The documentation says this blocks. This should block because it also
means the error reporting is more accurate by calling set_last_error
just before returning.
Otherwise it is possible for the context that is used in the spawn to
be unreferenced. Really this should be caught by the borrow checker
that ensures we only spawn things with a 'static lifetime, but we're
handling raw pointers so it doesn't.
This replaces the mechanism by which the IoPauseGuard makes sure the
IO scheduler is resumed: it really is a drop guard now by sending a
single message on drop.
This makes it not have to hold on to anything like the context so
makes it a lot easier to use.
The trade-off is that a long-running task is spawned when the guard is
created, this task needs to receive the message from the drop guard in
order for the scheduler to resume.
This changes the JSON-RPC APIs to get a QR code from the backup
provider to block. It means once you have a (blocking) call to
provide_backup() you can call get_backup_qr() or get_backup_qr_svg()
and they will block until the QR code is available.
Calling get_backup_qr() or get_backup_qr_svg() when there is no backup
provider will immediately error.
This adds a result extension trait to explicitly set the last error,
which *should* be the default for the FFI. Currently not touching all
APIs since that's potentially disruptive and we're close to a release.
The logging story is messy, as described in the doc comment. We
should further clean this up and tidy up these APIs so it's more
obvious to people how to do the right thing.
This makes the BackupProvider automatically invoke pause-io while it
is needed.
It needed to make the guard independent from the Context lifetime to
make this work. Which is a bit sad.
To handle backups the UIs have to make sure they do stop the IO
scheduler and also don't accidentally restart it while working on it.
Since they have to call start_io from a bunch of locations this can be
a bit difficult to manage.
This introduces a mechanism for the core to pause IO for some time,
which is used by the imex function. It interacts well with other
calls to dc_start_io() and dc_stop_io() making sure that when resumed
the scheduler will be running or not as the latest calls to them.
This was a little more invasive then hoped due to the scheduler. The
additional abstraction of the scheduler on the context seems a nice
improvement though.
