chromium/third_party/skia/src/gpu/ganesh/GrDrawOpAtlas.h

/*
 * 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 "include/core/SkRefCnt.h"
#include "include/core/SkSize.h"
#include "include/gpu/ganesh/GrBackendSurface.h"
#include "include/private/base/SkAssert.h"
#include "include/private/base/SkDebug.h"
#include "src/gpu/AtlasTypes.h"
#include "src/gpu/ganesh/GrDeferredUpload.h"
#include "src/gpu/ganesh/GrSurfaceProxyView.h"

#include <cstddef>
#include <cstdint>
#include <memory>
#include <string>
#include <string_view>
#include <vector>

class GrOnFlushResourceProvider;
class GrProxyProvider;
class GrResourceProvider;
class GrTextureProxy;
enum SkColorType : int;

/**
 * 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 less than a quarter of the plots have
 * been used recently (within kPlotRecentlyUsedCount iterations) and there are available
 * plots in lower index pages, the higher index page will be deactivated, and its glyphs will
 * gradually migrate to other pages via the usual upload system.
 *
 * 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 { … };

// There are three atlases (A8, 565, ARGB) that are kept in relation with one another. In
// general, because A8 is the most frequently used mask format its 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 { … };

#endif