impeller::ColorSourceContents Class Reference

#include <color_source_contents.h>

Inheritance diagram for impeller::ColorSourceContents:

Public Types
using	BindFragmentCallback = std::function< bool(RenderPass &pass)>
using	PipelineBuilderCallback = std::function< PipelineRef(ContentContextOptions)>
using	CreateGeometryCallback = std::function< GeometryResult(const ContentContext &renderer, const Entity &entity, RenderPass &pass, const Geometry *geom)>
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)>

Public Member Functions
	ColorSourceContents ()
	~ColorSourceContents () override
void	SetGeometry (const Geometry *geometry)
	Set the geometry that this contents will use to render. More...
const Geometry *	GetGeometry () const
	Get the geometry that this contents will use to render. More...
void	SetEffectTransform (Matrix matrix)
	Set the effect transform for this color source. More...
const Matrix &	GetInverseEffectTransform () const
	Set the inverted effect transform for this color source. More...
void	SetOpacityFactor (Scalar opacity)
	Set the opacity factor for this color source. More...
Scalar	GetOpacityFactor () const
	Get the opacity factor for this color source. More...
virtual bool	IsSolidColor () const
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...
void	SetInheritedOpacity (Scalar opacity) override
	Inherit the provided opacity. More...
Public Member Functions inherited from impeller::Contents
	Contents ()
virtual	~Contents ()
virtual bool	Render (const ContentContext &renderer, const Entity &entity, RenderPass &pass) const =0
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 Matrix &transform) 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, std::string_view 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 bool	ApplyColorFilter (const ColorFilterProc &color_filter_proc)
	If possible, applies a color filter to this contents inputs on the CPU. More...

Static Public Member Functions
template<typename VertexShaderT >
static bool	DrawGeometry (const Contents *contents, const Geometry *geometry, const ContentContext &renderer, const Entity &entity, RenderPass &pass, const PipelineBuilderCallback &pipeline_callback, typename VertexShaderT::FrameInfo frame_info, const BindFragmentCallback &bind_fragment_callback, bool force_stencil=false, const CreateGeometryCallback &create_geom_callback=DefaultCreateGeometryCallback)
Static Public Member Functions inherited from impeller::Contents
static std::shared_ptr< Contents >	MakeAnonymous (RenderProc render_proc, CoverageProc coverage_proc)

Protected Member Functions
bool	AppliesAlphaForStrokeCoverage (const Matrix &transform) const
	Whether the entity should be treated as non-opaque due to stroke geometry requiring alpha for coverage. More...
template<typename VertexShaderT >
bool	DrawGeometry (const ContentContext &renderer, const Entity &entity, RenderPass &pass, const PipelineBuilderCallback &pipeline_callback, typename VertexShaderT::FrameInfo frame_info, const BindFragmentCallback &bind_fragment_callback, bool force_stencil=false, const CreateGeometryCallback &create_geom_callback=DefaultCreateGeometryCallback) const

Static Protected Member Functions
static GeometryResult	DefaultCreateGeometryCallback (const ContentContext &renderer, const Entity &entity, RenderPass &pass, const Geometry *geom)

Detailed Description

Color sources are geometry-ignostic Contents capable of shading any area defined by an impeller::Geometry. Conceptually, impeller::ColorSourceContents implement a particular color shading behavior.

This separation of concerns between geometry and color source output allows Impeller to handle most possible draw combinations in a consistent way. For example: There are color sources for handling solid colors, gradients, textures, custom runtime effects, and even 3D scenes.

There are some special rendering exceptions that deviate from this pattern and cross geometry and color source concerns, such as text atlas and image atlas rendering. Special Contents exist for rendering these behaviors which don't implement ColorSourceContents.

See also

impeller::Geometry

Definition at line 38 of file color_source_contents.h.

Member Typedef Documentation

BindFragmentCallback

using impeller::ColorSourceContents::BindFragmentCallback = std::function<bool(RenderPass& pass)>

Definition at line 40 of file color_source_contents.h.

CreateGeometryCallback

using impeller::ColorSourceContents::CreateGeometryCallback = std::function<GeometryResult(const ContentContext& renderer, const Entity& entity, RenderPass& pass, const Geometry* geom)>

Definition at line 43 of file color_source_contents.h.

PipelineBuilderCallback

using impeller::ColorSourceContents::PipelineBuilderCallback = std::function<PipelineRef(ContentContextOptions)>

Definition at line 41 of file color_source_contents.h.

Constructor & Destructor Documentation

ColorSourceContents()

impeller::ColorSourceContents::ColorSourceContents ( )

default

~ColorSourceContents()

impeller::ColorSourceContents::~ColorSourceContents ( )

overridedefault

Member Function Documentation

AppliesAlphaForStrokeCoverage()

bool impeller::ColorSourceContents::AppliesAlphaForStrokeCoverage ( const Matrix &  transform ) const

protected

Whether the entity should be treated as non-opaque due to stroke geometry requiring alpha for coverage.

Definition at line 53 of file color_source_contents.cc.

                                   {
  return GetGeometry() && GetGeometry()->ComputeAlphaCoverage(transform) < 1.0;
}

References impeller::Geometry::ComputeAlphaCoverage(), GetGeometry(), and transform.

Referenced by impeller::LinearGradientContents::IsOpaque(), impeller::RadialGradientContents::IsOpaque(), impeller::SolidColorContents::IsOpaque(), impeller::SweepGradientContents::IsOpaque(), and impeller::TiledTextureContents::IsOpaque().

DefaultCreateGeometryCallback()

static GeometryResult impeller::ColorSourceContents::DefaultCreateGeometryCallback ( const ContentContext &  renderer, const Entity &  entity, RenderPass &  pass, const Geometry *  geom  )

inlinestaticprotected

Definition at line 260 of file color_source_contents.h.

                            {
    return geom->GetPositionBuffer(renderer, entity, pass);
  }

References impeller::Geometry::GetPositionBuffer().

DrawGeometry() [1/2]

template<typename VertexShaderT >

bool impeller::ColorSourceContents::DrawGeometry ( const ContentContext &  renderer, const Entity &  entity, RenderPass &  pass, const PipelineBuilderCallback &  pipeline_callback, typename VertexShaderT::FrameInfo  frame_info, const BindFragmentCallback &  bind_fragment_callback, bool  force_stencil = false, const CreateGeometryCallback &  create_geom_callback = DefaultCreateGeometryCallback  ) const

inlineprotected

Definition at line 273 of file color_source_contents.h.

                                                             {
    //
    return DrawGeometry<VertexShaderT>(this,                    //
                                       GetGeometry(),           //
                                       renderer,                //
                                       entity,                  //
                                       pass,                    //
                                       pipeline_callback,       //
                                       frame_info,              //
                                       bind_fragment_callback,  //
                                       force_stencil,           //
                                       create_geom_callback);
  }

References GetGeometry().

DrawGeometry() [2/2]

template<typename VertexShaderT >

static bool impeller::ColorSourceContents::DrawGeometry ( const Contents *  contents, const Geometry *  geometry, const ContentContext &  renderer, const Entity &  entity, RenderPass &  pass, const PipelineBuilderCallback &  pipeline_callback, typename VertexShaderT::FrameInfo  frame_info, const BindFragmentCallback &  bind_fragment_callback, bool  force_stencil = false, const CreateGeometryCallback &  create_geom_callback = DefaultCreateGeometryCallback  )

inlinestatic

Stencil preparation draw.

Cover draw.

Definition at line 113 of file color_source_contents.h.

                                                              {
    auto options = OptionsFromPassAndEntity(pass, entity);
 
    GeometryResult::Mode geometry_mode = geometry->GetResultMode();
    bool do_cover_draw = false;
    Rect cover_area = {};
 
    bool is_stencil_then_cover =
        geometry_mode == GeometryResult::Mode::kNonZero ||
        geometry_mode == GeometryResult::Mode::kEvenOdd;
    if (!is_stencil_then_cover && force_stencil) {
      geometry_mode = GeometryResult::Mode::kNonZero;
      is_stencil_then_cover = true;
    }
 
    if (is_stencil_then_cover) {
      pass.SetStencilReference(0);
 
      /// Stencil preparation draw.
 
      GeometryResult stencil_geometry_result =
          geometry->GetPositionBuffer(renderer, entity, pass);
      if (stencil_geometry_result.vertex_buffer.vertex_count == 0u) {
        return true;
      }
      pass.SetVertexBuffer(std::move(stencil_geometry_result.vertex_buffer));
      options.primitive_type = stencil_geometry_result.type;
 
      options.blend_mode = BlendMode::kDst;
      switch (stencil_geometry_result.mode) {
        case GeometryResult::Mode::kNonZero:
          pass.SetCommandLabel("Stencil preparation (NonZero)");
          options.stencil_mode =
              ContentContextOptions::StencilMode::kStencilNonZeroFill;
          break;
        case GeometryResult::Mode::kEvenOdd:
          pass.SetCommandLabel("Stencil preparation (EvenOdd)");
          options.stencil_mode =
              ContentContextOptions::StencilMode::kStencilEvenOddFill;
          break;
        default:
          if (force_stencil) {
            pass.SetCommandLabel("Stencil preparation (NonZero)");
            options.stencil_mode =
                ContentContextOptions::StencilMode::kStencilNonZeroFill;
            break;
          }
          FML_UNREACHABLE();
      }
      pass.SetPipeline(renderer.GetClipPipeline(options));
      ClipPipeline::VertexShader::FrameInfo clip_frame_info;
      clip_frame_info.depth = entity.GetShaderClipDepth();
      clip_frame_info.mvp = stencil_geometry_result.transform;
      ClipPipeline::VertexShader::BindFrameInfo(
          pass,
          renderer.GetTransientsDataBuffer().EmplaceUniform(clip_frame_info));
 
      if (!pass.Draw().ok()) {
        return false;
      }
 
      /// Cover draw.
 
      options.blend_mode = entity.GetBlendMode();
      options.stencil_mode = ContentContextOptions::StencilMode::kCoverCompare;
      std::optional<Rect> maybe_cover_area = geometry->GetCoverage({});
      if (!maybe_cover_area.has_value()) {
        return true;
      }
      do_cover_draw = true;
      cover_area = maybe_cover_area.value();
    }
 
    GeometryResult geometry_result;
    if (do_cover_draw) {
      FillRectGeometry geom(cover_area);
      geometry_result = create_geom_callback(renderer, entity, pass, &geom);
    } else {
      geometry_result = create_geom_callback(renderer, entity, pass, geometry);
    }
 
    if (geometry_result.vertex_buffer.vertex_count == 0u) {
      return true;
    }
    pass.SetVertexBuffer(std::move(geometry_result.vertex_buffer));
    options.primitive_type = geometry_result.type;
 
    // Enable depth writing for all opaque entities in order to allow
    // reordering. Opaque entities are coerced to source blending by
    // `EntityPass::AddEntity`.
    options.depth_write_enabled = options.blend_mode == BlendMode::kSrc;
 
    // Take the pre-populated vertex shader uniform struct and set managed
    // values.
    frame_info.mvp = geometry_result.transform;
 
    // If overdraw prevention is enabled (like when drawing stroke paths), we
    // increment the stencil buffer as we draw, preventing overlapping fragments
    // from drawing. Afterwards, we need to append another draw call to clean up
    // the stencil buffer (happens below in this method). This can be skipped
    // for draws that are fully opaque or use src blend mode.
    if (geometry_result.mode == GeometryResult::Mode::kPreventOverdraw &&
        options.blend_mode != BlendMode::kSrc) {
      options.stencil_mode =
          ContentContextOptions::StencilMode::kOverdrawPreventionIncrement;
    }
    pass.SetStencilReference(0);
 
    VertexShaderT::BindFrameInfo(
        pass, renderer.GetTransientsDataBuffer().EmplaceUniform(frame_info));
 
    // The reason we need to have a callback mechanism here is that this routine
    // may insert draw calls before the main draw call below. For example, for
    // sufficiently complex paths we may opt to use stencil-then-cover to avoid
    // tessellation.
    if (!bind_fragment_callback(pass)) {
      return false;
    }
 
    pass.SetPipeline(pipeline_callback(options));
 
    if (!pass.Draw().ok()) {
      return false;
    }
 
    // If we performed overdraw prevention, a subsection of the clip heightmap
    // was incremented by 1 in order to self-clip. So simply append a clip
    // restore to clean it up.
    if (geometry_result.mode == GeometryResult::Mode::kPreventOverdraw &&
        options.blend_mode != BlendMode::kSrc) {
      return RenderClipRestore(renderer, pass, entity.GetClipDepth(),
                               contents->GetCoverage(entity));
    }
    return true;
  }

References impeller::RenderPass::Draw(), impeller::HostBuffer::EmplaceUniform(), impeller::Entity::GetBlendMode(), impeller::Entity::GetClipDepth(), impeller::ContentContext::GetClipPipeline(), impeller::Contents::GetCoverage(), impeller::Geometry::GetCoverage(), impeller::Geometry::GetPositionBuffer(), impeller::Geometry::GetResultMode(), impeller::Entity::GetShaderClipDepth(), impeller::ContentContext::GetTransientsDataBuffer(), impeller::ContentContextOptions::kCoverCompare, impeller::kDst, impeller::GeometryResult::kEvenOdd, impeller::GeometryResult::kNonZero, impeller::ContentContextOptions::kOverdrawPreventionIncrement, impeller::GeometryResult::kPreventOverdraw, impeller::kSrc, impeller::ContentContextOptions::kStencilEvenOddFill, impeller::ContentContextOptions::kStencilNonZeroFill, impeller::GeometryResult::mode, impeller::OptionsFromPassAndEntity(), impeller::RenderClipRestore(), impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetStencilReference(), impeller::RenderPass::SetVertexBuffer(), impeller::GeometryResult::transform, impeller::GeometryResult::type, impeller::GeometryResult::vertex_buffer, and impeller::VertexBuffer::vertex_count.

GetCoverage()

std::optional< Rect > impeller::ColorSourceContents::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.

Reimplemented in impeller::SolidColorContents.

Definition at line 44 of file color_source_contents.cc.

                                {
  return geometry_->GetCoverage(entity.GetTransform());
};

References impeller::Geometry::GetCoverage(), and impeller::Entity::GetTransform().

Referenced by impeller::TiledTextureContents::RenderToSnapshot().

GetGeometry()

const Geometry * impeller::ColorSourceContents::GetGeometry

(

)

const

Get the geometry that this contents will use to render.

Definition at line 20 of file color_source_contents.cc.

                                                       {
  return geometry_;
}

Referenced by AppliesAlphaForStrokeCoverage(), impeller::SolidColorContents::AsBackgroundColor(), DrawGeometry(), impeller::SolidColorContents::GetCoverage(), impeller::SolidColorContents::Render(), impeller::TiledTextureContents::Render(), and impeller::TiledTextureContents::RenderToSnapshot().

GetInverseEffectTransform()

const Matrix & impeller::ColorSourceContents::GetInverseEffectTransform

(

)

const

Set the inverted effect transform for this color source.

     When the effect transform is set via `SetEffectTransform`, the
     value is inverted upon storage. The reason for this is that most
     color sources internally use the inverted transform.

Returns

The inverse of the transform set by SetEffectTransform.

See also

SetEffectTransform

Definition at line 36 of file color_source_contents.cc.

                                                                   {
  return inverse_matrix_;
}

Referenced by impeller::TiledTextureContents::Render(), and impeller::TiledTextureContents::RenderToSnapshot().

GetOpacityFactor()

Scalar impeller::ColorSourceContents::GetOpacityFactor

(

)

const

Get the opacity factor for this color source.

    This value is is factored into the output of the color source in
    addition to opacity information that may be supplied any other
    inputs.

Note

If set, the output of this method factors factors in the inherited opacity of this Contents.

Definition at line 28 of file color_source_contents.cc.

                                                   {
  return opacity_ * inherited_opacity_;
}

Referenced by impeller::SolidColorContents::GetColor(), impeller::LinearGradientContents::IsOpaque(), impeller::RadialGradientContents::IsOpaque(), impeller::SweepGradientContents::IsOpaque(), impeller::TiledTextureContents::IsOpaque(), impeller::TiledTextureContents::Render(), and impeller::TiledTextureContents::RenderToSnapshot().

IsSolidColor()

bool impeller::ColorSourceContents::IsSolidColor ( ) const

virtual

Reimplemented in impeller::SolidColorContents.

Definition at line 40 of file color_source_contents.cc.

                                             {
  return false;
}

SetEffectTransform()

void impeller::ColorSourceContents::SetEffectTransform

(

Matrix

matrix

)

Set the effect transform for this color source.

    The effect transform is a transform matrix that is applied to
    the shaded color output and does not impact geometry in any way.

    For example: With repeat tiling, any gradient or
    `TiledTextureContents` could be used with an effect transform to
    inexpensively draw an infinite scrolling background pattern.

Definition at line 32 of file color_source_contents.cc.

                                                          {
  inverse_matrix_ = matrix.Invert();
}

References impeller::Matrix::Invert().

SetGeometry()

void impeller::ColorSourceContents::SetGeometry

(

const Geometry *

geometry

)

Set the geometry that this contents will use to render.

Definition at line 16 of file color_source_contents.cc.

                                                              {
  geometry_ = geometry;
}

Referenced by impeller::testing::TEST_P().

SetInheritedOpacity()

void impeller::ColorSourceContents::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 49 of file color_source_contents.cc.

                                                            {
  inherited_opacity_ = opacity;
}

SetOpacityFactor()

void impeller::ColorSourceContents::SetOpacityFactor

(

Scalar

opacity

)

Set the opacity factor for this color source.

Definition at line 24 of file color_source_contents.cc.

                                                       {
  opacity_ = alpha;
}

---

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

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