add a demo program for fluid_audio_driver_register()

doc/fluidsynth_register_adriver.c

@@ -0,0 +1,49 @@
+/**
+ * This is a simple C99 program that demonstrates the usage of fluid_audio_driver_register()
+ * 
+ * There are 3 calls to fluid_audio_driver_register(), i.e. 3 iterations:
+ * First the alsa driver is registered and created, followed by the jack and portaudio driver.
+ * 
+ * The usual usecase would be to call fluid_audio_driver_register() only once providing the audio drivers needed during fluidsynth usage.
+ * If necessary however fluid_audio_driver_register() can be called multiple times as demonstrated here.
+ * Therefore the user must make sure to delete all fluid-instances of any kind before making the call to fluid_audio_driver_register().
+ * Else the behaviour is undefined and the application is likely to crash.
+ */
+
+#include <stdio.h>
+#include <fluidsynth.h>
+
+int main()
+{
+    const char* DRV[] = { "alsa", "jack", "portaudio" };
+    const char* adrivers[2];
+    
+    for(int i=0; i<sizeof(DRV)/sizeof(DRV[0]); i++)
+    {
+        adrivers[0] = DRV[i];
+        adrivers[1] = NULL;
+
+        int res = fluid_audio_driver_register(adrivers);
+        if(res != FLUID_OK)
+        {
+            puts("adriver reg err");
+            return -1;
+        }
+
+        fluid_settings_t* settings = new_fluid_settings();
+        res = fluid_settings_setstr(settings, "audio.driver", DRV[i]);
+        if(res != FLUID_OK)
+        {
+            puts("audio.driver set err");
+            return -1;
+        }
+
+        fluid_synth_t* synth = new_fluid_synth(settings);
+        fluid_audio_driver_t* ad = new_fluid_audio_driver(settings, synth);
+
+        delete_fluid_audio_driver(ad);
+        delete_fluid_synth(synth);
+        delete_fluid_settings(settings);
+    }
+    return 0;
+}