Instances of external textures peered to android.graphics.SurfaceTexture. More...

#include <surface_texture_external_texture.h>

Inheritance diagram for flutter::SurfaceTextureExternalTexture:

Public Member Functions
	SurfaceTextureExternalTexture (int64_t id, const fml::jni::ScopedJavaGlobalRef< jobject > &surface_texture, const std::shared_ptr< PlatformViewAndroidJNI > &jni_facade)

	~SurfaceTextureExternalTexture () override

Public Member Functions inherited from flutter::Texture
	Texture (int64_t id)

virtual	~Texture ()

int64_t	Id ()

Public Member Functions inherited from flutter::ContextListener
	ContextListener ()

	~ContextListener ()

Protected Types
enum class	AttachmentState { kUninitialized , kAttached , kDetached }
	Specifies how this instance is bound to the underlying surface texture. More...

Protected Member Functions
virtual void	ProcessFrame (PaintContext &context, const SkRect &bounds)=0
	Subclasses override this method to bind the OpenGL texture resource represented by this surface texture to the package specific texture (SkImage, impeller::Texture, etc...).

virtual void	DrawFrame (PaintContext &context, const SkRect &bounds, const DlImageSampling sampling) const

const SkM44 &	GetCurrentUVTransformation () const
	Get the transformation that should be applied to the UV texture coordinates when sampling from this texture.

virtual void	Detach ()
	Provides an opportunity for the subclasses to sever the connection between the OpenGL texture resource represented by this surface texture and the underlying package handle (SkImage, impeller::Texture, etc...).

void	Attach (int gl_tex_id)
	Attaches the given OpenGL texture handle to the surface texture via a bind operation.

bool	ShouldUpdate ()

void	Update ()
	Update the surface texture contents and transformation matrix.

Protected Attributes
std::shared_ptr< PlatformViewAndroidJNI >	jni_facade_

fml::jni::ScopedJavaGlobalRef< jobject >	surface_texture_

AttachmentState	state_ = AttachmentState::kUninitialized

sk_sp< flutter::DlImage >	dl_image_

Detailed Description

Instances of external textures peered to android.graphics.SurfaceTexture.

SurfaceTextures are used on older versions of Android (API < 29). On newer versions, the Android Hardware Buffer backend flutter::ImageExternalTexture instances are used instead.

Due to the way surface textures are designed, it is not possible to have a Vulkan renderer interoperate with such textures. Consequently, both Skia and Impeller only have OpenGL implementations for these kinds of textures.

This is an abstract base class. Minimally, subclasses override the pure virtual ProcessFrame method to bind the package specific texture implementation to the surface texture.

Definition at line 33 of file surface_texture_external_texture.h.

Member Enumeration Documentation

◆ AttachmentState

enum class flutter::SurfaceTextureExternalTexture::AttachmentState

strongprotected

Specifies how this instance is bound to the underlying surface texture.

Enumerator
kUninitialized
kAttached
kDetached

Definition at line 107 of file surface_texture_external_texture.h.

107{ kUninitialized, kAttached, kDetached };

flutter::SurfaceTextureExternalTexture::AttachmentState::kUninitialized

@ kUninitialized

flutter::SurfaceTextureExternalTexture::AttachmentState::kDetached

@ kDetached

flutter::SurfaceTextureExternalTexture::AttachmentState::kAttached

@ kAttached

Constructor & Destructor Documentation

◆ SurfaceTextureExternalTexture()

flutter::SurfaceTextureExternalTexture::SurfaceTextureExternalTexture	(	int64_t	id,
		const fml::jni::ScopedJavaGlobalRef< jobject > &	surface_texture,
		const std::shared_ptr< PlatformViewAndroidJNI > &	jni_facade
	)

Definition at line 19 of file surface_texture_external_texture.cc.

    : Texture(id),
      jni_facade_(jni_facade),
      surface_texture_(surface_texture),
      transform_(SkMatrix::I()) {}

◆ ~SurfaceTextureExternalTexture()

flutter::SurfaceTextureExternalTexture::~SurfaceTextureExternalTexture ( )

override

Definition at line 28 of file surface_texture_external_texture.cc.

28{}

Member Function Documentation

◆ Attach()

void flutter::SurfaceTextureExternalTexture::Attach ( int gl_tex_id )

protected

Attaches the given OpenGL texture handle to the surface texture via a bind operation.

@important It is the responsibility of the subclass to ensure that a context is current when this call is made. Subclass can do this by overriding this method, making the context current in the implementation and calling the base class method.

Parameters

[in] gl_tex_id The gl tex identifier

Definition at line 123 of file surface_texture_external_texture.cc.

                                                        {
  jni_facade_->SurfaceTextureAttachToGLContext(
      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_), gl_tex_id);
  state_ = AttachmentState::kAttached;
}

References jni_facade_, kAttached, state_, and surface_texture_.

◆ Detach()

void flutter::SurfaceTextureExternalTexture::Detach ( )

protectedvirtual

Provides an opportunity for the subclasses to sever the connection between the OpenGL texture resource represented by this surface texture and the underlying package handle (SkImage, impeller::Texture, etc...).

@important It is the responsibility of the subclass to ensure that a context is current when this call is made. Subclass can do this by overriding this method, making the context current in the implementation and calling the base class method.

Definition at line 117 of file surface_texture_external_texture.cc.

                                           {
  jni_facade_->SurfaceTextureDetachFromGLContext(
      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_));
  dl_image_.reset();
}

References dl_image_, jni_facade_, and surface_texture_.

◆ DrawFrame()

void flutter::SurfaceTextureExternalTexture::DrawFrame	(	PaintContext &	context,
		const SkRect &	bounds,
		const DlImageSampling	sampling
	)		const

protectedvirtual

Definition at line 64 of file surface_texture_external_texture.cc.

                                          {
  auto transform = ToDlMatrix(GetCurrentUVTransformation());
 
  // Android's SurfaceTexture transform matrix works on texture coordinate
  // lookups in the range 0.0-1.0, while Skia's Shader transform matrix works on
  // the image itself, as if it were inscribed inside a clip rect.
  // An Android transform that scales lookup by 0.5 (displaying 50% of the
  // texture) is the same as a Skia transform by 2.0 (scaling 50% of the image
  // outside of the virtual "clip rect"), so we invert the incoming matrix.
 
  if (transform.IsIdentity()) {
    context.canvas->DrawImage(dl_image_, DlPoint{0, 0}, sampling,
                              context.paint);
    return;
  }
 
  if (!transform.IsInvertible()) {
    FML_LOG(FATAL)
        << "Invalid (not invertable) SurfaceTexture transformation matrix";
  }
  transform = transform.Invert();
 
  DlAutoCanvasRestore autoRestore(context.canvas, true);
 
  // The incoming texture is vertically flipped, so we flip it
  // back. OpenGL's coordinate system has Positive Y equivalent to up, while
  // Skia's coordinate system has Negative Y equvalent to up.
  context.canvas->Translate(bounds.x(), bounds.y() + bounds.height());
  context.canvas->Scale(bounds.width(), -bounds.height());
 
  auto source = DlColorSource::MakeImage(
      dl_image_, DlTileMode::kClamp, DlTileMode::kClamp, sampling, &transform);
 
  DlPaint paintWithShader;
  if (context.paint) {
    paintWithShader = *context.paint;
  }
  paintWithShader.setColorSource(source);
  context.canvas->DrawRect(DlRect::MakeWH(1, 1), paintWithShader);
}

References flutter::Texture::PaintContext::canvas, dl_image_, flutter::DlCanvas::DrawImage(), flutter::DlCanvas::DrawRect(), FML_LOG, GetCurrentUVTransformation(), flutter::kClamp, flutter::DlColorSource::MakeImage(), impeller::TRect< Scalar >::MakeWH(), flutter::Texture::PaintContext::paint, flutter::DlCanvas::Scale(), flutter::DlPaint::setColorSource(), flutter::ToDlMatrix(), transform, and flutter::DlCanvas::Translate().

◆ GetCurrentUVTransformation()

const SkM44 & flutter::SurfaceTextureExternalTexture::GetCurrentUVTransformation ( ) const

protected

Get the transformation that should be applied to the UV texture coordinates when sampling from this texture.

Returns: The current uv transformation.

Definition at line 141 of file surface_texture_external_texture.cc.

                                                                             {
  return transform_;
}

Referenced by DrawFrame().

◆ ProcessFrame()

virtual void flutter::SurfaceTextureExternalTexture::ProcessFrame	(	PaintContext &	context,
		const SkRect &	bounds
	)

protectedpure virtual

Subclasses override this method to bind the OpenGL texture resource represented by this surface texture to the package specific texture (SkImage, impeller::Texture, etc...).

@important The state of texture should be AttachmentState::kAttached after a call to this method. That is the responsibility of the subclass.

Parameters

	context	The context.
[in]	bounds	The bounds of the texture.

◆ ShouldUpdate()

bool flutter::SurfaceTextureExternalTexture::ShouldUpdate ( )

protected

Definition at line 129 of file surface_texture_external_texture.cc.

                                                 {
  return jni_facade_->SurfaceTextureShouldUpdate(
      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_));
}

References jni_facade_, and surface_texture_.

◆ Update()

void flutter::SurfaceTextureExternalTexture::Update ( )

protected

Update the surface texture contents and transformation matrix.

Definition at line 134 of file surface_texture_external_texture.cc.

                                           {
  jni_facade_->SurfaceTextureUpdateTexImage(
      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_));
  transform_ = jni_facade_->SurfaceTextureGetTransformMatrix(
      fml::jni::ScopedJavaLocalRef<jobject>(surface_texture_));
}