flutter::PlatformView Class Reference

Platform views are created by the shell on the platform task runner. Unless explicitly specified, all platform view methods are called on the platform task runner as well. Platform views are usually sub-classed on a per platform basis and the bulk of the window system integration happens using that subclass. Since most platform window toolkits are usually only safe to access on a single "main" thread, any interaction that requires access to the underlying platform's window toolkit is routed through the platform view associated with that shell. This involves operations like settings up and tearing down the render surface, platform messages, interacting with accessibility features on the platform, input events, etc. More...

#include <platform_view.h>

Inheritance diagram for flutter::PlatformView:

Classes
class	Delegate
	Used to forward events from the platform view to interested subsystems. This forwarding is done by the shell which sets itself up as the delegate of the platform view. More...

Public Types
using	AddViewCallback = std::function< void(bool added)>
using	RemoveViewCallback = std::function< void(bool removed)>

Public Member Functions
	PlatformView (Delegate &delegate, const TaskRunners &task_runners)
	Creates a platform view with the specified delegate and task runner. The base class by itself does not do much but is suitable for use in test environments where full platform integration may not be necessary. The platform view may only be created, accessed and destroyed on the platform task runner.
virtual	~PlatformView ()
	Destroys the platform view. The platform view is owned by the shell and will be destroyed by the same on the platform tasks runner.
virtual std::unique_ptr< VsyncWaiter >	CreateVSyncWaiter ()
	Invoked by the shell to obtain a platform specific vsync waiter. It is optional for platforms to override this method and provide a custom vsync waiter because a timer based fall-back waiter is used by default. However, it is highly recommended that platform provide their own Vsync waiter as the timer based fall-back will not render frames aligned with vsync boundaries.
void	DispatchPlatformMessage (std::unique_ptr< PlatformMessage > message)
	Used by embedders to dispatch a platform message to a running root isolate hosted by the engine. If an isolate is not running, the message is dropped. If there is no one on the other side listening on the channel, the message is dropped. When a platform message is dropped, any response handles associated with that message will be dropped as well. All users of platform messages must assume that message may not be delivered and/or their response handles may not be invoked. Platform messages are not buffered.
virtual void	HandlePlatformMessage (std::unique_ptr< PlatformMessage > message)
	Overridden by embedders to perform actions in response to platform messages sent from the framework to the embedder. Default implementation of this method simply returns an empty response.
void	DispatchSemanticsAction (int32_t node_id, SemanticsAction action, fml::MallocMapping args)
	Used by embedders to dispatch an accessibility action to a running isolate hosted by the engine.
virtual void	SetSemanticsEnabled (bool enabled)
	Used by embedder to notify the running isolate hosted by the engine on the UI thread that the accessibility tree needs to be generated.
virtual void	SetAccessibilityFeatures (int32_t flags)
	Used by the embedder to specify the features to enable in the accessibility tree generated by the isolate. This information is forwarded to the root isolate hosted by the engine on the UI thread.
virtual void	UpdateSemantics (SemanticsNodeUpdates updates, CustomAccessibilityActionUpdates actions)
	Used by the framework to tell the embedder to apply the specified semantics node updates. The default implementation of this method does nothing.
virtual void	SendChannelUpdate (const std::string &name, bool listening)
	Used by the framework to tell the embedder that it has registered a listener on a given channel.
void	SetViewportMetrics (int64_t view_id, const ViewportMetrics &metrics)
	Used by embedders to specify the updated viewport metrics for a view. In response to this call, on the raster thread, the rasterizer may need to be reconfigured to the updated viewport dimensions. On the UI thread, the framework may need to start generating a new frame for the updated viewport metrics as well.
void	NotifyCreated ()
	Used by embedders to notify the shell that a platform view has been created. This notification is used to create a rendering surface and pick the client rendering API to use to render into this surface. No frames will be scheduled or rendered before this call. The surface must remain valid till the corresponding call to NotifyDestroyed.
virtual void	NotifyDestroyed ()
	Used by embedders to notify the shell that the platform view has been destroyed. This notification used to collect the rendering surface and all associated resources. Frame scheduling is also suspended.
void	ScheduleFrame ()
	Used by embedders to schedule a frame. In response to this call, the framework may need to start generating a new frame.
void	AddView (int64_t view_id, const ViewportMetrics &viewport_metrics, AddViewCallback callback)
	Used by embedders to notify the shell of a new non-implicit view.
void	RemoveView (int64_t view_id, RemoveViewCallback callback)
	Used by embedders to notify the shell of a removed non-implicit view.
virtual sk_sp< GrDirectContext >	CreateResourceContext () const
	Used by the shell to obtain a Skia GPU context that is capable of operating on the IO thread. The context must be in the same share-group as the Skia GPU context used on the render thread. This context will always be used on the IO thread. Because it is in the same share-group as the separate render thread context, any GPU resources uploaded in this context will be visible to the render thread context (synchronization of GPU resources is managed by Skia).
virtual std::shared_ptr< impeller::Context >	GetImpellerContext () const
virtual void	ReleaseResourceContext () const
	Used by the shell to notify the embedder that the resource context previously obtained via a call to CreateResourceContext() is being collected. The embedder is free to collect an platform specific resources associated with this context.
virtual PointerDataDispatcherMaker	GetDispatcherMaker ()
	Returns a platform-specific PointerDataDispatcherMaker so the Engine can construct the PointerDataPacketDispatcher based on platforms.
fml::WeakPtr< PlatformView >	GetWeakPtr () const
	Returns a weak pointer to the platform view. Since the platform view may only be created, accessed and destroyed on the platform thread, any access to the platform view from a non-platform task runner needs a weak pointer to the platform view along with a reference to the platform task runner. A task must be posted to the platform task runner with the weak pointer captured in the same. The platform view method may only be called in the posted task once the weak pointer validity has been checked. This method is used by callers to obtain that weak pointer.
virtual void	OnPreEngineRestart () const
	Gives embedders a chance to react to a "cold restart" of the running isolate. The default implementation of this method does nothing.
void	SetNextFrameCallback (const fml::closure &closure)
	Sets a callback that gets executed when the rasterizer renders the next frame. Due to the asynchronous nature of rendering in Flutter, embedders usually add a placeholder over the contents in which Flutter is going to render when Flutter is first initialized. This callback may be used as a signal to remove that placeholder. The callback is executed on the render task runner and not the platform task runner. It is the embedder's responsibility to re-thread as necessary.
void	DispatchPointerDataPacket (std::unique_ptr< PointerDataPacket > packet)
	Dispatches pointer events from the embedder to the framework. Each pointer data packet may contain multiple pointer input events. Each call to this method wakes up the UI thread.
void	RegisterTexture (std::shared_ptr< flutter::Texture > texture)
	Used by the embedder to specify a texture that it wants the rasterizer to composite within the Flutter layer tree. All textures must have a unique identifier. When the rasterizer encounters an external texture within its hierarchy, it gives the embedder a chance to update that texture on the raster thread before it composites the same on-screen.
void	UnregisterTexture (int64_t texture_id)
	Used by the embedder to notify the rasterizer that it will no longer attempt to composite the specified texture within the layer tree. This allows the rasterizer to collect associated resources.
void	MarkTextureFrameAvailable (int64_t texture_id)
	Used by the embedder to notify the rasterizer that the context of the previously registered texture have been updated. Typically, Flutter will only render a frame if there is an updated layer tree. However, in cases where the layer tree is static but one of the externally composited textures has been updated by the embedder, the embedder needs to notify the rasterizer to render a new frame. In such cases, the existing layer tree may be reused with the frame re-composited with all updated external textures. Unlike the calls to register and unregister the texture, this call must be made each time a new texture frame is available.
virtual std::unique_ptr< std::vector< std::string > >	ComputePlatformResolvedLocales (const std::vector< std::string > &supported_locale_data)
	Directly invokes platform-specific APIs to compute the locale the platform would have natively resolved to.
virtual std::shared_ptr< ExternalViewEmbedder >	CreateExternalViewEmbedder ()
virtual void	RequestDartDeferredLibrary (intptr_t loading_unit_id)
	Invoked when the dart VM requests that a deferred library be loaded. Notifies the engine that the deferred library identified by the specified loading unit id should be downloaded and loaded into the Dart VM via LoadDartDeferredLibrary
virtual void	LoadDartDeferredLibrary (intptr_t loading_unit_id, std::unique_ptr< const fml::Mapping > snapshot_data, std::unique_ptr< const fml::Mapping > snapshot_instructions)
	Loads the Dart shared library into the Dart VM. When the Dart library is loaded successfully, the Dart future returned by the originating loadLibrary() call completes.
virtual void	LoadDartDeferredLibraryError (intptr_t loading_unit_id, const std::string error_message, bool transient)
	Indicates to the dart VM that the request to load a deferred library with the specified loading unit id has failed.
virtual void	UpdateAssetResolverByType (std::unique_ptr< AssetResolver > updated_asset_resolver, AssetResolver::AssetResolverType type)
	Replaces the asset resolver handled by the engine's AssetManager of the specified type with updated_asset_resolver. The matching AssetResolver is removed and replaced with updated_asset_resolvers.
virtual std::unique_ptr< SnapshotSurfaceProducer >	CreateSnapshotSurfaceProducer ()
	Creates an object that produces surfaces suitable for raster snapshotting. The rasterizer will request this surface if no on screen surface is currently available when an application requests a snapshot, e.g. if Scene.toImage or Picture.toImage are called while the application is in the background.
virtual std::shared_ptr< PlatformMessageHandler >	GetPlatformMessageHandler () const
	Specifies a delegate that will receive PlatformMessages from Flutter to the host platform.
const Settings &	GetSettings () const
	Get the settings for this platform view instance.
virtual double	GetScaledFontSize (double unscaled_font_size, int configuration_id) const
	Synchronously invokes platform-specific APIs to apply the system text scaling on the given unscaled font size.

Protected Member Functions
virtual std::unique_ptr< Surface >	CreateRenderingSurface ()

Protected Attributes
PlatformView::Delegate &	delegate_
const TaskRunners	task_runners_
PointerDataPacketConverter	pointer_data_packet_converter_
fml::WeakPtrFactory< PlatformView >	weak_factory_

Detailed Description

Platform views are created by the shell on the platform task runner. Unless explicitly specified, all platform view methods are called on the platform task runner as well. Platform views are usually sub-classed on a per platform basis and the bulk of the window system integration happens using that subclass. Since most platform window toolkits are usually only safe to access on a single "main" thread, any interaction that requires access to the underlying platform's window toolkit is routed through the platform view associated with that shell. This involves operations like settings up and tearing down the render surface, platform messages, interacting with accessibility features on the platform, input events, etc.

Definition at line 52 of file platform_view.h.

Member Typedef Documentation

AddViewCallback

using flutter::PlatformView::AddViewCallback = std::function<void(bool added)>

Definition at line 54 of file platform_view.h.

RemoveViewCallback

using flutter::PlatformView::RemoveViewCallback = std::function<void(bool removed)>

Definition at line 55 of file platform_view.h.

Constructor & Destructor Documentation

PlatformView()

PlatformView::PlatformView ( Delegate &  delegate, const TaskRunners &  task_runners  )

explicit

Creates a platform view with the specified delegate and task runner. The base class by itself does not do much but is suitable for use in test environments where full platform integration may not be necessary. The platform view may only be created, accessed and destroyed on the platform task runner.

Parameters

	delegate	The delegate. This is typically the shell.
[in]	task_runners	The task runners used by this platform view.

Definition at line 16 of file platform_view.cc.

    : delegate_(delegate), task_runners_(task_runners), weak_factory_(this) {}

~PlatformView()

PlatformView::~PlatformView ( )

virtualdefault

Destroys the platform view. The platform view is owned by the shell and will be destroyed by the same on the platform tasks runner.

Reimplemented in flutter_runner::PlatformView.

Member Function Documentation

AddView()

void PlatformView::AddView	(	int64_t	view_id,
		const ViewportMetrics &	viewport_metrics,
		AddViewCallback	callback
	)

Used by embedders to notify the shell of a new non-implicit view.

    This method notifies the shell to allocate resources and inform
    Dart about the view, and on success, schedules a new frame.
    Finally, it invokes |callback| with whether the operation is
    successful.

    This operation is asynchronous; avoid using the view until
    |callback| returns true. Callers should prepare resources for the
    view (if any) in advance but be ready to clean up on failure.

    The callback is called on a different thread.

    Do not use for implicit views, which are added internally during
    shell initialization. Adding |kFlutterImplicitViewId| or an
    existing view ID will fail, indicated by |callback| returning
    false.

Parameters

[in]	view_id	The view ID of the new view.
[in]	viewport_metrics	The initial viewport metrics for the view.
[in]	callback	The callback that's invoked once the shell has attempted to add the view.

Definition at line 90 of file platform_view.cc.

                                                     {
  delegate_.OnPlatformViewAddView(view_id, viewport_metrics,
                                  std::move(callback));
}

ComputePlatformResolvedLocales()

std::unique_ptr< std::vector< std::string > > PlatformView::ComputePlatformResolvedLocales ( const std::vector< std::string > &  supported_locale_data )

virtual

Directly invokes platform-specific APIs to compute the locale the platform would have natively resolved to.

Parameters

[in]

supported_locale_data

The vector of strings that represents the locales supported by the app. Each locale consists of three strings: languageCode, countryCode, and scriptCode in that order.

Returns

A vector of 3 strings languageCode, countryCode, and scriptCode that represents the locale selected by the platform. Empty strings mean the value was unassigned. Empty vector represents a null locale.

Reimplemented in flutter::PlatformViewAndroid, flutter::PlatformViewIOS, and flutter::PlatformViewEmbedder.

Definition at line 175 of file platform_view.cc.

                                                       {
  std::unique_ptr<std::vector<std::string>> out =
      std::make_unique<std::vector<std::string>>();
  return out;
}

CreateExternalViewEmbedder()

std::shared_ptr< ExternalViewEmbedder > PlatformView::CreateExternalViewEmbedder ( )

virtual

Reimplemented in flutter::testing::ShellTestPlatformViewGL, flutter::testing::ShellTestPlatformViewMetal, flutter::testing::ShellTestPlatformViewVulkan, flutter::PlatformViewAndroid, flutter::PlatformViewIOS, flutter::PlatformViewEmbedder, flutter_runner::PlatformView, and flutter::TesterPlatformView.

Definition at line 160 of file platform_view.cc.

                                         {
  FML_DLOG(WARNING)
      << "This platform doesn't support embedding external views.";
  return nullptr;
}

CreateRenderingSurface()

std::unique_ptr< Surface > PlatformView::CreateRenderingSurface ( )

protectedvirtual

Reimplemented in flutter::testing::ShellTestPlatformViewGL, flutter::testing::ShellTestPlatformViewMetal, flutter::testing::ShellTestPlatformViewVulkan, flutter::PlatformViewAndroid, flutter::PlatformViewIOS, flutter::PlatformViewEmbedder, flutter_runner::PlatformView, and flutter::TesterPlatformView.

Definition at line 151 of file platform_view.cc.

                                                            {
  // We have a default implementation because tests create a platform view but
  // never a rendering surface.
  FML_DCHECK(false) << "This platform does not provide a rendering surface but "
                       "it was notified of surface rendering surface creation.";
  return nullptr;
}

CreateResourceContext()

sk_sp< GrDirectContext > PlatformView::CreateResourceContext ( ) const

virtual

Used by the shell to obtain a Skia GPU context that is capable of operating on the IO thread. The context must be in the same share-group as the Skia GPU context used on the render thread. This context will always be used on the IO thread. Because it is in the same share-group as the separate render thread context, any GPU resources uploaded in this context will be visible to the render thread context (synchronization of GPU resources is managed by Skia).

If such context cannot be created on the IO thread, callers may return nullptr. This will mean that all texture uploads will be queued onto the render thread which will cause performance issues. When this context is nullptr, an error is logged to the console. It is highly recommended that all platforms provide a resource context.

Attention

Unlike all other methods on the platform view, this will be called on IO task runner.

Returns

The Skia GPU context that is in the same share-group as the main render thread GPU context. May be nullptr in case such a context cannot be created.

Reimplemented in flutter::PlatformViewAndroid, flutter::PlatformViewIOS, and flutter::PlatformViewEmbedder.

Definition at line 101 of file platform_view.cc.

                                                                 {
  FML_DLOG(WARNING) << "This platform does not set up the resource "
                       "context on the IO thread for async texture uploads.";
  return nullptr;
}

CreateSnapshotSurfaceProducer()

std::unique_ptr< SnapshotSurfaceProducer > PlatformView::CreateSnapshotSurfaceProducer ( )

virtual

Creates an object that produces surfaces suitable for raster snapshotting. The rasterizer will request this surface if no on screen surface is currently available when an application requests a snapshot, e.g. if Scene.toImage or Picture.toImage are called while the application is in the background.

Not all backends support this kind of surface usage, and the default implementation returns nullptr. Platforms should override this if they can support GPU operations in the background and support GPU resource context usage.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 202 of file platform_view.cc.

                                            {
  return nullptr;
}

CreateVSyncWaiter()

std::unique_ptr< VsyncWaiter > PlatformView::CreateVSyncWaiter ( )

virtual

Invoked by the shell to obtain a platform specific vsync waiter. It is optional for platforms to override this method and provide a custom vsync waiter because a timer based fall-back waiter is used by default. However, it is highly recommended that platform provide their own Vsync waiter as the timer based fall-back will not render frames aligned with vsync boundaries.

Attention

If a timer based fall-back is used, a warning is logged to the console. In case this method is overridden in a subclass, it must return a valid vsync waiter. Returning null will lead to internal errors. If a valid vsync waiter cannot be returned, subclasses should just call the based class method instead.

Returns

A vsync waiter. If is an internal error to return a null waiter.

Reimplemented in flutter::testing::ShellTestPlatformViewGL, flutter::testing::ShellTestPlatformViewMetal, flutter::testing::ShellTestPlatformViewVulkan, flutter::PlatformViewAndroid, flutter::PlatformViewIOS, flutter::PlatformViewEmbedder, and flutter_runner::PlatformView.

Definition at line 21 of file platform_view.cc.

                                                           {
  FML_DLOG(WARNING)
      << "This platform does not provide a Vsync waiter implementation. A "
         "simple timer based fallback is being used.";
  return std::make_unique<VsyncWaiterFallback>(task_runners_);
}

DispatchPlatformMessage()

void PlatformView::DispatchPlatformMessage

(

std::unique_ptr< PlatformMessage >

message

)

Used by embedders to dispatch a platform message to a running root isolate hosted by the engine. If an isolate is not running, the message is dropped. If there is no one on the other side listening on the channel, the message is dropped. When a platform message is dropped, any response handles associated with that message will be dropped as well. All users of platform messages must assume that message may not be delivered and/or their response handles may not be invoked. Platform messages are not buffered.

For embedders that wish to respond to platform message directed from the framework to the embedder, the HandlePlatformMessage method may be overridden.

See also

HandlePlatformMessage()

Parameters

[in]

message

The platform message to deliver to the root isolate.

Definition at line 28 of file platform_view.cc.

                                            {
  delegate_.OnPlatformViewDispatchPlatformMessage(std::move(message));
}

DispatchPointerDataPacket()

void PlatformView::DispatchPointerDataPacket

(

std::unique_ptr< PointerDataPacket >

packet

)

Dispatches pointer events from the embedder to the framework. Each pointer data packet may contain multiple pointer input events. Each call to this method wakes up the UI thread.

Parameters

[in]

packet

The pointer data packet to dispatch to the framework.

Definition at line 33 of file platform_view.cc.

                                             {
  delegate_.OnPlatformViewDispatchPointerDataPacket(
      pointer_data_packet_converter_.Convert(std::move(packet)));
}

DispatchSemanticsAction()

void PlatformView::DispatchSemanticsAction	(	int32_t	node_id,
		SemanticsAction	action,
		fml::MallocMapping	args
	)

Used by embedders to dispatch an accessibility action to a running isolate hosted by the engine.

Parameters

[in]	node_id	The identifier of the accessibility node on which to perform the action.
[in]	action	The action
[in]	args	The arguments

Definition at line 39 of file platform_view.cc.

                                                                  {
  delegate_.OnPlatformViewDispatchSemanticsAction(node_id, action,
                                                  std::move(args));
}

GetDispatcherMaker()

PointerDataDispatcherMaker PlatformView::GetDispatcherMaker ( )

virtual

Returns a platform-specific PointerDataDispatcherMaker so the Engine can construct the PointerDataPacketDispatcher based on platforms.

Reimplemented in flutter::testing::ShellTestPlatformViewGL, flutter::testing::ShellTestPlatformViewMetal, flutter::testing::ShellTestPlatformViewVulkan, and flutter::PlatformViewIOS.

Definition at line 113 of file platform_view.cc.

                                                            {
  return [](DefaultPointerDataDispatcher::Delegate& delegate) {
    return std::make_unique<DefaultPointerDataDispatcher>(delegate);
  };
}

GetImpellerContext()

std::shared_ptr< impeller::Context > PlatformView::GetImpellerContext ( ) const

virtual

Reimplemented in flutter::testing::ShellTestPlatformViewGL, flutter::testing::ShellTestPlatformViewMetal, flutter::PlatformViewAndroid, flutter::PlatformViewIOS, flutter::PlatformViewEmbedder, and flutter::TesterPlatformView.

Definition at line 107 of file platform_view.cc.

                                                                      {
  return nullptr;
}

GetPlatformMessageHandler()

std::shared_ptr< PlatformMessageHandler > PlatformView::GetPlatformMessageHandler ( ) const

virtual

Specifies a delegate that will receive PlatformMessages from Flutter to the host platform.

If this returns null that means PlatformMessages should be sent to the PlatformView. That is to protect legacy behavior, any embedder that wants to support executing Platform Channel handlers on background threads should be returning a thread-safe PlatformMessageHandler instead.

Reimplemented in flutter::PlatformViewAndroid, flutter::PlatformViewIOS, and flutter::PlatformViewEmbedder.

Definition at line 207 of file platform_view.cc.

                                              {
  return nullptr;
}

GetScaledFontSize()

double PlatformView::GetScaledFontSize ( double  unscaled_font_size, int  configuration_id  ) const

virtual

Synchronously invokes platform-specific APIs to apply the system text scaling on the given unscaled font size.

Platforms that support this feature (currently it's only implemented for Android SDK level 34+) will send a valid configuration_id to potential callers, before this method can be called.

Parameters

[in]	unscaled_font_size	The unscaled font size specified by the app developer. The value is in logical pixels, and is guaranteed to be finite and non-negative.
[in]	configuration_id	The unique id of the configuration to use for computing the scaled font size.

Returns

The scaled font size in logical pixels, or -1 if the given configuration_id did not match a valid configuration.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 215 of file platform_view.cc.

                                                                   {
  // Unreachable by default, as most platforms do not support nonlinear scaling
  // and the Flutter application never invokes this method.
  FML_UNREACHABLE();
  return -1;
}

GetSettings()

const Settings & PlatformView::GetSettings

(

)

const

Get the settings for this platform view instance.

Returns

The settings.

Definition at line 211 of file platform_view.cc.

                                                {
  return delegate_.OnPlatformViewGetSettings();
}

GetWeakPtr()

fml::WeakPtr< PlatformView > PlatformView::GetWeakPtr

(

)

const

Returns a weak pointer to the platform view. Since the platform view may only be created, accessed and destroyed on the platform thread, any access to the platform view from a non-platform task runner needs a weak pointer to the platform view along with a reference to the platform task runner. A task must be posted to the platform task runner with the weak pointer captured in the same. The platform view method may only be called in the posted task once the weak pointer validity has been checked. This method is used by callers to obtain that weak pointer.

Returns

The weak pointer to the platform view.

Definition at line 119 of file platform_view.cc.

                                                        {
  return weak_factory_.GetWeakPtr();
}

HandlePlatformMessage()

void PlatformView::HandlePlatformMessage ( std::unique_ptr< PlatformMessage >  message )

virtual

Overridden by embedders to perform actions in response to platform messages sent from the framework to the embedder. Default implementation of this method simply returns an empty response.

Embedders that wish to send platform messages to the framework may use the DispatchPlatformMessage method. This method is for messages that go the other way.

See also

DispatchPlatformMessage()

Parameters

[in]

message

The message

Reimplemented in flutter::PlatformViewAndroid, flutter::PlatformViewIOS, flutter_runner::PlatformView, and flutter::PlatformViewEmbedder.

Definition at line 130 of file platform_view.cc.

                                            {
  if (auto response = message->response()) {
    response->CompleteEmpty();
  }
}

LoadDartDeferredLibrary()

void PlatformView::LoadDartDeferredLibrary ( intptr_t  loading_unit_id, std::unique_ptr< const fml::Mapping >  snapshot_data, std::unique_ptr< const fml::Mapping >  snapshot_instructions  )

virtual

Loads the Dart shared library into the Dart VM. When the Dart library is loaded successfully, the Dart future returned by the originating loadLibrary() call completes.

The Dart compiler may generate separate shared libraries files called 'loading units' when libraries are imported as deferred. Each of these shared libraries are identified by a unique loading unit id. Callers should open and resolve a SymbolMapping from the shared library. The Mappings should be moved into this method, as ownership will be assumed by the dart isolate after successful loading and released after shutdown of the dart isolate. If loading fails, the mappings will naturally go out of scope.

This method is paired with a RequestDartDeferredLibrary invocation that provides the embedder with the loading unit id of the deferred library to load.

Parameters

[in]	loading_unit_id	The unique id of the deferred library's loading unit, as passed in by RequestDartDeferredLibrary.
[in]	snapshot_data	Dart snapshot data of the loading unit's shared library.
[in]	snapshot_data	Dart snapshot instructions of the loading unit's shared library.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 184 of file platform_view.cc.

                                                           {}

LoadDartDeferredLibraryError()

void PlatformView::LoadDartDeferredLibraryError ( intptr_t  loading_unit_id, const std::string  error_message, bool  transient  )

virtual

Indicates to the dart VM that the request to load a deferred library with the specified loading unit id has failed.

The dart future returned by the initiating loadLibrary() call will complete with an error.

Parameters

[in]	loading_unit_id	The unique id of the deferred library's loading unit, as passed in by RequestDartDeferredLibrary.
[in]	error_message	The error message that will appear in the dart Future.
[in]	transient	A transient error is a failure due to temporary conditions such as no network. Transient errors allow the dart VM to re-request the same deferred library and loading_unit_id again. Non-transient errors are permanent and attempts to re-request the library will instantly complete with an error.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 189 of file platform_view.cc.

                    {}

MarkTextureFrameAvailable()

void PlatformView::MarkTextureFrameAvailable

(

int64_t

texture_id

)

Used by the embedder to notify the rasterizer that the context of the previously registered texture have been updated. Typically, Flutter will only render a frame if there is an updated layer tree. However, in cases where the layer tree is static but one of the externally composited textures has been updated by the embedder, the embedder needs to notify the rasterizer to render a new frame. In such cases, the existing layer tree may be reused with the frame re-composited with all updated external textures. Unlike the calls to register and unregister the texture, this call must be made each time a new texture frame is available.

See also

RegisterTexture, UnregisterTexture

Parameters

[in]

texture_id

The identifier of the texture that has been updated.

Definition at line 147 of file platform_view.cc.

                                                               {
  delegate_.OnPlatformViewMarkTextureFrameAvailable(texture_id);
}

NotifyCreated()

void PlatformView::NotifyCreated

(

)

Used by embedders to notify the shell that a platform view has been created. This notification is used to create a rendering surface and pick the client rendering API to use to render into this surface. No frames will be scheduled or rendered before this call. The surface must remain valid till the corresponding call to NotifyDestroyed.

Definition at line 59 of file platform_view.cc.

                                 {
  std::unique_ptr<Surface> surface;
  // Threading: We want to use the platform view on the non-platform thread.
  // Using the weak pointer is illegal. But, we are going to introduce a latch
  // so that the platform view is not collected till the surface is obtained.
  auto* platform_view = this;
  fml::ManualResetWaitableEvent latch;
  fml::TaskRunner::RunNowOrPostTask(
      task_runners_.GetRasterTaskRunner(), [platform_view, &surface, &latch]() {
        surface = platform_view->CreateRenderingSurface();
        if (surface && !surface->IsValid()) {
          surface.reset();
        }
        latch.Signal();
      });
  latch.Wait();
  if (!surface) {
    FML_LOG(ERROR) << "Failed to create platform view rendering surface";
    return;
  }
  delegate_.OnPlatformViewCreated(std::move(surface));
}

NotifyDestroyed()

void PlatformView::NotifyDestroyed ( )

virtual

Used by embedders to notify the shell that the platform view has been destroyed. This notification used to collect the rendering surface and all associated resources. Frame scheduling is also suspended.

Attention

Subclasses may choose to override this method to perform platform specific functions. However, they must call the base class method at some point in their implementation.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 82 of file platform_view.cc.

                                   {
  delegate_.OnPlatformViewDestroyed();
}

OnPreEngineRestart()

void PlatformView::OnPreEngineRestart ( ) const

virtual

Gives embedders a chance to react to a "cold restart" of the running isolate. The default implementation of this method does nothing.

While a "hot restart" patches a running isolate, a "cold restart" restarts the root isolate in a running shell.

Reimplemented in flutter::PlatformViewAndroid, flutter::PlatformViewIOS, and flutter::PlatformViewEmbedder.

Definition at line 137 of file platform_view.cc.

{}

RegisterTexture()

void PlatformView::RegisterTexture

(

std::shared_ptr< flutter::Texture >

texture

)

Used by the embedder to specify a texture that it wants the rasterizer to composite within the Flutter layer tree. All textures must have a unique identifier. When the rasterizer encounters an external texture within its hierarchy, it gives the embedder a chance to update that texture on the raster thread before it composites the same on-screen.

Attention

This method must only be called once per texture. When the texture is updated, calling MarkTextureFrameAvailable with the specified texture identifier is sufficient to make Flutter re-render the frame with the updated texture composited in-line.

See also

UnregisterTexture, MarkTextureFrameAvailable

Parameters

[in]

texture

The texture that is being updated by the embedder but composited by Flutter in its own hierarchy.

Definition at line 139 of file platform_view.cc.

                                                                        {
  delegate_.OnPlatformViewRegisterTexture(std::move(texture));
}

ReleaseResourceContext()

void PlatformView::ReleaseResourceContext ( ) const

virtual

Used by the shell to notify the embedder that the resource context previously obtained via a call to CreateResourceContext() is being collected. The embedder is free to collect an platform specific resources associated with this context.

Attention

Unlike all other methods on the platform view, this will be called on IO task runner.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 111 of file platform_view.cc.

{}

RemoveView()

void PlatformView::RemoveView	(	int64_t	view_id,
		RemoveViewCallback	callback
	)

Used by embedders to notify the shell of a removed non-implicit view.

This method notifies the shell to deallocate resources and inform Dart about the removal. Finally, it invokes |callback| with whether the operation is successful.

This operation is asynchronous. The embedder should not deallocate resources until the |callback| is invoked.

The callback is called on a different thread.

Do not use for implicit views, which are never removed throughout the lifetime of the app. Removing |kFlutterImplicitViewId| or an non-existent view ID will fail, indicated by |callback| returning false.

Parameters

[in]	view_id	The view ID of the view to be removed.
[in]	callback	The callback that's invoked once the shell has attempted to remove the view.

Definition at line 97 of file platform_view.cc.

                                                                          {
  delegate_.OnPlatformViewRemoveView(view_id, std::move(callback));
}

RequestDartDeferredLibrary()

void PlatformView::RequestDartDeferredLibrary ( intptr_t  loading_unit_id )

virtual

Invoked when the dart VM requests that a deferred library be loaded. Notifies the engine that the deferred library identified by the specified loading unit id should be downloaded and loaded into the Dart VM via LoadDartDeferredLibrary

Upon encountering errors or otherwise failing to load a loading unit with the specified id, the failure should be directly reported to dart by calling LoadDartDeferredLibraryFailure to ensure the waiting dart future completes with an error.

Parameters

[in]

loading_unit_id

The unique id of the deferred library's loading unit. This id is to be passed back into LoadDartDeferredLibrary in order to identify which deferred library to load.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 182 of file platform_view.cc.

{}

ScheduleFrame()

void PlatformView::ScheduleFrame

(

)

Used by embedders to schedule a frame. In response to this call, the framework may need to start generating a new frame.

Definition at line 86 of file platform_view.cc.

                                 {
  delegate_.OnPlatformViewScheduleFrame();
}

SendChannelUpdate()

void PlatformView::SendChannelUpdate ( const std::string &  name, bool  listening  )

virtual

Used by the framework to tell the embedder that it has registered a listener on a given channel.

Parameters

[in]	name	The name of the channel on which the listener has set or cleared a listener.
[in]	listening	True if a listener has been set, false if it has been cleared.

Reimplemented in flutter::PlatformViewEmbedder.

Definition at line 128 of file platform_view.cc.

{}

SetAccessibilityFeatures()

void PlatformView::SetAccessibilityFeatures ( int32_t  flags )

virtual

Used by the embedder to specify the features to enable in the accessibility tree generated by the isolate. This information is forwarded to the root isolate hosted by the engine on the UI thread.

The engine does not care about the accessibility feature flags as all it does is forward this information from the embedder to the framework. However, curious readers may refer to AccessibilityFeatures in window.dart for currently supported accessibility feature flags.

Attention

Subclasses may choose to override this method to perform platform specific functions. However, they must call the base class method at some point in their implementation.

Parameters

[in]

flags

The features to enable in the accessibility tree.

Reimplemented in flutter::PlatformViewIOS.

Definition at line 50 of file platform_view.cc.

                                                         {
  delegate_.OnPlatformViewSetAccessibilityFeatures(flags);
}

SetNextFrameCallback()

void PlatformView::SetNextFrameCallback

(

const fml::closure &

closure

)

Sets a callback that gets executed when the rasterizer renders the next frame. Due to the asynchronous nature of rendering in Flutter, embedders usually add a placeholder over the contents in which Flutter is going to render when Flutter is first initialized. This callback may be used as a signal to remove that placeholder. The callback is executed on the render task runner and not the platform task runner. It is the embedder's responsibility to re-thread as necessary.

Attention

The callback is executed on the render task runner and not the platform task runner. Embedders must re-thread as necessary.

Parameters

[in]

closure

The callback to execute on the render thread when the next frame gets rendered.

Definition at line 166 of file platform_view.cc.

                                                                 {
  if (!closure) {
    return;
  }
 
  delegate_.OnPlatformViewSetNextFrameCallback(closure);
}

SetSemanticsEnabled()

void PlatformView::SetSemanticsEnabled ( bool  enabled )

virtual

Used by embedder to notify the running isolate hosted by the engine on the UI thread that the accessibility tree needs to be generated.

Attention

Subclasses may choose to override this method to perform platform specific functions. However, they must call the base class method at some point in their implementation.

Parameters

[in]

enabled

Whether the accessibility tree needs to be generated.

Reimplemented in flutter::PlatformViewIOS, and flutter_runner::PlatformView.

Definition at line 46 of file platform_view.cc.

                                                   {
  delegate_.OnPlatformViewSetSemanticsEnabled(enabled);
}

SetViewportMetrics()

void PlatformView::SetViewportMetrics	(	int64_t	view_id,
		const ViewportMetrics &	metrics
	)

Used by embedders to specify the updated viewport metrics for a view. In response to this call, on the raster thread, the rasterizer may need to be reconfigured to the updated viewport dimensions. On the UI thread, the framework may need to start generating a new frame for the updated viewport metrics as well.

Parameters

[in]	view_id	The ID for the view that metrics describes.
[in]	metrics	The updated viewport metrics.

Definition at line 54 of file platform_view.cc.

                                                                      {
  delegate_.OnPlatformViewSetViewportMetrics(view_id, metrics);
}

UnregisterTexture()

void PlatformView::UnregisterTexture

(

int64_t

texture_id

)

Used by the embedder to notify the rasterizer that it will no longer attempt to composite the specified texture within the layer tree. This allows the rasterizer to collect associated resources.

Attention

This call must only be called once per texture identifier.

See also

RegisterTexture, MarkTextureFrameAvailable

Parameters

[in]

texture_id

The identifier of the texture to unregister. If the texture has not been previously registered, this call does nothing.

Definition at line 143 of file platform_view.cc.

                                                       {
  delegate_.OnPlatformViewUnregisterTexture(texture_id);
}

UpdateAssetResolverByType()

void PlatformView::UpdateAssetResolverByType ( std::unique_ptr< AssetResolver >  updated_asset_resolver, AssetResolver::AssetResolverType  type  )

virtual

Replaces the asset resolver handled by the engine's AssetManager of the specified type with updated_asset_resolver. The matching AssetResolver is removed and replaced with updated_asset_resolvers.

AssetResolvers should be updated when the existing resolver becomes obsolete and a newer one becomes available that provides updated access to the same type of assets as the existing one. This update process is meant to be performed at runtime.

If a null resolver is provided, nothing will be done. If no matching resolver is found, the provided resolver will be added to the end of the AssetManager resolvers queue. The replacement only occurs with the first matching resolver. Any additional matching resolvers are untouched.

Parameters

[in]	updated_asset_resolver	The asset resolver to replace the resolver of matching type with.
[in]	type	The type of AssetResolver to update. Only resolvers of the specified type will be replaced by the updated resolver.

Reimplemented in flutter::PlatformViewAndroid.

Definition at line 195 of file platform_view.cc.

                                         {
  delegate_.UpdateAssetResolverByType(std::move(updated_asset_resolver), type);
}

UpdateSemantics()

void PlatformView::UpdateSemantics ( SemanticsNodeUpdates  updates, CustomAccessibilityActionUpdates  actions  )

virtual

Used by the framework to tell the embedder to apply the specified semantics node updates. The default implementation of this method does nothing.

See also

SemanticsNode, SemticsNodeUpdates, CustomAccessibilityActionUpdates

Parameters

[in]	updates	A map with the stable semantics node identifier as key and the node properties as the value.
[in]	actions	A map with the stable semantics node identifier as key and the custom node action as the value.

Reimplemented in flutter::PlatformViewAndroid, flutter::PlatformViewIOS, flutter::PlatformViewEmbedder, and flutter_runner::PlatformView.

Definition at line 123 of file platform_view.cc.

                                              {}

Member Data Documentation

delegate_

PlatformView::Delegate& flutter::PlatformView::delegate_

protected

Definition at line 962 of file platform_view.h.

pointer_data_packet_converter_

PointerDataPacketConverter flutter::PlatformView::pointer_data_packet_converter_

protected

Definition at line 964 of file platform_view.h.

task_runners_

const TaskRunners flutter::PlatformView::task_runners_

protected

Definition at line 963 of file platform_view.h.

weak_factory_

fml::WeakPtrFactory<PlatformView> flutter::PlatformView::weak_factory_

protected

Definition at line 965 of file platform_view.h.

---

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

• shell/common/platform_view.h
• shell/common/platform_view.cc