First step in refactoring: brought both Paint and Mapping under the common umbrella class Element and implemented basic QProperties.

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);
+}
+