blob: fd702ddfd9b8b15b9706ca2be32136f6d693df48 [file] [log] [blame]
* Copyright 2021 Google LLC
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef skgpu_graphite_Renderer_DEFINED
#define skgpu_graphite_Renderer_DEFINED
#include "include/core/SkSpan.h"
#include "include/core/SkString.h"
#include "include/core/SkTypes.h"
#include "src/core/SkEnumBitMask.h"
#include "src/gpu/graphite/Attribute.h"
#include "src/gpu/graphite/DrawTypes.h"
#include "src/gpu/graphite/ResourceTypes.h"
#include "src/gpu/graphite/Uniform.h"
#include <array>
#include <initializer_list>
#include <string>
#include <string_view>
#include <vector>
enum class SkPathFillType;
namespace skgpu { enum class MaskFormat; }
namespace skgpu::graphite {
class DrawWriter;
class DrawParams;
class PipelineDataGatherer;
class ResourceProvider;
class TextureDataBlock;
struct ResourceBindingRequirements;
struct Varying {
const char* fName;
SkSLType fType;
// TODO: add modifier (e.g., flat and noperspective) support
* The actual technique for rasterizing a high-level draw recorded in a DrawList is handled by a
* specific Renderer. Each technique has an associated singleton Renderer that decomposes the
* technique into a series of RenderSteps that must be executed in the specified order for the draw.
* However, the RenderStep executions for multiple draws can be re-arranged so batches of each
* step can be performed in a larger GPU operation. This re-arranging relies on accurate
* determination of the DisjointStencilIndex for each draw so that stencil steps are not corrupted
* by another draw before its cover step is executed. It also relies on the CompressedPaintersOrder
* for each draw to ensure steps are not re-arranged in a way that violates the original draw order.
* Renderer itself is non-virtual since it simply has to point to a list of RenderSteps. RenderSteps
* on the other hand are virtual implement the technique specific functionality. It is entirely
* possible for certain types of steps, e.g. a bounding box cover, to be re-used across different
* Renderers even if the preceeding steps were different.
* All Renderers are accessed through the SharedContext's RendererProvider.
class RenderStep {
virtual ~RenderStep() = default;
// The DrawWriter is configured with the vertex and instance strides of the RenderStep, and its
// primitive type. The recorded draws will be executed with a graphics pipeline compatible with
// this RenderStep.
virtual void writeVertices(DrawWriter*, const DrawParams&, int ssboIndex) const = 0;
// Write out the uniform values (aligned for the layout), textures, and samplers. The uniform
// values will be de-duplicated across all draws using the RenderStep before uploading to the
// GPU, but it can be assumed the uniforms will be bound before the draws recorded in
// 'writeVertices' are executed.
virtual void writeUniformsAndTextures(const DrawParams&, PipelineDataGatherer*) const = 0;
// Returns the body of a vertex function, which must define a float4 devPosition variable and
// must write to an already-defined float2 stepLocalCoords variable. This will be automatically
// set to a varying for the fragment shader if the paint requires local coords. This SkSL has
// access to the variables declared by vertexAttributes(), instanceAttributes(), and uniforms().
// The 'devPosition' variable's z must store the PaintDepth normalized to a float from [0, 1],
// for each processed draw although the RenderStep can choose to upload it in any manner.
// NOTE: The above contract is mainly so that the entire SkSL program can be created by just str
// concatenating struct definitions generated from the RenderStep and paint Combination
// and then including the function bodies returned here.
virtual std::string vertexSkSL() const = 0;
// Emits code to set up textures and samplers. Should only be defined if hasTextures is true.
virtual std::string texturesAndSamplersSkSL(const ResourceBindingRequirements&,
int* nextBindingIndex) const {
return R"()";
// Emits code to set up coverage value. Should only be defined if overridesCoverage is true.
// When implemented the returned SkSL fragment should write its coverage into a
// 'half4 outputCoverage' variable (defined in the calling code) with the actual
// coverage splatted out into all four channels.
virtual const char* fragmentCoverageSkSL() const { return R"()"; }
// Emits code to set up a primitive color value. Should only be defined if emitsPrimitiveColor
// is true. When implemented, the returned SkSL fragment should write its color into a
// 'half4 primitiveColor' variable (defined in the calling code).
virtual const char* fragmentColorSkSL() const { return R"()"; }
uint32_t uniqueID() const { return fUniqueID; }
// Returns a name formatted as "Subclass[variant]", where "Subclass" matches the C++ class name
// and variant is a unique term describing instance's specific configuration.
const char* name() const { return fName.c_str(); }
bool requiresMSAA() const { return fFlags & Flags::kRequiresMSAA; }
bool performsShading() const { return fFlags & Flags::kPerformsShading; }
bool hasTextures() const { return fFlags & Flags::kHasTextures; }
bool emitsCoverage() const { return fFlags & Flags::kEmitsCoverage; }
bool emitsPrimitiveColor() const { return fFlags & Flags::kEmitsPrimitiveColor; }
PrimitiveType primitiveType() const { return fPrimitiveType; }
size_t vertexStride() const { return fVertexStride; }
size_t instanceStride() const { return fInstanceStride; }
size_t numUniforms() const { return fUniforms.size(); }
size_t numVertexAttributes() const { return fVertexAttrs.size(); }
size_t numInstanceAttributes() const { return fInstanceAttrs.size(); }
static const char* ssboIndex() { return "ssboIndex"; }
// The uniforms of a RenderStep are bound to the kRenderStep slot, the rest of the pipeline
// may still use uniforms bound to other slots.
SkSpan<const Uniform> uniforms() const { return SkSpan(fUniforms); }
SkSpan<const Attribute> vertexAttributes() const { return SkSpan(fVertexAttrs); }
SkSpan<const Attribute> instanceAttributes() const { return SkSpan(fInstanceAttrs); }
SkSpan<const Varying> varyings() const { return SkSpan(fVaryings); }
const DepthStencilSettings& depthStencilSettings() const { return fDepthStencilSettings; }
SkEnumBitMask<DepthStencilFlags> depthStencilFlags() const {
return (fDepthStencilSettings.fStencilTestEnabled
? DepthStencilFlags::kStencil : DepthStencilFlags::kNone) |
(fDepthStencilSettings.fDepthTestEnabled || fDepthStencilSettings.fDepthWriteEnabled
? DepthStencilFlags::kDepth : DepthStencilFlags::kNone);
// TODO: Actual API to do things
// 6. Some Renderers benefit from being able to share vertices between RenderSteps. Must find a
// way to support that. It may mean that RenderSteps get state per draw.
// - Does Renderer make RenderStepFactories that create steps for each DrawList::Draw?
// - Does DrawList->DrawPass conversion build a separate array of blind data that the
// stateless Renderstep can refer to for {draw,step} pairs?
// - Does each DrawList::Draw have extra space (e.g. 8 bytes) that steps can cache data in?
enum class Flags : unsigned {
kNone = 0b00000,
kRequiresMSAA = 0b00001,
kPerformsShading = 0b00010,
kHasTextures = 0b00100,
kEmitsCoverage = 0b01000,
kEmitsPrimitiveColor = 0b10000,
// While RenderStep does not define the full program that's run for a draw, it defines the
// entire vertex layout of the pipeline. This is not allowed to change, so can be provided to
// the RenderStep constructor by subclasses.
RenderStep(std::string_view className,
std::string_view variantName,
SkEnumBitMask<Flags> flags,
std::initializer_list<Uniform> uniforms,
PrimitiveType primitiveType,
DepthStencilSettings depthStencilSettings,
SkSpan<const Attribute> vertexAttrs,
SkSpan<const Attribute> instanceAttrs,
SkSpan<const Varying> varyings = {});
friend class Renderer; // for Flags
// Cannot copy or move
RenderStep(const RenderStep&) = delete;
RenderStep(RenderStep&&) = delete;
uint32_t fUniqueID;
SkEnumBitMask<Flags> fFlags;
PrimitiveType fPrimitiveType;
DepthStencilSettings fDepthStencilSettings;
// TODO: When we always use C++17 for builds, we should be able to just let subclasses declare
// constexpr arrays and point to those, but we need explicit storage for C++14.
// Alternatively, if we imposed a max attr count, similar to Renderer's num render steps, we
// could just have this be std::array and keep all attributes inline with the RenderStep memory.
// On the other hand, the attributes are only needed when creating a new pipeline so it's not
// that performance sensitive.
std::vector<Uniform> fUniforms;
std::vector<Attribute> fVertexAttrs;
std::vector<Attribute> fInstanceAttrs;
std::vector<Varying> fVaryings;
size_t fVertexStride; // derived from vertex attribute set
size_t fInstanceStride; // derived from instance attribute set
std::string fName;
class Renderer {
using StepFlags = RenderStep::Flags;
// The maximum number of render steps that any Renderer is allowed to have.
static constexpr int kMaxRenderSteps = 4;
const RenderStep& step(int i) const {
SkASSERT(i >= 0 && i < fStepCount);
return *fSteps[i];
SkSpan<const RenderStep* const> steps() const {
SkASSERT(fStepCount > 0); // steps() should only be called on valid Renderers.
return {, static_cast<size_t>(fStepCount) };
const char* name() const { return fName.c_str(); }
DrawTypeFlags drawTypes() const { return fDrawTypes; }
int numRenderSteps() const { return fStepCount; }
bool requiresMSAA() const { return fStepFlags & StepFlags::kRequiresMSAA; }
bool emitsCoverage() const { return fStepFlags & StepFlags::kEmitsCoverage; }
bool emitsPrimitiveColor() const { return fStepFlags & StepFlags::kEmitsPrimitiveColor; }
SkEnumBitMask<DepthStencilFlags> depthStencilFlags() const { return fDepthStencilFlags; }
friend class RendererProvider; // for ctors
// Max render steps is 4, so just spell the options out for now...
Renderer(std::string_view name, DrawTypeFlags drawTypes, const RenderStep* s1)
: Renderer(name, drawTypes, std::array<const RenderStep*, 1>{s1}) {}
Renderer(std::string_view name, DrawTypeFlags drawTypes,
const RenderStep* s1, const RenderStep* s2)
: Renderer(name, drawTypes, std::array<const RenderStep*, 2>{s1, s2}) {}
Renderer(std::string_view name, DrawTypeFlags drawTypes,
const RenderStep* s1, const RenderStep* s2, const RenderStep* s3)
: Renderer(name, drawTypes, std::array<const RenderStep*, 3>{s1, s2, s3}) {}
Renderer(std::string_view name, DrawTypeFlags drawTypes,
const RenderStep* s1, const RenderStep* s2, const RenderStep* s3, const RenderStep* s4)
: Renderer(name, drawTypes, std::array<const RenderStep*, 4>{s1, s2, s3, s4}) {}
template<size_t N>
Renderer(std::string_view name, DrawTypeFlags drawTypes, std::array<const RenderStep*, N> steps)
: fName(name)
, fDrawTypes(drawTypes)
, fStepCount(SkTo<int>(N)) {
static_assert(N <= kMaxRenderSteps);
for (int i = 0 ; i < fStepCount; ++i) {
fSteps[i] = steps[i];
fStepFlags |= fSteps[i]->fFlags;
fDepthStencilFlags |= fSteps[i]->depthStencilFlags();
// At least one step needs to actually shade.
SkASSERT(fStepFlags & RenderStep::Flags::kPerformsShading);
// For RendererProvider to manage initialization; it will never expose a Renderer that is only
// default-initialized and not replaced because it's algorithm is disabled by caps/options.
Renderer() : fSteps(), fName(""), fStepCount(0) {}
Renderer& operator=(Renderer&&) = default;
std::array<const RenderStep*, kMaxRenderSteps> fSteps;
std::string fName;
DrawTypeFlags fDrawTypes = DrawTypeFlags::kAll;
int fStepCount;
SkEnumBitMask<StepFlags> fStepFlags = StepFlags::kNone;
SkEnumBitMask<DepthStencilFlags> fDepthStencilFlags = DepthStencilFlags::kNone;
} // namespace skgpu::graphite
#endif // skgpu_graphite_Renderer_DEFINED