command: allow clients to subscribe to specific idle events

The client may provide the names of idle events as arguments to the
"idle" command to inform MPD that it is only interested in these
events.

src/client.c

@@ -91,6 +91,9 @@ struct client {
 	/** idle flags pending on this client, to be sent as soon as
 	    the client enters "idle" */
 	unsigned idle_flags;
+
+	/** idle flags that the client wants to receive */
+	unsigned idle_subscriptions;
 };
 
 static LIST_HEAD(clients);
@@ -766,16 +769,6 @@ mpd_fprintf void client_printf(struct client *client, const char *fmt, ...)
 	va_end(args);
 }
 
-static const char *const idle_names[] = {
-	"database",
-	"stored_playlist",
-	"playlist",
-	"player",
-	"mixer",
-	"output",
-	"options",
-};
-
 /**
  * Send "idle" response to this client.
  */
@@ -783,6 +776,7 @@ static void
 client_idle_notify(struct client *client)
 {
 	unsigned flags, i;
+	const char *const* idle_names;
 
 	assert(client->idle_waiting);
 	assert(client->idle_flags != 0);
@@ -791,10 +785,9 @@ client_idle_notify(struct client *client)
 	client->idle_flags = 0;
 	client->idle_waiting = false;
 
-	for (i = 0; i < sizeof(idle_names) / sizeof(idle_names[0]); ++i) {
-		assert(idle_names[i] != NULL);
-
-		if (flags & (1 << i))
+	idle_names = idle_get_names();
+	for (i = 0; idle_names[i]; ++i) {
+		if (flags & (1 << i) & client->idle_subscriptions)
 			client_printf(client, "changed: %s\n",
 				      idle_names[i]);
 	}
@@ -814,20 +807,22 @@ void client_manager_idle_add(unsigned flags)
 			continue;
 
 		client->idle_flags |= flags;
-		if (client->idle_waiting) {
+		if (client->idle_waiting
+		    && (client->idle_flags & client->idle_subscriptions)) {
 			client_idle_notify(client);
 			client_write_output(client);
 		}
 	}
 }
 
-bool client_idle_wait(struct client *client)
+bool client_idle_wait(struct client *client, unsigned flags)
 {
 	assert(!client->idle_waiting);
 
 	client->idle_waiting = true;
+	client->idle_subscriptions = flags;
 
-	if (client->idle_flags != 0) {
+	if (client->idle_flags & client->idle_subscriptions) {
 		client_idle_notify(client);
 		return true;
 	} else

src/client.h

@@ -78,6 +78,6 @@ void client_manager_idle_add(unsigned flags);
  * sent immediately and "true" is returned".  If no, it puts the
  * client into waiting mode and returns false.
  */
-bool client_idle_wait(struct client *client);
+bool client_idle_wait(struct client *client, unsigned flags);
 
 #endif

src/command.c

@@ -39,6 +39,7 @@
 #include "tag_print.h"
 #include "path.h"
 #include "os_compat.h"
+#include "idle.h"
 
 #define COMMAND_STATUS_VOLUME           "volume"
 #define COMMAND_STATUS_STATE            "state"
@@ -1253,8 +1254,28 @@ static enum command_return
 handle_idle(struct client *client,
 	    mpd_unused int argc, mpd_unused char *argv[])
 {
+        unsigned flags = 0, j;
+        int i;
+        const char *const* idle_names;
+
+        idle_names = idle_get_names();
+        for (i = 1; i < argc; ++i) {
+                if (!argv[i])
+                        continue;
+
+                for (j = 0; idle_names[j]; ++j) {
+                        if (!strcasecmp(argv[i], idle_names[j])) {
+                                flags |= (1 << j);
+                        }
+                }
+        }
+
+        /* No argument means that the client wants to receive everything */
+        if (flags == 0)
+                flags = ~0;
+
 	/* enable "idle" mode on this client */
-	client_idle_wait(client);
+	client_idle_wait(client, flags);
 
 	/* return value is "1" so the caller won't print "OK" */
 	return 1;
@@ -1280,7 +1301,7 @@ static const struct command commands[] = {
 	{ "disableoutput", PERMISSION_ADMIN, 1, 1, handle_disableoutput },
 	{ "enableoutput", PERMISSION_ADMIN, 1, 1, handle_enableoutput },
 	{ "find", PERMISSION_READ, 2, -1, handle_find },
-	{ "idle", PERMISSION_READ, 0, 0, handle_idle },
+	{ "idle", PERMISSION_READ, 0, -1, handle_idle },
 	{ "kill", PERMISSION_ADMIN, -1, -1, handle_kill },
 	{ "list", PERMISSION_READ, 1, -1, handle_list },
 	{ "listall", PERMISSION_READ, 0, 1, handle_listall },

src/idle.c

@@ -30,6 +30,18 @@
 static unsigned idle_flags;
 static pthread_mutex_t idle_mutex = PTHREAD_MUTEX_INITIALIZER;
 
+static const char *const idle_names[] = {
+	"database",
+	"stored_playlist",
+	"playlist",
+	"player",
+	"mixer",
+	"output",
+	"options",
+	"elapsed",
+        NULL
+};
+
 void
 idle_add(unsigned flags)
 {
@@ -54,3 +66,9 @@ idle_get(void)
 
 	return flags;
 }
+
+const char*const*
+idle_get_names(void)
+{
+        return idle_names;
+}

src/idle.h

@@ -61,4 +61,10 @@ idle_add(unsigned flags);
 unsigned
 idle_get(void);
 
+/**
+ * Get idle names
+ */
+const char*const*
+idle_get_names(void);
+
 #endif