This includes changes to callbacks used by custom backends. It adds a
`pConfig` parameter to both onContextInit and onDeviceInit. This allows
custom backends to specify custom config properties.
This commit includes a few changes required for better supporting this:
* Extra members have been added to ma_device_info which are going to
eventually replace the min and max channels and sample rates. The
new system is going to provide a list of supported data formats,
groups by format/channels/rate and some flags. The only flag used
at the moment is whether or not the format is usable in exclusive
mode. The custom backend is the only backend currently using these
new device info properties, and a backwards-compatibility layer has
been implemented to fill out the old properties. Built-in backends
will be migrated over to the new system in time.
* A new set of backend callbacks have been implemented. Only the
custom backend is using these at the moment. Built-in backends will
be migrated over to these new backends soon.
* A new public API called ma_device_get_state() has been added which
returns the current state of the device (whether or not it's
started or stopped). This is necessary for some custom backends.
* A new public API called ma_device_handle_backend_data_callback()
has been added. This is required for custom backends who use the
callback paradigm for data delivery.
* A new type of ring buffer has been created called ma_duplex_rb.
This is used as an intermediary buffer for duplex devices running
on backends that use the callback paradigm. It's used internally by
ma_device_handle_backend_data_callback(). In the future it's
planned to expand ma_duplex_rb to handle desyncs by dynamically
resampling to get both sides back in sync. This is not implemented
as of this commit.
Future work will involve converting existing built-in backends to be
consistent with the new ideas introduced with custom backend support.
David Reid