java.awt.Frame;
+import java.awt.Insets;
+import java.awt.Robot;
+import java.awt.event.ActionEvent;
+import java.lang.reflect.InvocationTargetException;
+
+public class DialogInsets {
+    private static Robot robot;
+    private static Insets insets;
+
+    public static void main(String[] args) throws Exception {
+        robot = new Robot();
+
+        final JFrame frame = new JFrame("Test Dialog Demo");
+        frame.setBounds(100, 100, 400, 300);
+        frame.setVisible(true);
+
+        robot.delay(300);
+
+        for (int i = 0; i < 16; i++) {
+            runSwing(() -> showDialog(frame));
+            robot.delay(300);
+        }
+
+        runSwing( () -> frame.dispose() );
+    }
+
+    private static void showDialog(Frame parent) {
+        final JLabel content = new JLabel("test label", SwingConstants.CENTER);
+        final JDialog dialog = new JDialog(parent, "Test Dialog", true);
+
+        if (insets == null) {
+            // Slow down the first time in order to increase the chance to get the right insets.
+           robot.delay(300);
+        }
+
+        dialog.setContentPane(content);
+        dialog.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
+        dialog.setResizable(false);
+        dialog.pack();
+
+        final Insets localInsets = dialog.getInsets();
+        System.out.println(localInsets);
+
+        if (insets == null) {
+            insets = localInsets;
+        } else if (!insets.equals(localInsets)) {
+            throw new RuntimeException("insets differ (" + insets + " before, " + localInsets + " now)");
+        }
+
+        final Timer closeTimer = new Timer(300, (ActionEvent event) -> { dialog.setVisible(false); dialog.dispose(); } );
+        closeTimer.setRepeats(false);
+        closeTimer.start();
+
+        dialog.setLocationRelativeTo(parent);
+        dialog.setVisible(true);
+    }
+
+    private static void runSwing(Runnable r) {
+        try {
+            SwingUtilities.invokeAndWait(r);
+        } catch (InterruptedException ignored) {
+        } catch (InvocationTargetException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}