if (keyCode == Keyboard.KeyCode.A) {
textArea.setSelection(0, document.getCharacterCount());
} else if (keyCode == Keyboard.KeyCode.X) {
textArea.cut();
} else if (keyCode == Keyboard.KeyCode.C) {
textArea.copy();
} else if (keyCode == Keyboard.KeyCode.V) {
textArea.paste();
} else if (keyCode == Keyboard.KeyCode.Z) {
if (Keyboard.isPressed(Keyboard.Modifier.SHIFT)) {
textArea.undo();