make Buffer::{add,remove}_change_listener const and the listener list mutable

3 files changed, 9 insertions, 9 deletions

diff --git a/src/buffer.cc b/src/buffer.cc
index e40383cd..4b53d210 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -415,13 +415,13 @@ void Buffer::notify_saved()
     m_last_save_undo_index = history_cursor_index;
 }
 
-void Buffer::add_change_listener(BufferChangeListener& listener)
+void Buffer::add_change_listener(BufferChangeListener& listener) const
 {
     assert(not contains(m_change_listeners, &listener));
     m_change_listeners.push_back(&listener);
 }
 
-void Buffer::remove_change_listener(BufferChangeListener& listener)
+void Buffer::remove_change_listener(BufferChangeListener& listener) const
 {
     auto it = std::find(m_change_listeners.begin(),
                         m_change_listeners.end(),
diff --git a/src/buffer.hh b/src/buffer.hh
index de5e0cbf..807f8acd 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -156,8 +156,8 @@ public:
     // notify the buffer that it was saved in the current state
     void notify_saved();
 
-    void add_change_listener(BufferChangeListener& listener);
-    void remove_change_listener(BufferChangeListener& listener);
+    void add_change_listener(BufferChangeListener& listener) const;
+    void remove_change_listener(BufferChangeListener& listener) const;
 
     // returns an iterator pointing to the first character of the line
     // iterator is on
@@ -224,7 +224,9 @@ private:
     size_t m_last_save_undo_index;
     size_t m_timestamp;
 
-    std::vector<BufferChangeListener*> m_change_listeners;
+    // this mutable as adding or removing listeners is not muting the buffer
+    // observable state.
+    mutable std::vector<BufferChangeListener*> m_change_listeners;
 
     OptionManager m_option_manager;
     HookManager   m_hook_manager;
diff --git a/src/selection.cc b/src/selection.cc
index baab004d..08456860 100644
--- a/src/selection.cc
+++ b/src/selection.cc
@@ -86,14 +86,12 @@ void Selection::on_erase(const BufferIterator& begin, const BufferIterator& end)
 
 void Selection::register_with_buffer()
 {
-    Buffer& buffer = const_cast<Buffer&>(m_first.buffer());
-    buffer.add_change_listener(*this);
+    m_first.buffer().add_change_listener(*this);
 }
 
 void Selection::unregister_with_buffer()
 {
-    Buffer& buffer = const_cast<Buffer&>(m_first.buffer());
-    buffer.remove_change_listener(*this);
+    m_first.buffer().remove_change_listener(*this);
 }
 
 void Selection::check_invariant() const