Begin separating macOS engine from view controller

ci/licenses_golden/licenses_flutter

@@ -739,6 +739,7 @@ FILE: ../../../flutter/shell/platform/darwin/ios/ios_surface_software.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/platform_view_ios.h
 FILE: ../../../flutter/shell/platform/darwin/ios/platform_view_ios.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/FlutterMacOS.podspec
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FLEEngine.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FLEOpenGLContextHandling.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FLEReshapeListener.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FLEView.h
@@ -747,6 +748,8 @@ FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FlutterMacO
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FlutterPluginMacOS.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Headers/FlutterPluginRegistrarMacOS.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Info.plist
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FLEEngine.mm
+FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FLEEngine_Internal.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FLETextInputModel.h
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FLETextInputModel.mm
 FILE: ../../../flutter/shell/platform/darwin/macos/framework/Source/FLETextInputPlugin.h

shell/platform/darwin/macos/BUILD.gn

@@ -33,6 +33,7 @@ _flutter_framework_headers = [
   "framework/Headers/FlutterMacOS.h",
   "framework/Headers/FlutterPluginMacOS.h",
   "framework/Headers/FlutterPluginRegistrarMacOS.h",
+  "framework/Headers/FLEEngine.h",
   "framework/Headers/FLEOpenGLContextHandling.h",
   "framework/Headers/FLEReshapeListener.h",
   "framework/Headers/FLEView.h",
@@ -48,6 +49,8 @@ shared_library("create_flutter_framework_dylib") {
   output_name = "$_flutter_framework_name"
 
   sources = [
+    "framework/Source/FLEEngine.mm",
+    "framework/Source/FLEEngine_Internal.h",
     "framework/Source/FLETextInputModel.h",
     "framework/Source/FLETextInputModel.mm",
     "framework/Source/FLETextInputPlugin.h",

shell/platform/darwin/macos/framework/Headers/FLEEngine.h

@@ -0,0 +1,59 @@
+// 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_FLEENGINE_H_
+#define FLUTTER_FLEENGINE_H_
+
+#import <Foundation/Foundation.h>
+
+#include "FlutterBinaryMessenger.h"
+#include "FlutterMacros.h"
+#include "FlutterPluginRegistrarMacOS.h"
+
+@class FLEViewController;
+
+/**
+ * Coordinates a single instance of execution of a Flutter engine.
+ *
+ * TODO(stuartmorgan): Finish aligning this (and ideally merging) with FlutterEngine. Currently
+ * this is largely usable only as an implementation detail of FLEViewController.
+ */
+FLUTTER_EXPORT
+@interface FLEEngine : NSObject <FlutterPluginRegistry>
+
+/**
+ * Initializes an engine with the given viewController.
+ *
+ * @param viewController The view controller associated with this engine. If nil, the engine
+ *                       will be run headless.
+ */
+- (nonnull instancetype)initWithViewController:(nullable FLEViewController*)viewController;
+
+/**
+ * Launches the Flutter engine with the provided configuration.
+ *
+ * @param assets The path to the flutter_assets folder for the Flutter application to be run.
+ * @param arguments Arguments to pass to the Flutter engine. See
+ *                  https://github.com/flutter/engine/blob/master/shell/common/switches.h
+ *                  for details. Not all arguments will apply to embedding mode.
+ *                  Note: This API layer will abstract arguments in the future, instead of
+ *                  providing a direct passthrough.
+ * @return YES if the engine launched successfully.
+ */
+- (BOOL)launchEngineWithAssetsPath:(nonnull NSURL*)assets
+              commandLineArguments:(nullable NSArray<NSString*>*)arguments;
+
+/**
+ * The `FLEViewController` associated with this engine, if any.
+ */
+@property(nonatomic, nullable, readonly, weak) FLEViewController* viewController;
+
+/**
+ * The `FlutterBinaryMessenger` for communicating with this engine.
+ */
+@property(nonatomic, nonnull, readonly) id<FlutterBinaryMessenger> binaryMessenger;
+
+@end
+
+#endif  // FLUTTER_FLEENGINE_H_

shell/platform/darwin/macos/framework/Headers/FLEViewController.h

@@ -4,9 +4,9 @@
 
 #import <Cocoa/Cocoa.h>
 
+#import "FLEEngine.h"
 #import "FLEOpenGLContextHandling.h"
 #import "FLEReshapeListener.h"
-#import "FlutterBinaryMessenger.h"
 #import "FlutterMacros.h"
 #import "FlutterPluginRegistrarMacOS.h"
 
@@ -29,15 +29,19 @@ typedef NS_ENUM(NSInteger, FlutterMouseTrackingMode) {
  * Flutter engine in non-interactive mode, or with a drawable Flutter canvas.
  */
 FLUTTER_EXPORT
-@interface FLEViewController
-    : NSViewController <FlutterPluginRegistrar, FlutterPluginRegistry, FLEReshapeListener>
+@interface FLEViewController : NSViewController <FlutterPluginRegistry, FLEReshapeListener>
 
 /**
- * The view this controller manages when launched in interactive mode (headless set to false). Must
- * be capable of handling text input events, and the OpenGL context handling protocols.
+ * The view this controller manages. Must be capable of handling text input events, and the OpenGL
+ * context handling protocols.
  */
 @property(nullable) NSView<FLEOpenGLContextHandling>* view;
 
+/**
+ * The Flutter engine associated with this view controller.
+ */
+@property(nonatomic, nonnull, readonly) FLEEngine* engine;
+
 /**
  * The style of mouse tracking to use for the view. Defaults to
  * FlutterMouseTrackingModeInKeyWindow.
@@ -49,28 +53,13 @@ FLUTTER_EXPORT
  *
  * @param assets The path to the flutter_assets folder for the Flutter application to be run.
  * @param arguments Arguments to pass to the Flutter engine. See
- *               https://github.com/flutter/engine/blob/master/shell/common/switches.h
- *               for details. Not all arguments will apply to embedding mode.
- *               Note: This API layer will likely abstract arguments in the future, instead of
- *               providing a direct passthrough.
+ *                  https://github.com/flutter/engine/blob/master/shell/common/switches.h
+ *                  for details. Not all arguments will apply to embedding mode.
+ *                  Note: This API layer will abstract in the future, instead of providing a direct
+ *                  passthrough.
  * @return YES if the engine launched successfully.
  */
 - (BOOL)launchEngineWithAssetsPath:(nonnull NSURL*)assets
               commandLineArguments:(nullable NSArray<NSString*>*)arguments;
 
-/**
- * Launches the Flutter engine in headless mode with the provided configuration. In headless mode,
- * this controller's view should not be displayed.
- *
- * See launcheEngineWithAssetsPath:commandLineArguments: for details.
- */
-- (BOOL)launchHeadlessEngineWithAssetsPath:(nonnull NSURL*)assets
-                      commandLineArguments:(nullable NSArray<NSString*>*)arguments;
-
-/**
- * The `FlutterBinaryMessenger` associated with this FLEViewController (used for communicating
- * with channels).
- */
-@property(nonatomic, readonly) NSObject<FlutterBinaryMessenger>* _Nonnull binaryMessenger;
-
 @end

shell/platform/darwin/macos/framework/Headers/FlutterMacOS.h

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#import "FLEEngine.h"
 #import "FLEOpenGLContextHandling.h"
 #import "FLEReshapeListener.h"
 #import "FLEView.h"