From b718c77fe338c18b61280aefcf8d42c01a6299fd Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Wed, 12 Apr 2017 20:19:08 +0200
Subject: Refuse to start if driver requires a graph and one is not provided

---
 ingen/EngineBase.hpp  | 9 +++++++++
 src/ingen/ingen.cpp   | 9 ++++++++-
 src/server/Engine.cpp | 6 ++++++
 src/server/Engine.hpp | 1 +
 4 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/ingen/EngineBase.hpp b/ingen/EngineBase.hpp
index f857f14a..272faa47 100644
--- a/ingen/EngineBase.hpp
+++ b/ingen/EngineBase.hpp
@@ -48,6 +48,15 @@ public:
 	                  uint32_t block_length,
 	                  size_t   seq_size) = 0;
 
+	/**
+	   Return true iff the engine and driver supports dynamic ports.
+
+	   This returns false in situations where top level ports can not be
+	   created once the driver is running, which is the case for most
+	   environments outside Jack.
+	*/
+	virtual bool supports_dynamic_ports() const = 0;
+
 	/**
 	   Activate the engine.
 	*/
diff --git a/src/ingen/ingen.cpp b/src/ingen/ingen.cpp
index 1932b793..4eacfa97 100644
--- a/src/ingen/ingen.cpp
+++ b/src/ingen/ingen.cpp
@@ -158,7 +158,14 @@ main(int argc, char** argv)
 		if (!world->load_module("jack") && !world->load_module("portaudio")) {
 			cerr << "ingen: error: Failed to load driver module" << endl;
 			delete world;
-			exit(EXIT_FAILURE);
+			return EXIT_FAILURE;
+		}
+
+		if (!world->engine()->supports_dynamic_ports() &&
+		    !conf.option("load").is_valid()) {
+			cerr << "ingen: error: Initial graph required for driver" << endl;
+			delete world;
+			return EXIT_FAILURE;
 		}
 	}
 
diff --git a/src/server/Engine.cpp b/src/server/Engine.cpp
index 2fa079f1..8ec74829 100644
--- a/src/server/Engine.cpp
+++ b/src/server/Engine.cpp
@@ -399,6 +399,12 @@ Engine::init(double sample_rate, uint32_t block_length, size_t seq_size)
 	set_driver(SPtr<Driver>(new DirectDriver(*this, sample_rate, block_length, seq_size)));
 }
 
+bool
+Engine::supports_dynamic_ports() const
+{
+	return !_driver || _driver->dynamic_ports();
+}
+
 bool
 Engine::activate()
 {
diff --git a/src/server/Engine.hpp b/src/server/Engine.hpp
index f951eaf3..cf13f5e6 100644
--- a/src/server/Engine.hpp
+++ b/src/server/Engine.hpp
@@ -77,6 +77,7 @@ public:
 
 	// EngineBase methods
 	virtual void init(double sample_rate, uint32_t block_length, size_t seq_size);
+	virtual bool supports_dynamic_ports() const;
 	virtual bool activate();
 	virtual void deactivate();
 	virtual bool pending_events() const;
-- 
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