Client-side reimplementation of IMM#setCurrentInputMethodSubtype()

This is a preparation to mark
InputMethodManager#setCurrentInputMethodSubtype() deprecated.

InputMethodManager#setCurrentInputMethodSubtype(), which was
introduced in Android 4.0 ICS [1], was probably mistakenly exposed as
a public API, because it has required WRITE_SECURE_SETTINGS that
typical applications cannot have.

Keeping maintaining InputMethodManager#setCurrentInputMethodSubtype()
is not that simple because now we are about to enable per-profile IME
mode, where this method needs to have a more clear spec about what
"Current" means.

An ideal solution is just removing this method, because if the caller
already has WRITE_SECURE_SETTINGS permission, they can just directly
update Settings.Secure.SELECTED_INPUT_METHOD_SUBTYPE to achieve the
same goal.  However, given that this has been a public API, it would
probably make sense to provide a fallback implementation like I did
for null IME token in InputMethodManager#setInputMethod() [2].

Either way, InputMethodManager#setCurrentInputMethodSubtype() will be
marked as deprecated in a subsequent CL.

 [1]: I55daa19ba924999def544bf841f00bf54852f3e1
      b66d287e30
 [2]: I42dd0325b01c527009bf85566ca8ba0766b2294e
      0c1ebffdb3

Bug: 123249820
Test: manually done with a test app that has WRITE_SECURE_SETTINGS
Change-Id: I76da83c57cffc6b73defccfd4a1b5734c958a97e

core/java/android/view/inputmethod/InputMethodManager.java

@@ -27,6 +27,7 @@ import android.annotation.SystemService;
 import android.annotation.TestApi;
 import android.annotation.UnsupportedAppUsage;
 import android.app.ActivityThread;
+import android.content.ComponentName;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.pm.PackageManager;
@@ -2492,11 +2493,48 @@ public final class InputMethodManager {
      */
     @RequiresPermission(WRITE_SECURE_SETTINGS)
     public boolean setCurrentInputMethodSubtype(InputMethodSubtype subtype) {
-        try {
-            return mService.setCurrentInputMethodSubtype(subtype);
-        } catch (RemoteException e) {
-            throw e.rethrowFromSystemServer();
+        if (Process.myUid() == Process.SYSTEM_UID) {
+            Log.w(TAG, "System process should not call setCurrentInputMethodSubtype() because "
+                    + "almost always it is a bug under multi-user / multi-profile environment. "
+                    + "Consider directly interacting with InputMethodManagerService "
+                    + "via LocalServices.");
+            return false;
         }
+        if (subtype == null) {
+            // See the JavaDoc. This is how this method has worked.
+            return false;
+        }
+        final Context fallbackContext = ActivityThread.currentApplication();
+        if (fallbackContext == null) {
+            return false;
+        }
+        if (fallbackContext.checkSelfPermission(WRITE_SECURE_SETTINGS)
+                != PackageManager.PERMISSION_GRANTED) {
+            return false;
+        }
+        final ContentResolver contentResolver = fallbackContext.getContentResolver();
+        final String imeId = Settings.Secure.getString(contentResolver,
+                Settings.Secure.DEFAULT_INPUT_METHOD);
+        if (ComponentName.unflattenFromString(imeId) == null) {
+            // Null or invalid IME ID format.
+            return false;
+        }
+        final List<InputMethodSubtype> enabledSubtypes;
+        try {
+            enabledSubtypes = mService.getEnabledInputMethodSubtypeList(imeId, true);
+        } catch (RemoteException e) {
+            return false;
+        }
+        final int numSubtypes = enabledSubtypes.size();
+        for (int i = 0; i < numSubtypes; ++i) {
+            final InputMethodSubtype enabledSubtype = enabledSubtypes.get(i);
+            if (enabledSubtype.equals(subtype)) {
+                Settings.Secure.putInt(contentResolver,
+                        Settings.Secure.SELECTED_INPUT_METHOD_SUBTYPE, enabledSubtype.hashCode());
+                return true;
+            }
+        }
+        return false;
     }
 
     /**

core/java/com/android/internal/view/IInputMethodManager.aidl

@@ -64,7 +64,6 @@ interface IInputMethodManager {
     void showInputMethodAndSubtypeEnablerFromClient(in IInputMethodClient client, String topId);
     boolean isInputMethodPickerShownForTest();
     InputMethodSubtype getCurrentInputMethodSubtype();
-    boolean setCurrentInputMethodSubtype(in InputMethodSubtype subtype);
     void setAdditionalInputMethodSubtypes(String id, in InputMethodSubtype[] subtypes);
     // This is kept due to @UnsupportedAppUsage.
     // TODO(Bug 113914148): Consider removing this.

services/core/java/com/android/server/inputmethod/InputMethodManagerService.java

@@ -4106,25 +4106,6 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
         return mCurrentSubtype;
     }
 
-    @Override
-    public boolean setCurrentInputMethodSubtype(InputMethodSubtype subtype) {
-        synchronized (mMethodMap) {
-            // TODO: Make this work even for non-current users?
-            if (!calledFromValidUserLocked()) {
-                return false;
-            }
-            if (subtype != null && mCurMethodId != null) {
-                InputMethodInfo imi = mMethodMap.get(mCurMethodId);
-                int subtypeId = InputMethodUtils.getSubtypeIdFromHashCode(imi, subtype.hashCode());
-                if (subtypeId != NOT_A_SUBTYPE_ID) {
-                    setInputMethodLocked(mCurMethodId, subtypeId);
-                    return true;
-                }
-            }
-            return false;
-        }
-    }
-
     private List<InputMethodInfo> getInputMethodListAsUser(@UserIdInt int userId) {
         synchronized (mMethodMap) {
             return getInputMethodListLocked(userId);

services/core/java/com/android/server/inputmethod/MultiClientInputMethodManagerService.java

@@ -1517,13 +1517,6 @@ public final class MultiClientInputMethodManagerService {
             return null;
         }
 
-        @BinderThread
-        @Override
-        public boolean setCurrentInputMethodSubtype(InputMethodSubtype subtype) {
-            reportNotSupported();
-            return false;
-        }
-
         @BinderThread
         @Override
         public void setAdditionalInputMethodSubtypes(String imiId, InputMethodSubtype[] subtypes) {