Add support for server-side language bindings

This commit adds support for server-side languages bindings.  This is done
in two ways:

1. Adding a wl_resource_set_dispatcher function that corresponds to
wl_resource_set_interface.  The only difference between the two functions
is that the new version takes a dispatcher along with the implementation,
data, and destructor.  This allows for runtime calling of native language
functions for callbacks instead of having to generate function pointers.

2. Adding versions of wl_resource_post_event and wl_resource_queue_event
that take an array of wl_argument instead of a variable argument list.
This allows for easier run-time argument conversion and removes the need
for libffi-based calling of variadic functions.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>

src/wayland-util.h

@@ -199,6 +199,46 @@ static inline wl_fixed_t wl_fixed_from_int(int i)
 	return i * 256;
 }
 
+/**
+ * \brief A union representing all of the basic data types that can be passed
+ * along the wayland wire format.
+ *
+ * This union represents all of the basic data types that can be passed in the
+ * wayland wire format.  It is used by dispatchers and runtime-friendly
+ * versions of the event and request marshaling functions.
+ */
+union wl_argument {
+	int32_t i; /**< signed integer */
+	uint32_t u; /**< unsigned integer */
+	wl_fixed_t f; /**< fixed point */
+	const char *s; /**< string */
+	struct wl_object *o; /**< object */
+	uint32_t n; /**< new_id */
+	struct wl_array *a; /**< array */
+	int32_t h; /**< file descriptor */
+};
+
+/**
+ * \brief A function pointer type for a dispatcher.
+ *
+ * A dispatcher is a function that handles the emitting of callbacks in client
+ * code.  For programs directly using the C library, this is done by using
+ * libffi to call function pointers.  When binding to languages other than C,
+ * dispatchers provide a way to abstract the function calling process to be
+ * friendlier to other function calling systems.
+ *
+ * A dispatcher takes five arguments:  The first is the dispatcher-specific
+ * implementation data associated with the target object.  The second is the
+ * object on which the callback is being invoked (either wl_proxy or
+ * wl_resource).  The third and fourth arguments are the opcode the wl_messsage
+ * structure corresponding to the callback being emitted.  The final argument
+ * is an array of arguments recieved from the other process via the wire
+ * protocol.
+ */
+typedef int (*wl_dispatcher_func_t)(const void *, void *, uint32_t,
+				    const struct wl_message *,
+				    union wl_argument *);
+
 typedef void (*wl_log_func_t)(const char *, va_list);
 
 #ifdef  __cplusplus