impeller::Snapshot Struct Reference

Represents a texture and its intended draw transform/sampler configuration. More...

#include <snapshot.h>

Public Member Functions
bool	ShouldRasterizeForRuntimeEffects () const
std::optional< Rect >	GetCoverage () const
std::optional< Matrix >	GetUVTransform () const
	Get the transform that converts screen space coordinates to the UV space of this snapshot. More...
std::optional< std::array< Point, 4 > >	GetCoverageUVs (const Rect &coverage) const
	Map a coverage rect to this filter input's UV space. Result order: Top left, top right, bottom left, bottom right. More...

Public Attributes
std::shared_ptr< Texture >	texture
Matrix	transform
	The transform that should be applied to this texture for rendering. More...
SamplerDescriptor	sampler_descriptor
Scalar	opacity = 1.0f
bool	needs_rasterization_for_runtime_effects = false
	Whether this snapshot needs to be re-rasterized when used as an input to a runtime effect. More...

Detailed Description

Represents a texture and its intended draw transform/sampler configuration.

Definition at line 24 of file snapshot.h.

Member Function Documentation

GetCoverage()

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

(

)

const

Definition at line 11 of file snapshot.cc.

                                              {
  if (!texture) {
    return std::nullopt;
  }
  return Rect::MakeSize(texture->GetSize()).TransformBounds(transform);
}

References impeller::TRect< Scalar >::MakeSize(), texture, transform, and impeller::TRect< T >::TransformBounds().

GetCoverageUVs()

std::optional< std::array< Point, 4 > > impeller::Snapshot::GetCoverageUVs

(

const Rect &

coverage

)

const

Map a coverage rect to this filter input's UV space. Result order: Top left, top right, bottom left, bottom right.

Definition at line 26 of file snapshot.cc.

                                {
  auto uv_transform = GetUVTransform();
  if (!uv_transform.has_value()) {
    return std::nullopt;
  }
  return coverage.GetTransformedPoints(uv_transform.value());
}

References impeller::TRect< T >::GetTransformedPoints(), and GetUVTransform().

GetUVTransform()

std::optional< Matrix > impeller::Snapshot::GetUVTransform

(

)

const

Get the transform that converts screen space coordinates to the UV space of this snapshot.

Definition at line 18 of file snapshot.cc.

                                                   {
  if (!texture || texture->GetSize().IsEmpty()) {
    return std::nullopt;
  }
  return Matrix::MakeScale(1 / Vector2(texture->GetSize())) *
         transform.Invert();
}

References impeller::Matrix::Invert(), impeller::Matrix::MakeScale(), texture, and transform.

Referenced by GetCoverageUVs().

ShouldRasterizeForRuntimeEffects()

bool impeller::Snapshot::ShouldRasterizeForRuntimeEffects ( ) const

inline

Any snapshot that is scaled should re-rasterize because we should be performing the RuntimeEffect at the resolution of the screen, not the scaled up or scaled down version of the snapshot.

Definition at line 51 of file snapshot.h.

                                                {
    // If the transform has a rotation we don't re-rasterize because we'll lose
    // the rotation.
    // TODO(tbd): We should re-rasterize scaled and rotated snapshots.
    return (!transform.IsTranslationOnly() &&
            transform.IsTranslationScaleOnly()) ||
           needs_rasterization_for_runtime_effects;
  }

References impeller::Matrix::IsTranslationOnly(), impeller::Matrix::IsTranslationScaleOnly(), needs_rasterization_for_runtime_effects, and transform.

Member Data Documentation

needs_rasterization_for_runtime_effects

bool impeller::Snapshot::needs_rasterization_for_runtime_effects = false

Whether this snapshot needs to be re-rasterized when used as an input to a runtime effect.

This is required because there is no good heuristic to determine if a Snapshot needs to be rerasterized before applying a RuntimeFilter. In particular the GaussianBlurContents will return a Snapshot that includes padding for the blur halo which is not possible for the RuntimeEffectContents to know about. This value will tell RuntimeEffectContents that the Snapshot will have to be rerasterized to capture the padding.

Definition at line 46 of file snapshot.h.

Referenced by impeller::Entity::FromSnapshot(), and ShouldRasterizeForRuntimeEffects().

opacity

Scalar impeller::Snapshot::opacity = 1.0f

Definition at line 35 of file snapshot.h.

Referenced by impeller::Entity::FromSnapshot().

sampler_descriptor

SamplerDescriptor impeller::Snapshot::sampler_descriptor

Initial value:

=
      SamplerDescriptor("Default Snapshot Sampler",
                        MinMagFilter::kLinear,
                        MinMagFilter::kLinear,
                        MipFilter::kNearest)

Definition at line 29 of file snapshot.h.

Referenced by impeller::Entity::FromSnapshot(), and impeller::Canvas::SaveLayer().

texture

std::shared_ptr<Texture> impeller::Snapshot::texture

Definition at line 25 of file snapshot.h.

Referenced by impeller::AdvancedBlend(), impeller::Entity::FromSnapshot(), GetCoverage(), impeller::TextureFilterInput::GetSnapshot(), GetUVTransform(), impeller::PipelineBlend(), impeller::Contents::RenderToSnapshot(), impeller::TextureContents::RenderToSnapshot(), impeller::TiledTextureContents::RenderToSnapshot(), and impeller::Canvas::SaveLayer().

transform

Matrix impeller::Snapshot::transform

The transform that should be applied to this texture for rendering.

Definition at line 27 of file snapshot.h.

Referenced by impeller::Entity::FromSnapshot(), GetCoverage(), GetUVTransform(), impeller::Canvas::SaveLayer(), and ShouldRasterizeForRuntimeEffects().

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

• impeller/renderer/snapshot.h
• impeller/renderer/snapshot.cc