obs/tools: Add active_source and visible_source helpers

These classes help us manage active and showing references to a source, which seem to be necessary for filters.

source/obs/obs-tools.hpp

@@ -36,6 +36,35 @@ namespace obs {
 
 			std::shared_ptr<obs_source_t> get();
 		};
+
+		// Class to manage
+		class active_source {
+			obs_source_t* _child;
+
+			public:
+			active_source(obs_source_t* child) : _child(child)
+			{
+				obs_source_inc_active(_child);
+			}
+			virtual ~active_source()
+			{
+				obs_source_dec_active(_child);
+			}
+		};
+
+		class visible_source {
+			obs_source_t* _child;
+
+			public:
+			visible_source(obs_source_t* child) : _child(child)
+			{
+				obs_source_inc_showing(_child);
+			}
+			virtual ~visible_source()
+			{
+				obs_source_dec_showing(_child);
+			}
+		};
 	} // namespace tools
 
 	inline void obs_source_deleter(obs_source_t* v)