Update UILoader.

Author: gk-brown

sierra/src/main/java/org/httprpc/sierra/UILoader.java

@@ -19,7 +19,9 @@
 import org.httprpc.kilo.io.Encoder;
 
 import javax.imageio.ImageIO;
+import javax.swing.AbstractAction;
 import javax.swing.AbstractButton;
+import javax.swing.Action;
 import javax.swing.ButtonGroup;
 import javax.swing.Icon;
 import javax.swing.JButton;
@@ -43,11 +45,13 @@
 import javax.swing.JTextField;
 import javax.swing.JToggleButton;
 import javax.swing.JTree;
+import javax.swing.KeyStroke;
 import javax.swing.SwingConstants;
 import javax.swing.UIManager;
 import javax.swing.border.CompoundBorder;
 import javax.swing.border.EmptyBorder;
 import javax.swing.border.LineBorder;
+import javax.swing.undo.UndoManager;
 import javax.xml.stream.Location;
 import javax.xml.stream.XMLInputFactory;
 import javax.xml.stream.XMLStreamConstants;
@@ -57,6 +61,9 @@
 import java.awt.Dimension;
 import java.awt.Font;
 import java.awt.Image;
+import java.awt.event.ActionEvent;
+import java.awt.event.InputEvent;
+import java.awt.event.KeyEvent;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -341,12 +348,39 @@ void declareAttributeList(String tag, Class<?> type, Writer writer) throws IOExc
     private static final String REVERT = "revert";
     private static final String PERSIST = "persist";
 
-    private static Map<String, Class<?>> types = new HashMap<>();
-    private static Map<String, Supplier<? extends JComponent>> suppliers = new HashMap<>();
+    private static final String UNDO_ACTION_KEY = "undo";
 
-    private static Map<String, Color> colors = new HashMap<>();
+    private static final Map<String, Class<?>> types = new HashMap<>();
+    private static final Map<String, Supplier<? extends JComponent>> suppliers = new HashMap<>();
 
-    private static Map<String, Font> fonts = new HashMap<>();
+    private static final Map<String, Color> colors = new HashMap<>();
+
+    private static final Map<String, Font> fonts = new HashMap<>();
+
+    private static final UndoManager undoManager = new UndoManager();
+
+    private static final Action undoAction = new AbstractAction() {
+        @Override
+        public void actionPerformed(ActionEvent event) {
+            if (undoManager.canUndo()) {
+                undoManager.undo();
+            }
+        }
+    };
+
+    private static final KeyStroke undoKeyStroke;
+    static {
+        var osName = System.getProperty("os.name").toLowerCase();
+
+        int modifier;
+        if (osName.contains("mac")) {
+            modifier = InputEvent.META_DOWN_MASK;
+        } else {
+            modifier = InputEvent.CTRL_DOWN_MASK;
+        }
+
+        undoKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_Z, modifier);
+    }
 
     static {
         bind("label", JLabel.class, JLabel::new);
@@ -365,7 +399,16 @@ void declareAttributeList(String tag, Class<?> type, Writer writer) throws IOExc
         bind("separator", JSeparator.class, JSeparator::new);
         bind("scroll-pane", JScrollPane.class, JScrollPane::new);
         bind("list", JList.class, JList::new);
-        bind("text-area", JTextArea.class, JTextArea::new);
+        bind("text-area", JTextArea.class, () -> {
+            var textArea = new JTextArea();
+
+            textArea.getDocument().addUndoableEditListener(undoManager);
+
+            textArea.getActionMap().put(UNDO_ACTION_KEY, undoAction);
+            textArea.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(undoKeyStroke, UNDO_ACTION_KEY);
+
+            return textArea;
+        });
         bind("table", JTable.class, JTable::new);
         bind("tree", JTree.class, JTree::new);