diff --git a/Element.cpp b/Element.cpp
new file mode 100644
index 0000000..0bcbb10
--- /dev/null
+++ b/Element.cpp
@@ -0,0 +1,40 @@
+/*
+ * Element.cpp
+ *
+ * (c) 2016 Sofian Audry -- info(@)sofianaudry(.)com
+ *
+ * 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Element.h"
+
+Element::Element(uid id, UidAllocator* allocator) : _name(""), _isLocked(false), _opacity(1.0f), _allocator(allocator)
+{
+  if (id == NULL_UID)
+    id = allocator->allocate();
+  else
+  {
+    Q_ASSERT(!allocator->exists(id));
+    allocator->reserve(id);
+  }
+  // Assign id.
+  _id = id;
+  // Reset name.
+  unsetName();
+}
+
+Element::~Element() {
+  _allocator->free(_id);
+}
+
diff --git a/Element.h b/Element.h
new file mode 100644
index 0000000..7594830
--- /dev/null
+++ b/Element.h
@@ -0,0 +1,66 @@
+/*
+ * Element.h
+ *
+ * (c) 2016 Sofian Audry -- info(@)sofianaudry(.)com
+ *
+ * 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef ELEMENT_H_
+#define ELEMENT_H_
+
+#include <QtGlobal>
+#include <QObject>
+
+#include "UidAllocator.h"
+
+class Element : public QObject
+{
+  Q_OBJECT
+
+  Q_PROPERTY(uid     id      READ getId)
+  Q_PROPERTY(QString name    READ getName WRITE setName RESET unsetName)
+  Q_PROPERTY(bool locked  READ isLocked  WRITE setLocked)
+  Q_PROPERTY(float   opacity READ getOpacity WRITE setOpacity)
+
+public:
+  Element(uid id, UidAllocator* allocator);
+  virtual ~Element();
+
+  uid getId() const { return _id; }
+
+  void setName(const QString& name) { _name = name; }
+  QString getName() const { return _name; }
+  virtual void unsetName() { _name = _id; }
+
+  float getOpacity() const { return _opacity; }
+  void setOpacity(float opacity) {
+    _opacity = qBound(opacity, 0.0f, 1.0f);
+  }
+
+  bool isLocked() const    { return _isLocked; }
+  void setLocked(bool locked)    { _isLocked = locked; }
+  void toggleLocked()  { _isLocked = !_isLocked; }
+
+  virtual void build() {}
+
+private:
+  uid _id;
+  QString _name;
+  bool _isLocked;
+  float _opacity;
+  UidAllocator* _allocator;
+};
+
+#endif /* MOBJECT_H_ */
diff --git a/Mapping.cpp b/Mapping.cpp
index 75b8f94..1701421 100644
--- a/Mapping.cpp
+++ b/Mapping.cpp
@@ -23,25 +23,15 @@
 UidAllocator Mapping::allocator;
 
 Mapping::Mapping(Paint::ptr paint, MShape::ptr shape, uid id)
-  : _paint(paint), _shape(shape),
-    _isLocked(false), _isSolo(false), _isVisible(true), _opacity(1.0f)
+  : Element(id, &allocator),
+    _paint(paint), _shape(shape),
+    _isSolo(false), _isVisible(true)
 {
-  if (id == NULL_UID)
-    id = allocator.allocate();
-  else
-  {
-    Q_ASSERT(!allocator.exists(id));
-    allocator.reserve(id);
-  }
-
-  // Assign id.
-  _id = id;
-
   // Default.
-  _depth = _id;
+  _depth = getId();
 }
 
 Mapping::~Mapping() {
-  allocator.free(_id);
+  allocator.free(getId());
 }
 
diff --git a/Mapping.h b/Mapping.h
index 7a6d568..bed8561 100644
--- a/Mapping.h
+++ b/Mapping.h
@@ -25,6 +25,9 @@
 
 #include "Shape.h"
 #include "Paint.h"
+
+#include "Element.h"
+
 #include "UidAllocator.h"
 
 /**
@@ -39,8 +42,20 @@
  * can thus change their opacity level, toggle their visibility, set
  * them in "solo" mode and lock them.
  */
-class Mapping
+class Mapping : public Element
 {
+  Q_OBJECT
+
+  Q_PROPERTY(bool solo    READ isSolo    WRITE setSolo)
+  Q_PROPERTY(bool visible READ isVisible WRITE setVisible)
+  Q_PROPERTY(int  depth   READ getDepth  WRITE setDepth)
+
+  Q_PROPERTY(MShape::ptr shape READ getShape)
+  Q_PROPERTY(MShape::ptr inputShape READ getInputShape)
+
+  Q_PROPERTY(bool hasInputShape READ hasInputShape STORED false)
+  Q_PROPERTY(Paint::ptr paint READ getPaint WRITE setPaint)
+
 protected:
   /// The input Paint instance.
   Paint::ptr _paint;
@@ -51,12 +66,8 @@ protected:
 private:
   static UidAllocator allocator;
 
-  uid _id;
-
-  bool _isLocked;
   bool _isSolo;
   bool _isVisible;
-  float _opacity;
   int _depth; // depth of the layer
 
 protected:
@@ -94,28 +105,18 @@ public:
   /// Returns the input (source) shape (if this mapping has one) or a null pointer if not.
   virtual MShape::ptr getInputShape() const { return MShape::ptr(); }
 
-  uid getId() const { return _id; }
-
-  void setLocked(bool locked)    { _isLocked = locked; }
   void setSolo(bool solo)        { _isSolo = solo; }
   void setVisible(bool visible)  { _isVisible = visible; }
-  void setRawOpacity(float opacity) {
-    Q_ASSERT(0.0f <= opacity && opacity <= 1.0f);
-    _opacity = opacity;
-  }
   void setDepth(int depth) { _depth = depth; }
 
-  void toggleLocked()  { _isLocked = !_isLocked; }
   void toggleSolo()    { _isSolo = !_isSolo; }
   void toggleVisible() { _isVisible = !_isVisible; }
 
-  bool isLocked() const    { return _isLocked; }
   bool isSolo() const      { return _isSolo; }
   bool isVisible() const   { return _isVisible; }
-  float getRawOpacity() const { return _opacity; }
   int getDepth() const { return _depth; }
 
-  float getOpacity() const { return _opacity * _paint->getOpacity(); }
+  float getComputedOpacity() const { return getOpacity() * _paint->getOpacity(); }
 
   void setPaint(Paint::ptr p) { _paint = p; }
 };
diff --git a/MappingGui.cpp b/MappingGui.cpp
index cca6c71..1e5c9d6 100644
--- a/MappingGui.cpp
+++ b/MappingGui.cpp
@@ -45,7 +45,7 @@ MappingGui::MappingGui(Mapping::ptr mapping)
   _opacityItem->setAttribute("minimum", 0.0);
   _opacityItem->setAttribute("maximum", 100.0);
   _opacityItem->setAttribute("decimals", 1);
-  _opacityItem->setValue(_mapping->getRawOpacity()*100.0);
+  _opacityItem->setValue(_mapping->getOpacity()*100.0);
   _topItem->addSubProperty(_opacityItem);
 
   // Output shape.
@@ -69,9 +69,9 @@ void MappingGui::setValue(QtProperty* property, const QVariant& value)
   if (property == _opacityItem)
   {
     double opacity = qBound(value.toDouble() / 100.0, 0.0, 1.0);
-    if (opacity != _mapping->getRawOpacity())
+    if (opacity != _mapping->getOpacity())
     {
-      _mapping->setRawOpacity(opacity);
+      _mapping->setOpacity(opacity);
       emit valueChanged();
     }
   }
diff --git a/Paint.cpp b/Paint.cpp
index e4e2d59..695cadb 100644
--- a/Paint.cpp
+++ b/Paint.cpp
@@ -24,30 +24,20 @@
 
 UidAllocator Paint::allocator;
 
-Paint::Paint(uid id)
-  : _opacity(1.0f)
+Paint::Paint(uid id) : Element(id, &allocator)
 {
-  if (id == NULL_UID)
-    id = allocator.allocate();
-  else
-  {
-    Q_ASSERT(!allocator.exists(id));
-    allocator.reserve(id);
-  }
-  // Assign id.
-  _id = id;
 }
 
 Paint::~Paint()
 {
-  allocator.free(_id);
+  allocator.free(getId());
 }
 
 bool Image::setUri(const QString &uri)
 {
   this->uri = uri;
   build();
-  return true;
+  return !image.isNull();
 }
 
 /* Implementation of the Video class */
diff --git a/Paint.h b/Paint.h
index 938673f..f23dcf5 100644
--- a/Paint.h
+++ b/Paint.h
@@ -24,6 +24,7 @@
 
 #include <QtGlobal>
 #include <QtOpenGL>
+
 #include <string>
 #include <QColor>
 #include <QMutex>
@@ -34,7 +35,7 @@
 #include <GL/gl.h>
 #endif
 
-#include "UidAllocator.h"
+#include "Element.h"
 
 /**
  * A Paint is a style that can be applied when drawing potentially any shape.
@@ -43,8 +44,10 @@
  * There must be a MappingGui that implements this paint for every shape 
  * so that this shape might be drawn with it.
  */
-class Paint
+class Paint : public Element
 {
+  Q_OBJECT
+
 private:
   static UidAllocator allocator;
 
@@ -60,8 +63,6 @@ public:
 
   static const UidAllocator& getUidAllocator() { return allocator; }
 
-  virtual void build() {}
-
   /// This method should be called at each call of draw().
   virtual void update() {}
 
@@ -80,25 +81,15 @@ public:
   /// Unlocks mutex (default = no effect).
   virtual void unlockMutex() {}
 
-  void setName(const QString& name) { _name = name; }
-  QString getName() const { return _name; }
-  uid getId() const { return _id; }
-
-  float getOpacity() const { return _opacity; }
-  void setOpacity(float opacity) {
-    Q_ASSERT(0.0f <= opacity && opacity <= 1.0f);
-    _opacity = opacity;
-  }
-
   virtual QString getType() const = 0;
-
-private:
-  QString _name;
-  float _opacity;
 };
 
 class Color : public Paint
 {
+  Q_OBJECT
+
+  Q_PROPERTY(QColor color READ getColor WRITE setColor)
+
 protected:
   QColor color;
 
@@ -107,7 +98,7 @@ public:
   Color(const QColor& color_, uid id=NULL_UID) : Paint(id), color(color_) {}
 
   QColor getColor() const { return color; }
-  virtual void setColor(const QColor& color_) { color = color_; }
+  void setColor(const QColor& color_) { color = color_; }
 
   virtual QString getType() const { return "color"; }
 };
@@ -119,6 +110,11 @@ public:
  */
 class Texture : public Paint
 {
+  Q_OBJECT
+
+  Q_PROPERTY(GLfloat x READ getX WRITE setX)
+  Q_PROPERTY(GLfloat y READ getY WRITE setY)
+
 protected:
   GLuint textureId;
   GLfloat x;
@@ -151,13 +147,22 @@ public:
   /// Returns true iff bits have changed since last call to getBits().
   virtual bool bitsHaveChanged() const = 0;
 
-  virtual void setPosition(GLfloat xPos, GLfloat yPos) {
-    x = xPos;
-    y = yPos;
-  }
   virtual GLfloat getX() const { return x; }
   virtual GLfloat getY() const { return y; }
 
+  virtual void setX(GLfloat xPos) {
+      x = xPos;
+    }
+
+  virtual void setY(GLfloat yPos) {
+      y = yPos;
+    }
+
+  virtual void setPosition(GLfloat xPos, GLfloat yPos) {
+    setX(xPos);
+    setY(yPos);
+  }
+
   virtual QRectF getRect() const { return QRectF(getX(), getY(), getWidth(), getHeight()); }
 };
 
@@ -166,6 +171,10 @@ public:
  */
 class Image : public Texture
 {
+  Q_OBJECT
+
+  Q_PROPERTY(QString uri READ getUri WRITE setUri)
+
 protected:
   QString uri;
   QImage image;
@@ -207,6 +216,13 @@ class MediaImpl; // forward declaration
  */
 class Media : public Texture
 {
+  Q_OBJECT
+
+  Q_PROPERTY(QString uri READ getUri WRITE setUri)
+
+  Q_PROPERTY(double volume READ getVolume WRITE setVolume)
+  Q_PROPERTY(double rate READ getRate WRITE setRate)
+
 protected:
   QString uri;
 public:
diff --git a/ShapeGraphicsItem.cpp b/ShapeGraphicsItem.cpp
index c935be7..4a74f4b 100644
--- a/ShapeGraphicsItem.cpp
+++ b/ShapeGraphicsItem.cpp
@@ -114,7 +114,7 @@ void ColorGraphicsItem::_prePaint(QPainter *painter,
 
   // Set brush.
   QColor col = color->getColor();
-  col.setAlphaF(getMapping()->getOpacity());
+  col.setAlphaF(getMapping()->getComputedOpacity());
   painter->setBrush(col);
 }
 
@@ -257,7 +257,7 @@ void TextureGraphicsItem::_prePaint(QPainter* painter,
 
   // Set texture color (apply opacity).
   glColor4f(1.0f, 1.0f, 1.0f,
-            isOutput() ? getMapping()->getOpacity() : getMapping()->getPaint()->getOpacity());
+            isOutput() ? getMapping()->getComputedOpacity() : getMapping()->getPaint()->getOpacity());
 }
 
 void TextureGraphicsItem::_postPaint(QPainter* painter,
diff --git a/mapmap.pro b/mapmap.pro
index 3264353..244e8fe 100644
--- a/mapmap.pro
+++ b/mapmap.pro
@@ -9,6 +9,7 @@ DEFINES += UNICODE QT_THREAD_SUPPORT QT_CORE_LIB QT_GUI_LIB
 HEADERS  = \
     Commands.h \
     DestinationGLCanvas.h \
+    Element.h \
     MM.h \
     MainApplication.h \
     MainWindow.h \
@@ -37,6 +38,7 @@ HEADERS  = \
 SOURCES  = \
     Commands.cpp \
     DestinationGLCanvas.cpp \
+    Element.cpp \
     MM.cpp \
     MainApplication.cpp \
     MainWindow.cpp \