Merge "Implement locale matching in LocalesList."

4 files changed, 63 insertions, 6 deletions

diff --git a/api/current.txt b/api/current.txt
index 732a32257a56..19b509d62fb8 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -38701,9 +38701,9 @@ package android.util {
     method public int describeContents();
     method public static android.util.LocaleList forLanguageTags(java.lang.String);
     method public java.util.Locale get(int);
-    method public java.util.Locale getBestMatch(java.lang.String[]);
     method public static android.util.LocaleList getDefault();
     method public static android.util.LocaleList getEmptyLocaleList();
+    method public java.util.Locale getFirstMatch(java.lang.String[]);
     method public java.util.Locale getPrimary();
     method public boolean isEmpty();
     method public int size();
diff --git a/api/system-current.txt b/api/system-current.txt
index 40347cbfa1ac..dcfc7d11ae12 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -41034,9 +41034,9 @@ package android.util {
     method public int describeContents();
     method public static android.util.LocaleList forLanguageTags(java.lang.String);
     method public java.util.Locale get(int);
-    method public java.util.Locale getBestMatch(java.lang.String[]);
     method public static android.util.LocaleList getDefault();
     method public static android.util.LocaleList getEmptyLocaleList();
+    method public java.util.Locale getFirstMatch(java.lang.String[]);
     method public java.util.Locale getPrimary();
     method public boolean isEmpty();
     method public int size();
diff --git a/core/java/android/util/LocaleList.java b/core/java/android/util/LocaleList.java
index b2ee045db451..1becfb4a0e23 100644
--- a/core/java/android/util/LocaleList.java
+++ b/core/java/android/util/LocaleList.java
@@ -19,6 +19,7 @@ package android.util;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.Size;
+import android.icu.util.ULocale;
 import android.os.Parcel;
 import android.os.Parcelable;
 
@@ -208,10 +209,66 @@ public final class LocaleList implements Parcelable {
         }
     }
 
+    private static String getLikelyScript(Locale locale) {
+        final String script = locale.getScript();
+        if (!script.isEmpty()) {
+            return script;
+        } else {
+            // TODO: Cache the results if this proves to be too slow
+            return ULocale.addLikelySubtags(ULocale.forLocale(locale)).getScript();
+        }
+    }
+
+    private static int matchScore(Locale supported, Locale desired) {
+        if (supported.equals(desired)) {
+            return 1;  // return early so we don't do unnecessary computation
+        }
+        if (!supported.getLanguage().equals(desired.getLanguage())) {
+            return 0;
+        }
+        // There is no match if the two locales use different scripts. This will most imporantly
+        // take care of traditional vs simplified Chinese.
+        final String supportedScr = getLikelyScript(supported);
+        final String desiredScr = getLikelyScript(desired);
+        return supportedScr.equals(desiredScr) ? 1 : 0;
+    }
+
+    /**
+     * Returns the first match in the locale list given an unordered array of supported locales
+     * in BCP47 format.
+     *
+     * If the locale list is empty, null would be returned.
+     */
     @Nullable
-    public Locale getBestMatch(String[] locales) {
-        // TODO: Fix this to actually do locale negotiation and choose the best match
-        return getPrimary();
+    public Locale getFirstMatch(String[] supportedLocales) {
+        if (mList.length == 1) {  // just one locale, perhaps the most common scenario
+            return mList[0];
+        }
+        if (mList.length == 0) {  // empty locale list
+            return null;
+        }
+        // TODO: Figure out what to if en-XA or ar-XB are in the locale list
+        int bestIndex = Integer.MAX_VALUE;
+        for (String tag : supportedLocales) {
+            final Locale supportedLocale = Locale.forLanguageTag(tag);
+            // We expect the average length of locale lists used for locale resolution to be
+            // smaller than three, so it's OK to do this as an O(mn) algorithm.
+            for (int idx = 0; idx < mList.length; idx++) {
+                final int score = matchScore(supportedLocale, mList[idx]);
+                if (score > 0) {
+                    if (idx == 0) {  // We have a match on the first locale, which is good enough
+                        return mList[0];
+                    } else if (idx < bestIndex) {
+                        bestIndex = idx;
+                    }
+                }
+            }
+        }
+        if (bestIndex == Integer.MAX_VALUE) {  // no match was found
+            return mList[0];
+        } else {
+            return mList[bestIndex];
+        }
     }
 
     private final static Object sLock = new Object();
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 507233f4920d..e4a6f3c7c96d 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -17901,7 +17901,7 @@ public final class ActivityManagerService extends ActivityManagerNative
                     if (mSupportedSystemLocales == null) {
                         mSupportedSystemLocales = Resources.getSystem().getAssets().getLocales();
                     }
-                    final Locale locale = values.getLocales().getBestMatch(mSupportedSystemLocales);
+                    final Locale locale = values.getLocales().getFirstMatch(mSupportedSystemLocales);
                     SystemProperties.set("persist.sys.locale", locale.toLanguageTag());
                     mHandler.sendMessage(mHandler.obtainMessage(SEND_LOCALE_TO_MOUNT_DAEMON_MSG,
                             locale));