Add Spell Check Support for Android Engine (#30858)

Author: camsim99

ci/licenses_golden/licenses_flutter

@@ -1400,6 +1400,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/system
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/PlatformViewsChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/RestorationChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/SettingsChannel.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/SpellCheckChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/SystemChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/TextInputChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/common/ActivityLifecycleListener.java
@@ -1424,6 +1425,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/FlutterT
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/ImeSyncDeferringInsetsCallback.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/InputConnectionAdaptor.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/ListenableEditingState.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/SpellCheckPlugin.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextEditingDelta.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextInputPlugin.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/localization/LocalizationPlugin.java

lib/ui/platform_dispatcher.dart

@@ -842,6 +842,14 @@ class PlatformDispatcher {
     _onTextScaleFactorChangedZone = Zone.current;
   }
 
+  /// Whether the spell check service is supported on the current platform.
+  ///
+  /// This option is used by [EditableTextState] to define its
+  /// [SpellCheckConfiguration] when a default spell check service
+  /// is requested.
+  bool get nativeSpellCheckServiceDefined => _nativeSpellCheckServiceDefined;
+  bool _nativeSpellCheckServiceDefined = false;
+
   /// Whether briefly displaying the characters as you type in obscured text
   /// fields is enabled in system settings.
   ///
@@ -903,6 +911,12 @@ class PlatformDispatcher {
 
     final double textScaleFactor = (data['textScaleFactor']! as num).toDouble();
     final bool alwaysUse24HourFormat = data['alwaysUse24HourFormat']! as bool;
+    final bool? nativeSpellCheckServiceDefined = data['nativeSpellCheckServiceDefined'] as bool?;
+    if (nativeSpellCheckServiceDefined != null) {
+      _nativeSpellCheckServiceDefined = nativeSpellCheckServiceDefined;
+    } else {
+      _nativeSpellCheckServiceDefined = false;
+    }
     // This field is optional.
     final bool? brieflyShowPassword = data['brieflyShowPassword'] as bool?;
     if (brieflyShowPassword != null) {

lib/ui/window.dart

@@ -425,6 +425,15 @@ class SingletonFlutterWindow extends FlutterWindow {
   ///    observe when this value changes.
   double get textScaleFactor => platformDispatcher.textScaleFactor;
 
+  /// Whether the spell check service is supported on the current platform.
+  ///
+  /// {@macro dart.ui.window.accessorForwardWarning}
+  ///
+  /// This option is used by [EditableTextState] to define its
+  /// [SpellCheckConfiguration] when spell check is enabled, but no spell check
+  /// service is specified.
+  bool get nativeSpellCheckServiceDefined => platformDispatcher.nativeSpellCheckServiceDefined;
+
   /// Whether briefly displaying the characters as you type in obscured text
   /// fields is enabled in system settings.
   ///

lib/web_ui/lib/platform_dispatcher.dart

@@ -82,6 +82,8 @@ abstract class PlatformDispatcher {
 
   double get textScaleFactor => configuration.textScaleFactor;
 
+  bool get nativeSpellCheckServiceDefined => false;
+
   bool get brieflyShowPassword => true;
 
   VoidCallback? get onTextScaleFactorChanged;

lib/web_ui/lib/window.dart

@@ -48,6 +48,8 @@ abstract class SingletonFlutterWindow extends FlutterWindow {
 
   double get textScaleFactor => platformDispatcher.textScaleFactor;
 
+  bool get nativeSpellCheckServiceDefined => platformDispatcher.nativeSpellCheckServiceDefined;
+
   bool get brieflyShowPassword => platformDispatcher.brieflyShowPassword;
 
   bool get alwaysUse24HourFormat => platformDispatcher.alwaysUse24HourFormat;

shell/platform/android/BUILD.gn

@@ -236,6 +236,7 @@ android_java_sources = [
   "io/flutter/embedding/engine/systemchannels/PlatformViewsChannel.java",
   "io/flutter/embedding/engine/systemchannels/RestorationChannel.java",
   "io/flutter/embedding/engine/systemchannels/SettingsChannel.java",
+  "io/flutter/embedding/engine/systemchannels/SpellCheckChannel.java",
   "io/flutter/embedding/engine/systemchannels/SystemChannel.java",
   "io/flutter/embedding/engine/systemchannels/TextInputChannel.java",
   "io/flutter/plugin/common/ActivityLifecycleListener.java",
@@ -260,6 +261,7 @@ android_java_sources = [
   "io/flutter/plugin/editing/ImeSyncDeferringInsetsCallback.java",
   "io/flutter/plugin/editing/InputConnectionAdaptor.java",
   "io/flutter/plugin/editing/ListenableEditingState.java",
+  "io/flutter/plugin/editing/SpellCheckPlugin.java",
   "io/flutter/plugin/editing/TextEditingDelta.java",
   "io/flutter/plugin/editing/TextInputPlugin.java",
   "io/flutter/plugin/localization/LocalizationPlugin.java",

shell/platform/android/io/flutter/embedding/android/FlutterView.java

@@ -35,6 +35,8 @@
 import android.view.autofill.AutofillValue;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
+import android.view.textservice.SpellCheckerInfo;
+import android.view.textservice.TextServicesManager;
 import android.widget.FrameLayout;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -58,6 +60,7 @@
 import io.flutter.embedding.engine.renderer.RenderSurface;
 import io.flutter.embedding.engine.systemchannels.SettingsChannel;
 import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.editing.SpellCheckPlugin;
 import io.flutter.plugin.editing.TextInputPlugin;
 import io.flutter.plugin.localization.LocalizationPlugin;
 import io.flutter.plugin.mouse.MouseCursorPlugin;
@@ -126,10 +129,12 @@ public class FlutterView extends FrameLayout
   // existing, stateless system channels, e.g., MouseCursorChannel, TextInputChannel, etc.
   @Nullable private MouseCursorPlugin mouseCursorPlugin;
   @Nullable private TextInputPlugin textInputPlugin;
+  @Nullable private SpellCheckPlugin spellCheckPlugin;
   @Nullable private LocalizationPlugin localizationPlugin;
   @Nullable private KeyboardManager keyboardManager;
   @Nullable private AndroidTouchProcessor androidTouchProcessor;
   @Nullable private AccessibilityBridge accessibilityBridge;
+  @Nullable private TextServicesManager textServicesManager;
 
   // Provides access to foldable/hinge information
   @Nullable private WindowInfoRepositoryCallbackAdapterWrapper windowInfoRepo;
@@ -1141,6 +1146,17 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
             this,
             this.flutterEngine.getTextInputChannel(),
             this.flutterEngine.getPlatformViewsController());
+
+    try {
+      textServicesManager =
+          (TextServicesManager)
+              getContext().getSystemService(Context.TEXT_SERVICES_MANAGER_SERVICE);
+      spellCheckPlugin =
+          new SpellCheckPlugin(textServicesManager, this.flutterEngine.getSpellCheckChannel());
+    } catch (Exception e) {
+      Log.e(TAG, "TextServicesManager not supported by device, spell check disabled.");
+    }
+
     localizationPlugin = this.flutterEngine.getLocalizationPlugin();
 
     keyboardManager = new KeyboardManager(this);
@@ -1238,6 +1254,9 @@ public void detachFromFlutterEngine() {
     textInputPlugin.getInputMethodManager().restartInput(this);
     textInputPlugin.destroy();
     keyboardManager.destroy();
+    if (spellCheckPlugin != null) {
+      spellCheckPlugin.destroy();
+    }
 
     if (mouseCursorPlugin != null) {
       mouseCursorPlugin.destroy();
@@ -1422,10 +1441,34 @@ public void removeFlutterEngineAttachmentListener(
             ? SettingsChannel.PlatformBrightness.dark
             : SettingsChannel.PlatformBrightness.light;
 
+    boolean isNativeSpellCheckServiceDefined = false;
+
+    if (textServicesManager != null) {
+      if (Build.VERSION.SDK_INT >= 31) {
+        List<SpellCheckerInfo> enabledSpellCheckerInfos =
+            textServicesManager.getEnabledSpellCheckerInfos();
+        boolean gboardSpellCheckerEnabled =
+            enabledSpellCheckerInfos.stream()
+                .anyMatch(
+                    spellCheckerInfo ->
+                        spellCheckerInfo
+                            .getPackageName()
+                            .equals("com.google.android.inputmethod.latin"));
+
+        // Checks if enabled spell checker is the one that is suppported by Gboard, which is
+        // the one Flutter supports by default.
+        isNativeSpellCheckServiceDefined =
+            textServicesManager.isSpellCheckerEnabled() && gboardSpellCheckerEnabled;
+      } else {
+        isNativeSpellCheckServiceDefined = true;
+      }
+    }
+
     flutterEngine
         .getSettingsChannel()
         .startMessage()
         .setTextScaleFactor(getResources().getConfiguration().fontScale)
+        .setNativeSpellCheckServiceDefined(isNativeSpellCheckServiceDefined)
         .setBrieflyShowPassword(
             Settings.System.getInt(
                     getContext().getContentResolver(), Settings.System.TEXT_SHOW_PASSWORD, 1)

shell/platform/android/io/flutter/embedding/engine/FlutterEngine.java

@@ -32,6 +32,7 @@
 import io.flutter.embedding.engine.systemchannels.PlatformChannel;
 import io.flutter.embedding.engine.systemchannels.RestorationChannel;
 import io.flutter.embedding.engine.systemchannels.SettingsChannel;
+import io.flutter.embedding.engine.systemchannels.SpellCheckChannel;
 import io.flutter.embedding.engine.systemchannels.SystemChannel;
 import io.flutter.embedding.engine.systemchannels.TextInputChannel;
 import io.flutter.plugin.localization.LocalizationPlugin;
@@ -93,6 +94,7 @@ public class FlutterEngine {
   @NonNull private final RestorationChannel restorationChannel;
   @NonNull private final PlatformChannel platformChannel;
   @NonNull private final SettingsChannel settingsChannel;
+  @NonNull private final SpellCheckChannel spellCheckChannel;
   @NonNull private final SystemChannel systemChannel;
   @NonNull private final TextInputChannel textInputChannel;
 
@@ -306,6 +308,7 @@ public FlutterEngine(
     platformChannel = new PlatformChannel(dartExecutor);
     restorationChannel = new RestorationChannel(dartExecutor, waitForRestorationData);
     settingsChannel = new SettingsChannel(dartExecutor);
+    spellCheckChannel = new SpellCheckChannel(dartExecutor);
     systemChannel = new SystemChannel(dartExecutor);
     textInputChannel = new TextInputChannel(dartExecutor);
 
@@ -550,6 +553,12 @@ public TextInputChannel getTextInputChannel() {
     return textInputChannel;
   }
 
+  /** System channel that sends and receives spell check requests and results. */
+  @NonNull
+  public SpellCheckChannel getSpellCheckChannel() {
+    return spellCheckChannel;
+  }
+
   /**
    * Plugin registry, which registers plugins that want to be applied to this {@code FlutterEngine}.
    */

shell/platform/android/io/flutter/embedding/engine/systemchannels/SettingsChannel.java

@@ -13,6 +13,7 @@ public class SettingsChannel {
 
   public static final String CHANNEL_NAME = "flutter/settings";
   private static final String TEXT_SCALE_FACTOR = "textScaleFactor";
+  private static final String NATIVE_SPELL_CHECK_SERVICE_DEFINED = "nativeSpellCheckServiceDefined";
   private static final String BRIEFLY_SHOW_PASSWORD = "brieflyShowPassword";
   private static final String ALWAYS_USE_24_HOUR_FORMAT = "alwaysUse24HourFormat";
   private static final String PLATFORM_BRIGHTNESS = "platformBrightness";
@@ -42,6 +43,13 @@ public MessageBuilder setTextScaleFactor(float textScaleFactor) {
       return this;
     }
 
+    @NonNull
+    public MessageBuilder setNativeSpellCheckServiceDefined(
+        boolean nativeSpellCheckServiceDefined) {
+      message.put(NATIVE_SPELL_CHECK_SERVICE_DEFINED, nativeSpellCheckServiceDefined);
+      return this;
+    }
+
     @NonNull
     public MessageBuilder setBrieflyShowPassword(@NonNull boolean brieflyShowPassword) {
       message.put(BRIEFLY_SHOW_PASSWORD, brieflyShowPassword);

shell/platform/android/io/flutter/embedding/engine/systemchannels/SpellCheckChannel.java

@@ -0,0 +1,101 @@
+// 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.
+
+package io.flutter.embedding.engine.systemchannels;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import io.flutter.Log;
+import io.flutter.embedding.engine.dart.DartExecutor;
+import io.flutter.plugin.common.JSONMethodCodec;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+import org.json.JSONArray;
+import org.json.JSONException;
+
+/**
+ * {@link SpellCheckChannel} is a platform channel that is used by the framework to initiate spell
+ * check in the embedding and for the embedding to send back the results.
+ *
+ * <p>When there is new text to be spell checked, the framework will send to the embedding the
+ * message {@code SpellCheck.initiateSpellCheck} with the {@code String} locale to spell check with
+ * and the {@code String} of text to spell check as arguments. In response, the {@link
+ * io.flutter.plugin.editing.SpellCheckPlugin} will make a call to Android's spell check service to
+ * fetch spell check results for the specified text.
+ *
+ * <p>Once the spell check results are received by the {@link
+ * io.flutter.plugin.editing.SpellCheckPlugin}, it will send to the framework the message {@code
+ * SpellCheck.updateSpellCheckResults} with the {@code ArrayList<String>} of encoded spell check
+ * results (see {@link
+ * io.flutter.plugin.editing.SpellCheckPlugin#onGetSentenceSuggestions(SentenceSuggestionsInfo[])}
+ * for details) with the text that these results correspond to appeneded to the front as an
+ * argument. For example, the argument may look like: {@code {"Hello, wrold!",
+ * "7.11.world\nword\nold"}}.
+ *
+ * <p>{@link io.flutter.plugin.editing.SpellCheckPlugin} implements {@link SpellCheckMethodHandler}
+ * to initiate spell check. Implement {@link SpellCheckMethodHandler} to respond to spell check
+ * requests.
+ */
+public class SpellCheckChannel {
+  private static final String TAG = "SpellCheckChannel";
+
+  public final MethodChannel channel;
+  private SpellCheckMethodHandler spellCheckMethodHandler;
+
+  @NonNull
+  public final MethodChannel.MethodCallHandler parsingMethodHandler =
+      new MethodChannel.MethodCallHandler() {
+        @Override
+        public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+          if (spellCheckMethodHandler == null) {
+            Log.v(
+                TAG,
+                "No SpellCheckeMethodHandler registered, call not forwarded to spell check API.");
+            return;
+          }
+          String method = call.method;
+          Object args = call.arguments;
+          Log.v(TAG, "Received '" + method + "' message.");
+          switch (method) {
+            case "SpellCheck.initiateSpellCheck":
+              try {
+                final JSONArray argumentList = (JSONArray) args;
+                String locale = argumentList.getString(0);
+                String text = argumentList.getString(1);
+                spellCheckMethodHandler.initiateSpellCheck(locale, text, result);
+              } catch (JSONException exception) {
+                result.error("error", exception.getMessage(), null);
+              }
+              break;
+            default:
+              result.notImplemented();
+              break;
+          }
+        }
+      };
+
+  public SpellCheckChannel(@NonNull DartExecutor dartExecutor) {
+    channel = new MethodChannel(dartExecutor, "flutter/spellcheck", JSONMethodCodec.INSTANCE);
+    channel.setMethodCallHandler(parsingMethodHandler);
+  }
+
+  /**
+   * Sets the {@link SpellCheckMethodHandler} which receives all requests to spell check the
+   * specified text sent through this channel.
+   */
+  public void setSpellCheckMethodHandler(
+      @Nullable SpellCheckMethodHandler spellCheckMethodHandler) {
+    this.spellCheckMethodHandler = spellCheckMethodHandler;
+  }
+
+  public interface SpellCheckMethodHandler {
+    /**
+     * Requests that spell check is initiated for the specified text, which will respond to the
+     * {@code result} with either success if spell check results are received or error if the
+     * request is skipped.
+     */
+    void initiateSpellCheck(
+        @NonNull String locale, @NonNull String text, @NonNull MethodChannel.Result result);
+  }
+}