audio_core: Make g_sink_details internally linked

We can hide the direct array from external view and instead provide
functions to retrieve the necessary info. This has the benefit of
completely hiding the makeup of the SinkDetails structure from the rest
of the code.

Given that this makes the array hidden, we can also make the array
constexpr by altering the members slightly. This gets rid of several
static constructor calls related to std::vector and std::function.

Now we don't have heap allocations here that need to occur before the
program can even enter main(). It also has the benefit of saving a
little bit of heap space, but this doesn't matter too much, since the
savings in that regard are pretty tiny.

src/audio_core/sink_details.h

@@ -4,34 +4,21 @@
 
 #pragma once
 
-#include <functional>
-#include <memory>
 #include <string>
 #include <string_view>
-#include <utility>
 #include <vector>
 
 namespace AudioCore {
 
 class Sink;
 
-struct SinkDetails {
-    using FactoryFn = std::function<std::unique_ptr<Sink>(std::string)>;
-    using ListDevicesFn = std::function<std::vector<std::string>()>;
+/// Retrieves the IDs for all available audio sinks.
+std::vector<const char*> GetSinkIDs();
 
-    SinkDetails(const char* id_, FactoryFn factory_, ListDevicesFn list_devices_)
-        : id(id_), factory(std::move(factory_)), list_devices(std::move(list_devices_)) {}
+/// Gets the list of devices for a particular sink identified by the given ID.
+std::vector<std::string> GetDeviceListForSink(std::string_view sink_id);
 
-    /// Name for this sink.
-    const char* id;
-    /// A method to call to construct an instance of this type of sink.
-    FactoryFn factory;
-    /// A method to call to list available devices.
-    ListDevicesFn list_devices;
-};
-
-extern const std::vector<SinkDetails> g_sink_details;
-
-const SinkDetails& GetSinkDetails(std::string_view sink_id);
+/// Creates an audio sink identified by the given device ID.
+std::unique_ptr<Sink> CreateSinkFromID(std::string_view sink_id, std::string_view device_id);
 
 } // namespace AudioCore