To do anything rendering related with Impeller, you need a context. More...

#include <context.h>

Inheritance diagram for impeller::Context:

Public Types
enum	BackendType { BackendType::kMetal, BackendType::kOpenGLES, BackendType::kVulkan }

Public Member Functions
virtual	~Context ()
	Destroys an Impeller context. More...

virtual BackendType	GetBackendType () const =0
	Get the graphics backend of an Impeller context. More...

virtual std::string	DescribeGpuModel () const =0

virtual bool	IsValid () const =0
	Determines if a context is valid. If the caller ever receives an invalid context, they must discard it and construct a new context. There is no recovery mechanism to repair a bad context. More...

virtual const std::shared_ptr< const Capabilities > &	GetCapabilities () const =0
	Get the capabilities of Impeller context. All optionally supported feature of the platform, client-rendering API, and device can be queried using the `Capabilities`. More...

virtual bool	UpdateOffscreenLayerPixelFormat (PixelFormat format)

virtual std::shared_ptr< Allocator >	GetResourceAllocator () const =0
	Returns the allocator used to create textures and buffers on the device. More...

virtual std::shared_ptr< ShaderLibrary >	GetShaderLibrary () const =0
	Returns the library of shaders used to specify the programmable stages of a pipeline. More...

virtual std::shared_ptr< SamplerLibrary >	GetSamplerLibrary () const =0
	Returns the library of combined image samplers used in shaders. More...

virtual std::shared_ptr< PipelineLibrary >	GetPipelineLibrary () const =0
	Returns the library of pipelines used by render or compute commands. More...

virtual std::shared_ptr< CommandBuffer >	CreateCommandBuffer () const =0
	Create a new command buffer. Command buffers can be used to encode graphics, blit, or compute commands to be submitted to the device. More...

virtual std::shared_ptr< CommandQueue >	GetCommandQueue () const =0
	Return the graphics queue for submitting command buffers. More...

virtual void	Shutdown ()=0
	Force all pending asynchronous work to finish. This is achieved by deleting all owned concurrent message loops. More...

virtual void	StoreTaskForGPU (const fml::closure &task, const fml::closure &failure)

virtual void	InitializeCommonlyUsedShadersIfNeeded () const

virtual void	DisposeThreadLocalCachedResources ()

Static Public Attributes
static constexpr int32_t	kMaxTasksAwaitingGPU = 10

Protected Member Functions
	Context ()

Protected Attributes
std::vector< std::function< void()> >	per_frame_task_

Detailed Description

To do anything rendering related with Impeller, you need a context.

Contexts are expensive to construct and typically you only need one in the process. The context represents a connection to a graphics or compute accelerator on the device.

If there are multiple context in a process, it would typically be for separation of concerns (say, use with multiple engines in Flutter), talking to multiple accelerators, or talking to the same accelerator using different client APIs (Metal, Vulkan, OpenGL ES, etc..).

Contexts are thread-safe. They may be created, used, and collected (though not from a thread used by an internal pool) on any thread. They may also be accessed simultaneously from multiple threads.

Contexts are abstract and a concrete instance must be created using one of the subclasses of Context in //impeller/renderer/backend.

Definition at line 46 of file context.h.

Member Enumeration Documentation

◆ BackendType

enum impeller::Context::BackendType

strong

Enumerator
kMetal
kOpenGLES
kVulkan

Definition at line 48 of file context.h.

                          {
     kMetal,
     kOpenGLES,
     kVulkan,
   };

Constructor & Destructor Documentation

◆ ~Context()

impeller::Context::~Context ( )

virtualdefault

Destroys an Impeller context.

◆ Context()

impeller::Context::Context ( )

protecteddefault

Member Function Documentation

◆ CreateCommandBuffer()

virtual std::shared_ptr<CommandBuffer> impeller::Context::CreateCommandBuffer ( ) const

pure virtual

Create a new command buffer. Command buffers can be used to encode graphics, blit, or compute commands to be submitted to the device.

A command buffer can only be used on a single thread. Multi-threaded render, blit, or compute passes must create a new command buffer on each thread.

Returns: A new command buffer.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

Referenced by impeller::TypographerContextSkia::CreateGlyphAtlas(), impeller::TypographerContextSTB::CreateGlyphAtlas(), and impeller::testing::CreateTestYUVTextures().

◆ DescribeGpuModel()

virtual std::string impeller::Context::DescribeGpuModel ( ) const

pure virtual

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

◆ DisposeThreadLocalCachedResources()

virtual void impeller::Context::DisposeThreadLocalCachedResources ( )

inlinevirtual

Dispose resources that are cached on behalf of the current thread.

Some backends such as Vulkan may cache resources that can be reused while executing a rendering operation. This API can be called after the operation completes in order to clear the cache.

Reimplemented in impeller::ContextVK, and impeller::SurfaceContextVK.

Definition at line 204 of file context.h.

204 {}

◆ GetBackendType()

virtual BackendType impeller::Context::GetBackendType ( ) const

pure virtual

Get the graphics backend of an Impeller context.

        This is useful for cases where a renderer needs to track and
        lookup backend-specific resources, like shaders or uniform
        layout information.

        It's not recommended to use this as a substitute for
        per-backend capability checking. Instead, check for specific
        capabilities via `GetCapabilities()`.

Returns: The graphics backend of the Context.

Implemented in impeller::ContextMTL, impeller::ContextVK, impeller::SurfaceContextVK, and impeller::ContextGLES.

Referenced by impeller::TypographerContextSkia::CreateGlyphAtlas().

◆ GetCapabilities()

virtual const std::shared_ptr<const Capabilities>& impeller::Context::GetCapabilities ( ) const

pure virtual

Get the capabilities of Impeller context. All optionally supported feature of the platform, client-rendering API, and device can be queried using the Capabilities.

Returns: The capabilities. Can never be nullptr for a valid context.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

Referenced by impeller::CreateDefaultPipeline(), impeller::TypographerContextSkia::CreateGlyphAtlas(), impeller::TypographerContextSTB::CreateGlyphAtlas(), impeller::RenderTargetAllocator::CreateOffscreen(), impeller::RenderTargetAllocator::CreateOffscreenMSAA(), impeller::PipelineBuilder< VertexShader_, FragmentShader_ >::InitializePipelineDescriptorDefaults(), and impeller::RenderTarget::SetupDepthStencilAttachments().

◆ GetCommandQueue()

virtual std::shared_ptr<CommandQueue> impeller::Context::GetCommandQueue ( ) const

pure virtual

Return the graphics queue for submitting command buffers.

Implemented in impeller::ContextVK, impeller::ContextMTL, and impeller::SurfaceContextVK.

Referenced by impeller::TypographerContextSkia::CreateGlyphAtlas(), impeller::TypographerContextSTB::CreateGlyphAtlas(), and impeller::testing::CreateTestYUVTextures().

◆ GetPipelineLibrary()

virtual std::shared_ptr<PipelineLibrary> impeller::Context::GetPipelineLibrary ( ) const

pure virtual

Returns the library of pipelines used by render or compute commands.

Returns: The pipeline library. Can never be nullptr for a valid context.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

Referenced by impeller::CreatePipelineFuture().

◆ GetResourceAllocator()

virtual std::shared_ptr<Allocator> impeller::Context::GetResourceAllocator ( ) const

pure virtual

Returns the allocator used to create textures and buffers on the device.

Returns: The resource allocator. Can never be nullptr for a valid context.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

Referenced by impeller::TypographerContextSkia::CreateGlyphAtlas(), impeller::TypographerContextSTB::CreateGlyphAtlas(), and impeller::testing::CreateTestYUVTextures().

◆ GetSamplerLibrary()

virtual std::shared_ptr<SamplerLibrary> impeller::Context::GetSamplerLibrary ( ) const

pure virtual

Returns the library of combined image samplers used in shaders.

Returns: The sampler library. Can never be nullptr for a valid context.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

◆ GetShaderLibrary()

virtual std::shared_ptr<ShaderLibrary> impeller::Context::GetShaderLibrary ( ) const

pure virtual

Returns the library of shaders used to specify the programmable stages of a pipeline.

Returns: The shader library. Can never be nullptr for a valid context.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

Referenced by impeller::ComputePipelineBuilder< ComputeShader_ >::InitializePipelineDescriptorDefaults(), and impeller::PipelineBuilder< VertexShader_, FragmentShader_ >::InitializePipelineDescriptorDefaults().

◆ InitializeCommonlyUsedShadersIfNeeded()

virtual void impeller::Context::InitializeCommonlyUsedShadersIfNeeded ( ) const

inlinevirtual

Run backend specific additional setup and create common shader variants.

This bootstrap is intended to improve the performance of several first frame benchmarks that are tracked in the flutter device lab. The workload includes initializing commonly used but not default shader variants, as well as forcing driver initialization.

Reimplemented in impeller::ContextVK, and impeller::SurfaceContextVK.

Definition at line 197 of file context.h.

197 {}

◆ IsValid()

virtual bool impeller::Context::IsValid ( ) const

pure virtual

Determines if a context is valid. If the caller ever receives an invalid context, they must discard it and construct a new context. There is no recovery mechanism to repair a bad context.

It is convention in Impeller to never return an invalid context from a call that returns an pointer to a context. The call implementation performs validity checks itself and return a null context instead of a pointer to an invalid context.

How a context goes invalid is backend specific. It could happen due to device loss, or any other unrecoverable error.

Returns: If the context is valid.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

Referenced by impeller::CreatePipelineFuture().

◆ Shutdown()

virtual void impeller::Context::Shutdown ( )

pure virtual

Force all pending asynchronous work to finish. This is achieved by deleting all owned concurrent message loops.

Implemented in impeller::ContextMTL, impeller::ContextVK, and impeller::SurfaceContextVK.

◆ StoreTaskForGPU()

virtual void impeller::Context::StoreTaskForGPU	(	const fml::closure &	task,
		const fml::closure &	failure
	)

inlinevirtual

Stores a task on the ContextMTL that is awaiting access for the GPU.

The task will be executed in the event that the GPU access has changed to being available or that the task has been canceled. The task should operate with the SyncSwitch to make sure the GPU is accessible.

If the queue of pending tasks is cleared without GPU access, then the failure callback will be invoked and the primary task function will not

Threadsafe.

task will be executed on the platform thread.

Reimplemented in impeller::ContextMTL.

Definition at line 186 of file context.h.

                                                           {
     FML_CHECK(false && "not supported in this context");
   }

◆ UpdateOffscreenLayerPixelFormat()

bool impeller::Context::UpdateOffscreenLayerPixelFormat ( PixelFormat format )

virtual

Reimplemented in impeller::ContextMTL.

Definition at line 13 of file context.cc.

                                                                 {
   return false;
 }

Member Data Documentation

◆ kMaxTasksAwaitingGPU

constexpr int32_t impeller::Context::kMaxTasksAwaitingGPU = 10

staticconstexpr

The maximum number of tasks that should ever be stored for StoreTaskForGPU.

This number was arbitrarily chosen. The idea is that this is a somewhat rare situation where tasks happen to get executed in that tiny amount of time while an app is being backgrounded but still executing.

Definition at line 60 of file context.h.

◆ per_frame_task_

std::vector<std::function<void()> > impeller::Context::per_frame_task_

protected

Definition at line 209 of file context.h.

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

impeller/renderer/context.h
impeller/renderer/context.cc

Public Types

Public Member Functions

Static Public Attributes

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ BackendType

Constructor & Destructor Documentation

◆ ~Context()

◆ Context()

Member Function Documentation

◆ CreateCommandBuffer()

◆ DescribeGpuModel()

◆ DisposeThreadLocalCachedResources()

◆ GetBackendType()

◆ GetCapabilities()

◆ GetCommandQueue()

◆ GetPipelineLibrary()

◆ GetResourceAllocator()

◆ GetSamplerLibrary()

◆ GetShaderLibrary()

◆ InitializeCommonlyUsedShadersIfNeeded()

◆ IsValid()

◆ Shutdown()

◆ StoreTaskForGPU()

◆ UpdateOffscreenLayerPixelFormat()

Member Data Documentation

◆ kMaxTasksAwaitingGPU

◆ per_frame_task_