DtGlTextureResidencyManager.h

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/******************************************************************************
** Copyright (c) 2021 MAK Technologies, Inc.
** All rights reserved.
******************************************************************************/


#pragma once
#include <vrvGraphicsUtils/vrvGraphicsUtils.h>

#include <map>
#include <unordered_map>

namespace makVrv
{
   class DtGlTextureResidentMemoryTracker;

   class DT_DLL_VRVGRAPHICSUTILS DtGlTextureResidencyManager
   {
   public:
      typedef std::map<unsigned int, int> TexIDToCount;
      typedef std::map<void*, TexIDToCount> ContextToTexID;

   public:
      DtGlTextureResidencyManager();

      virtual ~DtGlTextureResidencyManager();

      DtGlTextureResidencyManager(const DtGlTextureResidencyManager&) = delete;

      DtGlTextureResidencyManager& operator=(const DtGlTextureResidencyManager&) = delete;

   public:
      virtual void makeResidentIfNecessary(void* gContext, GLuint textureID);

      virtual bool makeNonResidentIfNecessary(void* gContext, GLuint textureID, bool canDelete);

      virtual GLuint64 gpuTextureAddress(GLuint textureID) const;

      virtual bool isTexture(GLuint textureID) const;

      virtual DtGlTextureResidentMemoryTracker* tracker() const;

   protected:
      virtual DtGlTextureResidentMemoryTracker* getOrCreateTracker(void* graphicsContext);
   protected:
      // Count of textures we've made resident *across all contexts*
      // So 1 texture in 3 contexts will have a count of 3
      // When this array goes to 0 then we call glDeleteTextures if the
      // texture is also marked 
      ContextToTexID myTextureCountByContext;

      // So for pageable terrains, the textures can be shared between tiles
      // However, when you releaseGLObjects and say glMakeTextureHandleNonResidentARB, 
      // other tiles which share the texture will not draw or have other problems
      // since we removed the data from underneath them
      // This is a basic (non-thread safe!) reference counting of textures by
      // context ID
      TexIDToCount myTextureIdToRefCountAcrossContexts;

      std::unordered_map<void*, DtGlTextureResidentMemoryTracker*> myContextsToTrackers;
   };
}