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 -r1.15 -r1.16
--- openacs-4/packages/xowiki/tcl/chat-procs.tcl	13 Sep 2012 16:05:26 -0000	1.15
+++ openacs-4/packages/xowiki/tcl/chat-procs.tcl	17 Feb 2013 11:48:06 -0000	1.16
@@ -34,37 +34,70 @@
   Chat proc initialize_nsvs {} {;}      ;# noop
 
   Chat proc login {-chat_id -package_id -mode} {
-    my log "--"
+    #my log "--chat"
     auth::require_login
     if {![info exists package_id]} {set package_id [ad_conn package_id] }
     if {![info exists chat_id]}    {set chat_id $package_id }
     set context id=$chat_id&s=[ad_conn session_id].[clock seconds]
     set path    [lindex [site_node::get_url_from_object_id -object_id $package_id] 0]
     
     if {![info exists mode]} {
+      #
+      # The parameter "mode" was not specified, we try to guess the
+      # "best" mode known to work for the currently used browser.
+      #
+      # The most conservative mode is
+      # - "polling" (which requires for every connected client polling
+      #    requests), followed by
+      # - "scripted-streaming" (which opens and "infinitely long" HTML 
+      #   files with embedded script tags; very portable, but this 
+      #   causes the loading indicator to spin), followed by
+      # - "streaming" (true streaming, but this requires 
+      #   an HTTP stack supporting partial reads).
+      #
+      # NOTICE 1: The guessing is based on current versions of the
+      # browsers. Older versions of the browser might behave
+      # differently.
+      #
+      # NOTICE 2: "streaming" (and to a lesser extend
+      # "scripted-streaming" - which used chunked encoding) might be
+      # influenced by the buffering behavior of a reverse proxy, which
+      # might have to be configured appropriately.
+      #
+      # To be independet of the guessing mode, instantiate the chat
+      # object with "mode" specified.
+      #
       set mode polling
+      #
+      # Check, whether we have the tcllibthread and a sufficiently new
+      # aolserver/naviserver supporting bgdelivery transfers.
+      #
       if {[info command ::thread::mutex] ne "" &&
           ![catch {ns_conn contentsentlength}]} {
-        # we seem to have libthread installed, and the patch for obtaining the tcl-stream
-        # from a connection thread, so we can use the background delivery thread;
+	#
         # scripted streaming should work everywhere
+	#
         set mode scripted-streaming
-        if {[regexp (firefox) [string tolower [ns_set get [ns_conn headers] User-Agent]]]} {
-          # for firefox, we could use the nice mode without the spinning load indicator
-          # currently, streaming mode seems broken with current firefox...
-          #set mode streaming
-        }
+        if {![regexp msie|opera [string tolower [ns_set get [ns_conn headers] User-Agent]]]} {
+	  # Explorer doesn't expose partial response until request state != 4, while Opera fires
+	  # onreadystateevent only once. For this reason, for every broser except them, we could 
+	  # use the nice mode without the spinning load indicator.
+	  #
+	  set mode streaming
+	}
       }
       my log "--chat mode $mode"
     }
 
+    # small javascript library to obtain a portable ajax request object
+    ::xo::Page requireJS "/resources/xowiki/get-http-object.js"
+
     switch $mode {
       polling {
-        ::xo::Page requireJS  "/resources/xowiki/get-http-object.js"
         set jspath packages/xowiki/www/ajax/chat.js
-        set login_url ${path}ajax/chat?m=login&$context
-        set get_update  "chatSendCmd(\"$path/ajax/chat?m=get_new&$context\",chatReceiver)"
-        set get_all     "chatSendCmd(\"$path/ajax/chat?m=get_all&$context\",chatReceiver)"
+        set login_url  ${path}ajax/chat?m=login&$context
+        set get_update "chatSendCmd(\"$path/ajax/chat?m=get_new&$context\",chatReceiver)"
+        set get_all    "chatSendCmd(\"$path/ajax/chat?m=get_all&$context\",chatReceiver)"
       }
       streaming {
         set jspath packages/xowiki/www/ajax/streaming-chat.js
@@ -117,7 +150,8 @@
 overflow:auto;
 '></div>
    <form action='#' onsubmit='chatSendMsg(); return false;'>
-   <input type='text' size='40' name='msg' id='chatMsg'>"
+   <input type='text' size='40' name='msg' id='chatMsg'>
+   </form>"
       }