[macOS] Reset keyboard states on engine restart (flutter#29283)

With this PR, the state of the keyboard system will be reset when the engine is reset (typically during a hot restart.)

shell/platform/android/io/flutter/view/FlutterNativeView.java

@@ -169,7 +169,7 @@ private void attach(FlutterNativeView view) {
   }
 
   private final class EngineLifecycleListenerImpl implements EngineLifecycleListener {
-    // Called by native to notify when the engine is restarted (cold reload).
+    // Called by native to notify right before the engine is restarted (cold reload).
     @SuppressWarnings("unused")
     public void onPreEngineRestart() {
       if (mFlutterView != null) {

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

@@ -53,4 +53,12 @@ FLUTTER_DARWIN_EXPORT
     NS_DESIGNATED_INITIALIZER;
 - (nonnull instancetype)initWithCoder:(nonnull NSCoder*)nibNameOrNil NS_DESIGNATED_INITIALIZER;
 
+/**
+ * Invoked by the engine right before the engine is restarted.
+ *
+ * This should reset states to as if the application has just started.  It
+ * usually indicates a hot restart (Shift-R in Flutter CLI.)
+ */
+- (void)onPreEngineRestart;
+
 @end

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

@@ -75,6 +75,14 @@ - (void)sendUserLocales;
  */
 - (void)engineCallbackOnPlatformMessage:(const FlutterPlatformMessage*)message;
 
+/**
+ * Invoked right before the engine is restarted.
+ *
+ * This should reset states to as if the application has just started.  It
+ * usually indicates a hot restart (Shift-R in Flutter CLI.)
+ */
+- (void)engineCallbackOnPreEngineRestart;
+
 /**
  * Requests that the task be posted back the to the Flutter engine at the target time. The target
  * time is in the clock used by the Flutter engine.
@@ -296,6 +304,11 @@ - (BOOL)runWithEntrypoint:(NSString*)entrypoint {
 
   flutterArguments.compositor = [self createFlutterCompositor];
 
+  flutterArguments.on_pre_engine_restart_callback = [](void* user_data) {
+    FlutterEngine* engine = (__bridge FlutterEngine*)user_data;
+    [engine engineCallbackOnPreEngineRestart];
+  };
+
   FlutterRendererConfig rendererConfig = [_renderer createRendererConfig];
   FlutterEngineResult result = _embedderAPI.Initialize(
       FLUTTER_ENGINE_VERSION, &rendererConfig, &flutterArguments, (__bridge void*)(self), &_engine);
@@ -584,6 +597,12 @@ - (void)engineCallbackOnPlatformMessage:(const FlutterPlatformMessage*)message {
   }
 }
 
+- (void)engineCallbackOnPreEngineRestart {
+  if (_viewController) {
+    [_viewController onPreEngineRestart];
+  }
+}
+
 /**
  * Note: Called from dealloc. Should not use accessors or other methods.
  */

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

@@ -186,7 +186,7 @@ - (instancetype)initWithViewController:(FlutterViewController*)viewController {
     [_channel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
       [unsafeSelf handleMethodCall:call result:result];
     }];
-    _textInputContext = [[NSTextInputContext alloc] initWithClient:self];
+    _textInputContext = [[NSTextInputContext alloc] initWithClient:unsafeSelf];
     _previouslyPressedFlags = 0;
 
     _flutterViewController = viewController;
@@ -208,6 +208,11 @@ - (BOOL)isFirstResponder {
 
 - (void)dealloc {
   [_channel setMethodCallHandler:nil];
+  if (_textInputContext) {
+    [_textInputContext deactivate];
+    [_textInputContext discardMarkedText];
+    _textInputContext = nil;
+  }
 }
 
 #pragma mark - Private

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

@@ -138,6 +138,11 @@ - (void)configureTrackingArea;
  */
 - (void)addInternalPlugins;
 
+/**
+ * Creates and registers keyboard related components.
+ */
+- (void)initializeKeyboard;
+
 /**
  * Calls dispatchMouseEvent:phase: with a phase determined by self.mouseState.
  *
@@ -358,6 +363,10 @@ - (void)setMouseTrackingMode:(FlutterMouseTrackingMode)mode {
   [self configureTrackingArea];
 }
 
+- (void)onPreEngineRestart {
+  [self initializeKeyboard];
+}
+
 #pragma mark - Private methods
 
 - (BOOL)launchEngine {
@@ -431,9 +440,9 @@ - (void)configureTrackingArea {
   }
 }
 
-- (void)addInternalPlugins {
+- (void)initializeKeyboard {
   __weak FlutterViewController* weakSelf = self;
-  [FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]];
+  _textInputPlugin = [[FlutterTextInputPlugin alloc] initWithViewController:weakSelf];
   _keyboardManager = [[FlutterKeyboardManager alloc] initWithOwner:weakSelf];
   [_keyboardManager addPrimaryResponder:[[FlutterEmbedderKeyResponder alloc]
                                             initWithSendEvent:^(const FlutterKeyEvent& event,
@@ -451,6 +460,12 @@ - (void)addInternalPlugins {
                                                                    codec:[FlutterJSONMessageCodec
                                                                              sharedInstance]]]];
   [_keyboardManager addSecondaryResponder:_textInputPlugin];
+}
+
+- (void)addInternalPlugins {
+  __weak FlutterViewController* weakSelf = self;
+  [FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]];
+  [self initializeKeyboard];
   _settingsChannel =
       [FlutterBasicMessageChannel messageChannelWithName:@"flutter/settings"
                                          binaryMessenger:_engine.binaryMessenger

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

@@ -20,6 +20,7 @@ - (bool)testKeyEventsArePropagatedIfNotHandled;
 - (bool)testKeyEventsAreNotPropagatedIfHandled;
 - (bool)testFlagsChangedEventsArePropagatedIfNotHandled;
 - (bool)testPerformKeyEquivalentSynthesizesKeyUp;
+- (bool)testKeyboardIsRestartedOnEngineRestart;
 
 + (void)respondFalseForSendEvent:(const FlutterKeyEvent&)event
                         callback:(nullable FlutterKeyEventCallback)callback
@@ -171,6 +172,10 @@ + (void)respondFalseForSendEvent:(const FlutterKeyEvent&)event
   ASSERT_TRUE([[FlutterViewControllerTestObjC alloc] testPerformKeyEquivalentSynthesizesKeyUp]);
 }
 
+TEST(FlutterViewControllerTest, TestKeyboardIsRestartedOnEngineRestart) {
+  ASSERT_TRUE([[FlutterViewControllerTestObjC alloc] testKeyboardIsRestartedOnEngineRestart]);
+}
+
 }  // namespace flutter::testing
 
 @implementation FlutterViewControllerTestObjC
@@ -456,6 +461,60 @@ - (bool)testPerformKeyEquivalentSynthesizesKeyUp {
   return true;
 }
 
+- (bool)testKeyboardIsRestartedOnEngineRestart {
+  id engineMock = OCMClassMock([FlutterEngine class]);
+  id binaryMessengerMock = OCMProtocolMock(@protocol(FlutterBinaryMessenger));
+  OCMStub(  // NOLINT(google-objc-avoid-throwing-exception)
+      [engineMock binaryMessenger])
+      .andReturn(binaryMessengerMock);
+  __block bool called = false;
+  __block FlutterKeyEvent last_event;
+  OCMStub([[engineMock ignoringNonObjectArgs] sendKeyEvent:FlutterKeyEvent {}
+                                                  callback:nil
+                                                  userData:nil])
+      .andDo((^(NSInvocation* invocation) {
+        FlutterKeyEvent* event;
+        [invocation getArgument:&event atIndex:2];
+        called = true;
+        last_event = *event;
+      }));
+
+  FlutterViewController* viewController = [[FlutterViewController alloc] initWithEngine:engineMock
+                                                                                nibName:@""
+                                                                                 bundle:nil];
+  [viewController viewWillAppear];
+  NSEvent* keyADown = [NSEvent keyEventWithType:NSEventTypeKeyDown
+                                       location:NSZeroPoint
+                                  modifierFlags:0x100
+                                      timestamp:0
+                                   windowNumber:0
+                                        context:nil
+                                     characters:@"a"
+                    charactersIgnoringModifiers:@"a"
+                                      isARepeat:FALSE
+                                        keyCode:0];
+  const uint64_t kPhysicalKeyA = 0x70004;
+
+  // Send KeyA key down event twice. Without restarting the keyboard during
+  // onPreEngineRestart, the second event received will be an empty event with
+  // physical key 0x0 because duplicate key down events are ignored.
+
+  called = false;
+  [viewController keyDown:keyADown];
+  EXPECT_TRUE(called);
+  EXPECT_EQ(last_event.type, kFlutterKeyEventTypeDown);
+  EXPECT_EQ(last_event.physical, kPhysicalKeyA);
+
+  [viewController onPreEngineRestart];
+
+  called = false;
+  [viewController keyDown:keyADown];
+  EXPECT_TRUE(called);
+  EXPECT_EQ(last_event.type, kFlutterKeyEventTypeDown);
+  EXPECT_EQ(last_event.physical, kPhysicalKeyA);
+  return true;
+}
+
 + (void)respondFalseForSendEvent:(const FlutterKeyEvent&)event
                         callback:(nullable FlutterKeyEventCallback)callback
                         userData:(nullable void*)userData {

shell/platform/embedder/embedder.h

@@ -1580,7 +1580,7 @@ typedef struct {
   // callbacks on `log_message_callback`. Defaults to "flutter" if unspecified.
   const char* log_tag;
 
-  // A callback that is invoked when the engine is restarted.
+  // A callback that is invoked right before the engine is restarted.
   //
   // This optional callback is typically used to reset states to as if the
   // engine has just been started, and usually indicates the user has requested

shell/platform/linux/fl_engine.cc

@@ -48,7 +48,7 @@ struct _FlEngine {
   gpointer update_semantics_node_handler_data;
   GDestroyNotify update_semantics_node_handler_destroy_notify;
 
-  // Function to call when the engine is restarted.
+  // Function to call right before the engine is restarted.
   FlEngineOnPreEngineRestartHandler on_pre_engine_restart_handler;
   gpointer on_pre_engine_restart_handler_data;
   GDestroyNotify on_pre_engine_restart_handler_destroy_notify;
@@ -284,7 +284,7 @@ static void fl_engine_update_semantics_node_cb(const FlutterSemanticsNode* node,
   }
 }
 
-// Called when the engine is restarted.
+// Called right before the engine is restarted.
 //
 // This method should reset states to as if the engine has just been started,
 // which usually indicates the user has requested a hot restart (Shift-R in the

shell/platform/linux/fl_engine_private.h

@@ -133,7 +133,7 @@ void fl_engine_set_update_semantics_node_handler(
  * @destroy_notify: (allow-none): a function which gets called to free
  * @user_data, or %NULL.
  *
- * Registers the function called when the engine is restarted.
+ * Registers the function called right before the engine is restarted.
  */
 void fl_engine_set_on_pre_engine_restart_handler(
     FlEngine* engine,

shell/platform/linux/fl_view.cc

@@ -102,7 +102,7 @@ static void fl_view_init_keyboard(FlView* self) {
       FL_KEY_RESPONDER(fl_key_channel_responder_new(messenger)));
 }
 
-// Called when the engine is restarted.
+// Invoked by the engine right before the engine is restarted.
 //
 // This method should reset states to be as if the engine had just been started,
 // which usually indicates the user has requested a hot restart (Shift-R in the

shell/platform/windows/flutter_windows_view.h

@@ -90,7 +90,7 @@ class FlutterWindowsView : public WindowBindingHandlerDelegate,
   // Returns the frame buffer id for the engine to render to.
   uint32_t GetFrameBufferId(size_t width, size_t height);
 
-  // Called when the engine is restarted.
+  // Invoked by the engine right before the engine is restarted.
   //
   // This should reset necessary states to as if the view has just been
   // created. This is typically caused by a hot restart (Shift-R in CLI.)