8321140: Add comment to note difference in Metal's JButton margins

Reviewed-by: honkar, aivanov

Author: Damon Nguyen

src/java.desktop/share/classes/javax/swing/plaf/basic/BasicLookAndFeel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2024, 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
@@ -727,6 +727,8 @@ public Object createValue(UIDefaults table) {
             "Button.highlight", controlLtHighlight,
             "Button.border", buttonBorder,
             "Button.margin", new InsetsUIResource(2, 14, 2, 14),
+            // The above margin has vastly larger horizontal values when
+            // compared to other look and feels that don't rely on these values
             "Button.textIconGap", 4,
             "Button.textShiftOffset", zero,
             "Button.focusInputMap", new UIDefaults.LazyInputMap(new Object[] {

src/java.desktop/share/classes/javax/swing/plaf/metal/MetalLookAndFeel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2024, 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
@@ -25,28 +25,53 @@
 
 package javax.swing.plaf.metal;
 
-import java.awt.*;
+import java.awt.Color;
+import java.awt.Component;
+import java.awt.Container;
+import java.awt.Frame;
+import java.awt.Insets;
+import java.awt.Toolkit;
+import java.awt.Window;
 import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
-import javax.swing.plaf.*;
-import javax.swing.*;
-import javax.swing.plaf.basic.*;
-import javax.swing.text.DefaultEditorKit;
-
-import java.awt.Color;
 import java.lang.ref.ReferenceQueue;
 import java.lang.ref.WeakReference;
-
 import java.security.AccessController;
 
-import sun.awt.*;
+import javax.swing.ButtonModel;
+import javax.swing.DefaultButtonModel;
+import javax.swing.Icon;
+import javax.swing.ImageIcon;
+import javax.swing.JComponent;
+import javax.swing.JDialog;
+import javax.swing.JFrame;
+import javax.swing.JRootPane;
+import javax.swing.JTextField;
+import javax.swing.JToggleButton;
+import javax.swing.LayoutStyle;
+import javax.swing.LookAndFeel;
+import javax.swing.SwingConstants;
+import javax.swing.SwingUtilities;
+import javax.swing.UIDefaults;
+import javax.swing.UIManager;
+import javax.swing.plaf.BorderUIResource;
+import javax.swing.plaf.ColorUIResource;
+import javax.swing.plaf.FontUIResource;
+import javax.swing.plaf.InsetsUIResource;
+import javax.swing.plaf.UIResource;
+import javax.swing.plaf.basic.BasicLookAndFeel;
+import javax.swing.text.DefaultEditorKit;
+
+import sun.awt.AppContext;
+import sun.awt.OSInfo;
+import sun.awt.SunToolkit;
 import sun.security.action.GetPropertyAction;
 import sun.swing.DefaultLayoutStyle;
-import static javax.swing.UIDefaults.LazyValue;
-
 import sun.swing.SwingAccessor;
 import sun.swing.SwingUtilities2;
 
+import static javax.swing.UIDefaults.LazyValue;
+
 /**
  * The Java Look and Feel, otherwise known as Metal.
  * <p>
@@ -782,6 +807,8 @@ protected void initComponentDefaults(UIDefaults table) {
                           "SPACE", "pressed",
                  "released SPACE", "released"
               }),
+            // Button default margin is (2, 14, 2, 14), defined in
+            // BasicLookAndFeel via "Button.margin" UI property.
 
             "CheckBox.disabledText", inactiveControlTextColor,
             "Checkbox.select", controlShadow,