Android: Add DW_FEATURE_RENDER_SAFE, initially just for Android. This will eventually be supported on other platforms that support unsafe rendering. On Android this moves EXPOSE events off the main thread and is enabled by default to provide extra safety. Since none of the callbacks happen on the main thread anymore, this means that none of the threading functions follow the potentially unsafe code paths that lead to instability. The trade off is performance, rendering performance, which was already kind of slow is even worse. I'll look for ways to improve this performance without sacrificing stability.