From e682e1fde4e86b8691bc523b5669314597f00e1e Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Fri, 8 Aug 2025 14:20:04 -0600
Subject: [PATCH] refinements to infrastructure for an EditingContext's locally
 scoped tempo map

---
 gtk2_ardour/editing_context.cc | 14 ++++++++++----
 gtk2_ardour/editing_context.h  | 23 +++++++++++++++++------
 2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/gtk2_ardour/editing_context.cc b/gtk2_ardour/editing_context.cc
index 3b23559397..925ec6d29c 100644
--- a/gtk2_ardour/editing_context.cc
+++ b/gtk2_ardour/editing_context.cc
@@ -1629,11 +1629,17 @@ EditingContext::snap_relative_time_to_relative_time (timepos_t const & origin, t
 	return origin.distance (snapped);
 }
 
-std::shared_ptr<Temporal::TempoMap const>
-EditingContext::start_local_tempo_map (std::shared_ptr<Temporal::TempoMap>)
+void
+EditingContext::start_local_tempo_map (std::shared_ptr<TempoMap> map)
 {
-	/* default is a no-op */
-	return Temporal::TempoMap::use ();
+	_local_tempo_map = map;
+}
+
+void
+EditingContext::end_local_tempo_map ()
+{
+	_local_tempo_map.reset ();
+	Temporal::TempoMap::fetch ();
 }
 
 bool
diff --git a/gtk2_ardour/editing_context.h b/gtk2_ardour/editing_context.h
index 08caf25ff1..a59bfeb677 100644
--- a/gtk2_ardour/editing_context.h
+++ b/gtk2_ardour/editing_context.h
@@ -87,18 +87,17 @@ class EditingContext : public ARDOUR::SessionHandlePtr, public AxisViewProvider,
 
 	Temporal::TimeDomain time_domain () const;
 
-
 	struct TempoMapScope {
 		TempoMapScope (EditingContext& context, std::shared_ptr<Temporal::TempoMap> map)
 			: ec (context)
 		{
-			old_map = ec.start_local_tempo_map (map);
+			ec.start_local_tempo_map (map);
+			ec.ensure_local_tempo_scope ();
 		}
 		~TempoMapScope () {
-			ec.end_local_tempo_map (old_map);
+			ec.end_local_tempo_map ();
 		}
 		EditingContext& ec;
-		std::shared_ptr<Temporal::TempoMap const> old_map;
 	};
 
 	DragManager* drags () const {
@@ -666,8 +665,9 @@ class EditingContext : public ARDOUR::SessionHandlePtr, public AxisViewProvider,
 	QuantizeDialog* quantize_dialog;
 
 	friend struct TempoMapScope;
-	virtual std::shared_ptr<Temporal::TempoMap const> start_local_tempo_map (std::shared_ptr<Temporal::TempoMap>);
-	virtual void end_local_tempo_map (std::shared_ptr<Temporal::TempoMap const>) { /* no-op by default */ }
+	void set_local_tempo_map (std::shared_ptr<Temporal::TempoMap>);
+	void start_local_tempo_map (std::shared_ptr<Temporal::TempoMap>);
+	void end_local_tempo_map ();
 
 	virtual bool button_press_handler (ArdourCanvas::Item*, GdkEvent*, ItemType) = 0;
 	virtual bool button_press_handler_1 (ArdourCanvas::Item*, GdkEvent*, ItemType) = 0;
@@ -832,4 +832,15 @@ class EditingContext : public ARDOUR::SessionHandlePtr, public AxisViewProvider,
 
 	bool temporary_zoom_focus_change;
 	bool _dragging_playhead;
+
+	std::shared_ptr<Temporal::TempoMap> _local_tempo_map;
+	void ensure_local_tempo_scope () {
+		if (_local_tempo_map) {
+			Temporal::TempoMap::set (_local_tempo_map);
+			_local_tempo_map.reset ();
+		}
+	}
 };
+
+#define EC_LOCAL_TEMPO_SCOPE ensure_local_tempo_scope ()
+#define EC_GIVEN_LOCAL_TEMPO_SCOPE(ec) ec.ensure_local_tempo_scope ()