weston-log: add function to avoid direct access to compositor members in non-core code

If we use the function weston_log_context_add_log_scope()
in non-core code, it's necessary to access
weston_compositor::weston_log_ctx.

This is not ideal, since the goal is to make core structs
(weston_compositor, weston_surface, weston_output, etc)
opaque.

Add function weston_compositor_add_log_scope(), so non-core
users are able to pass weston_compositor as argument instead
of weston_compositor::weston_log_ctx.

Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>

doc/sphinx/toc/libweston/log.rst

@@ -26,11 +26,11 @@ Instantiation of the :type:`weston_log_context` object takes place using
 Log scopes
 ----------
 
-A scope represents a source for a data stream (i.e., a producer). You'll require
-one as a way to generate data. Creating a log scope is done using
-:func:`weston_log_ctx_add_log_scope()`. You can customize the scope
-behaviour and you'll require at least a name and a description for the
-scope.
+A scope represents a source for a data stream (i.e., a producer). You'll
+require one as a way to generate data. Creating a log scope is done using
+:func:`weston_log_ctx_add_log_scope()` or
+:func:`weston_compositor_add_log_scope()`. You can customize the scope
+behaviour and you'll require at least a name and a description for the scope.
 
 .. note::
 

include/libweston/weston-log.h

@@ -55,7 +55,7 @@ struct weston_debug_stream;
  *
  * @param sub The subscription.
  * @param user_data The \c user_data argument given to
- * weston_log_ctx_add_log_scope()
+ * weston_log_ctx_add_log_scope() or weston_compositor_add_log_scope().
  *
  * @memberof weston_log_scope
  */
@@ -70,6 +70,14 @@ weston_log_ctx_add_log_scope(struct weston_log_context *log_ctx,
 			     weston_log_scope_cb destroy_subscription,
 			     void *user_data);
 
+struct weston_log_scope *
+weston_compositor_add_log_scope(struct weston_compositor *compositor,
+				const char *name,
+				const char *description,
+				weston_log_scope_cb new_subscription,
+				weston_log_scope_cb destroy_subscription,
+				void *user_data);
+
 void
 weston_log_scope_destroy(struct weston_log_scope *scope);
 

libweston/weston-log.c

@@ -355,7 +355,8 @@ weston_log_subscription_remove(struct weston_log_subscription *sub)
  * matching against the \c name.
  *
  * @param log_ctx
- * @param name the scope name, see weston_log_ctx_add_log_scope()
+ * @param name the scope name, see weston_log_ctx_add_log_scope() and
+ * weston_compositor_add_log_scope()
  * @returns NULL if none found, or a pointer to a weston_log_scope
  *
  * @ingroup internal-log
@@ -644,6 +645,42 @@ weston_log_ctx_add_log_scope(struct weston_log_context *log_ctx,
 	return scope;
 }
 
+/** Register a new stream name, creating a log scope.
+ *
+ * @param compositor The compositor that contains the log context where the log
+ * scope will be linked.
+ * @param name The debug stream/scope name; must not be NULL.
+ * @param description The log scope description for humans; must not be NULL.
+ * @param new_subscription Optional callback when a client subscribes to this
+ * scope.
+ * @param destroy_subscription Optional callback when a client destroys the
+ * subscription.
+ * @param user_data Optional user data pointer for the callback.
+ * @returns A valid pointer on success, NULL on failure.
+ *
+ * This function works like weston_log_ctx_add_log_scope(), but the log scope
+ * created is linked to the log context of \c compositor.
+ *
+ * @memberof weston_compositor
+ * @sa weston_log_ctx_add_log_scope
+ */
+WL_EXPORT struct weston_log_scope *
+weston_compositor_add_log_scope(struct weston_compositor *compositor,
+				const char *name,
+				const char *description,
+				weston_log_scope_cb new_subscription,
+				weston_log_scope_cb destroy_subscription,
+				void *user_data)
+{
+	struct weston_log_scope *scope;
+	scope = weston_log_ctx_add_log_scope(compositor->weston_log_ctx,
+					     name, description,
+ 					     new_subscription,
+					     destroy_subscription,
+					     user_data);
+	return scope;
+}
+
 /** Destroy a log scope
  *
  * @param scope The log scope to destroy; may be NULL.
@@ -896,9 +933,10 @@ weston_log_scope_timestamp(struct weston_log_scope *scope,
  * to the scope \c scope_name.
  *
  * If \c scope_name has already been created (using
- * weston_log_ctx_add_log_scope) the subscription will take place
- * immediately, otherwise we store the subscription into a pending list. See
- * also weston_log_ctx_add_log_scope().
+ * weston_log_ctx_add_log_scope or weston_compositor_add_log_scope) the
+ * subscription will take place immediately, otherwise we store the
+ * subscription into a pending list. See also weston_log_ctx_add_log_scope()
+ * and weston_compositor_add_log_scope()
  *
  * @param log_ctx the log context, used for accessing pending list
  * @param subscriber the subscriber, which has to be created before