Enable background users to call IMM#getCurrentInputMethodSubtype()

This is a follow up CL to my previous CLs [1][2], which let query APIs
defined in InputMethodManager support background users.

With this CL,

  InputMethodManager#getCurrentInputMethodSubtype()

is also fully supported under multi-user / multi-profile environment.

 [1]: I192a0f5a1375170d17a4c08af94f23966dbaea8b
      7f8ee4b9dd
 [2]: I48f57dc7184e85bdb422fd9d1d56e60381654125
      e960986554

Bug: 34886274
Bug: 122164939
Bug: 237316307
Test: atest CtsInputMethodTestCases:InputMethodSubtypeTest
Change-Id: Icb09f9cb1a4147884faa9952b2e03ec4afa9f0b1

core/java/android/view/inputmethod/IInputMethodManagerInvoker.java

@@ -182,9 +182,9 @@ final class IInputMethodManagerInvoker {
 
     @AnyThread
     @Nullable
-    InputMethodSubtype getCurrentInputMethodSubtype() {
+    InputMethodSubtype getCurrentInputMethodSubtype(@UserIdInt int userId) {
         try {
-            return mTarget.getCurrentInputMethodSubtype();
+            return mTarget.getCurrentInputMethodSubtype(userId);
         } catch (RemoteException e) {
             throw e.rethrowFromSystemServer();
         }

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

@@ -3374,7 +3374,7 @@ public final class InputMethodManager {
      */
     @Nullable
     public InputMethodSubtype getCurrentInputMethodSubtype() {
-        return mServiceInvoker.getCurrentInputMethodSubtype();
+        return mServiceInvoker.getCurrentInputMethodSubtype(UserHandle.myUserId());
     }
 
     /**

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

@@ -88,7 +88,10 @@ interface IInputMethodManager {
             + "android.Manifest.permission.TEST_INPUT_METHOD)")
     boolean isInputMethodPickerShownForTest();
 
-    @nullable InputMethodSubtype getCurrentInputMethodSubtype();
+    @JavaPassthrough(annotation="@android.annotation.RequiresPermission(value = "
+            + "android.Manifest.permission.INTERACT_ACROSS_USERS_FULL, conditional = true)")
+    @nullable InputMethodSubtype getCurrentInputMethodSubtype(int userId);
+
     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

@@ -5284,18 +5284,38 @@ public final class InputMethodManagerService extends IInputMethodManager.Stub
 
     /**
      * Gets the current subtype of this input method.
+     *
+     * @param userId User ID to be queried about.
+     * @return The current {@link InputMethodSubtype} for the specified user.
      */
+    @Nullable
     @Override
-    public InputMethodSubtype getCurrentInputMethodSubtype() {
+    public InputMethodSubtype getCurrentInputMethodSubtype(@UserIdInt int userId) {
+        if (UserHandle.getCallingUserId() != userId) {
+            mContext.enforceCallingPermission(Manifest.permission.INTERACT_ACROSS_USERS_FULL, null);
+        }
         synchronized (ImfLock.class) {
-            // TODO: Make this work even for non-current users?
-            if (!calledFromValidUserLocked()) {
-                return null;
+            if (mSettings.getCurrentUserId() == userId) {
+                return getCurrentInputMethodSubtypeLocked();
             }
-            return getCurrentInputMethodSubtypeLocked();
+
+            final ArrayMap<String, InputMethodInfo> methodMap = queryMethodMapForUser(userId);
+            final InputMethodSettings settings = new InputMethodSettings(mContext, methodMap,
+                    userId, false);
+            return settings.getCurrentInputMethodSubtypeForNonCurrentUsers();
         }
     }
 
+    /**
+     * Returns the current {@link InputMethodSubtype} for the current user.
+     *
+     * <p>CAVEATS: You must also update
+     * {@link InputMethodSettings#getCurrentInputMethodSubtypeForNonCurrentUsers()}
+     * when you update the algorithm of this method.</p>
+     *
+     * <p>TODO: Address code duplication between this and
+     * {@link InputMethodSettings#getCurrentInputMethodSubtypeForNonCurrentUsers()}.</p>
+     */
     @GuardedBy("ImfLock.class")
     InputMethodSubtype getCurrentInputMethodSubtypeLocked() {
         String selectedMethodId = getSelectedMethodIdLocked();

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

@@ -818,6 +818,56 @@ final class InputMethodUtils {
             }
         }
 
+        /**
+         * A variant of {@link InputMethodManagerService#getCurrentInputMethodSubtypeLocked()} for
+         * non-current users.
+         *
+         * <p>TODO: Address code duplication between this and
+         * {@link InputMethodManagerService#getCurrentInputMethodSubtypeLocked()}.</p>
+         *
+         * @return {@link InputMethodSubtype} if exists. {@code null} otherwise.
+         */
+        @Nullable
+        InputMethodSubtype getCurrentInputMethodSubtypeForNonCurrentUsers() {
+            final String selectedMethodId = getSelectedInputMethod();
+            if (selectedMethodId == null) {
+                return null;
+            }
+            final InputMethodInfo imi = mMethodMap.get(selectedMethodId);
+            if (imi == null || imi.getSubtypeCount() == 0) {
+                return null;
+            }
+
+            final int subtypeHashCode = getSelectedInputMethodSubtypeHashCode();
+            if (subtypeHashCode != InputMethodUtils.NOT_A_SUBTYPE_ID) {
+                final int subtypeIndex = SubtypeUtils.getSubtypeIdFromHashCode(imi,
+                        subtypeHashCode);
+                if (subtypeIndex >= 0) {
+                    return imi.getSubtypeAt(subtypeIndex);
+                }
+            }
+
+            // If there are no selected subtypes, the framework will try to find the most applicable
+            // subtype from explicitly or implicitly enabled subtypes.
+            final List<InputMethodSubtype> explicitlyOrImplicitlyEnabledSubtypes =
+                    getEnabledInputMethodSubtypeListLocked(imi, true);
+            // If there is only one explicitly or implicitly enabled subtype, just returns it.
+            if (explicitlyOrImplicitlyEnabledSubtypes.isEmpty()) {
+                return null;
+            }
+            if (explicitlyOrImplicitlyEnabledSubtypes.size() == 1) {
+                return explicitlyOrImplicitlyEnabledSubtypes.get(0);
+            }
+            final InputMethodSubtype subtype = SubtypeUtils.findLastResortApplicableSubtypeLocked(
+                    mRes, explicitlyOrImplicitlyEnabledSubtypes, SubtypeUtils.SUBTYPE_MODE_KEYBOARD,
+                    null, true);
+            if (subtype != null) {
+                return subtype;
+            }
+            return SubtypeUtils.findLastResortApplicableSubtypeLocked(mRes,
+                    explicitlyOrImplicitlyEnabledSubtypes, null, null, true);
+        }
+
         public void dumpLocked(final Printer pw, final String prefix) {
             pw.println(prefix + "mCurrentUserId=" + mCurrentUserId);
             pw.println(prefix + "mCurrentProfileIds=" + Arrays.toString(mCurrentProfileIds));