impeller::Entity Class Reference

#include <entity.h>

Public Types
enum class	RenderingMode {   kDirect ,   kSubpassAppendSnapshotTransform ,   kSubpassPrependSnapshotTransform }
enum class	TileMode {   kClamp ,   kRepeat ,   kMirror ,   kDecal }
enum class	ClipOperation {   kDifference ,   kIntersect }

Public Member Functions
	Entity ()
	~Entity ()
	Entity (Entity &&)
Entity &	operator= (Entity &&)
const Matrix &	GetTransform () const
	Get the global transform matrix for this Entity. More...
Matrix	GetShaderTransform (const RenderPass &pass) const
void	SetTransform (const Matrix &transform)
	Set the global transform matrix for this Entity. More...
std::optional< Rect >	GetCoverage () const
void	SetContents (std::shared_ptr< Contents > contents)
const std::shared_ptr< Contents > &	GetContents () const
void	SetClipDepth (uint32_t clip_depth)
uint32_t	GetClipDepth () const
float	GetShaderClipDepth () const
void	SetBlendMode (BlendMode blend_mode)
BlendMode	GetBlendMode () const
bool	Render (const ContentContext &renderer, RenderPass &parent_pass) const
bool	SetInheritedOpacity (Scalar alpha)
std::optional< Color >	AsBackgroundColor (ISize target_size) const
Entity	Clone () const

Static Public Member Functions
static Entity	FromSnapshot (const Snapshot &snapshot, BlendMode blend_mode=BlendMode::kSrcOver)
	Create an entity that can be used to render a given snapshot. More...
static Matrix	GetShaderTransform (Scalar clip_depth, const RenderPass &pass, const Matrix &transform)
	Static utility that computes the vertex shader transform used for drawing an Entity with a given the clip depth and RenderPass size. More...
static float	GetShaderClipDepth (uint32_t clip_depth)
static bool	IsBlendModeDestructive (BlendMode blend_mode)
	Returns true if the blend mode is "destructive", meaning that even fully transparent source colors would result in the destination getting changed. More...

Static Public Attributes
static constexpr BlendMode	kLastPipelineBlendMode = BlendMode::kModulate
static constexpr BlendMode	kLastAdvancedBlendMode = BlendMode::kLuminosity
static constexpr Scalar	kDepthEpsilon = 1.0f / 262144.0

Detailed Description

Represents a renderable object within the Impeller scene.

An Entity combines graphical content (Contents) with properties like transformation (Matrix), blend mode (BlendMode), and stencil clip depth. It serves as the primary unit for constructing and rendering scenes. Entities can be created directly or from Snapshot objects.

Definition at line 26 of file entity.h.

Member Enumeration Documentation

ClipOperation

enum impeller::Entity::ClipOperation

strong

Enumerator
kDifference
kIntersect

Definition at line 67 of file entity.h.

                           {
    kDifference,
    kIntersect,
  };

RenderingMode

enum impeller::Entity::RenderingMode

strong

Enumerator
kDirect	In direct mode, the Entity's transform is used as the current local-to-screen transform matrix.
kSubpassAppendSnapshotTransform	In subpass mode, the Entity passed through the filter is in screen space rather than local space, and so some filters (namely, MatrixFilterContents) need to interpret the given EffectTransform as the current transform matrix.
kSubpassPrependSnapshotTransform

Definition at line 33 of file entity.h.

                           {
    /// In direct mode, the Entity's transform is used as the current
    /// local-to-screen transform matrix.
    kDirect,
    /// In subpass mode, the Entity passed through the filter is in screen space
    /// rather than local space, and so some filters (namely,
    /// MatrixFilterContents) need to interpret the given EffectTransform as the
    /// current transform matrix.
    kSubpassAppendSnapshotTransform,
    kSubpassPrependSnapshotTransform,
  };

TileMode

enum impeller::Entity::TileMode

strong

An enum to define how to repeat, fold, or omit colors outside of the typically defined range of the source of the colors (such as the bounds of an image or the defining geometry of a gradient).

Enumerator
kClamp	Replicate the edge color if the shader draws outside of its original bounds.
kRepeat	Repeat the shader's image horizontally and vertically (or both along and perpendicular to a gradient's geometry).
kMirror	Repeat the shader's image horizontally and vertically, seamlessly alternating mirrored images.
kDecal	Render the shader's image pixels only within its original bounds. If the shader draws outside of its original bounds, transparent black is drawn instead.

Definition at line 48 of file entity.h.

                      {
    /// Replicate the edge color if the shader draws outside of its original
    /// bounds.
    kClamp,
 
    /// Repeat the shader's image horizontally and vertically (or both along and
    /// perpendicular to a gradient's geometry).
    kRepeat,
 
    /// Repeat the shader's image horizontally and vertically, seamlessly
    /// alternating mirrored images.
    kMirror,
 
    /// Render the shader's image pixels only within its original bounds. If the
    /// shader draws outside of its original bounds, transparent black is drawn
    /// instead.
    kDecal,
  };

Constructor & Destructor Documentation

Entity() [1/2]

impeller::Entity::Entity ( )

default

Referenced by Clone().

~Entity()

impeller::Entity::~Entity ( )

default

Entity() [2/2]

impeller::Entity::Entity ( Entity &&  )

default

Member Function Documentation

AsBackgroundColor()

std::optional< Color > impeller::Entity::AsBackgroundColor

(

ISize

target_size

)

const

Attempts to represent this entity as a solid background color.

This is an optimization. If the entity's contents can be represented as a solid color covering the entire target area, this method returns that color.

Parameters

[in]

target_size

The size of the render target.

Returns

The background color if representable, otherwise std::nullopt.

Definition at line 116 of file entity.cc.

                                                                    {
  return contents_->AsBackgroundColor(*this, target_size);
}

Clone()

Entity impeller::Entity::Clone

(

)

const

Definition at line 158 of file entity.cc.

                           {
  return Entity(*this);
}

References Entity().

Referenced by impeller::FilterContents::GetCoverage(), impeller::FilterContents::GetEntity(), impeller::FilterInput::GetLocalCoverage(), and impeller::TextShadowCache::Lookup().

FromSnapshot()

Entity impeller::Entity::FromSnapshot ( const Snapshot &  snapshot, BlendMode  blend_mode = BlendMode::kSrcOver  )

static

Create an entity that can be used to render a given snapshot.

Definition at line 18 of file entity.cc.

                                                                          {
  auto texture_rect = Rect::MakeSize(snapshot.texture->GetSize());
 
  auto contents = TextureContents::MakeRect(texture_rect);
  contents->SetTexture(snapshot.texture);
  contents->SetSamplerDescriptor(snapshot.sampler_descriptor);
  contents->SetSourceRect(texture_rect);
  contents->SetOpacity(snapshot.opacity);
 
  Entity entity;
  entity.SetBlendMode(blend_mode);
  entity.SetTransform(snapshot.transform);
  entity.SetContents(contents);
  return entity;
}

References impeller::TextureContents::MakeRect(), impeller::TRect< Scalar >::MakeSize(), impeller::Snapshot::opacity, impeller::Snapshot::sampler_descriptor, SetBlendMode(), SetContents(), SetTransform(), impeller::Snapshot::texture, and impeller::Snapshot::transform.

Referenced by impeller::AdvancedBlend(), and impeller::PipelineBlend().

GetBlendMode()

BlendMode impeller::Entity::GetBlendMode

(

)

const

Definition at line 101 of file entity.cc.

                                     {
  return blend_mode_;
}

Referenced by impeller::AdvancedBlend(), impeller::ColorSourceContents::DrawGeometry(), impeller::OptionsFromPassAndEntity(), impeller::PipelineBlend(), impeller::SolidRRectLikeBlurContents::Render(), impeller::Canvas::Restore(), and impeller::testing::TEST_P().

GetClipDepth()

uint32_t impeller::Entity::GetClipDepth

(

)

const

Gets the stencil clip depth level for this entity.

See also

SetClipDepth(uint32_t)

GetShaderClipDepth()

Returns

The current integer clip depth level.

Definition at line 84 of file entity.cc.

                                    {
  return clip_depth_;
}

Referenced by impeller::ColorSourceContents::DrawGeometry(), impeller::TextShadowCache::Lookup(), and impeller::FilterContents::Render().

GetContents()

const std::shared_ptr< Contents > & impeller::Entity::GetContents

(

)

const

Definition at line 76 of file entity.cc.

                                                         {
  return contents_;
}

Referenced by impeller::AdvancedBlend(), impeller::ContentsFilterInput::GetSnapshot(), impeller::PipelineBlend(), and impeller::Canvas::Restore().

GetCoverage()

std::optional< Rect > impeller::Entity::GetCoverage

(

)

const

Calculates the axis-aligned bounding box covering this entity after its transformation is applied.

Returns

The coverage rectangle in the parent coordinate space, or std::nullopt if the entity has no contents.

Definition at line 64 of file entity.cc.

                                            {
  if (!contents_) {
    return std::nullopt;
  }
 
  return contents_->GetCoverage(*this);
}

Referenced by impeller::TextShadowCache::Lookup(), impeller::Canvas::Restore(), impeller::testing::TEST(), and impeller::testing::TEST_P().

GetShaderClipDepth() [1/2]

Scalar impeller::Entity::GetShaderClipDepth

(

)

const

Gets the shader-compatible depth value based on the entity's current clip depth level (clip_depth_).

See also

GetShaderClipDepth(uint32_t) for details on the conversion logic.

Returns

The floating-point depth value for shaders corresponding to the entity's clip_depth_.

Definition at line 88 of file entity.cc.

                                        {
  return Entity::GetShaderClipDepth(clip_depth_);
}

Referenced by impeller::ColorSourceContents::DrawGeometry(), impeller::GetShaderClipDepth(), GetShaderTransform(), impeller::SolidRRectLikeBlurContents::Render(), and impeller::TextContents::Render().

GetShaderClipDepth() [2/2]

Scalar impeller::Entity::GetShaderClipDepth ( uint32_t  clip_depth )

static

Converts an integer clip depth level into a floating-point depth value suitable for use in shaders.

The integer clip_depth represents discrete layers used for stencil clipping. This function maps that integer to a depth value within the [0, 1) range for the depth buffer. Each increment in clip_depth corresponds to a small step (kDepthEpsilon) in the shader depth.

The result is clamped to ensure it stays within the valid depth range and slightly below 1.0 to avoid potential issues with the maximum depth value.

Parameters

[in]

clip_depth

The integer clip depth level.

Returns

The corresponding floating-point depth value for shaders.

Definition at line 92 of file entity.cc.

                                                     {
  Scalar result = std::clamp(clip_depth * kDepthEpsilon, 0.0f, 1.0f);
  return std::min(result, 1.0f - kDepthEpsilon);
}

References kDepthEpsilon.

GetShaderTransform() [1/2]

Matrix impeller::Entity::GetShaderTransform

(

const RenderPass &

pass

)

const

Calculates the final transformation matrix for rendering in a shader.

This combines the entity's transform with the render pass's orthographic projection and applies the necessary adjustments based on the entity's shader clip depth.

Parameters

[in]

pass

The current render pass.

Returns

The combined model-view-projection matrix for the shader.

Definition at line 48 of file entity.cc.

                                                              {
  return Entity::GetShaderTransform(GetShaderClipDepth(), pass, transform_);
}

References GetShaderClipDepth().

Referenced by impeller::Geometry::ComputePositionGeometry(), impeller::DlVerticesGeometry::GetPositionBuffer(), impeller::FillRectGeometry::GetPositionBuffer(), impeller::StrokeRectGeometry::GetPositionBuffer(), impeller::DlVerticesGeometry::GetPositionUVColorBuffer(), impeller::AtlasContents::Render(), impeller::ColorFilterAtlasContents::Render(), impeller::SolidRRectLikeBlurContents::Render(), impeller::TextContents::Render(), and impeller::TextureContents::Render().

GetShaderTransform() [2/2]

Matrix impeller::Entity::GetShaderTransform ( Scalar  clip_depth, const RenderPass &  pass, const Matrix &  transform  )

static

Static utility that computes the vertex shader transform used for drawing an Entity with a given the clip depth and RenderPass size.

Definition at line 52 of file entity.cc.

                                                           {
  return Matrix::MakeTranslateScale({1, 1, Entity::kDepthEpsilon},
                                    {0, 0, shader_clip_depth}) *
         pass.GetOrthographicTransform() * transform;
}

References impeller::RenderPass::GetOrthographicTransform(), kDepthEpsilon, impeller::Matrix::MakeTranslateScale(), and transform.

GetTransform()

const Matrix & impeller::Entity::GetTransform

(

)

const

Get the global transform matrix for this Entity.

Definition at line 44 of file entity.cc.

                                         {
  return transform_;
}

Referenced by impeller::SolidColorContents::AsBackgroundColor(), impeller::AtlasContents::GetCoverage(), impeller::ColorFilterAtlasContents::GetCoverage(), impeller::ColorSourceContents::GetCoverage(), impeller::FilterContents::GetCoverage(), impeller::LineContents::GetCoverage(), impeller::SolidColorContents::GetCoverage(), impeller::SolidRRectLikeBlurContents::GetCoverage(), impeller::TextContents::GetCoverage(), impeller::TextureContents::GetCoverage(), impeller::VerticesSimpleBlendContents::GetCoverage(), impeller::FilterContents::GetEntity(), impeller::FilterContentsFilterInput::GetLocalTransform(), impeller::StrokeRectGeometry::GetPositionBuffer(), impeller::FilterInput::GetTransform(), impeller::FilterContentsFilterInput::GetTransform(), impeller::TextShadowCache::Lookup(), impeller::LineContents::Render(), impeller::SolidColorContents::Render(), impeller::SolidRRectLikeBlurContents::Render(), impeller::TextContents::Render(), impeller::TiledTextureContents::Render(), impeller::Contents::RenderToSnapshot(), impeller::TextureContents::RenderToSnapshot(), impeller::Canvas::Restore(), SetInheritedOpacity(), and impeller::testing::TEST_P().

IsBlendModeDestructive()

bool impeller::Entity::IsBlendModeDestructive ( BlendMode  blend_mode )

static

Returns true if the blend mode is "destructive", meaning that even fully transparent source colors would result in the destination getting changed.

This is useful for determining if EntityPass textures can be shrinkwrapped to their Entities' coverage; they can be shrinkwrapped if all of the contained Entities have non-destructive blends.

Definition at line 127 of file entity.cc.

                                                        {
  switch (blend_mode) {
    case BlendMode::kClear:
    case BlendMode::kSrc:
    case BlendMode::kSrcIn:
    case BlendMode::kDstIn:
    case BlendMode::kSrcOut:
    case BlendMode::kDstOut:
    case BlendMode::kDstATop:
    case BlendMode::kXor:
    case BlendMode::kModulate:
      return true;
    default:
      return false;
  }
}

References impeller::kClear, impeller::kDstATop, impeller::kDstIn, impeller::kDstOut, impeller::kModulate, impeller::kSrc, impeller::kSrcIn, impeller::kSrcOut, and impeller::kXor.

Referenced by impeller::Canvas::SaveLayer().

operator=()

Entity & impeller::Entity::operator= ( Entity &&  )

default

Render()

bool impeller::Entity::Render	(	const ContentContext &	renderer,
		RenderPass &	parent_pass
	)		const

Definition at line 144 of file entity.cc.

                                                   {
  if (!contents_) {
    return true;
  }
 
  if (!contents_->GetCoverageHint().has_value()) {
    contents_->SetCoverageHint(
        Rect::MakeSize(parent_pass.GetRenderTargetSize()));
  }
 
  return contents_->Render(renderer, *this, parent_pass);
}

References impeller::RenderPass::GetRenderTargetSize(), and impeller::TRect< Scalar >::MakeSize().

Referenced by impeller::EntityPlayground::OpenPlaygroundHere(), impeller::PipelineBlend(), impeller::Canvas::Restore(), impeller::Canvas::SaveLayer(), and impeller::testing::TEST_P().

SetBlendMode()

void impeller::Entity::SetBlendMode

(

BlendMode

blend_mode

)

Definition at line 97 of file entity.cc.

                                              {
  blend_mode_ = blend_mode;
}

Referenced by impeller::Canvas::DrawArc(), impeller::Canvas::DrawAtlas(), impeller::Canvas::DrawCircle(), impeller::Canvas::DrawDashedLine(), impeller::Canvas::DrawDiffRoundRect(), impeller::Canvas::DrawImageRect(), impeller::Canvas::DrawLine(), impeller::Canvas::DrawOval(), impeller::Canvas::DrawPaint(), impeller::Canvas::DrawPath(), impeller::Canvas::DrawPoints(), impeller::Canvas::DrawRect(), impeller::Canvas::DrawRoundRect(), impeller::Canvas::DrawRoundSuperellipse(), impeller::Canvas::DrawTextFrame(), impeller::Canvas::DrawVertices(), FromSnapshot(), impeller::DlImageImpeller::MakeFromYUVTextures(), impeller::PipelineBlend(), impeller::Contents::RenderToSnapshot(), impeller::Canvas::Restore(), impeller::Canvas::SaveLayer(), and impeller::testing::TEST_P().

SetClipDepth()

void impeller::Entity::SetClipDepth

(

uint32_t

clip_depth

)

Sets the stencil clip depth for this entity.

The clip depth determines the entity's level within a stack of stencil clips. Higher values indicate the entity is nested deeper within clips. This value is used during rendering to configure stencil buffer operations.

Parameters

[in]

clip_depth

The integer clip depth level.

Definition at line 80 of file entity.cc.

                                             {
  clip_depth_ = clip_depth;
}

Referenced by impeller::Canvas::ClipGeometry(), impeller::Canvas::DrawTextFrame(), impeller::TextShadowCache::Lookup(), impeller::Canvas::Restore(), and impeller::Canvas::SaveLayer().

SetContents()

void impeller::Entity::SetContents

(

std::shared_ptr< Contents >

contents

)

Definition at line 72 of file entity.cc.

                                                         {
  contents_ = std::move(contents);
}

Referenced by impeller::Canvas::DrawAtlas(), impeller::Canvas::DrawImageRect(), impeller::Canvas::DrawLine(), impeller::Canvas::DrawTextFrame(), impeller::Canvas::DrawVertices(), FromSnapshot(), impeller::PipelineBlend(), impeller::Canvas::Restore(), impeller::Canvas::SaveLayer(), and impeller::testing::TEST_P().

SetInheritedOpacity()

bool impeller::Entity::SetInheritedOpacity

(

Scalar

alpha

)

Definition at line 105 of file entity.cc.

                                             {
  if (alpha >= 1.0) {
    return true;
  }
  if (blend_mode_ == BlendMode::kSrc && contents_->IsOpaque(GetTransform())) {
    blend_mode_ = BlendMode::kSrcOver;
  }
  contents_->SetInheritedOpacity(alpha);
  return true;
}

References GetTransform(), impeller::kSrc, and impeller::kSrcOver.

SetTransform()

void impeller::Entity::SetTransform

(

const Matrix &

transform

)

Set the global transform matrix for this Entity.

Definition at line 60 of file entity.cc.

                                                 {
  transform_ = transform;
}

References transform.

Referenced by impeller::Canvas::ClipGeometry(), impeller::Canvas::DrawArc(), impeller::Canvas::DrawAtlas(), impeller::Canvas::DrawCircle(), impeller::Canvas::DrawDashedLine(), impeller::Canvas::DrawDiffRoundRect(), impeller::Canvas::DrawImageRect(), impeller::Canvas::DrawLine(), impeller::Canvas::DrawOval(), impeller::Canvas::DrawPaint(), impeller::Canvas::DrawPath(), impeller::Canvas::DrawPoints(), impeller::Canvas::DrawRect(), impeller::Canvas::DrawRoundRect(), impeller::Canvas::DrawRoundSuperellipse(), impeller::Canvas::DrawTextFrame(), impeller::Canvas::DrawVertices(), FromSnapshot(), impeller::FilterContents::GetCoverage(), impeller::FilterContents::GetEntity(), impeller::FilterInput::GetLocalCoverage(), impeller::TextShadowCache::Lookup(), impeller::Contents::RenderToSnapshot(), impeller::Canvas::Restore(), impeller::Canvas::SaveLayer(), impeller::testing::TEST(), and impeller::testing::TEST_P().

Member Data Documentation

kDepthEpsilon

constexpr Scalar impeller::Entity::kDepthEpsilon = 1.0f / 262144.0

staticconstexpr

Definition at line 31 of file entity.h.

Referenced by GetShaderClipDepth(), and GetShaderTransform().

kLastAdvancedBlendMode

constexpr BlendMode impeller::Entity::kLastAdvancedBlendMode = BlendMode::kLuminosity

staticconstexpr

Definition at line 29 of file entity.h.

Referenced by impeller::testing::GetBlendModeSelection(), impeller::ColorFilterContents::MakeBlend(), and impeller::BlendFilterContents::SetBlendMode().

kLastPipelineBlendMode

constexpr BlendMode impeller::Entity::kLastPipelineBlendMode = BlendMode::kModulate

staticconstexpr

Definition at line 28 of file entity.h.

Referenced by impeller::ContentContextOptions::ApplyToPipelineDescriptor(), impeller::ColorFilterContents::MakeBlend(), impeller::VerticesSimpleBlendContents::Render(), impeller::RequiresReadbackForBlends(), impeller::Canvas::Restore(), impeller::BlendFilterContents::SetBlendMode(), and impeller::testing::TEST_P().

---

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

• impeller/entity/entity.h
• impeller/entity/entity.cc