diff --git a/doomsday/apps/client/src/client/clientsubsector.cpp b/doomsday/apps/client/src/client/clientsubsector.cpp
index 59a721f54f..5630f2ec35 100644
--- a/doomsday/apps/client/src/client/clientsubsector.cpp
+++ b/doomsday/apps/client/src/client/clientsubsector.cpp
@@ -119,7 +119,7 @@ DENG2_PIMPL(ClientSubsector)
         {
             ~EdgeLoops() { clear(); }
 
-            void clear() 
+            void clear()
             {
                 qDeleteAll(*this);
                 QList<ClEdgeLoop *>::clear();
@@ -201,7 +201,7 @@ DENG2_PIMPL(ClientSubsector)
     bool needReverbUpdate = true;
 
     /// Per surface lists of light decoration info and state.
-    QMap<Surface *, DecoratedSurface> decorSurfaces;
+    QHash<Surface *, DecoratedSurface> decorSurfaces;
 
     Impl(Public *i) : Base(i)
     {}
diff --git a/doomsday/apps/client/src/world/base/line.cpp b/doomsday/apps/client/src/world/base/line.cpp
index 1800055168..282ca3dcd6 100644
--- a/doomsday/apps/client/src/world/base/line.cpp
+++ b/doomsday/apps/client/src/world/base/line.cpp
@@ -1048,7 +1048,7 @@ DENG2_PIMPL(Line)
         slopetype_t slopeType;  ///< Logical line slope (i.e., world angle) classification.
         AABoxd bounds;          ///< Axis-aligned bounding box.
 
-        GeomData(Vertex &from, Vertex &to)
+        GeomData(Vertex const &from, Vertex const &to)
             : direction(to.origin() - from.origin())
             , length   (direction.length())
             , angle    (bamsAtan2(dint(direction.y), dint(direction.x)))
@@ -1057,6 +1057,11 @@ DENG2_PIMPL(Line)
             V2d_InitBoxXY (bounds.arvec2, from.x(), from.y());
             V2d_AddToBoxXY(bounds.arvec2, to  .x(), to  .y());
         }
+
+        static ddouble calcLength(Vertex const &from, Vertex const &to)
+        {
+            return (to.origin() - from.origin()).length();
+        }
     };
     std::unique_ptr<GeomData> gdata;
 
@@ -1259,7 +1264,8 @@ Vector2d const &Line::direction() const
 
 ddouble Line::length() const
 {
-    return d->geom().length;
+    if (d->gdata) return d->gdata->length;
+    return Impl::GeomData::calcLength(*d->from, *d->to);
 }
 
 slopetype_t Line::slopeType() const
diff --git a/doomsday/apps/client/src/world/base/surface.cpp b/doomsday/apps/client/src/world/base/surface.cpp
index 7e91f48397..a318c5ae2d 100644
--- a/doomsday/apps/client/src/world/base/surface.cpp
+++ b/doomsday/apps/client/src/world/base/surface.cpp
@@ -224,7 +224,7 @@ Material &Surface::material() const
 
 Material *Surface::materialPtr() const
 {
-    return hasMaterial() ? &material() : nullptr;
+    return d->material;
 }
 
 Surface &Surface::setMaterial(Material *newMaterial, bool isMissingFix)
diff --git a/doomsday/apps/libdoomsday/include/doomsday/defs/definition.h b/doomsday/apps/libdoomsday/include/doomsday/defs/definition.h
index e54e9ac60d..02ed15276d 100644
--- a/doomsday/apps/libdoomsday/include/doomsday/defs/definition.h
+++ b/doomsday/apps/libdoomsday/include/doomsday/defs/definition.h
@@ -59,6 +59,8 @@ class LIBDOOMSDAY_PUBLIC Definition : public de::RecordAccessor
      * call this before inserting their own members.
      */
     virtual void resetToDefaults();
+
+    static de::String const VAR_ORDER; // __order__
 };
 
 } // namespace defn
diff --git a/doomsday/apps/libdoomsday/include/doomsday/world/mapelement.h b/doomsday/apps/libdoomsday/include/doomsday/world/mapelement.h
index 16441cc591..bad5875d7d 100644
--- a/doomsday/apps/libdoomsday/include/doomsday/world/mapelement.h
+++ b/doomsday/apps/libdoomsday/include/doomsday/world/mapelement.h
@@ -44,9 +44,6 @@ class LIBDOOMSDAY_PUBLIC MapElement
     DENG2_NO_ASSIGN(MapElement)
 
 public:
-    /// No parent map element is configured. @ingroup errors
-    DENG2_ERROR(MissingParentError);
-
     /// Attempted to configure an invalid parent element. @ingroup errors
     DENG2_ERROR(InvalidParentError);
 
@@ -85,15 +82,22 @@ class LIBDOOMSDAY_PUBLIC MapElement
      *
      * @see parent(), setParent()
      */
-    bool hasParent() const;
+    inline bool hasParent() const { return _parent != nullptr; }
 
     /**
      * Returns the parent of the map element.
      *
      * @see hasParent(), setParent()
      */
-    MapElement       &parent();
-    MapElement const &parent() const;
+    inline MapElement &parent() {
+        DENG2_ASSERT(_parent);
+        return *_parent;
+    }
+
+    inline MapElement const &parent() const {
+        DENG2_ASSERT(_parent);
+        return *_parent;
+    }
 
     /**
      * Change the parent of the map element.
@@ -197,6 +201,8 @@ class LIBDOOMSDAY_PUBLIC MapElement
 
 private:
     DENG2_PRIVATE(d)
+
+    MapElement *_parent = nullptr;
 };
 
 } // namespace world
diff --git a/doomsday/apps/libdoomsday/src/defs/ded.cpp b/doomsday/apps/libdoomsday/src/defs/ded.cpp
index dc6857259b..8b315e55a4 100644
--- a/doomsday/apps/libdoomsday/src/defs/ded.cpp
+++ b/doomsday/apps/libdoomsday/src/defs/ded.cpp
@@ -101,14 +101,14 @@ int ded_s::addFlag(String const &id, int value)
     Record &def = flags.append();
     def.addText("id", id);
     def.addNumber("value", value);
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addEpisode()
 {
     Record &def = episodes.append();
     defn::Episode(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addThing(String const &id)
@@ -116,7 +116,7 @@ int ded_s::addThing(String const &id)
     Record &def = things.append();
     defn::Thing(def).resetToDefaults();
     def.set("id", id);
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addState(String const &id)
@@ -124,56 +124,56 @@ int ded_s::addState(String const &id)
     Record &def = states.append();
     defn::State(def).resetToDefaults();
     def.set("id", id);
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addDecoration()
 {
     Record &def = decorations.append();
     defn::Decoration(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addFinale()
 {
     Record &def = finales.append();
     defn::Finale(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addMapInfo()
 {
     Record &def = mapInfos.append();
     defn::MapInfo(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addMaterial()
 {
     Record &def = materials.append();
     defn::Material(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addModel()
 {
     Record &def = models.append();
     defn::Model(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addMusic()
 {
     Record &def = musics.append();
     defn::Music(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 int ded_s::addSky()
 {
     Record &def = skies.append();
     defn::Sky(def).resetToDefaults();
-    return def.geti("__order__");
+    return def.geti(defn::Definition::VAR_ORDER);
 }
 
 void ded_s::release()
@@ -362,7 +362,7 @@ int ded_s::getMobjNum(String const &id) const
 {
     if (Record const *def = things.tryFind("id", id))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     /*
     for (i = 0; i < mobjs.size(); ++i)
@@ -383,7 +383,7 @@ int ded_s::getMobjNumForName(const char *name) const
             return i;*/
     if (Record const *def = things.tryFind("name", name))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
 
     return -1;
@@ -400,7 +400,7 @@ int ded_s::getStateNum(String const &id) const
 {
     if (Record const *def = states.tryFind("id", id))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;
 }
@@ -440,7 +440,7 @@ int ded_s::getEpisodeNum(String const &id) const
 {
     if (Record const *def = episodes.tryFind("id", id))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;
 }
@@ -449,7 +449,7 @@ int ded_s::getMapInfoNum(de::Uri const &uri) const
 {
     if (Record const *def = mapInfos.tryFind("id", uri.compose()))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;  // Not found.
 }
@@ -478,7 +478,7 @@ int ded_s::getMaterialNum(de::Uri const &uri) const
 
     if (Record const *def = materials.tryFind("id", uri.compose()))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;  // Not found.
 }
@@ -487,7 +487,7 @@ int ded_s::getModelNum(const char *id) const
 {
     if (Record const *def = models.tryFind("id", id))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;
 
@@ -506,7 +506,7 @@ int ded_s::getSkyNum(char const *id) const
 {
     if (Record const *def = skies.tryFind("id", id))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;
 
@@ -572,7 +572,7 @@ int ded_s::getMusicNum(char const *id) const
 {
     if (Record const *def = musics.tryFind("id", id))
     {
-        return def->geti("__order__");
+        return def->geti(defn::Definition::VAR_ORDER);
     }
     return -1;
 
diff --git a/doomsday/apps/libdoomsday/src/defs/dedregister.cpp b/doomsday/apps/libdoomsday/src/defs/dedregister.cpp
index 24e750f9b5..85f56cd7ee 100644
--- a/doomsday/apps/libdoomsday/src/defs/dedregister.cpp
+++ b/doomsday/apps/libdoomsday/src/defs/dedregister.cpp
@@ -17,6 +17,7 @@
  */
 
 #include "doomsday/defs/dedregister.h"
+#include "doomsday/defs/definition.h"
 
 #include <de/ArrayValue>
 #include <de/DictionaryValue>
@@ -142,7 +143,7 @@ DENG2_PIMPL(DEDRegister)
         Record *sub = new Record;
 
         // Let each subrecord know their ordinal.
-        sub->set("__order__", int(order().size())).setReadOnly();
+        sub->set(defn::Definition::VAR_ORDER, int(order().size())).setReadOnly();
 
         // Observe what goes into this record.
         //sub->audienceForDeletion() += this;
diff --git a/doomsday/apps/libdoomsday/src/defs/definition.cpp b/doomsday/apps/libdoomsday/src/defs/definition.cpp
index a8454cbd1d..8a9f7eb602 100644
--- a/doomsday/apps/libdoomsday/src/defs/definition.cpp
+++ b/doomsday/apps/libdoomsday/src/defs/definition.cpp
@@ -24,6 +24,8 @@ using namespace de;
 
 namespace defn {
 
+String const Definition::VAR_ORDER("__order__");
+
 Record &Definition::def()
 {
     return const_cast<Record &>(accessedRecord());
@@ -37,7 +39,7 @@ Record const &Definition::def() const
 int Definition::order() const
 {
     if (!accessedRecordPtr()) return -1;
-    return geti("__order__");
+    return geti(VAR_ORDER);
 }
 
 Definition::operator bool() const
diff --git a/doomsday/apps/libdoomsday/src/world/mapelement.cpp b/doomsday/apps/libdoomsday/src/world/mapelement.cpp
index 26fc376c80..e5f10c2e93 100644
--- a/doomsday/apps/libdoomsday/src/world/mapelement.cpp
+++ b/doomsday/apps/libdoomsday/src/world/mapelement.cpp
@@ -28,7 +28,6 @@ namespace world {
 DENG2_PIMPL_NOREF(MapElement)
 {
     dint type;
-    MapElement *parent  = nullptr;
     Map *map            = nullptr;
     dint indexInMap     = NoIndex;
     dint indexInArchive = NoIndex;
@@ -50,23 +49,6 @@ dint MapElement::type() const
     return d->type;
 }
 
-bool MapElement::hasParent() const
-{
-    return d->parent != nullptr;
-}
-
-MapElement &MapElement::parent()
-{
-    return const_cast<MapElement &>(const_cast<MapElement const *>(this)->parent());
-}
-
-MapElement const &MapElement::parent() const
-{
-    if (d->parent) return *d->parent;
-    /// @throw MissingParentError  Attempted with no parent element is attributed.
-    throw MissingParentError("MapElement::parent", "No parent map element is attributed");
-}
-
 void MapElement::setParent(MapElement *newParent)
 {
     if (newParent == this)
@@ -74,15 +56,15 @@ void MapElement::setParent(MapElement *newParent)
         /// @throw InvalidParentError  Attempted to attribute *this* element as parent of itself.
         throw InvalidParentError("MapElement::setParent", "Cannot attribute 'this' map element as a parent of itself");
     }
-    d->parent = newParent;
+    _parent = newParent;
 }
 
 bool MapElement::hasMap() const
 {
     // If a parent is configured this property is delegated to the parent.
-    if (d->parent)
+    if (_parent)
     {
-        return d->parent->hasMap();
+        return _parent->hasMap();
     }
     return d->map != nullptr;
 }
@@ -90,9 +72,9 @@ bool MapElement::hasMap() const
 Map &MapElement::map() const
 {
     // If a parent is configured this property is delegated to the parent.
-    if (d->parent)
+    if (_parent)
     {
-        return d->parent->map();
+        return _parent->map();
     }
     if (d->map)
     {
@@ -105,7 +87,7 @@ Map &MapElement::map() const
 void MapElement::setMap(Map *newMap)
 {
     // If a parent is configured this property is delegated to the parent.
-    if (!d->parent)
+    if (!_parent)
     {
         d->map = newMap;
         return;
diff --git a/doomsday/apps/plugins/dehread/src/dehreader.cpp b/doomsday/apps/plugins/dehread/src/dehreader.cpp
index c0ba85330b..65b1004ed0 100644
--- a/doomsday/apps/plugins/dehread/src/dehreader.cpp
+++ b/doomsday/apps/plugins/dehread/src/dehreader.cpp
@@ -796,7 +796,7 @@ class DehReader
     {
         LOG_AS("parseThing");
 
-        int const thingNum = mobj.geti("__order__");
+        int const thingNum = mobj.geti(defn::Definition::VAR_ORDER);
         bool hadHeight     = false, checkHeight = false;
 
         for(; lineInCurrentSection(); skipToNextLine())
@@ -1043,7 +1043,7 @@ class DehReader
     void parseFrame(defn::State state, bool ignore = false)
     {
         LOG_AS("parseFrame");
-        int const stateNum = state.geti("__order__");
+        int const stateNum = state.geti(defn::Definition::VAR_ORDER);
 
         for(; lineInCurrentSection(); skipToNextLine())
         {
@@ -1390,7 +1390,7 @@ class DehReader
     void parsePointer(defn::State state, bool ignore)
     {
         LOG_AS("parsePointer");
-        int const stateNum = state.geti("__order__");
+        int const stateNum = state.geti(defn::Definition::VAR_ORDER);
 
         for(; lineInCurrentSection(); skipToNextLine())
         {
diff --git a/doomsday/sdk/libcore/src/data/record.cpp b/doomsday/sdk/libcore/src/data/record.cpp
index 650bae3a1f..238b789c9e 100644
--- a/doomsday/sdk/libcore/src/data/record.cpp
+++ b/doomsday/sdk/libcore/src/data/record.cpp
@@ -185,8 +185,6 @@ DENG2_PIMPL(Record), public Lockable
 
     Variable const *findMemberByPath(String const &name) const
     {
-        DENG2_GUARD(this);
-
         // Path notation allows looking into subrecords.
         int pos = name.indexOf('.');
         if (pos >= 0)
@@ -198,6 +196,8 @@ DENG2_PIMPL(Record), public Lockable
             return self[subName].value<RecordValue>().dereference().d->findMemberByPath(remaining);
         }
 
+        DENG2_GUARD(this);
+
         Members::const_iterator found = members.constFind(name);
         if (found != members.constEnd())
         {