embedder.h

// 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 FLUTTER_EMBEDDER_H_
#define FLUTTER_EMBEDDER_H_

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#if defined(__cplusplus)
extern "C" {
#endif

#ifndef FLUTTER_EXPORT
#define FLUTTER_EXPORT
#endif  // FLUTTER_EXPORT

#ifdef FLUTTER_API_SYMBOL_PREFIX
#define FLUTTER_EMBEDDING_CONCAT(a, b) a##b
#define FLUTTER_EMBEDDING_ADD_PREFIX(symbol, prefix) \
  FLUTTER_EMBEDDING_CONCAT(prefix, symbol)
#define FLUTTER_API_SYMBOL(symbol) \
  FLUTTER_EMBEDDING_ADD_PREFIX(symbol, FLUTTER_API_SYMBOL_PREFIX)
#else
#define FLUTTER_API_SYMBOL(symbol) symbol
#endif

#define FLUTTER_ENGINE_VERSION 1

typedef enum {
  kSuccess = 0,
  kInvalidLibraryVersion,
  kInvalidArguments,
  kInternalInconsistency,
} FlutterEngineResult;

typedef enum {
  kOpenGL,
  kSoftware,
} FlutterRendererType;

/// Additional accessibility features that may be enabled by the platform.
/// Must match the `AccessibilityFeatures` enum in window.dart.
typedef enum {
  /// Indicate there is a running accessibility service which is changing the
  /// interaction model of the device.
  kFlutterAccessibilityFeatureAccessibleNavigation = 1 << 0,
  /// Indicate the platform is inverting the colors of the application.
  kFlutterAccessibilityFeatureInvertColors = 1 << 1,
  /// Request that animations be disabled or simplified.
  kFlutterAccessibilityFeatureDisableAnimations = 1 << 2,
  /// Request that text be rendered at a bold font weight.
  kFlutterAccessibilityFeatureBoldText = 1 << 3,
  /// Request that certain animations be simplified and parallax effects
  // removed.
  kFlutterAccessibilityFeatureReduceMotion = 1 << 4,
} FlutterAccessibilityFeature;

/// The set of possible actions that can be conveyed to a semantics node.
///
/// Must match the `SemanticsAction` enum in semantics.dart.
typedef enum {
  /// The equivalent of a user briefly tapping the screen with the finger
  /// without
  /// moving it.
  kFlutterSemanticsActionTap = 1 << 0,
  /// The equivalent of a user pressing and holding the screen with the finger
  /// for a few seconds without moving it.
  kFlutterSemanticsActionLongPress = 1 << 1,
  /// The equivalent of a user moving their finger across the screen from right
  /// to left.
  kFlutterSemanticsActionScrollLeft = 1 << 2,
  /// The equivalent of a user moving their finger across the screen from left
  /// to
  /// right.
  kFlutterSemanticsActionScrollRight = 1 << 3,
  /// The equivalent of a user moving their finger across the screen from bottom
  /// to top.
  kFlutterSemanticsActionScrollUp = 1 << 4,
  /// The equivalent of a user moving their finger across the screen from top to
  /// bottom.
  kFlutterSemanticsActionScrollDown = 1 << 5,
  /// Increase the value represented by the semantics node.
  kFlutterSemanticsActionIncrease = 1 << 6,
  /// Decrease the value represented by the semantics node.
  kFlutterSemanticsActionDecrease = 1 << 7,
  /// A request to fully show the semantics node on screen.
  kFlutterSemanticsActionShowOnScreen = 1 << 8,
  /// Move the cursor forward by one character.
  kFlutterSemanticsActionMoveCursorForwardByCharacter = 1 << 9,
  /// Move the cursor backward by one character.
  kFlutterSemanticsActionMoveCursorBackwardByCharacter = 1 << 10,
  /// Set the text selection to the given range.
  kFlutterSemanticsActionSetSelection = 1 << 11,
  /// Copy the current selection to the clipboard.
  kFlutterSemanticsActionCopy = 1 << 12,
  /// Cut the current selection and place it in the clipboard.
  kFlutterSemanticsActionCut = 1 << 13,
  /// Paste the current content of the clipboard.
  kFlutterSemanticsActionPaste = 1 << 14,
  /// Indicate that the node has gained accessibility focus.
  kFlutterSemanticsActionDidGainAccessibilityFocus = 1 << 15,
  /// Indicate that the node has lost accessibility focus.
  kFlutterSemanticsActionDidLoseAccessibilityFocus = 1 << 16,
  /// Indicate that the user has invoked a custom accessibility action.
  kFlutterSemanticsActionCustomAction = 1 << 17,
  /// A request that the node should be dismissed.
  kFlutterSemanticsActionDismiss = 1 << 18,
  /// Move the cursor forward by one word.
  kFlutterSemanticsActionMoveCursorForwardByWord = 1 << 19,
  /// Move the cursor backward by one word.
  kFlutterSemanticsActionMoveCursorBackwardByWord = 1 << 20,
} FlutterSemanticsAction;

/// The set of properties that may be associated with a semantics node.
///
/// Must match the `SemanticsFlag` enum in semantics.dart.
typedef enum {
  /// The semantics node has the quality of either being "checked" or
  /// "unchecked".
  kFlutterSemanticsFlagHasCheckedState = 1 << 0,
  /// Whether a semantics node is checked.
  kFlutterSemanticsFlagIsChecked = 1 << 1,
  /// Whether a semantics node is selected.
  kFlutterSemanticsFlagIsSelected = 1 << 2,
  /// Whether the semantic node represents a button.
  kFlutterSemanticsFlagIsButton = 1 << 3,
  /// Whether the semantic node represents a text field.
  kFlutterSemanticsFlagIsTextField = 1 << 4,
  /// Whether the semantic node currently holds the user's focus.
  kFlutterSemanticsFlagIsFocused = 1 << 5,
  /// The semantics node has the quality of either being "enabled" or
  /// "disabled".
  kFlutterSemanticsFlagHasEnabledState = 1 << 6,
  /// Whether a semantic node that hasEnabledState is currently enabled.
  kFlutterSemanticsFlagIsEnabled = 1 << 7,
  /// Whether a semantic node is in a mutually exclusive group.
  kFlutterSemanticsFlagIsInMutuallyExclusiveGroup = 1 << 8,
  /// Whether a semantic node is a header that divides content into sections.
  kFlutterSemanticsFlagIsHeader = 1 << 9,
  /// Whether the value of the semantics node is obscured.
  kFlutterSemanticsFlagIsObscured = 1 << 10,
  /// Whether the semantics node is the root of a subtree for which a route name
  /// should be announced.
  kFlutterSemanticsFlagScopesRoute = 1 << 11,
  /// Whether the semantics node label is the name of a visually distinct route.
  kFlutterSemanticsFlagNamesRoute = 1 << 12,
  /// Whether the semantics node is considered hidden.
  kFlutterSemanticsFlagIsHidden = 1 << 13,
  /// Whether the semantics node represents an image.
  kFlutterSemanticsFlagIsImage = 1 << 14,
  /// Whether the semantics node is a live region.
  kFlutterSemanticsFlagIsLiveRegion = 1 << 15,
  /// The semantics node has the quality of either being "on" or "off".
  kFlutterSemanticsFlagHasToggledState = 1 << 16,
  /// If true, the semantics node is "on". If false, the semantics node is
  /// "off".
  kFlutterSemanticsFlagIsToggled = 1 << 17,
  /// Whether the platform can scroll the semantics node when the user attempts
  /// to move the accessibility focus to an offscreen child.
  ///
  /// For example, a `ListView` widget has implicit scrolling so that users can
  /// easily move the accessibility focus to the next set of children. A
  /// `PageView` widget does not have implicit scrolling, so that users don't
  /// navigate to the next page when reaching the end of the current one.
  kFlutterSemanticsFlagHasImplicitScrolling = 1 << 18,
  /// Whether the semantic node is read only.
  ///
  /// Only applicable when kFlutterSemanticsFlagIsTextField flag is on.
  kFlutterSemanticsFlagIsReadOnly = 1 << 20,
} FlutterSemanticsFlag;

typedef enum {
  /// Text has unknown text direction.
  kFlutterTextDirectionUnknown = 0,
  /// Text is read from right to left.
  kFlutterTextDirectionRTL = 1,
  /// Text is read from left to right.
  kFlutterTextDirectionLTR = 2,
} FlutterTextDirection;

typedef struct _FlutterEngine* FLUTTER_API_SYMBOL(FlutterEngine);

typedef struct {
  /// horizontal scale factor
  double scaleX;
  /// horizontal skew factor
  double skewX;
  /// horizontal translation
  double transX;
  /// vertical skew factor
  double skewY;
  /// vertical scale factor
  double scaleY;
  /// vertical translation
  double transY;
  /// input x-axis perspective factor
  double pers0;
  /// input y-axis perspective factor
  double pers1;
  /// perspective scale factor
  double pers2;
} FlutterTransformation;

typedef void (*VoidCallback)(void* /* user data */);

typedef enum {
  /// Specifies an OpenGL texture target type. Textures are specified using
  /// the FlutterOpenGLTexture struct.
  kFlutterOpenGLTargetTypeTexture,
  /// Specifies an OpenGL frame-buffer target type. Framebuffers are specified
  /// using the FlutterOpenGLFramebuffer struct.
  kFlutterOpenGLTargetTypeFramebuffer,
} FlutterOpenGLTargetType;

typedef struct {
  /// Target texture of the active texture unit (example GL_TEXTURE_2D).
  uint32_t target;
  /// The name of the texture.
  uint32_t name;
  /// The texture format (example GL_RGBA8).
  uint32_t format;
  /// User data to be returned on the invocation of the destruction callback.
  void* user_data;
  /// Callback invoked (on an engine managed thread) that asks the embedder to
  /// collect the texture.
  VoidCallback destruction_callback;
} FlutterOpenGLTexture;

typedef struct {
  /// The target of the color attachment of the frame-buffer. For example,
  /// GL_TEXTURE_2D or GL_RENDERBUFFER. In case of ambiguity when dealing with
  /// Window bound frame-buffers, 0 may be used.
  uint32_t target;

  /// The name of the framebuffer.
  uint32_t name;

  /// User data to be returned on the invocation of the destruction callback.
  void* user_data;

  /// Callback invoked (on an engine managed thread) that asks the embedder to
  /// collect the framebuffer.
  VoidCallback destruction_callback;
} FlutterOpenGLFramebuffer;

typedef bool (*BoolCallback)(void* /* user data */);
typedef FlutterTransformation (*TransformationCallback)(void* /* user data */);
typedef uint32_t (*UIntCallback)(void* /* user data */);
typedef bool (*SoftwareSurfacePresentCallback)(void* /* user data */,
                                               const void* /* allocation */,
                                               size_t /* row bytes */,
                                               size_t /* height */);
typedef void* (*ProcResolver)(void* /* user data */, const char* /* name */);
typedef bool (*TextureFrameCallback)(void* /* user data */,
                                     int64_t /* texture identifier */,
                                     size_t /* width */,
                                     size_t /* height */,
                                     FlutterOpenGLTexture* /* texture out */);
typedef void (*VsyncCallback)(void* /* user data */, intptr_t /* baton */);

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterOpenGLRendererConfig).
  size_t struct_size;
  BoolCallback make_current;
  BoolCallback clear_current;
  BoolCallback present;
  UIntCallback fbo_callback;
  /// This is an optional callback. Flutter will ask the emebdder to create a GL
  /// context current on a background thread. If the embedder is able to do so,
  /// Flutter will assume that this context is in the same sharegroup as the
  /// main rendering context and use this context for asynchronous texture
  /// uploads. Though optional, it is recommended that all embedders set this
  /// callback as it will lead to better performance in texture handling.
  BoolCallback make_resource_current;
  /// By default, the renderer config assumes that the FBO does not change for
  /// the duration of the engine run. If this argument is true, the
  /// engine will ask the embedder for an updated FBO target (via an
  /// fbo_callback invocation) after a present call.
  bool fbo_reset_after_present;
  /// The transformation to apply to the render target before any rendering
  /// operations. This callback is optional.
  TransformationCallback surface_transformation;
  ProcResolver gl_proc_resolver;
  /// When the embedder specifies that a texture has a frame available, the
  /// engine will call this method (on an internal engine managed thread) so
  /// that external texture details can be supplied to the engine for subsequent
  /// composition.
  TextureFrameCallback gl_external_texture_frame_callback;
} FlutterOpenGLRendererConfig;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterSoftwareRendererConfig).
  size_t struct_size;
  /// The callback presented to the embedder to present a fully populated buffer
  /// to the user. The pixel format of the buffer is the native 32-bit RGBA
  /// format. The buffer is owned by the Flutter engine and must be copied in
  /// this callback if needed.
  SoftwareSurfacePresentCallback surface_present_callback;
} FlutterSoftwareRendererConfig;

typedef struct {
  FlutterRendererType type;
  union {
    FlutterOpenGLRendererConfig open_gl;
    FlutterSoftwareRendererConfig software;
  };
} FlutterRendererConfig;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterWindowMetricsEvent).
  size_t struct_size;
  /// Physical width of the window.
  size_t width;
  /// Physical height of the window.
  size_t height;
  /// Scale factor for the physical screen.
  double pixel_ratio;
} FlutterWindowMetricsEvent;

/// The phase of the pointer event.
typedef enum {
  kCancel,
  /// The pointer, which must have been down (see kDown), is now up.
  ///
  /// For touch, this means that the pointer is no longer in contact with the
  /// screen. For a mouse, it means the last button was released. Note that if
  /// any other buttons are still pressed when one button is released, that
  /// should be sent as a kMove rather than a kUp.
  kUp,
  /// The pointer, which must have been been up, is now down.
  ///
  /// For touch, this means that the pointer has come into contact with the
  /// screen. For a mouse, it means a button is now pressed. Note that if any
  /// other buttons are already pressed when a new button is pressed, that
  /// should be sent as a kMove rather than a kDown.
  kDown,
  /// The pointer moved while down.
  ///
  /// This is also used for changes in button state that don't cause a kDown or
  /// kUp, such as releasing one of two pressed buttons.
  kMove,
  /// The pointer is now sending input to Flutter. For instance, a mouse has
  /// entered the area where the Flutter content is displayed.
  ///
  /// A pointer should always be added before sending any other events.
  kAdd,
  /// The pointer is no longer sending input to Flutter. For instance, a mouse
  /// has left the area where the Flutter content is displayed.
  ///
  /// A removed pointer should no longer send events until sending a new kAdd.
  kRemove,
  /// The pointer moved while up.
  kHover,
} FlutterPointerPhase;

/// The device type that created a pointer event.
typedef enum {
  kFlutterPointerDeviceKindMouse = 1,
  kFlutterPointerDeviceKindTouch,
} FlutterPointerDeviceKind;

/// Flags for the `buttons` field of `FlutterPointerEvent` when `device_kind`
/// is `kFlutterPointerDeviceKindMouse`.
typedef enum {
  kFlutterPointerButtonMousePrimary = 1 << 0,
  kFlutterPointerButtonMouseSecondary = 1 << 1,
  kFlutterPointerButtonMouseMiddle = 1 << 2,
  kFlutterPointerButtonMouseBack = 1 << 3,
  kFlutterPointerButtonMouseForward = 1 << 4,
  /// If a mouse has more than five buttons, send higher bit shifted values
  /// corresponding to the button number: 1 << 5 for the 6th, etc.
} FlutterPointerMouseButtons;

/// The type of a pointer signal.
typedef enum {
  kFlutterPointerSignalKindNone,
  kFlutterPointerSignalKindScroll,
} FlutterPointerSignalKind;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterPointerEvent).
  size_t struct_size;
  FlutterPointerPhase phase;
  /// @attention     The timestamp must be specified in microseconds.
  size_t timestamp;
  double x;
  double y;
  /// An optional device identifier. If this is not specified, it is assumed
  /// that the embedder has no multi-touch capability.
  int32_t device;
  FlutterPointerSignalKind signal_kind;
  double scroll_delta_x;
  double scroll_delta_y;
  /// The type of the device generating this event.
  /// Backwards compatibility note: If this is not set, the device will be
  /// treated as a mouse, with the primary button set for `kDown` and `kMove`.
  /// If set explicitly to `kFlutterPointerDeviceKindMouse`, you must set the
  /// correct buttons.
  FlutterPointerDeviceKind device_kind;
  /// The buttons currently pressed, if any.
  int64_t buttons;
} FlutterPointerEvent;

struct _FlutterPlatformMessageResponseHandle;
typedef struct _FlutterPlatformMessageResponseHandle
    FlutterPlatformMessageResponseHandle;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterPlatformMessage).
  size_t struct_size;
  const char* channel;
  const uint8_t* message;
  size_t message_size;
  /// The response handle on which to invoke
  /// `FlutterEngineSendPlatformMessageResponse` when the response is ready.
  /// `FlutterEngineSendPlatformMessageResponse` must be called for all messages
  /// received by the embedder. Failure to call
  /// `FlutterEngineSendPlatformMessageResponse` will cause a memory leak. It is
  /// not safe to send multiple responses on a single response object.
  const FlutterPlatformMessageResponseHandle* response_handle;
} FlutterPlatformMessage;

typedef void (*FlutterPlatformMessageCallback)(
    const FlutterPlatformMessage* /* message*/,
    void* /* user data */);

typedef void (*FlutterDataCallback)(const uint8_t* /* data */,
                                    size_t /* size */,
                                    void* /* user data */);

typedef struct {
  double left;
  double top;
  double right;
  double bottom;
} FlutterRect;

/// `FlutterSemanticsNode` ID used as a sentinel to signal the end of a batch of
/// semantics node updates.
FLUTTER_EXPORT
extern const int32_t kFlutterSemanticsNodeIdBatchEnd;

/// A node that represents some semantic data.
///
/// The semantics tree is maintained during the semantics phase of the pipeline
/// (i.e., during PipelineOwner.flushSemantics), which happens after
/// compositing. Updates are then pushed to embedders via the registered
/// `FlutterUpdateSemanticsNodeCallback`.
typedef struct {
  /// The size of this struct. Must be sizeof(FlutterSemanticsNode).
  size_t struct_size;
  /// The unique identifier for this node.
  int32_t id;
  /// The set of semantics flags associated with this node.
  FlutterSemanticsFlag flags;
  /// The set of semantics actions applicable to this node.
  FlutterSemanticsAction actions;
  /// The position at which the text selection originates.
  int32_t text_selection_base;
  /// The position at which the text selection terminates.
  int32_t text_selection_extent;
  /// The total number of scrollable children that contribute to semantics.
  int32_t scroll_child_count;
  /// The index of the first visible semantic child of a scroll node.
  int32_t scroll_index;
  /// The current scrolling position in logical pixels if the node is
  /// scrollable.
  double scroll_position;
  /// The maximum in-range value for `scrollPosition` if the node is scrollable.
  double scroll_extent_max;
  /// The minimum in-range value for `scrollPosition` if the node is scrollable.
  double scroll_extent_min;
  /// The elevation along the z-axis at which the rect of this semantics node is
  /// located above its parent.
  double elevation;
  /// Describes how much space the semantics node takes up along the z-axis.
  double thickness;
  /// A textual description of the node.
  const char* label;
  /// A brief description of the result of performing an action on the node.
  const char* hint;
  /// A textual description of the current value of the node.
  const char* value;
  /// A value that `value` will have after a kFlutterSemanticsActionIncrease`
  /// action has been performed.
  const char* increased_value;
  /// A value that `value` will have after a kFlutterSemanticsActionDecrease`
  /// action has been performed.
  const char* decreased_value;
  /// The reading direction for `label`, `value`, `hint`, `increasedValue`, and
  /// `decreasedValue`.
  FlutterTextDirection text_direction;
  /// The bounding box for this node in its coordinate system.
  FlutterRect rect;
  /// The transform from this node's coordinate system to its parent's
  /// coordinate system.
  FlutterTransformation transform;
  /// The number of children this node has.
  size_t child_count;
  /// Array of child node IDs in traversal order. Has length `child_count`.
  const int32_t* children_in_traversal_order;
  /// Array of child node IDs in hit test order. Has length `child_count`.
  const int32_t* children_in_hit_test_order;
  /// The number of custom accessibility action associated with this node.
  size_t custom_accessibility_actions_count;
  /// Array of `FlutterSemanticsCustomAction` IDs associated with this node.
  /// Has length `custom_accessibility_actions_count`.
  const int32_t* custom_accessibility_actions;
} FlutterSemanticsNode;

/// `FlutterSemanticsCustomAction` ID used as a sentinel to signal the end of a
/// batch of semantics custom action updates.
FLUTTER_EXPORT
extern const int32_t kFlutterSemanticsCustomActionIdBatchEnd;

/// A custom semantics action, or action override.
///
/// Custom actions can be registered by applications in order to provide
/// semantic actions other than the standard actions available through the
/// `FlutterSemanticsAction` enum.
///
/// Action overrides are custom actions that the application developer requests
/// to be used in place of the standard actions in the `FlutterSemanticsAction`
/// enum.
typedef struct {
  /// The size of the struct. Must be sizeof(FlutterSemanticsCustomAction).
  size_t struct_size;
  /// The unique custom action or action override ID.
  int32_t id;
  /// For overridden standard actions, corresponds to the
  /// `FlutterSemanticsAction` to override.
  FlutterSemanticsAction override_action;
  /// The user-readable name of this custom semantics action.
  const char* label;
  /// The hint description of this custom semantics action.
  const char* hint;
} FlutterSemanticsCustomAction;

typedef void (*FlutterUpdateSemanticsNodeCallback)(
    const FlutterSemanticsNode* /* semantics node */,
    void* /* user data */);

typedef void (*FlutterUpdateSemanticsCustomActionCallback)(
    const FlutterSemanticsCustomAction* /* semantics custom action */,
    void* /* user data */);

typedef struct _FlutterTaskRunner* FlutterTaskRunner;

typedef struct {
  FlutterTaskRunner runner;
  uint64_t task;
} FlutterTask;

typedef void (*FlutterTaskRunnerPostTaskCallback)(
    FlutterTask /* task */,
    uint64_t /* target time nanos */,
    void* /* user data */);

/// An interface used by the Flutter engine to execute tasks at the target time
/// on a specified thread. There should be a 1-1 relationship between a thread
/// and a task runner. It is undefined behavior to run a task on a thread that
/// is not associated with its task runner.
typedef struct {
  /// The size of this struct. Must be sizeof(FlutterTaskRunnerDescription).
  size_t struct_size;
  void* user_data;
  /// May be called from any thread. Should return true if tasks posted on the
  /// calling thread will be run on that same thread.
  ///
  /// @attention     This field is required.
  BoolCallback runs_task_on_current_thread_callback;
  /// May be called from any thread. The given task should be executed by the
  /// embedder on the thread associated with that task runner by calling
  /// `FlutterEngineRunTask` at the given target time. The system monotonic
  /// clock should be used for the target time. The target time is the absolute
  /// time from epoch (NOT a delta) at which the task must be returned back to
  /// the engine on the correct thread. If the embedder needs to calculate a
  /// delta, `FlutterEngineGetCurrentTime` may be called and the difference used
  /// as the delta.
  ///
  /// @attention     This field is required.
  FlutterTaskRunnerPostTaskCallback post_task_callback;
} FlutterTaskRunnerDescription;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterCustomTaskRunners).
  size_t struct_size;
  /// Specify the task runner for the thread on which the `FlutterEngineRun`
  /// call is made.
  const FlutterTaskRunnerDescription* platform_task_runner;
} FlutterCustomTaskRunners;

typedef struct {
  /// The type of the OpenGL backing store. Currently, it can either be a
  /// texture or a framebuffer.
  FlutterOpenGLTargetType type;
  union {
    /// A texture for Flutter to render into.
    FlutterOpenGLTexture texture;
    /// A framebuffer for Flutter to render into. The embedder must ensure that
    /// the framebuffer is complete.
    FlutterOpenGLFramebuffer framebuffer;
  };
} FlutterOpenGLBackingStore;

typedef struct {
  /// A pointer to the raw bytes of the allocation described by this software
  /// backing store.
  const void* allocation;
  /// The number of bytes in a single row of the allocation.
  size_t row_bytes;
  /// The number of rows in the allocation.
  size_t height;
  /// A baton that is not interpreted by the engine in any way. It will be given
  /// back to the embedder in the destruction callback below. Embedder resources
  /// may be associated with this baton.
  void* user_data;
  /// The callback invoked by the engine when it no longer needs this backing
  /// store.
  VoidCallback destruction_callback;
} FlutterSoftwareBackingStore;

/// The identifier of the platform view. This identifier is specified by the
/// application when a platform view is added to the scene via the
/// `SceneBuilder.addPlatformView` call.
typedef int64_t FlutterPlatformViewIdentifier;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterPlatformView).
  size_t struct_size;
  /// The identifier of this platform view. This identifier is specified by the
  /// application when a platform view is added to the scene via the
  /// `SceneBuilder.addPlatformView` call.
  FlutterPlatformViewIdentifier identifier;
} FlutterPlatformView;

typedef enum {
  /// Specifies an OpenGL backing store. Can either be an OpenGL texture or
  /// framebuffer.
  kFlutterBackingStoreTypeOpenGL,
  /// Specified an software allocation for Flutter to render into using the CPU.
  kFlutterBackingStoreTypeSoftware,
} FlutterBackingStoreType;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterBackingStore).
  size_t struct_size;
  /// A baton that is not interpreted by the engine in any way. The embedder may
  /// use this to associate resources that are tied to the lifecycle of the
  /// `FlutterBackingStore`.
  void* user_data;
  /// Specifies the type of backing store.
  FlutterBackingStoreType type;
  /// Indicates if this backing store was updated since the last time it was
  /// associated with a presented layer.
  bool did_update;
  union {
    /// The description of the OpenGL backing store.
    FlutterOpenGLBackingStore open_gl;
    /// The description of the software backing store.
    FlutterSoftwareBackingStore software;
  };
} FlutterBackingStore;

typedef struct {
  double x;
  double y;
} FlutterPoint;

typedef struct {
  double width;
  double height;
} FlutterSize;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterBackingStoreConfig).
  size_t struct_size;
  /// The size of the render target the engine expects to render into.
  FlutterSize size;
} FlutterBackingStoreConfig;

typedef enum {
  /// Indicates that the contents of this layer are rendered by Flutter into a
  /// backing store.
  kFlutterLayerContentTypeBackingStore,
  /// Indicates that the contents of this layer are determined by the embedder.
  kFlutterLayerContentTypePlatformView,
} FlutterLayerContentType;

typedef struct {
  /// This size of this struct. Must be sizeof(FlutterLayer).
  size_t struct_size;
  /// Each layer displays contents in one way or another. The type indicates
  /// whether those contents are specified by Flutter or the embedder.
  FlutterLayerContentType type;
  union {
    /// Indicates that the contents of this layer are rendered by Flutter into a
    /// backing store.
    const FlutterBackingStore* backing_store;
    /// Indicates that the contents of this layer are determined by the
    /// embedder.
    const FlutterPlatformView* platform_view;
  };
  /// The offset of this layer (in physical pixels) relative to the top left of
  /// the root surface used by the engine.
  FlutterPoint offset;
  /// The size of the layer (in physical pixels).
  FlutterSize size;
} FlutterLayer;

typedef bool (*FlutterBackingStoreCreateCallback)(
    const FlutterBackingStoreConfig* config,
    FlutterBackingStore* backing_store_out,
    void* user_data);

typedef bool (*FlutterBackingStoreCollectCallback)(
    const FlutterBackingStore* renderer,
    void* user_data);

typedef bool (*FlutterLayersPresentCallback)(const FlutterLayer** layers,
                                             size_t layers_count,
                                             void* user_data);

typedef struct {
  /// This size of this struct. Must be sizeof(FlutterCompositor).
  size_t struct_size;
  /// A baton that in not interpreted by the engine in any way. If it passed
  /// back to the embedder in `FlutterCompositor.create_backing_store_callback`,
  /// `FlutterCompositor.collect_backing_store_callback` and
  /// `FlutterCompositor.present_layers_callback`
  void* user_data;
  /// A callback invoked by the engine to obtain a backing store for a specific
  /// `FlutterLayer`.
  ///
  /// On ABI stability: Callers must take care to restrict access within
  /// `FlutterBackingStore::struct_size` when specifying a new backing store to
  /// the engine. This only matters if the embedder expects to be used with
  /// engines older than the version whose headers it used during compilation.
  FlutterBackingStoreCreateCallback create_backing_store_callback;
  /// A callback invoked by the engine to release the backing store. The
  /// embedder may collect any resources associated with the backing store.
  FlutterBackingStoreCollectCallback collect_backing_store_callback;
  /// Callback invoked by the engine to composite the contents of each layer
  /// onto the screen.
  FlutterLayersPresentCallback present_layers_callback;
} FlutterCompositor;

typedef struct {
  /// The size of this struct. Must be sizeof(FlutterProjectArgs).
  size_t struct_size;
  /// The path to the Flutter assets directory containing project assets. The
  /// string can be collected after the call to `FlutterEngineRun` returns. The
  /// string must be NULL terminated.
  const char* assets_path;
  /// The path to the Dart file containing the `main` entry point.
  /// The string can be collected after the call to `FlutterEngineRun` returns.
  /// The string must be NULL terminated.
  ///
  /// @deprecated     As of Dart 2, running from Dart source is no longer
  ///                 supported. Dart code should now be compiled to kernel form
  ///                 and will be loaded by from `kernel_blob.bin` in the assets
  ///                 directory. This struct member is retained for ABI
  ///                 stability.
  const char* main_path__unused__;
  /// The path to the `.packages` file for the project. The string can be
  /// collected after the call to `FlutterEngineRun` returns. The string must be
  /// NULL terminated.
  ///
  /// @deprecated    As of Dart 2, running from Dart source is no longer
  ///                supported. Dart code should now be compiled to kernel form
  ///                and will be loaded by from `kernel_blob.bin` in the assets
  ///                directory. This struct member is retained for ABI
  ///                stability.
  const char* packages_path__unused__;
  /// The path to the `icudtl.dat` file for the project. The string can be
  /// collected after the call to `FlutterEngineRun` returns. The string must
  /// be NULL terminated.
  const char* icu_data_path;
  /// The command line argument count used to initialize the project.
  int command_line_argc;
  /// The command line arguments used to initialize the project. The strings can
  /// be collected after the call to `FlutterEngineRun` returns. The strings
  /// must be `NULL` terminated.
  ///
  /// @attention     The first item in the command line (if specified at all) is
  ///                interpreted as the executable name. So if an engine flag
  ///                needs to be passed into the same, it needs to not be the
  ///                very first item in the list.
  ///
  /// The set of engine flags are only meant to control
  /// unstable features in the engine. Deployed applications should not pass any
  /// command line arguments at all as they may affect engine stability at
  /// runtime in the presence of un-sanitized input. The list of currently
  /// recognized engine flags and their descriptions can be retrieved from the
  /// `switches.h` engine source file.
  const char* const* command_line_argv;
  /// The callback invoked by the engine in order to give the embedder the
  /// chance to respond to platform messages from the Dart application. The
  /// callback will be invoked on the thread on which the `FlutterEngineRun`
  /// call is made.
  FlutterPlatformMessageCallback platform_message_callback;
  /// The VM snapshot data buffer used in AOT operation. This buffer must be
  /// mapped in as read-only. For more information refer to the documentation on
  /// the Wiki at
  /// https://github.com/flutter/flutter/wiki/Flutter-engine-operation-in-AOT-Mode
  const uint8_t* vm_snapshot_data;
  /// The size of the VM snapshot data buffer.  If vm_snapshot_data is a symbol
  /// reference, 0 may be passed here.
  size_t vm_snapshot_data_size;
  /// The VM snapshot instructions buffer used in AOT operation. This buffer
  /// must be mapped in as read-execute. For more information refer to the
  /// documentation on the Wiki at
  /// https://github.com/flutter/flutter/wiki/Flutter-engine-operation-in-AOT-Mode
  const uint8_t* vm_snapshot_instructions;
  /// The size of the VM snapshot instructions buffer. If
  /// vm_snapshot_instructions is a symbol reference, 0 may be passed here.
  size_t vm_snapshot_instructions_size;
  /// The isolate snapshot data buffer used in AOT operation. This buffer must
  /// be mapped in as read-only. For more information refer to the documentation
  /// on the Wiki at
  /// https://github.com/flutter/flutter/wiki/Flutter-engine-operation-in-AOT-Mode
  const uint8_t* isolate_snapshot_data;
  /// The size of the isolate snapshot data buffer.  If isolate_snapshot_data is
  /// a symbol reference, 0 may be passed here.
  size_t isolate_snapshot_data_size;
  /// The isolate snapshot instructions buffer used in AOT operation. This
  /// buffer must be mapped in as read-execute. For more information refer to
  /// the documentation on the Wiki at
  /// https://github.com/flutter/flutter/wiki/Flutter-engine-operation-in-AOT-Mode
  const uint8_t* isolate_snapshot_instructions;
  /// The size of the isolate snapshot instructions buffer. If
  /// isolate_snapshot_instructions is a symbol reference, 0 may be passed here.
  size_t isolate_snapshot_instructions_size;
  /// The callback invoked by the engine in root isolate scope. Called
  /// immediately after the root isolate has been created and marked runnable.
  VoidCallback root_isolate_create_callback;
  /// The callback invoked by the engine in order to give the embedder the
  /// chance to respond to semantics node updates from the Dart application.
  /// Semantics node updates are sent in batches terminated by a 'batch end'
  /// callback that is passed a sentinel `FlutterSemanticsNode` whose `id` field
  /// has the value `kFlutterSemanticsNodeIdBatchEnd`.
  ///
  /// The callback will be invoked on the thread on which the `FlutterEngineRun`
  /// call is made.
  FlutterUpdateSemanticsNodeCallback update_semantics_node_callback;
  /// The callback invoked by the engine in order to give the embedder the
  /// chance to respond to updates to semantics custom actions from the Dart
  /// application.  Custom action updates are sent in batches terminated by a
  /// 'batch end' callback that is passed a sentinel
  /// `FlutterSemanticsCustomAction` whose `id` field has the value
  /// `kFlutterSemanticsCustomActionIdBatchEnd`.
  ///
  /// The callback will be invoked on the thread on which the `FlutterEngineRun`
  /// call is made.
  FlutterUpdateSemanticsCustomActionCallback
      update_semantics_custom_action_callback;
  /// Path to a directory used to store data that is cached across runs of a
  /// Flutter application (such as compiled shader programs used by Skia).
  /// This is optional.  The string must be NULL terminated.
  ///
  // This is different from the cache-path-dir argument defined in switches.h,
  // which is used in `flutter::Settings` as `temp_directory_path`.
  const char* persistent_cache_path;

  /// If true, we'll only read the existing cache, but not write new ones.
  bool is_persistent_cache_read_only;

  /// A callback that gets invoked by the engine when it attempts to wait for a
  /// platform vsync event. The engine will give the platform a baton that needs
  /// to be returned back to the engine via `FlutterEngineOnVsync`. All batons
  /// must be retured to the engine before initializing a
  /// `FlutterEngineShutdown`. Not doing the same will result in a memory leak.
  /// While the call to `FlutterEngineOnVsync` must occur on the thread that
  /// made the call to `FlutterEngineRun`, the engine will make this callback on
  /// an internal engine-managed thread. If the components accessed on the
  /// embedder are not thread safe, the appropriate re-threading must be done.
  VsyncCallback vsync_callback;

  /// The name of a custom Dart entrypoint. This is optional and specifying a
  /// null or empty entrypoint makes the engine look for a method named "main"
  /// in the root library of the application.
  ///
  /// Care must be taken to ensure that the custom entrypoint is not tree-shaken
  /// away. Usually, this is done using the `@pragma('vm:entry-point')`
  /// decoration.
  const char* custom_dart_entrypoint;

  /// Typically the Flutter engine create and manages its internal threads. This
  /// optional argument allows for the specification of task runner interfaces
  /// to event loops managed by the embedder on threads it creates.
  const FlutterCustomTaskRunners* custom_task_runners;

  /// All `FlutterEngine` instances in the process share the same Dart VM. When
  /// the first engine is launched, it starts the Dart VM as well. It used to be
  /// the case that it was not possible to shutdown the Dart VM cleanly and
  /// start it back up in the process in a safe manner. This issue has since
  /// been patched. Unfortunately, applications already began to make use of the
  /// fact that shutting down the Flutter engine instance left a running VM in
  /// the process. Since a Flutter engine could be launched on any thread,
  /// applications would "warm up" the VM on another thread by launching
  /// an engine with no isolates and then shutting it down immediately. The main
  /// Flutter application could then be started on the main thread without
  /// having to incur the Dart VM startup costs at that time. With the new
  /// behavior, this "optimization" immediately becomes massive performance
  /// pessimization as the VM would be started up in the "warm up" phase, shut
  /// down there and then started again on the main thread. Changing this
  /// behavior was deemed to be an unacceptable breaking change. Embedders that
  /// wish to shutdown the Dart VM when the last engine is terminated in the
  /// process should opt into this behavior by setting this flag to true.
  bool shutdown_dart_vm_when_done;

  /// Typically, Flutter renders the layer hierarchy into a single root surface.
  /// However, when embedders need to interleave their own contents within the
  /// Flutter layer hierarchy, their applications can push platform views within
  /// the Flutter scene. This is done using the `SceneBuilder.addPlatformView`
  /// call. When this happens, the Flutter rasterizer divides the effective view
  /// hierarchy into multiple layers. Each layer gets its own backing store and
  /// Flutter renders into the same. Once the layers contents have been
  /// fulfilled, the embedder is asked to composite these layers on-screen. At
  /// this point, it can interleave its own contents within the effective
  /// hierarchy. The interface for the specification of these layer backing
  /// stores and the hooks to listen for the composition of layers on-screen can
  /// be controlled using this field. This field is completely optional. In its
  /// absence, platforms views in the scene are ignored and Flutter renders to
  /// the root surface as normal.
  const FlutterCompositor* compositor;
} FlutterProjectArgs;

FLUTTER_EXPORT
FlutterEngineResult FlutterEngineRun(size_t version,
                                     const FlutterRendererConfig* config,
                                     const FlutterProjectArgs* args,
                                     void* user_data,
                                     FLUTTER_API_SYMBOL(FlutterEngine) *
                                         engine_out);

FLUTTER_EXPORT
FlutterEngineResult FlutterEngineShutdown(FLUTTER_API_SYMBOL(FlutterEngine)
                                              engine);

FLUTTER_EXPORT
FlutterEngineResult FlutterEngineSendWindowMetricsEvent(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    const FlutterWindowMetricsEvent* event);

FLUTTER_EXPORT
FlutterEngineResult FlutterEngineSendPointerEvent(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    const FlutterPointerEvent* events,
    size_t events_count);

FLUTTER_EXPORT
FlutterEngineResult FlutterEngineSendPlatformMessage(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    const FlutterPlatformMessage* message);

//------------------------------------------------------------------------------
/// @brief     Creates a platform message response handle that allows the
///            embedder to set a native callback for a response to a message.
///            This handle may be set on the `response_handle` field of any
///            `FlutterPlatformMessage` sent to the engine.
///
///            The handle must be collected via a call to
///            `FlutterPlatformMessageReleaseResponseHandle`. This may be done
///            immediately after a call to `FlutterEngineSendPlatformMessage`
///            with a platform message whose response handle contains the handle
///            created using this call. In case a handle is created but never
///            sent in a message, the release call must still be made. Not
///            calling release on the handle results in a small memory leak.
///
///            The user data baton passed to the data callback is the one
///            specified in this call as the third argument.
///
/// @see       FlutterPlatformMessageReleaseResponseHandle()
///
/// @param[in]  engine         A running engine instance.
/// @param[in]  data_callback  The callback invoked by the engine when the
///                            Flutter application send a response on the
///                            handle.
/// @param[in]  user_data      The user data associated with the data callback.
/// @param[out] response_out   The response handle created when this call is
///                            successful.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterPlatformMessageCreateResponseHandle(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    FlutterDataCallback data_callback,
    void* user_data,
    FlutterPlatformMessageResponseHandle** response_out);

//------------------------------------------------------------------------------
/// @brief      Collects the handle created using
///             `FlutterPlatformMessageCreateResponseHandle`.
///
/// @see        FlutterPlatformMessageCreateResponseHandle()
///
/// @param[in]  engine     A running engine instance.
/// @param[in]  response   The platform message response handle to collect.
///                        These handles are created using
///                        `FlutterPlatformMessageCreateResponseHandle()`.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterPlatformMessageReleaseResponseHandle(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    FlutterPlatformMessageResponseHandle* response);

//------------------------------------------------------------------------------
/// @brief      Send a response from the native side to a platform message from
///             the Dart Flutter application.
///
/// @param[in]  engine       The running engine instance.
/// @param[in]  handle       The platform message response handle.
/// @param[in]  data         The data to associate with the platform message
///                          response.
/// @param[in]  data_length  The length of the platform message response data.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineSendPlatformMessageResponse(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    const FlutterPlatformMessageResponseHandle* handle,
    const uint8_t* data,
    size_t data_length);

//------------------------------------------------------------------------------
/// @brief      This API is only meant to be used by platforms that need to
///             flush tasks on a message loop not controlled by the Flutter
///             engine.
///
/// @deprecated This API will be deprecated and is not part of the stable API.
///             Please use the custom task runners API by setting an
///             appropriate `FlutterProjectArgs::custom_task_runners`
///             interface. This will yield better performance and the
///             interface is stable.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult __FlutterEngineFlushPendingTasksNow();

//------------------------------------------------------------------------------
/// @brief      Register an external texture with a unique (per engine)
///             identifier. Only rendering backends that support external
///             textures accept external texture registrations. After the
///             external texture is registered, the application can mark that a
///             frame is available by calling
///             `FlutterEngineMarkExternalTextureFrameAvailable`.
///
/// @see        FlutterEngineUnregisterExternalTexture()
/// @see        FlutterEngineMarkExternalTextureFrameAvailable()
///
/// @param[in]  engine              A running engine instance.
/// @param[in]  texture_identifier  The identifier of the texture to register
///                                 with the engine. The embedder may supply new
///                                 frames to this texture using the same
///                                 identifier.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineRegisterExternalTexture(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    int64_t texture_identifier);

//------------------------------------------------------------------------------
/// @brief      Unregister a previous texture registration.
///
/// @see        FlutterEngineRegisterExternalTexture()
/// @see        FlutterEngineMarkExternalTextureFrameAvailable()
///
/// @param[in]  engine              A running engine instance.
/// @param[in]  texture_identifier  The identifier of the texture for which new
///                                 frame will not be available.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineUnregisterExternalTexture(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    int64_t texture_identifier);

//------------------------------------------------------------------------------
/// @brief      Mark that a new texture frame is available for a given texture
///             identifier.
///
/// @see        FlutterEngineRegisterExternalTexture()
/// @see        FlutterEngineUnregisterExternalTexture()
///
/// @param[in]  engine              A running engine instance.
/// @param[in]  texture_identifier  The identifier of the texture whose frame
///                                 has been updated.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineMarkExternalTextureFrameAvailable(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    int64_t texture_identifier);

//------------------------------------------------------------------------------
/// @brief      Enable or disable accessibility semantics.
///
/// @param[in]  engine     A running engine instance.
/// @param[in]  enabled    When enabled, changes to the semantic contents of the
///                        window are sent via the
///                        `FlutterUpdateSemanticsNodeCallback` registered to
///                        `update_semantics_node_callback` in
///                        `FlutterProjectArgs`.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineUpdateSemanticsEnabled(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    bool enabled);

//------------------------------------------------------------------------------
/// @brief      Sets additional accessibility features.
///
/// @param[in]  engine     A running engine instance
/// @param[in]  features   The accessibility features to set.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineUpdateAccessibilityFeatures(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    FlutterAccessibilityFeature features);

//------------------------------------------------------------------------------
/// @brief      Dispatch a semantics action to the specified semantics node.
///
/// @param[in]  engine       A running engine instance.
/// @param[in]  identifier   The semantics action identifier.
/// @param[in]  action       The semantics action.
/// @param[in]  data         Data associated with the action.
/// @param[in]  data_length  The data length.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineDispatchSemanticsAction(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    uint64_t id,
    FlutterSemanticsAction action,
    const uint8_t* data,
    size_t data_length);

//------------------------------------------------------------------------------
/// @brief      Notify the engine that a vsync event occurred. A baton passed to
///             the platform via the vsync callback must be returned. This call
///             must be made on the thread on which the call to
///             `FlutterEngineRun` was made.
///
/// @see        FlutterEngineGetCurrentTime()
///
/// @attention  That frame timepoints are in nanoseconds.
///
/// @attention  The system monotonic clock is used as the timebase.
///
/// @param[in]  engine.                  A running engine instance.
/// @param[in]  baton                    The baton supplied by the engine.
/// @param[in]  frame_start_time_nanos   The point at which the vsync event
///                                      occurred or will occur. If the time
///                                      point is in the future, the engine will
///                                      wait till that point to begin its frame
///                                      workload.
/// @param[in]  frame_target_time_nanos  The point at which the embedder
///                                      anticipates the next vsync to occur.
///                                      This is a hint the engine uses to
///                                      schedule Dart VM garbage collection in
///                                      periods in which the various threads
///                                      are most likely to be idle. For
///                                      example, for a 60Hz display, embedders
///                                      should add 16.6 * 1e6 to the frame time
///                                      field.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineOnVsync(FLUTTER_API_SYMBOL(FlutterEngine)
                                             engine,
                                         intptr_t baton,
                                         uint64_t frame_start_time_nanos,
                                         uint64_t frame_target_time_nanos);

//------------------------------------------------------------------------------
/// @brief      A profiling utility. Logs a trace duration begin event to the
///             timeline. If the timeline is unavailable or disabled, this has
///             no effect. Must be balanced with an duration end event (via
///             `FlutterEngineTraceEventDurationEnd`) with the same name on the
///             same thread. Can be called on any thread. Strings passed into
///             the function will NOT be copied when added to the timeline. Only
///             string literals may be passed in.
///
/// @param[in]  name  The name of the trace event.
///
FLUTTER_EXPORT
void FlutterEngineTraceEventDurationBegin(const char* name);

//-----------------------------------------------------------------------------
/// @brief      A profiling utility. Logs a trace duration end event to the
///             timeline. If the timeline is unavailable or disabled, this has
///             no effect. This call must be preceded by a trace duration begin
///             call (via `FlutterEngineTraceEventDurationBegin`) with the same
///             name on the same thread. Can be called on any thread. Strings
///             passed into the function will NOT be copied when added to the
///             timeline. Only string literals may be passed in.
///
/// @param[in]  name  The name of the trace event.
///
FLUTTER_EXPORT
void FlutterEngineTraceEventDurationEnd(const char* name);

//-----------------------------------------------------------------------------
/// @brief      A profiling utility. Logs a trace duration instant event to the
///             timeline. If the timeline is unavailable or disabled, this has
///             no effect. Can be called on any thread. Strings passed into the
///             function will NOT be copied when added to the timeline. Only
///             string literals may be passed in.
///
/// @param[in]  name  The name of the trace event.
///
FLUTTER_EXPORT
void FlutterEngineTraceEventInstant(const char* name);

//------------------------------------------------------------------------------
/// @brief      Posts a task onto the Flutter render thread. Typically, this may
///             be called from any thread as long as a `FlutterEngineShutdown`
///             on the specific engine has not already been initiated.
///
/// @param[in]  engine         A running engine instance.
/// @param[in]  callback       The callback to execute on the render thread.
/// @param      callback_data  The callback context.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEnginePostRenderThreadTask(
    FLUTTER_API_SYMBOL(FlutterEngine) engine,
    VoidCallback callback,
    void* callback_data);

//------------------------------------------------------------------------------
/// @brief      Get the current time in nanoseconds from the clock used by the
///             flutter engine. This is the system monotonic clock.
///
/// @return     The current time in nanoseconds.
///
FLUTTER_EXPORT
uint64_t FlutterEngineGetCurrentTime();

//------------------------------------------------------------------------------
/// @brief      Inform the engine to run the specified task. This task has been
///             given to the engine via the
///             `FlutterTaskRunnerDescription.post_task_callback`. This call
///             must only be made at the target time specified in that callback.
///             Running the task before that time is undefined behavior.
///
/// @param[in]  engine     a running instance.
/// @param[in]  task       the task handle.
///
/// @return     The result of the call.
///
FLUTTER_EXPORT
FlutterEngineResult FlutterEngineRunTask(FLUTTER_API_SYMBOL(FlutterEngine)
                                             engine,
                                         const FlutterTask* task);

#if defined(__cplusplus)
}  // extern "C"
#endif

#endif  // FLUTTER_EMBEDDER_H_