XML and by inheritence XMPP has the feature of transmitting multiple language
variants for the same content. This can be really useful if, for example, you
are talking to an automated system. A chat bot could greet you in your own
language.
On the wire this will usually look like this:
```xml
<message to="you">
<body>Good morning</body>
<body xml:lang="de">Guten Morgen</body>
</message>
```
However receiving such a message in a group chat can be very confusing and
potentially dangerous if the sender puts conflicting information in there and
different people get shown different strings.
Disabeling support for localization entirely isn’t an ideal solution as on
principle it is still a good feature; and other clients might still show a
localization even if Conversations would always show the default language.
So instead Conversations now shows the displayed language in a corner of the
message bubble if more than one translation has been received.
If multiple languages are received Conversations will attempt to find one in
the language the operating system is set to. If no such translation can be
found it will attempt to display the English string.
If English can not be found either (for example a message that only has ru and
fr on a phone that is set to de) it will display what ever language came first.
Furthermore Conversations will discard (not show at all) messages with with
multiple bodies of the same language. (This is considered an invalid message)
The lanuage tag will not be shown if Conversations received a single body in
a language not understood by the user. (For example operating system set to
'de' and message received with one body in 'ru' will just display that body as
usual.)
As a guide line to the user: If you are reading a message where it is important
that this message is not interpreted differently by different people (like a
vote (+1 / -1) in a chat room) make sure it has *no* language tag.
We have seen some weird CursorIndexNotFoundException that we were unable to reproduce.
We assume that going forward (moveToNext()) through the cursor instead of (moveToPrevious() fixes that issue
after receiving a SignalMessage that can’t be decrypted because of broken sessions
Conversations will attempt to grab a new pre key bundle and send a new PreKeySignalMessage
wrapped in a key transport message.
Conversations stores sensitive data, such as SQLiteAxolotlStore tables, in its database.
secure_delete=ON is the default for newer Android devices:
https://android-review.googlesource.com/c/platform/external/sqlite/+/209123
However, older devices had it disabled by default, so any database created than has this setting disabled and it will not be updated automatically.
Also, the default might be changed in the future (for example, to "FAST", added in 2017), so it is safer to set it explicitly.
This way we avoid repeating the code. Unlike getWritableDatabase, onConfigure is intended to be overridden.
In fact, onConfigure documentation specifically says: "Called when the database connection is being configured, to enable features such as write-ahead logging or *foreign key support*."
