From 75699e384f6b89869e098badb4997764df49aaa9 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Tue, 21 Dec 2021 15:15:06 -0700
Subject: [PATCH] triggerbox: start of "pending" architecture to allow for
 thread-safe swapping of slot contents (Triggers)

---
 libs/ardour/ardour/triggerbox.h |  4 ++++
 libs/ardour/triggerbox.cc       | 41 +++++++++++++++++++++++++++++++--
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/libs/ardour/ardour/triggerbox.h b/libs/ardour/ardour/triggerbox.h
index b67157c4fd..fde62f6680 100644
--- a/libs/ardour/ardour/triggerbox.h
+++ b/libs/ardour/ardour/triggerbox.h
@@ -483,6 +483,8 @@ class LIBARDOUR_API TriggerBox : public Processor
 	bool unbang_trigger (TriggerPtr);
 	void add_trigger (TriggerPtr);
 
+	void set_pending (uint32_t slot, TriggerPtr);
+
 	XMLNode& get_state (void);
 	int set_state (const XMLNode&, int version);
 
@@ -511,6 +513,7 @@ class LIBARDOUR_API TriggerBox : public Processor
 	void set_pass_thru (bool yn);
 
 	void request_reload (int32_t slot, void*);
+	void set_region (uint32_t slot, boost::shared_ptr<Region> region);
 
 	enum TriggerMidiMapMode {
 		AbletonPush,
@@ -554,6 +557,7 @@ class LIBARDOUR_API TriggerBox : public Processor
 	int32_t _order;
 	Glib::Threads::RWLock trigger_lock; /* protects all_triggers */
 	Triggers all_triggers;
+	Triggers pending;
 	PBD::RingBuffer<uint32_t> explicit_queue; /* user queued triggers */
 	TriggerPtr _currently_playing;
 	Requests _requests;
diff --git a/libs/ardour/triggerbox.cc b/libs/ardour/triggerbox.cc
index 7f842f5e2d..2d243229d4 100644
--- a/libs/ardour/triggerbox.cc
+++ b/libs/ardour/triggerbox.cc
@@ -274,7 +274,13 @@ Trigger::set_quantization (Temporal::BBT_Offset const & q)
 void
 Trigger::set_region (boost::shared_ptr<Region> r)
 {
-	TriggerBox::worker->set_region (_box, index(), r);
+	if (!r) {
+		/* clear operation, no need to talk to the worker thread */
+		_box.set_pending (_index, TriggerPtr());
+	} else {
+		/* load data, do analysis in another thread */
+		TriggerBox::worker->set_region (_box, index(), r);
+	}
 }
 
 void
@@ -1681,6 +1687,8 @@ TriggerBox::TriggerBox (Session& s, DataType dt)
 		}
 	}
 
+	pending.reserve (all_triggers.size());
+
 	Config->ParameterChanged.connect_same_thread (*this, boost::bind (&TriggerBox::parameter_changed, this, _1));
 
 	StopAllTriggers.connect_same_thread (stop_all_connection, boost::bind (&TriggerBox::request_stop_all, this));
@@ -1693,6 +1701,35 @@ TriggerBox::scene_bang (uint32_t n)
 	_pending_scene = n;
 }
 
+void
+TriggerBox::set_region (uint32_t slot, boost::shared_ptr<Region> region)
+{
+	/* This is called from our worker thread */
+
+	TriggerPtr t;
+
+	switch (_data_type) {
+	case DataType::AUDIO:
+		t = boost::make_shared<AudioTrigger> (slot, *this);
+		break;
+	case DataType::MIDI:
+		t = boost::make_shared<MIDITrigger> (slot, *this);
+		break;
+	}
+
+	t->set_region_threaded (region);
+
+	/* XXX what happens if pending is already set? */
+
+	set_pending (slot, t);
+}
+
+void
+TriggerBox::set_pending (uint32_t slot, TriggerPtr t)
+{
+	pending[slot] = t;
+}
+
 void
 TriggerBox::scene_unbang (uint32_t n)
 {
@@ -2700,7 +2737,7 @@ TriggerBoxThread::thread_work ()
 			while (requests.read (&req, 1) == 1) {
 				switch (req->type) {
 				case SetRegion:
-					req->box->trigger (req->slot)->set_region_threaded (req->region);
+					req->box->set_region (req->slot, req->region);
 					break;
 				default:
 					break;