From 6495e3c93be9e6908e3d3c50e02a3a4095fbc7fe Mon Sep 17 00:00:00 2001
From: Yohei Yukawa <yukawa@google.com>
Date: Thu, 20 Jan 2022 20:40:52 -0800
Subject: [PATCH] Clarify how IMMS#executeOrSendMessage() works

This CL attempts to clarify how

  InputMethodManagerService#executeOrSendMessage()

has been actually working, that is, probably to emulate oneway Binder
IPC semantics in case the target IInterface object is an in-process
Binder object, which is quite important to avoid dead-locks.

However, using it for IInputMethod objects is overkill because we have
never officially supported IMEs running in the system_server process.
There is no reason to define MSG_* for those cases.

As the initial step towards cleaning up those unnecessarily defined
switch cases, this CL introduces a new overload method

  InputMethodManagerService#executeOrSendMessage(IInputMethod, Message)

to make it clear that it always immediately invokes

  InputMethodManagerService#handleMessage()

if the target is IInputMethod.

The actual removal of

  InputMethodManagerService#executeOrSendMessage(IInputMethod, Message)

will be done through subsequent CLs.

To summarize, there should be no observable behavior change unless
someone is surprisingly running InputMethodService in the
system_server process.

Bug: 215609403
Test: presubmit
Change-Id: I0c4aab9a0974857e531be4fb1fc75980b36f4443
---
 .../InputMethodManagerService.java            | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
index ec49b4768b749..25cb11f905a1b 100644
--- a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
@@ -97,7 +97,6 @@ import android.os.Bundle;
 import android.os.Debug;
 import android.os.Handler;
 import android.os.IBinder;
-import android.os.IInterface;
 import android.os.LocaleList;
 import android.os.Message;
 import android.os.Parcel;
@@ -2216,8 +2215,24 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
         }
     }
 
-    private void executeOrSendMessage(IInterface target, Message msg) {
+    // TODO(b/215609403): This method will be removed soon!
+    private void executeOrSendMessage(IInputMethod target, Message msg) {
+        if (target.asBinder() instanceof Binder) {
+            throw new UnsupportedOperationException(
+                    "InputMethodService is not supported to run in the system_server");
+        }
+        handleMessage(msg);
+        msg.recycle();
+    }
+
+    private void executeOrSendMessage(IInputMethodClient target, Message msg) {
          if (target.asBinder() instanceof Binder) {
+             // This is supposed to be emulating the one-way semantics when the IME client is
+             // system_server itself, which has not been explicitly prohibited so far while we have
+             // never ever officially supported such a use case...
+             // We probably should create a simple wrapper of IInputMethodClient as the first step
+             // to get rid of executeOrSendMessage() then should prohibit system_server to be the
+             // IME client for long term.
              mCaller.sendMessage(msg);
          } else {
              handleMessage(msg);