Scribe (Android stylus handwriting text input) (#52943)

The engine API for Android's Scribe stylus handwriting input. Just bare bones handwriting itself, does not support special gestures, which will come in subsequent PR(s).

Author: justinmc

ci/licenses_golden/licenses_flutter

@@ -44294,6 +44294,7 @@ ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/syst
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/PlatformViewsChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/ProcessTextChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/RestorationChannel.java + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/ScribeChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/SpellCheckChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/SystemChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/common/ActivityLifecycleListener.java + ../../../flutter/LICENSE
@@ -44317,6 +44318,7 @@ ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/Flutte
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/ImeSyncDeferringInsetsCallback.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/InputConnectionAdaptor.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/ListenableEditingState.java + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/ScribePlugin.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/SpellCheckPlugin.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextEditingDelta.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextInputPlugin.java + ../../../flutter/LICENSE
@@ -47176,6 +47178,7 @@ 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/ProcessTextChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/RestorationChannel.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/ScribeChannel.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
@@ -47202,6 +47205,7 @@ 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/ScribePlugin.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

shell/platform/android/BUILD.gn

@@ -294,6 +294,7 @@ android_java_sources = [
   "io/flutter/embedding/engine/systemchannels/PlatformViewsChannel.java",
   "io/flutter/embedding/engine/systemchannels/ProcessTextChannel.java",
   "io/flutter/embedding/engine/systemchannels/RestorationChannel.java",
+  "io/flutter/embedding/engine/systemchannels/ScribeChannel.java",
   "io/flutter/embedding/engine/systemchannels/SettingsChannel.java",
   "io/flutter/embedding/engine/systemchannels/SpellCheckChannel.java",
   "io/flutter/embedding/engine/systemchannels/SystemChannel.java",
@@ -320,6 +321,7 @@ 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/ScribePlugin.java",
   "io/flutter/plugin/editing/SpellCheckPlugin.java",
   "io/flutter/plugin/editing/TextEditingDelta.java",
   "io/flutter/plugin/editing/TextInputPlugin.java",

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

@@ -63,6 +63,7 @@
 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.ScribePlugin;
 import io.flutter.plugin.editing.SpellCheckPlugin;
 import io.flutter.plugin.editing.TextInputPlugin;
 import io.flutter.plugin.localization.LocalizationPlugin;
@@ -133,6 +134,7 @@ public class FlutterView extends FrameLayout
   @Nullable private MouseCursorPlugin mouseCursorPlugin;
   @Nullable private TextInputPlugin textInputPlugin;
   @Nullable private SpellCheckPlugin spellCheckPlugin;
+  @Nullable private ScribePlugin scribePlugin;
   @Nullable private LocalizationPlugin localizationPlugin;
   @Nullable private KeyboardManager keyboardManager;
   @Nullable private AndroidTouchProcessor androidTouchProcessor;
@@ -1120,10 +1122,12 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
     if (Build.VERSION.SDK_INT >= API_LEVELS.API_24) {
       mouseCursorPlugin = new MouseCursorPlugin(this, this.flutterEngine.getMouseCursorChannel());
     }
+
     textInputPlugin =
         new TextInputPlugin(
             this,
             this.flutterEngine.getTextInputChannel(),
+            this.flutterEngine.getScribeChannel(),
             this.flutterEngine.getPlatformViewsController());
 
     try {
@@ -1136,6 +1140,10 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
       Log.e(TAG, "TextServicesManager not supported by device, spell check disabled.");
     }
 
+    scribePlugin =
+        new ScribePlugin(
+            this, textInputPlugin.getInputMethodManager(), this.flutterEngine.getScribeChannel());
+
     localizationPlugin = this.flutterEngine.getLocalizationPlugin();
 
     keyboardManager = new KeyboardManager(this);

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

@@ -34,6 +34,7 @@
 import io.flutter.embedding.engine.systemchannels.PlatformChannel;
 import io.flutter.embedding.engine.systemchannels.ProcessTextChannel;
 import io.flutter.embedding.engine.systemchannels.RestorationChannel;
+import io.flutter.embedding.engine.systemchannels.ScribeChannel;
 import io.flutter.embedding.engine.systemchannels.SettingsChannel;
 import io.flutter.embedding.engine.systemchannels.SpellCheckChannel;
 import io.flutter.embedding.engine.systemchannels.SystemChannel;
@@ -100,6 +101,7 @@ public class FlutterEngine implements ViewUtils.DisplayUpdater {
   @NonNull private final RestorationChannel restorationChannel;
   @NonNull private final PlatformChannel platformChannel;
   @NonNull private final ProcessTextChannel processTextChannel;
+  @NonNull private final ScribeChannel scribeChannel;
   @NonNull private final SettingsChannel settingsChannel;
   @NonNull private final SpellCheckChannel spellCheckChannel;
   @NonNull private final SystemChannel systemChannel;
@@ -337,6 +339,7 @@ public FlutterEngine(
     platformChannel = new PlatformChannel(dartExecutor);
     processTextChannel = new ProcessTextChannel(dartExecutor, context.getPackageManager());
     restorationChannel = new RestorationChannel(dartExecutor, waitForRestorationData);
+    scribeChannel = new ScribeChannel(dartExecutor);
     settingsChannel = new SettingsChannel(dartExecutor);
     spellCheckChannel = new SpellCheckChannel(dartExecutor);
     systemChannel = new SystemChannel(dartExecutor);
@@ -610,6 +613,12 @@ public TextInputChannel getTextInputChannel() {
     return textInputChannel;
   }
 
+  /** System channel that sends and receives Scribe requests and results. */
+  @NonNull
+  public ScribeChannel getScribeChannel() {
+    return scribeChannel;
+  }
+
   /** System channel that sends and receives spell check requests and results. */
   @NonNull
   public SpellCheckChannel getSpellCheckChannel() {

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

@@ -0,0 +1,147 @@
+// 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 static io.flutter.Build.API_LEVELS;
+
+import android.annotation.TargetApi;
+import android.os.Build;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
+import androidx.annotation.VisibleForTesting;
+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;
+
+/**
+ * {@link ScribeChannel} is a platform channel that is used by the framework to facilitate the
+ * Scribe handwriting text input feature.
+ */
+public class ScribeChannel {
+  private static final String TAG = "ScribeChannel";
+
+  @VisibleForTesting
+  public static final String METHOD_IS_FEATURE_AVAILABLE = "Scribe.isFeatureAvailable";
+
+  @VisibleForTesting
+  public static final String METHOD_IS_STYLUS_HANDWRITING_AVAILABLE =
+      "Scribe.isStylusHandwritingAvailable";
+
+  @VisibleForTesting
+  public static final String METHOD_START_STYLUS_HANDWRITING = "Scribe.startStylusHandwriting";
+
+  public final MethodChannel channel;
+  private ScribeMethodHandler scribeMethodHandler;
+
+  @NonNull
+  public final MethodChannel.MethodCallHandler parsingMethodHandler =
+      new MethodChannel.MethodCallHandler() {
+        @Override
+        public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+          if (scribeMethodHandler == null) {
+            Log.v(TAG, "No ScribeMethodHandler registered. Scribe call not handled.");
+            return;
+          }
+          String method = call.method;
+          Log.v(TAG, "Received '" + method + "' message.");
+          switch (method) {
+            case METHOD_IS_FEATURE_AVAILABLE:
+              isFeatureAvailable(call, result);
+              break;
+            case METHOD_IS_STYLUS_HANDWRITING_AVAILABLE:
+              isStylusHandwritingAvailable(call, result);
+              break;
+            case METHOD_START_STYLUS_HANDWRITING:
+              startStylusHandwriting(call, result);
+              break;
+            default:
+              result.notImplemented();
+              break;
+          }
+        }
+      };
+
+  private void isFeatureAvailable(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+    try {
+      final boolean isAvailable = scribeMethodHandler.isFeatureAvailable();
+      result.success(isAvailable);
+    } catch (IllegalStateException exception) {
+      result.error("error", exception.getMessage(), null);
+    }
+  }
+
+  private void isStylusHandwritingAvailable(
+      @NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+    if (Build.VERSION.SDK_INT < API_LEVELS.API_34) {
+      result.error("error", "Requires API level 34 or higher.", null);
+      return;
+    }
+
+    try {
+      final boolean isAvailable = scribeMethodHandler.isStylusHandwritingAvailable();
+      result.success(isAvailable);
+    } catch (IllegalStateException exception) {
+      result.error("error", exception.getMessage(), null);
+    }
+  }
+
+  private void startStylusHandwriting(
+      @NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+    if (Build.VERSION.SDK_INT < API_LEVELS.API_33) {
+      result.error("error", "Requires API level 33 or higher.", null);
+      return;
+    }
+
+    try {
+      scribeMethodHandler.startStylusHandwriting();
+      result.success(null);
+    } catch (IllegalStateException exception) {
+      result.error("error", exception.getMessage(), null);
+    }
+  }
+
+  public ScribeChannel(@NonNull DartExecutor dartExecutor) {
+    channel = new MethodChannel(dartExecutor, "flutter/scribe", JSONMethodCodec.INSTANCE);
+    channel.setMethodCallHandler(parsingMethodHandler);
+  }
+
+  /**
+   * Sets the {@link ScribeMethodHandler} which receives all requests for scribe sent through this
+   * channel.
+   */
+  public void setScribeMethodHandler(@Nullable ScribeMethodHandler scribeMethodHandler) {
+    this.scribeMethodHandler = scribeMethodHandler;
+  }
+
+  public interface ScribeMethodHandler {
+    /**
+     * Responds to the {@code result} with success and a boolean indicating whether or not stylus
+     * handwriting is available.
+     */
+    boolean isFeatureAvailable();
+
+    /**
+     * Responds to the {@code result} with success and a boolean indicating whether or not stylus
+     * handwriting is available.
+     */
+    @TargetApi(API_LEVELS.API_34)
+    @RequiresApi(API_LEVELS.API_34)
+    boolean isStylusHandwritingAvailable();
+
+    /**
+     * Requests to start Scribe stylus handwriting, which will respond to the {@code result} with
+     * either success if handwriting input has started or error otherwise.
+     */
+    @TargetApi(API_LEVELS.API_33)
+    @RequiresApi(API_LEVELS.API_33)
+    void startStylusHandwriting();
+  }
+
+  // TODO(justinmc): Scribe stylus gestures should be supported here.
+  // https://github.com/flutter/flutter/issues/156018
+}

shell/platform/android/io/flutter/plugin/editing/InputConnectionAdaptor.java

@@ -33,6 +33,7 @@
 import androidx.core.view.inputmethod.InputConnectionCompat;
 import io.flutter.Log;
 import io.flutter.embedding.engine.FlutterJNI;
+import io.flutter.embedding.engine.systemchannels.ScribeChannel;
 import io.flutter.embedding.engine.systemchannels.TextInputChannel;
 import java.io.ByteArrayOutputStream;
 import java.io.FileNotFoundException;
@@ -51,6 +52,7 @@ public interface KeyboardDelegate {
 
   private final View mFlutterView;
   private final int mClient;
+  private final ScribeChannel scribeChannel;
   private final TextInputChannel textInputChannel;
   private final ListenableEditingState mEditable;
   private final EditorInfo mEditorInfo;
@@ -69,6 +71,7 @@ public InputConnectionAdaptor(
       View view,
       int client,
       TextInputChannel textInputChannel,
+      ScribeChannel scribeChannel,
       KeyboardDelegate keyboardDelegate,
       ListenableEditingState editable,
       EditorInfo editorInfo,
@@ -77,6 +80,7 @@ public InputConnectionAdaptor(
     mFlutterView = view;
     mClient = client;
     this.textInputChannel = textInputChannel;
+    this.scribeChannel = scribeChannel;
     mEditable = editable;
     mEditable.addEditingStateListener(this);
     mEditorInfo = editorInfo;
@@ -100,10 +104,19 @@ public InputConnectionAdaptor(
       View view,
       int client,
       TextInputChannel textInputChannel,
+      ScribeChannel scribeChannel,
       KeyboardDelegate keyboardDelegate,
       ListenableEditingState editable,
       EditorInfo editorInfo) {
-    this(view, client, textInputChannel, keyboardDelegate, editable, editorInfo, new FlutterJNI());
+    this(
+        view,
+        client,
+        textInputChannel,
+        scribeChannel,
+        keyboardDelegate,
+        editable,
+        editorInfo,
+        new FlutterJNI());
   }
 
   private ExtractedText getExtractedText(ExtractedTextRequest request) {
@@ -262,6 +275,10 @@ public boolean setSelection(int start, int end) {
     return result;
   }
 
+  // TODO(justinmc): Scribe stylus gestures should be supported here via
+  // performHandwritingGesture.
+  // https://github.com/flutter/flutter/issues/156018
+
   // Sanitizes the index to ensure the index is within the range of the
   // contents of editable.
   private static int clampIndexToEditable(int index, Editable editable) {