From 05d3a649521e0e8524209ae9deae75c30ff01e93 Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Sat, 21 Jul 2018 23:58:47 +0200
Subject: [PATCH] Use swap in InsetText::updateBuffer for notes ad friends

Avoid as much as possible to do full copies of all counters, since
that can be exensive. Unfortunately, it is just posible when we want
to restore the saved counters.

Explanations why we use friend swap is here:
https://stackoverflow.com/questions/5695548/public-friend-swap-member-function

Part of bug #5973.
---
 src/Counters.cpp         | 8 ++++++++
 src/Counters.h           | 3 +++
 src/insets/InsetText.cpp | 4 ++--
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/Counters.cpp b/src/Counters.cpp
index 2daac53224..3bb4d07758 100644
--- a/src/Counters.cpp
+++ b/src/Counters.cpp
@@ -697,4 +697,12 @@ void Counters::endEnvironment()
 }
 
 
+void swap(Counters & c1, Counters & c2)
+{
+	Counters tmp = move(c1);
+	c1 = move(c2);
+	c2 = move(tmp);
+}
+
+
 } // namespace lyx
diff --git a/src/Counters.h b/src/Counters.h
index 536dcc17a6..f8bb0fa6aa 100644
--- a/src/Counters.h
+++ b/src/Counters.h
@@ -239,6 +239,9 @@ private:
 	std::vector<docstring> counter_stack_;
 	/// Same, but for last layout.
 	std::vector<Layout const *> layout_stack_;
+
+	///
+	friend void swap(Counters &, Counters &);
 };
 
 } // namespace lyx
diff --git a/src/insets/InsetText.cpp b/src/insets/InsetText.cpp
index 74f60e422e..d00935784d 100644
--- a/src/insets/InsetText.cpp
+++ b/src/insets/InsetText.cpp
@@ -814,13 +814,13 @@ void InsetText::updateBuffer(ParIterator const & it, UpdateType utype)
 		// Note that we do not need to call:
 		//	tclass.counters().clearLastLayout()
 		// since we are saving and restoring the existing counters, etc.
-		Counters const savecnt = tclass.counters();
+		Counters savecnt = tclass.counters();
 		tclass.counters().reset();
 		// we need float information even in note insets (#9760)
 		tclass.counters().current_float(savecnt.current_float());
 		tclass.counters().isSubfloat(savecnt.isSubfloat());
 		buffer().updateBuffer(it2, utype);
-		tclass.counters() = savecnt;
+		swap(tclass.counters(), savecnt);
 	}
 }
 
-- 
2.39.2