System mouse cursor: macOS

shell/platform/darwin/macos/BUILD.gn

@@ -54,6 +54,8 @@ source_set("flutter_framework_source") {
     "framework/Source/FlutterEngine_Internal.h",
     "framework/Source/FlutterExternalTextureGL.h",
     "framework/Source/FlutterExternalTextureGL.mm",
+    "framework/Source/FlutterMouseCursorPlugin.h",
+    "framework/Source/FlutterMouseCursorPlugin.mm",
     "framework/Source/FlutterTextInputModel.h",
     "framework/Source/FlutterTextInputModel.mm",
     "framework/Source/FlutterTextInputPlugin.h",

shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h

@@ -0,0 +1,17 @@
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Cocoa/Cocoa.h>
+
+#import "flutter/shell/platform/darwin/common/framework/Headers/FlutterBinaryMessenger.h"
+#import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterViewController.h"
+
+/**
+ * A plugin to handle mouse cursor.
+ *
+ * Responsible for bridging the native macOS mouse cursor system with the
+ * Flutter framework mouse cursor classes, via system channels.
+ */
+@interface FlutterMouseCursorPlugin : NSObject <FlutterPlugin>
+
+@end

shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.mm

@@ -0,0 +1,137 @@
+// Copyright 2019 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 <objc/message.h>
+
+#import "FlutterMouseCursorPlugin.h"
+#import "flutter/shell/platform/darwin/common/framework/Headers/FlutterCodecs.h"
+
+static NSString* const kMouseCursorChannel = @"flutter/mousecursor";
+
+static NSString* const kActivateSystemCursorMethod = @"activateSystemCursor";
+static NSString* const kKindKey = @"kind";
+static NSString* const kDeviceKey = @"device";
+
+static NSString* const kKindValueNone = @"none";
+
+static NSMutableDictionary* cachedSystemCursors;
+
+// Maps a Flutter's constant to a platform's cursor object.
+//
+// Returns the arrow cursor for unknown constants, including kSystemShapeNone.
+static NSCursor* mapKindToCursor(NSString* kind) {
+  // The following mapping must be kept in sync with Flutter framework's
+  // mouse_cursor.dart
+  if ([kind isEqualToString:@"basic"])
+    return [NSCursor arrowCursor];
+  else if ([kind isEqualToString:@"click"])
+    return [NSCursor pointingHandCursor];
+  else if ([kind isEqualToString:@"text"])
+    return [NSCursor IBeamCursor];
+  else if ([kind isEqualToString:@"forbidden"])
+    return [NSCursor operationNotAllowedCursor];
+  else if ([kind isEqualToString:@"grab"])
+    return [NSCursor openHandCursor];
+  else if ([kind isEqualToString:@"grabbing"])
+    return [NSCursor closedHandCursor];
+  else
+    return [NSCursor arrowCursor];
+}
+
+@interface FlutterMouseCursorPlugin ()
+/**
+ * The channel used to communicate with Flutter.
+ */
+@property(nonatomic) FlutterMethodChannel* channel;
+
+/**
+ * Whether the cursor is currently hidden. 
+ */
+@property(nonatomic) BOOL hidden;
+
+@end
+
+@implementation FlutterMouseCursorPlugin
+
+- (instancetype)initWithChannel:(FlutterMethodChannel *)channel {
+  self = [super init];
+  if (self) {
+    _channel = channel;
+  }
+  return self;
+}
+
+#pragma mark - Private
+
+- (id)activateSystemCursor:(nonnull NSDictionary*)arguments {
+  if (!arguments) {
+    return [FlutterError
+        errorWithCode:@"error"
+              message:@"Missing arguments"
+              details:@"Missing arguments while trying to activate system cursor"];
+  }
+  NSString* kindArg = arguments[kKindKey];
+  NSNumber* deviceArg = arguments[kDeviceKey];
+  if (!kindArg || !deviceArg) {
+    return [FlutterError
+        errorWithCode:@"error"
+              message:@"Missing argument"
+              details:@"Missing argument while trying to activate system cursor"];
+  }
+  if ([kindArg isEqualToString:kKindValueNone]) {
+    [self hide];
+    return nil;
+  }
+  NSCursor* shapeObject = [FlutterMouseCursorPlugin resolveKindToCursor:kindArg];
+  [self activateShapeObject:shapeObject];
+  return nil;
+}
+
+- (void)activateShapeObject: (nonnull NSCursor *)targetShape {
+  [targetShape set];
+  if (_hidden) {
+    [NSCursor unhide];
+  }
+  _hidden = NO;
+}
+
+- (void)hide {
+  if (!_hidden) {
+    [NSCursor hide];
+  }
+  _hidden = YES;
+}
+
++ (NSCursor*)resolveKindToCursor:(NSString*)kind {
+  if (cachedSystemCursors == nil) {
+    cachedSystemCursors = [NSMutableDictionary dictionary];
+  }
+
+  NSCursor* cachedValue = [cachedSystemCursors objectForKey:kind];
+  if (cachedValue == nil) {
+    cachedValue = mapKindToCursor(kind);
+    [cachedSystemCursors setValue:cachedValue forKey:kind];
+  }
+  return cachedValue;
+}
+
+#pragma mark - FlutterPlugin implementation
+
++ (void)registerWithRegistrar:(id<FlutterPluginRegistrar>)registrar {
+  FlutterMethodChannel *channel = [FlutterMethodChannel methodChannelWithName:kMouseCursorChannel
+                                                              binaryMessenger:registrar.messenger];
+  FlutterMouseCursorPlugin *instance = [[FlutterMouseCursorPlugin alloc] initWithChannel:channel];
+  [registrar addMethodCallDelegate:instance channel:channel];
+}
+
+- (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)result {
+  NSString* method = call.method;
+  if ([method isEqualToString:kActivateSystemCursorMethod]) {
+    result([self activateSystemCursor:call.arguments]);
+  } else {
+    result(FlutterMethodNotImplemented);
+  }
+}
+
+@end

shell/platform/darwin/macos/framework/Source/FlutterViewController.mm

@@ -8,6 +8,7 @@
 #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/FlutterMouseCursorPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterEngine_Internal.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterTextInputPlugin.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterView.h"
@@ -350,6 +351,7 @@ - (void)configureTrackingArea {
 }
 
 - (void)addInternalPlugins {
+  [FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]];
   _textInputPlugin = [[FlutterTextInputPlugin alloc] initWithViewController:self];
   _keyEventChannel =
       [FlutterBasicMessageChannel messageChannelWithName:@"flutter/keyevent"