31 files changed, 720 insertions, 139 deletions
diff --git a/src/CGALEvaluator.cc b/src/CGALEvaluator.cc
index 20c5d5e..60d98b8 100644
--- a/src/CGALEvaluator.cc
+++ b/src/CGALEvaluator.cc
@@ -61,6 +61,11 @@ void CGALEvaluator::process(CGAL_Nef_polyhedron &target, const CGAL_Nef_polyhedr
  	if (target.dim != 2 && target.dim != 3) {
  		assert(false && "Dimension of Nef polyhedron must be 2 or 3");
  	}
+    // Intersecting something with nothing results in nothing
+	if (src.isEmpty() && op == CGE_INTERSECTION) {
+        target = src;
+        return;
+    }
 	if (src.isEmpty()) return; // Empty polyhedron. This can happen for e.g. square([0,0])
 	if (target.isEmpty() && op != CGE_UNION) return; // empty op <something> => empty
 	if (target.dim != src.dim) return; // If someone tries to e.g. union 2d and 3d objects
@@ -708,7 +713,7 @@ CGAL_Nef_polyhedron CGALEvaluator::evaluateCGALMesh(const PolySet &ps)
 			PRINTB("Alternate construction failed. CGAL error in CGAL_Nef_polyhedron3(): %s", e.what());
 		}
 		CGAL::set_error_behaviour(old_behaviour);
-		return CGAL_Nef_polyhedron(N);
+		if (N) return CGAL_Nef_polyhedron(N);
 	}
-	return CGAL_Nef_polyhedron();
+	return CGAL_Nef_polyhedron(ps.is2d?2:3);
 }
diff --git a/src/CSGTermEvaluator.cc b/src/CSGTermEvaluator.cc
index 647a3dc..56f7b3a 100644
--- a/src/CSGTermEvaluator.cc
+++ b/src/CSGTermEvaluator.cc
@@ -108,7 +108,7 @@ static shared_ptr<CSGTerm> evaluate_csg_term_from_ps(const State &state,
 
 Response CSGTermEvaluator::visit(State &state, const AbstractPolyNode &node)
 {
-	if (state.isPrefix()) {
+	if (state.isPostfix()) {
 		shared_ptr<CSGTerm> t1;
 		if (this->psevaluator) {
 			shared_ptr<PolySet> ps = this->psevaluator->getPolySet(node, true);
@@ -121,7 +121,7 @@ Response CSGTermEvaluator::visit(State &state, const AbstractPolyNode &node)
 		this->stored_term[node.index()] = t1;
 		addToParent(state, node);
 	}
-	return PruneTraversal;
+	return ContinueTraversal;
 }
 
 Response CSGTermEvaluator::visit(State &state, const CsgNode &node)
@@ -174,7 +174,7 @@ Response CSGTermEvaluator::visit(State &state, const ColorNode &node)
 // FIXME: If we've got CGAL support, render this node as a CGAL union into a PolySet
 Response CSGTermEvaluator::visit(State &state, const RenderNode &node)
 {
-	if (state.isPrefix()) {
+	if (state.isPostfix()) {
 		shared_ptr<CSGTerm> t1;
 		shared_ptr<PolySet> ps;
 		if (this->psevaluator) {
@@ -188,12 +188,12 @@ Response CSGTermEvaluator::visit(State &state, const RenderNode &node)
 		this->stored_term[node.index()] = t1;
 		addToParent(state, node);
 	}
-	return PruneTraversal;
+	return ContinueTraversal;
 }
 
 Response CSGTermEvaluator::visit(State &state, const CgaladvNode &node)
 {
-	if (state.isPrefix()) {
+	if (state.isPostfix()) {
 		shared_ptr<CSGTerm> t1;
     // FIXME: Calling evaluator directly since we're not a PolyNode. Generalize this.
 		shared_ptr<PolySet> ps;
@@ -208,7 +208,7 @@ Response CSGTermEvaluator::visit(State &state, const CgaladvNode &node)
 		this->stored_term[node.index()] = t1;
 		addToParent(state, node);
 	}
-	return PruneTraversal;
+	return ContinueTraversal;
 }
 
 /*!
diff --git a/src/MainWindow.h b/src/MainWindow.h
index ac999bf..4948d46 100644
--- a/src/MainWindow.h
+++ b/src/MainWindow.h
@@ -70,6 +70,7 @@ private slots:
 	void updateTVal();
 	void setFileName(const QString &filename);
 	void setFont(const QString &family, uint size);
+	void setSyntaxHighlight(const QString &s);
 	void showProgress();
 	void openCSGSettingsChanged();
 
diff --git a/src/PlatformUtils-posix.cc b/src/PlatformUtils-posix.cc
index d7b7b6d..d2b8792 100644
--- a/src/PlatformUtils-posix.cc
+++ b/src/PlatformUtils-posix.cc
@@ -3,8 +3,13 @@
 
 std::string PlatformUtils::documentsPath()
 {
-	fs::path docpath(getenv("HOME"));
-	docpath = docpath / ".local" / "share";
-
-	return boosty::stringy(docpath);
+	const char *home = getenv("HOME");
+	if (home) {
+		fs::path docpath(home);
+		docpath = docpath / ".local" / "share";
+		return boosty::stringy(docpath);
+	}
+	else {
+		return "";
+	}
 }
diff --git a/src/PolySetCGALEvaluator.cc b/src/PolySetCGALEvaluator.cc
index a2d896d..0b57de1 100644
--- a/src/PolySetCGALEvaluator.cc
+++ b/src/PolySetCGALEvaluator.cc
@@ -13,10 +13,10 @@
 #include "dxfdata.h"
 #include "dxftess.h"
 #include "module.h"
+#include "calc.h"
 
 #include "svg.h"
 #include "printutils.h"
-#include "openscad.h" // get_fragments_from_r()
 #include <boost/foreach.hpp>
 #include <vector>
 
@@ -469,7 +469,7 @@ PolySet *PolySetCGALEvaluator::rotateDxfData(const RotateExtrudeNode &node, DxfD
 			}
 		}
 
-		int fragments = get_fragments_from_r(max_x-min_x, node.fn, node.fs, node.fa);
+		int fragments = Calc::get_fragments_from_r(max_x-min_x, node.fn, node.fs, node.fa);
 
 		double ***points;
 		points = new double**[fragments];
diff --git a/src/Preferences.cc b/src/Preferences.cc
index 0f3115e..92f11c7 100644
--- a/src/Preferences.cc
+++ b/src/Preferences.cc
@@ -33,12 +33,16 @@
 #include <QStatusBar>
 #include "PolySetCache.h"
 #include "AutoUpdater.h"
+#include "feature.h"
 #ifdef ENABLE_CGAL
 #include "CGALCache.h"
 #endif
 
 Preferences *Preferences::instance = NULL;
 
+const char * Preferences::featurePropertyName = "FeatureProperty";
+Q_DECLARE_METATYPE(Feature *);
+
 Preferences::Preferences(QWidget *parent) : QMainWindow(parent)
 {
 	setupUi(this);
@@ -59,6 +63,7 @@ Preferences::Preferences(QWidget *parent) : QMainWindow(parent)
 	QString found_family(QFontInfo(font).family());
 	this->defaultmap["editor/fontfamily"] = found_family;
  	this->defaultmap["editor/fontsize"] = 12;
+	this->defaultmap["editor/syntaxhighlight"] = "For Light Background";
 
 	uint savedsize = getValue("editor/fontsize").toUInt();
 	QFontDatabase db;
@@ -86,13 +91,13 @@ Preferences::Preferences(QWidget *parent) : QMainWindow(parent)
 	this->defaultmap["advanced/openCSGLimit"] = RenderSettings::inst()->openCSGTermLimit;
 	this->defaultmap["advanced/forceGoldfeather"] = false;
 
-
 	// Toolbar
 	QActionGroup *group = new QActionGroup(this);
-	group->addAction(prefsAction3DView);
-	group->addAction(prefsActionEditor);
-	group->addAction(prefsActionUpdate);
-	group->addAction(prefsActionAdvanced);
+	addPrefPage(group, prefsAction3DView, page3DView);
+	addPrefPage(group, prefsActionEditor, pageEditor);
+	addPrefPage(group, prefsActionUpdate, pageUpdate);
+	addPrefPage(group, prefsActionFeatures, pageFeatures);
+	addPrefPage(group, prefsActionAdvanced, pageAdvanced);
 	connect(group, SIGNAL(triggered(QAction*)), this, SLOT(actionTriggered(QAction*)));
 
 	prefsAction3DView->setChecked(true);
@@ -140,6 +145,7 @@ Preferences::Preferences(QWidget *parent) : QMainWindow(parent)
 	this->polysetCacheSizeEdit->setValidator(validator);
 	this->opencsgLimitEdit->setValidator(validator);
 
+	setupFeaturesPage();
 	updateGUI();
 
 	RenderSettings::inst()->setColors(this->colorschemes[getValue("3dview/colorscheme").toString()]);
@@ -150,21 +156,102 @@ Preferences::~Preferences()
 	removeDefaultSettings();
 }
 
+/**
+ * Add a page for the preferences GUI. This handles both the action grouping
+ * and the registration of the widget for each action to have a generalized
+ * callback to switch pages.
+ * 
+ * @param group The action group for all page actions. This one will have the
+ *              callback attached after creating all actions/pages.
+ * @param action The action specific for the added page.
+ * @param widget The widget that should be shown when the action is triggered.
+ *               This must be a child page of the stackedWidget.
+ */
+void
+Preferences::addPrefPage(QActionGroup *group, QAction *action, QWidget *widget)
+{
+	group->addAction(action);
+	prefPages[action] = widget;
+}
+
+/**
+ * Callback to switch pages in the preferences GUI.
+ * 
+ * @param action The action triggered by the user.
+ */
 void
 Preferences::actionTriggered(QAction *action)
 {
-	if (action == this->prefsAction3DView) {
-		this->stackedWidget->setCurrentWidget(this->page3DView);
-	}
-	else if (action == this->prefsActionEditor) {
-		this->stackedWidget->setCurrentWidget(this->pageEditor);
+	this->stackedWidget->setCurrentWidget(prefPages[action]);
+}
+
+/**
+ * Callback for the dynamically created checkboxes on the features
+ * page. The specific Feature object is associated as property with
+ * the callback.
+ * 
+ * @param state the state of the checkbox.
+ */
+void Preferences::featuresCheckBoxToggled(bool state)
+{
+	const QObject *sender = QObject::sender();
+	if (sender == NULL) {
+		return;
 	}
-	else if (action == this->prefsActionUpdate) {
-		this->stackedWidget->setCurrentWidget(this->pageUpdate);
+	QVariant v = sender->property(featurePropertyName);
+	if (!v.isValid()) {
+		return;
 	}
-	else if (action == this->prefsActionAdvanced) {
-		this->stackedWidget->setCurrentWidget(this->pageAdvanced);
+	Feature *feature = v.value<Feature *>();
+	feature->enable(state);
+	QSettings settings;
+	settings.setValue(QString("feature/%1").arg(QString::fromStdString(feature->get_name())), state);
+}
+
+/**
+ * Setup feature GUI and synchronize the Qt settings with the feature values.
+ * 
+ * When running in GUI mode, the feature setting that might have been set
+ * from commandline is ignored. This always uses the value coming from the
+ * QSettings.
+ */
+void
+Preferences::setupFeaturesPage()
+{
+	int row = 0;
+	for (Feature::iterator it = Feature::begin();it != Feature::end();it++) {
+		Feature *feature = *it;
+		
+		QString featurekey = QString("feature/%1").arg(QString::fromStdString(feature->get_name()));
+		this->defaultmap[featurekey] = false;
+
+		// spacer item between the features, just for some optical separation
+		gridLayoutExperimentalFeatures->addItem(new QSpacerItem(1, 8, QSizePolicy::Expanding, QSizePolicy::Fixed), row, 1, 1, 1, Qt::AlignCenter);
+		row++;
+
+		QCheckBox *cb = new QCheckBox(QString::fromStdString(feature->get_name()), pageFeatures);
+		QFont bold_font(cb->font());
+		bold_font.setBold(true);
+		cb->setFont(bold_font);
+		// synchronize Qt settings with the feature settings
+		bool value = getValue(featurekey).toBool();
+		feature->enable(value);
+		cb->setChecked(value);
+		cb->setProperty(featurePropertyName, QVariant::fromValue<Feature *>(feature));
+		connect(cb, SIGNAL(toggled(bool)), this, SLOT(featuresCheckBoxToggled(bool)));		
+		gridLayoutExperimentalFeatures->addWidget(cb, row, 0, 1, 2, Qt::AlignLeading);
+		row++;
+		
+		QLabel *l = new QLabel(QString::fromStdString(feature->get_description()), pageFeatures);
+		l->setTextFormat(Qt::RichText);
+		gridLayoutExperimentalFeatures->addWidget(l, row, 1, 1, 1, Qt::AlignLeading);
+		row++;
 	}
+	// Force fixed indentation, the checkboxes use column span of 2 so 
+	// first row is not constrained in size by the visible controls. The
+	// fixed size space essentially gives the first row the width of the
+	// spacer item itself.
+	gridLayoutExperimentalFeatures->addItem(new QSpacerItem(20, 0, QSizePolicy::Fixed, QSizePolicy::Fixed), 1, 0, 1, 1, Qt::AlignLeading);
 }
 
 void Preferences::on_colorSchemeChooser_itemSelectionChanged()
@@ -193,6 +280,13 @@ void Preferences::on_fontSize_editTextChanged(const QString &size)
 	emit fontChanged(getValue("editor/fontfamily").toString(), intsize);
 }
 
+void Preferences::on_syntaxHighlight_currentIndexChanged(const QString &s)
+{
+	QSettings settings;
+	settings.setValue("editor/syntaxhighlight", s);
+	emit syntaxHighlightChanged(s);
+}
+
 void unimplemented_msg()
 {
   QMessageBox mbox;
@@ -309,7 +403,6 @@ QVariant Preferences::getValue(const QString &key) const
 
 void Preferences::updateGUI()
 {
-	QSettings settings;
 	QList<QListWidgetItem *> found = 
 		this->colorSchemeChooser->findItems(getValue("3dview/colorscheme").toString(),
 																				Qt::MatchExactly);
@@ -330,6 +423,10 @@ void Preferences::updateGUI()
 		this->fontSize->setEditText(fontsize);
 	}
 
+	QString shighlight = getValue("editor/syntaxhighlight").toString();
+	int shidx = this->syntaxHighlight->findText(shighlight);
+	if (shidx >= 0) this->syntaxHighlight->setCurrentIndex(shidx);
+
 	if (AutoUpdater *updater = AutoUpdater::updater()) {
 		this->updateCheckBox->setChecked(updater->automaticallyChecksForUpdates());
 		this->snapshotCheckBox->setChecked(updater->enableSnapshots());
diff --git a/src/Preferences.h b/src/Preferences.h
index 4656793..d74ada9 100644
--- a/src/Preferences.h
+++ b/src/Preferences.h
@@ -21,9 +21,11 @@ public:
 
 public slots:
 	void actionTriggered(class QAction *);
+	void featuresCheckBoxToggled(bool);
 	void on_colorSchemeChooser_itemSelectionChanged();
 	void on_fontChooser_activated(const QString &);
 	void on_fontSize_editTextChanged(const QString &);
+	void on_syntaxHighlight_currentIndexChanged(const QString &);
 	void on_openCSGWarningBox_toggled(bool);
 	void on_enableOpenCSGBox_toggled(bool);
 	void on_cgalCacheSizeEdit_textChanged(const QString &);
@@ -38,17 +40,22 @@ signals:
 	void requestRedraw() const;
 	void fontChanged(const QString &family, uint size) const;
 	void openCSGSettingsChanged() const;
+	void syntaxHighlightChanged(const QString &s);
 
 private:
 	Preferences(QWidget *parent = NULL);
 	void keyPressEvent(QKeyEvent *e);
 	void updateGUI();
 	void removeDefaultSettings();
+	void setupFeaturesPage();
+	void addPrefPage(QActionGroup *group, QAction *action, QWidget *widget);
 
 	QSettings::SettingsMap defaultmap;
 	QHash<QString, std::map<RenderSettings::RenderColor, Color4f> > colorschemes;
+	QHash<const QAction *, QWidget *> prefPages;
 
 	static Preferences *instance;
+	static const char *featurePropertyName;
 };
 
 #endif
diff --git a/src/Preferences.ui b/src/Preferences.ui
index d67db6a..100bcb1 100644
--- a/src/Preferences.ui
+++ b/src/Preferences.ui
@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>473</width>
-    <height>320</height>
+    <width>823</width>
+    <height>433</height>
    </rect>
   </property>
   <property name="sizePolicy">
@@ -27,7 +27,7 @@
     <item>
      <widget class="QStackedWidget" name="stackedWidget">
       <property name="currentIndex">
-       <number>2</number>
+       <number>1</number>
       </property>
       <widget class="QWidget" name="page3DView">
        <layout class="QVBoxLayout" name="verticalLayout_4">
@@ -136,7 +136,7 @@
            <widget class="QFontComboBox" name="fontChooser">
             <property name="currentFont">
              <font>
-              <family>Monaco</family>
+              <family>DejaVu Sans</family>
               <pointsize>12</pointsize>
              </font>
             </property>
@@ -165,6 +165,61 @@
          </layout>
         </item>
         <item>
+         <layout class="QHBoxLayout" name="horizontalLayout_5">
+          <property name="bottomMargin">
+           <number>0</number>
+          </property>
+          <item>
+           <widget class="QLabel" name="label_9">
+            <property name="font">
+             <font>
+              <weight>75</weight>
+              <bold>true</bold>
+             </font>
+            </property>
+            <property name="text">
+             <string>Color syntax highlighting</string>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <spacer name="horizontalSpacer_3">
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+            <property name="sizeType">
+             <enum>QSizePolicy::Maximum</enum>
+            </property>
+            <property name="sizeHint" stdset="0">
+             <size>
+              <width>30</width>
+              <height>20</height>
+             </size>
+            </property>
+           </spacer>
+          </item>
+          <item>
+           <widget class="QComboBox" name="syntaxHighlight">
+            <item>
+             <property name="text">
+              <string>For Light Background</string>
+             </property>
+            </item>
+            <item>
+             <property name="text">
+              <string>For Dark Background</string>
+             </property>
+            </item>
+            <item>
+             <property name="text">
+              <string>Off</string>
+             </property>
+            </item>
+           </widget>
+          </item>
+         </layout>
+        </item>
+        <item>
          <spacer name="verticalSpacer_4">
           <property name="orientation">
            <enum>Qt::Vertical</enum>
@@ -323,6 +378,78 @@
         </item>
        </layout>
       </widget>
+      <widget class="QWidget" name="pageFeatures">
+       <layout class="QGridLayout" name="gridLayout_2">
+        <property name="margin">
+         <number>0</number>
+        </property>
+        <item row="0" column="0">
+         <layout class="QVBoxLayout" name="verticalLayout_9">
+          <item>
+           <widget class="QLabel" name="label_9">
+            <property name="font">
+             <font>
+              <weight>75</weight>
+              <bold>true</bold>
+             </font>
+            </property>
+            <property name="text">
+             <string>Features</string>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <widget class="QScrollArea" name="scrollArea">
+            <property name="frameShape">
+             <enum>QFrame::NoFrame</enum>
+            </property>
+            <property name="frameShadow">
+             <enum>QFrame::Plain</enum>
+            </property>
+            <property name="horizontalScrollBarPolicy">
+             <enum>Qt::ScrollBarAlwaysOff</enum>
+            </property>
+            <property name="widgetResizable">
+             <bool>true</bool>
+            </property>
+            <widget class="QWidget" name="scrollAreaWidgetContents">
+             <property name="geometry">
+              <rect>
+               <x>0</x>
+               <y>0</y>
+               <width>803</width>
+               <height>311</height>
+              </rect>
+             </property>
+             <layout class="QVBoxLayout" name="verticalLayout_10">
+              <item>
+               <layout class="QGridLayout" name="gridLayoutExperimentalFeatures" rowminimumheight="0">
+                <property name="spacing">
+                 <number>8</number>
+                </property>
+               </layout>
+              </item>
+              <item>
+               <spacer name="verticalSpacer_3">
+                <property name="orientation">
+                 <enum>Qt::Vertical</enum>
+                </property>
+                <property name="sizeHint" stdset="0">
+                 <size>
+                  <width>20</width>
+                  <height>282</height>
+                 </size>
+                </property>
+               </spacer>
+              </item>
+             </layout>
+            </widget>
+           </widget>
+          </item>
+         </layout>
+        </item>
+       </layout>
+      </widget>
       <widget class="QWidget" name="pageAdvanced">
        <layout class="QVBoxLayout" name="verticalLayout_3">
         <item>
@@ -465,6 +592,7 @@
    <addaction name="prefsAction3DView"/>
    <addaction name="prefsActionEditor"/>
    <addaction name="prefsActionUpdate"/>
+   <addaction name="prefsActionFeatures"/>
    <addaction name="prefsActionAdvanced"/>
   </widget>
   <action name="prefsAction3DView">
@@ -515,6 +643,21 @@
     <string>Update</string>
    </property>
   </action>
+  <action name="prefsActionFeatures">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="../openscad.qrc">
+     <normaloff>:/icons/prefsFeatures.png</normaloff>:/icons/prefsFeatures.png</iconset>
+   </property>
+   <property name="text">
+    <string>Features</string>
+   </property>
+   <property name="toolTip">
+    <string>Enable/Disable experimental features</string>
+   </property>
+  </action>
  </widget>
  <resources>
   <include location="../openscad.qrc"/>
diff --git a/src/calc.cc b/src/calc.cc
new file mode 100644
index 0000000..bdae085
--- /dev/null
+++ b/src/calc.cc
@@ -0,0 +1,40 @@
+/*
+ *  OpenSCAD (www.openscad.org)
+ *  Copyright (C) 2009-2011 Clifford Wolf <clifford@clifford.at> and
+ *                          Marius Kintel <marius@kintel.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  As a special exception, you have permission to link this program
+ *  with the CGAL library and distribute executables, as long as you
+ *  follow the requirements of the GNU GPL in regard to all of the
+ *  software in the executable aside from CGAL.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+
+#include "calc.h"
+#include "grid.h"
+
+/*!
+	Returns the number of subdivision of a whole circle, given radius and
+	the three special variables $fn, $fs and $fa
+*/
+int Calc::get_fragments_from_r(double r, double fn, double fs, double fa)
+{
+	if (r < GRID_FINE) return 3;
+	if (fn > 0.0) return (int)(fn >= 3 ? fn : 3);
+	return (int)ceil(fmax(fmin(360.0 / fa, r*2*M_PI / fs), 5));
+}
+
diff --git a/src/calc.h b/src/calc.h
new file mode 100644
index 0000000..1ac9e17
--- /dev/null
+++ b/src/calc.h
@@ -0,0 +1,8 @@
+#ifndef CALC_H_
+#define CALC_H_
+
+namespace Calc {
+	int get_fragments_from_r(double r, double fn, double fs, double fa);
+}
+
+#endif
diff --git a/src/csgtermnormalizer.cc b/src/csgtermnormalizer.cc
index 461e965..2f79841 100644
--- a/src/csgtermnormalizer.cc
+++ b/src/csgtermnormalizer.cc
@@ -32,6 +32,22 @@ shared_ptr<CSGTerm> CSGTermNormalizer::normalize(const shared_ptr<CSGTerm> &root
 	return temp;
 }
 
+/*!
+	After aborting, a subtree might have become invalidated (NULL child term)
+	since terms can be instantiated multiple times.
+	This will search for NULL children an recursively repair the corresponding
+	subtree.
+ */
+shared_ptr<CSGTerm> CSGTermNormalizer::cleanup_term(shared_ptr<CSGTerm> &t)
+{
+	if (t->type != CSGTerm::TYPE_PRIMITIVE) {
+		if (t->left) t->left = cleanup_term(t->left);
+		if (t->right) t->right = cleanup_term(t->right);
+		return collapse_null_terms(t);
+	}
+	else return t;
+}
+
 shared_ptr<CSGTerm> CSGTermNormalizer::normalizePass(shared_ptr<CSGTerm> term)
 {
 	// This function implements the CSG normalization
@@ -62,7 +78,13 @@ shared_ptr<CSGTerm> CSGTermNormalizer::normalizePass(shared_ptr<CSGTerm> term)
 	if (!this->aborted) term->right = normalizePass(term->right);
 
 	// FIXME: Do we need to take into account any transformation of item here?
-	return collapse_null_terms(term);
+	shared_ptr<CSGTerm> t = collapse_null_terms(term);
+
+	if (this->aborted) {
+		if (t) t = cleanup_term(t);
+	}
+
+	return t;
 }
 
 shared_ptr<CSGTerm> CSGTermNormalizer::collapse_null_terms(const shared_ptr<CSGTerm> &term)
diff --git a/src/csgtermnormalizer.h b/src/csgtermnormalizer.h
index f7a444f..bb55141 100644
--- a/src/csgtermnormalizer.h
+++ b/src/csgtermnormalizer.h
@@ -15,6 +15,7 @@ private:
 	shared_ptr<CSGTerm> normalizePass(shared_ptr<CSGTerm> term) ;
 	bool match_and_replace(shared_ptr<CSGTerm> &term);
 	shared_ptr<CSGTerm> collapse_null_terms(const shared_ptr<CSGTerm> &term);
+	shared_ptr<CSGTerm> cleanup_term(shared_ptr<CSGTerm> &t);
 	unsigned int count(const shared_ptr<CSGTerm> &term) const;
 
 	bool aborted;
diff --git a/src/dxfdata.cc b/src/dxfdata.cc
index 8415228..ffea169 100644
--- a/src/dxfdata.cc
+++ b/src/dxfdata.cc
@@ -28,7 +28,7 @@
 #include "grid.h"
 #include "printutils.h"
 #include "handle_dep.h"
-#include "openscad.h" // get_fragments_from_r()
+#include "calc.h"
 
 #include <fstream>
 #include "mathc99.h"
@@ -175,22 +175,23 @@ DxfData::DxfData(double fn, double fs, double fa,
 				in_blocks_section = iddata == "BLOCKS";
 			}
 			else if (mode == "LINE") {
-				ADD_LINE(xverts[0], yverts[0], xverts[1], yverts[1]);
+				ADD_LINE(xverts.at(0), yverts.at(0), xverts.at(1), yverts.at(1));
 			}
 			else if (mode == "LWPOLYLINE") {
-				assert(xverts.size() == yverts.size());
-				// polyline flag is stored in 'dimtype'
-				int numverts = xverts.size();
+				// assert(xverts.size() == yverts.size());
+				// Get maximum to enforce managed exception if xverts.size() != yverts.size()
+				int numverts = std::max(xverts.size(), yverts.size());
 				for (int i=1;i<numverts;i++) {
-					ADD_LINE(xverts[i-1], yverts[i-1], xverts[i%numverts], yverts[i%numverts]);
+					ADD_LINE(xverts.at(i-1), yverts.at(i-1), xverts.at(i%numverts), yverts.at(i%numverts));
 				}
+				// polyline flag is stored in 'dimtype'
 				if (dimtype & 0x01) { // closed polyline
-					ADD_LINE(xverts[numverts-1], yverts[numverts-1], xverts[0], yverts[0]);
+					ADD_LINE(xverts.at(numverts-1), yverts.at(numverts-1), xverts.at(0), yverts.at(0));
 				}
 			}
 			else if (mode == "CIRCLE") {
-				int n = get_fragments_from_r(radius, fn, fs, fa);
-				Vector2d center(xverts[0], yverts[0]);
+				int n = Calc::get_fragments_from_r(radius, fn, fs, fa);
+				Vector2d center(xverts.at(0), yverts.at(0));
 				for (int i = 0; i < n; i++) {
 					double a1 = (2*M_PI*i)/n;
 					double a2 = (2*M_PI*(i+1))/n;
@@ -199,8 +200,8 @@ DxfData::DxfData(double fn, double fs, double fa,
 				}
 			}
 			else if (mode == "ARC") {
-				Vector2d center(xverts[0], yverts[0]);
-				int n = get_fragments_from_r(radius, fn, fs, fa);
+				Vector2d center(xverts.at(0), yverts.at(0));
+				int n = Calc::get_fragments_from_r(radius, fn, fs, fa);
 				while (arc_start_angle > arc_stop_angle)
 					arc_stop_angle += 360.0;
 				n = (int)ceil(n * (arc_stop_angle-arc_start_angle) / 360);
@@ -217,9 +218,9 @@ DxfData::DxfData(double fn, double fs, double fa,
 				// Commented code is meant as documentation of vector math
 				while (ellipse_start_angle > ellipse_stop_angle) ellipse_stop_angle += 2 * M_PI;
 //				Vector2d center(xverts[0], yverts[0]);
-				Vector2d center(xverts[0], yverts[0]);
+				Vector2d center(xverts.at(0), yverts.at(0));
 //				Vector2d ce(xverts[1], yverts[1]);
-				Vector2d ce(xverts[1], yverts[1]);
+				Vector2d ce(xverts.at(1), yverts.at(1));
 //				double r_major = ce.length();
 				double r_major = sqrt(ce[0]*ce[0] + ce[1]*ce[1]);
 //				double rot_angle = ce.angle();
@@ -237,7 +238,7 @@ DxfData::DxfData(double fn, double fs, double fa,
 				// the ratio stored in 'radius; due to the parser code not checking entity type
 				double r_minor = r_major * radius;
 				double sweep_angle = ellipse_stop_angle-ellipse_start_angle;
-				int n = get_fragments_from_r(r_major, fn, fs, fa);
+				int n = Calc::get_fragments_from_r(r_major, fn, fs, fa);
 				n = (int)ceil(n * sweep_angle / (2 * M_PI));
 //				Vector2d p1;
 				Vector2d p1; p1 << 0,0;
@@ -270,10 +271,10 @@ DxfData::DxfData(double fn, double fs, double fa,
 					double ly1 = this->points[blockdata[iddata][i].idx[0]][1] * ellipse_stop_angle;
 					double lx2 = this->points[blockdata[iddata][i].idx[1]][0] * ellipse_start_angle;
 					double ly2 = this->points[blockdata[iddata][i].idx[1]][1] * ellipse_stop_angle;
-					double px1 = (cos(a)*lx1 - sin(a)*ly1) * scale + xverts[0];
-					double py1 = (sin(a)*lx1 + cos(a)*ly1) * scale + yverts[0];
-					double px2 = (cos(a)*lx2 - sin(a)*ly2) * scale + xverts[0];
-					double py2 = (sin(a)*lx2 + cos(a)*ly2) * scale + yverts[0];
+					double px1 = (cos(a)*lx1 - sin(a)*ly1) * scale + xverts.at(0);
+					double py1 = (sin(a)*lx1 + cos(a)*ly1) * scale + yverts.at(0);
+					double px2 = (cos(a)*lx2 - sin(a)*ly2) * scale + xverts.at(0);
+					double py2 = (sin(a)*lx2 + cos(a)*ly2) * scale + yverts.at(0);
 					ADD_LINE(px1, py1, px2, py2);
 				}
 			}
@@ -385,6 +386,9 @@ DxfData::DxfData(double fn, double fs, double fa,
     catch (boost::bad_lexical_cast &blc) {
 	  	PRINTB("WARNING: Illegal value %s in '%s'", data % filename);
   	}
+    catch (const std::out_of_range& oor) {
+	  	PRINTB("WARNING: not enough input values for %s in '%s'", data % filename);
+  	}
 	}
 
 	BOOST_FOREACH(const EntityList::value_type &i, unsupported_entities_list) {
diff --git a/src/evalcontext.cc b/src/evalcontext.cc
index 57c206f..7752451 100644
--- a/src/evalcontext.cc
+++ b/src/evalcontext.cc
@@ -41,7 +41,7 @@ void EvalContext::dump(const AbstractModule *mod, const ModuleInstantiation *ins
 	PRINTB("  document path: %s", this->document_path);
 
 	PRINT("  eval args:");
-	for (int i=0;i<this->eval_arguments.size();i++) {
+	for (size_t i=0;i<this->eval_arguments.size();i++) {
 		PRINTB("    %s = %s", this->eval_arguments[i].first % this->eval_arguments[i].second);
 	}
 	if (this->scope && this->scope->children.size() > 0) {
diff --git a/src/feature.cc b/src/feature.cc
new file mode 100644
index 0000000..80d7887
--- /dev/null
+++ b/src/feature.cc
@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <iostream>
+#include <string>
+#include <map>
+
+#include "feature.h"
+#include "printutils.h"
+
+/**
+ * Feature registration map/list for later lookup. This must be initialized
+ * before the static feature instances as those register with this map. 
+ */
+Feature::map_t Feature::feature_map;
+Feature::list_t Feature::feature_list;
+
+/*
+ * List of features, the names given here are used in both command line
+ * argument to enable the option and for saving the option value in GUI
+ * context.
+ */
+const Feature Feature::ExperimentalConcatFunction("concat", "Enable the <code>concat()</code> function.");
+
+Feature::Feature(const std::string &name, const std::string &description)
+	: enabled(false), name(name), description(description)
+{
+	feature_map[name] = this;
+	feature_list.push_back(this);
+}
+
+Feature::~Feature()
+{
+}
+
+const std::string &Feature::get_name() const
+{
+	return name;
+}
+    
+const std::string &Feature::get_description() const
+{
+	return description;
+}
+    
+bool Feature::is_enabled() const
+{
+	return enabled;
+}
+
+void Feature::enable(bool status)
+{
+	enabled = status;
+}
+    
+void Feature::enable_feature(const std::string &feature_name, bool status)
+{
+	map_t::iterator it = feature_map.find(feature_name);
+	if (it != feature_map.end()) {
+		it->second->enable(status);
+	} else {
+		PRINTB("WARNING: Ignoring request to enable unknown feature '%s'.", feature_name);
+	}
+}
+
+Feature::iterator Feature::begin()
+{	
+	return feature_list.begin();
+}
+
+Feature::iterator Feature::end()
+{
+	return feature_list.end();
+}
+
+void Feature::dump_features()
+{
+	for (map_t::iterator it = feature_map.begin(); it != feature_map.end(); it++) {
+		std::cout << "Feature('" << it->first << "') = " << (it->second->is_enabled() ? "enabled" : "disabled") << std::endl;
+	}
+}
diff --git a/src/feature.h b/src/feature.h
new file mode 100644
index 0000000..20b4f16
--- /dev/null
+++ b/src/feature.h
@@ -0,0 +1,44 @@
+#ifndef FEATURE_H_
+#define FEATURE_H_
+
+#include <stdio.h>
+#include <iostream>
+#include <string>
+#include <map>
+#include <vector>
+
+class Feature
+{
+public:
+	typedef std::vector<Feature *> list_t;
+	typedef list_t::iterator iterator;
+
+	static const Feature ExperimentalConcatFunction;
+    
+	const std::string& get_name() const;
+	const std::string& get_description() const;
+    
+	bool is_enabled() const;
+	void enable(bool status);
+
+	static iterator begin();
+	static iterator end();
+    
+	static void dump_features();
+	static void enable_feature(const std::string &feature_name, bool status = true);
+
+private:
+	bool enabled;
+  
+	const std::string name;
+	const std::string description;
+    
+	typedef std::map<std::string, Feature *> map_t;
+	static map_t feature_map;
+	static list_t feature_list;
+    
+	Feature(const std::string &name, const std::string &description);
+	virtual ~Feature();
+};
+
+#endif
diff --git a/src/func.cc b/src/func.cc
index 4587f72..878bc1c 100644
--- a/src/func.cc
+++ b/src/func.cc
@@ -343,6 +343,24 @@ Value builtin_str(const Context *, const EvalContext *evalctx)
 	return Value(stream.str());
 }
 
+Value builtin_concat(const Context *, const EvalContext *evalctx)
+{
+	Value::VectorType result;
+
+	for (size_t i = 0; i < evalctx->numArgs(); i++) {
+		const Value v = evalctx->getArgValue(i);
+		if (v.type() == Value::VECTOR) {
+			Value::VectorType vec = v.toVector();
+			for (Value::VectorType::const_iterator it = vec.begin(); it != vec.end(); it++) {
+				result.push_back(*it);
+			}
+		} else {
+			result.push_back(v);
+		}
+	}
+	return Value(result);
+}
+
 Value builtin_lookup(const Context *, const EvalContext *evalctx)
 {
 	double p, low_p, low_v, high_p, high_v;
@@ -604,6 +622,7 @@ void register_builtin_functions()
 	Builtins::init("log", new BuiltinFunction(&builtin_log));
 	Builtins::init("ln", new BuiltinFunction(&builtin_ln));
 	Builtins::init("str", new BuiltinFunction(&builtin_str));
+	Builtins::init("concat", new BuiltinFunction(&builtin_concat, Feature::ExperimentalConcatFunction));
 	Builtins::init("lookup", new BuiltinFunction(&builtin_lookup));
 	Builtins::init("search", new BuiltinFunction(&builtin_search));
 	Builtins::init("version", new BuiltinFunction(&builtin_version));
diff --git a/src/function.h b/src/function.h
index a1fde3c..2491809 100644
--- a/src/function.h
+++ b/src/function.h
@@ -3,13 +3,21 @@
 
 #include "value.h"
 #include "typedefs.h"
+#include "feature.h"
+
 #include <string>
 #include <vector>
 
+
 class AbstractFunction
 {
+private:
+        const Feature *feature;
 public:
+        AbstractFunction() : feature(NULL) {}
+        AbstractFunction(const Feature& feature) : feature(&feature) {}
 	virtual ~AbstractFunction();
+        virtual bool is_enabled() const { return (feature == NULL) || feature->is_enabled(); };
 	virtual Value evaluate(const class Context *ctx, const class EvalContext *evalctx) const;
 	virtual std::string dump(const std::string &indent, const std::string &name) const;
 };
@@ -21,6 +29,7 @@ public:
 	eval_func_t eval_func;
 
 	BuiltinFunction(eval_func_t f) : eval_func(f) { }
+	BuiltinFunction(eval_func_t f, const Feature& feature) : AbstractFunction(feature), eval_func(f) { }
 	virtual ~BuiltinFunction();
 
 	virtual Value evaluate(const Context *ctx, const EvalContext *evalctx) const;
diff --git a/src/highlighter.cc b/src/highlighter.cc
index 1da0e88..2fb7c65 100644
--- a/src/highlighter.cc
+++ b/src/highlighter.cc
@@ -121,72 +121,110 @@
 */
 
 #include "highlighter.h"
+#include "Preferences.h"
 #include <QTextDocument>
 #include <QTextCursor>
 #include <QColor>
-//#include <iostream>
+//#include "printutils.h"
+
+void format_colors_for_light_background(QMap<QString,QTextCharFormat> &formats)
+{
+	//PRINT("format for light");
+	formats["operator"].setForeground(Qt::blue);
+	formats["math"].setForeground(QColor("Green"));
+	formats["keyword"].setForeground(QColor("Green"));
+	formats["keyword"].setToolTip("Keyword");
+	formats["transform"].setForeground(QColor("Indigo"));
+	formats["csgop"].setForeground(QColor("DarkGreen"));
+	formats["prim3d"].setForeground(QColor("DarkBlue"));
+	formats["prim2d"].setForeground(QColor("MidnightBlue"));
+	formats["import"].setForeground(Qt::darkYellow);
+	formats["special"].setForeground(Qt::darkGreen);
+	formats["extrude"].setForeground(Qt::darkGreen);
+	formats["bracket"].setForeground(QColor("Green"));
+	formats["curlies"].setForeground(QColor(32,32,20));
+	formats["bool"].setForeground(QColor("DarkRed"));
+
+	formats["_$quote"].setForeground(Qt::darkMagenta);
+	formats["_$comment"].setForeground(Qt::darkCyan);
+	formats["_$number"].setForeground(QColor("DarkRed"));
+}
+
+void format_colors_for_dark_background(QMap<QString,QTextCharFormat> &formats)
+{
+	//PRINT("format for dark");
+	formats["operator"].setForeground(Qt::blue);
+	formats["math"].setForeground(Qt::green);
+	formats["keyword"].setForeground(QColor("LightGreen"));
+	formats["keyword"].setToolTip("Keyword");
+	formats["transform"].setForeground(QColor("Indigo"));
+	formats["csgop"].setForeground(QColor("LightGreen"));
+	formats["prim3d"].setForeground(QColor("LightBlue"));
+	formats["prim2d"].setForeground(QColor("LightBlue"));
+	formats["import"].setForeground(QColor("LightYellow"));
+	formats["special"].setForeground(QColor("LightGreen"));
+	formats["extrude"].setForeground(QColor("LightGreen"));
+	formats["bracket"].setForeground(QColor("Green"));
+	formats["curlies"].setForeground(QColor(132,132,120));
+	formats["bool"].setForeground(QColor("LightRed"));
+
+	formats["_$quote"].setForeground(Qt::magenta);
+	formats["_$comment"].setForeground(Qt::cyan);
+	formats["_$number"].setForeground(Qt::red);
+}
+
+void Highlighter::assignFormatsToTokens(const QString &s)
+{
+	//PRINTB("assign fmts %s",s.toStdString());
+	if (s=="For Light Background") {
+		format_colors_for_light_background(this->typeformats);
+	} else if (s=="For Dark Background") {
+		format_colors_for_dark_background(this->typeformats);
+	} else return;
+
+	// Put each token into single QHash, and map it to it's appropriate
+	// qtextchar format (color, bold, etc). For example, '(' is type 
+	// 'bracket' so it should get the 'bracket' format from 
+	// typeformats[] which is, maybe, Green.
+
+	QList<QString>::iterator ki;
+	QList<QString> toktypes = tokentypes.keys();
+	for ( ki=toktypes.begin(); ki!=toktypes.end(); ++ki ) {
+		QString toktype = *ki;
+		QStringList::iterator it;
+		for ( it = tokentypes[toktype].begin(); it < tokentypes[toktype].end(); ++it) {
+			QString token = *it;
+			//PRINTB("set format for %s: type %s", token.toStdString()%toktype.toStdString() );;
+			tokenFormats[ token ] = typeformats [ toktype ];
+		}
+	}
+}
 
 Highlighter::Highlighter(QTextDocument *parent)
 		: QSyntaxHighlighter(parent)
 {
 	tokentypes["operator"] << "=" << "!" << "&&" << "||" << "+" << "-" << "*" << "/" << "%" << "!" << "#" << ";";
-	typeformats["operator"].setForeground(Qt::blue);
-
 	tokentypes["math"] << "abs" << "sign" << "acos" << "asin" << "atan" << "atan2" << "sin" << "cos" << "floor" << "round" << "ceil" << "ln" << "log" << "lookup" << "min" << "max" << "pow" << "sqrt" << "exp" << "rands";
-	typeformats["math"].setForeground(Qt::green);
-	
 	tokentypes["keyword"] << "module" << "function" << "for" << "intersection_for" << "if" << "assign" << "echo"<< "search" << "str";
-	typeformats["keyword"].setForeground(QColor("Green"));
-	typeformats["keyword"].setToolTip("Keyword");
-
 	tokentypes["transform"] << "scale" << "translate" << "rotate" << "multmatrix" << "color" << "projection" << "hull" << "resize" << "mirror" << "minkowski";
-	typeformats["transform"].setForeground(QColor("Indigo"));
-
 	tokentypes["csgop"]	<< "union" << "intersection" << "difference" << "render";
-	typeformats["csgop"].setForeground(QColor("DarkGreen"));
-
 	tokentypes["prim3d"] << "cube" << "cylinder" << "sphere" << "polyhedron";
-	typeformats["prim3d"].setForeground(QColor("DarkBlue"));
-
 	tokentypes["prim2d"] << "square" << "polygon" << "circle";
-	typeformats["prim2d"].setForeground(QColor("MidnightBlue"));
-
 	tokentypes["import"] << "include" << "use" << "import_stl" << "import" << "import_dxf" << "dxf_dim" << "dxf_cross" << "surface";
-	typeformats["import"].setForeground(Qt::darkYellow);
-
 	tokentypes["special"] << "$children" << "child" << "children" << "$fn" << "$fa" << "$fs" << "$t" << "$vpt" << "$vpr";
-	typeformats["special"].setForeground(Qt::darkGreen);
-
 	tokentypes["extrude"] << "linear_extrude" << "rotate_extrude";
-	typeformats["extrude"].setForeground(Qt::darkGreen);
-
 	tokentypes["bracket"] << "[" << "]" << "(" << ")";
-	typeformats["bracket"].setForeground(QColor("Green"));
-
 	tokentypes["curlies"] << "{" << "}";
-	typeformats["curlies"].setForeground(QColor(32,32,20));
-
 	tokentypes["bool"] << "true" << "false";
-	typeformats["bool"].setForeground(QColor("DarkRed"));
 
-	// Put each token into single QHash, mapped to it's format
-	QList<QString>::iterator ki;
-	QList<QString> toktypes = tokentypes.keys();
-	for ( ki=toktypes.begin(); ki!=toktypes.end(); ++ki ) {
-		QString toktype = *ki;
-		QStringList::iterator it;
-		for ( it = tokentypes[toktype].begin(); it < tokentypes[toktype].end(); ++it) {
-			QString token = *it;
-			//std::cout << token.toStdString() << "\n";
-			tokenFormats[ token ] = typeformats [ toktype ];
-		}
-	}
+	tokentypes["_$comment"] << "_$comment"; // bit of a kludge here
+	tokentypes["_$quote"] << "_$quote";
+	tokentypes["_$number"] << "_$number";
 
-	quoteFormat.setForeground(Qt::darkMagenta);
-	commentFormat.setForeground(Qt::darkCyan);
-	errorFormat.setBackground(Qt::red);
-	numberFormat.setForeground(QColor("DarkRed"));
+	QString syntaxhighlight = Preferences::inst()->getValue("editor/syntaxhighlight").toString();
+	this->assignFormatsToTokens(syntaxhighlight);
 
+	errorFormat.setBackground(Qt::red);
 	errorState = false;
 	errorPos = -1;
 	lastErrorBlock = parent->begin();
@@ -198,10 +236,10 @@ void Highlighter::highlightError(int error_pos)
 	errorPos = error_pos;
 
 	QTextBlock err_block = document()->findBlock( errorPos );
-	//std::cout << "error pos: "  << error_pos << " doc len: " << document()->characterCount() << "\n";
+	//PRINTB( "error pos: %i doc len: %i ", error_pos % document()->characterCount() );
 
 	while (err_block.text().remove(QRegExp("\\s+")).size()==0) {
-		//std::cout << "special case - errors at end of file w whitespace\n";
+		//PRINT("special case - errors at end of file w whitespace";
 		err_block = err_block.previous();
 		errorPos = err_block.position()+err_block.length() - 2;
 	}
@@ -211,7 +249,7 @@ void Highlighter::highlightError(int error_pos)
 
 	int block_last_pos = err_block.position() + err_block.length() - 1;
 	if ( errorPos == block_last_pos ) {
-		//std::cout << "special case - errors at ends of certain blocks\n";
+		//PRINT( "special case - errors at ends of certain blocks");
 		errorPos--;
 	}
 	err_block = document()->findBlock(errorPos);
@@ -254,6 +292,18 @@ void Highlighter::highlightBlock(const QString &text)
 	//  << ", err:" << errorPos << "," << errorState
 	//  << ", text:'" << text.toStdString() << "'\n";
 
+	// If desired, skip all highlighting .. except for error highlighting.
+	if (Preferences::inst()->getValue("editor/syntaxhighlight").toString()==QString("Off")) {
+		if (errorState)
+			setFormat( errorPos - block_first_pos, 1, errorFormat);
+		return;
+	}
+
+	// bit of a kludge (for historical convenience)
+	QTextCharFormat &quoteFormat = tokenFormats["_$quote"];
+	QTextCharFormat &commentFormat = tokenFormats["_$comment"];
+	QTextCharFormat &numberFormat = tokenFormats["_$number"];
+
 	// Split the block into chunks (tokens), based on whitespace,
 	// and then highlight each token as appropriate
 	QString newtext = text;
@@ -265,7 +315,7 @@ void Highlighter::highlightBlock(const QString &text)
 	for ( sh = splitHelpers.begin(); sh!=splitHelpers.end(); ++sh ) {
 		newtext = newtext.replace( *sh, " " + *sh + " ");
 	}
-	//std::cout << "\nnewtext: " << newtext.toStdString() << "\n";
+	//PRINTB("\nnewtext: %s", newtext.toStdString() );
 	QStringList tokens = newtext.split(QRegExp("\\s"));
 	int tokindex = 0; // tokindex helps w duplicate tokens in a single block
 	bool numtest;
@@ -273,14 +323,16 @@ void Highlighter::highlightBlock(const QString &text)
 		if ( tokenFormats.contains( *token ) ) {
 			tokindex = text.indexOf( *token, tokindex );
 			setFormat( tokindex, token->size(), tokenFormats[ *token ]);
-			//std::cout  << "found tok '" << (*token).toStdString() << "' at " << tokindex << "\n";
+			std::string tokprint = (*token).toStdString();
+			//PRINTB("found tok '%s' at %i", tokprint % tokindex );
 			tokindex += token->size();
 		} else {
 			(*token).toDouble( &numtest );
 			if ( numtest ) {
 				tokindex = text.indexOf( *token, tokindex );
 				setFormat( tokindex, token->size(), numberFormat );
-				//std::cout  << "found num '" << (*token).toStdString() << "' at " << tokindex << "\n";
+				std::string tokprint = (*token).toStdString();
+				//PRINTB("found num '%s' at %i", tokprint % tokindex );
 				tokindex += token->size();
 			}
 		}
diff --git a/src/highlighter.h b/src/highlighter.h
index b4ffae8..10f9b0a 100644
--- a/src/highlighter.h
+++ b/src/highlighter.h
@@ -10,11 +10,12 @@ class Highlighter : public QSyntaxHighlighter
 public:
 	enum state_e {NORMAL=-1,QUOTE,COMMENT};
 	QHash<QString, QTextCharFormat> tokenFormats;
-	QTextCharFormat errorFormat, commentFormat, quoteFormat, numberFormat;
+	QTextCharFormat errorFormat;
 	Highlighter(QTextDocument *parent);
 	void highlightBlock(const QString &text);
 	void highlightError(int error_pos);
 	void unhighlightLastError();
+	void assignFormatsToTokens(const QString &);
 private:
 	QTextBlock lastErrorBlock;
 	int errorPos;
diff --git a/src/linalg.cc b/src/linalg.cc
index 6799055..274a70a 100644
--- a/src/linalg.cc
+++ b/src/linalg.cc
@@ -14,6 +14,7 @@
 */
 BoundingBox operator*(const Transform3d &m, const BoundingBox &box)
 {
+	if (box.isEmpty()) return box;
 	BoundingBox newbox;
 	Vector3d boxvec[2] = { box.min(), box.max() };
 	for (int k=0;k<2;k++) {
diff --git a/src/linearextrude.cc b/src/linearextrude.cc
index c5d4529..1812504 100644
--- a/src/linearextrude.cc
+++ b/src/linearextrude.cc
@@ -32,7 +32,7 @@
 #include "fileutils.h"
 #include "builtin.h"
 #include "PolySetEvaluator.h"
-#include "openscad.h" // get_fragments_from_r()
+#include "calc.h"
 #include "mathc99.h" 
 
 #include <sstream>
@@ -113,7 +113,7 @@ AbstractNode *LinearExtrudeModule::instantiate(const Context *ctx, const ModuleI
 		if (slices.type() == Value::NUMBER) {
 			node->slices = (int)slices.toDouble();
 		} else {
-			node->slices = (int)fmax(2, fabs(get_fragments_from_r(node->height,
+			node->slices = (int)fmax(2, fabs(Calc::get_fragments_from_r(node->height,
 					node->fn, node->fs, node->fa) * node->twist / 360));
 		}
 		node->has_twist = true;
diff --git a/src/mainwin.cc b/src/mainwin.cc
index 1ad8bc8..c2a7b7e 100644
--- a/src/mainwin.cc
+++ b/src/mainwin.cc
@@ -369,6 +369,8 @@ MainWindow::MainWindow(const QString &filename)
 					this, SLOT(setFont(const QString&,uint)));
 	connect(Preferences::inst(), SIGNAL(openCSGSettingsChanged()),
 					this, SLOT(openCSGSettingsChanged()));
+	connect(Preferences::inst(), SIGNAL(syntaxHighlightChanged(const QString&)), 
+					this, SLOT(setSyntaxHighlight(const QString&)));
 	Preferences::inst()->apply();
 
 	// make sure it looks nice..
@@ -1899,6 +1901,12 @@ void MainWindow::setFont(const QString &family, uint size)
 	editor->setFont(font);
 }
 
+void MainWindow::setSyntaxHighlight(const QString &s)
+{
+	this->highlighter->assignFormatsToTokens( s );
+	this->highlighter->rehighlight(); // slow on large files
+}
+
 void MainWindow::quit()
 {
 	QCloseEvent ev;
diff --git a/src/modcontext.cc b/src/modcontext.cc
index 7941cf5..21b04fd 100644
--- a/src/modcontext.cc
+++ b/src/modcontext.cc
@@ -95,7 +95,12 @@ void ModuleContext::registerBuiltin()
 const AbstractFunction *ModuleContext::findLocalFunction(const std::string &name) const
 {
 	if (this->functions_p && this->functions_p->find(name) != this->functions_p->end()) {
-		return this->functions_p->find(name)->second;
+		AbstractFunction *f = this->functions_p->find(name)->second;
+		if (!f->is_enabled()) {
+			PRINTB("WARNING: Experimental builtin function '%s' is not enabled.", name);
+			return NULL;
+		}
+		return f;
 	}
 	return NULL;
 }
@@ -104,6 +109,10 @@ const AbstractModule *ModuleContext::findLocalModule(const std::string &name) co
 {
 	if (this->modules_p && this->modules_p->find(name) != this->modules_p->end()) {
 		AbstractModule *m = this->modules_p->find(name)->second;
+		if (!m->is_enabled()) {
+			PRINTB("WARNING: Experimental builtin module '%s' is not enabled.", name);
+			return NULL;
+		}
 		std::string replacement = Builtins::instance()->isDeprecated(name);
 		if (!replacement.empty()) {
 			PRINTB("DEPRECATED: The %s() module will be removed in future releases. Use %s() instead.", name % replacement);
diff --git a/src/module.h b/src/module.h
index 8414706..81e5f10 100644
--- a/src/module.h
+++ b/src/module.h
@@ -13,6 +13,7 @@
 #include "value.h"
 #include "typedefs.h"
 #include "localscope.h"
+#include "feature.h"
 
 class ModuleInstantiation
 {
@@ -60,8 +61,13 @@ public:
 
 class AbstractModule
 {
+private:
+        const Feature *feature;
 public:
+        AbstractModule() : feature(NULL) {}
+        AbstractModule(const Feature& feature) : feature(&feature) {}
 	virtual ~AbstractModule();
+        virtual bool is_enabled() const { return (feature == NULL) || feature->is_enabled(); };
 	virtual class AbstractNode *instantiate(const Context *ctx, const ModuleInstantiation *inst, const class EvalContext *evalctx = NULL) const;
 	virtual std::string dump(const std::string &indent, const std::string &name) const;
 };
@@ -70,6 +76,7 @@ class Module : public AbstractModule
 {
 public:
 	Module() { }
+	Module(const Feature& feature) : AbstractModule(feature) { }
 	virtual ~Module();
 
 	virtual AbstractNode *instantiate(const Context *ctx, const ModuleInstantiation *inst, const EvalContext *evalctx = NULL) const;
diff --git a/src/openscad.cc b/src/openscad.cc
index ab84235..0fa9f92 100644
--- a/src/openscad.cc
+++ b/src/openscad.cc
@@ -33,6 +33,7 @@
 #include "builtin.h"
 #include "printutils.h"
 #include "handle_dep.h"
+#include "feature.h"
 #include "parsersettings.h"
 #include "rendersettings.h"
 #include "PlatformUtils.h"
@@ -107,10 +108,12 @@ static void help(const char *progname)
 
 	PRINTB("Usage: %1% [ -o output_file [ -d deps_file ] ]\\\n"
          "%2%[ -m make_command ] [ -D var=val [..] ] \\\n"
+         "%2%[ --version ] [ --info ] \\\n"
          "%2%[ --camera=translatex,y,z,rotx,y,z,dist | \\\n"
          "%2%  --camera=eyex,y,z,centerx,y,z ] \\\n"
          "%2%[ --imgsize=width,height ] [ --projection=(o)rtho|(p)ersp] \\\n"
          "%2%[ --render | --preview[=throwntogether] ] \\\n"
+         "%2%[ --enable=<feature> ] \\\n"
          "%2%filename\n",
  				 progname % (const char *)tabstr);
 	exit(1);
@@ -203,7 +206,7 @@ int cmdline(const char *deps_output_file, const std::string &filename, Camera &c
 #else
 	const std::string application_path = boosty::stringy(boosty::absolute(boost::filesystem::path(argv[0]).parent_path()));
 #endif
-	parser_init(application_path, false);
+	parser_init(application_path);
 	Tree tree;
 #ifdef ENABLE_CGAL
 	CGALEvaluator cgalevaluator(tree);
@@ -513,7 +516,7 @@ int gui(vector<string> &inputFiles, const fs::path &original_path, int argc, cha
 					qexamplesdir = exdir.path();
 				}
 	MainWindow::setExamplesDir(qexamplesdir);
-  parser_init(app_path.toLocal8Bit().constData(), true);
+  parser_init(app_path.toLocal8Bit().constData());
 
 #ifdef Q_WS_MAC
 	installAppleEventHandlers();
@@ -568,7 +571,6 @@ int main(int argc, char **argv)
 
 	fs::path original_path = fs::current_path();
 
-	const char *filename = NULL;
 	const char *output_file = NULL;
 	const char *deps_output_file = NULL;
 
@@ -587,7 +589,8 @@ int main(int argc, char **argv)
 		("x,x", po::value<string>(), "dxf-file")
 		("d,d", po::value<string>(), "deps-file")
 		("m,m", po::value<string>(), "makefile")
-		("D,D", po::value<vector<string> >(), "var=val");
+		("D,D", po::value<vector<string> >(), "var=val")
+		("enable", po::value<vector<string> >(), "enable experimental features");
 
 	po::options_description hidden("Hidden options");
 	hidden.add_options()
@@ -651,6 +654,11 @@ int main(int argc, char **argv)
 			commandline_commands += ";\n";
 		}
 	}
+	if (vm.count("enable")) {
+		BOOST_FOREACH(const string &feature, vm["enable"].as<vector<string> >()) {
+			Feature::enable_feature(feature);
+		}
+	}
 	vector<string> inputFiles;
 	if (vm.count("input-file"))	{
 		inputFiles = vm["input-file"].as<vector<string> >();
diff --git a/src/openscad.h b/src/openscad.h
index dd379a9..0d146c1 100644
--- a/src/openscad.h
+++ b/src/openscad.h
@@ -28,7 +28,6 @@
 #define OPENSCAD_H
 
 extern class FileModule *parse(const char *text, const char *path, int debug);
-extern int get_fragments_from_r(double r, double fn, double fs, double fa);
 
 #include <string>
 extern std::string commandline_commands;
diff --git a/src/parsersettings.cc b/src/parsersettings.cc
index de1ff98..ba4a223 100644
--- a/src/parsersettings.cc
+++ b/src/parsersettings.cc
@@ -88,7 +88,7 @@ fs::path find_valid_path(const fs::path &sourcepath,
 	return fs::path();
 }
 
-void parser_init(const std::string &applicationpath, bool isgui)
+void parser_init(const std::string &applicationpath)
 {
   // Add paths from OPENSCADPATH before adding built-in paths
 	const char *openscadpaths = getenv("OPENSCADPATH");
@@ -117,7 +117,8 @@ void parser_init(const std::string &applicationpath, bool isgui)
 	fs::path tmpdir;
 #ifdef __APPLE__
 	// Libraries can be bundled on Mac. If not, fall back to development layout
-	if (isgui) {
+	bool isbundle = is_directory(libdir / ".." / "Resources");
+	if (isbundle) {
 		libdir /= "../Resources";
 		if (!is_directory(libdir / "libraries")) libdir /= "../../..";
 	}
diff --git a/src/parsersettings.h b/src/parsersettings.h
index 2aef85b..52172b6 100644
--- a/src/parsersettings.h
+++ b/src/parsersettings.h
@@ -6,7 +6,7 @@
 
 extern int parser_error_pos;
 
-void parser_init(const std::string &applicationpath, bool isgui);
+void parser_init(const std::string &applicationpath);
 void add_librarydir(const std::string &libdir);
 fs::path search_libs(const fs::path &localpath);
 fs::path find_valid_path(const fs::path &sourcepath, 
diff --git a/src/primitives.cc b/src/primitives.cc
index f1a4ba7..c9e1072 100644
--- a/src/primitives.cc
+++ b/src/primitives.cc
@@ -34,11 +34,16 @@
 #include "printutils.h"
 #include "visitor.h"
 #include "context.h"
+#include "calc.h"
+#include "mathc99.h"
 #include <sstream>
 #include <assert.h>
 #include <boost/assign/std/vector.hpp>
 using namespace boost::assign; // bring 'operator+=()' into scope
 
+#include <boost/math/special_functions/fpclassify.hpp>
+using boost::math::isinf;
+
 #define F_MINIMUM 0.01
 
 enum primitive_type_e {
@@ -275,17 +280,6 @@ AbstractNode *PrimitiveModule::instantiate(const Context *ctx, const ModuleInsta
 	return node;
 }
 
-/*!
-	Returns the number of subdivision of a whole circle, given radius and
-	the three special variables $fn, $fs and $fa
-*/
-int get_fragments_from_r(double r, double fn, double fs, double fa)
-{
-	if (r < GRID_FINE) return 3;
-	if (fn > 0.0) return (int)(fn >= 3 ? fn : 3);
-	return (int)ceil(fmax(fmin(360.0 / fa, r*2*M_PI / fs), 5));
-}
-
 struct point2d {
 	double x, y;
 };
@@ -303,8 +297,9 @@ PolySet *PrimitiveNode::evaluate_polyset(class PolySetEvaluator *) const
 {
 	PolySet *p = new PolySet();
 
-	if (this->type == CUBE && this->x > 0 && this->y > 0 && this->z > 0)
-	{
+	if (this->type == CUBE && 
+			this->x > 0 && this->y > 0 && this->z > 0 &&
+			!isinf(this->x) > 0 && !isinf(this->y) > 0 && !isinf(this->z) > 0) {
 		double x1, x2, y1, y2, z1, z2;
 		if (this->center) {
 			x1 = -this->x/2;
@@ -357,14 +352,14 @@ PolySet *PrimitiveNode::evaluate_polyset(class PolySetEvaluator *) const
 		p->append_vertex(x1, y2, z2);
 	}
 
-	if (this->type == SPHERE && this->r1 > 0)
+	if (this->type == SPHERE && this->r1 > 0 && !isinf(this->r1))
 	{
 		struct ring_s {
 			point2d *points;
 			double z;
 		};
 
-		int fragments = get_fragments_from_r(r1, fn, fs, fa);
+		int fragments = Calc::get_fragments_from_r(r1, fn, fs, fa);
 		int rings = (fragments+1)/2;
 // Uncomment the following three lines to enable experimental sphere tesselation
 //		if (rings % 2 == 0) rings++; // To ensure that the middle ring is at phi == 0 degrees
@@ -425,9 +420,10 @@ sphere_next_r2:
 	}
 
 	if (this->type == CYLINDER && 
-			this->h > 0 && this->r1 >=0 && this->r2 >= 0 && (this->r1 > 0 || this->r2 > 0))
-	{
-		int fragments = get_fragments_from_r(fmax(this->r1, this->r2), this->fn, this->fs, this->fa);
+			this->h > 0 && !isinf(this->h) &&
+			this->r1 >=0 && this->r2 >= 0 && (this->r1 + this->r2) > 0 &&
+			!isinf(this->r1) && !isinf(this->r2)) {
+		int fragments = Calc::get_fragments_from_r(fmax(this->r1, this->r2), this->fn, this->fs, this->fa);
 
 		double z1, z2;
 		if (this->center) {
@@ -490,12 +486,18 @@ sphere_next_r2:
 		for (size_t i=0; i<this->faces.toVector().size(); i++)
 		{
 			p->append_poly();
-			for (size_t j=0; j<this->faces.toVector()[i].toVector().size(); j++) {
-				size_t pt = this->faces.toVector()[i].toVector()[j].toDouble();
+			const Value::VectorType &vec = this->faces.toVector()[i].toVector();
+			for (size_t j=0; j<vec.size(); j++) {
+				size_t pt = vec[j].toDouble();
 				if (pt < this->points.toVector().size()) {
 					double px, py, pz;
-					if (this->points.toVector()[pt].getVec3(px, py, pz))
-						p->insert_vertex(px, py, pz);
+					if (!this->points.toVector()[pt].getVec3(px, py, pz) ||
+							isinf(px) || isinf(py) || isinf(pz)) {
+						PRINTB("ERROR: Unable to convert point at index %d to a vec3 of numbers", j);
+						delete p;
+						return NULL;
+					}
+					p->insert_vertex(px, py, pz);
 				}
 			}
 		}
@@ -525,7 +527,7 @@ sphere_next_r2:
 
 	if (this->type == CIRCLE)
 	{
-		int fragments = get_fragments_from_r(this->r1, this->fn, this->fs, this->fa);
+		int fragments = Calc::get_fragments_from_r(this->r1, this->fn, this->fs, this->fa);
 
 		p->is2d = true;
 		p->append_poly();
@@ -542,7 +544,8 @@ sphere_next_r2:
 
 		for (size_t i=0; i<this->points.toVector().size(); i++) {
 			double x,y;
-			if (!this->points.toVector()[i].getVec2(x, y)) {
+			if (!this->points.toVector()[i].getVec2(x, y) ||
+					isinf(x) || isinf(y)) {
 				PRINTB("ERROR: Unable to convert point at index %d to a vec2 of numbers", i);
 				delete p;
 				return NULL;
diff --git a/src/value.cc b/src/value.cc
index c8a88c6..3a6540f 100644
--- a/src/value.cc
+++ b/src/value.cc
@@ -39,6 +39,10 @@
 /*Unicode support for string lengths and array accesses*/
 #include <glib.h>
 
+#include <boost/math/special_functions/fpclassify.hpp>
+using boost::math::isnan;
+using boost::math::isinf;
+
 std::ostream &operator<<(std::ostream &stream, const Filename &filename)
 {
   fs::path fnpath = fs::path( (std::string)filename );
@@ -642,7 +646,11 @@ void Value::RangeType::normalize() {
 }
 
 uint32_t Value::RangeType::nbsteps() const {
-  if (begin_val == end_val) {
+  if (isnan(step_val) || isinf(begin_val) || (isinf(end_val))) {
+    return std::numeric_limits<uint32_t>::max();
+  }
+
+  if ((begin_val == end_val) || isinf(step_val)) {
     return 0;
   }