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

/*
 * Copyright 2014 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrXferProcessor_DEFINED
#define GrXferProcessor_DEFINED

#include "include/core/SkRefCnt.h"
#include "include/private/base/SkAssert.h"
#include "include/private/base/SkMacros.h"
#include "include/private/base/SkTo.h"
#include "src/gpu/Blend.h"
#include "src/gpu/Swizzle.h"
#include "src/gpu/ganesh/GrCaps.h"
#include "src/gpu/ganesh/GrNonAtomicRef.h"
#include "src/gpu/ganesh/GrProcessor.h"
#include "src/gpu/ganesh/GrProcessorAnalysis.h"
#include "src/gpu/ganesh/glsl/GrGLSLUniformHandler.h"

#include <memory>

class GrGLSLProgramDataManager;
class GrGLSLXPFragmentBuilder;
enum GrSurfaceOrigin : int;
enum class GrClampType;
enum class SkBlendMode;
namespace skgpu { class KeyBuilder; }
struct GrShaderCaps;

/**
 * Barriers for blending. When a shader reads the dst directly, an Xfer barrier is sometimes
 * required after a pixel has been written, before it can be safely read again.
 */
enum GrXferBarrierType { … };
/** Should be able to treat kNone as false in boolean expressions */
static_assert …;

// Flag version of the above enum.
enum class GrXferBarrierFlags { … };

SK_MAKE_BITFIELD_CLASS_OPS(GrXferBarrierFlags)

/**
 * GrXferProcessor is responsible for implementing the xfer mode that blends the src color and dst
 * color, and for applying any coverage. It does this by emitting fragment shader code and
 * controlling the fixed-function blend state. When dual-source blending is available, it may also
 * write a secondary fragment shader output color. GrXferProcessor has two modes of operation:
 *
 * Dst read: When allowed by the backend API, or when supplied a texture of the destination, the
 * GrXferProcessor may read the destination color. While operating in this mode, the subclass only
 * provides shader code that blends the src and dst colors, and the base class applies coverage.
 *
 * No dst read: When not performing a dst read, the subclass is given full control of the fixed-
 * function blend state and/or secondary output, and is responsible to apply coverage on its own.
 *
 * A GrXferProcessor is never installed directly into our draw state, but instead is created from a
 * GrXPFactory once we have finalized the state of our draw.
 */
class GrXferProcessor : public GrProcessor, public GrNonAtomicRef<GrXferProcessor> { … };

/**
 * We install a GrXPFactory (XPF) early on in the pipeline before all the final draw information is
 * known (e.g. whether there is fractional pixel coverage, will coverage be 1 or 4 channel, is the
 * draw opaque, etc.). Once the state of the draw is finalized, we use the XPF along with all the
 * draw information to create a GrXferProcessor (XP) which can implement the desired blending for
 * the draw.
 *
 * Before the XP is created, the XPF is able to answer queries about what functionality the XPs it
 * creates will have. For example, can it create an XP that supports RGB coverage or will the XP
 * blend with the destination color.
 *
 * GrXPFactories are intended to be static immutable objects. We pass them around as raw pointers
 * and expect the pointers to always be valid and for the factories to be reusable and thread safe.
 * Equality is tested for using pointer comparison. GrXPFactory destructors must be no-ops.
 */

// In order to construct GrXPFactory subclass instances as constexpr the subclass, and therefore
// GrXPFactory, must be a literal type. One requirement is having a trivial destructor. This is ok
// since these objects have no need for destructors. However, GCC and clang throw a warning when a
// class has virtual functions and a non-virtual destructor. We suppress that warning here and
// for the subclasses.
#if defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
#endif
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wnon-virtual-dtor"
#endif
class GrXPFactory { … };
#if defined(__GNUC__)
#pragma GCC diagnostic pop
#endif
#if defined(__clang__)
#pragma clang diagnostic pop
#endif

SK_MAKE_BITFIELD_CLASS_OPS(GrXPFactory::AnalysisProperties)

//////////////////////////////////////////////////////////////////////////////

class GrXferProcessor::ProgramImpl { … };

#endif