Index: openacs-4/packages/chat/tcl/chat-ajax-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/chat/tcl/chat-ajax-procs.tcl,v
diff -u -N -r1.26 -r1.27
--- openacs-4/packages/chat/tcl/chat-ajax-procs.tcl	20 Nov 2018 17:46:20 -0000	1.26
+++ openacs-4/packages/chat/tcl/chat-ajax-procs.tcl	21 Nov 2018 09:56:37 -0000	1.27
@@ -37,9 +37,15 @@
             return [_ chat.Room_not_found]
         } else {
             chat_room_get -room_id $chat_id -array c
-            set package_id $c(context_id)
+            next \
+                -chat_id $chat_id \
+                -package_id $c(context_id) \
+                -mode $mode \
+                -path $path \
+                -login_messages_p $c(login_messages_p) \
+                -logout_messages_p $c(logout_messages_p) \
+                -timewindow $c(messages_time_window)
         }
-        next -chat_id $chat_id -package_id $package_id -mode $mode -path $path
     }
 
     Chat instproc initialize_nsvs {} {
@@ -60,12 +66,6 @@
             ad_return_forbidden
             ad_script_abort
         }
-        if {[chat_room_exists_p ${:chat_id}]} {
-            chat_room_get -room_id ${:chat_id} -array c
-            set :login_messages_p  $c(login_messages_p)
-            set :logout_messages_p $c(logout_messages_p)
-            set :timewindow        $c(messages_time_window)
-        }
         next
     }
 
Index: openacs-4/packages/xowiki/tcl/chat-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/chat-procs.tcl,v
diff -u -N -r1.46 -r1.47
--- openacs-4/packages/xowiki/tcl/chat-procs.tcl	20 Nov 2018 18:45:56 -0000	1.46
+++ openacs-4/packages/xowiki/tcl/chat-procs.tcl	21 Nov 2018 09:56:37 -0000	1.47
@@ -403,7 +403,15 @@
     return $mode
   }
 
-  ::xo::ChatClass instproc login {-chat_id {-package_id ""} {-mode ""} {-path ""}} {
+  ::xo::ChatClass instproc login {
+    -chat_id
+    {-package_id ""}
+    {-mode ""}
+    {-path ""}
+    -login_messages_p
+    -logout_messages_p
+    -timewindow
+  } {
     #:log "--chat"
     if {![ns_conn isconnected]} return
     auth::require_login
@@ -430,8 +438,9 @@
     if {[string index $path end] ne "/"} {append path /}
     if {![info exists chat_id]} {set chat_id $package_id}
     set session_id [ad_conn session_id].[clock seconds]
-    set context id=$chat_id&s=$session_id&class=[self]
-    set base_url ${xowiki_path}chat?${context}
+    set base_url [export_vars -base ${xowiki_path}chat -no_empty {
+      {id $chat_id} {s $session_id} {class "[self]"}
+    }]
 
     # This might come in handy to get resources from the chat package
     # if we want to have e.g. a separate css.
@@ -515,11 +524,22 @@
       </div>
     }]
 
-    [self] create c1 \
-          -destroy_on_cleanup \
-          -chat_id    $chat_id \
-          -session_id $session_id \
-          -mode       $mode
+    set chat_cmd [list \
+                      [self] create c1 \
+                      -destroy_on_cleanup \
+                      -chat_id    $chat_id \
+                      -session_id $session_id \
+                      -mode       $mode]
+    # We don't want to override Chat class default with our own and
+    # therefore we build the command dynamically depending if these
+    # variables are there or not.
+    set optional_vars [list login_messages_p logout_messages_p timewindow]
+    foreach var $optional_vars {
+      if {[info exists $var]} {
+        lappend chat_cmd -${var} [set $var]
+      }
+    }
+    {*}$chat_cmd
 
     set data [c1 login]
     if {$data ne ""} {
Index: openacs-4/packages/xowiki/tcl/includelet-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowiki/tcl/includelet-procs.tcl,v
diff -u -N -r1.233 -r1.234
--- openacs-4/packages/xowiki/tcl/includelet-procs.tcl	19 Nov 2018 14:32:29 -0000	1.233
+++ openacs-4/packages/xowiki/tcl/includelet-procs.tcl	21 Nov 2018 09:56:37 -0000	1.234
@@ -4665,6 +4665,9 @@
           {-chat_id ""}
           {-mode ""}
           {-path ""}
+          -login_messages_p
+          -logout_messages_p
+          -timewindow
         }}
       }
   chat instproc render {} {
@@ -4673,7 +4676,22 @@
       # make the chat just for including page
       set chat_id [${:__including_page} item_id]
     }
-    set r [::xowiki::Chat login -chat_id $chat_id -mode $mode -path $path]
+    set chat_cmd [list \
+                      ::xowiki::Chat login \
+                      -chat_id $chat_id \
+                      -mode $mode \
+                      -path $path]
+    # We don't want to override Chat class default with our own and
+    # therefore we build the command dynamically depending if these
+    # variables are there or not.
+    set optional_vars [list login_messages_p logout_messages_p timewindow]
+    foreach var $optional_vars {
+      if {[info exists $var]} {
+        lappend chat_cmd -${var} [set $var]
+      }
+    }
+    set r [{*}$chat_cmd]
+
     #ns_log notice chat=>$r
 
     return $r