FlagLines: use a shared updaters for options

previously, having two windows showing the same buffer with
the same line flags would have updated the options twice, resulting
in wrong lines in option. Now line flags options are updated only
once by a shared object along all FlagLines highlighter using the
same option.

src/highlighters.cc

@@ -332,22 +332,22 @@ void expand_unprintable(DisplayBuffer& display_buffer)
     }
 }
 
-class FlagLines : public BufferChangeListener_AutoRegister,
+class FlagLines : public OptionManagerWatcher_AutoRegister
-                  public OptionManagerWatcher_AutoRegister
 {
 public:
     FlagLines(Color bg, String option_name, Window& window)
-        : BufferChangeListener_AutoRegister(window.buffer()),
+        : OptionManagerWatcher_AutoRegister(window.options()),
-          OptionManagerWatcher_AutoRegister(window.options()),
           m_bg(bg), m_option_name(std::move(option_name)),
           m_window(window)
     {
         // trigger an exception if option is not of right type.
         m_window.options()[m_option_name].get<std::vector<LineAndFlag>>();
+        update_shared_option_updater();
     }
 
     void operator()(DisplayBuffer& display_buffer)
     {
+        update_shared_option_updater();
         auto& lines = m_window.options()[m_option_name].get<std::vector<LineAndFlag>>();
 
         CharCount width = 0;
@@ -366,28 +366,36 @@ public:
         }
     }
 
-    void on_option_changed(const Option& option)
+private:
+    void on_option_changed(const Option& option) override
     {
         if (option.name() == m_option_name)
             m_window.forget_timestamp();
     }
 
+    struct OptionUpdater : BufferChangeListener_AutoRegister
+    {
+        OptionUpdater(Buffer& buffer, Option& option)
+            : BufferChangeListener_AutoRegister(buffer), m_option(&option)
+        {
+            // sanity checks
+            kak_assert(&m_option->manager() != &GlobalOptions::instance());
+            m_option->get<std::vector<LineAndFlag>>();
+        }
+
         void on_insert(const BufferIterator& begin, const BufferIterator& end) override
         {
             LineCount new_lines = end.line() - begin.line();
             if (new_lines == 0)
                 return;
 
-        const Option& opt = m_window.options()[m_option_name];
+            auto lines = m_option->get<std::vector<LineAndFlag>>();
-        if (&opt.manager() == &GlobalOptions::instance())
-            return;
-        auto lines = opt.get<std::vector<LineAndFlag>>();
             for (auto& line : lines)
             {
                 if (std::get<0>(line) > begin.line())
                     std::get<0>(line) += new_lines;
             }
-        opt.manager().get_local_option(m_option_name).set(lines);
+            m_option->set(lines);
         }
 
         void on_erase(const BufferIterator& begin, const BufferIterator& end)  override
@@ -396,24 +404,44 @@ public:
             if (removed_lines == 0)
                 return;
 
-        const Option& opt = m_window.options()[m_option_name];
+            auto lines = m_option->get<std::vector<LineAndFlag>>();
-        // only update
-        if (&opt.manager() == &GlobalOptions::instance())
-            return;
-        auto lines = opt.get<std::vector<LineAndFlag>>();
             for (auto& line : lines)
             {
                 if (std::get<0>(line) > begin.line())
                     std::get<0>(line) -= removed_lines;
             }
-        opt.manager().get_local_option(m_option_name).set(lines);
+            m_option->set(lines);
         }
 
+        const Option& option() const { return *m_option; }
     private:
+        safe_ptr<Option> m_option;
+    };
+    static std::unordered_map<const Option*, std::weak_ptr<OptionUpdater>> ms_updaters;
+
+    void update_shared_option_updater()
+    {
+        const Option& option = m_window.options()[m_option_name];
+        if (&option.manager() == &GlobalOptions::instance() or
+            (m_updater and &option == &m_updater->option()))
+            return;
+        auto& shared_updater = ms_updaters[&option];
+        if (shared_updater.expired())
+        {
+            m_updater = std::make_shared<OptionUpdater>(
+                m_window.buffer(), option.manager().get_local_option(option.name()));
+            shared_updater = m_updater;
+        }
+        else
+           m_updater = shared_updater.lock();
+    }
+
     Color m_bg;
     String m_option_name;
     Window& m_window;
+    std::shared_ptr<OptionUpdater> m_updater;
 };
+std::unordered_map<const Option*, std::weak_ptr<FlagLines::OptionUpdater>> FlagLines::ms_updaters;
 
 HighlighterAndId flag_lines_factory(const HighlighterParameters& params, Window& window)
 {

src/option_manager.hh

@@ -19,7 +19,7 @@ struct option_not_found : public runtime_error
 
 class OptionManager;
 
-class Option
+class Option : public SafeCountable
 {
 public:
     Option(OptionManager& manager, String name);