From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Tue, 12 Mar 2019 11:40:32 +0000 (+0100)
Subject: Make TextMetrics noncopyable
X-Git-Url: https://git.lyx.org/gitweb/?a=commitdiff_plain;h=6d67dfa2b42845206d8b40e9416f047e372cfa23;p=features.git

Make TextMetrics noncopyable

This is done by declaring unimplemented private copy constructor and
assignment operator.

This breaks compilation in BufferView::textMetrics, which does a copy when
inserting a TextMetrics object in the cache. Some C++11 wizardry I will not
pretend to completely understand saves the day.

See the following page for details:
  https://en.cppreference.com/w/cpp/container/map/emplace

This avoids real world bugs like #11512.
---

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index 50df1aade2..900207c238 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -2542,8 +2542,9 @@ TextMetrics & BufferView::textMetrics(Text const * t)
 	LBUFERR(t);
 	TextMetricsCache::iterator tmc_it  = d->text_metrics_.find(t);
 	if (tmc_it == d->text_metrics_.end()) {
-		tmc_it = d->text_metrics_.insert(
-			make_pair(t, TextMetrics(this, const_cast<Text *>(t)))).first;
+		tmc_it = d->text_metrics_.emplace(std::piecewise_construct,
+		         	std::forward_as_tuple(t),
+		         	std::forward_as_tuple(this, const_cast<Text *>(t))).first;
 	}
 	return tmc_it->second;
 }
diff --git a/src/TextMetrics.h b/src/TextMetrics.h
index 26156fa100..006836fb0a 100644
--- a/src/TextMetrics.h
+++ b/src/TextMetrics.h
@@ -33,6 +33,9 @@ class Text;
 /// A map from a Text to the map of paragraphs metrics
 class TextMetrics
 {
+	/// noncopyable
+	TextMetrics(TextMetrics const &);
+	void operator=(TextMetrics const &);
 public:
 	/// Default constructor (only here for STL containers).
 	TextMetrics() : bv_(0), text_(0), max_width_(0) {}