fgdata/gui/dialogs/chat_full.xml

<?xml version="1.0"?>

<PropertyList>
  <name>chat-full</name>
  <modal>false</modal>
  <layout>vbox</layout>
  <resizable>true</resizable>

  <group>
    <layout>hbox</layout>

    <button>
      <legend>-</legend>
      <pref-width>16</pref-width>
      <pref-height>16</pref-height>
      <border>2</border>
      <key>-</key>
      <binding>
       <command>dialog-show</command>
       <dialog-name>chat</dialog-name>
      </binding>
      <binding>
        <command>dialog-close</command>
      </binding>
    </button>

    <empty><stretch>1</stretch></empty>

    <text>
      <label>Multiplayer Chat</label>
    </text>

    <empty><stretch>1</stretch></empty>

    <button>
      <legend></legend>
      <pref-width>16</pref-width>
      <pref-height>16</pref-height>
      <border>2</border>
      <keynum>27</keynum>
      <binding>
        <command>dialog-close</command>
      </binding>
    </button>
  </group>

  <hrule/>

  <textbox>
    <halign>fill</halign>
    <valign>fill</valign>
    <stretch>true</stretch>
    <pref-width>450</pref-width>
    <pref-height>120</pref-height>
    <padding>5</padding>
    <slider>20</slider>
    <live>true</live>
    <wrap>true</wrap>
    <editable>false</editable>
    <top-line>-1</top-line>
    <property>/sim/multiplay/chat-history</property>
  </textbox>

  <group>
    <layout>hbox</layout>
    <padding>4</padding>

    <input>
      <name>compose</name>
      <stretch>true</stretch>
      <halign>fill</halign>
      <stretch>true</stretch>
      <length>50</length>
      <pref-width>500</pref-width>
      <property>/sim/multiplay/chat-compose</property>
    </input>

    <button>
      <legend>Send</legend>
      <default>true</default>
      <key>Enter</key>
      <binding>
        <command>dialog-apply</command>
      </binding>
      <binding>
        <command>nasal</command>
        <script>
          var lchat = getprop("/sim/multiplay/chat-compose");
          if (lchat != "")
          {
            setprop("/sim/multiplay/chat", lchat);
            setprop("/sim/multiplay/chat-compose", "");
            gui.dialog_update("chat-full", "compose");
          }
        </script>
      </binding>
    </button>
  </group>
</PropertyList>