Index: roundcubemail/program/js/list.js
===================================================================
--- roundcubemail/program/js/list.js	(revision 2308)
+++ roundcubemail/program/js/list.js	(working copy)
@@ -77,7 +77,7 @@
     for(var r=0; r<this.list.tBodies[0].childNodes.length; r++)
     {
       row = this.list.tBodies[0].childNodes[r];
-      while (row && (row.nodeType != 1 || row.style.display == 'none'))
+      while (row && row.nodeType != 1)
       {
         row = row.nextSibling;
         r++;
@@ -118,6 +118,10 @@
     if (document.all)
       row.onselectstart = function() { return false; };
 
+    var expando = document.getElementById('rcmexpando' + uid);
+    if (expando != null)
+      expando.onmousedown = function(e) { return p.expando_clicked(e, uid); };
+
     this.row_init(this.rows[uid]);
   }
 },
@@ -319,6 +323,85 @@
 },
 
 
+expando_clicked: function(e, id)
+{
+  var row = this.rows[id];
+  var evtarget = rcube_event.get_target(e);
+  // Don't select this message
+  this.dont_select = true;
+  // Don't treat double click on the expando as double click on the message.
+  row.clicked = 0;
+  if (row.expanded) {
+    evtarget.className = "collapsed";
+    this.collapse(row);
+  } else {
+    evtarget.className = "expanded";
+    this.expand(row);
+  }
+},
+
+
+collapse: function(row)
+{
+    row.expanded = false;
+    var depth = row.depth;
+    var new_row = row ? row.obj.nextSibling : null;
+    var r;
+    while (new_row) {
+        if (new_row.nodeType == 1) {
+            var r = this.rows[new_row.uid];
+            if (r &&r.depth <= depth)
+                break;
+            new_row.style.display = 'none';
+        }
+        new_row = new_row.nextSibling;
+    }
+    return false;
+},
+
+
+expand: function(row)
+{
+    var depth, new_row;
+    if (row) {
+        row.expanded = true;
+        depth = row.depth;
+        new_row = row.obj.nextSibling;
+    } else {
+        var tbody = this.list.tBodies[0];
+        new_row = tbody.firstChild;
+        depth = 0;
+    }
+    var current_expand = true;
+    var current_depth = depth;
+    var expand_stack = new Array();
+    var depth_stack = new Array();
+    while (new_row) {
+        if (new_row.nodeType == 1) {
+            var r = this.rows[new_row.uid];
+            if (r) {
+                if (r.depth <= depth)
+                    break;
+                while (r.depth <= current_depth) {
+                    current_expand = expand_stack.pop();
+                    current_depth = depth_stack.pop();
+                }
+                if (current_expand)
+                     new_row.style.display = 'table-row';
+                if (r.has_children) {
+                    expand_stack.push(current_expand);
+                    depth_stack.push(current_depth);
+                    current_expand = r.expanded;
+                    current_depth = r.depth;
+                }
+            }
+        }
+        new_row = new_row.nextSibling;
+    }
+    return false;
+},
+
+
 /**
  * get next/previous/last rows that are not hidden
  */
Index: roundcubemail/program/js/app.js
===================================================================
--- roundcubemail/program/js/app.js	(revision 2308)
+++ roundcubemail/program/js/app.js	(working copy)
@@ -381,6 +381,9 @@
       row.replied = this.env.messages[uid].replied ? true : false;
       row.flagged = this.env.messages[uid].flagged ? true : false;
       row.forwarded = this.env.messages[uid].forwarded ? true : false;
+      row.has_children = this.env.messages[uid].has_children ? true : false;
+      row.expanded = this.env.messages[uid].expanded ? true : false;
+      row.depth = this.env.messages[uid].depth;
       }
 
     // set eventhandler to message icon
@@ -397,7 +400,7 @@
       {
       var found;
       if((found = find_in_array('flag', this.env.coltypes)) >= 0)
-          this.set_env('flagged_col', found+1);
+          this.set_env('flagged_col', found);
       }
 
     // set eventhandler to flag icon, if icon found
@@ -409,6 +412,15 @@
       row.flagged_icon._row = row.obj;
       row.flagged_icon.onmousedown = function(e) { p.command('toggle_flag', this); };
       }
+      
+    // expando is handled here rather than in rcube_list_widget so that the
+    // expanded state may be persisted in this.env.messages
+    var expando = document.getElementById('rcmexpando' + uid);
+    if (expando != null) 
+      {
+      var p = this;
+      expando.onmousedown = function(e) { return p.expando_clicked(e, uid); };
+      }
   };
 
   // init message compose form: set focus and eventhandlers
@@ -1976,6 +1988,13 @@
   };
   
   
+  this.expando_clicked = function(e, id)
+  {
+    this.message_list.expando_clicked(e, id);
+    this.env.messages[id].expanded = this.message_list.rows[id].expanded;
+  },
+  
+  
   /*********************************************************/
   /*********           login form methods          *********/
   /*********************************************************/
@@ -3475,7 +3494,7 @@
     for (var n=0; thead && n<this.coltypes.length; n++) 
       {
       col = this.coltypes[n];
-      if ((cell = thead.rows[0].cells[n+1]) && (col=='from' || col=='to'))
+      if ((cell = thead.rows[0].cells[n]) && (col=='from' || col=='to'))
         {
         // if we have links for sorting, it's a bit more complicated...
         if (cell.firstChild && cell.firstChild.tagName=='A')
@@ -3490,7 +3509,7 @@
         cell.id = 'rcm'+col;
         }
       else if (col == 'subject' && this.message_list)
-        this.message_list.subject_col = n+1;
+        this.message_list.subject_col = n;
       }
   };
 
@@ -3503,12 +3522,19 @@
     var tbody = this.gui_objects.messagelist.tBodies[0];
     var rowcount = tbody.rows.length;
     var even = rowcount%2;
+    var depth = cols['depth'];
     
-    this.env.messages[uid] = {deleted:flags.deleted?1:0,
-                              replied:flags.replied?1:0,
-                              unread:flags.unread?1:0,
-			      forwarded:flags.forwarded?1:0,
-                              flagged:flags.flagged?1:0};
+    // don't overwrite the existing values - we want to preserve expanded
+    var message = this.env.messages[uid];
+    if (!message)
+        message = this.env.messages[uid] = Array();
+    message.deleted = flags.deleted?1:0;
+    message.replied = flags.replied?1:0;
+    message.unread = flags.unread?1:0;
+    message.forwarded = flags.forwarded?1:0;
+    message.flagged = flags.flagged?1:0;
+    message.has_children = flags.has_children?1:0;
+    message.depth = depth;
     
     var row = document.createElement('TR');
     row.id = 'rcmrow'+uid;
@@ -3536,10 +3562,17 @@
     else if(flags.unread && this.env.unreadicon)
       icon = this.env.unreadicon;
     
-    var col = document.createElement('TD');
-    col.className = 'icon';
-    col.innerHTML = icon ? '<img src="'+icon+'" alt="" />' : '';
-    row.appendChild(col);
+    var tree = '';
+    if (depth > 0)
+      {
+      for (var i=1;i<depth;i++)
+        tree += '<div class="branch">&nbsp</div>';
+      tree += flags.has_children?'<div id="rcmexpando' + uid + '" class="' + (message.expanded?'expanded':'collapsed') + '">&nbsp;</div>':'<div class="leaf">&nbsp;</div>';
+      if (depth > 1)
+        row.style.display = 'none';
+      }
+    
+    tree += icon ? '<img src="'+icon+'" alt="" />' : '';
 
     // add each submitted col
     for (var n = 0; n < this.coltypes.length; n++) 
@@ -3548,17 +3581,21 @@
       col = document.createElement('TD');
       col.className = String(c).toLowerCase();
       
+      var html;
       if (c=='flag')
         {
         if (flags.flagged && this.env.flaggedicon)
-          col.innerHTML = '<img src="'+this.env.flaggedicon+'" alt="" />';
+          html = '<img src="'+this.env.flaggedicon+'" alt="" />';
         else if(!flags.flagged && this.env.unflaggedicon)
-          col.innerHTML = '<img src="'+this.env.unflaggedicon+'" alt="" />';
+          html = '<img src="'+this.env.unflaggedicon+'" alt="" />';
       }
       else if (c=='attachment')
-        col.innerHTML = attachment && this.env.attachmenticon ? '<img src="'+this.env.attachmenticon+'" alt="" />' : '&nbsp;';
+        html = attachment && this.env.attachmenticon ? '<img src="'+this.env.attachmenticon+'" alt="" />' : '&nbsp;';
       else
-        col.innerHTML = cols[c];
+        html = cols[c];
+	  if (n == 0)
+	    html = tree + html;
+      col.innerHTML = html;
 
       row.appendChild(col);
       }
@@ -3574,6 +3611,12 @@
       }
     };
 
+  // expand any threads that were open
+  this.expand_threads = function()
+    {
+	this.message_list.expand(null);
+    }
+
   // replace content of row count display
   this.set_rowcount = function(text)
     {
Index: roundcubemail/program/steps/mail/func.inc
===================================================================
--- roundcubemail/program/steps/mail/func.inc	(revision 2306)
+++ roundcubemail/program/steps/mail/func.inc	(working copy)
@@ -152,7 +152,6 @@
   
   // add col definition
   $out .= '<colgroup>';
-  $out .= '<col class="icon" />';
 
   foreach ($a_show_cols as $col)
     $out .= ($col!='attachment') ? sprintf('<col class="%s" />', $col) : '<col class="icon" />';
@@ -160,7 +159,7 @@
   $out .= "</colgroup>\n";
 
   // add table title
-  $out .= "<thead><tr>\n<td class=\"icon\">&nbsp;</td>\n";
+  $out .= "<thead><tr>\n";
 
   $javascript = '';
   foreach ($a_show_cols as $col)
@@ -257,6 +256,9 @@
       $js_row_arr['forwarded'] = true;
     if ($header->flagged)
       $js_row_arr['flagged'] = true;
+    if ($header->has_children)
+      $js_row_arr['has_children'] = true;
+    $js_row_arr['depth'] = $header->depth;
 
     // set message icon  
     if ($attrib['deletedicon'] && $header->deleted)
@@ -284,19 +286,28 @@
     if ($attrib['attachmenticon'] && preg_match("/multipart\/m/i", $header->ctype))
       $attach_icon = $attrib['attachmenticon'];
         
-    $out .= sprintf('<tr id="rcmrow%d" class="message%s%s%s%s">'."\n",
+    $out .= sprintf('<tr id="rcmrow%d" class="message%s%s%s%s"%s>'."\n",
                     $header->uid,
                     $header->seen ? '' : ' unread',
                     $header->deleted ? ' deleted' : '',
                     $header->flagged ? ' flagged' : '',
-                    $zebra_class);
+                    $zebra_class,
+                    ($header->depth  > 1) ? ' style="display: none"' : '');
     
-    $out .= sprintf("<td class=\"icon\">%s</td>\n", $message_icon ? sprintf($image_tag, $skin_path, $message_icon, '') : '');
+    $tree = '';
+    $depth = $header->depth;
+    if ($depth > 0)
+      {
+      for ($i=1;$i<$depth;$i++)
+        $tree .= '<div class="branch">&nbsp</div>';
+      $tree .= $header->has_children?'<div id="rcmexpando' . $header->uid . '" class="collapsed">&nbsp;</div>':'<div class="leaf">&nbsp;</div>';
+      }
+    $tree .= $message_icon ? sprintf($image_tag, $skin_path, $message_icon, '') : '';
 
-
     $IMAP->set_charset(!empty($header->charset) ? $header->charset : $CONFIG['default_charset']);
   
     // format each col
+    $first = true;
     foreach ($a_show_cols as $col)
       {
       if ($col=='from' || $col=='to')
@@ -318,6 +329,10 @@
       else
         $cont = Q($header->$col);
         
+      if ($first) {
+      	$first = false;
+      	$cont = $tree . $cont;
+      }
       if ($col!='attachment')
         $out .= '<td class="'.$col.'">' . $cont . "</td>\n";
       else
@@ -393,6 +408,12 @@
 
   $OUTPUT->command('set_message_coltypes', $a_show_cols);
 
+  // remove 'attachment' and 'flag' columns, we don't need them here
+  if(($key = array_search('attachment', $a_show_cols)) !== FALSE)
+    unset($a_show_cols[$key]);
+  if(($key = array_search('flag', $a_show_cols)) !== FALSE)
+    unset($a_show_cols[$key]);
+
   // loop through message headers
   foreach ($a_headers as $n => $header)
     {
@@ -404,12 +425,6 @@
 
     $IMAP->set_charset(!empty($header->charset) ? $header->charset : $CONFIG['default_charset']);
 
-    // remove 'attachment' and 'flag' columns, we don't need them here
-    if(($key = array_search('attachment', $a_show_cols)) !== FALSE)
-      unset($a_show_cols[$key]);
-    if(($key = array_search('flag', $a_show_cols)) !== FALSE)
-      unset($a_show_cols[$key]);
-
     // format each col; similar as in rcmail_message_list()
     foreach ($a_show_cols as $col)
       {
@@ -438,6 +453,8 @@
     $a_msg_flags['replied'] = $header->answered ? 1 : 0;
     $a_msg_flags['forwarded'] = $header->forwarded ? 1 : 0;
     $a_msg_flags['flagged'] = $header->flagged ? 1 : 0;
+    $a_msg_flags['has_children'] = $header->has_children ? 1 : 0;
+    $a_msg_cols['depth'] = $header->depth;
     
     $OUTPUT->command('add_message_row',
       $header->uid,
@@ -446,6 +463,7 @@
       preg_match("/multipart\/m/i", $header->ctype),
       $insert_top);
     }
+  $OUTPUT->command('expand_threads');
   }