--- loncom/homework/functionplotresponse.pm	2010/10/04 18:28:53	1.3
+++ loncom/homework/functionplotresponse.pm	2010/10/31 12:33:02	1.21
@@ -1,7 +1,7 @@
 # LearningOnline Network with CAPA
 # option list style responses
 #
-# $Id: functionplotresponse.pm,v 1.3 2010/10/04 18:28:53 www Exp $
+# $Id: functionplotresponse.pm,v 1.21 2010/10/31 12:33:02 www Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -33,9 +33,14 @@ use Apache::lonlocal;
 use Apache::lonnet;
 
 BEGIN {
-  &Apache::lonxml::register('Apache::functionplotresponse',('functionplotresponse'));
+  &Apache::lonxml::register('Apache::functionplotresponse',('functionplotresponse','backgroundplot','spline','splinerule'));
 }
 
+#
+# There can be a number of applets on a page, each called ggbApplet_$id, 
+# where $id is the "_"-concatenated part and responseid
+#
+
 sub geogebra_startcode {
     my ($id)=@_;
     return (<<ENDSTARTCODE);
@@ -49,12 +54,18 @@ sub geogebra_endcode {
     return &Apache::lonhtmlcommon::java_not_enabled()."</applet>\n";
 }
 
+#
+# This is the internal GeoGebra bytecode which defines the spline functions
+#
 sub geogebra_spline_program {
     return (<<ENDSPLINEPROGRAM);
 <param name="ggbBase64" value="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"/>
 ENDSPLINEPROGRAM
 }
 
+#
+# The standard set of parameters inside <applet>
+#
 sub geogebra_default_parameters {
    my ($id)=@_;
    return(<<ENDDEFAULTPARAMETERS);
@@ -82,13 +93,33 @@ sub geogebra_default_parameters {
 ENDDEFAULTPARAMETERS
 }
 
+#
+# This subroutine is called by LON-CAPA at </problem>
+# Each applet on the page will call function ggbOnInit when it is done loading
+# This function in turn will call the respective function registered by start_init_script
+# Which one of the registered functions is called is determined by ggbOnInitParam, which GeoGebra passes to ggbOnInit
+#
+
 sub init_script {
-   if ($Apache::functionplotresponse::callscripts) {
+   if ($#Apache::functionplotresponse::callscripts>=0) {
+      my $script='';
+      foreach my $id (@Apache::functionplotresponse::callscripts) {
+          $script.="if (param=='applet_$id') { loaded_$id=true; }\n";
+      }
+      $script.="if (".join(' && ',map { "loaded_$_" } (@Apache::functionplotresponse::callscripts)).
+               ") { setTimeout('ggbInitAll()',20) }";
+      my $calls=join("\n",map { "ggbInit_$_();" } (@Apache::functionplotresponse::callscripts)); 
       return (<<ENDGGBINIT);
 <script type="text/javascript">
 // <![CDATA[
+// Function that each applet will call when loaded
+// It will pass "its" parameter
+// Set flags for when an applet is loaded, wait till all are loaded, and then some
 function ggbOnInit(param) {
-$Apache::functionplotresponse::callscripts
+$script
+}
+function ggbInitAll() {
+$calls
 }
 // ]]>
 </script>
@@ -96,17 +127,314 @@ ENDGGBINIT
    }
 }
 
+#
+# Each Geogebra applet is supposed to call this when parameters change
+# Changes the hidden fields on the web page
+#
+sub update_script {
+    my ($id)=@_;
+    return (<<ENDUPDATESCRIPT);
+<script type="text/javascript">
+// <![CDATA[
+function updatePointCoordinates_$id(coordinateName) {
+            var x = document.ggbApplet_$id.getXcoord(coordinateName);
+            var y = document.ggbApplet_$id.getYcoord(coordinateName);
+            document.lonhomework.elements["HWVAL_$id\_" + coordinateName + "_x"].value = x;
+            document.lonhomework.elements["HWVAL_$id\_" + coordinateName + "_y"].value = y;
+        }
+// ]]>
+</script>
+ENDUPDATESCRIPT
+}
+
+#
+# Register the above update-handler for a variable
+#
+
+sub update_register {
+   my ($id,$variable)=@_;
+   return "document.ggbApplet_$id.registerObjectUpdateListener('$variable','updatePointCoordinates_$id');\n";
+}
+
+#
+# Set a coordinate variable
+#
+sub set_coordinate {
+   my ($id,$variable,$x,$y)=@_;
+   return (<<ENDSETVARIABLE);
+document.ggbApplet_$id.evalCommand("$variable=($x,$y)");
+ENDSETVARIABLE
+}
+
+#
+# Input field name for a coordinate variable
+#
+
+sub field_name {
+    my ($id,$variable,$name)=@_;
+    return "HWVAL_$id\_$variable\_$name";
+}
+
+#
+# Generate an input field for a coordinate variable
+#
+
+sub generate_input_field {
+    my ($id,$variable,$x,$y)=@_;
+    $Apache::functionplotresponse::inputfields.=
+       "<input type='hidden' name='".&field_name($id,$variable,'x')."' value='$x' />\n".
+       "<input type='hidden' name='".&field_name($id,$variable,'y')."' value='$y' />\n";
+}
+
+#
+# Initialize a new coordinate variable at set a listener on it
+#
+sub new_coordinate {
+    my ($id,$variable,$x,$y)=@_;
+    if (defined($Apache::functionplotresponse::previous{&field_name($id,$variable,'x')})) {
+       $x=$Apache::functionplotresponse::previous{&field_name($id,$variable,'x')};
+    }
+    if (defined($Apache::functionplotresponse::previous{&field_name($id,$variable,'y')})) {
+       $y=$Apache::functionplotresponse::previous{&field_name($id,$variable,'y')};
+    }
+    &generate_input_field($id,$variable,$x,$y);
+    return &set_coordinate($id,$variable,$x,$y).&update_register($id,$variable);
+}
+
+#
+# This registers the init-function call for ggbOnInit, which LON-CAPA will place at </problem>
+# It then starts the right headers
+#
 sub start_init_script {
     my ($id)=@_;
-    $Apache::functionplotresponse::callscripts.="if (param=='applet_$id') { ggbInit_$id(); }\n";
+# Add id to the list of ggbInit_$id functions that need to be called
+    push(@Apache::functionplotresponse::callscripts,$id);
+# ... and open this function
     return (<<ENDSTARTINIT);
 <script type="text/javascript">
 // <![CDATA[
+// variable that will eventually be passed back to the server
+var coordinateMap_$id = [];
+// flag for not loaded yet
+var loaded_$id=false;
+// Init-function for applet
 function ggbInit_$id() {
-   alert("Hello $id");
 ENDSTARTINIT
 }
 
+#
+# This sets the axes inside ggbInit_$id
+#
+
+sub axes_script {
+    my ($id,$xmin,$xmax,$ymin,$ymax,$xvisible,$yvisible,$gvisible)=@_;
+    return (<<ENDAXESSCRIPT);
+            // changes (xmin, xmax, ymin, ymax)
+            document.ggbApplet_$id.setCoordSystem($xmin,$xmax,$ymin,$ymax);
+
+            // makes the (x,y) axis (in)visible
+            document.ggbApplet_$id.setAxesVisible($xvisible,$yvisible);
+            // makes the grid (in)visible
+            document.ggbApplet_$id.setGridVisible($gvisible);
+ENDAXESSCRIPT
+}
+
+sub axes_label {
+    my ($id,$xlabel,$ylabel)=@_;
+    unless ($xlabel || $ylabel) { return ''; }
+    my $return='document.ggbApplet_'.$id.'.evalCommand("topRight=Corner[3]");';
+    if ($xlabel) {
+       $return.=(<<ENDXAXISLABELSCRIPT);
+document.ggbApplet_$id.evalCommand("Xlabel=(x(topRight)-AxisStepX[],AxisStepY[]/6)");
+document.ggbApplet_$id.setVisible("Xlabel",false);
+document.ggbApplet_$id.evalCommand("Text[\\"$xlabel\\", Xlabel]");
+ENDXAXISLABELSCRIPT
+    }
+    if ($ylabel) {
+       $return.=(<<ENDYAXISLABELSCRIPT);
+document.ggbApplet_$id.evalCommand("Ylabel=(AxisStepX[]/6,y(topRight)-AxisStepY[]/3)");
+document.ggbApplet_$id.setVisible("Ylabel",false);
+document.ggbApplet_$id.evalCommand("Text[\\"$ylabel\\", Ylabel]");
+ENDYAXISLABELSCRIPT
+    }
+    return $return;
+}
+
+sub plot_script {
+   my ($id,$function,$fixed)=@_;
+   if ($fixed) {
+# Use stupid trick to nail this to a location
+# Oddly, it seems like only one plot cannot be nailed to a location
+# Non-nailed-down plots apparently get overwritten
+      return (<<ENDPLOTSCRIPT);
+            document.ggbApplet_$id.evalCommand("a=1");
+            document.ggbApplet_$id.setVisible("a",false);
+            // This MUST be a DEPENDENT OBJECT in order to be locked down:
+            document.ggbApplet_$id.evalCommand("y=a*($function)");
+ENDPLOTSCRIPT
+   } else {
+       return "document.ggbApplet_$id.evalCommand('y=$function')";
+   }
+}
+
+#
+# Subroutine that generates code for spline $label based on stored information
+#
+
+sub generate_spline {
+   my ($id,$label)=@_;
+   my $result='';
+   my $order=$Apache::functionplotresponse::splineorder{$label};
+   my $x=$Apache::functionplotresponse::splineinitx{$label};
+   my $y=$Apache::functionplotresponse::splineinity{$label};
+   my $sx=$Apache::functionplotresponse::splinescalex{$label};
+   my $sy=$Apache::functionplotresponse::splinescaley{$label};
+   my @coords=();
+   foreach my $i (1..$order) {
+       $result.=&new_coordinate($id,$label.'P'.$i,$x,$y);
+       $x+=$sx/(2.*($order-1));
+       push(@coords,$label.'P'.$i);
+       $result.=&new_coordinate($id,$label.'S'.$i,$x,$y+$sy);
+       $x+=$sx/(2.*($order-1));
+       push(@coords,$label.'S'.$i);
+   }
+   $result.='document.ggbApplet_'.$id.'.evalCommand("Spline'.$order.'['.join(',',@coords).']");'."\n";
+   return $result;
+}
+#
+# <backgroundplot function="..." fixed="yes/no" />
+#
+sub start_backgroundplot {
+   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
+   my $result='';
+   my $internalid = $Apache::inputtags::part.'_'.$Apache::inputtags::response[-1];
+   my $function=&Apache::lonxml::get_param('function',$parstack,$safeeval);
+   my $fixed=(&Apache::lonxml::get_param('fixed',$parstack,$safeeval)=~/on|true|yes|1/i?1:0);
+ 
+   unless ($function) { $function="0"; }
+   if ($target eq 'web') {
+      $result.=&plot_script($internalid,$function,$fixed);
+   } elsif ($target eq 'edit') {
+        $result=&Apache::edit::tag_start($target,$token,'Background Function Plot').
+             &Apache::edit::text_arg('Function:','function',
+                                     $token,'16').
+             &Apache::edit::select_arg('Fixed location:','fixed',
+                                  ['yes','no'],$token).
+             &Apache::edit::end_row();
+  } elsif ($target eq 'modified') {
+    my $constructtag=&Apache::edit::get_new_args($token,$parstack,
+                                                 $safeeval,'function','fixed');
+    if ($constructtag) { $result=&Apache::edit::rebuild_tag($token); }
+  }
+  return $result;
+}
+
+sub end_backgroundplot {
+   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
+   my $result='';
+   if ($target eq 'edit') {
+       $result=&Apache::edit::end_table();
+   }
+   return $result;
+}
+
+#
+# <splinerule ... />
+#
+sub start_splinerule {
+   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
+   my $result='';
+   my $internalid = $Apache::inputtags::part.'_'.$Apache::inputtags::response[-1];
+   if ($target eq 'edit') {
+        $result=&Apache::edit::tag_start($target,$token,'Spline Evaluation Rule').
+                &Apache::edit::end_row();
+   }
+   return $result;
+}
+
+sub end_splinerule {
+   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
+   my $result='';
+   if ($target eq 'edit') {
+       $result=&Apache::edit::end_table();
+   }
+   return $result;
+}
+
+
+#
+# <spline label="..." order="1,2,3,4" initx="..." inity="..." scalex="..." scaley="..." />
+#
+# Unfortunately, GeoGebra seems to want all splines after everything else, so we need to store them
+#
+sub start_spline {
+   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
+   my $result='';
+   if ($target eq 'web') {
+      my $label=&Apache::lonxml::get_param('label',$parstack,$safeeval);
+      $Apache::functionplotresponse::counter++;
+      if ($label=~/\W/) {
+         &Apache::lonxml::warning(&mt('Spline labels should only contain alphanumeric characters.'));
+      }
+      $label=~s/\W//gs;
+      unless ($label) { $label='S'.$Apache::functionplotresponse::counter; }
+      if ($Apache::functionplotresponse::splineorder{$label}) {
+         &Apache::lonxml::error(&mt('Spline labels must be unique.'));
+      }
+
+      my $order=&Apache::lonxml::get_param('order',$parstack,$safeeval);
+      if ($order<2) { $order=2; }
+      if ($order>8) { $order=8; }
+      $Apache::functionplotresponse::splineorder{$label}=$order;
+
+      my $x=&Apache::lonxml::get_param('initx',$parstack,$safeeval);
+      unless ($x) { $x=0; }
+      $Apache::functionplotresponse::splineinitx{$label}=$x;
+
+      my $y=&Apache::lonxml::get_param('inity',$parstack,$safeeval);
+      unless ($y) { $y=0; }
+      $Apache::functionplotresponse::splineinity{$label}=$y;
+
+      my $sx=&Apache::lonxml::get_param('scalex',$parstack,$safeeval);
+      unless ($sx) { $sx=$order; }
+      $Apache::functionplotresponse::splinescalex{$label}=$sx;
+
+      my $sy=&Apache::lonxml::get_param('scaley',$parstack,$safeeval);
+      unless ($sy) { $sy=2; }
+      $Apache::functionplotresponse::splinescaley{$label}=$sy;
+   } elsif ($target eq 'edit') {
+        $result=&Apache::edit::tag_start($target,$token,'Spline').
+             &Apache::edit::text_arg('Label:','label',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::select_arg('Order:','order',
+                                  ['2','3','4','5','6','7','8','9'],$token).'&nbsp;'.
+             &Apache::edit::text_arg('Initial x-value:','initx',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::text_arg('Initial y-value:','inity',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::text_arg('Scale x:','scalex',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::text_arg('Scale y:','scaley',
+                                     $token,'4').
+             &Apache::edit::end_row();
+  } elsif ($target eq 'modified') {
+    my $constructtag=&Apache::edit::get_new_args($token,$parstack,
+                                                 $safeeval,'label','order','initx','inity',
+                                                           'scalex','scaley');
+    if ($constructtag) { $result=&Apache::edit::rebuild_tag($token); }
+  }
+  return $result;
+}
+
+sub end_spline {
+   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
+   my $result='';
+   if ($target eq 'edit') {
+       $result=&Apache::edit::end_table();
+   }
+   return $result;
+}
+ 
 sub end_init_script {
     return (<<ENDENDINIT);
 }
@@ -115,21 +443,246 @@ sub end_init_script {
 ENDENDINIT
 }
 
+#
+# Storing and restoring spline coordinates from part answers
+#
+sub decode_previous_answer {
+   my ($answer)=@_;
+   foreach my $coordinate (split(/\,/,$answer)) {
+      my ($key,$value)=split(/\=/,$coordinate);
+      $Apache::functionplotresponse::previous{$key}=$value;
+   }
+}
+
+sub get_answer_from_form_fields {
+   my ($id)=@_;
+   my $answer='';
+   my %coords=();
+   foreach my $field (keys(%env)) {
+      if ($field=~/^form\.HWVAL\_$id/) {
+         $field=~/^form\.(.*)$/;
+         $coords{$1}=$env{$field};
+      }
+   }
+   $answer=join(',',map { $_.'='.$coords{$_} } (sort(keys(%coords))));
+   return ($answer,%coords);
+}
+
+#
+# The following functions calculate the cubic-hermite splines server-side
+#
+
+sub cubic_hermite {
+   my ($t,$p1,$s1,$p2,$s2)=@_;
+   return (2.*$t*$t*$t-3.*$t*$t+1.)*$p1 + 5.*($t*$t*$t-2.*$t*$t+$t)*($s1-$p1)+
+          (-2.*$t*$t*$t+3.*$t*$t)  *$p2 + 5.*($t*$t*$t-$t*$t)      *($s2-$p2);
+}
+
+#
+# d/dt(...)
+# 
+
+sub ddt_cubic_hermite {
+   my ($t,$p1,$s1,$p2,$s2)=@_;
+   return (6.*$t*$t-6.*$t) *$p1 + 5.*(3.*$t*$t-4.*$t+1.)*($s1-$p1)+
+          (-6.*$t*$t+6.*$t)*$p2 + 5.*(3.*$t*$t-2.*$t)   *($s2-$p2);
+}
+
+#
+# d^2/dt^2(...)
+#
+
+sub d2dt2_cubic_hermite {
+   my ($t,$p1,$s1,$p2,$s2)=@_;
+   return (12.*$t-6.) *$p1 + 5.*(6.*$t-4.)*($s1-$p1)+
+          (-12.*$t+6.)*$p2 + 5.*(6.*$t-2.)*($s2-$p2);
+}
+
+#
+# Array index calculation
+#
+sub array_index {
+   my ($xmin,$xmax,$x)=@_;
+   return int(($x-$xmin)/($xmax-$xmin)*200.+0.5);
+}
+
+#
+# Actual x-value of array index
+#
+
+sub index_x {
+   my ($xmin,$xmax,$i)=@_;
+   return $i*($xmax-$xmin)/200.+$xmin;
+}
+
+#
+# Assume function to be linear between array points
+# Return the two indices and the scale factor
+#
+
+sub indices_scale {
+   my ($xmin,$xmax,$x)=@_;
+   my $i=&array_index($xmin,$xmax,$x);
+   my $xr=&index_x($xmin,$xmax,$i);
+   &Apache::lonnet::logthis("x:$x i:$i xr:$xr");
+   if ($xr<$x) {
+# Desired x is right of array index
+      if ($i>=200) { return (200,200,0); }
+      return($i,$i+1,200.*($x-$xr)/($xmax-$xmin));
+   } elsif ($xr>$x) {
+# Desired x is left of array index
+      if ($i<=0) { return (0,0,0); }
+      return($i-1,$i,1.-200.*($xr-$x)/($xmax-$xmin));
+   } else {
+# Desired x is at array index (unlikely, but ...)
+      if ($i>=200) { return (200,200,0); }
+      if ($i<=0) { return (0,0,0); }
+      return ($i,$i,0);
+   }
+}
+
+#
+# Function value
+#
+
+sub func_val {
+   my ($xmin,$xmax,$x)=@_;
+   my ($il,$ih,$factor)=&indices_scale($xmin,$xmax,$x);
+   my $fl=$Apache::functionplotresponse::func[$il];
+   my $fh=$Apache::functionplotresponse::func[$ih];
+   unless (defined($fl) || defined($fh)) { return undef; }
+   unless (defined($fl)) { return $fh; }
+   unless (defined($fh)) { return $fl; }
+   my $func=$fl+$factor*($fh-$fl);
+   &Apache::lonnet::logthis("x:$x func:$func factor:$factor il:$il ih:$ih fil:$fl fih:$fh");
+   return $func;
+}
+
+#
+# Populate the arrays
+#
+
+sub populate_arrays {
+    my ($id,$xmin,$xmax)=@_;
+    for (my $i=0; $i<=200; $i++) {
+       $Apache::functionplotresponse::func[$i]=undef;
+       $Apache::functionplotresponse::dfunddx[$i]=undef;
+       $Apache::functionplotresponse::d2funcd2x[$i]=undef;
+    }
+    unless ($xmax>$xmin) { return 'no_func'; }
+# Run over all splines in response
+    foreach my $label (split(/\,/,$env{"form.HWVAL_AllSplines_$id"})) {
+        my $xiold=-1;
+# Run over all points in spline
+        for (my $i=1; $i<$env{"form.HWVAL_SplineOrder_".$id."_".$label}; $i++) {
+            my $ni=$i+1;
+            my @xparms=($env{'form.HWVAL_'.$id.'_'.$label.'P'.$i.'_x'},
+                        $env{'form.HWVAL_'.$id.'_'.$label.'S'.$i.'_x'},
+                        $env{'form.HWVAL_'.$id.'_'.$label.'P'.$ni.'_x'},
+                        $env{'form.HWVAL_'.$id.'_'.$label.'S'.$ni.'_x'});
+            my @yparms=($env{'form.HWVAL_'.$id.'_'.$label.'P'.$i.'_y'},
+                        $env{'form.HWVAL_'.$id.'_'.$label.'S'.$i.'_y'},
+                        $env{'form.HWVAL_'.$id.'_'.$label.'P'.$ni.'_y'},
+                        $env{'form.HWVAL_'.$id.'_'.$label.'S'.$ni.'_y'});
+# Run in small steps over spline parameter
+            for (my $t=0; $t<=1; $t+=0.00025) {
+                my $xi=&array_index($xmin,$xmax,&cubic_hermite($t,@xparms));
+                if ($xi<$xiold) { return 'no_func'; }
+                if (($xi>$xiold) && ($xi>=0) && ($xi<=200)) {
+                   if (defined($Apache::functionplotresponse::func[$xi])) { return 'no_func'; }
+                   $xiold=$xi;
+                   $Apache::functionplotresponse::func[$xi]=&cubic_hermite($t,@yparms);
+                }
+            }
+        }
+    }
+}
+
+#
+# Implentation of <functionplotresponse>
+#
+
 sub start_functionplotresponse {
   my ($target,$token,$tagstack,$parstack,$parser,$safeeval,$style)=@_;
   my $result='';
-  my $internalid = $Apache::inputtags::part.'_'.&Apache::response::start_response($parstack,$safeeval);
+# To remember the splines - somehow, they need to come last
+  undef %Apache::functionplotresponse::splineorder;
+  undef %Apache::functionplotresponse::splineinitx;
+  undef %Apache::functionplotresponse::splineinity;
+  undef %Apache::functionplotresponse::splinescalex;
+  undef %Apache::functionplotresponse::splinescaley;
+# Remember input fields, etc
+  undef %Apache::functionplotresponse::previous;
+  $Apache::functionplotresponse::inputfields='';
+  $Apache::functionplotresponse::counter=0;
+# Part and ID
+  my $partid=$Apache::inputtags::part;
+  my $id=&Apache::response::start_response($parstack,$safeeval);
+# Internal ID to mark the applet and its coordinates
+  my $internalid = $partid.'_'.$id;
+# Previous answer
+  &decode_previous_answer($Apache::lonhomework::history{"resource.$partid.$id.submission"});
+
+# Parameters of <functionplotresponse>
   my $xmin=&Apache::lonxml::get_param('xmin',$parstack,$safeeval);
+  $xmin=(defined($xmin)?$xmin:-10);
   my $xmax=&Apache::lonxml::get_param('xmax',$parstack,$safeeval);
+  $xmax=(defined($xmax)?$xmax:10);
   my $ymin=&Apache::lonxml::get_param('ymin',$parstack,$safeeval);
+  $ymin=(defined($ymin)?$ymin:-10);
   my $ymax=&Apache::lonxml::get_param('ymax',$parstack,$safeeval);
-  my $xaxisvisible=&Apache::lonxml::get_param('xaxisvisible',$parstack,$safeeval);
-  my $yaxisvisible=&Apache::lonxml::get_param('yaxisvisible',$parstack,$safeeval);
-  my $gridvisible=&Apache::lonxml::get_param('gridvisible',$parstack,$safeeval);
-
-
-  if ($target eq 'web') {
+  $ymax=(defined($ymax)?$ymax:10);
+  my $xaxisvisible=(&Apache::lonxml::get_param('xaxisvisible',$parstack,$safeeval)=~/on|true|yes|1/i?'true':'false');
+  my $yaxisvisible=(&Apache::lonxml::get_param('yaxisvisible',$parstack,$safeeval)=~/on|true|yes|1/i?'true':'false');
+  my $gridvisible=(&Apache::lonxml::get_param('gridvisible',$parstack,$safeeval)=~/on|true|yes|1/i?'true':'false');
+  my $xlabel=&Apache::lonxml::get_param('xlabel',$parstack,$safeeval);
+  my $ylabel=&Apache::lonxml::get_param('ylabel',$parstack,$safeeval);
+  if ($target eq 'edit') {
+    $result.=&Apache::edit::start_table($token)
+       .'<tr><td><span class="LC_nobreak">'.&mt('Function Plot Question').'</span></td>'
+       .'<td><span class="LC_nobreak">'.&mt('Delete?').' '
+       .&Apache::edit::deletelist($target,$token)
+       .'</span></td>'
+       ."<td>&nbsp;"
+       .&Apache::edit::end_row()
+       .&Apache::edit::start_spanning_row()
+       ."\n";
+    $result.=&Apache::edit::text_arg('Label x-axis:','xlabel',
+                                     $token,'6').'&nbsp;'.
+             &Apache::edit::text_arg('Minimum x-value:','xmin',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::text_arg('Maximum x-value:','xmax',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::select_arg('x-axis visible:','xaxisvisible',
+                                  ['yes','no'],$token).'&nbsp;&nbsp;'.
+             &Apache::edit::text_arg('Label y-axis:','ylabel',
+                                     $token,'6').'&nbsp;'.
+             &Apache::edit::text_arg('Minimum y-value:','ymin',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::text_arg('Maximum y-value:','ymax',
+                                     $token,'4').'&nbsp;'.
+             &Apache::edit::select_arg('y-axis visible:','yaxisvisible',
+                                  ['yes','no'],$token).'&nbsp;&nbsp;'.
+             &Apache::edit::select_arg('Grid visible:','gridvisible',
+                                  ['yes','no'],$token).
+             &Apache::edit::end_row().&Apache::edit::start_spanning_row();
+  } elsif ($target eq 'modified') {
+    my $constructtag=&Apache::edit::get_new_args($token,$parstack,
+                                                 $safeeval,'xlabel','xmin','xmax','ylabel','ymin','ymax',
+                                                           'xaxisvisible','yaxisvisible','gridvisible');
+    if ($constructtag) { $result = &Apache::edit::rebuild_tag($token); }
+
+  } elsif ($target eq 'meta') {
+       $result=&Apache::response::meta_package_write('functionplotresponse');
+  } elsif ($target eq 'web') {
+# paste in the update routine to receive stuff back from the applet
+     $result.=&update_script($internalid);
+# start the initscript for this applet
      $result.=&start_init_script($internalid);
+# put the axis commands inside
+     $result.=&axes_script($internalid,$xmin,$xmax,$ymin,$ymax,$xaxisvisible,$yaxisvisible,$gridvisible);
+     $result.=&axes_label($internalid,$xlabel,$ylabel);
+# init script is left open
   }
   return $result;
 }
@@ -139,14 +692,84 @@ sub end_functionplotresponse {
   &Apache::response::end_response;
 
   my $result;
-  my $internalid = $Apache::inputtags::part.'_'.$Apache::inputtags::response[-1];
+  my $id=$Apache::inputtags::response[-1];
+  my $partid=$Apache::inputtags::part;
+  my $internalid = $partid.'_'.$id;
+
+    if ($target eq 'edit') { $result=&Apache::edit::end_table(); }
+    if ($target eq 'grade'
+         && &Apache::response::submitted()
+         && $Apache::lonhomework::type eq 'exam') {
+
+        #&Apache::response::scored_response($partid,$id);
+
+    } elsif ($target eq 'grade'
+         && &Apache::response::submitted()
+         && $Apache::lonhomework::type ne 'exam') {
+        my ($response,%coords)=&get_answer_from_form_fields($internalid);
+        $Apache::lonhomework::results{"resource.$partid.$id.submission"}=$response;
+        my %previous=&Apache::response::check_for_previous($response,$partid,$id);
+#
+# Actually grade
+#
+        my $xmin=&Apache::lonxml::get_param('xmin',$parstack,$safeeval);
+        $xmin=(defined($xmin)?$xmin:-10);
+        my $xmax=&Apache::lonxml::get_param('xmax',$parstack,$safeeval);
+        $xmax=(defined($xmax)?$xmax:10);
+        my $ad;
+        if (&populate_arrays($internalid,$xmin,$xmax) eq 'no_func') {
+           $ad='NOT_FUNCTION';
+        } else {
+           $ad='INCORRECT';
+        }
+        &func_val($xmin,$xmax,3.96);
+
+        &func_val($xmin,$xmax,3.965);
+
+        &func_val($xmin,$xmax,3.97);
+        &func_val($xmin,$xmax,3.975);
+        &func_val($xmin,$xmax,3.98);
+
+        &func_val($xmin,$xmax,3.985);
+        &func_val($xmin,$xmax,3.99);
+        &func_val($xmin,$xmax,3.995);
+
+        &func_val($xmin,$xmax,4);
+        &func_val($xmin,$xmax,4.05);
+        &func_val($xmin,$xmax,4.1);
+
+        &func_val($xmin,$xmax,4.15);
+        &func_val($xmin,$xmax,4.2);
+        &func_val($xmin,$xmax,4.25);
 
-#  if ($target eq 'edit') { $result=&Apache::edit::end_table(); }
-  if ($target eq 'web') {
+#
+# Store grading info
+#
+        $Apache::lonhomework::results{"resource.$partid.$id.awarddetail"}=$ad;
+        &Apache::response::handle_previous(\%previous,$ad);
+   } elsif ($target eq 'web') {
+# Now is the time to render all of the stored splines
+     foreach my $label (keys(%Apache::functionplotresponse::splineorder)) {
+        $result.=&generate_spline($internalid,$label);
+     }
+# close the init script
      $result.=&end_init_script();
+# register all splines in this response 
+     $result.='<input type="hidden" name="HWVAL_AllSplines_'.$internalid.'" value="'.
+                 join(',',keys(%Apache::functionplotresponse::splineorder)).'" />'."\n";
+     foreach my $label (keys(%Apache::functionplotresponse::splineorder)) {
+        $result.='<input type="hidden" name="HWVAL_SplineOrder_'.$internalid.'_'.$label.'" value="'.
+                 $Apache::functionplotresponse::splineorder{$label}.'" />'."\n";
+     }
+# generate the input fields
+     $result.=$Apache::functionplotresponse::inputfields;
+# actually start the <applet>-tag
      $result.=&geogebra_startcode($internalid);
+# load the spline bytecode
      $result.=&geogebra_spline_program();
+# set default parameters
      $result.=&geogebra_default_parameters($internalid);
+# close the <applet>-tag
      $result.=&geogebra_endcode();
   }
   return $result;