Add 'update_properties' signal and obs_source_update_properties call

obs_source_update_properties should be called by sources when property
values change, e.g. a capture device source would use this when it
detects a new capture device (in case its properties contain a list of
available capture devices or similar)

libobs/obs-source.c

@@ -82,6 +82,7 @@ static const char *source_signals[] = {
 	"void volume(ptr source, in out float volume)",
 	"void volume_level(ptr source, float level, float magnitude, "
 		"float peak)",
+	"void update_properties(ptr source)",
 	NULL
 };
 
@@ -389,6 +390,21 @@ void obs_source_update(obs_source_t *source, obs_data_t *settings)
 	}
 }
 
+void obs_source_update_properties(obs_source_t *source)
+{
+	calldata_t calldata;
+
+	if (!source) return;
+
+	calldata_init(&calldata);
+	calldata_set_ptr(&calldata, "source", source);
+
+	signal_handler_signal(obs_source_get_signal_handler(source),
+			"update_properties", &calldata);
+
+	calldata_free(&calldata);
+}
+
 void obs_source_send_mouse_click(obs_source_t *source,
 		const struct obs_mouse_event *event,
 		int32_t type, bool mouse_up,

libobs/obs.h

@@ -730,6 +730,9 @@ EXPORT void obs_source_output_video(obs_source_t *source,
 EXPORT void obs_source_output_audio(obs_source_t *source,
 		const struct obs_source_audio *audio);
 
+/** Signal an update to any currently used properties via 'update_properties' */
+EXPORT void obs_source_update_properties(obs_source_t *source);
+
 /** Gets the current async video frame */
 EXPORT struct obs_source_frame *obs_source_get_frame(obs_source_t *source);