From 38be9e32f161828b3a8d3f4e0046af3213350622 Mon Sep 17 00:00:00 2001
From: Shan Huang <shanh@google.com>
Date: Mon, 21 Mar 2022 21:44:05 +0000
Subject: Migrate InputMethodService to use OnBackInvokedDispatcher

We currently close the IME by having the target application forward
KEYCODE_BACK to the IME process through InputMethodManager#dispatchInputEvent and having the IME handle the keycode in InputMethodService#onKeyDown. When apps opt in to OnBackInvokedDispatcher API, we will not dispatch KEYCODE_BACK to apps anymore. Thus we need to migrate IME to the new API for it to close on back invocation.

This CL migrates the client side IME code to register and unregister callbacks, and also updates the WM side logic to make sure IME callback priority works correctly with other application callbacks.

Test: In BackTestApp home activity, Show IME -> try swipe back. Open WidgetTestActivity, show IME by clicking on EditText -> try swipe back.
Test: Install Micrsoft SwiftKey. Set as primary IME. Repeat the above
steps in BackTestApp and make sure IME behaves correctly.

Bug: 228358882

Change-Id: Idb246cf1858a7515f6fc34a5ccde33f25f56d404
---
 .../inputmethodservice/InputMethodService.java     | 60 ++++++++++++++++++++++
 1 file changed, 60 insertions(+)

(limited to 'core/java/android/inputmethodservice/InputMethodService.java')

diff --git a/core/java/android/inputmethodservice/InputMethodService.java b/core/java/android/inputmethodservice/InputMethodService.java
index 4fdd53425328..6ece5efae537 100644
--- a/core/java/android/inputmethodservice/InputMethodService.java
+++ b/core/java/android/inputmethodservice/InputMethodService.java
@@ -101,6 +101,7 @@ import android.view.BatchedInputEventReceiver.SimpleBatchedInputEventReceiver;
 import android.view.Choreographer;
 import android.view.Gravity;
 import android.view.InputChannel;
+import android.view.InputDevice;
 import android.view.InputEventReceiver;
 import android.view.KeyCharacterMap;
 import android.view.KeyEvent;
@@ -134,7 +135,10 @@ import android.widget.FrameLayout;
 import android.widget.ImageButton;
 import android.widget.LinearLayout;
 import android.widget.TextView;
+import android.window.OnBackInvokedCallback;
+import android.window.OnBackInvokedDispatcher;
 import android.window.WindowMetricsHelper;
+import android.window.WindowOnBackInvokedDispatcher;
 
 import com.android.internal.annotations.GuardedBy;
 import com.android.internal.inputmethod.IInputContentUriToken;
@@ -345,6 +349,9 @@ public class InputMethodService extends AbstractInputMethodService {
      **/
     private RingBuffer<MotionEvent> mPendingEvents;
 
+    /** Callback to handle back invocation when IME window is shown. */
+    private OnBackInvokedCallback mBackCallback;
+
     /**
      * Returns whether {@link InputMethodService} is responsible for rendering the back button and
      * the IME switcher button or not when the gestural navigation is enabled.
@@ -1605,6 +1612,7 @@ public class InputMethodService extends AbstractInputMethodService {
     @Override public void onDestroy() {
         mDestroyed = true;
         super.onDestroy();
+        unregisterOnBackInvokedCallback();
         mRootView.getViewTreeObserver().removeOnComputeInternalInsetsListener(
                 mInsetsComputer);
         doFinishInput();
@@ -2579,6 +2587,7 @@ public class InputMethodService extends AbstractInputMethodService {
         cancelImeSurfaceRemoval();
         mInShowWindow = false;
         Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
+        registerOnBackInvokedCallback();
     }
 
 
@@ -2624,6 +2633,56 @@ public class InputMethodService extends AbstractInputMethodService {
         if (doShowInput) startExtractingText(false);
     }
 
+    /**
+     * Registers an {@link OnBackInvokedCallback} to handle back invocation when ahead-of-time
+     *  back dispatching is enabled. We keep the KEYCODE_BACK based legacy code around to handle
+     *  back on older devices.
+     */
+    private void registerOnBackInvokedCallback() {
+        if (mBackCallback != null) {
+            // A back callback has already been registered.
+            return;
+        }
+        final ViewRootImpl viewRootImpl = mRootView == null ? null : mRootView.getViewRootImpl();
+        if (viewRootImpl != null && WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(
+                viewRootImpl.mContext)) {
+            final OnBackInvokedCallback callback = () -> {
+                KeyEvent downEvent = createKeyEvent(
+                        KeyEvent.ACTION_DOWN, false /* isTracking */);
+                onKeyDown(KeyEvent.KEYCODE_BACK, downEvent);
+                boolean hasStartedTracking =
+                        (downEvent.getFlags() & KeyEvent.FLAG_START_TRACKING) != 0;
+                KeyEvent upEvent = createKeyEvent(KeyEvent.ACTION_UP, hasStartedTracking);
+                onKeyUp(KeyEvent.KEYCODE_BACK, upEvent);
+            };
+            viewRootImpl.getOnBackInvokedDispatcher().registerOnBackInvokedCallback(
+                    OnBackInvokedDispatcher.PRIORITY_DEFAULT, callback);
+            mBackCallback = callback;
+        }
+    }
+
+    private KeyEvent createKeyEvent(int action, boolean isTracking) {
+        final long when = SystemClock.uptimeMillis();
+        return new KeyEvent(when, when, action,
+                KeyEvent.KEYCODE_BACK, 0 /* repeat */, 0 /* metaState */,
+                KeyCharacterMap.VIRTUAL_KEYBOARD, 0 /* scancode */,
+                KeyEvent.FLAG_FROM_SYSTEM | KeyEvent.FLAG_VIRTUAL_HARD_KEY
+                        | (isTracking ? KeyEvent.FLAG_TRACKING : 0),
+                InputDevice.SOURCE_KEYBOARD);
+    }
+
+    private void unregisterOnBackInvokedCallback() {
+        final ViewRootImpl viewRootImpl = mRootView == null ? null : mRootView.getViewRootImpl();
+        if (viewRootImpl != null
+                && mBackCallback != null
+                && WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(
+                viewRootImpl.mContext)) {
+            viewRootImpl.getOnBackInvokedDispatcher()
+                    .unregisterOnBackInvokedCallback(mBackCallback);
+        }
+        mBackCallback = null;
+    }
+
     /**
      * Applies the IME visibility in {@link android.view.ImeInsetsSourceConsumer}.
      *
@@ -2669,6 +2728,7 @@ public class InputMethodService extends AbstractInputMethodService {
         }
         mLastWasInFullscreenMode = mIsFullscreen;
         updateFullscreenMode();
+        unregisterOnBackInvokedCallback();
     }
 
     /**
-- 
cgit v1.2.3