Support IME switcher icon visibility update

With this CL, the IME switcher icon becomes visible only when
necessary, even if InputMethodService renders the back button and the
IME switcher button in the gestural navigation mode.

Implementation idea:

InputMethodManagerService#shouldShowImeSwitcherLocked() is the source
of truth about whether the IME switcher visibility should be shown or
not, and it internally depends on the following conditions:

 A. com.android.internal.R.bool.show_ongoing_ime_switcher
 B. Whether the IME switcher is already shown or not.
 C. Whether the IME is perceptible or not.
 D. Whether one or more hardware keyboards are attached or not.
 E. Keyguard state.
 F. What IMEs and their subtypes are enabled.

Here are what those conditions would mean for this project.

 * A is considered to be a per-device constant value.
 * B, D, and F can happen at any time outside of the IME lifecycle
   events such as startInput().
 * C is no longer relevant if those buttons are rendered by the IME.
 * E is considered to be constant throughout each startInput() cycle.

This CL uses the following 3 IPCs to notify when the IME switcher
visibility is changing.

 1. IInputMethod#initializeInternal()
 2. IInputMethod#startInput()
 3. IInputMethod#onShouldShowImeSwitcherWhenImeIsShownChanged()

1 and 2 will be used to provide the "initial" value to avoid potential
flickers.  3 is still necessary to take care of async changes
triggered by B, D, and F.

Fix: 215551357
Test: Manually verified with for the following scenarios:
 * Enabling/disabling multiple IMEs
 * Attaching/detaching a hardware keyboard
 * Showing/hinding the IME switcher
 * Showing an IME on the lock screen
Change-Id: I5de9ac0dc8670842edf66306bb4c281c77cea376

1 files changed, 28 insertions, 8 deletions

diff --git a/core/java/android/inputmethodservice/IInputMethodWrapper.java b/core/java/android/inputmethodservice/IInputMethodWrapper.java
index 41642e7a9fce..af57f793bf73 100644
--- a/core/java/android/inputmethodservice/IInputMethodWrapper.java
+++ b/core/java/android/inputmethodservice/IInputMethodWrapper.java
@@ -70,6 +70,7 @@ class IInputMethodWrapper extends IInputMethod.Stub
     private static final int DO_SET_INPUT_CONTEXT = 20;
     private static final int DO_UNSET_INPUT_CONTEXT = 30;
     private static final int DO_START_INPUT = 32;
+    private static final int DO_ON_SHOULD_SHOW_IME_SWITCHER_WHEN_IME_IS_SHOWN_CHANGED = 35;
     private static final int DO_CREATE_SESSION = 40;
     private static final int DO_SET_SESSION_ENABLED = 45;
     private static final int DO_SHOW_SOFT_INPUT = 60;
@@ -175,7 +176,7 @@ class IInputMethodWrapper extends IInputMethod.Stub
                 try {
                     inputMethod.initializeInternal((IBinder) args.arg1,
                             (IInputMethodPrivilegedOperations) args.arg2, msg.arg1,
-                            (boolean) args.arg3);
+                            (boolean) args.arg3, msg.arg2 != 0);
                 } finally {
                     args.recycle();
                 }
@@ -195,14 +196,22 @@ class IInputMethodWrapper extends IInputMethod.Stub
                 final EditorInfo info = (EditorInfo) args.arg3;
                 final CancellationGroup cancellationGroup = (CancellationGroup) args.arg4;
                 final boolean restarting = args.argi5 == 1;
+                final boolean shouldShowImeSwitcherWhenImeIsShown = args.argi6 != 0;
                 final InputConnection ic = inputContext != null
                         ? new RemoteInputConnection(mTarget, inputContext, cancellationGroup)
                         : null;
                 info.makeCompatible(mTargetSdkVersion);
-                inputMethod.dispatchStartInputWithToken(ic, info, restarting, startInputToken);
+                inputMethod.dispatchStartInputWithToken(ic, info, restarting, startInputToken,
+                        shouldShowImeSwitcherWhenImeIsShown);
                 args.recycle();
                 return;
             }
+            case DO_ON_SHOULD_SHOW_IME_SWITCHER_WHEN_IME_IS_SHOWN_CHANGED: {
+                final boolean shouldShowImeSwitcherWhenImeIsShown = msg.arg1 != 0;
+                inputMethod.onShouldShowImeSwitcherWhenImeIsShownChanged(
+                        shouldShowImeSwitcherWhenImeIsShown);
+                return;
+            }
             case DO_CREATE_SESSION: {
                 SomeArgs args = (SomeArgs)msg.obj;
                 inputMethod.createSession(new InputMethodSessionCallbackWrapper(
@@ -291,10 +300,11 @@ class IInputMethodWrapper extends IInputMethod.Stub
     @BinderThread
     @Override
     public void initializeInternal(IBinder token, IInputMethodPrivilegedOperations privOps,
-            int configChanges, boolean stylusHwSupported) {
-        mCaller.executeOrSendMessage(
-                mCaller.obtainMessageIOOO(
-                        DO_INITIALIZE_INTERNAL, configChanges, token, privOps, stylusHwSupported));
+            int configChanges, boolean stylusHwSupported,
+            boolean shouldShowImeSwitcherWhenImeIsShown) {
+        mCaller.executeOrSendMessage(mCaller.obtainMessageIIOOO(DO_INITIALIZE_INTERNAL,
+                configChanges, shouldShowImeSwitcherWhenImeIsShown ? 1 : 0, token, privOps,
+                stylusHwSupported));
     }
 
     @BinderThread
@@ -334,13 +344,23 @@ class IInputMethodWrapper extends IInputMethod.Stub
     @BinderThread
     @Override
     public void startInput(IBinder startInputToken, IInputContext inputContext,
-            EditorInfo attribute, boolean restarting) {
+            EditorInfo attribute, boolean restarting, boolean shouldShowImeSwitcherWhenImeIsShown) {
         if (mCancellationGroup == null) {
             Log.e(TAG, "startInput must be called after bindInput.");
             mCancellationGroup = new CancellationGroup();
         }
         mCaller.executeOrSendMessage(mCaller.obtainMessageOOOOII(DO_START_INPUT, startInputToken,
-                inputContext, attribute, mCancellationGroup, restarting ? 1 : 0, 0 /* unused */));
+                inputContext, attribute, mCancellationGroup, restarting ? 1 : 0,
+                shouldShowImeSwitcherWhenImeIsShown ? 1 : 0));
+    }
+
+    @BinderThread
+    @Override
+    public void onShouldShowImeSwitcherWhenImeIsShownChanged(
+            boolean shouldShowImeSwitcherWhenImeIsShown) {
+        mCaller.executeOrSendMessage(mCaller.obtainMessageI(
+                DO_ON_SHOULD_SHOW_IME_SWITCHER_WHEN_IME_IS_SHOWN_CHANGED,
+                shouldShowImeSwitcherWhenImeIsShown ? 1 : 0));
     }
 
     @BinderThread