// 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 SHELL_COMMON_ACE_ENGINE_H_
#define SHELL_COMMON_ACE_ENGINE_H_
#include <memory>
#include <string>
#include "flutter/assets/asset_manager.h"
#include "flutter/common/task_runners.h"
#include "flutter/fml/macros.h"
#include "flutter/fml/memory/weak_ptr.h"
#include "flutter/lib/ui/semantics/semantics_node.h"
#include "flutter/lib/ui/text/font_collection.h"
#include "flutter/lib/ui/window/platform_message.h"
#include "flutter/lib/ui/window/viewport_metrics.h"
#include "flutter/runtime/runtime_controller.h"
#include "flutter/runtime/runtime_delegate.h"
#include "flutter/shell/common/animator.h"
#include "flutter/shell/common/rasterizer.h"
#include "flutter/shell/common/run_configuration.h"
#include "flutter/shell/common/shell_io_manager.h"
#include "include/core/SkPicture.h"
namespace flutter {
//------------------------------------------------------------------------------
/// The engine is a component owned by the shell that resides on the UI task
/// runner and is responsible for managing the needs of the root isolate and its
/// runtime. The engine can only be created, accessed and collected on the UI
/// task runner. Each shell owns exactly one instance of the engine.
///
/// The root isolate of Flutter application gets "window" bindings. Using these
/// bindings, the application can schedule frames, post layer-trees for
/// rendering, ask to decompress images and upload them to the GPU, etc..
/// Non-root isolates of the VM do not get any of these capabilities and are run
/// in a VM managed thread pool (so if they did have "window", the threading
/// guarantees needed for engine operation would be violated).
///
/// The engine is responsible for the entire life-cycle of the root isolate.
/// When the engine is collected, its owner assumes that the root isolate has
/// been shutdown and appropriate resources collected. While each engine
/// instance can only manage a single instance of a root isolate, it may restart
/// that isolate on request. This is how the cold-restart development scenario
/// is supported.
///
/// When the engine instance is initially created, the root isolate is created
/// but it is not in the |DartIsolate::Phase::Running| phase yet. It only moves
/// into that phase when a successful call to `Engine::Run` is made.
///
/// @see `Shell`
///
/// @note This name of this class is perhaps a bit unfortunate and has
/// sometimes been the cause of confusion. For a class named "Engine"
/// in the Flutter "Engine" repository, its responsibilities are
/// decidedly unremarkable. But, it does happen to be the primary
/// entry-point used by components higher up in the Flutter tech stack
/// (usually in Dart code) to peer into the lower level functionality.
/// Besides, the authors haven't been able to come up with a more apt
/// name and it does happen to be one of the older classes in the
/// repository.
///
class Engine final : public RuntimeDelegate {
public:
// ACE PC preivew
using IdleCallback = std::function<void(int64_t)>;
//----------------------------------------------------------------------------
/// @brief Indicates the result of the call to `Engine::Run`.
///
enum class RunStatus {
//--------------------------------------------------------------------------
/// The call to |Engine::Run| was successful and the root isolate is in the
/// `DartIsolate::Phase::Running` phase with its entry-point invocation
/// already pending in the task queue.
///
Success,
//--------------------------------------------------------------------------
/// The engine can only manage a single instance of a root isolate. If a
/// previous call to run the root isolate was successful, subsequent calls
/// to run the isolate (even if the new run configuration is different) will
/// be rejected.
///
/// It is up to the caller to decide to re-purpose the running isolate,
/// terminate it, or use another shell to host the new isolate. This is
/// mostly used by embedders which have a fire-and-forget strategy to root
/// isolate launch. For example, the application may try to "launch" and
/// isolate when the embedders launches or resumes from a paused state. That
/// the isolate is running is not necessarily a failure condition for them.
/// But from the engine's perspective, the run configuration was rejected.
///
FailureAlreadyRunning,
//--------------------------------------------------------------------------
/// Used to indicate to the embedder that a root isolate was not already
/// running but the run configuration was not valid and root isolate could
/// not be moved into the `DartIsolate::Phase::Running` phase.
///
/// The caller must attempt the run call again with a valid configuration.
/// The set of all failure modes is massive and can originate from a variety
/// of sub-components. The engine will attempt to log the same when
/// possible. With the aid of logs, the common causes of failure are:
///
/// * AOT assets give to JIT/DBC mode VM's and vice-versa.
/// * The assets could not be found in the asset manager. Callers must make
/// sure their run configuration asset managers have been correctly setup.
/// * The assets themselves were corrupt or invalid. Callers must make sure
/// their asset delivery mechanisms are sound.
/// * The application entry-point or the root library of the entry-point
/// specified in the run configuration was invalid. Callers must make sure
/// that the entry-point is present in the application. If the name of the
/// entrypoint is not "main" in the root library, callers must also ensure
/// that the snapshotting process has not tree-shaken away this
/// entrypoint. This requires the decoration of the entrypoint with the
/// `@pragma('vm:entry-point')` directive. This problem will manifest in
/// AOT mode operation of the Dart VM.
///
Failure,
};
//----------------------------------------------------------------------------
/// @brief While the engine operates entirely on the UI task runner, it
/// needs the capabilities of the other components to fulfill the
/// requirements of the root isolate. The shell is the only class
/// that implements this interface as no other component has
/// access to all components in a thread safe manner. The engine
/// delegates these tasks to the shell via this interface.
///
class Delegate {
public:
//--------------------------------------------------------------------------
/// @brief When the Flutter application has a message to send to the
/// underlying platform, the message needs to be forwarded to
/// the platform on the the appropriate thread (via the platform
/// task runner). The engine delegates this task to the shell
/// via this method.
///
/// @see `PlatformView::HandlePlatformMessage`
///
/// @param[in] message The message from the Flutter application to send to
/// the underlying platform.
///
virtual void OnEngineHandlePlatformMessage(
fml::RefPtr<PlatformMessage> message) = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the delegate that the root isolate of the
/// application is about to be discarded and a new isolate with
/// the same runtime started in its place. This should only
/// happen in the Flutter "debug" runtime mode in the
/// cold-restart scenario. The embedder may need to reset native
/// resource in response to the restart.
///
/// @see `PlatformView::OnPreEngineRestart`
///
virtual void OnPreEngineRestart() = 0;
//--------------------------------------------------------------------------
/// @brief Notifies the shell that the application has an opinion about
/// whether its frame timings need to be reported backed to it.
/// Due to the asynchronous nature of rendering in Flutter, it
/// is not possible for the application to determine the total
/// time it took to render a specific frame. While the
/// layer-tree is constructed on the UI thread, it needs to be
/// rendering on the GPU thread. Dart code cannot execute on
/// this thread. So any instrumentation about the frame times
/// gathered on this thread needs to be aggregated and sent back
/// to the UI thread for processing in Dart.
///
/// When the application indicates that frame times need to be
/// reported, it collects this information till a specified
/// number of data points are gathered. Then this information is
/// sent back to Dart code via `Engine::ReportTimings`.
///
/// This option is engine counterpart of the
/// `Window._setNeedsReportTimings` in `window.dart`.
///
/// @param[in] needs_reporting If reporting information should be
/// collected and send back to Dart.
///
virtual void SetNeedsReportTimings(bool needs_reporting) = 0;
};
//----------------------------------------------------------------------------
/// @brief Creates an instance of the engine. This is done by the Shell
/// on the the UI task runner.
///
/// @param delegate The object used by the engine to perform
/// tasks that require access to components
/// that cannot be safely accessed by the
/// engine. This is the shell.
/// @param vm An instance of the running Dart VM.
/// @param[in] isolate_snapshot The snapshot used to create the root
/// isolate. Even though the isolate is not
/// `DartIsolate::Phase::Running` phase, it is
/// created when the engine is created. This
/// requires access to the isolate snapshot
/// upfront.
/// @param[in] shared_snapshot The portion of the isolate snapshot shared
/// among multiple isolates.
// TODO(chinmaygarde): This is probably redundant now that the IO manager is
// it's own object.
/// @param[in] task_runners The task runners used by the shell that
/// hosts this engine.
/// @param[in] settings The settings used to initialize the shell
/// and the engine.
/// @param[in] animator The animator used to schedule frames.
// TODO(chinmaygarde): Move this to `Engine::Delegate`
/// @param[in] snapshot_delegate The delegate used to fulfill requests to
/// snapshot a specified scene. The engine
/// cannot snapshot a scene on the UI thread
/// directly because the scene (described via
/// an `SkPicture`) may reference resources on
/// the GPU and there is no GPU context current
/// on the UI thread. The delegate is a
/// component that has access to all the
/// requisite GPU resources.
/// @param[in] io_manager The IO manager used by this root isolate to
/// schedule tasks that manage resources on the
/// GPU.
///
Engine(Delegate& delegate,
TaskRunners task_runners,
Settings settings,
std::unique_ptr<Animator> animator,
fml::WeakPtr<IOManager> io_manager);
//----------------------------------------------------------------------------
/// @brief Destroys the engine engine. Called by the shell on the UI task
/// runner. The running root isolate is terminated and will no
/// longer access the task runner after this call returns. This
/// allows the embedder to tear down the thread immediately if
/// needed.
///
~Engine() override;
//----------------------------------------------------------------------------
/// @brief Gets the refresh rate in frames per second of the vsync waiter
/// used by the animator managed by this engine. This information
/// is purely advisory and is not used by any component. It is
/// only used by the tooling to visualize frame performance.
///
/// @attention The display refresh rate is useless for frame scheduling
/// because it can vary and more accurate frame specific
/// information is given to the engine by the vsync waiter
/// already. However, this call is used by the tooling to ask very
/// high level questions about display refresh rate. For example,
/// "Is the display 60 or 120Hz?". This information is quite
/// unreliable (not available immediately on launch on some
/// platforms), variable and advisory. It must not be used by any
/// component that claims to use it to perform accurate frame
/// scheduling.
///
/// @return The display refresh rate in frames per second. This may change
/// from frame to frame, throughout the lifecycle of the
/// application, and, may not be available immediately upon
/// application launch.
///
float GetDisplayRefreshRate() const;
//----------------------------------------------------------------------------
/// @return The pointer to this instance of the engine. The engine may
/// only be accessed safely on the UI task runner.
///
fml::WeakPtr<Engine> GetWeakPtr() const;
//----------------------------------------------------------------------------
/// @brief Moves the root isolate to the `DartIsolate::Phase::Running`
/// phase on a successful call to this method.
///
/// The isolate itself is created when the engine is created, but
/// it is not yet in the running phase. This is done to amortize
/// initial time taken to launch the root isolate. The isolate
/// snapshots used to run the isolate can be fetched on another
/// thread while the engine itself is launched on the UI task
/// runner.
///
/// Repeated calls to this method after a successful run will be
/// rejected even if the run configuration is valid (with the
/// appropriate error returned).
///
/// @param[in] configuration The configuration used to run the root isolate.
/// The configuration must be valid.
///
/// @return The result of the call to run the root isolate.
///
FML_WARN_UNUSED_RESULT
RunStatus Run(RunConfiguration configuration);
//----------------------------------------------------------------------------
/// @brief Tears down an existing root isolate, reuses the components of
/// that isolate and attempts to launch a new isolate using the
/// given the run configuration. This is only used in the
/// "debug" Flutter runtime mode in the cold-restart scenario.
///
/// @attention This operation must be performed with care as even a
/// non-successful restart will still tear down any existing root
/// isolate. In such cases, the engine and its shell must be
/// discarded.
///
/// @param[in] configuration The configuration used to launch the new
/// isolate.
///
/// @return Whether the restart was successful. If not, the engine and its
/// shell must be discarded.
///
FML_WARN_UNUSED_RESULT
bool Restart(RunConfiguration configuration);
//----------------------------------------------------------------------------
/// @brief Updates the asset manager referenced by the root isolate of a
/// Flutter application. This happens implicitly in the call to
/// `Engine::Run` and `Engine::Restart` as the asset manager is
/// referenced from the run configuration provided to those calls.
/// In addition to the the `Engine::Run` and `Engine::Restart`
/// calls, the tooling may need to update the assets available to
/// the application as the user adds them to their project. For
/// example, these assets may be referenced by code that is newly
/// patched in after a hot-reload. Neither the shell or the
/// isolate in relaunched in such cases. The tooling usually
/// patches in the new assets in a temporary location and updates
/// the asset manager to point to that location.
///
/// @param[in] asset_manager The new asset manager to use for the running
/// root isolate.
///
/// @return If the asset manager was successfully replaced. This may fail
/// if the new asset manager is invalid.
///
bool UpdateAssetManager(std::shared_ptr<AssetManager> asset_manager);
//----------------------------------------------------------------------------
/// @brief Notifies the engine that it is time to begin working on a new
/// frame previously scheduled via a call to
/// `Engine::ScheduleFrame`. This call originates in the animator.
///
/// The frame time given as the argument indicates the point at
/// which the current frame interval began. It is very slightly
/// (because of scheduling overhead) in the past. If a new layer
/// tree is not produced and given to the GPU task runner within
/// one frame interval from this point, the Flutter application
/// will jank.
///
/// If an root isolate is running, this method calls the
/// `::_beginFrame` method in `hooks.dart`. If a root isolate is
/// not running, this call does nothing.
///
/// This method encapsulates the entire UI thread frame workload.
/// The following (mis)behavior in the functioning of the method
/// will cause the jank in the Flutter application:
/// * The time taken by this method to create a layer-tree exceeds
/// on frame interval (for example, 16.66 ms on a 60Hz display).
/// * The time take by this method to generate a new layer-tree
/// causes the current layer-tree pipeline depth to change. To
/// illustrate this point, note that maximum pipeline depth used
/// by layer tree in the engine is 2. If both the UI and GPU
/// task runner tasks finish within one frame interval, the
/// pipeline depth is one. If the UI thread happens to be
/// working on a frame when the GPU thread is still not done
/// with the previous frame, the pipeline depth is 2. When the
/// pipeline depth changes from 1 to 2, animations and UI
/// interactions that cause the generation of the new layer tree
/// appropriate for (frame_time + one frame interval) will
/// actually end up at (frame_time + two frame intervals). This
/// is not what code running on the UI thread expected would
/// happen. This causes perceptible jank.
///
/// @param[in] frame_time The point at which the current frame interval
/// began. May be used by animation interpolators,
/// physics simulations, etc..
///
void BeginFrame(fml::TimePoint frame_time);
void ReportTimings(std::vector<int64_t> timings);
//----------------------------------------------------------------------------
/// @brief Notifies the engine that the UI task runner is not expected to
/// undertake a new frame workload till a specified timepoint. The
/// timepoint is measured in microseconds against the system's
/// monotonic clock. It is recommended that the clock be accessed
/// via `Dart_TimelineGetMicros` from `dart_api.h` for
/// consistency. In reality, the clocks used by Dart, FML and
/// std::steady_clock are all the same and the timepoints can be
/// converted from on clock type to another.
///
/// The Dart VM uses this notification to schedule book-keeping
/// tasks that may include a garbage collection. In this way, it
/// is less likely for the VM to perform such (potentially long
/// running) tasks in the middle of a frame workload.
///
/// This notification is advisory. That is, not providing this
/// notification does not mean garbage collection is postponed
/// till this call is made. If this notification is not provided,
/// garbage collection will happen based on the usual heuristics
/// used by the Dart VM.
///
/// Currently, this idle notification is delivered to the engine
/// at two points. Once, the deadline is calculated based on how
/// much time in the current frame interval is left on the UI task
/// runner. Since the next frame workload cannot begin till at
/// least the next callback from the vsync waiter, this period may
/// be used to used as a "small" idle notification. On the other
/// hand, if no more frames are scheduled, a large (but arbitrary)
/// idle notification deadline is chosen for a "big" idle
/// notification. Again, this notification does not guarantee
/// collection, just gives the Dart VM more hints about opportune
/// moments to perform collections.
///
// TODO(chinmaygarde): This should just use fml::TimePoint instead of having
// to remember that the unit is microseconds (which is no used anywhere else
// in the engine).
///
/// @param[in] deadline The deadline as a timepoint in microseconds measured
/// against the system monotonic clock. Use
/// `Dart_TimelineGetMicros()`, for consistency.
///
void NotifyIdle(int64_t deadline);
//----------------------------------------------------------------------------
/// @brief Indicates to the Flutter application that it has obtained a
/// rendering surface. This is a good opportunity for the engine
/// to start servicing any outstanding frame requests from the
/// Flutter applications. Flutter application that have no
/// rendering concerns may never get a rendering surface. In such
/// cases, while their root isolate can perform as normal, any
/// frame requests made by them will never be serviced and layer
/// trees produced outside of frame workloads will be dropped.
///
/// Very close to when this call is made, the application can
/// expect the updated viewport metrics. Rendering only begins
/// when the Flutter application gets an output surface and a
/// valid set of viewport metrics.
///
/// @see `OnOutputSurfaceDestroyed`
///
void OnOutputSurfaceCreated();
//----------------------------------------------------------------------------
/// @brief Indicates to the Flutter application that a previously
/// acquired rendering surface has been lost. Further frame
/// requests will no longer be serviced and any layer tree
/// submitted for rendering will be dropped. If/when a new surface
/// is acquired, a new layer tree must be generated.
///
/// @see `OnOutputSurfaceCreated`
///
void OnOutputSurfaceDestroyed();
//----------------------------------------------------------------------------
/// @brief Ace PC preivew
///
void SetIdleNotificationCallback(const IdleCallback& idleCallback);
//----------------------------------------------------------------------------
/// @brief Updates the viewport metrics for the currently running Flutter
/// application. The viewport metrics detail the size of the
/// rendering viewport in texels as well as edge insets if
/// present.
///
/// @see `ViewportMetrics`
///
/// @param[in] metrics The metrics
///
void SetViewportMetrics(const ViewportMetrics& metrics);
//----------------------------------------------------------------------------
/// @brief Notifies the engine that the embedder has sent it a message.
/// This call originates in the platform view and has been
/// forwarded to the engine on the UI task runner here.
///
/// @param[in] message The message sent from the embedder to the Dart
/// application.
///
void DispatchPlatformMessage(fml::RefPtr<PlatformMessage> message);
//----------------------------------------------------------------------------
/// @brief Notifies the engine that the embedder has sent it a pointer
/// data packet. A pointer data packet may contain multiple
/// input events. This call originates in the platform view and
/// the shell has forwarded the same to the engine on the UI task
/// runner here.
///
/// @param[in] packet The pointer data packet containing multiple
/// input events.
/// @param[in] trace_flow_id The trace flow identifier associated with the
/// pointer data packet. The engine uses this trace
/// identifier to connect trace flows in the
/// timeline from the input event event to the
/// frames generated due to those input events.
/// These flows are tagged as "PointerEvent" in the
/// timeline and allow grouping frames and input
/// events into logical chunks.
///
void DispatchPointerDataPacket(const PointerDataPacket& packet,
uint64_t trace_flow_id);
// |RuntimeDelegate|
void ScheduleFrame(bool regenerate_layer_tree = true) override;
// |RuntimeDelegate|
FontCollection& GetFontCollection() override;
private:
Engine::Delegate& delegate_;
const Settings settings_;
std::unique_ptr<Animator> animator_;
std::unique_ptr<RuntimeController> runtime_controller_;
std::string initial_route_;
ViewportMetrics viewport_metrics_;
std::shared_ptr<AssetManager> asset_manager_;
bool activity_running_;
bool have_surface_;
std::once_flag font_flag_;
std::unique_ptr<FontCollection> font_collection_;
fml::WeakPtrFactory<Engine> weak_factory_;
// |RuntimeDelegate|
std::string DefaultRouteName() override;
// |RuntimeDelegate|
void Render(std::unique_ptr<flutter::LayerTree> layer_tree) override;
void HandlePlatformMessage(fml::RefPtr<PlatformMessage> message) override;
void SetNeedsReportTimings(bool value) override;
void StopAnimator();
void StartAnimatorIfPossible();
bool HandleLifecyclePlatformMessage(PlatformMessage* message);
bool HandleNavigationPlatformMessage(fml::RefPtr<PlatformMessage> message);
bool HandleLocalizationPlatformMessage(PlatformMessage* message);
void HandleSettingsPlatformMessage(PlatformMessage* message);
void HandleAssetPlatformMessage(fml::RefPtr<PlatformMessage> message);
bool GetAssetAsBuffer(const std::string& name, std::vector<uint8_t>* data);
RunStatus PrepareAndLaunchIsolate(RunConfiguration configuration);
friend class testing::ShellTest;
FML_DISALLOW_COPY_AND_ASSIGN(Engine);
};
} // namespace flutter
#endif // SHELL_COMMON_ENGINE_H_