text: /*
   * Copyright 2015 Google Inc.
   *
   * Use of this source code is governed by a BSD-style license that can be
   * found in the LICENSE file.
   */
  
  #include "src/gpu/GrDrawOpAtlas.h"
  
  #include "include/gpu/GrContext.h"
  #include "include/gpu/GrTexture.h"
  #include "src/gpu/GrContextPriv.h"
  #include "src/gpu/GrOnFlushResourceProvider.h"
  #include "src/gpu/GrOpFlushState.h"
  #include "src/gpu/GrProxyProvider.h"
  #include "src/gpu/GrRectanizer.h"
  #include "src/gpu/GrResourceProvider.h"
  #include "src/gpu/GrSurfaceProxyPriv.h"
  #include "src/gpu/GrTracing.h"
  
  // When proxy allocation is deferred until flush time the proxies acting as atlases require
  // special handling. This is because the usage that can be determined from the ops themselves
  // isn't sufficient. Independent of the ops there will be ASAP and inline uploads to the
  // atlases. Extending the usage interval of any op that uses an atlas to the start of the
  // flush (as is done for proxies that are used for sw-generated masks) also won't work because
  // the atlas persists even beyond the last use in an op - for a given flush. Given this, atlases
  // must explicitly manage the lifetime of their backing proxies via the onFlushCallback system
  // (which calls this method).
  void GrDrawOpAtlas::instantiate(GrOnFlushResourceProvider* onFlushResourceProvider) {
      for (uint32_t i = 0; i < fNumActivePages; ++i) {
          // All the atlas pages are now instantiated at flush time in the activeNewPage method.
          SkASSERT(fProxies[i] && fProxies[i]->isInstantiated());
      }
  }
  
  std::unique_ptr<GrDrawOpAtlas> GrDrawOpAtlas::Make(GrProxyProvider* proxyProvider,
                                                     const GrBackendFormat& format,
                                                     GrColorType colorType, int width,
                                                     int height, int plotWidth, int plotHeight,
                                                     AllowMultitexturing allowMultitexturing,
                                                     GrDrawOpAtlas::EvictionFunc func, void* data) {
      std::unique_ptr<GrDrawOpAtlas> atlas(new GrDrawOpAtlas(proxyProvider, format, colorType, width,
                                                             height, plotWidth, plotHeight,
                                                             allowMultitexturing));
      if (!atlas->getProxies()[0]) {
          return nullptr;
      }
  
      atlas->registerEvictionCallback(func, data);
      return atlas;
  }
  
  #ifdef DUMP_ATLAS_DATA
  static bool gDumpAtlasData = false;
  #endif
  
  ////////////////////////////////////////////////////////////////////////////////
  GrDrawOpAtlas::Plot::Plot(int pageIndex, int plotIndex, uint64_t genID, int offX, int offY,
                            int width, int height, GrColorType colorType)
          : fLastUpload(GrDeferredUploadToken::AlreadyFlushedToken())
          , fLastUse(GrDeferredUploadToken::AlreadyFlushedToken())
          , fFlushesSinceLastUse(0)
          , fPageIndex(pageIndex)
          , fPlotIndex(plotIndex)
          , fGenID(genID)
          , fID(CreateId(fPageIndex, fPlotIndex, fGenID))
          , fData(nullptr)
          , fWidth(width)
          , fHeight(height)
          , fX(offX)
          , fY(offY)
          , fRects(nullptr)
          , fOffset(SkIPoint16::Make(fX * fWidth, fY * fHeight))
          , fColorType(colorType)
          , fBytesPerPixel(GrColorTypeBytesPerPixel(colorType))
  #ifdef SK_DEBUG
          , fDirty(false)
  #endif
  {
      // We expect the allocated dimensions to be a multiple of 4 bytes
      SkASSERT(((width*fBytesPerPixel) & 0x3) == 0);
      // The padding for faster uploads only works for 1, 2 and 4 byte texels
      SkASSERT(fBytesPerPixel != 3 && fBytesPerPixel <= 4);
      fDirtyRect.setEmpty();
  }
  
  GrDrawOpAtlas::Plot::~Plot() {
      sk_free(fData);
      delete fRects;
  }
  
  bool GrDrawOpAtlas::Plot::addSubImage(int width, int height, const void* image, SkIPoint16* loc) {
      SkASSERT(width <= fWidth && height <= fHeight);
  
      if (!fRects) {
          fRects = GrRectanizer::Factory(fWidth, fHeight);
      }
  
      if (!fRects->addRect(width, height, loc)) {
          return false;
      }
  
      if (!fData) {
          fData = reinterpret_cast<unsigned char*>(sk_calloc_throw(fBytesPerPixel * fWidth *
                                                                   fHeight));
      }
      size_t rowBytes = width * fBytesPerPixel;
      const unsigned char* imagePtr = (const unsigned char*)image;
      // point ourselves at the right starting spot
      unsigned char* dataPtr = fData;
      dataPtr += fBytesPerPixel * fWidth * loc->fY;
      dataPtr += fBytesPerPixel * loc->fX;
      // copy into the data buffer, swizzling as we go if this is ARGB data
      if (4 == fBytesPerPixel && kSkia8888_GrPixelConfig == kBGRA_8888_GrPixelConfig) {
          for (int i = 0; i < height; ++i) {
              SkOpts::RGBA_to_BGRA((uint32_t*)dataPtr, (const uint32_t*)imagePtr, width);
              dataPtr += fBytesPerPixel * fWidth;
              imagePtr += rowBytes;
          }
      } else {
          for (int i = 0; i < height; ++i) {
              memcpy(dataPtr, imagePtr, rowBytes);
              dataPtr += fBytesPerPixel * fWidth;
              imagePtr += rowBytes;
          }
      }
  
      fDirtyRect.join(loc->fX, loc->fY, loc->fX + width, loc->fY + height);
  
      loc->fX += fOffset.fX;
      loc->fY += fOffset.fY;
      SkDEBUGCODE(fDirty = true;)
  
      return true;
  }
  
  void GrDrawOpAtlas::Plot::uploadToTexture(GrDeferredTextureUploadWritePixelsFn& writePixels,
                                            GrTextureProxy* proxy) {
      // We should only be issuing uploads if we are in fact dirty
      SkASSERT(fDirty && fData && proxy && proxy->peekTexture());
      TRACE_EVENT0("skia.gpu", TRACE_FUNC);
      size_t rowBytes = fBytesPerPixel * fWidth;
      const unsigned char* dataPtr = fData;
      // Clamp to 4-byte aligned boundaries
      unsigned int clearBits = 0x3 / fBytesPerPixel;
      fDirtyRect.fLeft &= ~clearBits;
      fDirtyRect.fRight += clearBits;
      fDirtyRect.fRight &= ~clearBits;
      SkASSERT(fDirtyRect.fRight <= fWidth);
      // Set up dataPtr
      dataPtr += rowBytes * fDirtyRect.fTop;
      dataPtr += fBytesPerPixel * fDirtyRect.fLeft;
  
      writePixels(proxy, fOffset.fX + fDirtyRect.fLeft, fOffset.fY + fDirtyRect.fTop,
                  fDirtyRect.width(), fDirtyRect.height(), fColorType, dataPtr, rowBytes);
      fDirtyRect.setEmpty();
      SkDEBUGCODE(fDirty = false;)
  }
  
  void GrDrawOpAtlas::Plot::resetRects() {
      if (fRects) {
          fRects->reset();
      }
  
      fGenID++;
      fID = CreateId(fPageIndex, fPlotIndex, fGenID);
      fLastUpload = GrDeferredUploadToken::AlreadyFlushedToken();
      fLastUse = GrDeferredUploadToken::AlreadyFlushedToken();
  
      // zero out the plot
      if (fData) {
          sk_bzero(fData, fBytesPerPixel * fWidth * fHeight);
      }
  
      fDirtyRect.setEmpty();
      SkDEBUGCODE(fDirty = false;)
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  
  GrDrawOpAtlas::GrDrawOpAtlas(GrProxyProvider* proxyProvider, const GrBackendFormat& format,
                               GrColorType colorType, int width, int height,
                               int plotWidth, int plotHeight, AllowMultitexturing allowMultitexturing)
          : fFormat(format)
          , fColorType(colorType)
          , fTextureWidth(width)
          , fTextureHeight(height)
          , fPlotWidth(plotWidth)
          , fPlotHeight(plotHeight)
          , fAtlasGeneration(kInvalidAtlasGeneration + 1)
          , fPrevFlushToken(GrDeferredUploadToken::AlreadyFlushedToken())
          , fMaxPages(AllowMultitexturing::kYes == allowMultitexturing ? kMaxMultitexturePages : 1)
          , fNumActivePages(0) {
      int numPlotsX = width/plotWidth;
      int numPlotsY = height/plotHeight;
      SkASSERT(numPlotsX * numPlotsY <= GrDrawOpAtlas::kMaxPlots);
      SkASSERT(fPlotWidth * numPlotsX == fTextureWidth);
      SkASSERT(fPlotHeight * numPlotsY == fTextureHeight);
  
      fNumPlots = numPlotsX * numPlotsY;
  
      this->createPages(proxyProvider);
  }
  
  inline void GrDrawOpAtlas::processEviction(AtlasID id) {
      for (int i = 0; i < fEvictionCallbacks.count(); i++) {
          (*fEvictionCallbacks[i].fFunc)(id, fEvictionCallbacks[i].fData);
      }
      ++fAtlasGeneration;
  }
  
  inline bool GrDrawOpAtlas::updatePlot(GrDeferredUploadTarget* target, AtlasID* id, Plot* plot) {
      int pageIdx = GetPageIndexFromID(plot->id());
      this->makeMRU(plot, pageIdx);
  
      // If our most recent upload has already occurred then we have to insert a new
      // upload. Otherwise, we already have a scheduled upload that hasn't yet ocurred.
      // This new update will piggy back on that previously scheduled update.
      if (plot->lastUploadToken() < target->tokenTracker()->nextTokenToFlush()) {
          // With c+14 we could move sk_sp into lamba to only ref once.
          sk_sp<Plot> plotsp(SkRef(plot));
  
          GrTextureProxy* proxy = fProxies[pageIdx].get();
          SkASSERT(proxy->isInstantiated());  // This is occurring at flush time
  
          GrDeferredUploadToken lastUploadToken = target->addASAPUpload(
                  [plotsp, proxy](GrDeferredTextureUploadWritePixelsFn& writePixels) {
                      plotsp->uploadToTexture(writePixels, proxy);
                  });
          plot->setLastUploadToken(lastUploadToken);
      }
      *id = plot->id();
      return true;
  }
  
  bool GrDrawOpAtlas::uploadToPage(unsigned int pageIdx, AtlasID* id, GrDeferredUploadTarget* target,
                                   int width, int height, const void* image, SkIPoint16* loc) {
      SkASSERT(fProxies[pageIdx] && fProxies[pageIdx]->isInstantiated());
  
      // look through all allocated plots for one we can share, in Most Recently Refed order
      PlotList::Iter plotIter;
      plotIter.init(fPages[pageIdx].fPlotList, PlotList::Iter::kHead_IterStart);
  
      for (Plot* plot = plotIter.get(); plot; plot = plotIter.next()) {
          SkASSERT(GrBytesPerPixel(fProxies[pageIdx]->config()) == plot->bpp());
  
          if (plot->addSubImage(width, height, image, loc)) {
              return this->updatePlot(target, id, plot);
          }
      }
  
      return false;
  }
  
  // Number of atlas-related flushes beyond which we consider a plot to no longer be in use.
  //
  // This value is somewhat arbitrary -- the idea is to keep it low enough that
  // a page with unused plots will get removed reasonably quickly, but allow it
  // to hang around for a bit in case it's needed. The assumption is that flushes
  // are rare; i.e., we are not continually refreshing the frame.
  static constexpr auto kRecentlyUsedCount = 256;
  
  GrDrawOpAtlas::ErrorCode GrDrawOpAtlas::addToAtlas(GrResourceProvider* resourceProvider,
                                                     AtlasID* id, GrDeferredUploadTarget* target,
                                                     int width, int height,
                                                     const void* image, SkIPoint16* loc) {
      if (width > fPlotWidth || height > fPlotHeight) {
          return ErrorCode::kError;
      }
  
      // Look through each page to see if we can upload without having to flush
      // We prioritize this upload to the first pages, not the most recently used, to make it easier
      // to remove unused pages in reverse page order.
      for (unsigned int pageIdx = 0; pageIdx < fNumActivePages; ++pageIdx) {
          if (this->uploadToPage(pageIdx, id, target, width, height, image, loc)) {
              return ErrorCode::kSucceeded;
          }
      }
  
      // If the above fails, then see if the least recently used plot per page has already been
      // flushed to the gpu if we're at max page allocation, or if the plot has aged out otherwise.
      // We wait until we've grown to the full number of pages to begin evicting already flushed
      // plots so that we can maximize the opportunity for reuse.
      // As before we prioritize this upload to the first pages, not the most recently used.
      if (fNumActivePages == this->maxPages()) {
          for (unsigned int pageIdx = 0; pageIdx < fNumActivePages; ++pageIdx) {
              Plot* plot = fPages[pageIdx].fPlotList.tail();
              SkASSERT(plot);
              if (plot->lastUseToken() < target->tokenTracker()->nextTokenToFlush()) {
                  this->processEvictionAndResetRects(plot);
                  SkASSERT(GrBytesPerPixel(fProxies[pageIdx]->config()) == plot->bpp());
                  SkDEBUGCODE(bool verify = )plot->addSubImage(width, height, image, loc);
                  SkASSERT(verify);
                  if (!this->updatePlot(target, id, plot)) {
                      return ErrorCode::kError;
                  }
                  return ErrorCode::kSucceeded;
              }
          }
      } else {
          // If we haven't activated all the available pages, try to create a new one and add to it
          if (!this->activateNewPage(resourceProvider)) {
              return ErrorCode::kError;
          }
  
          if (this->uploadToPage(fNumActivePages-1, id, target, width, height, image, loc)) {
              return ErrorCode::kSucceeded;
          } else {
              // If we fail to upload to a newly activated page then something has gone terribly
              // wrong - return an error
              return ErrorCode::kError;
          }
      }
  
      if (!fNumActivePages) {
          return ErrorCode::kError;
      }
  
      // Try to find a plot that we can perform an inline upload to.
      // We prioritize this upload in reverse order of pages to counterbalance the order above.
      Plot* plot = nullptr;
      for (int pageIdx = ((int)fNumActivePages)-1; pageIdx >= 0; --pageIdx) {
          Plot* currentPlot = fPages[pageIdx].fPlotList.tail();
          if (currentPlot->lastUseToken() != target->tokenTracker()->nextDrawToken()) {
              plot = currentPlot;
              break;
          }
      }
  
      // If we can't find a plot that is not used in a draw currently being prepared by an op, then
      // we have to fail. This gives the op a chance to enqueue the draw, and call back into this
      // function. When that draw is enqueued, the draw token advances, and the subsequent call will
      // continue past this branch and prepare an inline upload that will occur after the enqueued
      // draw which references the plot's pre-upload content.
      if (!plot) {
          return ErrorCode::kTryAgain;
      }
  
      this->processEviction(plot->id());
      int pageIdx = GetPageIndexFromID(plot->id());
      fPages[pageIdx].fPlotList.remove(plot);
      sk_sp<Plot>& newPlot = fPages[pageIdx].fPlotArray[plot->index()];
      newPlot.reset(plot->clone());
  
      fPages[pageIdx].fPlotList.addToHead(newPlot.get());
      SkASSERT(GrBytesPerPixel(fProxies[pageIdx]->config()) == newPlot->bpp());
      SkDEBUGCODE(bool verify = )newPlot->addSubImage(width, height, image, loc);
      SkASSERT(verify);
  
      // Note that this plot will be uploaded inline with the draws whereas the
      // one it displaced most likely was uploaded ASAP.
      // With c+14 we could move sk_sp into lambda to only ref once.
      sk_sp<Plot> plotsp(SkRef(newPlot.get()));
  
      GrTextureProxy* proxy = fProxies[pageIdx].get();
      SkASSERT(proxy->isInstantiated());
  
      GrDeferredUploadToken lastUploadToken = target->addInlineUpload(
              [plotsp, proxy](GrDeferredTextureUploadWritePixelsFn& writePixels) {
                  plotsp->uploadToTexture(writePixels, proxy);
              });
      newPlot->setLastUploadToken(lastUploadToken);
  
      *id = newPlot->id();
  
      return ErrorCode::kSucceeded;
  }
  
  void GrDrawOpAtlas::compact(GrDeferredUploadToken startTokenForNextFlush) {
      if (fNumActivePages <= 1) {
          fPrevFlushToken = startTokenForNextFlush;
          return;
      }
  
      // For all plots, reset number of flushes since used if used this frame.
      PlotList::Iter plotIter;
      bool atlasUsedThisFlush = false;
      for (uint32_t pageIndex = 0; pageIndex < fNumActivePages; ++pageIndex) {
          plotIter.init(fPages[pageIndex].fPlotList, PlotList::Iter::kHead_IterStart);
          while (Plot* plot = plotIter.get()) {
              // Reset number of flushes since used
              if (plot->lastUseToken().inInterval(fPrevFlushToken, startTokenForNextFlush)) {
                  plot->resetFlushesSinceLastUsed();
                  atlasUsedThisFlush = true;
              }
  
              plotIter.next();
          }
      }
  
      // We only try to compact if the atlas was used in the recently completed flush.
      // This is to handle the case where a lot of text or path rendering has occurred but then just
      // a blinking cursor is drawn.
      // TODO: consider if we should also do this if it's been a long time since the last atlas use
      if (atlasUsedThisFlush) {
          SkTArray<Plot*> availablePlots;
          uint32_t lastPageIndex = fNumActivePages - 1;
  
          // For all plots but the last one, update number of flushes since used, and check to see
          // if there are any in the first pages that the last page can safely upload to.
          for (uint32_t pageIndex = 0; pageIndex < lastPageIndex; ++pageIndex) {
  #ifdef DUMP_ATLAS_DATA
              if (gDumpAtlasData) {
                  SkDebugf("page %d: ", pageIndex);
              }
  #endif
              plotIter.init(fPages[pageIndex].fPlotList, PlotList::Iter::kHead_IterStart);
              while (Plot* plot = plotIter.get()) {
                  // Update number of flushes since plot was last used
                  // We only increment the 'sinceLastUsed' count for flushes where the atlas was used
                  // to avoid deleting everything when we return to text drawing in the blinking
                  // cursor case
                  if (!plot->lastUseToken().inInterval(fPrevFlushToken, startTokenForNextFlush)) {
                      plot->incFlushesSinceLastUsed();
                  }
  
  #ifdef DUMP_ATLAS_DATA
                  if (gDumpAtlasData) {
                      SkDebugf("%d ", plot->flushesSinceLastUsed());
                  }
  #endif
                  // Count plots we can potentially upload to in all pages except the last one
                  // (the potential compactee).
                  if (plot->flushesSinceLastUsed() > kRecentlyUsedCount) {
                      availablePlots.push_back() = plot;
                  }
  
                  plotIter.next();
              }
  #ifdef DUMP_ATLAS_DATA
              if (gDumpAtlasData) {
                  SkDebugf("\n");
              }
  #endif
          }
  
          // Count recently used plots in the last page and evict any that are no longer in use.
          // Since we prioritize uploading to the first pages, this will eventually
          // clear out usage of this page unless we have a large need.
          plotIter.init(fPages[lastPageIndex].fPlotList, PlotList::Iter::kHead_IterStart);
          unsigned int usedPlots = 0;
  #ifdef DUMP_ATLAS_DATA
          if (gDumpAtlasData) {
              SkDebugf("page %d: ", lastPageIndex);
          }
  #endif
          while (Plot* plot = plotIter.get()) {
              // Update number of flushes since plot was last used
              if (!plot->lastUseToken().inInterval(fPrevFlushToken, startTokenForNextFlush)) {
                  plot->incFlushesSinceLastUsed();
              }
  
  #ifdef DUMP_ATLAS_DATA
              if (gDumpAtlasData) {
                  SkDebugf("%d ", plot->flushesSinceLastUsed());
              }
  #endif
              // If this plot was used recently
              if (plot->flushesSinceLastUsed() <= kRecentlyUsedCount) {
                  usedPlots++;
              } else if (plot->lastUseToken() != GrDeferredUploadToken::AlreadyFlushedToken()) {
                  // otherwise if aged out just evict it.
                  this->processEvictionAndResetRects(plot);
              }
              plotIter.next();
          }
  #ifdef DUMP_ATLAS_DATA
          if (gDumpAtlasData) {
              SkDebugf("\n");
          }
  #endif
  
          // If recently used plots in the last page are using less than a quarter of the page, try
          // to evict them if there's available space in earlier pages. Since we prioritize uploading
          // to the first pages, this will eventually clear out usage of this page unless we have a
          // large need.
          if (availablePlots.count() && usedPlots && usedPlots <= fNumPlots / 4) {
              plotIter.init(fPages[lastPageIndex].fPlotList, PlotList::Iter::kHead_IterStart);
              while (Plot* plot = plotIter.get()) {
                  // If this plot was used recently
                  if (plot->flushesSinceLastUsed() <= kRecentlyUsedCount) {
                      // See if there's room in an earlier page and if so evict.
                      // We need to be somewhat harsh here so that a handful of plots that are
                      // consistently in use don't end up locking the page in memory.
                      if (availablePlots.count() > 0) {
                          this->processEvictionAndResetRects(plot);
                          this->processEvictionAndResetRects(availablePlots.back());
                          availablePlots.pop_back();
                          --usedPlots;
                      }
                      if (!usedPlots || !availablePlots.count()) {
                          break;
                      }
                  }
                  plotIter.next();
              }
          }
  
          // If none of the plots in the last page have been used recently, delete it.
          if (!usedPlots) {
  #ifdef DUMP_ATLAS_DATA
              if (gDumpAtlasData) {
                  SkDebugf("delete %d\n", fNumPages-1);
              }
  #endif
              this->deactivateLastPage();
          }
      }
  
      fPrevFlushToken = startTokenForNextFlush;
  }
  
  bool GrDrawOpAtlas::createPages(GrProxyProvider* proxyProvider) {
      SkASSERT(SkIsPow2(fTextureWidth) && SkIsPow2(fTextureHeight));
  
      GrSurfaceDesc desc;
      if (proxyProvider->caps()->shouldInitializeTextures()) {
          // The atlas isn't guaranteed to touch all its pixels so, for platforms that benefit
          // from complete initialization, clear everything.
          desc.fFlags = kPerformInitialClear_GrSurfaceFlag;
      } else {
          desc.fFlags = kNone_GrSurfaceFlags;
      }
      desc.fWidth = fTextureWidth;
      desc.fHeight = fTextureHeight;
      desc.fConfig = GrColorTypeToPixelConfig(fColorType, GrSRGBEncoded::kNo);
  
      int numPlotsX = fTextureWidth/fPlotWidth;
      int numPlotsY = fTextureHeight/fPlotHeight;
  
      for (uint32_t i = 0; i < this->maxPages(); ++i) {
          fProxies[i] = proxyProvider->createProxy(fFormat, desc, kTopLeft_GrSurfaceOrigin,
                                                   SkBackingFit::kExact, SkBudgeted::kYes);
          if (!fProxies[i]) {
              return false;
          }
  
          fProxies[i]->priv().setIgnoredByResourceAllocator();
  
          // set up allocated plots
          fPages[i].fPlotArray.reset(new sk_sp<Plot>[ numPlotsX * numPlotsY ]);
  
          sk_sp<Plot>* currPlot = fPages[i].fPlotArray.get();
          for (int y = numPlotsY - 1, r = 0; y >= 0; --y, ++r) {
              for (int x = numPlotsX - 1, c = 0; x >= 0; --x, ++c) {
                  uint32_t plotIndex = r * numPlotsX + c;
                  currPlot->reset(new Plot(i, plotIndex, 1, x, y, fPlotWidth, fPlotHeight,
                                           fColorType));
  
                  // build LRU list
                  fPages[i].fPlotList.addToHead(currPlot->get());
                  ++currPlot;
              }
          }
  
      }
  
      return true;
  }
  
  
  bool GrDrawOpAtlas::activateNewPage(GrResourceProvider* resourceProvider) {
      SkASSERT(fNumActivePages < this->maxPages());
  
      if (!fProxies[fNumActivePages]->instantiate(resourceProvider)) {
          return false;
      }
  
  #ifdef DUMP_ATLAS_DATA
      if (gDumpAtlasData) {
          SkDebugf("activated page#: %d\n", fNumActivePages);
      }
  #endif
  
      ++fNumActivePages;
      return true;
  }
  
  
  inline void GrDrawOpAtlas::deactivateLastPage() {
      SkASSERT(fNumActivePages);
  
      uint32_t lastPageIndex = fNumActivePages - 1;
  
      int numPlotsX = fTextureWidth/fPlotWidth;
      int numPlotsY = fTextureHeight/fPlotHeight;
  
      fPages[lastPageIndex].fPlotList.reset();
      for (int r = 0; r < numPlotsY; ++r) {
          for (int c = 0; c < numPlotsX; ++c) {
              uint32_t plotIndex = r * numPlotsX + c;
  
              Plot* currPlot = fPages[lastPageIndex].fPlotArray[plotIndex].get();
              currPlot->resetRects();
              currPlot->resetFlushesSinceLastUsed();
  
              // rebuild the LRU list
              SkDEBUGCODE(currPlot->fPrev = currPlot->fNext = nullptr);
              SkDEBUGCODE(currPlot->fList = nullptr);
              fPages[lastPageIndex].fPlotList.addToHead(currPlot);
          }
      }
  
      // remove ref to the backing texture
      fProxies[lastPageIndex]->deinstantiate();
      --fNumActivePages;
  }
  
  GrDrawOpAtlasConfig::GrDrawOpAtlasConfig(int maxTextureSize, size_t maxBytes) {
      static const SkISize kARGBDimensions[] = {
          {256, 256},   // maxBytes < 2^19
          {512, 256},   // 2^19 <= maxBytes < 2^20
          {512, 512},   // 2^20 <= maxBytes < 2^21
          {1024, 512},  // 2^21 <= maxBytes < 2^22
          {1024, 1024}, // 2^22 <= maxBytes < 2^23
          {2048, 1024}, // 2^23 <= maxBytes
      };
  
      // Index 0 corresponds to maxBytes of 2^18, so start by dividing it by that
      maxBytes >>= 18;
      // Take the floor of the log to get the index
      int index = maxBytes > 0
          ? SkTPin<int>(SkPrevLog2(maxBytes), 0, SK_ARRAY_COUNT(kARGBDimensions) - 1)
          : 0;
  
      SkASSERT(kARGBDimensions[index].width() <= kMaxAtlasDim);
      SkASSERT(kARGBDimensions[index].height() <= kMaxAtlasDim);
      fARGBDimensions.set(SkTMin<int>(kARGBDimensions[index].width(), maxTextureSize),
                          SkTMin<int>(kARGBDimensions[index].height(), maxTextureSize));
      fMaxTextureSize = SkTMin<int>(maxTextureSize, kMaxAtlasDim);
  }
  
  SkISize GrDrawOpAtlasConfig::atlasDimensions(GrMaskFormat type) const {
      if (kA8_GrMaskFormat == type) {
          // A8 is always 2x the ARGB dimensions, clamped to the max allowed texture size
          return { SkTMin<int>(2 * fARGBDimensions.width(), fMaxTextureSize),
                   SkTMin<int>(2 * fARGBDimensions.height(), fMaxTextureSize) };
      } else {
          return fARGBDimensions;
      }
  }
  
  SkISize GrDrawOpAtlasConfig::plotDimensions(GrMaskFormat type) const {
      if (kA8_GrMaskFormat == type) {
          SkISize atlasDimensions = this->atlasDimensions(type);
          // For A8 we want to grow the plots at larger texture sizes to accept more of the
          // larger SDF glyphs. Since the largest SDF glyph can be 170x170 with padding, this
          // allows us to pack 3 in a 512x256 plot, or 9 in a 512x512 plot.
  
          // This will give us 512x256 plots for 2048x1024, 512x512 plots for 2048x2048,
          // and 256x256 plots otherwise.
          int plotWidth = atlasDimensions.width() >= 2048 ? 512 : 256;
          int plotHeight = atlasDimensions.height() >= 2048 ? 512 : 256;
  
          return { plotWidth, plotHeight };
      } else {
          // ARGB and LCD always use 256x256 plots -- this has been shown to be faster
          return { 256, 256 };
      }
  }
  
  constexpr int GrDrawOpAtlasConfig::kMaxAtlasDim;
  