Don't broadcast an event unless settings have changed.

briar-android/src/org/briarproject/android/invitation/AddContactActivity.java

@@ -8,7 +8,6 @@ import org.briarproject.R;
 import org.briarproject.android.BriarActivity;
 import org.briarproject.api.android.ReferenceManager;
 import org.briarproject.api.crypto.CryptoComponent;
-import org.briarproject.api.db.DatabaseComponent;
 import org.briarproject.api.db.DbException;
 import org.briarproject.api.identity.AuthorId;
 import org.briarproject.api.identity.IdentityManager;
@@ -54,7 +53,6 @@ implements InvitationListener {
 	private String contactName = null;
 
 	// Fields that are accessed from background threads must be volatile
-	@Inject private volatile DatabaseComponent db;
 	@Inject private volatile IdentityManager identityManager;
 
 	@Override

briar-core/src/org/briarproject/db/DatabaseComponentImpl.java

@@ -930,11 +930,19 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	public void mergeSettings(Settings s, String namespace) throws DbException {
+		boolean changed = false;
 		lock.writeLock().lock();
 		try {
 			T txn = db.startTransaction();
 			try {
-				db.mergeSettings(txn, s, namespace);
+				Settings old = db.getSettings(txn, namespace);
+				Settings merged = new Settings();
+				merged.putAll(old);
+				merged.putAll(s);
+				if (!merged.equals(old)) {
+					db.mergeSettings(txn, s, namespace);
+					changed = true;
+				}
 				db.commitTransaction(txn);
 			} catch (DbException e) {
 				db.abortTransaction(txn);
@@ -943,7 +951,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		} finally {
 			lock.writeLock().unlock();
 		}
-		eventBus.broadcast(new SettingsUpdatedEvent(namespace));
+		if (changed) eventBus.broadcast(new SettingsUpdatedEvent(namespace));
 	}
 
 	public void receiveAck(ContactId c, Ack a) throws DbException {

briar-tests/src/org/briarproject/db/DatabaseComponentImplTest.java

@@ -24,12 +24,14 @@ import org.briarproject.api.event.MessageToRequestEvent;
 import org.briarproject.api.event.MessageValidatedEvent;
 import org.briarproject.api.event.MessagesAckedEvent;
 import org.briarproject.api.event.MessagesSentEvent;
+import org.briarproject.api.event.SettingsUpdatedEvent;
 import org.briarproject.api.event.SubscriptionAddedEvent;
 import org.briarproject.api.event.SubscriptionRemovedEvent;
 import org.briarproject.api.identity.Author;
 import org.briarproject.api.identity.AuthorId;
 import org.briarproject.api.identity.LocalAuthor;
 import org.briarproject.api.lifecycle.ShutdownManager;
+import org.briarproject.api.settings.Settings;
 import org.briarproject.api.sync.Ack;
 import org.briarproject.api.sync.ClientId;
 import org.briarproject.api.sync.Group;
@@ -1319,4 +1321,47 @@ public class DatabaseComponentImplTest extends BriarTestCase {
 				2, 456);
 		return new TransportKeys(transportId, inPrev, inCurr, inNext, outCurr);
 	}
+
+	@Test
+	public void testMergeSettings() throws Exception {
+		final Settings before = new Settings();
+		before.put("foo", "bar");
+		before.put("baz", "bam");
+		final Settings update = new Settings();
+		update.put("baz", "qux");
+		final Settings merged = new Settings();
+		merged.put("foo", "bar");
+		merged.put("baz", "qux");
+		Mockery context = new Mockery();
+		@SuppressWarnings("unchecked")
+		final Database<Object> database = context.mock(Database.class);
+		final ShutdownManager shutdown = context.mock(ShutdownManager.class);
+		final EventBus eventBus = context.mock(EventBus.class);
+		context.checking(new Expectations() {{
+			// mergeSettings()
+			oneOf(database).startTransaction();
+			will(returnValue(txn));
+			oneOf(database).getSettings(txn, "namespace");
+			will(returnValue(before));
+			oneOf(database).mergeSettings(txn, update, "namespace");
+			oneOf(database).commitTransaction(txn);
+			oneOf(eventBus).broadcast(with(any(SettingsUpdatedEvent.class)));
+			// mergeSettings() again
+			oneOf(database).startTransaction();
+			will(returnValue(txn));
+			oneOf(database).getSettings(txn, "namespace");
+			will(returnValue(merged));
+			oneOf(database).commitTransaction(txn);
+		}});
+
+		DatabaseComponent db = createDatabaseComponent(database, eventBus,
+				shutdown);
+
+		// First merge should broadcast an event
+		db.mergeSettings(update, "namespace");
+		// Second merge should not broadcast an event
+		db.mergeSettings(update, "namespace");
+
+		context.assertIsSatisfied();
+	}
 }