From ebf59d4426fcae0d94dabdf6559a8832db224d27 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Fri, 7 Oct 2022 00:32:14 +0200
Subject: [PATCH] Insert_or_assign properties, allow to override properties

This allows to copy a property list and then selectively
replace various properties. e.g.

```
PropertyList plist (region->properties ());
plist.add (Properties::length, len);
plist.remove (Properties::start);
```

See also 8b0ab386756007334c961953f10482ea0cb90644
and 97f0fac7d544391d9631127aeaf8fe98fa74baf1
This also fixes the issue referenced in
8c83149c4c5bd596f6bf5f437b1f2bc934a35d4d
---
 libs/pbd/pbd/property_list.h      | 1 +
 libs/pbd/pbd/property_list_impl.h | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/libs/pbd/pbd/property_list.h b/libs/pbd/pbd/property_list.h
index 1711b2dd00..330345853f 100644
--- a/libs/pbd/pbd/property_list.h
+++ b/libs/pbd/pbd/property_list.h
@@ -57,6 +57,7 @@ public:
 	 * Defined below, once we have Property<T>
 	 */
 	template<typename T, typename V> bool add (PropertyDescriptor<T> pid, const V& v);
+	template<typename T> bool remove (PropertyDescriptor<T> pid);
 
 protected:
 	bool _property_owner;
diff --git a/libs/pbd/pbd/property_list_impl.h b/libs/pbd/pbd/property_list_impl.h
index 194042cf4c..b99f07236b 100644
--- a/libs/pbd/pbd/property_list_impl.h
+++ b/libs/pbd/pbd/property_list_impl.h
@@ -28,7 +28,13 @@ namespace PBD {
 
 template<typename T, typename V> bool
 PropertyList::add (PropertyDescriptor<T> pid, const V& v) {
-        return insert (value_type (pid.property_id, new Property<T> (pid, (T)v))).second;
+	erase (pid.property_id);
+	return insert (value_type (pid.property_id, new Property<T> (pid, (T)v))).second;
+}
+
+template<typename T> bool
+PropertyList::remove (PropertyDescriptor<T> pid) {
+	return erase (pid.property_id) > 0;
 }
 
 }