Make the viewport able to return the tile of a given index.

src/tileiterator.cpp

@@ -66,7 +66,7 @@ namespace curry {
 	ScreenTile TileIterator::dereference() const {
 		auto index = vector_cast<vec2us>(m_index);
 		return ScreenTile {
-			m_viewport->world()->tile(index),
+			m_viewport->tile(index),
 			m_pixel_pos
 		};
 	}

src/worldviewport.cpp

@@ -1,8 +1,21 @@
 #include "worldviewport.hpp"
 #include "worldgrid.hpp"
+#include "compatibility.h"
 #include <cassert>
 
 namespace curry {
+	namespace {
+		vec2us starting_index (const WorldViewport& parViewport) a_pure;
+
+		vec2us starting_index (const WorldViewport& parViewport) {
+			const auto pos = vector_cast<vec2i>(parViewport.position());
+			const auto ts = parViewport.world()->tile_size();
+			return vec2us(
+				static_cast<uint16_t>(pos.x() / ts.x()),
+				static_cast<uint16_t>(pos.y() / ts.y())
+			);
+		}
+	} //unnamed namespace
 	WorldViewport::WorldViewport (WorldGrid* parWorld, vec2f parSize) :
 		m_position(0),
 		m_size(parSize),
@@ -34,4 +47,8 @@ namespace curry {
 	void WorldViewport::set_position (const vec2f& parPos) {
 		m_position = parPos; //TODO: assert validity
 	}
+
+	WorldViewport::TileIndex WorldViewport::tile (const vec2us& parIndex) const {
+		return world()->tile(parIndex + starting_index(*this));
+	}
 } //namespace curry

src/worldviewport.hpp

@@ -9,11 +9,13 @@ namespace curry {
 	class WorldViewport {
 	public:
 		typedef TileIterator iterator;
+		typedef int TileIndex;
 
 		WorldViewport (WorldGrid* parWorld, vec2f parSize);
 		const WorldGrid* world() const;
 		const vec2f& position() const;
 		const vec2f& size() const;
+		TileIndex tile (const vec2us& parIndex) const;
 
 		void set_position (const vec2f& parPos);