shell/platform/darwin/macos/framework/Source/FlutterViewController.mm - external/github.com/flutter/engine - Git at Google

 // 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.

 #import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterViewController.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"

 #import "flutter/shell/platform/darwin/common/framework/Headers/FlutterChannels.h"
 #import "flutter/shell/platform/darwin/common/framework/Headers/FlutterCodecs.h"
 #import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
 #import "flutter/shell/platform/embedder/embedder.h"

 namespace {

 /// Clipboard plain text format.
 constexpr char kTextPlainFormat[] = "text/plain";

 /**
  * State tracking for mouse events, to adapt between the events coming from the system and the
  * events that the embedding API expects.
  */
 struct MouseState {
   /**
    * Whether or not a kAdd event has been sent (or sent again since the last kRemove if tracking is
    * enabled). Used to determine whether to send a kAdd event before sending an incoming mouse
    * event, since Flutter expects pointers to be added before events are sent for them.
    */
   bool flutter_state_is_added = false;

   /**
    * Whether or not a kDown has been sent since the last kAdd/kUp.
    */
   bool flutter_state_is_down = false;

   /**
    * Whether or not mouseExited: was received while a button was down. Cocoa's behavior when
    * dragging out of a tracked area is to send an exit, then keep sending drag events until the last
    * button is released. If it was released inside the view, mouseEntered: is sent the next time the
    * mouse moves. Flutter doesn't expect to receive events after a kRemove, so the kRemove for the
    * exit needs to be delayed until after the last mouse button is released.
    */
   bool has_pending_exit = false;

   /**
    * The currently pressed buttons, as represented in FlutterPointerEvent.
    */
   int64_t buttons = 0;

   /**
    * Resets all state to default values.
    */
   void Reset() {
     flutter_state_is_added = false;
     flutter_state_is_down = false;
     has_pending_exit = false;
     buttons = 0;
   }
 };

 /**
  * State tracking for keyboard events, to adapt between the events coming from the system and the
  * events that the embedding API expects.
  */
 struct KeyboardState {
   /**
    * The last known pressed modifier flag keys.
    */
   uint64_t previously_pressed_flags = 0;
 };

 }  // namespace

 #pragma mark - Private interface declaration.

 /**
  * Private interface declaration for FlutterViewController.
  */
 @interface FlutterViewController () <FlutterViewReshapeListener>

 /**
  * A list of additional responders to keyboard events. Keybord events are forwarded to all of them.
  */
 @property(nonatomic) NSMutableOrderedSet<NSResponder*>* additionalKeyResponders;

 /**
  * The tracking area used to generate hover events, if enabled.
  */
 @property(nonatomic) NSTrackingArea* trackingArea;

 /**
  * The current state of the mouse and the sent mouse events.
  */
 @property(nonatomic) MouseState mouseState;

 /**
  * The current state of the keyboard and pressed keys.
  */
 @property(nonatomic) KeyboardState keyboardState;

 /**
  * Event monitor for keyUp events.
  */
 @property(nonatomic) id keyUpMonitor;

 /**
  * Starts running |engine|, including any initial setup.
  */
 - (BOOL)launchEngine;

 /**
  * Updates |trackingArea| for the current tracking settings, creating it with
  * the correct mode if tracking is enabled, or removing it if not.
  */
 - (void)configureTrackingArea;

 /**
  * Creates and registers plugins used by this view controller.
  */
 - (void)addInternalPlugins;

 /**
  * Calls dispatchMouseEvent:phase: with a phase determined by self.mouseState.
  *
  * mouseState.buttons should be updated before calling this method.
  */
 - (void)dispatchMouseEvent:(nonnull NSEvent*)event;

 /**
  * Converts |event| to a FlutterPointerEvent with the given phase, and sends it to the engine.
  */
 - (void)dispatchMouseEvent:(nonnull NSEvent*)event phase:(FlutterPointerPhase)phase;

 /**
  * Converts |event| to a key event channel message, and sends it to the engine.
  */
 - (void)dispatchKeyEvent:(NSEvent*)event ofType:(NSString*)type;

 /**
  * Initializes the KVO for user settings and passes the initial user settings to the engine.
  */
 - (void)sendInitialSettings;

 /**
  * Responsds to updates in the user settings and passes this data to the engine.
  */
 - (void)onSettingsChanged:(NSNotification*)notification;

 /**
  * Handles messages received from the Flutter engine on the _*Channel channels.
  */
 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result;

 /**
  * Reads the data from the clipboard. |format| specifies the media type of the
  * data to obtain.
  */
 - (NSDictionary*)getClipboardData:(NSString*)format;

 /**
  * Clears contents and writes new data into clipboard. |data| is a dictionary where
  * the keys are the type of data, and tervalue the data to be stored.
  */
 - (void)setClipboardData:(NSDictionary*)data;

 @end

 #pragma mark - FlutterViewController implementation.

 @implementation FlutterViewController {
   // The project to run in this controller's engine.
   FlutterDartProject* _project;

   // The plugin used to handle text input. This is not an FlutterPlugin, so must be owned
   // separately.
   FlutterTextInputPlugin* _textInputPlugin;

   // A message channel for passing key events to the Flutter engine. This should be replaced with
   // an embedding API; see Issue #47.
   FlutterBasicMessageChannel* _keyEventChannel;

   // A message channel for sending user settings to the flutter engine.
   FlutterBasicMessageChannel* _settingsChannel;

   // A method channel for miscellaneous platform functionality.
   FlutterMethodChannel* _platformChannel;
 }

 @dynamic view;

 /**
  * Performs initialization that's common between the different init paths.
  */
 static void CommonInit(FlutterViewController* controller) {
   controller->_engine = [[FlutterEngine alloc] initWithName:@"io.flutter"
                                                     project:controller->_project
                                      allowHeadlessExecution:NO];
   controller->_additionalKeyResponders = [[NSMutableOrderedSet alloc] init];
   controller->_mouseTrackingMode = FlutterMouseTrackingModeInKeyWindow;
 }

 - (instancetype)initWithCoder:(NSCoder*)coder {
   self = [super initWithCoder:coder];
   NSAssert(self, @"Super init cannot be nil");

   CommonInit(self);
   return self;
 }

 - (instancetype)initWithNibName:(NSString*)nibNameOrNil bundle:(NSBundle*)nibBundleOrNil {
   self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
   NSAssert(self, @"Super init cannot be nil");

   CommonInit(self);
   return self;
 }

 - (instancetype)initWithProject:(nullable FlutterDartProject*)project {
   self = [super initWithNibName:nil bundle:nil];
   NSAssert(self, @"Super init cannot be nil");

   _project = project;
   CommonInit(self);
   return self;
 }

 - (void)loadView {
   NSOpenGLContext* resourceContext = _engine.resourceContext;
   if (!resourceContext) {
     NSLog(@"Unable to create FlutterView; no resource context available.");
     return;
   }
   FlutterView* flutterView = [[FlutterView alloc] initWithShareContext:resourceContext
                                                        reshapeListener:self];
   self.view = flutterView;
 }

 - (void)viewDidLoad {
   [self configureTrackingArea];
 }

 - (void)viewWillAppear {
   [super viewWillAppear];
   if (!_engine.running) {
     [self launchEngine];
   }
   [self listenForMetaModifiedKeyUpEvents];
 }

 - (void)viewWillDisappear {
   // Per Apple's documentation, it is discouraged to call removeMonitor: in dealloc, and it's
   // recommended to be called earlier in the lifecycle.
   [NSEvent removeMonitor:_keyUpMonitor];
   _keyUpMonitor = nil;
 }

 - (void)dealloc {
   _engine.viewController = nil;
 }

 #pragma mark - Public methods

 - (void)setMouseTrackingMode:(FlutterMouseTrackingMode)mode {
   if (_mouseTrackingMode == mode) {
     return;
   }
   _mouseTrackingMode = mode;
   [self configureTrackingArea];
 }

 #pragma mark - Framework-internal methods

 - (FlutterView*)flutterView {
   return static_cast<FlutterView*>(self.view);
 }

 - (void)addKeyResponder:(NSResponder*)responder {
   [self.additionalKeyResponders addObject:responder];
 }

 - (void)removeKeyResponder:(NSResponder*)responder {
 }

 #pragma mark - Private methods

 - (BOOL)launchEngine {
   // Register internal plugins before starting the engine.
   [self addInternalPlugins];

   _engine.viewController = self;
   if (![_engine runWithEntrypoint:nil]) {
     return NO;
   }
   // Send the initial user settings such as brightness and text scale factor
   // to the engine.
   [self sendInitialSettings];
   return YES;
 }

 // macOS does not call keyUp: on a key while the command key is pressed. This results in a loss
 // of a key event once the modified key is released. This method registers the
 // ViewController as a listener for a keyUp event before it's handled by NSApplication, and should
 // NOT modify the event to avoid any unexpected behavior.
 - (void)listenForMetaModifiedKeyUpEvents {
   NSAssert(_keyUpMonitor == nil, @"_keyUpMonitor was already created");
   FlutterViewController* __weak weakSelf = self;
   _keyUpMonitor = [NSEvent
       addLocalMonitorForEventsMatchingMask:NSEventMaskKeyUp
                                    handler:^NSEvent*(NSEvent* event) {
                                      // Intercept keyUp only for events triggered on the current
                                      // view.
                                      if (weakSelf.view &&
                                          ([[event window] firstResponder] == weakSelf.view) &&
                                          ([event modifierFlags] & NSEventModifierFlagCommand) &&
                                          ([event type] == NSEventTypeKeyUp))
                                        [weakSelf keyUp:event];
                                      return event;
                                    }];
 }

 - (void)configureTrackingArea {
   if (_mouseTrackingMode != FlutterMouseTrackingModeNone && self.view) {
     NSTrackingAreaOptions options =
         NSTrackingMouseEnteredAndExited | NSTrackingMouseMoved | NSTrackingInVisibleRect;
     switch (_mouseTrackingMode) {
       case FlutterMouseTrackingModeInKeyWindow:
         options |= NSTrackingActiveInKeyWindow;
         break;
       case FlutterMouseTrackingModeInActiveApp:
         options |= NSTrackingActiveInActiveApp;
         break;
       case FlutterMouseTrackingModeAlways:
         options |= NSTrackingActiveAlways;
         break;
       default:
         NSLog(@"Error: Unrecognized mouse tracking mode: %ld", _mouseTrackingMode);
         return;
     }
     _trackingArea = [[NSTrackingArea alloc] initWithRect:NSZeroRect
                                                  options:options
                                                    owner:self
                                                 userInfo:nil];
     [self.view addTrackingArea:_trackingArea];
   } else if (_trackingArea) {
     [self.view removeTrackingArea:_trackingArea];
     _trackingArea = nil;
   }
 }

 - (void)addInternalPlugins {
   [FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]];
   _textInputPlugin = [[FlutterTextInputPlugin alloc] initWithViewController:self];
   _keyEventChannel =
       [FlutterBasicMessageChannel messageChannelWithName:@"flutter/keyevent"
                                          binaryMessenger:_engine.binaryMessenger
                                                    codec:[FlutterJSONMessageCodec sharedInstance]];
   _settingsChannel =
       [FlutterBasicMessageChannel messageChannelWithName:@"flutter/settings"
                                          binaryMessenger:_engine.binaryMessenger
                                                    codec:[FlutterJSONMessageCodec sharedInstance]];
   _platformChannel =
       [FlutterMethodChannel methodChannelWithName:@"flutter/platform"
                                   binaryMessenger:_engine.binaryMessenger
                                             codec:[FlutterJSONMethodCodec sharedInstance]];
   __weak FlutterViewController* weakSelf = self;
   [_platformChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
     [weakSelf handleMethodCall:call result:result];
   }];
 }

 - (void)dispatchMouseEvent:(nonnull NSEvent*)event {
   FlutterPointerPhase phase = _mouseState.buttons == 0
                                   ? (_mouseState.flutter_state_is_down ? kUp : kHover)
                                   : (_mouseState.flutter_state_is_down ? kMove : kDown);
   [self dispatchMouseEvent:event phase:phase];
 }

 - (void)dispatchMouseEvent:(NSEvent*)event phase:(FlutterPointerPhase)phase {
   // There are edge cases where the system will deliver enter out of order relative to other
   // events (e.g., drag out and back in, release, then click; mouseDown: will be called before
   // mouseEntered:). Discard those events, since the add will already have been synthesized.
   if (_mouseState.flutter_state_is_added && phase == kAdd) {
     return;
   }

   // If a pointer added event hasn't been sent, synthesize one using this event for the basic
   // information.
   if (!_mouseState.flutter_state_is_added && phase != kAdd) {
     // Only the values extracted for use in flutterEvent below matter, the rest are dummy values.
     NSEvent* addEvent = [NSEvent enterExitEventWithType:NSEventTypeMouseEntered
                                                location:event.locationInWindow
                                           modifierFlags:0
                                               timestamp:event.timestamp
                                            windowNumber:event.windowNumber
                                                 context:nil
                                             eventNumber:0
                                          trackingNumber:0
                                                userData:NULL];
     [self dispatchMouseEvent:addEvent phase:kAdd];
   }

   NSPoint locationInView = [self.view convertPoint:event.locationInWindow fromView:nil];
   NSPoint locationInBackingCoordinates = [self.view convertPointToBacking:locationInView];
   FlutterPointerEvent flutterEvent = {
       .struct_size = sizeof(flutterEvent),
       .phase = phase,
       .timestamp = static_cast<size_t>(event.timestamp * USEC_PER_SEC),
       .x = locationInBackingCoordinates.x,
       .y = -locationInBackingCoordinates.y,  // convertPointToBacking makes this negative.
       .device_kind = kFlutterPointerDeviceKindMouse,
       // If a click triggered a synthesized kAdd, don't pass the buttons in that event.
       .buttons = phase == kAdd ? 0 : _mouseState.buttons,
   };

   if (event.type == NSEventTypeScrollWheel) {
     flutterEvent.signal_kind = kFlutterPointerSignalKindScroll;

     double pixelsPerLine = 1.0;
     if (!event.hasPreciseScrollingDeltas) {
       CGEventSourceRef source = CGEventCreateSourceFromEvent(event.CGEvent);
       pixelsPerLine = CGEventSourceGetPixelsPerLine(source);
       if (source) {
         CFRelease(source);
       }
     }
     double scaleFactor = self.view.layer.contentsScale;
     flutterEvent.scroll_delta_x = -event.scrollingDeltaX * pixelsPerLine * scaleFactor;
     flutterEvent.scroll_delta_y = -event.scrollingDeltaY * pixelsPerLine * scaleFactor;
   }
   [_engine sendPointerEvent:flutterEvent];

   // Update tracking of state as reported to Flutter.
   if (phase == kDown) {
     _mouseState.flutter_state_is_down = true;
   } else if (phase == kUp) {
     _mouseState.flutter_state_is_down = false;
     if (_mouseState.has_pending_exit) {
       [self dispatchMouseEvent:event phase:kRemove];
       _mouseState.has_pending_exit = false;
     }
   } else if (phase == kAdd) {
     _mouseState.flutter_state_is_added = true;
   } else if (phase == kRemove) {
     _mouseState.Reset();
   }
 }

 - (void)dispatchKeyEvent:(NSEvent*)event ofType:(NSString*)type {
   NSMutableDictionary* keyMessage = [@{
     @"keymap" : @"macos",
     @"type" : type,
     @"keyCode" : @(event.keyCode),
     @"modifiers" : @(event.modifierFlags),
   } mutableCopy];
   // Calling these methods on any other type of event will raise an exception.
   if (event.type == NSEventTypeKeyDown || event.type == NSEventTypeKeyUp) {
     keyMessage[@"characters"] = event.characters;
     keyMessage[@"charactersIgnoringModifiers"] = event.charactersIgnoringModifiers;
   }
   [_keyEventChannel sendMessage:keyMessage];
 }

 - (void)onSettingsChanged:(NSNotification*)notification {
   // TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32015.
   NSString* brightness =
       [[NSUserDefaults standardUserDefaults] stringForKey:@"AppleInterfaceStyle"];
   [_settingsChannel sendMessage:@{
     @"platformBrightness" : [brightness isEqualToString:@"Dark"] ? @"dark" : @"light",
     // TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32006.
     @"textScaleFactor" : @1.0,
     @"alwaysUse24HourFormat" : @false
   }];
 }

 - (void)sendInitialSettings {
   // TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32015.
   [[NSDistributedNotificationCenter defaultCenter]
       addObserver:self
          selector:@selector(onSettingsChanged:)
              name:@"AppleInterfaceThemeChangedNotification"
            object:nil];
   [self onSettingsChanged:nil];
 }

 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
   if ([call.method isEqualToString:@"SystemNavigator.pop"]) {
     [NSApp terminate:self];
     result(nil);
   } else if ([call.method isEqualToString:@"Clipboard.getData"]) {
     result([self getClipboardData:call.arguments]);
   } else if ([call.method isEqualToString:@"Clipboard.setData"]) {
     [self setClipboardData:call.arguments];
     result(nil);
   } else {
     result(FlutterMethodNotImplemented);
   }
 }

 - (NSDictionary*)getClipboardData:(NSString*)format {
   NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
   if ([format isEqualToString:@(kTextPlainFormat)]) {
     NSString* stringInPasteboard = [pasteboard stringForType:NSPasteboardTypeString];
     return stringInPasteboard == nil ? nil : @{@"text" : stringInPasteboard};
   }
   return nil;
 }

 - (void)setClipboardData:(NSDictionary*)data {
   NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
   NSString* text = data[@"text"];
   if (text && ![text isEqual:[NSNull null]]) {
     [pasteboard clearContents];
     [pasteboard setString:text forType:NSPasteboardTypeString];
   }
 }

 #pragma mark - FlutterViewReshapeListener

 /**
  * Responds to view reshape by notifying the engine of the change in dimensions.
  */
 - (void)viewDidReshape:(NSView*)view {
   [_engine updateWindowMetrics];
 }

 #pragma mark - FlutterPluginRegistry

 - (id<FlutterPluginRegistrar>)registrarForPlugin:(NSString*)pluginName {
   return [_engine registrarForPlugin:pluginName];
 }

 #pragma mark - NSResponder

 - (BOOL)acceptsFirstResponder {
   return YES;
 }

 - (void)keyDown:(NSEvent*)event {
   [self dispatchKeyEvent:event ofType:@"keydown"];
   for (NSResponder* responder in self.additionalKeyResponders) {
     if ([responder respondsToSelector:@selector(keyDown:)]) {
       [responder keyDown:event];
     }
   }
 }

 - (void)keyUp:(NSEvent*)event {
   [self dispatchKeyEvent:event ofType:@"keyup"];
   for (NSResponder* responder in self.additionalKeyResponders) {
     if ([responder respondsToSelector:@selector(keyUp:)]) {
       [responder keyUp:event];
     }
   }
 }

 - (void)flagsChanged:(NSEvent*)event {
   if (event.modifierFlags < _keyboardState.previously_pressed_flags) {
     [self keyUp:event];
   } else {
     [self keyDown:event];
   }
   _keyboardState.previously_pressed_flags = event.modifierFlags;
 }

 - (void)mouseEntered:(NSEvent*)event {
   [self dispatchMouseEvent:event phase:kAdd];
 }

 - (void)mouseExited:(NSEvent*)event {
   if (_mouseState.buttons != 0) {
     _mouseState.has_pending_exit = true;
     return;
   }
   [self dispatchMouseEvent:event phase:kRemove];
 }

 - (void)mouseDown:(NSEvent*)event {
   _mouseState.buttons |= kFlutterPointerButtonMousePrimary;
   [self dispatchMouseEvent:event];
 }

 - (void)mouseUp:(NSEvent*)event {
   _mouseState.buttons &= ~static_cast<uint64_t>(kFlutterPointerButtonMousePrimary);
   [self dispatchMouseEvent:event];
 }

 - (void)mouseDragged:(NSEvent*)event {
   [self dispatchMouseEvent:event];
 }

 - (void)rightMouseDown:(NSEvent*)event {
   _mouseState.buttons |= kFlutterPointerButtonMouseSecondary;
   [self dispatchMouseEvent:event];
 }

 - (void)rightMouseUp:(NSEvent*)event {
   _mouseState.buttons &= ~static_cast<uint64_t>(kFlutterPointerButtonMouseSecondary);
   [self dispatchMouseEvent:event];
 }

 - (void)rightMouseDragged:(NSEvent*)event {
   [self dispatchMouseEvent:event];
 }

 - (void)otherMouseDown:(NSEvent*)event {
   _mouseState.buttons |= (1 << event.buttonNumber);
   [self dispatchMouseEvent:event];
 }

 - (void)otherMouseUp:(NSEvent*)event {
   _mouseState.buttons &= ~static_cast<uint64_t>(1 << event.buttonNumber);
   [self dispatchMouseEvent:event];
 }

 - (void)otherMouseDragged:(NSEvent*)event {
   [self dispatchMouseEvent:event];
 }

 - (void)mouseMoved:(NSEvent*)event {
   [self dispatchMouseEvent:event];
 }

 - (void)scrollWheel:(NSEvent*)event {
   // TODO: Add gesture-based (trackpad) scroll support once it's supported by the engine rather
   // than always using kHover.
   [self dispatchMouseEvent:event phase:kHover];
 }

 @end
	// 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.

	#import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterViewController.h"
	#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewController_Internal.h"

	#import "flutter/shell/platform/darwin/common/framework/Headers/FlutterChannels.h"
	#import "flutter/shell/platform/darwin/common/framework/Headers/FlutterCodecs.h"
	#import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterEngine.h"
	#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
	#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h"
	#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputPlugin.h"
	#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
	#import "flutter/shell/platform/embedder/embedder.h"

	namespace {

	/// Clipboard plain text format.
	constexpr char kTextPlainFormat[] = "text/plain";

	/**
	* State tracking for mouse events, to adapt between the events coming from the system and the
	* events that the embedding API expects.
	*/
	struct MouseState {
	/**
	* Whether or not a kAdd event has been sent (or sent again since the last kRemove if tracking is
	* enabled). Used to determine whether to send a kAdd event before sending an incoming mouse
	* event, since Flutter expects pointers to be added before events are sent for them.
	*/
	bool flutter_state_is_added = false;

	/**
	* Whether or not a kDown has been sent since the last kAdd/kUp.
	*/
	bool flutter_state_is_down = false;

	/**
	* Whether or not mouseExited: was received while a button was down. Cocoa's behavior when
	* dragging out of a tracked area is to send an exit, then keep sending drag events until the last
	* button is released. If it was released inside the view, mouseEntered: is sent the next time the
	* mouse moves. Flutter doesn't expect to receive events after a kRemove, so the kRemove for the
	* exit needs to be delayed until after the last mouse button is released.
	*/
	bool has_pending_exit = false;

	/**
	* The currently pressed buttons, as represented in FlutterPointerEvent.
	*/
	int64_t buttons = 0;

	/**
	* Resets all state to default values.
	*/
	void Reset() {
	flutter_state_is_added = false;
	flutter_state_is_down = false;
	has_pending_exit = false;
	buttons = 0;
	}
	};

	/**
	* State tracking for keyboard events, to adapt between the events coming from the system and the
	* events that the embedding API expects.
	*/
	struct KeyboardState {
	/**
	* The last known pressed modifier flag keys.
	*/
	uint64_t previously_pressed_flags = 0;
	};

	} // namespace

	#pragma mark - Private interface declaration.

	/**
	* Private interface declaration for FlutterViewController.
	*/
	@interface FlutterViewController () <FlutterViewReshapeListener>

	/**
	* A list of additional responders to keyboard events. Keybord events are forwarded to all of them.
	*/
	@property(nonatomic) NSMutableOrderedSet<NSResponder> additionalKeyResponders;

	/**
	* The tracking area used to generate hover events, if enabled.
	*/
	@property(nonatomic) NSTrackingArea* trackingArea;

	/**
	* The current state of the mouse and the sent mouse events.
	*/
	@property(nonatomic) MouseState mouseState;

	/**
	* The current state of the keyboard and pressed keys.
	*/
	@property(nonatomic) KeyboardState keyboardState;

	/**
	* Event monitor for keyUp events.
	*/
	@property(nonatomic) id keyUpMonitor;

	/**
	* Starts running \|engine\|, including any initial setup.
	*/
	- (BOOL)launchEngine;

	/**
	* Updates \|trackingArea\| for the current tracking settings, creating it with
	* the correct mode if tracking is enabled, or removing it if not.
	*/
	- (void)configureTrackingArea;

	/**
	* Creates and registers plugins used by this view controller.
	*/
	- (void)addInternalPlugins;

	/**
	* Calls dispatchMouseEvent:phase: with a phase determined by self.mouseState.
	*
	* mouseState.buttons should be updated before calling this method.
	*/
	- (void)dispatchMouseEvent:(nonnull NSEvent*)event;

	/**
	* Converts \|event\| to a FlutterPointerEvent with the given phase, and sends it to the engine.
	*/
	- (void)dispatchMouseEvent:(nonnull NSEvent*)event phase:(FlutterPointerPhase)phase;

	/**
	* Converts \|event\| to a key event channel message, and sends it to the engine.
	*/
	- (void)dispatchKeyEvent:(NSEvent)event ofType:(NSString)type;

	/**
	* Initializes the KVO for user settings and passes the initial user settings to the engine.
	*/
	- (void)sendInitialSettings;

	/**
	* Responsds to updates in the user settings and passes this data to the engine.
	*/
	- (void)onSettingsChanged:(NSNotification*)notification;

	/**
	* Handles messages received from the Flutter engine on the _*Channel channels.
	*/
	- (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result;

	/**
	* Reads the data from the clipboard. \|format\| specifies the media type of the
	* data to obtain.
	*/
	- (NSDictionary)getClipboardData:(NSString)format;

	/**
	* Clears contents and writes new data into clipboard. \|data\| is a dictionary where
	* the keys are the type of data, and tervalue the data to be stored.
	*/
	- (void)setClipboardData:(NSDictionary*)data;

	@end

	#pragma mark - FlutterViewController implementation.

	@implementation FlutterViewController {
	// The project to run in this controller's engine.
	FlutterDartProject* _project;

	// The plugin used to handle text input. This is not an FlutterPlugin, so must be owned
	// separately.
	FlutterTextInputPlugin* _textInputPlugin;

	// A message channel for passing key events to the Flutter engine. This should be replaced with
	// an embedding API; see Issue #47.
	FlutterBasicMessageChannel* _keyEventChannel;

	// A message channel for sending user settings to the flutter engine.
	FlutterBasicMessageChannel* _settingsChannel;

	// A method channel for miscellaneous platform functionality.
	FlutterMethodChannel* _platformChannel;
	}

	@dynamic view;

	/**
	* Performs initialization that's common between the different init paths.
	*/
	static void CommonInit(FlutterViewController* controller) {
	controller->_engine = [[FlutterEngine alloc] initWithName:@"io.flutter"
	project:controller->_project
	allowHeadlessExecution:NO];
	controller->_additionalKeyResponders = [[NSMutableOrderedSet alloc] init];
	controller->_mouseTrackingMode = FlutterMouseTrackingModeInKeyWindow;
	}

	- (instancetype)initWithCoder:(NSCoder*)coder {
	self = [super initWithCoder:coder];
	NSAssert(self, @"Super init cannot be nil");

	CommonInit(self);
	return self;
	}

	- (instancetype)initWithNibName:(NSString)nibNameOrNil bundle:(NSBundle)nibBundleOrNil {
	self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
	NSAssert(self, @"Super init cannot be nil");

	CommonInit(self);
	return self;
	}

	- (instancetype)initWithProject:(nullable FlutterDartProject*)project {
	self = [super initWithNibName:nil bundle:nil];
	NSAssert(self, @"Super init cannot be nil");

	_project = project;
	CommonInit(self);
	return self;
	}

	- (void)loadView {
	NSOpenGLContext* resourceContext = _engine.resourceContext;
	if (!resourceContext) {
	NSLog(@"Unable to create FlutterView; no resource context available.");
	return;
	}
	FlutterView* flutterView = [[FlutterView alloc] initWithShareContext:resourceContext
	reshapeListener:self];
	self.view = flutterView;
	}

	- (void)viewDidLoad {
	[self configureTrackingArea];
	}

	- (void)viewWillAppear {
	[super viewWillAppear];
	if (!_engine.running) {
	[self launchEngine];
	}
	[self listenForMetaModifiedKeyUpEvents];
	}

	- (void)viewWillDisappear {
	// Per Apple's documentation, it is discouraged to call removeMonitor: in dealloc, and it's
	// recommended to be called earlier in the lifecycle.
	[NSEvent removeMonitor:_keyUpMonitor];
	_keyUpMonitor = nil;
	}

	- (void)dealloc {
	_engine.viewController = nil;
	}

	#pragma mark - Public methods

	- (void)setMouseTrackingMode:(FlutterMouseTrackingMode)mode {
	if (_mouseTrackingMode == mode) {
	return;
	}
	_mouseTrackingMode = mode;
	[self configureTrackingArea];
	}

	#pragma mark - Framework-internal methods

	- (FlutterView*)flutterView {
	return static_cast<FlutterView*>(self.view);
	}

	- (void)addKeyResponder:(NSResponder*)responder {
	[self.additionalKeyResponders addObject:responder];
	}

	- (void)removeKeyResponder:(NSResponder*)responder {
	}

	#pragma mark - Private methods

	- (BOOL)launchEngine {
	// Register internal plugins before starting the engine.
	[self addInternalPlugins];

	_engine.viewController = self;
	if (![_engine runWithEntrypoint:nil]) {
	return NO;
	}
	// Send the initial user settings such as brightness and text scale factor
	// to the engine.
	[self sendInitialSettings];
	return YES;
	}

	// macOS does not call keyUp: on a key while the command key is pressed. This results in a loss
	// of a key event once the modified key is released. This method registers the
	// ViewController as a listener for a keyUp event before it's handled by NSApplication, and should
	// NOT modify the event to avoid any unexpected behavior.
	- (void)listenForMetaModifiedKeyUpEvents {
	NSAssert(_keyUpMonitor == nil, @"_keyUpMonitor was already created");
	FlutterViewController* __weak weakSelf = self;
	_keyUpMonitor = [NSEvent
	addLocalMonitorForEventsMatchingMask:NSEventMaskKeyUp
	handler:^NSEvent(NSEvent event) {
	// Intercept keyUp only for events triggered on the current
	// view.
	if (weakSelf.view &&
	([[event window] firstResponder] == weakSelf.view) &&
	([event modifierFlags] & NSEventModifierFlagCommand) &&
	([event type] == NSEventTypeKeyUp))
	[weakSelf keyUp:event];
	return event;
	}];
	}

	- (void)configureTrackingArea {
	if (_mouseTrackingMode != FlutterMouseTrackingModeNone && self.view) {
	NSTrackingAreaOptions options =
	NSTrackingMouseEnteredAndExited \| NSTrackingMouseMoved \| NSTrackingInVisibleRect;
	switch (_mouseTrackingMode) {
	case FlutterMouseTrackingModeInKeyWindow:
	options \|= NSTrackingActiveInKeyWindow;
	break;
	case FlutterMouseTrackingModeInActiveApp:
	options \|= NSTrackingActiveInActiveApp;
	break;
	case FlutterMouseTrackingModeAlways:
	options \|= NSTrackingActiveAlways;
	break;
	default:
	NSLog(@"Error: Unrecognized mouse tracking mode: %ld", _mouseTrackingMode);
	return;
	}
	_trackingArea = [[NSTrackingArea alloc] initWithRect:NSZeroRect
	options:options
	owner:self
	userInfo:nil];
	[self.view addTrackingArea:_trackingArea];
	} else if (_trackingArea) {
	[self.view removeTrackingArea:_trackingArea];
	_trackingArea = nil;
	}
	}

	- (void)addInternalPlugins {
	[FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]];
	_textInputPlugin = [[FlutterTextInputPlugin alloc] initWithViewController:self];
	_keyEventChannel =
	[FlutterBasicMessageChannel messageChannelWithName:@"flutter/keyevent"
	binaryMessenger:_engine.binaryMessenger
	codec:[FlutterJSONMessageCodec sharedInstance]];
	_settingsChannel =
	[FlutterBasicMessageChannel messageChannelWithName:@"flutter/settings"
	binaryMessenger:_engine.binaryMessenger
	codec:[FlutterJSONMessageCodec sharedInstance]];
	_platformChannel =
	[FlutterMethodChannel methodChannelWithName:@"flutter/platform"
	binaryMessenger:_engine.binaryMessenger
	codec:[FlutterJSONMethodCodec sharedInstance]];
	__weak FlutterViewController* weakSelf = self;
	[_platformChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
	[weakSelf handleMethodCall:call result:result];
	}];
	}

	- (void)dispatchMouseEvent:(nonnull NSEvent*)event {
	FlutterPointerPhase phase = _mouseState.buttons == 0
	? (_mouseState.flutter_state_is_down ? kUp : kHover)
	: (_mouseState.flutter_state_is_down ? kMove : kDown);
	[self dispatchMouseEvent:event phase:phase];
	}

	- (void)dispatchMouseEvent:(NSEvent*)event phase:(FlutterPointerPhase)phase {
	// There are edge cases where the system will deliver enter out of order relative to other
	// events (e.g., drag out and back in, release, then click; mouseDown: will be called before
	// mouseEntered:). Discard those events, since the add will already have been synthesized.
	if (_mouseState.flutter_state_is_added && phase == kAdd) {
	return;
	}

	// If a pointer added event hasn't been sent, synthesize one using this event for the basic
	// information.
	if (!_mouseState.flutter_state_is_added && phase != kAdd) {
	// Only the values extracted for use in flutterEvent below matter, the rest are dummy values.
	NSEvent* addEvent = [NSEvent enterExitEventWithType:NSEventTypeMouseEntered
	location:event.locationInWindow
	modifierFlags:0
	timestamp:event.timestamp
	windowNumber:event.windowNumber
	context:nil
	eventNumber:0
	trackingNumber:0
	userData:NULL];
	[self dispatchMouseEvent:addEvent phase:kAdd];
	}

	NSPoint locationInView = [self.view convertPoint:event.locationInWindow fromView:nil];
	NSPoint locationInBackingCoordinates = [self.view convertPointToBacking:locationInView];
	FlutterPointerEvent flutterEvent = {
	.struct_size = sizeof(flutterEvent),
	.phase = phase,
	.timestamp = static_cast<size_t>(event.timestamp * USEC_PER_SEC),
	.x = locationInBackingCoordinates.x,
	.y = -locationInBackingCoordinates.y, // convertPointToBacking makes this negative.
	.device_kind = kFlutterPointerDeviceKindMouse,
	// If a click triggered a synthesized kAdd, don't pass the buttons in that event.
	.buttons = phase == kAdd ? 0 : _mouseState.buttons,
	};

	if (event.type == NSEventTypeScrollWheel) {
	flutterEvent.signal_kind = kFlutterPointerSignalKindScroll;

	double pixelsPerLine = 1.0;
	if (!event.hasPreciseScrollingDeltas) {
	CGEventSourceRef source = CGEventCreateSourceFromEvent(event.CGEvent);
	pixelsPerLine = CGEventSourceGetPixelsPerLine(source);
	if (source) {
	CFRelease(source);
	}
	}
	double scaleFactor = self.view.layer.contentsScale;
	flutterEvent.scroll_delta_x = -event.scrollingDeltaX * pixelsPerLine * scaleFactor;
	flutterEvent.scroll_delta_y = -event.scrollingDeltaY * pixelsPerLine * scaleFactor;
	}
	[_engine sendPointerEvent:flutterEvent];

	// Update tracking of state as reported to Flutter.
	if (phase == kDown) {
	_mouseState.flutter_state_is_down = true;
	} else if (phase == kUp) {
	_mouseState.flutter_state_is_down = false;
	if (_mouseState.has_pending_exit) {
	[self dispatchMouseEvent:event phase:kRemove];
	_mouseState.has_pending_exit = false;
	}
	} else if (phase == kAdd) {
	_mouseState.flutter_state_is_added = true;
	} else if (phase == kRemove) {
	_mouseState.Reset();
	}
	}

	- (void)dispatchKeyEvent:(NSEvent)event ofType:(NSString)type {
	NSMutableDictionary* keyMessage = [@{
	@"keymap" : @"macos",
	@"type" : type,
	@"keyCode" : @(event.keyCode),
	@"modifiers" : @(event.modifierFlags),
	} mutableCopy];
	// Calling these methods on any other type of event will raise an exception.
	if (event.type == NSEventTypeKeyDown \|\| event.type == NSEventTypeKeyUp) {
	keyMessage[@"characters"] = event.characters;
	keyMessage[@"charactersIgnoringModifiers"] = event.charactersIgnoringModifiers;
	}
	[_keyEventChannel sendMessage:keyMessage];
	}

	- (void)onSettingsChanged:(NSNotification*)notification {
	// TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32015.
	NSString* brightness =
	[[NSUserDefaults standardUserDefaults] stringForKey:@"AppleInterfaceStyle"];
	[_settingsChannel sendMessage:@{
	@"platformBrightness" : [brightness isEqualToString:@"Dark"] ? @"dark" : @"light",
	// TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32006.
	@"textScaleFactor" : @1.0,
	@"alwaysUse24HourFormat" : @false
	}];
	}

	- (void)sendInitialSettings {
	// TODO(jonahwilliams): https://github.com/flutter/flutter/issues/32015.
	[[NSDistributedNotificationCenter defaultCenter]
	addObserver:self
	selector:@selector(onSettingsChanged:)
	name:@"AppleInterfaceThemeChangedNotification"
	object:nil];
	[self onSettingsChanged:nil];
	}

	- (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
	if ([call.method isEqualToString:@"SystemNavigator.pop"]) {
	[NSApp terminate:self];
	result(nil);
	} else if ([call.method isEqualToString:@"Clipboard.getData"]) {
	result([self getClipboardData:call.arguments]);
	} else if ([call.method isEqualToString:@"Clipboard.setData"]) {
	[self setClipboardData:call.arguments];
	result(nil);
	} else {
	result(FlutterMethodNotImplemented);
	}
	}

	- (NSDictionary)getClipboardData:(NSString)format {
	NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
	if ([format isEqualToString:@(kTextPlainFormat)]) {
	NSString* stringInPasteboard = [pasteboard stringForType:NSPasteboardTypeString];
	return stringInPasteboard == nil ? nil : @{@"text" : stringInPasteboard};
	}
	return nil;
	}

	- (void)setClipboardData:(NSDictionary*)data {
	NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
	NSString* text = data[@"text"];
	if (text && ![text isEqual:[NSNull null]]) {
	[pasteboard clearContents];
	[pasteboard setString:text forType:NSPasteboardTypeString];
	}
	}

	#pragma mark - FlutterViewReshapeListener

	/**
	* Responds to view reshape by notifying the engine of the change in dimensions.
	*/
	- (void)viewDidReshape:(NSView*)view {
	[_engine updateWindowMetrics];
	}

	#pragma mark - FlutterPluginRegistry

	- (id<FlutterPluginRegistrar>)registrarForPlugin:(NSString*)pluginName {
	return [_engine registrarForPlugin:pluginName];
	}

	#pragma mark - NSResponder

	- (BOOL)acceptsFirstResponder {
	return YES;
	}

	- (void)keyDown:(NSEvent*)event {
	[self dispatchKeyEvent:event ofType:@"keydown"];
	for (NSResponder* responder in self.additionalKeyResponders) {
	if ([responder respondsToSelector:@selector(keyDown:)]) {
	[responder keyDown:event];
	}
	}
	}

	- (void)keyUp:(NSEvent*)event {
	[self dispatchKeyEvent:event ofType:@"keyup"];
	for (NSResponder* responder in self.additionalKeyResponders) {
	if ([responder respondsToSelector:@selector(keyUp:)]) {
	[responder keyUp:event];
	}
	}
	}

	- (void)flagsChanged:(NSEvent*)event {
	if (event.modifierFlags < _keyboardState.previously_pressed_flags) {
	[self keyUp:event];
	} else {
	[self keyDown:event];
	}
	_keyboardState.previously_pressed_flags = event.modifierFlags;
	}

	- (void)mouseEntered:(NSEvent*)event {
	[self dispatchMouseEvent:event phase:kAdd];
	}

	- (void)mouseExited:(NSEvent*)event {
	if (_mouseState.buttons != 0) {
	_mouseState.has_pending_exit = true;
	return;
	}
	[self dispatchMouseEvent:event phase:kRemove];
	}

	- (void)mouseDown:(NSEvent*)event {
	_mouseState.buttons \|= kFlutterPointerButtonMousePrimary;
	[self dispatchMouseEvent:event];
	}

	- (void)mouseUp:(NSEvent*)event {
	_mouseState.buttons &= ~static_cast<uint64_t>(kFlutterPointerButtonMousePrimary);
	[self dispatchMouseEvent:event];
	}

	- (void)mouseDragged:(NSEvent*)event {
	[self dispatchMouseEvent:event];
	}

	- (void)rightMouseDown:(NSEvent*)event {
	_mouseState.buttons \|= kFlutterPointerButtonMouseSecondary;
	[self dispatchMouseEvent:event];
	}

	- (void)rightMouseUp:(NSEvent*)event {
	_mouseState.buttons &= ~static_cast<uint64_t>(kFlutterPointerButtonMouseSecondary);
	[self dispatchMouseEvent:event];
	}

	- (void)rightMouseDragged:(NSEvent*)event {
	[self dispatchMouseEvent:event];
	}

	- (void)otherMouseDown:(NSEvent*)event {
	_mouseState.buttons \|= (1 << event.buttonNumber);
	[self dispatchMouseEvent:event];
	}

	- (void)otherMouseUp:(NSEvent*)event {
	_mouseState.buttons &= ~static_cast<uint64_t>(1 << event.buttonNumber);
	[self dispatchMouseEvent:event];
	}

	- (void)otherMouseDragged:(NSEvent*)event {
	[self dispatchMouseEvent:event];
	}

	- (void)mouseMoved:(NSEvent*)event {
	[self dispatchMouseEvent:event];
	}

	- (void)scrollWheel:(NSEvent*)event {
	// TODO: Add gesture-based (trackpad) scroll support once it's supported by the engine rather
	// than always using kHover.
	[self dispatchMouseEvent:event phase:kHover];
	}

	@end