--- loncom/interface/lonnavmaps.pm	2003/05/14 18:34:44	1.189
+++ loncom/interface/lonnavmaps.pm	2003/05/14 20:16:56	1.190
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Navigate Maps Handler
 #
-# $Id: lonnavmaps.pm,v 1.189 2003/05/14 18:34:44 bowersj2 Exp $
+# $Id: lonnavmaps.pm,v 1.190 2003/05/14 20:16:56 bowersj2 Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -737,6 +737,14 @@ returns a true or false value. If true,
 false, it is simply skipped in the display. By default, all resources
 are shown.
 
+=item * B<suppressEmptySequences>:
+
+If you're using a filter function, and displaying sequences to orient
+the user, then frequently some sequences will be empty. Setting this to
+true will cause those sequences not to display, so as not to confuse the
+user into thinking that if the sequence is there there should be things
+under it.
+
 =item * B<suppressNavmaps>:
 
 If true, will not display Navigate Content resources. Default to
@@ -1223,6 +1231,43 @@ sub render {
     $args->{'indentString'} = setDefault($args->{'indentString'}, "<img src='/adm/lonIcons/whitespace1.gif' width='25' height='1' alt='' border='0' />");
     $args->{'displayedHereMarker'} = 0;
 
+    # If we're suppressing empty sequences, look for them here. Use DFS for speed,
+    # since structure actually doesn't matter, except what map has what resources.
+    if ($args->{'suppressEmptySequences'}) {
+        my $dfsit = Apache::lonnavmaps::DFSiterator->new($navmap,
+                                                         $it->{FIRST_RESOURCE},
+                                                         $it->{FINISH_RESOURCE},
+                                                         {}, undef, 1);
+        $depth = 0;
+        $dfsit->next();
+        my $curRes = $dfsit->next();
+        while ($depth > -1) {
+            if ($curRes == $dfsit->BEGIN_MAP()) { $depth++; }
+            if ($curRes == $dfsit->END_MAP()) { $depth--; }
+
+            if (ref($curRes)) { 
+                # Parallel pre-processing: Do sequences have non-filtered-out children?
+                if ($curRes->is_sequence()) {
+                    $curRes->{DATA}->{HAS_VISIBLE_CHILDREN} = 0;
+                    # Sequences themselves do not count as visible children,
+                    # unless those sequences also have visible children.
+                    # This means if a sequence appears, there's a "promise"
+                    # that there's something under it if you open it, somewhere.
+                } else {
+                    # Not a sequence: if it's filtered, ignore it, otherwise
+                    # rise up the stack and mark the sequences as having children
+                    if (&$filterFunc($curRes)) {
+                        for my $sequence (@{$dfsit->getStack()}) {
+                            $sequence->{DATA}->{HAS_VISIBLE_CHILDREN} = 1;
+                        }
+                    }
+                }
+            }
+        } continue {
+            $curRes = $dfsit->next();
+        }
+    }
+
     my $displayedJumpMarker = 0;
     # Set up iteration.
     $depth = 1;
@@ -1266,6 +1311,12 @@ sub render {
             next;
         } 
 
+        # If this is an empty sequence and we're filtering them, continue on
+        if ($curRes->is_sequence() && $args->{'suppressEmptySequences'} &&
+            !$curRes->{DATA}->{HAS_VISIBLE_CHILDREN}) {
+            next;
+        }
+
         # If we're suppressing navmaps and this is a navmap, continue on
         if ($suppressNavmap && $curRes->src() =~ /^\/adm\/navmaps/) {
             next;
@@ -2194,7 +2245,8 @@ sub new {
                 
                 $curRes->{DATA}->{DISPLAY_DEPTH} = $finalDepth;
                 if ($finalDepth > $maxDepth) {$maxDepth = $finalDepth;}
-                }
+            }
+        } continue {
             $curRes = $iterator->next();
         }
     }
@@ -2571,6 +2623,31 @@ sub next {
     return $self->{HERE};
 }
 
+# Identical to the full iterator methods of the same name. Hate to copy/paste
+# but I also hate to "inherit" either iterator from the other.
+
+sub getStack {
+    my $self=shift;
+
+    my @stack;
+
+    $self->populateStack(\@stack);
+
+    return \@stack;
+}
+
+# Private method: Calls the iterators recursively to populate the stack.
+sub populateStack {
+    my $self=shift;
+    my $stack = shift;
+
+    push @$stack, $self->{HERE} if ($self->{HERE});
+
+    if ($self->{RECURSIVE_ITERATOR_FLAG}) {
+        $self->{RECURSIVE_ITERATOR}->populateStack($stack);
+    }
+}
+
 1;
 
 package Apache::lonnavmaps::resource;