From 469fcc9c5279635dcd4565b51e6927480fb6ebc0 Mon Sep 17 00:00:00 2001
From: Steve Cotton <steve@octalot.co.uk>
Date: Mon, 15 Jul 2019 16:23:52 +0200
Subject: [PATCH] Convert help_impl's ref-counting to std::shared_ptr

This is part of #4166, as topic_text wasn't consistent with
the Rule of Three.
---
 src/help/help_impl.cpp | 27 ++++++---------------------
 src/help/help_impl.hpp | 30 ++++++++++++++----------------
 2 files changed, 20 insertions(+), 37 deletions(-)

diff --git a/src/help/help_impl.cpp b/src/help/help_impl.cpp
index 8a8ca04cf9f8..1e6f3532f13e 100644
--- a/src/help/help_impl.cpp
+++ b/src/help/help_impl.cpp
@@ -325,22 +325,8 @@ std::string generate_topic_text(const std::string &generator, const config *help
 	return empty_string;
 }
 
-topic_text::~topic_text()
+topic_text& topic_text::operator=(std::shared_ptr<topic_generator> g)
 {
-	if (generator_ && --generator_->count == 0)
-		delete generator_;
-}
-
-topic_text::topic_text(const topic_text& t): parsed_text_(t.parsed_text_), generator_(t.generator_)
-{
-	if (generator_)
-		++generator_->count;
-}
-
-topic_text &topic_text::operator=(topic_generator *g)
-{
-	if (generator_ && --generator_->count == 0)
-		delete generator_;
 	generator_ = g;
 	return *this;
 }
@@ -349,9 +335,8 @@ const std::vector<std::string>& topic_text::parsed_text() const
 {
 	if (generator_) {
 		parsed_text_ = parse_text((*generator_)());
-		if (--generator_->count == 0)
-			delete generator_;
-		generator_ = nullptr;
+		// This caches the result, so doesn't need the generator any more
+		generator_.reset();
 	}
 	return parsed_text_;
 }
@@ -855,7 +840,7 @@ void generate_terrain_sections(const config* /*help_cfg*/, section& sec, int /*l
 		topic terrain_topic;
 		terrain_topic.title = info.editor_name();
 		terrain_topic.id    = hidden_symbol(hidden) + terrain_prefix + info.id();
-		terrain_topic.text  = new terrain_topic_generator(info);
+		terrain_topic.text  = std::make_shared<terrain_topic_generator>(info);
 
 		t_translation::ter_list base_terrains = tdata->underlying_union_terrain(t);
 		for (const t_translation::terrain_code& base : base_terrains) {
@@ -900,7 +885,7 @@ void generate_unit_sections(const config* /*help_cfg*/, section& sec, int level,
 			const std::string var_ref = hidden_symbol(var_type.hide_help()) + variation_prefix + var_type.id() + "_" + variation_id;
 
 			topic var_topic(topic_name, var_ref, "");
-			var_topic.text = new unit_topic_generator(var_type, variation_id);
+			var_topic.text = std::make_shared<unit_topic_generator>(var_type, variation_id);
 			base_unit.topics.push_back(var_topic);
 		}
 
@@ -938,7 +923,7 @@ std::vector<topic> generate_unit_topics(const bool sort_generated, const std::st
 		const std::string real_prefix = type.show_variations_in_help() ? ".." : "";
 		const std::string ref_id = hidden_symbol(type.hide_help()) + real_prefix + unit_prefix +  type.id();
 		topic unit_topic(type_name, ref_id, "");
-		unit_topic.text = new unit_topic_generator(type);
+		unit_topic.text = std::make_shared<unit_topic_generator>(type);
 		topics.push_back(unit_topic);
 
 		if (!type.hide_help()) {
diff --git a/src/help/help_impl.hpp b/src/help/help_impl.hpp
index 43687953efed..d12fe738bf4e 100644
--- a/src/help/help_impl.hpp
+++ b/src/help/help_impl.hpp
@@ -62,10 +62,8 @@ typedef std::vector<section *> section_list;
 /// Generate a topic text on the fly.
 class topic_generator
 {
-	unsigned count;
-	friend class topic_text;
 public:
-	topic_generator(): count(1) {}
+	topic_generator() = default;
 	virtual std::string operator()() const = 0;
 	virtual ~topic_generator() {}
 };
@@ -82,30 +80,30 @@ class text_topic_generator: public topic_generator {
 class topic_text
 {
 	mutable std::vector< std::string > parsed_text_;
-	mutable topic_generator *generator_;
+	mutable std::shared_ptr<topic_generator> generator_;
 public:
-	~topic_text();
-	topic_text():
-		parsed_text_(),
-		generator_(nullptr)
-	{
-	}
+	topic_text() = default;
+	~topic_text() = default;
 
 	topic_text(const std::string& t):
 		parsed_text_(),
-		generator_(new text_topic_generator(t))
+		generator_(std::make_shared<text_topic_generator>(t))
 	{
 	}
 
-	explicit topic_text(topic_generator *g):
+	explicit topic_text(std::shared_ptr<topic_generator> g):
 		parsed_text_(),
 		generator_(g)
 	{
 	}
-	topic_text &operator=(topic_generator *g);
-	topic_text(const topic_text& t);
 
-    const std::vector<std::string>& parsed_text() const;
+	topic_text(const topic_text& t) = default;
+	topic_text(topic_text&& t) = default;
+	topic_text& operator=(topic_text&& t) = default;
+	topic_text& operator=(const topic_text& t) = default;
+	topic_text& operator=(std::shared_ptr<topic_generator> g);
+
+	const std::vector<std::string>& parsed_text() const;
 };
 
 /// A topic contains a title, an id and some text.
@@ -127,7 +125,7 @@ struct topic
 
 	topic(const std::string &_title, const std::string &_id, const std::string &_text)
 		: title(_title), id(_id), text(_text) {}
-	topic(const std::string &_title, const std::string &_id, topic_generator *g)
+	topic(const std::string &_title, const std::string &_id, std::shared_ptr<topic_generator> g)
 		: title(_title), id(_id), text(g) {}
 	/// Two topics are equal if their IDs are equal.
 	bool operator==(const topic &) const;