Index: openacs-4/packages/xowf/lib/inclass-exam-answer.wf
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xowf/lib/Attic/inclass-exam-answer.wf,v
diff -u -r1.1.2.39 -r1.1.2.40
--- openacs-4/packages/xowf/lib/inclass-exam-answer.wf	2 May 2021 11:06:57 -0000	1.1.2.39
+++ openacs-4/packages/xowf/lib/inclass-exam-answer.wf	25 May 2021 20:08:20 -0000	1.1.2.40
@@ -227,23 +227,27 @@
     return [done_form_loader $ctx $form_name]
   }
 
-  set item_nr [$obj property position]
+  set item_nr [:current_position $obj]
+  #:msg "working_form_loader item_nr $item_nr [$obj instance_attributes]"
 
   set parent_id [$obj parent_id]
-  #:msg "working_form_loader item_nr $item_nr [$obj instance_attributes]"
   set parent_obj [::xo::db::CrClass get_instance_from_db -item_id $parent_id]
 
   #
   # In case shuffling is required, fetch via the shuffled position.
   #
+  #:msg "============ working_form_loader load form on pos $position"
+
   set shuffle_id [expr {[$parent_obj property shuffle_items 0] ? [$obj creation_user] : -1}]
   set position [${:QM} shuffled_index -shuffle_id $shuffle_id $parent_obj $item_nr]
-  #:msg "============ working_form_loader load form on pos $position"
+  #ns_log notice "============ working_form_loader: position based on item_nr $item_nr and shuffle $shuffle_id -> $position"
 
   #
   # Load the form.
   #
   set form_obj [${:QM} nth_question_obj $parent_obj $position]
+  #ns_log notice "load form => $form_obj (position $position [$form_obj name])"
+
   #
   # Substitute markup in the constant part of the form in the context
   # of the original form object, setting the resolve context in the
@@ -257,6 +261,13 @@
   $form_obj set_property form [dict get $d form]
 
   #
+  # Add __current_item_nr as hidden form field to detect and handle
+  # cases, where actual form-data divergates from data in the
+  # database.
+  #
+  $obj proc extra_html_fields {} [list ::html::input -type hidden -name __current_item_nr -value $item_nr]
+
+  #
   # Update IP address each time the form is loaded.
   #
   if {[$obj state] in {"initial" "working"}} {
@@ -268,13 +279,20 @@
   #
   :set_title $obj -position $position -item_nr $item_nr -for_question -with_minutes
 
+  ns_log notice "============ working_form_loader: set title -position $position -item_nr $item_nr "
+
   #
   # Disallow paste if required
   #
   if {![$parent_obj property allow_paste true]} {
     ${:QM} disallow_paste $form_obj
   }
 
+  #$form_obj lappend form_constraints {__item_nr:hidden}
+
+  #ns_log notice "============ working_form_loader: [$form_obj serialize] "
+  ns_log notice "============ working_form_loader returns [$form_obj name] "
+
   return $form_obj
 }
 
@@ -343,7 +361,7 @@
   #ns_log notice "SETTING $obj title [join $title { · }]"
   $obj title [join $title " · "]
   #:msg title=[join $title " · "]
-  
+
   #:msg set_title-set_parameter-MenuBar-[$obj state]
   :plain_template -prevent_multiple_tabs $prevent_multiple_tabs $obj
 
@@ -385,7 +403,7 @@
   # active, and is the feature set in the workflow parameters?
   #
   if {$prevent_multiple_tabs && [info exists :prevent_multiple_tabs] && ${:prevent_multiple_tabs}} {
-    ns_log notice "!!! prevent multiple tabs"
+    #ns_log notice "!!! prevent multiple tabs"
     xowf::test_item::answer_manager prevent_multiple_tabs -cookie_name "tab_counter_[$obj item_id]"
   }
 }
@@ -435,6 +453,27 @@
               -form_constraints $summary_fc]
 }
 
+:proc current_position {obj} {
+  if {[$obj form_parameter __form_action ""] eq "save-form-data"} {
+    #
+    # In case there was an mutual overwrite, the position as provided
+    # by the instance attributes might deviate from the position,
+    # based on which the actual form data was generated. So, for
+    # validating and updating one has to change the position to the
+    # one from the form data (when this differs). Note, that the
+    # randomizer depends on property "position" as well.
+    #
+    set current_item_nr [$obj form_parameter __current_item_nr]
+    set position [$obj property position]
+    if {$current_item_nr ne "" && $current_item_nr ne $position} {
+      ns_log warning "working_form_loader: position provided by form differs from stored data." \
+          "Use position from form data $current_item_nr instead of $position"
+      $obj set_property position $current_item_nr
+    }
+  }
+  return [$obj property position]
+}
+
 :proc addSignature {obj} {
   set answerAttributes [xowf::test_item::renaming_form_loader \
                             answer_attributes [$obj instance_attributes]]
@@ -495,7 +534,9 @@
     # user, which is not necessarily the nth question in the list of
     # questions due to shuffling.
     #
-    set current_position [:property position]
+    set current_position0 [:property position]
+    set current_position [$container current_position [self]]
+    ns_log notice "============ object-specific old current_position $current_position0 new current_position $current_position"
     set actions {}
 
     if {${:state} ne "done"} {
@@ -570,6 +611,19 @@
     ns_return 200 text/plain OK
     ad_script_abort
   }
+
+  #
+  # Do NOT allow edits from multiple browser instances or tabs.
+  #
+  :proc mutual_overwrite_occurred {} {
+    next
+    ns_log warning "mutual_overwrite_occurred [self] ${:name}: user [::xo::cc user_id] => auto-close window"
+    template::add_body_script -script [subst {
+      alert('Not allowed to have two browser instances or tabs open!');
+      window.open("about:blank", "_self").close();
+    }]
+  }
+
 }