Fix flow for latency measurements that needs an engine stop.

Make AudioEngine::prepare_for_latency_measurement() idempotent. There are
multple calls (when switching to the measurement page and every time
a measurement is preformed).

Also the Stopped() signal is important for the Dialog state regardless
if the engine was stopped for latency or not.

1 files changed, 5 insertions, 1 deletions

diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index 96445b5973..1a09a7f0eb 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -956,7 +956,7 @@ AudioEngine::stop (bool for_latency)
 		Port::PortDrop ();
 	}
 
-	if (!for_latency && stop_engine) {
+	if (stop_engine) {
 		Stopped (); /* EMIT SIGNAL */
 	}
 
@@ -1331,6 +1331,10 @@ AudioEngine::prepare_for_latency_measurement ()
 		return -1;
 	}
 
+	if (running() && _started_for_latency) {
+		return 0;
+	}
+
 	if (_backend->can_change_systemic_latency_when_running()) {
 		if (start()) {
 			return -1;