impeller::ClipContents Class Reference

#include <clip_contents.h>

Inheritance diagram for impeller::ClipContents:

Public Member Functions
	ClipContents ()
	~ClipContents ()
void	SetGeometry (const std::shared_ptr< Geometry > &geometry)
void	SetClipOperation (Entity::ClipOperation clip_op)
std::optional< Rect >	GetCoverage (const Entity &entity) const override
	Get the area of the render pass that will be affected when this contents is rendered. More...
ClipCoverage	GetClipCoverage (const Entity &entity, const std::optional< Rect > &current_clip_coverage) const override
	Given the current pass space bounding rectangle of the clip buffer, return the expected clip coverage after this draw call. This should only be implemented for contents that may write to the clip buffer. More...
bool	ShouldRender (const Entity &entity, const std::optional< Rect > clip_coverage) const override
bool	Render (const ContentContext &renderer, const Entity &entity, RenderPass &pass) const override
bool	CanInheritOpacity (const Entity &entity) const override
	Whether or not this contents can accept the opacity peephole optimization. More...
void	SetInheritedOpacity (Scalar opacity) override
	Inherit the provided opacity. More...
Public Member Functions inherited from impeller::Contents
	Contents ()
virtual	~Contents ()
virtual void	PopulateGlyphAtlas (const std::shared_ptr< LazyGlyphAtlas > &lazy_glyph_atlas, Scalar scale)
	Add any text data to the specified lazy atlas. The scale parameter must be used again later when drawing the text. More...
void	SetCoverageHint (std::optional< Rect > coverage_hint)
	Hint that specifies the coverage area of this Contents that will actually be used during rendering. This is for optimization purposes only and can not be relied on as a clip. May optionally affect the result of GetCoverage(). More...
const std::optional< Rect > &	GetCoverageHint () const
virtual bool	IsOpaque () const
	Whether this Contents only emits opaque source colors from the fragment stage. This value does not account for any entity properties (e.g. the blend mode), clips/visibility culling, or inherited opacity. More...
virtual std::optional< Snapshot >	RenderToSnapshot (const ContentContext &renderer, const Entity &entity, std::optional< Rect > coverage_limit=std::nullopt, const std::optional< SamplerDescriptor > &sampler_descriptor=std::nullopt, bool msaa_enabled=true, int32_t mip_count=1, const std::string &label="Snapshot") const
	Render this contents to a snapshot, respecting the entity's transform, path, clip depth, and blend mode. The result texture size is always the size of GetCoverage(entity). More...
std::optional< Size >	GetColorSourceSize () const
	Return the color source's intrinsic size, if available. More...
void	SetColorSourceSize (Size size)
virtual std::optional< Color >	AsBackgroundColor (const Entity &entity, ISize target_size) const
	Returns a color if this Contents will flood the given target_size with a color. This output color is the "Source" color that will be used for the Entity's blend operation. More...
virtual const FilterContents *	AsFilter () const
	Cast to a filter. Returns nullptr if this Contents is not a filter. More...
virtual bool	ApplyColorFilter (const ColorFilterProc &color_filter_proc)
	If possible, applies a color filter to this contents inputs on the CPU. More...

Additional Inherited Members
Public Types inherited from impeller::Contents
using	ColorFilterProc = std::function< Color(Color)>
using	RenderProc = std::function< bool(const ContentContext &renderer, const Entity &entity, RenderPass &pass)>
using	CoverageProc = std::function< std::optional< Rect >(const Entity &entity)>
Static Public Member Functions inherited from impeller::Contents
static std::shared_ptr< Contents >	MakeAnonymous (RenderProc render_proc, CoverageProc coverage_proc)

Detailed Description

Definition at line 18 of file clip_contents.h.

Constructor & Destructor Documentation

ClipContents()

impeller::ClipContents::ClipContents ( )

default

~ClipContents()

impeller::ClipContents::~ClipContents ( )

default

Member Function Documentation

CanInheritOpacity()

bool impeller::ClipContents::CanInheritOpacity ( const Entity &  entity ) const

overridevirtual

Whether or not this contents can accept the opacity peephole optimization.

By default all contents return false. Contents are responsible for determining whether or not their own geometries intersect in a way that makes accepting opacity impossible. It is always safe to return false, especially if computing overlap would be computationally expensive.

Reimplemented from impeller::Contents.

Definition at line 79 of file clip_contents.cc.

                                                               {
  return true;
}

GetClipCoverage()

Contents::ClipCoverage impeller::ClipContents::GetClipCoverage ( const Entity &  entity, const std::optional< Rect > &  current_clip_coverage  ) const

overridevirtual

Given the current pass space bounding rectangle of the clip buffer, return the expected clip coverage after this draw call. This should only be implemented for contents that may write to the clip buffer.

During rendering, coverage coordinates count pixels from the top left corner of the framebuffer.

Reimplemented from impeller::Contents.

Definition at line 46 of file clip_contents.cc.

                                                          {
  if (!current_clip_coverage.has_value()) {
    return {.type = ClipCoverage::Type::kAppend, .coverage = std::nullopt};
  }
  switch (clip_op_) {
    case Entity::ClipOperation::kDifference:
      // This can be optimized further by considering cases when the bounds of
      // the current stencil will shrink.
      return {.type = ClipCoverage::Type::kAppend,
              .coverage = current_clip_coverage};
    case Entity::ClipOperation::kIntersect:
      if (!geometry_) {
        return {.type = ClipCoverage::Type::kAppend, .coverage = std::nullopt};
      }
      auto coverage = geometry_->GetCoverage(entity.GetTransform());
      if (!coverage.has_value() || !current_clip_coverage.has_value()) {
        return {.type = ClipCoverage::Type::kAppend, .coverage = std::nullopt};
      }
      return {
          .type = ClipCoverage::Type::kAppend,
          .coverage = current_clip_coverage->Intersection(coverage.value()),
      };
  }
  FML_UNREACHABLE();
}

References impeller::Entity::GetTransform(), impeller::Entity::kDifference, impeller::Entity::kIntersect, and impeller::Contents::ClipCoverage::type.

GetCoverage()

std::optional< Rect > impeller::ClipContents::GetCoverage ( const Entity &  entity ) const

overridevirtual

Get the area of the render pass that will be affected when this contents is rendered.

During rendering, coverage coordinates count pixels from the top left corner of the framebuffer.

Returns

The coverage rectangle. An std::nullopt result means that rendering this contents has no effect on the output color.

Implements impeller::Contents.

Definition at line 42 of file clip_contents.cc.

                                                                      {
  return std::nullopt;
};

Render()

bool impeller::ClipContents::Render ( const ContentContext &  renderer, const Entity &  entity, RenderPass &  pass  ) const

overridevirtual

Stencil preparation draw.

Write depth.

Implements impeller::Contents.

Definition at line 85 of file clip_contents.cc.

                                                  {
  if (!geometry_) {
    return true;
  }
 
  using VS = ClipPipeline::VertexShader;
 
  if (clip_op_ == Entity::ClipOperation::kIntersect &&
      geometry_->IsAxisAlignedRect() &&
      entity.GetTransform().IsTranslationScaleOnly()) {
    std::optional<Rect> coverage =
        geometry_->GetCoverage(entity.GetTransform());
    if (coverage.has_value() &&
        coverage->Contains(Rect::MakeSize(pass.GetRenderTargetSize()))) {
      // Skip axis-aligned intersect clips that cover the whole render target
      // since they won't draw anything to the depth buffer.
      return true;
    }
  }
 
  VS::FrameInfo info;
  info.depth = GetShaderClipDepth(entity);
 
  auto geometry_result = geometry_->GetPositionBuffer(renderer, entity, pass);
  auto options = OptionsFromPass(pass);
  options.blend_mode = BlendMode::kDestination;
 
  pass.SetStencilReference(0);
 
  /// Stencil preparation draw.
 
  options.depth_write_enabled = false;
  options.primitive_type = geometry_result.type;
  pass.SetVertexBuffer(std::move(geometry_result.vertex_buffer));
  switch (geometry_result.mode) {
    case GeometryResult::Mode::kNonZero:
      pass.SetCommandLabel("Clip stencil preparation (NonZero)");
      options.stencil_mode =
          ContentContextOptions::StencilMode::kStencilNonZeroFill;
      break;
    case GeometryResult::Mode::kEvenOdd:
      pass.SetCommandLabel("Clip stencil preparation (EvenOdd)");
      options.stencil_mode =
          ContentContextOptions::StencilMode::kStencilEvenOddFill;
      break;
    case GeometryResult::Mode::kNormal:
    case GeometryResult::Mode::kPreventOverdraw:
      pass.SetCommandLabel("Clip stencil preparation (Increment)");
      options.stencil_mode =
          ContentContextOptions::StencilMode::kOverdrawPreventionIncrement;
      break;
  }
  pass.SetPipeline(renderer.GetClipPipeline(options));
 
  info.mvp = geometry_result.transform;
  VS::BindFrameInfo(pass, renderer.GetTransientsBuffer().EmplaceUniform(info));
 
  if (!pass.Draw().ok()) {
    return false;
  }
 
  /// Write depth.
 
  options.depth_write_enabled = true;
  options.primitive_type = PrimitiveType::kTriangleStrip;
  Rect cover_area;
  switch (clip_op_) {
    case Entity::ClipOperation::kIntersect:
      pass.SetCommandLabel("Intersect Clip");
      options.stencil_mode =
          ContentContextOptions::StencilMode::kCoverCompareInverted;
      cover_area = Rect::MakeSize(pass.GetRenderTargetSize());
      break;
    case Entity::ClipOperation::kDifference:
      pass.SetCommandLabel("Difference Clip");
      options.stencil_mode = ContentContextOptions::StencilMode::kCoverCompare;
      std::optional<Rect> maybe_cover_area =
          geometry_->GetCoverage(entity.GetTransform());
      if (!maybe_cover_area.has_value()) {
        return true;
      }
      cover_area = maybe_cover_area.value();
      break;
  }
  auto points = cover_area.GetPoints();
  auto vertices =
      VertexBufferBuilder<VS::PerVertexData>{}
          .AddVertices({{points[0]}, {points[1]}, {points[2]}, {points[3]}})
          .CreateVertexBuffer(renderer.GetTransientsBuffer());
  pass.SetVertexBuffer(std::move(vertices));
 
  pass.SetPipeline(renderer.GetClipPipeline(options));
 
  info.mvp = pass.GetOrthographicTransform();
  VS::BindFrameInfo(pass, renderer.GetTransientsBuffer().EmplaceUniform(info));
 
  return pass.Draw().ok();
}

References impeller::VertexBufferBuilder< VertexType_, IndexType_ >::AddVertices(), impeller::RenderPass::Draw(), impeller::HostBuffer::EmplaceUniform(), impeller::ContentContext::GetClipPipeline(), impeller::RenderPass::GetOrthographicTransform(), impeller::TRect< T >::GetPoints(), impeller::RenderPass::GetRenderTargetSize(), impeller::GetShaderClipDepth(), impeller::Entity::GetTransform(), impeller::ContentContext::GetTransientsBuffer(), impeller::Matrix::IsTranslationScaleOnly(), impeller::ContentContextOptions::kCoverCompare, impeller::ContentContextOptions::kCoverCompareInverted, impeller::kDestination, impeller::Entity::kDifference, impeller::GeometryResult::kEvenOdd, impeller::Entity::kIntersect, impeller::GeometryResult::kNonZero, impeller::GeometryResult::kNormal, impeller::ContentContextOptions::kOverdrawPreventionIncrement, impeller::GeometryResult::kPreventOverdraw, impeller::ContentContextOptions::kStencilEvenOddFill, impeller::ContentContextOptions::kStencilNonZeroFill, impeller::kTriangleStrip, impeller::TRect< Scalar >::MakeSize(), impeller::OptionsFromPass(), impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetStencilReference(), and impeller::RenderPass::SetVertexBuffer().

SetClipOperation()

void impeller::ClipContents::SetClipOperation

(

Entity::ClipOperation

clip_op

)

Definition at line 38 of file clip_contents.cc.

                                                               {
  clip_op_ = clip_op;
}

SetGeometry()

void impeller::ClipContents::SetGeometry

(

const std::shared_ptr< Geometry > &

geometry

)

Definition at line 34 of file clip_contents.cc.

                                                                      {
  geometry_ = geometry;
}

SetInheritedOpacity()

void impeller::ClipContents::SetInheritedOpacity ( Scalar  opacity )

overridevirtual

Inherit the provided opacity.

   Use of this method is invalid if CanAcceptOpacity returns false.

Reimplemented from impeller::Contents.

Definition at line 83 of file clip_contents.cc.

{}

ShouldRender()

bool impeller::ClipContents::ShouldRender ( const Entity &  entity, const std::optional< Rect >  clip_coverage  ) const

overridevirtual

Reimplemented from impeller::Contents.

Definition at line 74 of file clip_contents.cc.

                                                                             {
  return true;
}

---

The documentation for this class was generated from the following files:

• impeller/entity/contents/clip_contents.h
• impeller/entity/contents/clip_contents.cc