info: allow getting other log categories. Fixes #587417

Add a new macro GST_DEBUG_CATEGORY_GET to get a log category by name. This
allows plugins to use e.g. core categories like PERFORMANCE or CLOCK.
API: GST_DEBUG_CATEGORY_GET

docs/gst/gstreamer-sections.txt

@@ -970,6 +970,7 @@ GST_DEBUG_CATEGORY
 GST_DEBUG_CATEGORY_EXTERN
 GST_DEBUG_CATEGORY_STATIC
 GST_DEBUG_CATEGORY_INIT
+GST_DEBUG_CATEGORY_GET
 gst_debug_category_free
 gst_debug_category_set_threshold
 gst_debug_category_reset_threshold

gst/gstinfo.c

@@ -1470,6 +1470,21 @@ gst_debug_get_all_categories (void)
   return ret;
 }
 
+GstDebugCategory *
+_gst_debug_get_category (const gchar * name)
+{
+  GstDebugCategory *ret = NULL;
+  GSList *node;
+
+  for (node = __categories; node; node = g_slist_next (node)) {
+    ret = (GstDebugCategory *) node->data;
+    if (!strcmp (name, ret->name)) {
+      return ret;
+    }
+  }
+  return NULL;
+}
+
 /*** FUNCTION POINTERS ********************************************************/
 
 static GHashTable *__gst_function_pointers;     /* NULL */

gst/gstinfo.h

@@ -350,7 +350,8 @@ void            gst_debug_unset_threshold_for_name  (const gchar * name);
  * This macro expands to nothing if debugging is disabled.
  */
 #define GST_DEBUG_CATEGORY_STATIC(cat) static GstDebugCategory *cat = NULL
-/* do not use this function, use the macros below */
+
+/* do not use this function, use the GST_DEBUG_CATEGORY_INIT macro below */
 GstDebugCategory *_gst_debug_category_new (const gchar * name,
                                            guint         color,
                                            const gchar * description);
@@ -408,6 +409,41 @@ G_CONST_RETURN gchar *
 GSList *
         gst_debug_get_all_categories	(void);
 
+/* do not use this function, use the GST_DEBUG_CATEGORY_GET macro below */
+GstDebugCategory *_gst_debug_get_category (const gchar *name);
+
+/**
+ * GST_DEBUG_CATEGORY_GET:
+ * @cat: the category to initialize.
+ * @name: log category name
+ *
+ * Lookup an exiting #GstDebugCategory by its @name and sets @cat. If category
+ * is not found, but %GST_CAT_DEFAULT is defined, that is assigned to @cat.
+ * Otherwise cat will be NULL.
+ *
+ * |[
+ * GST_DEBUG_CATEGORY_STATIC (gst_myplugin_debug);
+ * #define GST_CAT_DEFAULT gst_myplugin_debug
+ * GST_DEBUG_CATEGORY_STATIC (GST_CAT_PERFORMANCE);
+ * ...
+ * GST_DEBUG_CATEGORY_INIT (gst_myplugin_debug, "myplugin", 0, "nice element");
+ * GST_DEBUG_CATEGORY_GET (GST_CAT_PERFORMANCE, "performance);
+ * ]|
+ */
+#ifdef GST_CAT_DEFAULT
+#define GST_DEBUG_CATEGORY_GET(cat,name)  G_STMT_START{\
+  cat = _gst_debug_get_category (name);			\
+  if (!cat) {						\
+    cat = GST_CAT_DEFAULT;				\
+  }							\
+}G_STMT_END
+#else
+#define GST_DEBUG_CATEGORY_GET(cat,name)  G_STMT_START{\
+  cat = _gst_debug_get_category (name);			\
+}G_STMT_END
+#endif
+
+
 gchar * gst_debug_construct_term_color	(guint colorinfo);
 gint    gst_debug_construct_win_color (guint colorinfo);
 
@@ -1126,6 +1162,7 @@ guint gst_debug_remove_log_function_by_data (gpointer data);
 #define GST_DEBUG_CATEGORY_STATIC(var)			/* NOP */
 #endif
 #define GST_DEBUG_CATEGORY_INIT(var,name,color,desc)	/* NOP */
+#define GST_DEBUG_CATEGORY_GET(var,name)		/* NOP */
 #define gst_debug_category_free(category)		/* NOP */
 #define gst_debug_category_set_threshold(category,level) /* NOP */
 #define gst_debug_category_reset_threshold(category)	/* NOP */

win32/common/libgstreamer.def

@@ -39,6 +39,7 @@ EXPORTS
 	_gst_debug_bin_to_dot_file_with_ts
 	_gst_debug_category_new
 	_gst_debug_dump_mem
+	_gst_debug_get_category
 	_gst_debug_nameof_funcptr
 	_gst_debug_register_funcptr
 	_gst_element_error_printf