Sdk/Widget: Add Canvas system, mouse movement event for widgets (buttons react to hovering)

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SDK/include/NDK/Canvas.inl

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+// Copyright (C) 2015 Jérôme Leclercq
+// This file is part of the "Nazara Development Kit"
+// For conditions of distribution and use, see copyright notice in Prerequesites.hpp
+
+#include <NDK/Canvas.hpp>
+
+namespace Ndk
+{
+	inline Canvas::Canvas(WorldHandle world, Nz::EventHandler& eventHandler) :
+	m_hoveredWidget(nullptr),
+	m_world(std::move(world))
+	{
+		m_canvas = this;
+
+		m_mouseMovedSlot.Connect(eventHandler.OnMouseMoved, this, &Canvas::OnMouseMoved);
+	}
+
+	inline const WorldHandle& Canvas::GetWorld() const
+	{
+		return m_world;
+	}
+}