JACK deal with the global msg callbacks

README.md

@@ -10,7 +10,7 @@ exposed.
 
 **This library is a work-in-progress.**
 
-## Features
+## Features and Limitations
 
  * Supported backends:
    - [PulseAudio](http://www.freedesktop.org/wiki/Software/PulseAudio/)

src/jack.cpp

@@ -7,10 +7,13 @@
 
 #include "jack.hpp"
 #include "soundio.hpp"
+#include "atomics.hpp"
 
 #include <jack/jack.h>
 #include <stdio.h>
 
+static atomic_flag global_msg_callback_flag = ATOMIC_FLAG_INIT;
+
 struct SoundIoJack {
     jack_client_t *client;
 };
@@ -96,16 +99,17 @@ static void destroy_jack(SoundIoPrivate *si) {
     si->backend_data = nullptr;
 }
 
-static void error_callback(const char *msg) {
-    //fprintf(stderr, "JACK error: %s\n", msg);
-}
-
-static void info_callback(const char *msg) {
-    //fprintf(stderr, "JACK info: %s\n", msg);
-}
-
 int soundio_jack_init(struct SoundIoPrivate *si) {
     SoundIo *soundio = &si->pub;
+
+    if (!global_msg_callback_flag.test_and_set()) {
+        if (soundio->jack_error_callback)
+            jack_set_error_function(soundio->jack_error_callback);
+        if (soundio->jack_info_callback)
+            jack_set_info_function(soundio->jack_info_callback);
+        global_msg_callback_flag.clear();
+    }
+
     assert(!si->backend_data);
     SoundIoJack *sij = create<SoundIoJack>();
     if (!sij) {
@@ -114,9 +118,6 @@ int soundio_jack_init(struct SoundIoPrivate *si) {
     }
     si->backend_data = sij;
 
-    jack_set_error_function(error_callback);
-    jack_set_info_function(info_callback);
-
     jack_status_t status;
     sij->client = jack_client_open(soundio->app_name, JackNoStartServer, &status);
     if (!sij->client) {

src/soundio.cpp

@@ -154,6 +154,7 @@ void soundio_destroy(struct SoundIo *soundio) {
 
 static void default_on_devices_change(struct SoundIo *) { }
 static void default_on_events_signal(struct SoundIo *) { }
+static void default_msg_callback(const char *msg) { }
 
 struct SoundIo * soundio_create(void) {
     soundio_os_init();
@@ -164,6 +165,8 @@ struct SoundIo * soundio_create(void) {
     soundio->on_devices_change = default_on_devices_change;
     soundio->on_events_signal = default_on_events_signal;
     soundio->app_name = "SoundIo";
+    soundio->jack_info_callback = default_msg_callback;
+    soundio->jack_error_callback = default_msg_callback;
     return soundio;
 }
 

src/soundio.h

@@ -212,6 +212,13 @@ struct SoundIo {
     // PulseAudio uses this for "application name".
     // JACK uses this for `client_name`.
     const char *app_name;
+
+    // Optional: JACK info and error callbacks.
+    // By default, libsoundio sets these to empty functions in order to
+    // silence stdio messages from JACK. You may override the behavior by
+    // setting these to `NULL` or providing your own function.
+    void (*jack_info_callback)(const char *msg);
+    void (*jack_error_callback)(const char *msg);
 };
 
 // The size of this struct is not part of the API or ABI.
@@ -426,11 +433,10 @@ struct SoundIo * soundio_create(void);
 void soundio_destroy(struct SoundIo *soundio);
 
 
-// Provided these backends were compiled in, this tries JACK, then PulseAudio,
-// then ALSA, then CoreAudio, then ASIO, then DirectSound, then OSS, then Dummy.
+// This is a convenience function you could implement yourself if you wanted
+// to. It tries `soundio_connect_backend` on all available backends in order.
 int soundio_connect(struct SoundIo *soundio);
 // Instead of calling `soundio_connect` you may call this function to try a
-// specific backend.
 int soundio_connect_backend(struct SoundIo *soundio, enum SoundIoBackend backend);
 void soundio_disconnect(struct SoundIo *soundio);