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Revision 739 - (download) (as text) (annotate)
Fri Feb 21 20:49:49 2003 UTC (10 years, 3 months ago) by sh002i
File size: 20845 byte(s)
1. fixed some formatting in Problem
2. hardcopy allows correct answers, hints, solutions to be shown
3. privileged users are allowed to view/download "not yet open" sets
-sam

    1 ################################################################################
    2 # WeBWorK mod_perl (c) 2000-2002 WeBWorK Project
    3 # $Id$
    4 ################################################################################
    5 
    6 package WeBWorK::ContentGenerator::Problem;
    7 
    8 =head1 NAME
    9 
   10 WeBWorK::ContentGenerator::Problem - Allow a student to interact with a problem.
   11 
   12 =cut
   13 
   14 use strict;
   15 use warnings;
   16 use base qw(WeBWorK::ContentGenerator);
   17 use CGI qw();
   18 use File::Temp qw(tempdir);
   19 use WeBWorK::Form;
   20 use WeBWorK::PG;
   21 use WeBWorK::PG::IO;
   22 use WeBWorK::Utils qw(writeLog encodeAnswers decodeAnswers ref2string);
   23 
   24 ############################################################
   25 #
   26 # user
   27 # effectiveUser
   28 # key
   29 #
   30 # displayMode
   31 # showOldAnswers
   32 # showCorrectAnswers
   33 # showHints
   34 # showSolutions
   35 #
   36 # AnSwEr# - answer blanks in problem
   37 #
   38 # redisplay - name of the "Redisplay Problem" button
   39 # submitAnswers - name of "Submit Answers" button
   40 #
   41 ############################################################
   42 
   43 sub pre_header_initialize {
   44   my ($self, $setName, $problemNumber) = @_;
   45   my $courseEnv = $self->{courseEnvironment};
   46   my $r = $self->{r};
   47   my $userName = $r->param('user');
   48   my $effectiveUserName = $r->param('effectiveUser');
   49 
   50   ##### database setup #####
   51 
   52   my $cldb   = WeBWorK::DB::Classlist->new($courseEnv);
   53   my $wwdb   = WeBWorK::DB::WW->new($courseEnv);
   54   my $authdb = WeBWorK::DB::Auth->new($courseEnv);
   55 
   56   my $user            = $cldb->getUser($userName);
   57   my $effectiveUser   = $cldb->getUser($effectiveUserName);
   58   my $set             = $wwdb->getSet($effectiveUserName, $setName);
   59   my $problem         = $wwdb->getProblem($effectiveUserName, $setName, $problemNumber);
   60   my $psvn            = $wwdb->getPSVN($effectiveUserName, $setName);
   61   my $permissionLevel = $authdb->getPermissions($userName);
   62 
   63   $self->{cldb}            = $cldb;
   64   $self->{wwdb}            = $wwdb;
   65   $self->{authdb}          = $authdb;
   66 
   67   $self->{userName}        = $userName;
   68   $self->{user}            = $user;
   69   $self->{effectiveUser}   = $effectiveUser;
   70   $self->{set}             = $set;
   71   $self->{problem}         = $problem;
   72   $self->{permissionLevel} = $permissionLevel;
   73 
   74   ##### form processing #####
   75 
   76   # set options from form fields (see comment at top of file for names)
   77   my $displayMode        = $r->param("displayMode") || $courseEnv->{pg}->{options}->{displayMode};
   78   my $redisplay          = $r->param("redisplay");
   79   my $submitAnswers      = $r->param("submitAnswers");
   80   my $checkAnswers       = $r->param("checkAnswers");
   81   my $previewAnswers     = $r->param("previewAnswers");
   82 
   83   # coerce form fields into CGI::Vars format
   84   my $formFields = { WeBWorK::Form->new_from_paramable($r)->Vars };
   85 
   86   $self->{displayMode}    = $displayMode;
   87   $self->{redisplay}      = $redisplay;
   88   $self->{submitAnswers}  = $submitAnswers;
   89   $self->{checkAnswers}   = $checkAnswers;
   90   $self->{previewAnswers} = $previewAnswers;
   91   $self->{formFields}     = $formFields;
   92 
   93   ##### permissions #####
   94 
   95   # are we allowed to view this problem?
   96   $self->{isOpen} = time >= $set->open_date || $permissionLevel > 0;
   97   return unless $self->{isOpen};
   98 
   99   # what does the user want to do?
  100   my %want = (
  101     showOldAnswers     => $r->param("showOldAnswers")     || $courseEnv->{pg}->{options}->{showOldAnswers},
  102     showCorrectAnswers => $r->param("showCorrectAnswers") || $courseEnv->{pg}->{options}->{showCorrectAnswers},
  103     showHints          => $r->param("showHints")          || $courseEnv->{pg}->{options}->{showHints},
  104     showSolutions      => $r->param("showSolutions")      || $courseEnv->{pg}->{options}->{showSolutions},
  105     #recordAnswers      => $r->param("recordAnswers")      || 1,
  106     recordAnswers      => $submitAnswers,
  107   );
  108 
  109   # are certain options enforced?
  110   my %must = (
  111     showOldAnswers     => 0,
  112     showCorrectAnswers => 0,
  113     showHints          => 0,
  114     showSolutions      => 0,
  115     recordAnswers      => mustRecordAnswers($permissionLevel),
  116   );
  117 
  118   # does the user have permission to use certain options?
  119   my %can = (
  120     showOldAnswers     => 1,
  121     showCorrectAnswers => canShowCorrectAnswers($permissionLevel, $set->answer_date),
  122     showHints          => 1,
  123     showSolutions      => canShowSolutions($permissionLevel, $set->answer_date),
  124     recordAnswers      => canRecordAnswers($permissionLevel, $set->open_date, $set->due_date,
  125       $problem->max_attempts, $problem->num_correct + $problem->num_incorrect + 1),
  126       # num_correct+num_incorrect+1 -- as this happens before updating $problem
  127   );
  128 
  129   # final values for options
  130   my %will;
  131   foreach (keys %must) {
  132     $will{$_} = $can{$_} && ($want{$_} || $must{$_});
  133   }
  134 
  135   ##### sticky answers #####
  136 
  137   if (not $submitAnswers and $will{showOldAnswers}) {
  138     # do this only if new answers are NOT being submitted
  139     my %oldAnswers = decodeAnswers($problem->last_answer);
  140     $formFields->{$_} = $oldAnswers{$_} foreach keys %oldAnswers;
  141   }
  142 
  143   ##### translation #####
  144 
  145   my $pg = WeBWorK::PG->new(
  146     $courseEnv,
  147     $effectiveUser,
  148     $r->param('key'),
  149     $set,
  150     $problem,
  151     $psvn,
  152     $formFields,
  153     { # translation options
  154       displayMode     => $displayMode,
  155       showHints       => $will{showHints},
  156       showSolutions   => $will{showSolutions},
  157       refreshMath2img => $will{showHints} || $will{showSolutions},
  158       processAnswers  => 1,
  159     },
  160   );
  161 
  162   ##### fix hint/solution options #####
  163 
  164   $can{showHints}     &&= $pg->{flags}->{hintExists};
  165   $can{showSolutions} &&= $pg->{flags}->{solutionExists};
  166 
  167   ##### store fields #####
  168 
  169   $self->{want} = \%want;
  170   $self->{must} = \%must;
  171   $self->{can}  = \%can;
  172   $self->{will} = \%will;
  173 
  174   $self->{pg} = $pg;
  175 }
  176 
  177 sub if_warnings($$) {
  178   my ($self, $arg) = @_;
  179   return 0 unless $self->{isOpen};
  180   return $self->{pg}->{warnings} ne "";
  181 }
  182 
  183 sub if_errors($$) {
  184   my ($self, $arg) = @_;
  185   return 0 unless $self->{isOpen};
  186   return $self->{pg}->{flags}->{error_flag};
  187 }
  188 
  189 sub head {
  190   my $self = shift;
  191   return "" unless $self->{isOpen};
  192   return $self->{pg}->{head_text} if $self->{pg}->{head_text};
  193 }
  194 
  195 sub path {
  196   my $self = shift;
  197   my $args = $_[-1];
  198   my $setName = $self->{set}->id;
  199   my $problemNumber = $self->{problem}->id;
  200 
  201   my $ce = $self->{courseEnvironment};
  202   my $root = $ce->{webworkURLs}->{root};
  203   my $courseName = $ce->{courseName};
  204   return $self->pathMacro($args,
  205     "Home" => "$root",
  206     $courseName => "$root/$courseName",
  207     $setName => "$root/$courseName/$setName",
  208     "Problem $problemNumber" => "",
  209   );
  210 }
  211 
  212 sub siblings {
  213   my $self = shift;
  214   my $setName = $self->{set}->id;
  215   my $problemNumber = $self->{problem}->id;
  216 
  217   my $ce = $self->{courseEnvironment};
  218   my $root = $ce->{webworkURLs}->{root};
  219   my $courseName = $ce->{courseName};
  220 
  221   print CGI::strong("Problems"), CGI::br();
  222 
  223   my $wwdb = $self->{wwdb};
  224   my $effectiveUser = $self->{r}->param("effectiveUser");
  225   my @problems;
  226   push @problems, $wwdb->getProblem($effectiveUser, $setName, $_)
  227     foreach ($wwdb->getProblems($effectiveUser, $setName));
  228   foreach my $problem (sort { $a->id <=> $b->id } @problems) {
  229     print CGI::a({-href=>"$root/$courseName/$setName/".$problem->id."/?"
  230       . $self->url_authen_args . "&displayMode=" . $self->{displayMode}},
  231         "Problem ".$problem->id), CGI::br();
  232   }
  233 }
  234 
  235 sub nav {
  236   my $self = shift;
  237   my $args = $_[-1];
  238   my $setName = $self->{set}->id;
  239   my $problemNumber = $self->{problem}->id;
  240 
  241   my $ce = $self->{courseEnvironment};
  242   my $root = $ce->{webworkURLs}->{root};
  243   my $courseName = $ce->{courseName};
  244 
  245   my $wwdb          = $self->{wwdb};
  246   my $effectiveUser = $self->{r}->param("effectiveUser");
  247   my $tail = "&displayMode=".$self->{displayMode};
  248 
  249   my @links = ("Problem List" => "$root/$courseName/$setName");
  250 
  251   my $prevProblem = $wwdb->getProblem($effectiveUser, $setName, $problemNumber-1);
  252   my $nextProblem = $wwdb->getProblem($effectiveUser, $setName, $problemNumber+1);
  253   unshift @links, "Previous Problem" => $prevProblem
  254     ? "$root/$courseName/$setName/".$prevProblem->id
  255     : "";
  256   push @links, "Next Problem" => $nextProblem
  257     ? "$root/$courseName/$setName/".$nextProblem->id
  258     : "";
  259 
  260   return $self->navMacro($args, $tail, @links);
  261 }
  262 
  263 sub title {
  264   my $self = shift;
  265   my $setName = $self->{set}->id;
  266   my $problemNumber = $self->{problem}->id;
  267 
  268   return "$setName : Problem $problemNumber";
  269 }
  270 
  271 sub body {
  272   my $self = shift;
  273 
  274   return CGI::p(CGI::font({-color=>"red"}, "This problem is not available because the problem set that contains it is not yet open."))
  275     unless $self->{isOpen};
  276 
  277   # unpack some useful variables
  278   my $r               = $self->{r};
  279   my $wwdb            = $self->{wwdb};
  280   my $set             = $self->{set};
  281   my $problem         = $self->{problem};
  282   my $permissionLevel = $self->{permissionLevel};
  283   my $submitAnswers   = $self->{submitAnswers};
  284   my $checkAnswers    = $self->{checkAnswers};
  285   my $previewAnswers  = $self->{previewAnswers};
  286   my %want            = %{ $self->{want} };
  287   my %can             = %{ $self->{can} };
  288   my %must            = %{ $self->{must} };
  289   my %will            = %{ $self->{will} };
  290   my $pg              = $self->{pg};
  291 
  292   ##### translation errors? #####
  293 
  294   if ($pg->{flags}->{error_flag}) {
  295     return $self->errorOutput($pg->{errors}, $pg->{body_text});
  296   }
  297 
  298   ##### answer processing #####
  299 
  300   # if answers were submitted:
  301   if ($submitAnswers) {
  302     # store answers in DB for sticky answers
  303     my %answersToStore;
  304     my %answerHash = %{ $pg->{answers} };
  305     $answersToStore{$_} = $answerHash{$_}->{original_student_ans}
  306       foreach (keys %answerHash);
  307     my $answerString = encodeAnswers(%answersToStore,
  308       @{ $pg->{flags}->{ANSWER_ENTRY_ORDER} });
  309     $problem->last_answer($answerString);
  310     $wwdb->setProblem($problem);
  311 
  312     # store state in DB if it makes sense
  313     if ($will{recordAnswers}) {
  314       $problem->attempted(1);
  315       $problem->status($pg->{state}->{recorded_score});
  316       $problem->num_correct($pg->{state}->{num_of_correct_ans});
  317       $problem->num_incorrect($pg->{state}->{num_of_incorrect_ans});
  318       $wwdb->setProblem($problem);
  319       # write to the transaction log, just to make sure
  320       writeLog($self->{courseEnvironment}, "transaction",
  321         $problem->id."\t".
  322         $problem->set_id."\t".
  323         $problem->login_id."\t".
  324         $problem->source_file."\t".
  325         $problem->value."\t".
  326         $problem->max_attempts."\t".
  327         $problem->problem_seed."\t".
  328         $problem->status."\t".
  329         $problem->attempted."\t".
  330         $problem->last_answer."\t".
  331         $problem->num_correct."\t".
  332         $problem->num_incorrect
  333       );
  334     }
  335   }
  336 
  337   ##### output #####
  338 
  339   # attempt summary
  340   if ($submitAnswers or $will{showCorrectAnswers}) {
  341     # print this if user submitted answers OR requested correct answers
  342     print $self->attemptResults($pg, $submitAnswers,
  343       $will{showCorrectAnswers},
  344       $pg->{flags}->{showPartialCorrectAnswers}, 0);
  345   } elsif ($checkAnswers) {
  346     # print this if user previewed answers
  347     print $self->attemptResults($pg, 1, 0, 1, 0);
  348       # show attempt answers
  349       # don't show correct answers
  350       # show attempt results (correctness)
  351       # don't show attempt previews
  352   } elsif ($previewAnswers) {
  353     # print this if user previewed answers
  354     print $self->attemptResults($pg, 1, 0, 0, 1);
  355       # show attempt answers
  356       # don't show correct answers
  357       # don't show attempt results (correctness)
  358       # show attempt previews
  359   }
  360 
  361   # score summary
  362   my $attempts = $problem->num_correct + $problem->num_incorrect;
  363   my $attemptsNoun = $attempts != 1 ? "times" : "time";
  364   my $lastScore = int ($problem->status * 100) . "%";
  365   my ($attemptsLeft, $attemptsLeftNoun);
  366   if ($problem->max_attempts == -1) {
  367     # unlimited attempts
  368     $attemptsLeft = "unlimited";
  369     $attemptsLeftNoun = "attempts";
  370   } else {
  371     $attemptsLeft = $problem->max_attempts - $attempts;
  372     $attemptsLeftNoun = $attemptsLeft == 1 ? "attempt" : "attempts";
  373   }
  374   my $setClosedMessage;
  375   if (time < $set->open_date or time > $set->due_date) {
  376     $setClosedMessage = "This problem set is closed.";
  377     if ($permissionLevel > 0) {
  378       $setClosedMessage .= " Since you are a privileged user, additional attempts will be recorded.";
  379     } else {
  380       $setClosedMessage .= " Additional attempts will not be recorded.";
  381     }
  382   }
  383   print CGI::p(
  384     "You have attempted this problem $attempts $attemptsNoun.", CGI::br(),
  385     $problem->attempted
  386       ? "Your recorded score is $lastScore." . CGI::br()
  387       : "",
  388     "You have $attemptsLeft $attemptsLeftNoun remaining.", CGI::br(),
  389     $setClosedMessage,
  390   );
  391 
  392   print CGI::hr();
  393 
  394   # main form
  395   print
  396     CGI::startform("POST", $r->uri),
  397     $self->hidden_authen_fields,
  398     CGI::p(CGI::i($pg->{result}->{msg})),
  399     CGI::p($pg->{body_text}),
  400     CGI::p(
  401       ($can{recordAnswers}
  402         ? CGI::submit(-name=>"submitAnswers",
  403           -label=>"Submit Answers")
  404         : ""),
  405       ($can{recordAnswers}
  406         ? CGI::submit(-name=>"checkAnswers",
  407           -label=>"Check Answers")
  408         : ""),
  409       CGI::submit(-name=>"previewAnswers",
  410         -label=>"Preview Answers"),
  411     ),
  412     $self->viewOptions(),
  413     CGI::endform();
  414 
  415   # feedback form
  416   my $ce = $self->{courseEnvironment};
  417   my $root = $ce->{webworkURLs}->{root};
  418   my $courseName = $ce->{courseName};
  419   my $feedbackURL = "$root/$courseName/feedback/";
  420   print
  421     CGI::startform("POST", $feedbackURL),
  422     $self->hidden_authen_fields,
  423     CGI::hidden("module",             __PACKAGE__),
  424     CGI::hidden("set",                $set->id),
  425     CGI::hidden("problem",            $problem->id),
  426     CGI::hidden("displayMode",        $self->{displayMode}),
  427     CGI::hidden("showOldAnswers",     $will{showOldAnswers}),
  428     CGI::hidden("showCorrectAnswers", $will{showCorrectAnswers}),
  429     CGI::hidden("showHints",          $will{showHints}),
  430     CGI::hidden("showSolutions",      $will{showSolutions}),
  431     CGI::p({-align=>"right"},
  432       CGI::submit(-name=>"feedbackForm", -label=>"Send Feedback")
  433     ),
  434     CGI::endform();
  435 
  436   # warning output
  437   if ($pg->{warnings} ne "") {
  438     print CGI::hr(), $self->warningOutput($pg->{warnings});
  439   }
  440 
  441   # debugging stuff
  442   if (1) {
  443     print
  444       CGI::hr(),
  445       CGI::h2("debugging information"),
  446       CGI::h3("form fields"),
  447       ref2string($self->{formFields}),
  448       CGI::h3("user object"),
  449       ref2string($self->{user}),
  450       CGI::h3("set object"),
  451       ref2string($set),
  452       CGI::h3("problem object"),
  453       ref2string($problem),
  454       CGI::h3("PG object"),
  455       ref2string($pg, {'WeBWorK::PG::Translator' => 1});
  456   }
  457 
  458   return "";
  459 }
  460 
  461 ##### output utilities #####
  462 
  463 sub attemptResults($$$$$) {
  464   my $self = shift;
  465   my $pg = shift;
  466   my $showAttemptAnswers = shift;
  467   my $showCorrectAnswers = shift;
  468   my $showAttemptResults = $showAttemptAnswers && shift;
  469   my $showAttemptPreview = shift || 0;
  470   my $problemResult = $pg->{result}; # the overall result of the problem
  471   my @answerNames = @{ $pg->{flags}->{ANSWER_ENTRY_ORDER} };
  472 
  473   my $showMessages = $showAttemptAnswers && grep { $pg->{answers}->{$_}->{ans_message} } @answerNames;
  474 
  475   my $header = CGI::th("part");
  476   $header .= $showAttemptAnswers ? CGI::th("entered")  : "";
  477   $header .= $showAttemptPreview ? CGI::th("preview")  : "";
  478   $header .= $showCorrectAnswers ? CGI::th("correct")  : "";
  479   $header .= $showAttemptResults ? CGI::th("result")   : "";
  480   $header .= $showMessages       ? CGI::th("messages") : "";
  481   my @tableRows = ( $header );
  482   my $numCorrect;
  483   foreach my $name (@answerNames) {
  484     my $answerResult  = $pg->{answers}->{$name};
  485     my $studentAnswer = $answerResult->{student_ans}; # original_student_ans
  486     my $preview       = ($showAttemptPreview
  487                           ? $self->previewAnswer($answerResult)
  488           : "");
  489     my $correctAnswer = $answerResult->{correct_ans};
  490     my $answerScore   = $answerResult->{score};
  491     my $answerMessage = $showMessages ? $answerResult->{ans_message} : "";
  492 
  493     $numCorrect += $answerScore > 0;
  494     my $resultString = $answerScore ? "correct" : "incorrect";
  495 
  496     # get rid of the goofy prefix on the answer names (supposedly, the format
  497     # of the answer names is changeable. this only fixes it for "AnSwEr"
  498     $name =~ s/^AnSwEr//;
  499 
  500     my $row = CGI::td($name);
  501     $row .= $showAttemptAnswers ? CGI::td($studentAnswer) : "";
  502     $row .= $showAttemptPreview ? CGI::td($preview)       : "";
  503     $row .= $showCorrectAnswers ? CGI::td($correctAnswer) : "";
  504     $row .= $showAttemptResults ? CGI::td($resultString)  : "";
  505     $row .= $answerMessage      ? CGI::td($answerMessage) : "";
  506     push @tableRows, $row;
  507   }
  508 
  509   my $numCorrectNoun = $numCorrect == 1 ? "question" : "questions";
  510   my $scorePercent = int ($problemResult->{score} * 100) . "\%";
  511   my $summary = "On this attempt, you answered $numCorrect $numCorrectNoun out of "
  512     . scalar @answerNames . " correct, for a score of $scorePercent.";
  513   return CGI::table({-border=>1}, CGI::Tr(\@tableRows)) . CGI::p($summary);
  514 }
  515 
  516 sub viewOptions($) {
  517   my $self = shift;
  518   my $displayMode = $self->{displayMode};
  519   my %must = %{ $self->{must} };
  520   my %can  = %{ $self->{can}  };
  521   my %will = %{ $self->{will} };
  522 
  523   my $optionLine;
  524   $can{showOldAnswers} and $optionLine .= join "",
  525     "Show: &nbsp;",
  526     CGI::checkbox(
  527       -name    => "showOldAnswers",
  528       -checked => $will{showOldAnswers},
  529       -label   => "Saved answers",
  530     ), "&nbsp;&nbsp;";
  531   $can{showCorrectAnswers} and $optionLine .= join "",
  532     CGI::checkbox(
  533       -name    => "showCorrectAnswers",
  534       -checked => $will{showCorrectAnswers},
  535       -label   => "Correct answers",
  536     ), "&nbsp;&nbsp;";
  537   $can{showHints} and $optionLine .= join "",
  538     CGI::checkbox(
  539       -name    => "showHints",
  540       -checked => $will{showHints},
  541       -label   => "Hints",
  542     ), "&nbsp;&nbsp;";
  543   $can{showSolutions} and $optionLine .= join "",
  544     CGI::checkbox(
  545       -name    => "showSolutions",
  546       -checked => $will{showSolutions},
  547       -label   => "Solutions",
  548     ), "&nbsp;&nbsp;";
  549   $optionLine and $optionLine .= join "", CGI::br();
  550 
  551   return CGI::div({-style=>"border: thin groove; padding: 1ex; margin: 2ex"},
  552       "View equations as: &nbsp;",
  553     CGI::radio_group(
  554       -name    => "displayMode",
  555       -values  => ['plainText', 'formattedText', 'images'],
  556       -default => $displayMode,
  557       -labels  => {
  558         plainText     => "plain text",
  559         formattedText => "formatted text",
  560         images        => "images",
  561       }
  562     ), CGI::br(),
  563     $optionLine,
  564     CGI::submit(-name=>"redisplay", -label=>"Redisplay Problem"),
  565   );
  566 }
  567 
  568 sub previewAnswer($$) {
  569   my ($self, $answerResult) = @_;
  570   my $ce            = $self->{courseEnvironment};
  571   my $effectiveUser = $self->{effectiveUser};
  572   my $set           = $self->{set};
  573   my $problem       = $self->{problem};
  574   my $displayMode   = $self->{displayMode};
  575 
  576   # note: right now, we have to do things completely differently when we are
  577   # rendering math from INSIDE the translator and from OUTSIDE the translator.
  578   # so we'll just deal with each case explicitly here. there's some code
  579   # duplication that can be dealt with later by abstracting out tth/dvipng/etc.
  580 
  581   my $tex = $answerResult->{preview_latex_string};
  582 
  583   return "" unless $tex;
  584 
  585   if ($displayMode eq "plainText") {
  586     return $tex;
  587   } elsif ($displayMode eq "formattedText") {
  588     my $tthCommand = $ce->{externalPrograms}->{tth}
  589       . " -L -f5 -r 2> /dev/null <<END_OF_INPUT; echo > /dev/null\n"
  590       . "\\(".$tex."\\)\n"
  591       . "END_OF_INPUT\n";
  592 
  593     # call tth
  594     my $result = `$tthCommand`;
  595     if ($?) {
  596       return "<b>[tth failed: $? $@]</b>";
  597     }
  598     return $result;
  599   } elsif ($displayMode eq "images") {
  600     # how are we going to name this?
  601     my $targetPathCommon = "/png/"
  602       . $effectiveUser->id . "."
  603       . $set->id . "."
  604       . $problem->id . "."
  605       . $answerResult->{ans_name} . ".png";
  606 
  607     # figure out where to put things
  608     my $wd = tempdir("webwork-dvipng-XXXXXXXX", DIR => $ce->{courseDirs}->{html_temp});
  609     my $latex = $ce->{externalPrograms}->{latex};
  610     my $dvipng = $ce->{externalPrograms}->{dvipng};
  611     my $targetPath = $ce->{courseDirs}->{html_temp} . $targetPathCommon;
  612         # should use surePathToTmpFile, but we have to
  613         # isolate it from the problem enivronment first
  614     my $targetURL = $ce->{courseURLs}->{html_temp} . $targetPathCommon;
  615 
  616     # call dvipng to generate a preview
  617     dvipng($wd, $latex, $dvipng, $tex, $targetPath);
  618     if (-e $targetPath) {
  619       return "<img src=\"$targetURL\" alt=\"$tex\" />";
  620     } else {
  621       return "<b>[math2img failed]</b>";
  622     }
  623   }
  624 }
  625 
  626 ##### permission queries #####
  627 
  628 # this stuff should be abstracted out into the permissions system
  629 # however, the permission system only knows about things in the
  630 # course environment and the username. hmmm...
  631 
  632 # also, i should fix these so that they have a consistent calling
  633 # format -- perhaps:
  634 #   canPERM($courseEnv, $user, $set, $problem, $permissionLevel)
  635 
  636 sub canShowCorrectAnswers($$) {
  637   my ($permissionLevel, $answerDate) = @_;
  638   return $permissionLevel > 0 || time > $answerDate;
  639 }
  640 
  641 sub canShowSolutions($$) {
  642   my ($permissionLevel, $answerDate) = @_;
  643   return canShowCorrectAnswers($permissionLevel, $answerDate);
  644 }
  645 
  646 sub canRecordAnswers($$$$$) {
  647   my ($permissionLevel, $openDate, $dueDate, $maxAttempts, $attempts) = @_;
  648   my $permHigh = $permissionLevel > 0;
  649   my $timeOK = time >= $openDate && time <= $dueDate;
  650   my $attemptsOK = $maxAttempts == -1 || $attempts <= $maxAttempts;
  651   my $recordAnswers = $permHigh || ($timeOK && $attemptsOK);
  652   return $recordAnswers;
  653 }
  654 
  655 sub mustRecordAnswers($) {
  656   my ($permissionLevel) = @_;
  657   return $permissionLevel == 0;
  658 }
  659 
  660 1;

aubreyja at gmail dot com
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