Listen for MIDI event through ALSA "virtual" rawmidi interface

[scherzo] / scherzo.c

diff --git a/scherzo.c b/scherzo.c
index bdd1a0fe5c7dbe86e97cf1c2a219e17815b9873e..0ef44ea1b362bba96e6b3edc63160cfdd6e97af0 100644 (file)
--- a/scherzo.c
+++ b/scherzo.c
@@ -66,8 +66,6 @@ typedef struct scherzo
      * keyboard". Any "piano keyboard" key knows its own octave and
      * accidental already. */
     int keyboard_octave;
-
-    int midi_fd;
     snd_midi_event_t *snd_midi_event;
 
     mnemon_t mnemon;
@@ -1182,17 +1180,25 @@ _score_challenge (scherzo_t *scherzo)
 }
 #endif
 
+typedef struct
+{
+    scherzo_t *scherzo;
+    int fd;
+} scherzo_midi_closure_t;
+
 static int
 on_midi_input (unused (GIOChannel *channel),
               unused (GIOCondition condition),
               void *user_data)
 {
+    scherzo_midi_closure_t *closure = user_data;
     unsigned char buf[MIDI_BUF_SIZE], *next;
-    scherzo_t *scherzo = user_data;
+    scherzo_t *scherzo = closure->scherzo;
+    int fd = closure->fd;
     ssize_t remaining;
     snd_seq_event_t event;
 
-    remaining = read (scherzo->midi_fd, buf, MIDI_BUF_SIZE);
+    remaining = read (fd, buf, MIDI_BUF_SIZE);
 
     next = buf;
     while (remaining) {
@@ -1244,11 +1250,38 @@ on_midi_input (unused (GIOChannel *channel),
     return TRUE;
 }
 
+static void *
+listen_to_alsa_midi (void *data)
+{
+    scherzo_midi_closure_t *closure = data;
+    int out_fd = closure->fd;
+    snd_rawmidi_t *midi_in;
+    unsigned char buf[MIDI_BUF_SIZE];
+    ssize_t bytes;
+    int err;
+
+    err = snd_rawmidi_open (&midi_in, NULL, "virtual", 0);
+    if (err) {
+       fprintf (stderr, "Failed to open virtual MIDI handle.");
+       return NULL;
+    }
+
+    while (1) {
+       bytes = snd_rawmidi_read (midi_in, buf, MIDI_BUF_SIZE);
+       write (out_fd, buf, bytes);
+    }
+
+    return NULL;
+}
+
 int
 main (int argc, char *argv[])
 {
     GtkWidget *drawing_area;
+    GIOChannel *channel;
     scherzo_t scherzo;
+    int alsa_midi_fd[2];
+    scherzo_midi_closure_t midi_out, alsa_midi_in, alsa_midi_out;
     int err;
 
     srand (time (NULL));
@@ -1294,17 +1327,29 @@ main (int argc, char *argv[])
     }
 
 #define MIDI_DEVICE "/dev/midi1"
-    scherzo.midi_fd = open (MIDI_DEVICE, O_RDONLY);
-    if (scherzo.midi_fd < 0) {
-       printf ("failed to open " MIDI_DEVICE ". Midi input will not be available.\n");
-    } else {
-       GIOChannel *channel;
 
-       channel = g_io_channel_unix_new (scherzo.midi_fd);
+    midi_out.scherzo = &scherzo;
+    midi_out.fd = open (MIDI_DEVICE, O_RDONLY);
+    if (midi_out.fd < 0) {
+       printf ("Failed to open " MIDI_DEVICE ". You will need to connect a MIDI device.\n");
+    } else {
+       channel = g_io_channel_unix_new (midi_out.fd);
        g_io_channel_set_encoding (channel, NULL, NULL);
-       g_io_add_watch (channel, G_IO_IN, on_midi_input, &scherzo);
+       g_io_add_watch (channel, G_IO_IN, on_midi_input, &midi_out);
     }
 
+    pipe (alsa_midi_fd);
+
+    alsa_midi_in.scherzo = &scherzo;
+    alsa_midi_in.fd = alsa_midi_fd[1];
+    g_thread_new ("scherzo-vmidi", listen_to_alsa_midi, &alsa_midi_in);
+
+    alsa_midi_out.scherzo = &scherzo;
+    alsa_midi_out.fd = alsa_midi_fd[0];
+    channel = g_io_channel_unix_new (alsa_midi_out.fd);
+    g_io_channel_set_encoding (channel, NULL, NULL);
+    g_io_add_watch (channel, G_IO_IN, on_midi_input, &alsa_midi_out);
+
     scherzo.window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
 
     gtk_window_set_default_size (GTK_WINDOW (scherzo.window), 1000, 600);