Added some more hooks to the page editing pipeline. It should now be possible to add controls to the page editor, send the data from them out to the server, and process them on the server side.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>{#advanced_dlg.link_title}</title>
<script type="text/javascript" src="../../tiny_mce_popup.js"></script>
<script type="text/javascript" src="../../utils/mctabs.js"></script>
<script type="text/javascript" src="../../utils/form_utils.js"></script>
<script type="text/javascript" src="../../utils/validate.js"></script>
<script type="text/javascript" src="js/link.js"></script>
</head>
<body id="link" style="display: none">
<form onsubmit="LinkDialog.update();return false;" action="#">
<div class="tabs">
<ul>
<li id="general_tab" class="current"><span><a href="javascript:mcTabs.displayTab('general_tab','general_panel');" onmousedown="return false;">{#advanced_dlg.link_title}</a></span></li>
</ul>
</div>
<div class="panel_wrapper">
<div id="general_panel" class="panel current">
<table border="0" cellpadding="4" cellspacing="0">
<tr>
<td class="nowrap"><label for="href">{#advanced_dlg.link_url}</label></td>
<td><table border="0" cellspacing="0" cellpadding="0">
<tr>
<td><input id="href" name="href" type="text" class="mceFocus" value="" style="width: 200px" onchange="LinkDialog.checkPrefix(this);" /></td>
<td id="hrefbrowsercontainer"> </td>
</tr>
</table></td>
</tr>
<tr>
<td><label for="link_list">{#advanced_dlg.link_list}</label></td>
<td><select id="link_list" name="link_list" onchange="document.getElementById('href').value=this.options[this.selectedIndex].value;"></select></td>
</tr>
<tr>
<td><label id="targetlistlabel" for="targetlist">{#advanced_dlg.link_target}</label></td>
<td><select id="target_list" name="target_list"></select></td>
</tr>
<tr>
<td class="nowrap"><label for="linktitle">{#advanced_dlg.link_titlefield}</label></td>
<td><input id="linktitle" name="linktitle" type="text" value="" style="width: 200px" /></td>
</tr>
<tr>
<td><label for="class_list">{#class_name}</label></td>
<td><select id="class_list" name="class_list"></select></td>
</tr>
</table>
</div>
</div>
<div class="mceActionPanel">
<div style="float: left">
<input type="submit" id="insert" name="insert" value="{#insert}" />
</div>
<div style="float: right">
<input type="button" id="cancel" name="cancel" value="{#cancel}" onclick="tinyMCEPopup.close();" />
</div>
</div>
</form>
</body>
</html>