src/gpu/GrDrawOpAtlas.h - platform/external/skia - Gitiles

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #ifndef GrDrawOpAtlas_DEFINED
 #define GrDrawOpAtlas_DEFINED

 #include <cmath>

 #include "include/core/SkSize.h"
 #include "include/private/SkTDArray.h"
 #include "src/core/SkGlyphRunPainter.h"
 #include "src/core/SkIPoint16.h"
 #include "src/core/SkTInternalLList.h"

 #include "src/gpu/ops/GrDrawOp.h"

 class GrOnFlushResourceProvider;
 class GrRectanizer;


 /**
  * This class manages one or more atlas textures on behalf of GrDrawOps. The draw ops that use the
  * atlas perform texture uploads when preparing their draws during flush. The class provides
  * facilities for using GrDrawOpUploadToken to detect data hazards. Op's uploads are performed in
  * "ASAP" mode until it is impossible to add data without overwriting texels read by draws that
  * have not yet executed on the gpu. At that point, the atlas will attempt to allocate a new
  * atlas texture (or "page") of the same size, up to a maximum number of textures, and upload
  * to that texture. If that's not possible, the uploads are performed "inline" between draws. If a
  * single draw would use enough subimage space to overflow the atlas texture then the atlas will
  * fail to add a subimage. This gives the op the chance to end the draw and begin a new one.
  * Additional uploads will then succeed in inline mode.
  *
  * When the atlas has multiple pages, new uploads are prioritized to the lower index pages, i.e.,
  * it will try to upload to page 0 before page 1 or 2. To keep the atlas from continually using
  * excess space, periodic garbage collection is needed to shift data from the higher index pages to
  * the lower ones, and then eventually remove any pages that are no longer in use. "In use" is
  * determined by using the GrDrawUploadToken system: After a flush each subarea of the page
  * is checked to see whether it was used in that flush; if it is not, a counter is incremented.
  * Once that counter reaches a threshold that subarea is considered to be no longer in use.
  *
  * Garbage collection is initiated by the GrDrawOpAtlas's client via the compact() method. One
  * solution is to make the client a subclass of GrOnFlushCallbackObject, register it with the
  * GrContext via addOnFlushCallbackObject(), and the client's postFlush() method calls compact()
  * and passes in the given GrDrawUploadToken.
  */
 class GrDrawOpAtlas {
 private:
     static constexpr auto kMaxMultitexturePages = 4;


 public:
     /** Is the atlas allowed to use more than one texture? */
     enum class AllowMultitexturing : bool { kNo, kYes };

     static constexpr int kMaxPlots = 32; // restricted by the fPlotAlreadyUpdated bitfield
                                          // in BulkUseTokenUpdater

     /**
      * An AtlasID is an opaque handle which callers can use to determine if the atlas contains
      * a specific piece of data.
      */
     typedef uint64_t AtlasID;
     static const uint32_t kInvalidAtlasID = 0;
     static const uint64_t kInvalidAtlasGeneration = 0;

     /**
      * A function pointer for use as a callback during eviction. Whenever GrDrawOpAtlas evicts a
      * specific AtlasID, it will call all of the registered listeners so they can process the
      * eviction.
      */
     typedef void (*EvictionFunc)(GrDrawOpAtlas::AtlasID, void*);

     /**
      * Returns a GrDrawOpAtlas. This function can be called anywhere, but the returned atlas
      * should only be used inside of GrMeshDrawOp::onPrepareDraws.
      *  @param GrColorType      The colorType which this atlas will store
      *  @param width            width in pixels of the atlas
      *  @param height           height in pixels of the atlas
      *  @param numPlotsX        The number of plots the atlas should be broken up into in the X
      *                          direction
      *  @param numPlotsY        The number of plots the atlas should be broken up into in the Y
      *                          direction
      *  @param allowMultitexturing Can the atlas use more than one texture.
      *  @param func             An eviction function which will be called whenever the atlas has to
      *                          evict data
      *  @param data             User supplied data which will be passed into func whenever an
      *                          eviction occurs
      *  @return                 An initialized GrDrawOpAtlas, or nullptr if creation fails
      */
     static std::unique_ptr<GrDrawOpAtlas> Make(GrProxyProvider*,
                                                const GrBackendFormat& format,
                                                GrColorType,
                                                int width, int height,
                                                int plotWidth, int plotHeight,
                                                AllowMultitexturing allowMultitexturing,
                                                GrDrawOpAtlas::EvictionFunc func, void* data);

     /**
      * Packs a texture atlas index into the signed int16 texture coordinates.
      *  @param u      U texture coordinate
      *  @param v      V texture coordinate
      *  @param texIndex           index of the texture these coordinates apply to. Must be in the range [0, 3].
      *  @return                 The new u and v coordinates with the packed value
      */
     static std::pair<int16_t, int16_t> PackIndexInTexCoords(int16_t u, int16_t v, int texIndex);

     /**
      * Unpacks a texture atlas index from signed int16 texture coordinates.
      *  @param u      Packed U texture coordinate
      *  @param v      Packed V texture coordinate
      *  @return    The unpacked u and v coordinates with the texture index.
      */
     static std::tuple<int16_t, int16_t, int> UnpackIndexFromTexCoords(int16_t u, int16_t v);

     // Maximum texture size that can be used for atlases.
     // On lower-end GPUs texture coordinates end up being half floats, which means we only
     // have enough precision to represent 2048 texels.
     static constexpr int kMaxTextureSize = 2048;

     /**
      * Adds a width x height subimage to the atlas. Upon success it returns 'kSucceeded' and returns
      * the ID and the subimage's coordinates in the backing texture. 'kTryAgain' is returned if
      * the subimage cannot fit in the atlas without overwriting texels that will be read in the
      * current draw. This indicates that the op should end its current draw and begin another
      * before adding more data. Upon success, an upload of the provided image data will have
      * been added to the GrDrawOp::Target, in "asap" mode if possible, otherwise in "inline" mode.
      * Successive uploads in either mode may be consolidated.
      * 'kError' will be returned when some unrecoverable error was encountered while trying to
      * add the subimage. In this case the op being created should be discarded.
      *
      * NOTE: When the GrDrawOp prepares a draw that reads from the atlas, it must immediately call
      * 'setUseToken' with the currentToken from the GrDrawOp::Target, otherwise the next call to
      * addToAtlas might cause the previous data to be overwritten before it has been read.
      */

     enum class ErrorCode {
         kError,
         kSucceeded,
         kTryAgain
     };

     ErrorCode addToAtlas(GrResourceProvider*, AtlasID*, GrDeferredUploadTarget*,
                          int width, int height,
                          const void* image, SkIPoint16* loc);

     const GrSurfaceProxyView* getViews() const { return fViews; }

     uint64_t atlasGeneration() const { return fAtlasGeneration; }

     inline bool hasID(AtlasID id) {
         if (kInvalidAtlasID == id) {
             return false;
         }
         uint32_t plot = GetPlotIndexFromID(id);
         SkASSERT(plot < fNumPlots);
         uint32_t page = GetPageIndexFromID(id);
         SkASSERT(page < fNumActivePages);
         return fPages[page].fPlotArray[plot]->genID() == GetGenerationFromID(id);
     }

     /** To ensure the atlas does not evict a given entry, the client must set the last use token. */
     inline void setLastUseToken(AtlasID id, GrDeferredUploadToken token) {
         SkASSERT(this->hasID(id));
         uint32_t plotIdx = GetPlotIndexFromID(id);
         SkASSERT(plotIdx < fNumPlots);
         uint32_t pageIdx = GetPageIndexFromID(id);
         SkASSERT(pageIdx < fNumActivePages);
         Plot* plot = fPages[pageIdx].fPlotArray[plotIdx].get();
         this->makeMRU(plot, pageIdx);
         plot->setLastUseToken(token);
     }

     inline void registerEvictionCallback(EvictionFunc func, void* userData) {
         EvictionData* data = fEvictionCallbacks.append();
         data->fFunc = func;
         data->fData = userData;
     }

     uint32_t numActivePages() { return fNumActivePages; }

     /**
      * A class which can be handed back to GrDrawOpAtlas for updating last use tokens in bulk.  The
      * current max number of plots per page the GrDrawOpAtlas can handle is 32. If in the future
      * this is insufficient then we can move to a 64 bit int.
      */
     class BulkUseTokenUpdater {
     public:
         BulkUseTokenUpdater() {
             memset(fPlotAlreadyUpdated, 0, sizeof(fPlotAlreadyUpdated));
         }
         BulkUseTokenUpdater(const BulkUseTokenUpdater& that)
             : fPlotsToUpdate(that.fPlotsToUpdate) {
             memcpy(fPlotAlreadyUpdated, that.fPlotAlreadyUpdated, sizeof(fPlotAlreadyUpdated));
         }

         bool add(AtlasID id) {
             int index = GrDrawOpAtlas::GetPlotIndexFromID(id);
             int pageIdx = GrDrawOpAtlas::GetPageIndexFromID(id);
             if (this->find(pageIdx, index)) {
                 return false;
             }
             this->set(pageIdx, index);
             return true;
         }

         void reset() {
             fPlotsToUpdate.reset();
             memset(fPlotAlreadyUpdated, 0, sizeof(fPlotAlreadyUpdated));
         }

         struct PlotData {
             PlotData(int pageIdx, int plotIdx) : fPageIndex(pageIdx), fPlotIndex(plotIdx) {}
             uint32_t fPageIndex;
             uint32_t fPlotIndex;
         };

     private:
         bool find(int pageIdx, int index) const {
             SkASSERT(index < kMaxPlots);
             return (fPlotAlreadyUpdated[pageIdx] >> index) & 1;
         }

         void set(int pageIdx, int index) {
             SkASSERT(!this->find(pageIdx, index));
             fPlotAlreadyUpdated[pageIdx] |= (1 << index);
             fPlotsToUpdate.push_back(PlotData(pageIdx, index));
         }

         static constexpr int kMinItems = 4;
         SkSTArray<kMinItems, PlotData, true> fPlotsToUpdate;
         uint32_t fPlotAlreadyUpdated[kMaxMultitexturePages]; // TODO: increase this to uint64_t
                                                              //       to allow more plots per page

         friend class GrDrawOpAtlas;
     };

     void setLastUseTokenBulk(const BulkUseTokenUpdater& updater, GrDeferredUploadToken token) {
         int count = updater.fPlotsToUpdate.count();
         for (int i = 0; i < count; i++) {
             const BulkUseTokenUpdater::PlotData& pd = updater.fPlotsToUpdate[i];
             // it's possible we've added a plot to the updater and subsequently the plot's page
             // was deleted -- so we check to prevent a crash
             if (pd.fPageIndex < fNumActivePages) {
                 Plot* plot = fPages[pd.fPageIndex].fPlotArray[pd.fPlotIndex].get();
                 this->makeMRU(plot, pd.fPageIndex);
                 plot->setLastUseToken(token);
             }
         }
     }

     void compact(GrDeferredUploadToken startTokenForNextFlush);

     static uint32_t GetPageIndexFromID(AtlasID id) {
         return id & 0xff;
     }

     void instantiate(GrOnFlushResourceProvider*);

     uint32_t maxPages() const {
         return fMaxPages;
     }

     int numAllocated_TestingOnly() const;
     void setMaxPages_TestingOnly(uint32_t maxPages);

 private:
     GrDrawOpAtlas(GrProxyProvider*, const GrBackendFormat& format, GrColorType, int width,
                   int height, int plotWidth, int plotHeight,
                   AllowMultitexturing allowMultitexturing);

     /**
      * The backing GrTexture for a GrDrawOpAtlas is broken into a spatial grid of Plots. The Plots
      * keep track of subimage placement via their GrRectanizer. A Plot manages the lifetime of its
      * data using two tokens, a last use token and a last upload token. Once a Plot is "full" (i.e.
      * there is no room for the new subimage according to the GrRectanizer), it can no longer be
      * used unless the last use of the Plot has already been flushed through to the gpu.
      */
     class Plot : public SkRefCnt {
         SK_DECLARE_INTERNAL_LLIST_INTERFACE(Plot);

     public:
         /** index() is a unique id for the plot relative to the owning GrAtlas and page. */
         uint32_t index() const { return fPlotIndex; }
         /**
          * genID() is incremented when the plot is evicted due to a atlas spill. It is used to know
          * if a particular subimage is still present in the atlas.
          */
         uint64_t genID() const { return fGenID; }
         GrDrawOpAtlas::AtlasID id() const {
             SkASSERT(GrDrawOpAtlas::kInvalidAtlasID != fID);
             return fID;
         }
         SkDEBUGCODE(size_t bpp() const { return fBytesPerPixel; })

         bool addSubImage(int width, int height, const void* image, SkIPoint16* loc);

         /**
          * To manage the lifetime of a plot, we use two tokens. We use the last upload token to
          * know when we can 'piggy back' uploads, i.e. if the last upload hasn't been flushed to
          * the gpu, we don't need to issue a new upload even if we update the cpu backing store. We
          * use lastUse to determine when we can evict a plot from the cache, i.e. if the last use
          * has already flushed through the gpu then we can reuse the plot.
          */
         GrDeferredUploadToken lastUploadToken() const { return fLastUpload; }
         GrDeferredUploadToken lastUseToken() const { return fLastUse; }
         void setLastUploadToken(GrDeferredUploadToken token) { fLastUpload = token; }
         void setLastUseToken(GrDeferredUploadToken token) { fLastUse = token; }

         void uploadToTexture(GrDeferredTextureUploadWritePixelsFn&, GrTextureProxy*);
         void resetRects();

         int flushesSinceLastUsed() { return fFlushesSinceLastUse; }
         void resetFlushesSinceLastUsed() { fFlushesSinceLastUse = 0; }
         void incFlushesSinceLastUsed() { fFlushesSinceLastUse++; }

     private:
         Plot(int pageIndex, int plotIndex, uint64_t genID, int offX, int offY,
              int width, int height, GrColorType colorType);

         ~Plot() override;

         /**
          * Create a clone of this plot. The cloned plot will take the place of the current plot in
          * the atlas
          */
         Plot* clone() const {
             return new Plot(fPageIndex, fPlotIndex, fGenID + 1, fX, fY, fWidth, fHeight,
                             fColorType);
         }

         static GrDrawOpAtlas::AtlasID CreateId(uint32_t pageIdx, uint32_t plotIdx,
                                                uint64_t generation) {
             SkASSERT(pageIdx < (1 << 8));
             SkASSERT(pageIdx < kMaxMultitexturePages);
             SkASSERT(plotIdx < (1 << 8));
             SkASSERT(generation < ((uint64_t)1 << 48));
             return generation << 16 | plotIdx << 8 | pageIdx;
         }

         GrDeferredUploadToken fLastUpload;
         GrDeferredUploadToken fLastUse;
         // the number of flushes since this plot has been last used
         int                   fFlushesSinceLastUse;

         struct {
             const uint32_t fPageIndex : 16;
             const uint32_t fPlotIndex : 16;
         };
         uint64_t fGenID;
         GrDrawOpAtlas::AtlasID fID;
         unsigned char* fData;
         const int fWidth;
         const int fHeight;
         const int fX;
         const int fY;
         GrRectanizer* fRects;
         const SkIPoint16 fOffset;  // the offset of the plot in the backing texture
         const GrColorType fColorType;
         const size_t fBytesPerPixel;
         SkIRect fDirtyRect;
         SkDEBUGCODE(bool fDirty);

         friend class GrDrawOpAtlas;

         typedef SkRefCnt INHERITED;
     };

     typedef SkTInternalLList<Plot> PlotList;

     static uint32_t GetPlotIndexFromID(AtlasID id) {
         return (id >> 8) & 0xff;
     }

     // top 48 bits are reserved for the generation ID
     static uint64_t GetGenerationFromID(AtlasID id) {
         return (id >> 16) & 0xffffffffffff;
     }

     inline bool updatePlot(GrDeferredUploadTarget*, AtlasID*, Plot*);

     inline void makeMRU(Plot* plot, int pageIdx) {
         if (fPages[pageIdx].fPlotList.head() == plot) {
             return;
         }

         fPages[pageIdx].fPlotList.remove(plot);
         fPages[pageIdx].fPlotList.addToHead(plot);

         // No MRU update for pages -- since we will always try to add from
         // the front and remove from the back there is no need for MRU.
     }

     bool uploadToPage(const GrCaps&, unsigned int pageIdx, AtlasID* id,
                       GrDeferredUploadTarget* target, int width, int height, const void* image,
                       SkIPoint16* loc);

     bool createPages(GrProxyProvider*);
     bool activateNewPage(GrResourceProvider*);
     void deactivateLastPage();

     void processEviction(AtlasID);
     inline void processEvictionAndResetRects(Plot* plot) {
         this->processEviction(plot->id());
         plot->resetRects();
     }

     GrBackendFormat       fFormat;
     GrColorType           fColorType;
     int                   fTextureWidth;
     int                   fTextureHeight;
     int                   fPlotWidth;
     int                   fPlotHeight;
     unsigned int          fNumPlots;

     uint64_t              fAtlasGeneration;
     // nextTokenToFlush() value at the end of the previous flush
     GrDeferredUploadToken fPrevFlushToken;

     struct EvictionData {
         EvictionFunc fFunc;
         void* fData;
     };

     SkTDArray<EvictionData> fEvictionCallbacks;

     struct Page {
         // allocated array of Plots
         std::unique_ptr<sk_sp<Plot>[]> fPlotArray;
         // LRU list of Plots (MRU at head - LRU at tail)
         PlotList fPlotList;
     };
     // proxies kept separate to make it easier to pass them up to client
     GrSurfaceProxyView fViews[kMaxMultitexturePages];
     Page fPages[kMaxMultitexturePages];
     uint32_t fMaxPages;

     uint32_t fNumActivePages;
 };

 // There are three atlases (A8, 565, ARGB) that are kept in relation with one another. In
 // general, the A8 dimensions are 2x the 565 and ARGB dimensions with the constraint that an atlas
 // size will always contain at least one plot. Since the ARGB atlas takes the most space, its
 // dimensions are used to size the other two atlases.
 class GrDrawOpAtlasConfig {
 public:
     // The capabilities of the GPU define maxTextureSize. The client provides maxBytes, and this
     // represents the largest they want a single atlas texture to be. Due to multitexturing, we
     // may expand temporarily to use more space as needed.
     GrDrawOpAtlasConfig(int maxTextureSize, size_t maxBytes);

     // For testing only - make minimum sized atlases -- a single plot for ARGB, four for A8
     GrDrawOpAtlasConfig() : GrDrawOpAtlasConfig(kMaxAtlasDim, 0) {}

     SkISize atlasDimensions(GrMaskFormat type) const;
     SkISize plotDimensions(GrMaskFormat type) const;

 private:
     // On some systems texture coordinates are represented using half-precision floating point,
     // which limits the largest atlas dimensions to 2048x2048.
     // For simplicity we'll use this constraint for all of our atlas textures.
     // This can be revisited later if we need larger atlases.
     static constexpr int kMaxAtlasDim = 2048;

     SkISize fARGBDimensions;
     int     fMaxTextureSize;
 };

 #endif
	/*
	* Copyright 2015 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#ifndef GrDrawOpAtlas_DEFINED
	#define GrDrawOpAtlas_DEFINED

	#include <cmath>

	#include "include/core/SkSize.h"
	#include "include/private/SkTDArray.h"
	#include "src/core/SkGlyphRunPainter.h"
	#include "src/core/SkIPoint16.h"
	#include "src/core/SkTInternalLList.h"

	#include "src/gpu/ops/GrDrawOp.h"

	class GrOnFlushResourceProvider;
	class GrRectanizer;


	/**
	* This class manages one or more atlas textures on behalf of GrDrawOps. The draw ops that use the
	* atlas perform texture uploads when preparing their draws during flush. The class provides
	* facilities for using GrDrawOpUploadToken to detect data hazards. Op's uploads are performed in
	* "ASAP" mode until it is impossible to add data without overwriting texels read by draws that
	* have not yet executed on the gpu. At that point, the atlas will attempt to allocate a new
	* atlas texture (or "page") of the same size, up to a maximum number of textures, and upload
	* to that texture. If that's not possible, the uploads are performed "inline" between draws. If a
	* single draw would use enough subimage space to overflow the atlas texture then the atlas will
	* fail to add a subimage. This gives the op the chance to end the draw and begin a new one.
	* Additional uploads will then succeed in inline mode.
	*
	* When the atlas has multiple pages, new uploads are prioritized to the lower index pages, i.e.,
	* it will try to upload to page 0 before page 1 or 2. To keep the atlas from continually using
	* excess space, periodic garbage collection is needed to shift data from the higher index pages to
	* the lower ones, and then eventually remove any pages that are no longer in use. "In use" is
	* determined by using the GrDrawUploadToken system: After a flush each subarea of the page
	* is checked to see whether it was used in that flush; if it is not, a counter is incremented.
	* Once that counter reaches a threshold that subarea is considered to be no longer in use.
	*
	* Garbage collection is initiated by the GrDrawOpAtlas's client via the compact() method. One
	* solution is to make the client a subclass of GrOnFlushCallbackObject, register it with the
	* GrContext via addOnFlushCallbackObject(), and the client's postFlush() method calls compact()
	* and passes in the given GrDrawUploadToken.
	*/
	class GrDrawOpAtlas {
	private:
	static constexpr auto kMaxMultitexturePages = 4;


	public:
	/** Is the atlas allowed to use more than one texture? */
	enum class AllowMultitexturing : bool { kNo, kYes };

	static constexpr int kMaxPlots = 32; // restricted by the fPlotAlreadyUpdated bitfield
	// in BulkUseTokenUpdater

	/**
	* An AtlasID is an opaque handle which callers can use to determine if the atlas contains
	* a specific piece of data.
	*/
	typedef uint64_t AtlasID;
	static const uint32_t kInvalidAtlasID = 0;
	static const uint64_t kInvalidAtlasGeneration = 0;

	/**
	* A function pointer for use as a callback during eviction. Whenever GrDrawOpAtlas evicts a
	* specific AtlasID, it will call all of the registered listeners so they can process the
	* eviction.
	*/
	typedef void (EvictionFunc)(GrDrawOpAtlas::AtlasID, void);

	/**
	* Returns a GrDrawOpAtlas. This function can be called anywhere, but the returned atlas
	* should only be used inside of GrMeshDrawOp::onPrepareDraws.
	* @param GrColorType The colorType which this atlas will store
	* @param width width in pixels of the atlas
	* @param height height in pixels of the atlas
	* @param numPlotsX The number of plots the atlas should be broken up into in the X
	* direction
	* @param numPlotsY The number of plots the atlas should be broken up into in the Y
	* direction
	* @param allowMultitexturing Can the atlas use more than one texture.
	* @param func An eviction function which will be called whenever the atlas has to
	* evict data
	* @param data User supplied data which will be passed into func whenever an
	* eviction occurs
	* @return An initialized GrDrawOpAtlas, or nullptr if creation fails
	*/
	static std::unique_ptr<GrDrawOpAtlas> Make(GrProxyProvider*,
	const GrBackendFormat& format,
	GrColorType,
	int width, int height,
	int plotWidth, int plotHeight,
	AllowMultitexturing allowMultitexturing,
	GrDrawOpAtlas::EvictionFunc func, void* data);

	/**
	* Packs a texture atlas index into the signed int16 texture coordinates.
	* @param u U texture coordinate
	* @param v V texture coordinate
	* @param texIndex index of the texture these coordinates apply to. Must be in the range [0, 3].
	* @return The new u and v coordinates with the packed value
	*/
	static std::pair<int16_t, int16_t> PackIndexInTexCoords(int16_t u, int16_t v, int texIndex);

	/**
	* Unpacks a texture atlas index from signed int16 texture coordinates.
	* @param u Packed U texture coordinate
	* @param v Packed V texture coordinate
	* @return The unpacked u and v coordinates with the texture index.
	*/
	static std::tuple<int16_t, int16_t, int> UnpackIndexFromTexCoords(int16_t u, int16_t v);

	// Maximum texture size that can be used for atlases.
	// On lower-end GPUs texture coordinates end up being half floats, which means we only
	// have enough precision to represent 2048 texels.
	static constexpr int kMaxTextureSize = 2048;

	/**
	* Adds a width x height subimage to the atlas. Upon success it returns 'kSucceeded' and returns
	* the ID and the subimage's coordinates in the backing texture. 'kTryAgain' is returned if
	* the subimage cannot fit in the atlas without overwriting texels that will be read in the
	* current draw. This indicates that the op should end its current draw and begin another
	* before adding more data. Upon success, an upload of the provided image data will have
	* been added to the GrDrawOp::Target, in "asap" mode if possible, otherwise in "inline" mode.
	* Successive uploads in either mode may be consolidated.
	* 'kError' will be returned when some unrecoverable error was encountered while trying to
	* add the subimage. In this case the op being created should be discarded.
	*
	* NOTE: When the GrDrawOp prepares a draw that reads from the atlas, it must immediately call
	* 'setUseToken' with the currentToken from the GrDrawOp::Target, otherwise the next call to
	* addToAtlas might cause the previous data to be overwritten before it has been read.
	*/

	enum class ErrorCode {
	kError,
	kSucceeded,
	kTryAgain
	};

	ErrorCode addToAtlas(GrResourceProvider, AtlasID, GrDeferredUploadTarget*,
	int width, int height,
	const void* image, SkIPoint16* loc);

	const GrSurfaceProxyView* getViews() const { return fViews; }

	uint64_t atlasGeneration() const { return fAtlasGeneration; }

	inline bool hasID(AtlasID id) {
	if (kInvalidAtlasID == id) {
	return false;
	}
	uint32_t plot = GetPlotIndexFromID(id);
	SkASSERT(plot < fNumPlots);
	uint32_t page = GetPageIndexFromID(id);
	SkASSERT(page < fNumActivePages);
	return fPages[page].fPlotArray[plot]->genID() == GetGenerationFromID(id);
	}

	/** To ensure the atlas does not evict a given entry, the client must set the last use token. */
	inline void setLastUseToken(AtlasID id, GrDeferredUploadToken token) {
	SkASSERT(this->hasID(id));
	uint32_t plotIdx = GetPlotIndexFromID(id);
	SkASSERT(plotIdx < fNumPlots);
	uint32_t pageIdx = GetPageIndexFromID(id);
	SkASSERT(pageIdx < fNumActivePages);
	Plot* plot = fPages[pageIdx].fPlotArray[plotIdx].get();
	this->makeMRU(plot, pageIdx);
	plot->setLastUseToken(token);
	}

	inline void registerEvictionCallback(EvictionFunc func, void* userData) {
	EvictionData* data = fEvictionCallbacks.append();
	data->fFunc = func;
	data->fData = userData;
	}

	uint32_t numActivePages() { return fNumActivePages; }

	/**
	* A class which can be handed back to GrDrawOpAtlas for updating last use tokens in bulk. The
	* current max number of plots per page the GrDrawOpAtlas can handle is 32. If in the future
	* this is insufficient then we can move to a 64 bit int.
	*/
	class BulkUseTokenUpdater {
	public:
	BulkUseTokenUpdater() {
	memset(fPlotAlreadyUpdated, 0, sizeof(fPlotAlreadyUpdated));
	}
	BulkUseTokenUpdater(const BulkUseTokenUpdater& that)
	: fPlotsToUpdate(that.fPlotsToUpdate) {
	memcpy(fPlotAlreadyUpdated, that.fPlotAlreadyUpdated, sizeof(fPlotAlreadyUpdated));
	}

	bool add(AtlasID id) {
	int index = GrDrawOpAtlas::GetPlotIndexFromID(id);
	int pageIdx = GrDrawOpAtlas::GetPageIndexFromID(id);
	if (this->find(pageIdx, index)) {
	return false;
	}
	this->set(pageIdx, index);
	return true;
	}

	void reset() {
	fPlotsToUpdate.reset();
	memset(fPlotAlreadyUpdated, 0, sizeof(fPlotAlreadyUpdated));
	}

	struct PlotData {
	PlotData(int pageIdx, int plotIdx) : fPageIndex(pageIdx), fPlotIndex(plotIdx) {}
	uint32_t fPageIndex;
	uint32_t fPlotIndex;
	};

	private:
	bool find(int pageIdx, int index) const {
	SkASSERT(index < kMaxPlots);
	return (fPlotAlreadyUpdated[pageIdx] >> index) & 1;
	}

	void set(int pageIdx, int index) {
	SkASSERT(!this->find(pageIdx, index));
	fPlotAlreadyUpdated[pageIdx] \|= (1 << index);
	fPlotsToUpdate.push_back(PlotData(pageIdx, index));
	}

	static constexpr int kMinItems = 4;
	SkSTArray<kMinItems, PlotData, true> fPlotsToUpdate;
	uint32_t fPlotAlreadyUpdated[kMaxMultitexturePages]; // TODO: increase this to uint64_t
	// to allow more plots per page

	friend class GrDrawOpAtlas;
	};

	void setLastUseTokenBulk(const BulkUseTokenUpdater& updater, GrDeferredUploadToken token) {
	int count = updater.fPlotsToUpdate.count();
	for (int i = 0; i < count; i++) {
	const BulkUseTokenUpdater::PlotData& pd = updater.fPlotsToUpdate[i];
	// it's possible we've added a plot to the updater and subsequently the plot's page
	// was deleted -- so we check to prevent a crash
	if (pd.fPageIndex < fNumActivePages) {
	Plot* plot = fPages[pd.fPageIndex].fPlotArray[pd.fPlotIndex].get();
	this->makeMRU(plot, pd.fPageIndex);
	plot->setLastUseToken(token);
	}
	}
	}

	void compact(GrDeferredUploadToken startTokenForNextFlush);

	static uint32_t GetPageIndexFromID(AtlasID id) {
	return id & 0xff;
	}

	void instantiate(GrOnFlushResourceProvider*);

	uint32_t maxPages() const {
	return fMaxPages;
	}

	int numAllocated_TestingOnly() const;
	void setMaxPages_TestingOnly(uint32_t maxPages);

	private:
	GrDrawOpAtlas(GrProxyProvider*, const GrBackendFormat& format, GrColorType, int width,
	int height, int plotWidth, int plotHeight,
	AllowMultitexturing allowMultitexturing);

	/**
	* The backing GrTexture for a GrDrawOpAtlas is broken into a spatial grid of Plots. The Plots
	* keep track of subimage placement via their GrRectanizer. A Plot manages the lifetime of its
	* data using two tokens, a last use token and a last upload token. Once a Plot is "full" (i.e.
	* there is no room for the new subimage according to the GrRectanizer), it can no longer be
	* used unless the last use of the Plot has already been flushed through to the gpu.
	*/
	class Plot : public SkRefCnt {
	SK_DECLARE_INTERNAL_LLIST_INTERFACE(Plot);

	public:
	/** index() is a unique id for the plot relative to the owning GrAtlas and page. */
	uint32_t index() const { return fPlotIndex; }
	/**
	* genID() is incremented when the plot is evicted due to a atlas spill. It is used to know
	* if a particular subimage is still present in the atlas.
	*/
	uint64_t genID() const { return fGenID; }
	GrDrawOpAtlas::AtlasID id() const {
	SkASSERT(GrDrawOpAtlas::kInvalidAtlasID != fID);
	return fID;
	}
	SkDEBUGCODE(size_t bpp() const { return fBytesPerPixel; })

	bool addSubImage(int width, int height, const void* image, SkIPoint16* loc);

	/**
	* To manage the lifetime of a plot, we use two tokens. We use the last upload token to
	* know when we can 'piggy back' uploads, i.e. if the last upload hasn't been flushed to
	* the gpu, we don't need to issue a new upload even if we update the cpu backing store. We
	* use lastUse to determine when we can evict a plot from the cache, i.e. if the last use
	* has already flushed through the gpu then we can reuse the plot.
	*/
	GrDeferredUploadToken lastUploadToken() const { return fLastUpload; }
	GrDeferredUploadToken lastUseToken() const { return fLastUse; }
	void setLastUploadToken(GrDeferredUploadToken token) { fLastUpload = token; }
	void setLastUseToken(GrDeferredUploadToken token) { fLastUse = token; }

	void uploadToTexture(GrDeferredTextureUploadWritePixelsFn&, GrTextureProxy*);
	void resetRects();

	int flushesSinceLastUsed() { return fFlushesSinceLastUse; }
	void resetFlushesSinceLastUsed() { fFlushesSinceLastUse = 0; }
	void incFlushesSinceLastUsed() { fFlushesSinceLastUse++; }

	private:
	Plot(int pageIndex, int plotIndex, uint64_t genID, int offX, int offY,
	int width, int height, GrColorType colorType);

	~Plot() override;

	/**
	* Create a clone of this plot. The cloned plot will take the place of the current plot in
	* the atlas
	*/
	Plot* clone() const {
	return new Plot(fPageIndex, fPlotIndex, fGenID + 1, fX, fY, fWidth, fHeight,
	fColorType);
	}

	static GrDrawOpAtlas::AtlasID CreateId(uint32_t pageIdx, uint32_t plotIdx,
	uint64_t generation) {
	SkASSERT(pageIdx < (1 << 8));
	SkASSERT(pageIdx < kMaxMultitexturePages);
	SkASSERT(plotIdx < (1 << 8));
	SkASSERT(generation < ((uint64_t)1 << 48));
	return generation << 16 \| plotIdx << 8 \| pageIdx;
	}

	GrDeferredUploadToken fLastUpload;
	GrDeferredUploadToken fLastUse;
	// the number of flushes since this plot has been last used
	int fFlushesSinceLastUse;

	struct {
	const uint32_t fPageIndex : 16;
	const uint32_t fPlotIndex : 16;
	};
	uint64_t fGenID;
	GrDrawOpAtlas::AtlasID fID;
	unsigned char* fData;
	const int fWidth;
	const int fHeight;
	const int fX;
	const int fY;
	GrRectanizer* fRects;
	const SkIPoint16 fOffset; // the offset of the plot in the backing texture
	const GrColorType fColorType;
	const size_t fBytesPerPixel;
	SkIRect fDirtyRect;
	SkDEBUGCODE(bool fDirty);

	friend class GrDrawOpAtlas;

	typedef SkRefCnt INHERITED;
	};

	typedef SkTInternalLList<Plot> PlotList;

	static uint32_t GetPlotIndexFromID(AtlasID id) {
	return (id >> 8) & 0xff;
	}

	// top 48 bits are reserved for the generation ID
	static uint64_t GetGenerationFromID(AtlasID id) {
	return (id >> 16) & 0xffffffffffff;
	}

	inline bool updatePlot(GrDeferredUploadTarget, AtlasID, Plot*);

	inline void makeMRU(Plot* plot, int pageIdx) {
	if (fPages[pageIdx].fPlotList.head() == plot) {
	return;
	}

	fPages[pageIdx].fPlotList.remove(plot);
	fPages[pageIdx].fPlotList.addToHead(plot);

	// No MRU update for pages -- since we will always try to add from
	// the front and remove from the back there is no need for MRU.
	}

	bool uploadToPage(const GrCaps&, unsigned int pageIdx, AtlasID* id,
	GrDeferredUploadTarget* target, int width, int height, const void* image,
	SkIPoint16* loc);

	bool createPages(GrProxyProvider*);
	bool activateNewPage(GrResourceProvider*);
	void deactivateLastPage();

	void processEviction(AtlasID);
	inline void processEvictionAndResetRects(Plot* plot) {
	this->processEviction(plot->id());
	plot->resetRects();
	}

	GrBackendFormat fFormat;
	GrColorType fColorType;
	int fTextureWidth;
	int fTextureHeight;
	int fPlotWidth;
	int fPlotHeight;
	unsigned int fNumPlots;

	uint64_t fAtlasGeneration;
	// nextTokenToFlush() value at the end of the previous flush
	GrDeferredUploadToken fPrevFlushToken;

	struct EvictionData {
	EvictionFunc fFunc;
	void* fData;
	};

	SkTDArray<EvictionData> fEvictionCallbacks;

	struct Page {
	// allocated array of Plots
	std::unique_ptr<sk_sp<Plot>[]> fPlotArray;
	// LRU list of Plots (MRU at head - LRU at tail)
	PlotList fPlotList;
	};
	// proxies kept separate to make it easier to pass them up to client
	GrSurfaceProxyView fViews[kMaxMultitexturePages];
	Page fPages[kMaxMultitexturePages];
	uint32_t fMaxPages;

	uint32_t fNumActivePages;
	};

	// There are three atlases (A8, 565, ARGB) that are kept in relation with one another. In
	// general, the A8 dimensions are 2x the 565 and ARGB dimensions with the constraint that an atlas
	// size will always contain at least one plot. Since the ARGB atlas takes the most space, its
	// dimensions are used to size the other two atlases.
	class GrDrawOpAtlasConfig {
	public:
	// The capabilities of the GPU define maxTextureSize. The client provides maxBytes, and this
	// represents the largest they want a single atlas texture to be. Due to multitexturing, we
	// may expand temporarily to use more space as needed.
	GrDrawOpAtlasConfig(int maxTextureSize, size_t maxBytes);

	// For testing only - make minimum sized atlases -- a single plot for ARGB, four for A8
	GrDrawOpAtlasConfig() : GrDrawOpAtlasConfig(kMaxAtlasDim, 0) {}

	SkISize atlasDimensions(GrMaskFormat type) const;
	SkISize plotDimensions(GrMaskFormat type) const;

	private:
	// On some systems texture coordinates are represented using half-precision floating point,
	// which limits the largest atlas dimensions to 2048x2048.
	// For simplicity we'll use this constraint for all of our atlas textures.
	// This can be revisited later if we need larger atlases.
	static constexpr int kMaxAtlasDim = 2048;

	SkISize fARGBDimensions;
	int fMaxTextureSize;
	};

	#endif