libsaria: Change volume function

I introduced a function for directly setting the new volume level.  It
does not allow changing by some value.

include/libsaria/audio.h

@@ -21,8 +21,10 @@ class Audio
 		Audio();
 		~Audio();
 
+		/* Other functions */
 		void init(int, char **);
 		void load(string);
+		void set_volume(double);
 
 		/* Control functions */
 		bool play();

include/libsaria/libsaria.h

@@ -15,7 +15,9 @@ class Libsaria
 		Libsaria(int, char**);
 		~Libsaria();
 
+		/* Other functions */
 		void load(string);
+		void set_volume(double);
 		void register_callback(callback_t, void (*)());
 
 		/* Control functions */

libsaria/audio/volume.cpp

@@ -0,0 +1,10 @@
+
+#include <libsaria/audio.h>
+
+void Audio::set_volume(double volume)
+{
+	GValue value = { 0, };
+	g_value_init(&value, G_TYPE_DOUBLE);
+	g_value_set_double(&value, volume);
+	g_object_set_property(G_OBJECT(player), "volume", &value);
+}

libsaria/libsaria.cpp

@@ -15,3 +15,8 @@ void Libsaria::load(string filepath)
 	audio.load(filepath);
 	play();
 }
+
+void Libsaria::set_volume(double volume)
+{
+	audio.set_volume(volume);
+}