--- rat/lonwrapper.pm	2013/10/15 10:17:19	1.45
+++ rat/lonwrapper.pm	2023/01/21 23:25:16	1.49.2.11.2.3
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Wrapper for external and binary files as standalone resources
 #
-# $Id: lonwrapper.pm,v 1.45 2013/10/15 10:17:19 raeburn Exp $
+# $Id: lonwrapper.pm,v 1.49.2.11.2.3 2023/01/21 23:25:16 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -37,16 +37,52 @@ use Apache::lonlocal;
 use Apache::loncommon();
 use Apache::lonhtmlcommon();
 use Apache::lonextresedit();
+use Apache::lonexttool();
+use Apache::lonnavmaps();
+use LONCAPA qw(:DEFAULT :match);
+use HTML::Entities();
+use Digest::MD5();
 
 # ================================================================ Main Handler
 sub wrapper {
-    my ($url,$brcrum,$absolute,$is_ext) = @_;
+    my ($r,$url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,$linktext,$explanation,
+        $title,$width,$height,$reuse,$is_supp) = @_;
 
     my $forcereg;
     unless ($env{'form.folderpath'}) {
         $forcereg = 1;
     }
 
+    my %lt = &Apache::lonlocal::texthash(
+                                          'noif' => 'No iframe support.',
+                                          'show' => 'Show content in pop-up window',
+                                        );
+
+    (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'});
+            if ($res =~ /(#[^#]+)$/) {
+                $anchor = $1;
+            }
+        } elsif ($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);
     my $args = {'bgcolor' => '#FFFFFF'};
     if ($forcereg) {
         $args->{'force_register'} = $forcereg;
@@ -55,47 +91,241 @@ 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 $startpage =  Apache::loncommon::start_page('Menu',undef,$args);
-    my $endpage =  Apache::loncommon::end_page();
+    my $headjs;
 
-    my $script = Apache::lonhtmlcommon::scripttag(<<SCRIPT );
-    \$(document).ready( function() {
-        \$(window).unbind('resize').resize(function(){
-            var header;
-            var offset = 5;
-            var height = 0;
-            var hdrtop = 0;
-            if (\$('div.LC_head_subbox:first').length) {
-                header = \$('div.LC_head_subbox:first');
-                offset = 9;
+#
+# Where iframe is in use, if window.onload() executes before the custom resize function
+# has been defined (jQuery), two global javascript vars (LCnotready and LCresizedef)
+# are used to ensure document.ready() triggers a call to resize, so the iframe contents
+# do not obscure the Functions menu.
+#
+
+    unless ($clientmobile || ($exttool eq 'window') || ($exttool eq 'tab') || $uselink) {
+        $headjs = '
+<script type="text/javascript">
+// <![CDATA[
+var LCnotready = 0;
+var LCresizedef = 0;
+// ]]>
+</script>'."\n";
+    }
+
+    my $startpage = &Apache::loncommon::start_page('Menu',$headjs,$args);
+    my $endpage = &Apache::loncommon::end_page();
+
+    if (($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) {
+            $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 {
-                if (\$('#LC_breadcrumbs').length) {
-                    header = \$('#LC_breadcrumbs');
+                $url = &HTML::Entities::encode($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
+            }
+            if ($exttool) {
+                if ($explanation ne '') {
+                    $output .= '<div>'.$explanation.'</div>';
                 }
             }
-            if (header.length) {
-                height = header.height();
-                hdrtop = header.position().top;
+        } else {
+            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 = null;
+                var offset = $offset;
+                var height = 0;
+                var hdrtop = 0;
+                if (\$('div.LC_head_subbox:first').length) {
+                    header = \$('div.LC_head_subbox:first');
+                    offset = 9;
+                } else {
+                    if (\$('#LC_breadcrumbs').length) {
+                        header = \$('#LC_breadcrumbs');
+                    }
+                }
+                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');
             }
-            var pos = height + hdrtop + offset;
-            \$('.LC_iframecontainer').css('top', pos);
         });
-    });
-    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)
-    return <<ENDFRAME;
-    $startpage
-    $script
-    <div class="LC_iframecontainer">
-        <iframe src="$url">No iframe support!</iframe>
-    </div>
-    $endpage
+        # javascript will position the iframe if window was resized (or zoomed)
+        my $dest = &HTML::Entities::encode($url.$anchor,'&<>"');
+        return <<ENDFRAME;
+        $startpage
+        $script
+        <div class="LC_iframecontainer">
+            <iframe src="$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 {
@@ -106,51 +336,142 @@ sub handler {
     return OK if $r->header_only;
 
     my $url = $r->uri;
-    my ($is_ext,$brcrum,$absolute);
+    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 ($is_ext) {
-        my $hostname = $r->hostname();
-        my $lonhost = &Apache::lonnet::host_from_dns($hostname);
-        if ($lonhost) {
-            my $actual = &Apache::lonnet::absolute_url($hostname);
-            my $expected = $Apache::lonnet::protocol{$lonhost}.'://'.$hostname; 
-            unless ($actual eq $expected) {
-                $absolute = $expected;
+    if ($url =~ /\.pdf$/i) {
+        $is_pdf = 1;
+    } elsif (($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 $exttoolremote;
+        my %toolhash = &Apache::lonnet::get('exttool_'.$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';
+            $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) || ($exttool)) {
         &Apache::loncommon::get_unprocessed_cgi($ENV{'QUERY_STRING'},
-            ['forceedit','register','folderpath','symb','idx','title']);
+            ['forceedit','register','folderpath','symb','idx','title','anchor']);
         if (($env{'form.forceedit'}) &&
             (&Apache::lonnet::allowed('mdc',$env{'request.course.id'})) &&
             (($env{'form.folderpath'} =~ /^supplemental/) ||
              ($env{'form.symb'} =~ /^uploaded/))) {
+            if ($env{'form.symb'}) {
+                (undef,undef,my $res) = &Apache::lonnet::decode_symb($env{'form.symb'});
+                if ($res =~ /(#[^#]+)$/) {
+                    $url .= $1;
+                }
+            } elsif ($env{'form.folderpath'} =~ /^supplemental/) {
+                if ($env{'form.anchor'} ne '') {
+                    $url .= '#'.$env{'form.anchor'};
+                }
+                $is_supp = 1;
+            }
+            my $type = 'ext';
+            if ($exttool) {
+                $type = 'tool';
+            } elsif (($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'}));
+                                                       $env{'form.idx'},$type,$cdom,
+                                                       $cnum,$hostname));
             return OK;
         } elsif ($env{'form.folderpath'} =~ /^supplemental/) {
             my $crstype = &Apache::loncommon::course_type();
             my $title = $env{'form.title'};
             if ($title eq '') {
-                $title = &mt('External Resource');
+                if ($is_ext) {
+                    $title = &mt('External Resource');
+                } else {
+                    $title = &mt('External Tool');
+                }
+            }
+            $title = &HTML::Entities::encode($title,'\'"<>&');
+            $is_supp = 1;
+            if ($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'};
+            $title = &HTML::Entities::encode($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/) && (!$exttool)) {
 #
 # This is uploaded homework
 #
@@ -160,7 +481,8 @@ sub handler {
 #
 # This is not homework
 #
-        if ($is_ext) {
+        if (($is_ext) || ($exttool)) {
+            $absolute = $env{'request.use_absolute'};
             $ENV{'QUERY_STRING'} =~ s/(^|\&)symb=[^\&]*/$1/;
             $ENV{'QUERY_STRING'} =~ s/\&$//;
         }
@@ -170,9 +492,13 @@ sub handler {
         }
 
         # encrypt url if not external
-        &Apache::lonenc::check_encrypt(\$url) if $url !~ /^https?\:/ ;
+        unless ($is_ext) {
+            &Apache::lonenc::check_encrypt(\$url);
+        }
 
-        $r->print( wrapper($url,$brcrum,$absolute,$is_ext) );
+        $r->print( wrapper($r,$url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,
+                           $linktext,$explanation,undef,$width,$height,$reuse,
+                           $is_supp) );
 
     } # not just the menu
     
@@ -199,21 +525,28 @@ described at http://www.lon-capa.org.
 
 =over
 
-=item wrapper($url,$brcrum,$absolute,$is_ext)
+=item wrapper($r,$url,$brcrum,$absolute,$is_ext,$is_pdf,$exttool,$linktext,$explanation,$title,$width,$height,$reuse,$is_supp)
 
 =over
 
-=item $url 
- 
-url to display by including in an iframe within a
-LON-CAPA page which has a standard LON-CAPA inline menu.
+=item $r
+
+request object
+
+=item $url
+
+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
 
 breadcrumbs for unregistered urls
 (i.e., external resources in Supplemental Content).
 
-=item $absolute 
+=item $absolute
 
 contains protocol (http or https) followed by
 the hostname, if menu items in the standard LON-CAPA
@@ -224,7 +557,9 @@ relative URLs.
 That will be the case where an external resource has been 
 served from port 80, when the server customarily serves
 requests using Apache/SSL (i.e., port 443). mod_rewrite 
-is used to switch requests for external resources  
+is used to switch requests for external resources and
+the syllabus: /public/<domain>/<courseid>/syllabus
+(which might also point at an external resource)
 from https:// to http:// where the the URL of the remote site 
 specified in the resource itself is http://.
 
@@ -233,21 +568,90 @@ 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.
 
-=back
+=item $is_pdf
 
-Returns markup for the entire page.
+true if URL is for a PDF (based on file extension).
 
-=item handler()
+=item $exttool
 
-=back
+If URL is for an External Tool, will contain the target type: iframe, window or tab.
 
-=cut
+=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 $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