namespace dk {
	template <size_t D>
	Viewport<D>::Viewport (Tyler<D>& parTyler) :
		m_tyler(parTyler)
	{
	}

	template <size_t D>
	Viewport<D>::Viewport (Tyler<D>& parTyler, const coords& parSize, const coords& parPos) :
		m_size(parSize),
		m_position(parPos),
		m_tyler(parTyler)
	{
		DK_ASSERT(parPos <= parPos + parSize);
		DK_ASSERT(parSize + parPos <= parTyler.map_size());
		m_tyler.preload(m_position, m_position + m_size);
	}

	template <size_t D>
	template <typename T>
	typename Layer<T, D>::iterator Viewport<D>::begin (Layer<T, D>& parLayer) const {
		typedef typename Layer<T, D>::iterator IterType;

		return IterType(&parLayer.m_tiles, m_position, m_position + m_size);
	}

	template <size_t D>
	template <typename T>
	typename Layer<T, D>::iterator Viewport<D>::end (Layer<T, D>& parLayer) const {
		typedef typename Layer<T, D>::iterator IterType;

		const auto to(m_position + m_size);
		return IterType(&parLayer.m_tiles, implem::buildPastEndCoordinate(m_position, to), to);
	}

	template <size_t D>
	void Viewport<D>::setSize (const coords& parSize) {
		DK_ASSERT(m_position <= m_position + parSize);
		DK_ASSERT(parSize + m_position <= m_tyler.map_size());
		m_size = parSize;
		m_tyler.preload(m_position, m_position + m_size);
	}

	template <size_t D>
	void Viewport<D>::setFrom (const coords& parFrom) {
		DK_ASSERT(parFrom <= parFrom + m_size);
		DK_ASSERT(m_size + parFrom <= m_tyler.map_size());
		m_position = parFrom;
		m_tyler.preload(m_position, m_position + m_size);
	}

	template <size_t D>
	void Viewport<D>::setFromSize (const coords& parFrom, const coords& parSize) {
		DK_ASSERT(parFrom <= parFrom + parSize);
		DK_ASSERT(parSize + parFrom <= m_tyler.map_size());
		m_position = parFrom;
		m_size = parSize;
		m_tyler.preload(m_position, m_position + m_size);
	}
} //namespace dk