BansheeEngine/BansheeCore/Include/BsOcclusionQuery.h

#pragma once

#include "BsCorePrerequisites.h"

namespace BansheeEngine
{
	/**
	* @brief	Represents a query that counts number of samples rendered by the GPU
	*			while the query is active.
	*
	* @note		Core thread only.
	*/
	class BS_CORE_EXPORT OcclusionQuery
	{
	public:
		OcclusionQuery(bool binary);
		virtual ~OcclusionQuery() {}

		/**
		* @brief	Starts the query. Any draw calls after this call will have any rendered samples
		*			counted in the query.
		*
		* @note		Place any commands you want to measure after this call. Call "end" when done.
		*/
		virtual void begin() = 0;

		/**
		* @brief	Stops the query. 
		*
		* @note		Be aware that queries are executed on the GPU and the results will not be immediately available.
		*/
		virtual void end() = 0;

		/**
		* @brief	Check if GPU has processed the query.
		*/
		virtual bool isReady() const = 0;

		/**
		 * @brief	Returns the number of samples that passed the depth and stencil test between
		 *			query start and end.
		 *
		 * @note	If the query is binary, this will return 0 or 1. 1 meaning one or more samples were rendered,
		 *			but will not give you the exact count.
		 */
		virtual UINT32 getNumSamples() = 0;

		/**
		 * @brief	Triggered when the query has completed. Argument provided
		 *			is the number of samples counted by the query.
		 */
		Event<void(UINT32)> onComplete;

		/**
		 * @brief	Creates a new occlusion query. 
		 *
		 * @param binary	If query is binary it will not give you an exact count of samples rendered, but will instead
		 *					just return 0 (no samples were rendered) or 1 (one or more samples were rendered). Binary
		 *					queries can return sooner as they potentially do not need to wait until all of the geometry is rendered.
		 */
		static OcclusionQueryPtr create(bool binary);

	protected:
		friend class QueryManager;

		/**
		* @brief	Returns true if the has still not been completed by the GPU.
		*/
		bool isActive() const { return mActive; }
		void setActive(bool active) { mActive = active; }

	protected:
		bool mActive;
		bool mBinary;
	};
}