weston-log: Rename scope's 'begin_cb' callback to 'new_subscriber'

Rather than using 'begin_cb' rename it to a more suitable name.

Further more instead of using the scope use the subscription to pass as
an argument. The source scope is attached to the subscription when
creating it so we can access it that way.

This also adds a _complete and a _printf method for the subscription
such that the callbacks can use to write data to only _that_
subscription and to close/complete it, otherwise writing to a scope
results in writing to all subscriptions for that scope which is not
correct.

In the same time, the scope counter-parts of _write and _complete will
now use the subscription function as well.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Suggested-by: Daniel Stone <daniels@collabora.com>

4 files changed, 91 insertions, 26 deletions

diff --git a/include/libweston/weston-log.h b/include/libweston/weston-log.h
index 90bce786..c07ac75d 100644
--- a/include/libweston/weston-log.h
+++ b/include/libweston/weston-log.h
@@ -38,6 +38,7 @@ struct weston_compositor;
 struct weston_log_context;
 struct wl_display;
 struct weston_log_subscriber;
+struct weston_log_subscription;
 
 void
 weston_compositor_enable_debug_protocol(struct weston_compositor *);
@@ -56,14 +57,14 @@ struct weston_debug_stream;
  *
  * @memberof weston_log_scope
  */
-typedef void (*weston_log_scope_cb)(struct weston_log_scope *scope,
-				      void *user_data);
+typedef void (*weston_log_scope_cb)(struct weston_log_subscription *sub,
+				    void *user_data);
 
 struct weston_log_scope *
 weston_compositor_add_log_scope(struct weston_log_context *compositor,
 				  const char *name,
 				  const char *description,
-				  weston_log_scope_cb begin_cb,
+				  weston_log_scope_cb new_subscriber,
 				  void *user_data);
 
 void
@@ -85,8 +86,15 @@ weston_log_scope_printf(struct weston_log_scope *scope,
 			  const char *fmt, ...)
 			  __attribute__ ((format (printf, 2, 3)));
 void
+weston_log_subscription_printf(struct weston_log_subscription *scope,
+				const char *fmt, ...)
+			  __attribute__ ((format (printf, 2, 3)));
+void
 weston_log_scope_complete(struct weston_log_scope *scope);
 
+void
+weston_log_subscription_complete(struct weston_log_subscription *sub);
+
 char *
 weston_log_scope_timestamp(struct weston_log_scope *scope,
 			     char *buf, size_t len);
diff --git a/libweston/compositor.c b/libweston/compositor.c
index b637fbb7..f2ef3f5b 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -7143,14 +7143,14 @@ weston_compositor_print_scene_graph(struct weston_compositor *ec)
  * and then terminates the stream.
  */
 static void
-debug_scene_graph_cb(struct weston_log_scope *scope, void *data)
+debug_scene_graph_cb(struct weston_log_subscription *sub, void *data)
 {
 	struct weston_compositor *ec = data;
 	char *str = weston_compositor_print_scene_graph(ec);
 
-	weston_log_scope_printf(scope, "%s", str);
+	weston_log_subscription_printf(sub, "%s", str);
 	free(str);
-	weston_log_scope_complete(scope);
+	weston_log_subscription_complete(sub);
 }
 
 /** Create the compositor.
diff --git a/libweston/weston-log-internal.h b/libweston/weston-log-internal.h
index d8023358..265c0d3f 100644
--- a/libweston/weston-log-internal.h
+++ b/libweston/weston-log-internal.h
@@ -88,7 +88,7 @@ struct weston_log_scope *
 weston_log_get_scope(struct weston_log_context *log_ctx, const char *name);
 
 void
-weston_log_run_begin_cb(struct weston_log_scope *scope);
+weston_log_run_cb_new_subscriber(struct weston_log_subscription *sub);
 
 void
 weston_debug_protocol_advertise_scopes(struct weston_log_context *log_ctx,
diff --git a/libweston/weston-log.c b/libweston/weston-log.c
index 9caca22d..0fb03b45 100644
--- a/libweston/weston-log.c
+++ b/libweston/weston-log.c
@@ -74,7 +74,7 @@ struct weston_log_context {
 struct weston_log_scope {
 	char *name;
 	char *desc;
-	weston_log_scope_cb begin_cb;
+	weston_log_scope_cb new_subscriber;
 	void *user_data;
 	struct wl_list compositor_link;
 	struct wl_list subscription_list;  /**< weston_log_subscription::source_link */
@@ -164,6 +164,34 @@ weston_log_subscription_destroy_pending(struct weston_log_subscription *sub)
 	free(sub);
 }
 
+static void
+weston_log_subscription_write(struct weston_log_subscription *sub,
+			      const char *data, size_t len)
+{
+	if (sub->owner && sub->owner->write)
+		sub->owner->write(sub->owner, data, len);
+}
+
+static void
+weston_log_subscription_vprintf(struct weston_log_subscription *sub,
+				const char *fmt, va_list ap)
+{
+	static const char oom[] = "Out of memory";
+	char *str;
+	int len;
+
+	if (!weston_log_scope_is_enabled(sub->source))
+		return;
+
+	len = vasprintf(&str, fmt, ap);
+	if (len >= 0) {
+		weston_log_subscription_write(sub, str, len);
+		free(str);
+	} else {
+		weston_log_subscription_write(sub, oom, sizeof oom - 1);
+	}
+}
+
 /** Creates a new subscription using the subscriber by \c owner.
  *
  * The subscription created is added to the \c owner subscription list.
@@ -203,7 +231,7 @@ weston_log_subscription_create(struct weston_log_subscriber *owner,
 	wl_list_insert(&sub->owner->subscription_list, &sub->owner_link);
 
 	weston_log_subscription_add(scope, sub);
-	weston_log_run_begin_cb(scope);
+	weston_log_run_cb_new_subscriber(sub);
 }
 
 /** Destroys the subscription
@@ -306,16 +334,16 @@ weston_log_get_scope(struct weston_log_context *log_ctx, const char *name)
 	return NULL;
 }
 
-/** Wrapper to invoke the weston_log_scope_cb. Allows to call the begin_cb of
+/** Wrapper to invoke the weston_log_scope_cb. Allows to call the cb new_subscriber of
  * a log scope.
  *
  * @internal
  */
 void
-weston_log_run_begin_cb(struct weston_log_scope *scope)
+weston_log_run_cb_new_subscriber(struct weston_log_subscription *sub)
 {
-	if (scope->begin_cb)
-		scope->begin_cb(scope, scope->user_data);
+	if (sub->source->new_subscriber)
+		sub->source->new_subscriber(sub, sub->source->user_data);
 }
 
 /** Advertise the log scope name and the log scope description
@@ -464,7 +492,8 @@ weston_compositor_is_debug_protocol_enabled(struct weston_compositor *wc)
  * @param log_ctx The weston_log_context where to add.
  * @param name The debug stream/scope name; must not be NULL.
  * @param description The log scope description for humans; must not be NULL.
- * @param begin_cb Optional callback when a client subscribes to this scope.
+ * @param new_subscriber Optional callback when a client subscribes to this
+ * scope.
  * @param user_data Optional user data pointer for the callback.
  * @returns A valid pointer on success, NULL on failure.
  *
@@ -480,17 +509,17 @@ weston_compositor_is_debug_protocol_enabled(struct weston_compositor *wc)
  * protocol, the description is printed when a client asks for a list of
  * supported log scopes.
  *
- * \p begin_cb, if not NULL, is called when a client subscribes to the log
+ * \p new_subscriber, if not NULL, is called when a client subscribes to the log
  * scope creating a debug stream. This is for log scopes that need to print
  * messages as a response to a client appearing, e.g. printing a list of
  * windows on demand or a static preamble. The argument \p user_data is
  * passed in to the callback and is otherwise unused.
  *
- * For one-shot debug streams, \c begin_cb should finally call
- * weston_log_scope_complete() to close the stream and tell the client the
- * printing is complete. Otherwise the client expects more data to be written.
- * The complete callback in weston_log_subscriber should be installed to
- * trigger it and it is set-up automatically for the weston-debug protocol.
+ * For one-shot debug streams, \c new_subscriber should finally call
+ * weston_log_subscription_complete() to close the stream and tell the client
+ * the printing is complete. Otherwise the client expects more data to be
+ * written.  The complete callback in weston_log_subscriber should be installed
+ * to trigger it and it is set-up automatically for the weston-debug protocol.
  *
  * As subscription can take place before creating the scope, any pending
  * subscriptions to scope added by weston_log_subscribe(), will be checked
@@ -507,7 +536,7 @@ WL_EXPORT struct weston_log_scope *
 weston_compositor_add_log_scope(struct weston_log_context *log_ctx,
 				const char *name,
 				const char *description,
-				weston_log_scope_cb begin_cb,
+				weston_log_scope_cb new_subscriber,
 				void *user_data)
 {
 	struct weston_log_scope *scope;
@@ -539,7 +568,7 @@ weston_compositor_add_log_scope(struct weston_log_context *log_ctx,
 
 	scope->name = strdup(name);
 	scope->desc = strdup(description);
-	scope->begin_cb = begin_cb;
+	scope->new_subscriber = new_subscriber;
 	scope->user_data = user_data;
 	wl_list_init(&scope->subscription_list);
 
@@ -627,6 +656,16 @@ weston_log_scope_is_enabled(struct weston_log_scope *scope)
 	return !wl_list_empty(&scope->subscription_list);
 }
 
+/** Close the stream's complete callback if one was installed/created.
+ *
+ */
+WL_EXPORT void
+weston_log_subscription_complete(struct weston_log_subscription *sub)
+{
+	if (sub->owner && sub->owner->complete)
+		sub->owner->complete(sub->owner);
+}
+
 /** Close the log scope.
  *
  * @param scope The log scope to complete; may be NULL.
@@ -648,8 +687,7 @@ weston_log_scope_complete(struct weston_log_scope *scope)
 		return;
 
 	wl_list_for_each(sub, &scope->subscription_list, source_link)
-		if (sub->owner && sub->owner->complete)
-			sub->owner->complete(sub->owner);
+		weston_log_subscription_complete(sub);
 }
 
 /** Write log data for a scope
@@ -673,8 +711,7 @@ weston_log_scope_write(struct weston_log_scope *scope,
 		return;
 
 	wl_list_for_each(sub, &scope->subscription_list, source_link)
-		if (sub->owner && sub->owner->write)
-			sub->owner->write(sub->owner, data, len);
+		weston_log_subscription_write(sub, data, len);
 }
 
 /** Write a formatted string for a scope (varargs)
@@ -735,6 +772,26 @@ weston_log_scope_printf(struct weston_log_scope *scope,
 	va_end(ap);
 }
 
+/** Write a formatted string for a subscription
+ *
+ * \param sub The subscription to write for; may be NULL, in which case
+ *              nothing will be written.
+ * \param fmt Printf-style format string and arguments.
+ *
+ * Writes to formatted string to the stream that created the subscription.
+ *
+ */
+WL_EXPORT void
+weston_log_subscription_printf(struct weston_log_subscription *sub,
+			       const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	weston_log_subscription_vprintf(sub, fmt, ap);
+	va_end(ap);
+}
+
 /** Write debug scope name and current time into string
  *
  * \param[in] scope debug scope; may be NULL