FEAT(client): Implement native support for PipeWire

Tested with PipeWire 0.3.26.

The implementation is quite basic and simple, yet it surpasses the JACK one in terms of features.
For example, support for the most common surround mappings is provided.

As opposed to JACK, an option to disable the auto endpoint connection is not provided.
However, it's something that can be easily implemented if needed.

Support for echo cancellation will definitely be added in future.

3rdparty/pipewire/pipewire/context.h

@@ -0,0 +1,194 @@
+/* PipeWire
+ *
+ * Copyright © 2018 Wim Taymans
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef PIPEWIRE_CONTEXT_H
+#define PIPEWIRE_CONTEXT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <spa/utils/defs.h>
+#include <spa/utils/hook.h>
+
+/** \class pw_context
+ *
+ * \brief the PipeWire context
+ *
+ * The context object manages all locally available resources. It
+ * is used by both clients and servers.
+ *
+ * The context is used to:
+ *
+ *  - Load modules and extend the functionality. This includes
+ *    extending the protocol with new object types or creating
+ *    any of the available objects.
+ *
+ *  - Create implementations of various objects like nodes,
+ *    devices, factories, modules, etc.. This will usually also
+ *    create pw_global objects that can then be shared with
+ *    clients.
+ *
+ *  - Connect to another PipeWire instance (the main daemon, for
+ *    example) and interact with it (See \subpage page_core_api).
+ *
+ *  - Export a local implementation of an object to another
+ *    instance.
+ */
+struct pw_context;
+
+struct pw_global;
+struct pw_impl_client;
+
+#include <pipewire/core.h>
+#include <pipewire/loop.h>
+#include <pipewire/properties.h>
+
+/** \page page_context_api Core API
+ *
+ * \section page_context_overview Overview
+ *
+ * \subpage page_context
+ *
+ * \subpage page_global
+ *
+ * \subpage page_client
+ *
+ * \subpage page_resource
+ *
+ * \subpage page_node
+ *
+ * \subpage page_port
+ *
+ * \subpage page_link
+ */
+
+/** \page page_context Context
+ *
+ * \section page_context_overview Overview
+ *
+ * The context object is an object that manages the state and
+ * resources of a PipeWire instance.
+ */
+
+/** context events emitted by the context object added with \ref pw_context_add_listener */
+struct pw_context_events {
+#define PW_VERSION_CONTEXT_EVENTS	0
+	uint32_t version;
+
+	/** The context is being destroyed */
+	void (*destroy) (void *data);
+	/** The context is being freed */
+	void (*free) (void *data);
+	/** a new client object is added */
+	void (*check_access) (void *data, struct pw_impl_client *client);
+	/** a new global object was added */
+	void (*global_added) (void *data, struct pw_global *global);
+	/** a global object was removed */
+	void (*global_removed) (void *data, struct pw_global *global);
+};
+
+/** Make a new context object for a given main_loop. Ownership of the properties is taken */
+struct pw_context * pw_context_new(struct pw_loop *main_loop,		/**< a main loop to run in */
+			     struct pw_properties *props,	/**< extra properties */
+			     size_t user_data_size		/**< extra user data size */);
+
+/** destroy a context object, all resources except the main_loop will be destroyed */
+void pw_context_destroy(struct pw_context *context);
+
+/** Get the context user data */
+void *pw_context_get_user_data(struct pw_context *context);
+
+/** Add a new event listener to a context */
+void pw_context_add_listener(struct pw_context *context,
+			  struct spa_hook *listener,
+			  const struct pw_context_events *events,
+			  void *data);
+
+/** Get the context properties */
+const struct pw_properties *pw_context_get_properties(struct pw_context *context);
+
+/** Update the context properties */
+int pw_context_update_properties(struct pw_context *context, const struct spa_dict *dict);
+
+/** Get a config section for this context. Since 0.3.22 */
+const char *pw_context_get_conf_section(struct pw_context *context, const char *section);
+
+/** Get the context support objects */
+const struct spa_support *pw_context_get_support(struct pw_context *context, uint32_t *n_support);
+
+/** get the context main loop */
+struct pw_loop *pw_context_get_main_loop(struct pw_context *context);
+
+/** Get the work queue from the context: Since 0.3.26 */
+struct pw_work_queue *pw_context_get_work_queue(struct pw_context *context);
+
+/** Iterate the globals of the context. The callback should return
+ * 0 to fetch the next item, any other value stops the iteration and returns
+ * the value. When all callbacks return 0, this function returns 0 when all
+ * globals are iterated. */
+int pw_context_for_each_global(struct pw_context *context,	/**< the context */
+			    int (*callback) (void *data, struct pw_global *global),
+			    void *data);
+
+/** Find a context global by id */
+struct pw_global *pw_context_find_global(struct pw_context *context,	/**< the context */
+				      uint32_t id		/**< the global id */);
+
+/** add a spa library for the given factory_name regex */
+int pw_context_add_spa_lib(struct pw_context *context, const char *factory_regex, const char *lib);
+
+/** find the library name for a spa factory */
+const char * pw_context_find_spa_lib(struct pw_context *context, const char *factory_name);
+
+struct spa_handle *pw_context_load_spa_handle(struct pw_context *context,
+		const char *factory_name,
+		const struct spa_dict *info);
+
+
+/** data for registering export functions */
+struct pw_export_type {
+	struct spa_list link;
+	const char *type;
+	struct pw_proxy * (*func) (struct pw_core *core,
+		const char *type, const struct spa_dict *props, void *object,
+		size_t user_data_size);
+};
+
+/** register a type that can be exported on a context_proxy. This is usually used by
+ * extension modules */
+int pw_context_register_export_type(struct pw_context *context, struct pw_export_type *type);
+/** find information about registered export type */
+const struct pw_export_type *pw_context_find_export_type(struct pw_context *context, const char *type);
+
+/** add an object to the context */
+int pw_context_set_object(struct pw_context *context, const char *type, void *value);
+/** get an object from the context */
+void *pw_context_get_object(struct pw_context *context, const char *type);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PIPEWIRE_CONTEXT_H */