From cdf98a1bd7cff14dcbeacf6c98a77ebd1ad94807 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Thu, 16 Jun 2022 22:09:53 -0600
Subject: [PATCH] tempo display: when the tempo map changes, avoid unnecessary
 work

If the initial tempo marker is referencing a point in the new map, assume that
all markers have already been associated with the map.
---
 gtk2_ardour/editor_tempodisplay.cc | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/gtk2_ardour/editor_tempodisplay.cc b/gtk2_ardour/editor_tempodisplay.cc
index ec96466293..7c0e806363 100644
--- a/gtk2_ardour/editor_tempodisplay.cc
+++ b/gtk2_ardour/editor_tempodisplay.cc
@@ -450,6 +450,24 @@ Editor::tempo_map_changed ()
 {
 	TempoMap::SharedPtr current_map = TempoMap::fetch ();
 	reassociate_metric_markers (current_map);
+	/* If the tempo map was changed by something other than the Editor, we
+	 * will need to reassociate all visual elements used for tempo display
+	 * with the new map.
+	 */
+
+	if (!tempo_marks.empty()) {
+		/* a little awkward using shared_ptr<T>::get() but better than every
+		 * point in the map holding a shared_ptr ref to the map that owns it.
+		 */
+
+		if (&tempo_marks.front()->point().map() != current_map.get()) {
+			std::cerr << "Map changed, need marker reassoc; point using " << &tempo_marks.front()->point().map() << " vs. " << current_map.get() << std::endl;
+			reassociate_metric_markers (current_map);
+		} else {
+			std::cerr << "Map changed, no reassoc reqd\n";
+		}
+	}
+
 	tempo_map_visual_update ();
 }