--- rat/lonwrapper.pm	2016/10/31 19:49:05	1.53
+++ rat/lonwrapper.pm	2022/10/27 21:35:30	1.80
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Wrapper for external and binary files as standalone resources
 #
-# $Id: lonwrapper.pm,v 1.53 2016/10/31 19:49:05 raeburn Exp $
+# $Id: lonwrapper.pm,v 1.80 2022/10/27 21:35:30 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -38,11 +38,16 @@ use Apache::loncommon();
 use Apache::lonhtmlcommon();
 use Apache::lonextresedit();
 use Apache::lonexttool();
-use LONCAPA qw(:DEFAULT :match);;
+use Apache::lonhomework();
+use Apache::lonnavmaps();
+use LONCAPA qw(:DEFAULT :match);
+use HTML::Entities();
+use Digest::MD5();
 
 # ================================================================ Main Handler
 sub wrapper {
-    my ($url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,$title) = @_;
+    my ($r,$url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,$linktext,$explanation,
+        $title,$width,$height,$reuse,$is_supp) = @_;
 
     my $forcereg;
     unless ($env{'form.folderpath'}) {
@@ -53,7 +58,10 @@ sub wrapper {
                                           'show' => 'Show content in pop-up window',
                                         );
 
-    my $anchor;
+    (undef,undef,undef,undef,undef,undef,my $clientmobile) =
+        &Apache::loncommon::decode_user_agent($r);
+
+    my ($anchor,$uselink);
     if ($is_ext) {
         if ($env{'form.symb'}) {
             (undef,undef,my $res) = &Apache::lonnet::decode_symb($env{'form.symb'});
@@ -63,6 +71,15 @@ sub wrapper {
         } elsif ($env{'form.anchor'} ne '') {
             $anchor = '#'.$env{'form.anchor'};
         }
+        if (($is_ext eq 'tab') || ($is_ext eq 'window')) {
+            $uselink = 1;
+        }
+        unless (($is_pdf && $clientmobile) || $uselink) {
+            my $hostname = $r->hostname();
+            my $lonhost = $r->dir_config('lonHostID');
+            my $ip = &Apache::lonnet::get_host_ip($lonhost);
+            $uselink = &Apache::loncommon::is_nonframeable($url,$absolute,$hostname,$ip);
+        }
     }
 
     my $noiframe = &Apache::loncommon::modal_link($url.$anchor,$lt{'show'},500,400);
@@ -74,48 +91,225 @@ sub wrapper {
         $args->{'bread_crumbs'} = $brcrum;
     }
     if ($absolute) {
-        $args->{'use_absolute'} = $absolute; 
+        $args->{'use_absolute'} = $absolute;
+    }
+    if ($env{'form.only_body'}) {
+        $args->{'only_body'} = $env{'form.only_body'};
+    }
+
+    my ($countdown,$donemsg,$headjs);
+    if (($exttool) && (&Apache::lonnet::EXT('resource.0.gradable') =~ /^yes$/i)) {
+        $Apache::lonhomework::browse = &Apache::lonnet::allowed('bre',$url);
+        if ($env{'form.markaccess'}) {
+            my $symb=&Apache::lonnet::symbread($url);
+            my @interval=&Apache::lonnet::EXT('resource.0.interval',$symb);
+            my ($timelimit) = split(/_/,$interval[0]);
+            my $setres = &Apache::lonnet::set_first_access($interval[1],$timelimit);
+            if ($setres eq 'ok') {
+                delete($env{'form.markaccess'});
+            }
+        } elsif ($env{'form.LC_interval_done'} eq 'true') {
+            my $symb=&Apache::lonnet::symbread($url);
+            if ($symb) {
+                (my $donebuttonresult,$donemsg) = &Apache::lonhomework::zero_timer($symb);
+                undef($env{'form.LC_interval_done'});
+                undef($env{'form.LC_interval_done_proctorpass'});
+            }
+        }
+        my ($status,$result,$resource_due) =
+            &Apache::lonexttool::gradabletool_access_check();
+        undef($Apache::lonhomework::browse);
+        if ($status eq 'CAN_ANSWER') {
+            if ($resource_due) {
+                my $time_left = $resource_due - time();
+                if ($resource_due && ($time_left > 0)) {
+                    $countdown ='
+<script type="text/javascript">
+// <![CDATA['."\n".
+                             &Apache::lonhtmlcommon::countdown().'
+// ]]>
+</script>'."\n".
+                    &Apache::lonhtmlcommon::set_due_date($resource_due);
+                }
+            }
+        } else {
+            if ($status eq 'SHOW_ANSWER') {
+                $result = &Apache::lonexttool::display_score().
+                          &Apache::lonfeedback::list_discussion('tool','OPEN');
+            }
+            return &Apache::loncommon::start_page('Menu',undef,$args).
+                   $result.
+                   &Apache::loncommon::end_page();
+        }
+    }
+
+#
+# Where iframe is in use, if window.onload() executes before the custom resize function
+# has been defined (jQuery), two global javascript vars (LCnotready and LCresizedef)
+# are used to ensure document.ready() triggers a call to resize, so the iframe contents
+# do not obscure the Functions menu.
+#
+
+    unless ($clientmobile || ($exttool eq 'window') || ($exttool eq 'tab') || $uselink) {
+        $headjs = '
+<script type="text/javascript">
+// <![CDATA[
+var LCnotready = 0;
+var LCresizedef = 0;
+// ]]>
+</script>'."\n";
     }
 
-    my $startpage = &Apache::loncommon::start_page('Menu',undef,$args);
+    my $startpage = &Apache::loncommon::start_page('Menu',$headjs,$args).$countdown.$donemsg;
     my $endpage = &Apache::loncommon::end_page();
-    
-    if (($env{'browser.mobile'}) || ($exttool eq 'window')) {
+
+    if (($uselink) && ($title eq '')) {
+        if ($env{'form.symb'}) {
+            $title=&Apache::lonnet::gettitle($env{'form.symb'});
+        } elsif (!$is_supp) {
+            my $symb=&Apache::lonnet::symbread($r->uri);
+            if ($symb) {
+                $title=&Apache::lonnet::gettitle($symb);
+            }
+        }
+    }
+    if ($clientmobile || ($exttool eq 'window') || ($exttool eq 'tab') ||
+        ($is_ext eq 'tab') || ($is_ext eq 'window')) {
         my $output = $startpage;
         if ($is_pdf) {
-            if ($title eq '') {
-                $title = $env{'form.title'};
-                if ($title eq '') {
-                    unless ($env{'request.enc'}) {
-                        ($title) = ($url =~ m{/([^/]+)$});
-                        $title =~ s/(\?[^\?]+)$//;
+            $linktext = &mt('Link to PDF (for mobile devices)');
+            $output .= &create_link($url,$anchor,$title,$linktext);
+        } elsif (($exttool eq 'window') || ($exttool eq 'tab') ||
+                 ($is_ext eq 'tab') || ($is_ext eq 'window')) {
+            my $preamble;
+            if ($linktext eq '') {
+                if ($exttool) {
+                    $linktext = &mt('Launch External Tool');
+                } else {
+                    $linktext = &mt('Link to External Resource');
+                }
+            }
+            if ($exttool) {
+                $url = &HTML::Entities::encode($url,'"<>&');
+            } else {
+                $url = &HTML::Entities::encode($url.$anchor,'&<>"');
+            }
+            if (($exttool eq 'tab') || ($is_ext eq 'tab')) {
+                my $target;
+                if ($exttool) {
+                    $target = 'LCExternalToolTab';
+                } else {
+                    if ($reuse) {
+                        $target = 'LCExternalResTab';
+                    } else {
+                        $target = '_blank';
+                    }
+                    if ($title ne '') {
+                        $preamble = '<span style="font-weight:bold;">'.$title.'</span><br />';
                     }
                 }
+                $output .= '<div>'.$preamble.
+                           '<a href="'.$url.'" target="'.$target.'" style="padding:0;clear:both;margin:0;border:0">'.
+                           $linktext.'</a>'.
+                           '</div>';
+            } else {
+                my ($target,$extlinkimg);
+                if ($exttool) {
+                    $target = 'LCExternalToolPopUp';
+                } else {
+                    $target = 'LCExternalResPopUp';
+                    if ($title ne '') {
+                        $preamble = '<span style="font-weight:bold;">'.$title.'</span><br />';
+                    }
+                    $extlinkimg = '<img src="'.&Apache::loncommon::lonhttpdurl($r->dir_config('lonIconsURL').'/externallink.gif').'" width="19" height="18" border="0" />';
+                    unless ($reuse) {
+                        my $resid;
+                        if ($env{'request.course.id'}) {
+                            unless (($is_supp) || ($env{'form.folderpath'} =~ /^supplemental/)) {
+                                my $symb=&Apache::lonnet::symbread($r->uri);
+                                if ($symb) {
+                                    my $navmap = Apache::lonnavmaps::navmap->new();
+                                    if (ref($navmap)) {
+                                        my $res = $navmap->getBySymb($symb);
+                                        if (ref($res)) {
+                                            $resid = $res->id;
+                                            $resid =~ s/\./_/g;
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                        if ($resid eq '') {
+                            $resid = substr(Digest::MD5::md5_hex(Digest::MD5::md5_hex(time(). {}. rand(). $$)), 0, 8);
+                        }
+                        &js_escape(\$resid);
+                        $target .= $resid;
+                    }
+                }
+                $output .= <<"ENDLINK";
+<script type="text/javascript">
+// <![CDATA[
+var windowObjectReference = null;
+var PreviousUrl;
+
+function openSinglePopup(strUrl) {
+    if (windowObjectReference == null || windowObjectReference.closed) {
+        windowObjectReference = window.open(strUrl, "$target",
+                                            "height=$height,width=$width,scrollbars=yes,resizable=yes,status=yes,menubar=no,location=no'");
+    } else if(PreviousUrl != strUrl) {
+        windowObjectReference = window.open(strUrl, "$target",
+                                            "height=$height,width=$width,scrollbars=yes,resizable=yes,status=yes,menubar=no,location=no'");
+        windowObjectReference.focus();
+    } else {
+        windowObjectReference.focus();
+    };
+    PreviousUrl = strUrl;
+}
+// ]]>
+</script>
+<div>$preamble
+<a href="$url" target="$target" onclick="openSinglePopup(this.href); return false;">
+$linktext$extlinkimg</a>
+</div>
+ENDLINK
             }
-            unless ($title eq '') {
-                $output .= $title.'<br />';
+            if ($exttool) {
+                if ($explanation ne '') {
+                    $output .= '<div>'.$explanation.'</div>';
+                }
+                if (&Apache::lonnet::EXT('resource.0.gradable')) {
+                    $output .= &Apache::lonfeedback::list_discussion('tool','OPEN');
+                }
             }
-            $output .= '<a href="'.$url.'">'.&mt('Link to PDF (for mobile devices)').'</a>';
-        } elsif ($exttool eq 'window') {
-            $output .= '<div>'.
-                       '<a href="'.$url.'" target="LC_LTI" style="padding:0;clear:both;margin:0;border:0">'.
-                       &mt('Launch External Tool').'</a>'.
-                       '</div>';
         } else {
-            $output .= '<div style="overflow:scroll; -webkit-overflow-scrolling:touch;">'."\n".
-                       '<iframe src="'.$url.$anchor.'" height="100%" width="100%" frameborder="0">'."\n".
-                       "$lt{'noif'} $noiframe\n".
-                       "</iframe>\n".
-                       "</div>\n";
+            if ($uselink) {
+                $linktext = &mt('Link to resource');
+                $output .= &create_link($url,$anchor,$title,$linktext);
+            } else {
+                my $dest = &HTML::Entities::encode($url.$anchor,'&<>"');
+                $output .= '<div style="overflow:scroll; -webkit-overflow-scrolling:touch;">'."\n".
+                           '<iframe src="'.$dest.'" height="100%" width="100%" frameborder="0">'."\n".
+                           "$lt{'noif'} $noiframe\n".
+                           "</iframe>\n".
+                           "</div>\n";
+            }
         }
         $output .= $endpage;
         return $output;
+    } elsif ($uselink) {
+        $linktext = &mt('Link to resource');
+        return $startpage.&create_link($url,$anchor,$title,$linktext).$endpage;
     } else {
+        my $offset = 5;
+        &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},['inhibitmenu']);
+        if ($env{'form.inhibitmenu'} eq 'yes') {
+            $offset = 0;
+        }
         my $script = &Apache::lonhtmlcommon::scripttag(<<SCRIPT);
         \$(document).ready( function() {
             \$(window).unbind('resize').resize(function(){
-                var header;
-                var offset = 5;
+                var header = null;
+                var offset = $offset;
                 var height = 0;
                 var hdrtop = 0;
                 if (\$('div.LC_head_subbox:first').length) {
@@ -126,28 +320,61 @@ sub wrapper {
                         header = \$('#LC_breadcrumbs');
                     }
                 }
-                if (header.length) {
+                if (header != null && header.length) {
                     height = header.height();
                     hdrtop = header.position().top;
                 }
                 var pos = height + hdrtop + offset;
                 \$('.LC_iframecontainer').css('top', pos);
             });
+            LCresizedef = 1;
+            if (LCnotready == 1) {
+                LCnotready = 0;
+                \$(window).trigger('resize');
+            }
         });
-        window.onload = function(){  \$(window).trigger('resize') };
+        window.onload = function(){
+             if (LCresizedef) {
+                 LCnotready = 0;
+                 \$(window).trigger('resize');
+             } else {
+                 LCnotready = 1;
+             }
+        };
 SCRIPT
         # javascript will position the iframe if window was resized (or zoomed)
+        my $dest = &HTML::Entities::encode($url.$anchor,'&<>"');
         return <<ENDFRAME;
         $startpage
         $script
         <div class="LC_iframecontainer">
-            <iframe src="$url$anchor">$lt{'noif'} $noiframe</iframe>
+            <iframe src="$dest">$lt{'noif'} $noiframe</iframe>
         </div>
         $endpage
 ENDFRAME
     }
 }
 
+sub create_link {
+    my ($url,$anchor,$title,$linktext) = @_;
+    my $shownlink;
+    if ($title eq '') {
+        $title = $env{'form.title'};
+        if ($title eq '') {
+            unless ($env{'request.enc'}) {
+                ($title) = ($url =~ m{/([^/]+)$});
+                $title =~ s/(\?[^\?]+)$//;
+            }
+        }
+    }
+    unless ($title eq '') {
+        $shownlink = '<span style="font-weight:bold;">'.$title.'</span><br />';
+    }
+    my $dest = &HTML::Entities::encode($url.$anchor,'&<>"');
+    $shownlink .= '<a href="'.$dest.'">'.$linktext.'</a>';
+    return $shownlink;
+}
+
 sub handler {
     my $r=shift;
     &Apache::loncommon::content_type($r,'text/html');
@@ -156,26 +383,65 @@ sub handler {
     return OK if $r->header_only;
 
     my $url = $r->uri;
-    my ($is_ext,$brcrum,$absolute,$is_pdf,$exttool,$cdom,$cnum);
+    my ($is_ext,$brcrum,$absolute,$is_pdf,$exttool,$cdom,$cnum,$hostname,
+        $linktext,$explanation,$width,$height,$reuse,$is_supp);
 
     for ($url){
         s|^/adm/wrapper||;
-        $is_ext = $_ =~ s|^/ext/|http://|;         
-        s|http://https://|https://|;
-        s|&colon;|:|g;              
+        $is_ext = $_ =~ s|^/ext/|http://|;
+        s|http://https://|https://| if ($is_ext);
+        s|&colon;|:|g;
     }
 
-
     if ($url =~ /\.pdf$/i) {
         $is_pdf = 1;
-    } elsif ($url =~ m{^/adm/($match_domain)/($match_courseid)/(\d+)/exttools?$}) {
+    } elsif (($is_ext) && ($env{'request.course.id'})) {
+        if ($env{'course.'.$env{'request.course.id'}.'.extresource'}) {
+            (my $selected,$reuse,$width,$height) = split(/:/,$env{'course.'.$env{'request.course.id'}.'.extresource'});
+            if ($selected eq 'tab') {
+                $is_ext = 'tab';
+                $width = '';
+                $height = '';
+            } elsif ($selected eq 'window') {
+                $is_ext = 'window';
+                unless ($width =~ /^\d+$/) {
+                    $width = '';
+                }
+                unless ($height =~ /^\d+$/) {
+                    $height = '';
+                }
+            } else {
+                $width = '';
+                $height = '';
+                $reuse = '';
+            }
+        }
+    } elsif ($url =~ m{^/adm/($match_domain)/($match_courseid)/(\d+)/ext\.tool$}) {
         $cdom = $1;
         $cnum = $2;
         my $marker = $3;
         $exttool = 'iframe';
-        my %toolhash = &Apache::lonnet::get('exttool_'.$marker,['target'],$cdom,$cnum);
+        my $exttoolremote;
+        my %toolhash = &Apache::lonnet::get('exttool_'.$marker,['target','linktext','explanation','id','width','height'],
+                                            $cdom,$cnum);
+        if ($toolhash{'id'}) {
+            my %ltitools = &Apache::lonnet::get_domain_lti($cdom,'consumer');
+            if (ref($ltitools{$toolhash{'id'}}) eq 'HASH') {
+                $exttoolremote = $ltitools{$toolhash{'id'}}{'url'};
+            }
+        }
         if ($toolhash{'target'} eq 'window') {
-           $exttool = 'window'; 
+            $exttool = 'window';
+            $width = $toolhash{'width'};
+            $height = $toolhash{'height'};
+        } elsif ($toolhash{'target'} eq 'tab') {
+            $exttool = 'tab';
+        }
+        if (($exttool eq 'window') || ($exttool eq 'tab')) {
+            $linktext = $toolhash{'linktext'};
+            $explanation = $toolhash{'explanation'};
+        } elsif (($exttoolremote =~ /^http:/) && ($ENV{'SERVER_PORT'} == 443)) {
+            $exttool = 'tab';
         }
     }
     if (($is_ext) || ($exttool)) {
@@ -194,18 +460,19 @@ sub handler {
                 if ($env{'form.anchor'} ne '') {
                     $url .= '#'.$env{'form.anchor'};
                 }
+                $is_supp = 1;
             }
             my $type = 'ext';
-            my %ltitools;
             if ($exttool) {
                 $type = 'tool';
-                %ltitools = &Apache::lonnet::get_domain_ltitools($cdom);
+            } elsif (($url =~ /^http:/) && ($ENV{'SERVER_PORT'} == 443)) {
+                $hostname = $r->hostname();
             }
             $r->print(
                 &Apache::lonextresedit::display_editor($url,$env{'form.folderpath'},
                                                        $env{'form.symb'},
                                                        $env{'form.idx'},$type,$cdom,
-                                                       $cnum,\%ltitools));
+                                                       $cnum,$hostname));
             return OK;
         } elsif ($env{'form.folderpath'} =~ /^supplemental/) {
             my $crstype = &Apache::loncommon::course_type();
@@ -217,15 +484,39 @@ sub handler {
                     $title = &mt('External Tool');
                 }
             }
+            $is_supp = 1;
+            if ($env{'request.course.id'}) {
+                $cnum = $env{'course.'.$env{'request.course.id'}.'.num'};
+                $cdom = $env{'course.'.$env{'request.course.id'}.'.domain'};
+                &Apache::loncommon::validate_folderpath(1,'',$cnum,$cdom);
+            }
+            $brcrum =
+                &Apache::lonhtmlcommon::docs_breadcrumbs(undef,$crstype,undef,$title,1);
+        }
+    } elsif ($env{'request.course.id'}) {
+        my $courseurl = &Apache::lonnet::courseid_to_courseurl($env{'request.course.id'});
+        $courseurl =~ s{^/}{};
+        if ($url =~ m{^\Q/uploaded/$courseurl/supplemental/\E}) {
+            $is_supp = 1;
+            &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},
+                                                    ['folderpath','title']);
+            if ($env{'form.folderpath'}) {
+                $cnum = $env{'course.'.$env{'request.course.id'}.'.num'};
+                $cdom = $env{'course.'.$env{'request.course.id'}.'.domain'};
+                &Apache::loncommon::validate_folderpath(1,'',$cnum,$cdom);
+            }
+            my $title = $env{'form.title'};
+            my $crstype = &Apache::loncommon::course_type();
             $brcrum =
                 &Apache::lonhtmlcommon::docs_breadcrumbs(undef,$crstype,undef,$title,1);
+
         }
     }
 
 #
 # Actual URL
 #
-    if ($url=~/$LONCAPA::assess_re/) {
+    if (($url=~/$LONCAPA::assess_re/) && (!$exttool)) {
 #
 # This is uploaded homework
 #
@@ -246,11 +537,13 @@ sub handler {
         }
 
         # encrypt url if not external
-        unless ($is_ext || $exttool) {
+        unless ($is_ext) {
             &Apache::lonenc::check_encrypt(\$url);
         }
 
-        $r->print( wrapper($url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool) );
+        $r->print( wrapper($r,$url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,
+                           $linktext,$explanation,undef,$width,$height,$reuse,
+                           $is_supp) );
 
     } # not just the menu
     
@@ -277,14 +570,21 @@ described at http://www.lon-capa.org.
 
 =over
 
-=item wrapper($url,$brcrum,$absolute,$is_ext,$is_pdf,$title))
+=item wrapper($r,$url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,$linktext,$explanation,$title,$width,$height,$reuse,$is_supp)
 
 =over
 
+=item $r
+
+request object
+
 =item $url
 
-url to display by including in an iframe within a
-LON-CAPA page which has a standard LON-CAPA inline menu.
+url to display either by including in an iframe within a
+LON-CAPA page which has a standard LON-CAPA inline menu,
+or in some cases launched in a separate tab or window,
+launched via a link in a LON-CAPA page with standard inline
+menu.
 
 =item $brcrum
 
@@ -313,26 +613,89 @@ in Firefox 23 and later, when serving fr
 
 =item $is_ext
 
-true if URL is for an external resource.
+true if URL is for an external resource. Default true value
+is 1 (display in iframe, unless $uselink is true).
+If external resource is to be displayed in a tab,
+value of $is_ext will be tab, if to be displayed in a pop-up window,
+value of $is_ext will be window.
 
 =item $is_pdf
 
 true if URL is for a PDF (based on file extension).
 
+=item $exttool
+
+If URL is for an External Tool, will contain the target type: iframe, window or tab.
+
+=item $linktext
+
+optional. If URL is for an External Tool, and target type is window or tab,
+then the link text may be an option set in the course for each tool instance,
+or may be a default defined in the domain for all instances of the tool.
+
+=item $explanation
+
+optional. If URL is for an External Tool, and target type is window or tab,
+then the explanation is an option set in the course for each tool instance,
+or may be a default defined in the domain for all instances of the tool.
+
 =item $title
 
-optional. If wrapped item is a PDF, and $env{'browser.mobile'} 
-is true, a link to a PDF is shown. The "title" will be displayed
+optional. If wrapped item is a PDF, and $clientmobile is true,
+a link to a PDF is shown. The "title" will be displayed
 above the link, but if not provided as an arg, $env{'form.title'}
 will be used, otherwise, the filename will be displayed (unless
 hidden URL set for the resource).
 
+=item $width
+
+optional. If URL is for an External Tool, and target type is window,
+then a default width may have been defined in the domain for all instances of
+the tool.  If so, that width will be used for the window opened (via a link)
+to launch the external tool. If the URL is for an External Resource, and
+$is_ext is window, then a default width (px) may have been defined in the current
+course for all external resource instances.
+
+=item $height
+
+optional. If URL is for an External Tool, and target type is window,
+then a default height may have been defined in the domain for all instances of
+the tool.  If so, that height will be used for the window opened (via a link)
+to launch the external tool.  If the URL is for an External Resource, and
+$is_ext is window, then a default height (px) may have been defined in the current
+course for all external resource instances.
+
+=item $reuse
+
+optional. If the URL is for an External Resource, and $is_ext is tab or window,
+then $reuse will be true if the same tab or window is to be reused for display
+of all external resource instances in a a course.
+
 =back
 
 Returns markup for the entire page.
 
 =item handler()
 
+Content handler for requests for: /adm/wrapper/...
+used for content to be displayed in an iframe, or launched in a separate tab
+or window via a link.  The target URL is extracted from the requested URL, by
+removing the /adm/wrapper prefix.
+
+The target URL will typically be a PDF served from the current server, an
+external resource URL served from a different server, or an external tool
+(from an LTI Provider) launched from LON-CAPA (as LTI Consumer) and launched
+via a link.
+
+If the request included forceedit in the query string, and the requester has
+rights to modify course content, then the editor will be displayed to allow
+changes to be made to the resource (e.g., change the URL of the external resource,
+or change the setting for the external tool instance).
+
+If not in edit mode, then the wrapper() subroutine will be called to generate the
+standard LON-CAPA inline menu, and then either a link to launch a separate tab or
+window, or an iframe to display the content inline.
+
 =back
 
 =cut