Introduce ThreadedInputConnection behind a switch

content/public/android/java/src/org/chromium/content/browser/input/ChromiumBaseInputConnectionFactory.java

Index: content/public/android/java/src/org/chromium/content/browser/input/ChromiumBaseInputConnectionFactory.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/input/ChromiumBaseInputConnectionFactory.java b/content/public/android/java/src/org/chromium/content/browser/input/ChromiumBaseInputConnectionFactory.java
new file mode 100644
index 0000000000000000000000000000000000000000..04734f35a6ff9b45a21a083f63c317ed99bffaf1
--- /dev/null
+++ b/content/public/android/java/src/org/chromium/content/browser/input/ChromiumBaseInputConnectionFactory.java
@@ -0,0 +1,153 @@
+// Copyright 2015 The Chromium 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 org.chromium.content.browser.input;
+
+import android.content.Context;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+import android.os.MessageQueue;
+import android.text.Editable;
+import android.view.View;
+import android.view.inputmethod.EditorInfo;
+import android.view.inputmethod.InputMethodManager;
+
+import org.chromium.base.CommandLine;
+import org.chromium.base.Log;
+import org.chromium.content.common.ContentSwitches;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+
+/**
+ * Default factory for ChromiumBaseInputConnection classes.
+ */
+public class ChromiumBaseInputConnectionFactory {
+    private static final String TAG = "cr.Ime";
+
+    private ChromiumInputConnection mChromiumInputConnection;
+    private View mView;

[aelias_OOO_until_Jul13, 2015/09/30 00:10:03]

This member variable is only used to recreate if the View has changed.  I'm not
convinced this is really needed, what use case does it cover?  The comment for
ContentViewCore.setContainerView() says the View should basically only change
for fullscreen WebView video, not clear whether this is relevant for IME?  If
there's no clear reason why you put this here, could this be deleted and just
say if (mChromiumInputConnection == null)?

[Changwan Ryu, 2016/01/19 07:31:53]

Removed and moved the logic up to ImeAdapter.

+
+    public ChromiumBaseInputConnection get(
+            View view, ImeAdapter imeAdapter, Editable editable, EditorInfo outAttrs) {
+        if (CommandLine.getInstance().hasSwitch(ContentSwitches.USE_IME_THREAD)) {
+            ImeUtils.assertOnUiThread();
+            if (mChromiumInputConnection == null || view != mView) {
+                Log.w(TAG, "Creating ChromiumInputConnection...");
+                mChromiumInputConnection = new ChromiumInputConnection(view, imeAdapter);
+                ImeUtils.assertReally("View: " + view, mView == null || view == mView);
+                mView = view;
+            }
+            mChromiumInputConnection.reset();
+            mChromiumInputConnection.updateEditorInfo(
+                    outAttrs, imeAdapter.getTextInputType(), imeAdapter.getTextInputFlags());
+            switchInputConnectionLooper(view.getContext(), view.getHandler());
+            return mChromiumInputConnection;
+        } else {
+            return new AdapterInputConnection(view, imeAdapter, editable, outAttrs);
+        }
+    }
+
+    /**
+     * Pump messages from a handler and add them to another handler.
+     *
+     * @param sourceHandler The source handler.
+     * @param targetHandler The target handler.
+     * @throws NoSuchFieldException
+     * @throws IllegalAccessException
+     * @throws IllegalArgumentException
+     */
+    private void pumpHandlerMessages(Handler sourceHandler, Handler targetHandler)
+            throws NoSuchFieldException, IllegalAccessException, IllegalArgumentException {
+        MessageQueue queue = sourceHandler.getLooper().getQueue();
+        Field messagesField = MessageQueue.class.getDeclaredField("mMessages");
+        Field nextField = Message.class.getDeclaredField("next");
+
+        synchronized (queue) {
+            // Copy messages first.
+            messagesField.setAccessible(true);
+            nextField.setAccessible(true);
+            Message msg = (Message) messagesField.get(queue);
+            while (msg != null) {
+                if (msg.getTarget() == sourceHandler) {
+                    Log.d(TAG, "Copying a message to the new handler...");
+                    Message newMsg = targetHandler.obtainMessage();
+                    newMsg.copyFrom(msg);
+                    targetHandler.sendMessage(newMsg);
+                }
+                msg = (Message) nextField.get(msg);
+            }
+            messagesField.setAccessible(false);
+            nextField.setAccessible(false);
+
+            // Now remove messages from the first handler.
+            sourceHandler.removeCallbacksAndMessages(null);

[aelias_OOO_until_Jul13, 2015/09/18 04:59:30]

Is there any signal we can use to filter for IME-related messages?  I'm worried
some non-input message may end up getting forwarded from here.

[Changwan Ryu, 2015/09/18 07:34:59]

This removes callbacks and messages that belong to this handler only, and this
handler is only used for IME messages
(inputMethodManager.mServedInputConnectionWrapper.mH), so I think it's safe.

+        }
+    }
+
+    /**
+     * Switch the looper in InputMethodManager so that future calls to InputConnection
+     * can run in IME thread.
+     * TODO(changwan): add more description
+     *
+     * @param context
+     * @param viewHandler
+     */
+    private void switchInputConnectionLooper(Context context, Handler viewHandler) {

[Changwan Ryu, 2015/09/17 06:58:01]

Alex, this is the logic that implements the idea we discussed on Tuesday. It
still needs a failover mechanism (i.e. restart with AdapterInputConnection on
failure), but could you take a look and check if this makes sense?

+        Log.d(TAG, "switchInputConnectionLooper");
+        // Retrieve the same singleton instance of InputMethodManager that called
+        // onCreateInputConnection().
+        final InputMethodManager inputMethodManager =
+                (InputMethodManager) context.getSystemService(Context.INPUT_METHOD_SERVICE);
+        final Handler icHandler = InputConnectionHandlerFactory.getInputConnectionHandler();
+        viewHandler.post(new Runnable() {
+            @Override
+            public void run() {
+                Log.d(TAG, "switchInputConnectionLooper: replacing looper and handler");
+                try {
+                    // inputMethodManager.mServedInputConnectionWrapper.mMainLooper =
+                    // icHandler.getLooper();
+                    Field inputConnectionWrapperField = InputMethodManager.class.getDeclaredField(
+                            "mServedInputConnectionWrapper");
+                    inputConnectionWrapperField.setAccessible(true);
+                    Object inputConnectionWrapper =
+                            inputConnectionWrapperField.get(inputMethodManager);
+                    Class<?> iinputConnectionWrapperClass =
+                            Class.forName("com.android.internal.view.IInputConnectionWrapper");
+                    Field looperField =
+                            iinputConnectionWrapperClass.getDeclaredField("mMainLooper");
+                    looperField.setAccessible(true);
+                    looperField.set(inputConnectionWrapper, icHandler.getLooper());
+                    looperField.setAccessible(false);
+
+                    // inputMethodManager.mServedInputConnectionWrapper.mH =
+                    //         new IInputConnectionWrapper.MyHandler(icHandler.getLooper());
+                    Class<?> myHandlerClass = Class.forName(
+                            "com.android.internal.view.IInputConnectionWrapper$MyHandler");
+                    Constructor<?> ctor = myHandlerClass.getDeclaredConstructor(
+                            iinputConnectionWrapperClass, Looper.class);
+                    ctor.setAccessible(true);
+                    Handler myHandler = (Handler) ctor.newInstance(
+                            inputConnectionWrapper, icHandler.getLooper());
+                    Field handlerField = iinputConnectionWrapperClass.getDeclaredField("mH");
+                    ctor.setAccessible(false);
+                    handlerField.setAccessible(true);
+                    Handler oldHandler = (Handler) handlerField.get(inputConnectionWrapper);
+                    handlerField.set(inputConnectionWrapper, myHandler);
+                    handlerField.setAccessible(false);
+
+                    pumpHandlerMessages(oldHandler, myHandler);
+                } catch (IllegalAccessException | IllegalArgumentException | NoSuchFieldException
+                        | ClassNotFoundException | NoSuchMethodException | InstantiationException
+                        | InvocationTargetException | NullPointerException e) {
+                    e.printStackTrace();
+                    return;
+                }
+                Log.d(TAG, "switchInputConnectionLooper: replacing done.");
+            }
+        });
+    }
+}