From 6877ac820b149fab1cae75633a5efd6dab5adb47 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sun, 2 Dec 2018 02:04:21 +0100
Subject: [PATCH] Don't invalidate AU preset on load

This works around async parameter-changed signal emission when loading
an AU preset. A simple timeout is used to delay making the preset
as modified.
---
 libs/ardour/ardour/audio_unit.h |  5 +++--
 libs/ardour/audio_unit.cc       | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/libs/ardour/ardour/audio_unit.h b/libs/ardour/ardour/audio_unit.h
index 55faf4a08e..454a7d1ce0 100644
--- a/libs/ardour/ardour/audio_unit.h
+++ b/libs/ardour/ardour/audio_unit.h
@@ -228,8 +228,9 @@ class LIBARDOUR_API AUPlugin : public ARDOUR::Plugin
 	void discover_factory_presets ();
 
 	samplepos_t transport_sample;
-	float      transport_speed;
-	float      last_transport_speed;
+	float       transport_speed;
+	float       last_transport_speed;
+	pframes_t   preset_holdoff;
 
 	static void _parameter_change_listener (void* /*arg*/, void* /*src*/, const AudioUnitEvent* event, UInt64 host_time, Float32 new_value);
 	void parameter_change_listener (void* /*arg*/, void* /*src*/, const AudioUnitEvent* event, UInt64 host_time, Float32 new_value);
diff --git a/libs/ardour/audio_unit.cc b/libs/ardour/audio_unit.cc
index 812d004e6a..559961b0b2 100644
--- a/libs/ardour/audio_unit.cc
+++ b/libs/ardour/audio_unit.cc
@@ -452,6 +452,7 @@ AUPlugin::AUPlugin (AudioEngine& engine, Session& session, boost::shared_ptr<CAC
 	, transport_sample (0)
 	, transport_speed (0)
 	, last_transport_speed (0.0)
+	, preset_holdoff (0)
 {
 	if (!preset_search_path_initialized) {
 		Glib::ustring p = Glib::get_home_dir();
@@ -493,6 +494,7 @@ AUPlugin::AUPlugin (const AUPlugin& other)
 	, transport_sample (0)
 	, transport_speed (0)
 	, last_transport_speed (0.0)
+	, preset_holdoff (0)
 
 {
 	init ();
@@ -1651,6 +1653,10 @@ AUPlugin::connect_and_run (BufferSet& bufs,
 	AudioTimeStamp ts;
 	OSErr err;
 
+	if (preset_holdoff > 0) {
+		preset_holdoff -= std::min (nframes, preset_holdoff);
+	}
+
 	if (requires_fixed_size_buffers() && (nframes != _last_nframes)) {
 		unit->GlobalReset();
 		_last_nframes = nframes;
@@ -2215,6 +2221,9 @@ AUPlugin::load_preset (PresetRecord r)
 			AUParameterListenerNotify (NULL, NULL, &changedUnit);
 		}
 	}
+	if (ret) {
+		preset_holdoff = std::max (_session.get_block_size() * 2.0, _session.sample_rate() * .2);
+	}
 
 	return ret && Plugin::load_preset (r);
 }
@@ -3500,7 +3509,11 @@ AUPlugin::parameter_change_listener (void* /*arg*/, void* src, const AudioUnitEv
                 /* whenever we change a parameter, we request that we are NOT notified of the change, so anytime we arrive here, it
                    means that something else (i.e. the plugin GUI) made the change.
                 */
-                Plugin::parameter_changed_externally (i->second, new_value);
+                if (preset_holdoff > 0) {
+	                ParameterChangedExternally (i->second, new_value);
+                } else {
+                        Plugin::parameter_changed_externally (i->second, new_value);
+		}
                 break;
         default:
                 break;
-- 
2.30.2