Wayland: logging

The core libwayland libraries should not handle logging, only passing
the error messages to subscribed functions.
An application linked to libwayland-server or libwayland-client
will be able to set own functions (one per library) to handle error
messages.

Change in this series: make the wl_log return int, because
of compatibility with printf. It will return the number of bytes logged.

src/wayland-client.c

@@ -589,3 +589,9 @@ wl_proxy_get_id(struct wl_proxy *proxy)
 {
 	return proxy->object.id;
 }
+
+WL_EXPORT void
+wl_log_set_handler_client(wl_log_func_t handler)
+{
+	wl_log_handler = handler;
+}

src/wayland-client.h

@@ -96,6 +96,8 @@ uint32_t
 wl_display_get_global(struct wl_display *display,
 		      const char *interface, uint32_t version);
 
+void wl_log_set_handler_client(wl_log_func_t handler);
+
 #ifdef  __cplusplus
 }
 #endif

src/wayland-private.h

@@ -105,4 +105,8 @@ wl_closure_print(struct wl_closure *closure, struct wl_object *target, int send)
 void
 wl_closure_destroy(struct wl_closure *closure);
 
+extern wl_log_func_t wl_log_handler;
+
+void wl_log(const char *fmt, ...);
+
 #endif

src/wayland-server.c

@@ -1178,3 +1178,9 @@ wl_client_new_object(struct wl_client *client,
 				    interface, implementation, id, data);
 
 }
+
+WL_EXPORT void
+wl_log_set_handler_server(wl_log_func_t handler)
+{
+	wl_log_handler = handler;
+}

src/wayland-server.h

@@ -418,6 +418,8 @@ wl_buffer_is_shm(struct wl_buffer *buffer);
 int
 wl_display_init_shm(struct wl_display *display);
 
+void wl_log_set_handler_server(wl_log_func_t handler);
+
 #ifdef  __cplusplus
 }
 #endif

src/wayland-util.c

@@ -24,6 +24,7 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
+#include <stdarg.h>
 
 #include "wayland-util.h"
 #include "wayland-private.h"
@@ -270,3 +271,20 @@ wl_map_for_each(struct wl_map *map, wl_iterator_func_t func, void *data)
 	for_each_helper(&map->client_entries, func, data);
 	for_each_helper(&map->server_entries, func, data);
 }
+
+static void
+wl_log_noop_handler(const char *fmt, va_list arg)
+{
+}
+
+wl_log_func_t wl_log_handler = wl_log_noop_handler;
+
+void
+wl_log(const char *fmt, ...)
+{
+	va_list argp;
+
+	va_start(argp, fmt);
+	wl_log_handler(fmt, argp);
+	va_end(argp);
+}

src/wayland-util.h

@@ -30,6 +30,7 @@ extern "C" {
 #include <math.h>
 #include <stddef.h>
 #include <inttypes.h>
+#include <stdarg.h>
 
 /* GCC visibility */
 #if defined(__GNUC__) && __GNUC__ >= 4
@@ -203,6 +204,8 @@ static inline wl_fixed_t wl_fixed_from_int(int i)
 	return i * 256;
 }
 
+typedef void (*wl_log_func_t)(const char *, va_list);
+
 #ifdef  __cplusplus
 }
 #endif