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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMMON_PLATFORM_VIEW_H_
#define COMMON_PLATFORM_VIEW_H_
#include <memory>
#include "flutter/common/task_runners.h"
#include "flutter/flow/texture.h"
#include "flutter/fml/macros.h"
#include "flutter/fml/memory/weak_ptr.h"
#include "flutter/lib/ui/semantics/custom_accessibility_action.h"
#include "flutter/lib/ui/semantics/semantics_node.h"
#include "flutter/lib/ui/window/platform_message.h"
#include "flutter/lib/ui/window/pointer_data_packet.h"
#include "flutter/lib/ui/window/pointer_data_packet_converter.h"
#include "flutter/lib/ui/window/viewport_metrics.h"
#include "flutter/shell/common/pointer_data_dispatcher.h"
#include "flutter/shell/common/surface.h"
#include "flutter/shell/common/vsync_waiter.h"
#include "third_party/skia/include/core/SkSize.h"
#include "third_party/skia/include/gpu/GrContext.h"
namespace flutter {
class Shell;
//------------------------------------------------------------------------------
/// @brief 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.
///
class PlatformView {
public:
//----------------------------------------------------------------------------
/// @brief 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.
///
class Delegate {
public:
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the platform view was created
/// with the given render surface. This surface is platform
/// (iOS, Android) and client-rendering API (OpenGL, Software,
/// Metal, Vulkan) specific. This is usually a sign to the
/// rasterizer to setup and begin rendering to that surface.
///
/// @param[in] surface The surface
///
virtual void OnPlatformViewCreated(std::unique_ptr<Surface> surface) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the platform view was destroyed.
/// This is usually a sign to the rasterizer to suspend
/// rendering a previously configured surface and collect any
/// intermediate resources.
///
virtual void OnPlatformViewDestroyed() = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the specified callback needs to
/// be invoked after the rasterizer is done rendering the next
/// frame. This callback will be called on the render thread and
/// it is caller responsibility to perform any re-threading as
/// necessary. 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.
///
/// @attention The callback will be invoked on the render thread and not
/// the calling thread.
///
/// @param[in] closure The callback to execute on the next frame.
///
virtual void OnPlatformViewSetNextFrameCallback(
const fml::closure& closure) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate the viewport metrics of the platform
/// view have been updated. The rasterizer will need to be
/// reconfigured to render the frame in the updated viewport
/// metrics.
///
/// @param[in] metrics The updated viewport metrics.
///
virtual void OnPlatformViewSetViewportMetrics(
const ViewportMetrics& metrics) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the platform has dispatched a
/// platform message from the embedder to the Flutter
/// application. This message must be forwarded to the running
/// isolate hosted by the engine on the UI thread.
///
/// @param[in] message The platform message to dispatch to the running
/// root isolate.
///
virtual void OnPlatformViewDispatchPlatformMessage(
fml::RefPtr<PlatformMessage> message) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the platform view has encountered
/// a pointer event. This pointer event needs to be forwarded to
/// the running root isolate hosted by the engine on the UI
/// thread.
///
/// @param[in] packet The pointer data packet containing multiple pointer
/// events.
///
virtual void OnPlatformViewDispatchPointerDataPacket(
std::unique_ptr<PointerDataPacket> packet) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the platform view has encountered
/// an accessibility related action on the specified node. This
/// event must be forwarded to the running root isolate hosted
/// by the engine on the UI thread.
///
/// @param[in] id The identifier of the accessibility node.
/// @param[in] action The accessibility related action performed on the
/// node of the specified ID.
/// @param[in] args An optional list of argument that apply to the
/// specified action.
///
virtual void OnPlatformViewDispatchSemanticsAction(
int32_t id,
SemanticsAction action,
std::vector<uint8_t> args) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the embedder has expressed an
/// opinion about whether the accessibility tree needs to be
/// enabled or disabled. This information needs to be forwarded
/// to the root isolate running on the UI thread.
///
/// @param[in] enabled Whether the accessibility tree is enabled or
/// disabled.
///
virtual void OnPlatformViewSetSemanticsEnabled(bool enabled) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the embedder has expressed an
/// opinion about the features to enable in the accessibility
/// tree.
///
/// 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.
///
/// @param[in] flags The features to enable in the accessibility tree.
///
virtual void OnPlatformViewSetAccessibilityFeatures(int32_t flags) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the embedder has specified a
/// texture that it want 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.
///
/// @param[in] texture The texture that is being updated by the embedder
/// but composited by Flutter in its own hierarchy.
///
virtual void OnPlatformViewRegisterTexture(
std::shared_ptr<Texture> texture) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the embedder will no longer
/// attempt to composite the specified texture within the layer
/// tree. This allows the rasterizer to collect associated
/// resources.
///
/// @param[in] texture_id The identifier of the texture to unregister. If
/// the texture has not been previously registered,
/// this call does nothing.
///
virtual void OnPlatformViewUnregisterTexture(int64_t texture_id) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the embedder has updated the
/// contents of the texture with the specified identifier.
/// 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 composited
/// with all updated external textures.
///
/// @param[in] texture_id The identifier of the texture that has been
/// updated.
///
virtual void OnPlatformViewMarkTextureFrameAvailable(
int64_t texture_id) = 0;
};
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @param delegate The delegate. This is typically the shell.
/// @param[in] task_runners The task runners used by this platform view.
///
explicit PlatformView(Delegate& delegate, TaskRunners task_runners);
//----------------------------------------------------------------------------
/// @brief 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 ~PlatformView();
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @return A vsync waiter. If is an internal error to return a null
/// waiter.
///
virtual std::unique_ptr<VsyncWaiter> CreateVSyncWaiter();
//----------------------------------------------------------------------------
/// @brief 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 HandlePlatformMessage()
///
/// @param[in] message The platform message to deliver to the root isolate.
///
void DispatchPlatformMessage(fml::RefPtr<PlatformMessage> message);
//----------------------------------------------------------------------------
/// @brief 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 DisplatchPlatformMessage()
///
/// @param[in] message The message
///
virtual void HandlePlatformMessage(fml::RefPtr<PlatformMessage> message);
//----------------------------------------------------------------------------
/// @brief Used by embedders to dispatch an accessibility action to a
/// running isolate hosted by the engine.
///
/// @param[in] id The identifier of the accessibility node on which to
/// perform the action.
/// @param[in] action The action
/// @param[in] args The arguments
///
void DispatchSemanticsAction(int32_t id,
SemanticsAction action,
std::vector<uint8_t> args);
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @param[in] enabled Whether the accessibility tree needs to be generated.
///
virtual void SetSemanticsEnabled(bool enabled);
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @param[in] flags The features to enable in the accessibility tree.
///
virtual void SetAccessibilityFeatures(int32_t flags);
//----------------------------------------------------------------------------
/// @brief Used by the framework to tell the embedder to apply the
/// specified semantics node updates. The default implementation
/// of this method does nothing.
///
/// @see SemanticsNode, SemticsNodeUpdates,
/// CustomAccessibilityActionUpdates
///
/// @param[in] updates A map with the stable semantics node identifier as
/// key and the node properties as the value.
/// @param[in] actions A map with the stable semantics node identifier as
/// key and the custom node action as the value.
///
virtual void UpdateSemantics(SemanticsNodeUpdates updates,
CustomAccessibilityActionUpdates actions);
//----------------------------------------------------------------------------
/// @brief Used by embedders to specify the updated viewport metrics. 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.
///
/// @param[in] metrics The updated viewport metrics.
///
void SetViewportMetrics(const ViewportMetrics& metrics);
//----------------------------------------------------------------------------
/// @brief 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.
///
void NotifyCreated();
//----------------------------------------------------------------------------
/// @brief 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.
///
virtual void NotifyDestroyed();
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @return 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.
///
virtual sk_sp<GrContext> CreateResourceContext() const;
//----------------------------------------------------------------------------
/// @brief 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.
///
virtual void ReleaseResourceContext() const;
//--------------------------------------------------------------------------
/// @brief Returns a platform-specific PointerDataDispatcherMaker so the
/// `Engine` can construct the PointerDataPacketDispatcher based
/// on platforms.
virtual PointerDataDispatcherMaker GetDispatcherMaker();
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @return The weak pointer to the platform view.
///
fml::WeakPtr<PlatformView> GetWeakPtr() const;
//----------------------------------------------------------------------------
/// @brief 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.
///
virtual void OnPreEngineRestart() const;
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @param[in] closure The callback to execute on the render thread when the
/// next frame gets rendered.
///
void SetNextFrameCallback(const fml::closure& closure);
//----------------------------------------------------------------------------
/// @brief 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.
///
/// @param[in] packet The pointer data packet to dispatch to the framework.
///
void DispatchPointerDataPacket(std::unique_ptr<PointerDataPacket> packet);
//--------------------------------------------------------------------------
/// @brief 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 UnregisterTexture, MarkTextureFrameAvailable
///
/// @param[in] texture The texture that is being updated by the embedder
/// but composited by Flutter in its own hierarchy.
///
void RegisterTexture(std::shared_ptr<flutter::Texture> texture);
//--------------------------------------------------------------------------
/// @brief 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 RegisterTexture, MarkTextureFrameAvailable
///
/// @param[in] texture_id The identifier of the texture to unregister. If
/// the texture has not been previously registered,
/// this call does nothing.
///
void UnregisterTexture(int64_t texture_id);
//--------------------------------------------------------------------------
/// @brief 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 RegisterTexture, UnregisterTexture
///
/// @param[in] texture_id The identifier of the texture that has been
/// updated.
///
void MarkTextureFrameAvailable(int64_t texture_id);
protected:
PlatformView::Delegate& delegate_;
const TaskRunners task_runners_;
PointerDataPacketConverter pointer_data_packet_converter_;
SkISize size_;
fml::WeakPtrFactory<PlatformView> weak_factory_;
// Unlike all other methods on the platform view, this is called on the
// GPU task runner.
virtual std::unique_ptr<Surface> CreateRenderingSurface();
private:
FML_DISALLOW_COPY_AND_ASSIGN(PlatformView);
};
} // namespace flutter
#endif // COMMON_PLATFORM_VIEW_H_