diff --git a/src/buffer.cc b/src/buffer.cc
index 398f7460..52621f3d 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -66,10 +66,10 @@ BufferCoord Buffer::line_and_column_at(const BufferIterator& iterator) const
     return iterator.m_coord;
 }
 
-BufferSize Buffer::line_length(LineCount line) const
+CharCount Buffer::line_length(LineCount line) const
 {
     assert(line < line_count());
-    BufferPos end = (line < line_count() - 1) ?
+    CharCount end = (line < line_count() - 1) ?
                     m_lines[line + 1].start : character_count();
     return end - m_lines[line].start;
 }
@@ -82,8 +82,8 @@ BufferCoord Buffer::clamp(const BufferCoord& line_and_column,
 
     BufferCoord result(line_and_column.line, line_and_column.column);
     result.line = Kakoune::clamp(0_line, line_count() - 1, result.line);
-    int max_col = std::max(0, line_length(result.line) - (avoid_eol ? 2 : 1));
-    result.column = Kakoune::clamp<int>(0, max_col, result.column);
+    CharCount max_col = std::max(0_char, line_length(result.line) - (avoid_eol ? 2 : 1));
+    result.column = Kakoune::clamp(0_char, max_col, result.column);
     return result;
 }
 
@@ -120,10 +120,10 @@ BufferIterator Buffer::end() const
 {
     if (m_lines.empty())
         return BufferIterator(*this, { 0_line, 0 });
-    return BufferIterator(*this, { line_count()-1, (int)m_lines.back().length() });
+    return BufferIterator(*this, { line_count()-1, m_lines.back().length() });
 }
 
-BufferSize Buffer::character_count() const
+CharCount Buffer::character_count() const
 {
     if (m_lines.empty())
         return 0;
@@ -140,10 +140,10 @@ String Buffer::string(const BufferIterator& begin, const BufferIterator& end) co
     String res;
     for (LineCount line = begin.line(); line <= end.line(); ++line)
     {
-       size_t start = 0;
+       CharCount start = 0;
        if (line == begin.line())
            start = begin.column();
-       size_t count = -1;
+       CharCount count = -1;
        if (line == end.line())
            count = end.column() - start;
        res += m_lines[line].content.substr(start, count);
@@ -231,7 +231,7 @@ void Buffer::reset_undo_data()
 
 void Buffer::check_invariant() const
 {
-    BufferSize start = 0;
+    CharCount start = 0;
     assert(not m_lines.empty());
     for (auto& line : m_lines)
     {
@@ -245,7 +245,7 @@ void Buffer::check_invariant() const
 void Buffer::do_insert(const BufferIterator& pos, const String& content)
 {
     ++m_timestamp;
-    BufferSize offset = pos.offset();
+    CharCount offset = pos.offset();
 
     // all following lines advanced by length
     for (LineCount i = pos.line()+1; i < line_count(); ++i)
@@ -257,8 +257,8 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
     // line without inserting a '\n'
     if (pos == end() and (pos == begin() or *(pos-1) == '\n'))
     {
-        int start = 0;
-        for (int i = 0; i < content.length(); ++i)
+        CharCount start = 0;
+        for (CharCount i = 0; i < content.length(); ++i)
         {
             if (content[i] == '\n')
             {
@@ -280,8 +280,8 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
         auto line_it = m_lines.begin() + (int)pos.line();
         line_it = m_lines.erase(line_it);
 
-        int start = 0;
-        for (int i = 0; i < content.length(); ++i)
+        CharCount start = 0;
+        for (CharCount i = 0; i < content.length(); ++i)
         {
             if (content[i] == '\n')
             {
@@ -289,7 +289,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
                 if (start == 0)
                 {
                     line_content = prefix + line_content;
-                    line_it = m_lines.insert(line_it, { offset + start - (int)prefix.length(),
+                    line_it = m_lines.insert(line_it, { offset + start - prefix.length(),
                                                         std::move(line_content) });
                 }
                 else
@@ -301,7 +301,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
             }
         }
         if (start == 0)
-            line_it = m_lines.insert(line_it, { offset + start - (int)prefix.length(), prefix + content + suffix });
+            line_it = m_lines.insert(line_it, { offset + start - prefix.length(), prefix + content + suffix });
         else if (start != content.length() or not suffix.empty())
             line_it = m_lines.insert(line_it, { offset + start, content.substr(start) + suffix });
         else
@@ -309,7 +309,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
 
         begin_it = pos;
         end_it = BufferIterator(*this, { LineCount(line_it - m_lines.begin()),
-                                         int(line_it->length() - suffix.length()) });
+                                         line_it->length() - suffix.length() });
     }
 
     check_invariant();
@@ -318,7 +318,7 @@ void Buffer::do_insert(const BufferIterator& pos, const String& content)
         listener->on_insert(begin_it, end_it);
 }
 
-void Buffer::do_erase(const BufferIterator& pos, BufferSize length)
+void Buffer::do_erase(const BufferIterator& pos, CharCount length)
 {
     ++m_timestamp;
     BufferIterator end = pos + length;
@@ -328,7 +328,7 @@ void Buffer::do_erase(const BufferIterator& pos, BufferSize length)
     Line new_line = { m_lines[pos.line()].start, prefix + suffix };
 
     m_lines.erase(m_lines.begin() + (int)pos.line(), m_lines.begin() + (int)end.line() + 1);
-    if (new_line.length())
+    if (new_line.length() != 0)
         m_lines.insert(m_lines.begin() + (int)pos.line(), std::move(new_line));
 
     for (LineCount i = pos.line()+1; i < line_count(); ++i)
@@ -356,7 +356,7 @@ void Buffer::apply_modification(const Modification& modification)
     }
     case Modification::Erase:
     {
-        size_t count = modification.content.length();
+        CharCount count = modification.content.length();
         assert(string(modification.position, modification.position + count)
                == modification.content);
         do_erase(modification.position, count);
diff --git a/src/buffer.hh b/src/buffer.hh
index 971c731f..7f3f95ac 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -17,12 +17,9 @@ namespace Kakoune
 class Buffer;
 class Window;
 
-typedef int       BufferPos;
-typedef int       BufferSize;
-
 struct BufferCoord : LineAndColumn<BufferCoord>
 {
-    BufferCoord(LineCount line = 0, int column = 0)
+    BufferCoord(LineCount line = 0, CharCount column = 0)
         : LineAndColumn(line, column) {}
 
     template<typename T>
@@ -35,7 +32,7 @@ class BufferIterator
 {
 public:
     typedef Character  value_type;
-    typedef BufferSize difference_type;
+    typedef size_t difference_type;
     typedef const value_type* pointer;
     typedef const value_type& reference;
     typedef std::bidirectional_iterator_tag iterator_category;
@@ -51,13 +48,13 @@ public:
     bool operator>= (const BufferIterator& iterator) const;
 
     Character  operator* () const;
-    BufferSize operator- (const BufferIterator& iterator) const;
+    size_t operator- (const BufferIterator& iterator) const;
 
-    BufferIterator operator+ (BufferSize size) const;
-    BufferIterator operator- (BufferSize size) const;
+    BufferIterator operator+ (CharCount size) const;
+    BufferIterator operator- (CharCount size) const;
 
-    BufferIterator& operator+= (BufferSize size);
-    BufferIterator& operator-= (BufferSize size);
+    BufferIterator& operator+= (CharCount size);
+    BufferIterator& operator-= (CharCount size);
 
     BufferIterator& operator++ ();
     BufferIterator& operator-- ();
@@ -74,10 +71,10 @@ public:
     const Buffer& buffer() const;
     const BufferCoord& coord() const { return m_coord; }
     LineCount  line() const { return m_coord.line; }
-    BufferSize column() const { return m_coord.column; }
+    CharCount column() const { return m_coord.column; }
 
 private:
-    BufferSize offset() const;
+    CharCount offset() const;
 
     const Buffer* m_buffer;
     BufferCoord   m_coord;
@@ -130,7 +127,7 @@ public:
 
     BufferIterator begin() const;
     BufferIterator end() const;
-    BufferSize     character_count() const;
+    CharCount      character_count() const;
     LineCount      line_count() const;
 
     // returns an iterator at given coordinates. line_and_column is
@@ -187,10 +184,10 @@ private:
 
     struct Line
     {
-        BufferPos start;
+        CharCount start;
         String    content;
 
-        size_t length() const { return content.length(); }
+        CharCount length() const { return content.length(); }
     };
     struct LineList : std::vector<Line>
     {
@@ -204,9 +201,9 @@ private:
     LineList m_lines;
 
     void do_insert(const BufferIterator& pos, const String& content);
-    void do_erase(const BufferIterator& pos, BufferSize length);
+    void do_erase(const BufferIterator& pos, CharCount length);
 
-    BufferSize line_length(LineCount line) const;
+    CharCount line_length(LineCount line) const;
 
     String  m_name;
     const Type   m_type;
diff --git a/src/buffer_iterator.inl.hh b/src/buffer_iterator.inl.hh
index b91734dc..1b346527 100644
--- a/src/buffer_iterator.inl.hh
+++ b/src/buffer_iterator.inl.hh
@@ -114,25 +114,25 @@ inline Character BufferIterator::operator*() const
     return m_buffer->m_lines[line()].content[column()];
 }
 
-inline BufferSize BufferIterator::offset() const
+inline CharCount BufferIterator::offset() const
 {
     assert(m_buffer);
     return line() == 0 ? column()
-                            : m_buffer->m_lines[line()].start + column();
+                       : m_buffer->m_lines[line()].start + column();
 }
 
-inline BufferSize BufferIterator::operator-(const BufferIterator& iterator) const
+inline size_t BufferIterator::operator-(const BufferIterator& iterator) const
 {
     assert(m_buffer == iterator.m_buffer);
-    return offset() - iterator.offset();
+    return (size_t)(int)(offset() - iterator.offset());
 }
 
-inline BufferIterator BufferIterator::operator+(BufferSize size) const
+inline BufferIterator BufferIterator::operator+(CharCount size) const
 {
     assert(m_buffer);
     if (size >= 0)
     {
-        BufferSize o = std::min(m_buffer->character_count(), offset() + size);
+        CharCount o = std::min(m_buffer->character_count(), offset() + size);
         for (LineCount i = line() + 1; i < m_buffer->line_count(); ++i)
         {
             if (m_buffer->m_lines[i].start > o)
@@ -144,12 +144,12 @@ inline BufferIterator BufferIterator::operator+(BufferSize size) const
     return operator-(-size);
 }
 
-inline BufferIterator BufferIterator::operator-(BufferSize size) const
+inline BufferIterator BufferIterator::operator-(CharCount size) const
 {
     assert(m_buffer);
     if (size >= 0)
     {
-        BufferSize o = std::max(0, offset() - size);
+        CharCount o = std::max(0_char, offset() - size);
         for (LineCount i = line(); i >= 0; --i)
         {
             if (m_buffer->m_lines[i].start <= o)
@@ -160,12 +160,12 @@ inline BufferIterator BufferIterator::operator-(BufferSize size) const
     return operator+(-size);
 }
 
-inline BufferIterator& BufferIterator::operator+=(BufferSize size)
+inline BufferIterator& BufferIterator::operator+=(CharCount size)
 {
     return *this = (*this + size);
 }
 
-inline BufferIterator& BufferIterator::operator-=(BufferSize size)
+inline BufferIterator& BufferIterator::operator-=(CharCount size)
 {
     return *this = (*this - size);
 }
diff --git a/src/buffer_manager.cc b/src/buffer_manager.cc
index c5235cb1..5a1f63da 100644
--- a/src/buffer_manager.cc
+++ b/src/buffer_manager.cc
@@ -53,7 +53,7 @@ Buffer* BufferManager::get_buffer(const String& name)
 }
 
 CandidateList BufferManager::complete_buffername(const String& prefix,
-                                                 size_t cursor_pos)
+                                                 CharCount cursor_pos)
 {
     String real_prefix = prefix.substr(0, cursor_pos);
     CandidateList result;
diff --git a/src/buffer_manager.hh b/src/buffer_manager.hh
index 36373a69..fd6ca23f 100644
--- a/src/buffer_manager.hh
+++ b/src/buffer_manager.hh
@@ -29,7 +29,7 @@ public:
     Buffer* get_buffer(const String& name);
 
     CandidateList complete_buffername(const String& prefix,
-                                      size_t cursor_pos = String::npos);
+                                      CharCount cursor_pos = -1);
 
 private:
     BufferList m_buffers;
diff --git a/src/command_manager.cc b/src/command_manager.cc
index 4e982663..947031c4 100644
--- a/src/command_manager.cc
+++ b/src/command_manager.cc
@@ -61,7 +61,7 @@ private:
 
 
 using TokenList = std::vector<Token>;
-using TokenPosList = std::vector<std::pair<size_t, size_t>>;
+using TokenPosList = std::vector<std::pair<CharCount, CharCount>>;
 
 bool is_command_separator(Character c)
 {
@@ -78,8 +78,8 @@ TokenList parse(const String& line,
 {
     TokenList result;
 
-    size_t length = line.length();
-    size_t pos = 0;
+    CharCount length = line.length();
+    CharCount pos = 0;
     while (pos < length)
     {
         while (pos != length)
@@ -92,7 +92,7 @@ TokenList parse(const String& line,
                 break;
         }
 
-        size_t token_start = pos;
+        CharCount token_start = pos;
 
         Token::Type type = Token::Type::Raw;
         if (line[pos] == '"' or line[pos] == '\'')
@@ -107,7 +107,7 @@ TokenList parse(const String& line,
         }
         else if (line[pos] == '%')
         {
-            size_t type_start = ++pos;
+            CharCount type_start = ++pos;
             while (isalpha(line[pos]))
                 ++pos;
             String type_name = line.substr(type_start, pos - type_start);
@@ -250,7 +250,7 @@ void CommandManager::execute(const String& command_line,
 }
 
 Completions CommandManager::complete(const Context& context,
-                                     const String& command_line, size_t cursor_pos)
+                                     const String& command_line, CharCount cursor_pos)
 {
     TokenPosList pos_info;
     TokenList tokens = parse(command_line, &pos_info);
@@ -267,7 +267,7 @@ Completions CommandManager::complete(const Context& context,
 
     if (token_to_complete == 0 or tokens.empty()) // command name completion
     {
-        size_t cmd_start = tokens.empty() ? 0 : pos_info[0].first;
+        CharCount cmd_start = tokens.empty() ? 0 : pos_info[0].first;
         Completions result(cmd_start, cursor_pos);
         String prefix = command_line.substr(cmd_start,
                                             cursor_pos - cmd_start);
@@ -292,10 +292,10 @@ Completions CommandManager::complete(const Context& context,
     if (command_it == m_commands.end() or not command_it->second.completer)
         return Completions();
 
-    size_t start = token_to_complete < tokens.size() ?
+    CharCount start = token_to_complete < tokens.size() ?
                    pos_info[token_to_complete].first : cursor_pos;
     Completions result(start , cursor_pos);
-    size_t cursor_pos_in_token = cursor_pos - start;
+    CharCount cursor_pos_in_token = cursor_pos - start;
 
     std::vector<String> params;
     for (auto token_it = tokens.begin()+1; token_it != tokens.end(); ++token_it)
@@ -309,7 +309,7 @@ Completions CommandManager::complete(const Context& context,
 CandidateList PerArgumentCommandCompleter::operator()(const Context& context,
                                                       const CommandParameters& params,
                                                       size_t token_to_complete,
-                                                      size_t pos_in_token) const
+                                                      CharCount pos_in_token) const
 {
     if (token_to_complete >= m_completers.size())
         return CandidateList();
diff --git a/src/command_manager.hh b/src/command_manager.hh
index 113bac3e..cbc6a2c7 100644
--- a/src/command_manager.hh
+++ b/src/command_manager.hh
@@ -28,13 +28,13 @@ typedef std::function<void (const CommandParameters&,
 
 typedef std::function<CandidateList (const Context& context,
                                      const CommandParameters&,
-                                     size_t, size_t)> CommandCompleter;
+                                     size_t, CharCount)> CommandCompleter;
 
 class PerArgumentCommandCompleter
 {
 public:
     typedef std::function<CandidateList (const Context&,
-                                         const String&, size_t)> ArgumentCompleter;
+                                         const String&, CharCount)> ArgumentCompleter;
     typedef memoryview<ArgumentCompleter> ArgumentCompleterList;
 
     PerArgumentCommandCompleter(const ArgumentCompleterList& completers)
@@ -43,7 +43,7 @@ public:
     CandidateList operator()(const Context& context,
                              const CommandParameters& params,
                              size_t token_to_complete,
-                             size_t pos_in_token) const;
+                             CharCount pos_in_token) const;
 
 private:
     std::vector<ArgumentCompleter> m_completers;
@@ -56,7 +56,7 @@ public:
                  const EnvVarMap& env_vars = EnvVarMap());
 
     Completions complete(const Context& context,
-                         const String& command_line, size_t cursor_pos);
+                         const String& command_line, CharCount cursor_pos);
 
     bool command_defined(const String& command_name) const;
 
diff --git a/src/commands.cc b/src/commands.cc
index 0b73b164..6c04fbc0 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -259,7 +259,7 @@ void edit(const CommandParameters& params, Context& context)
         int column = param_count > 2 ?
                          std::max(0, str_to_int(parser[2]) - 1) : 0;
 
-        window.select(window.buffer().iterator_at({LineCount(line), column}));
+        window.select(window.buffer().iterator_at({ line,  column }));
         window.center_selection();
     }
 
@@ -536,11 +536,11 @@ void define_command(const CommandParameters& params, Context& context)
     {
         String shell_cmd = parser.option_value("shell-completion");
         auto completer = [=](const Context& context, const CommandParameters& params,
-                             size_t token_to_complete, size_t pos_in_token)
+                             size_t token_to_complete, CharCount pos_in_token)
         {
            EnvVarMap vars = params_to_env_var_map(params);
            vars["token_to_complete"] = int_to_str(token_to_complete);
-           vars["pos_in_token"]      = int_to_str(pos_in_token);
+           vars["pos_in_token"]      = int_to_str((int)pos_in_token);
            String output = ShellManager::instance().eval(shell_cmd, context, vars);
            return split(output, '\n');
         };
@@ -577,14 +577,14 @@ void exec_commands_in_runtime_file(const CommandParameters& params,
     const String& filename = params[0];
     char buffer[2048];
 #if defined(__linux__)
-    ssize_t res = readlink("/proc/self/exe", buffer, 2048 - filename.length());
+    ssize_t res = readlink("/proc/self/exe", buffer, 2048 - (int)filename.length());
     assert(res != -1);
     buffer[res] = '\0';
 #elif defined(__APPLE__)
     uint32_t bufsize = 2048 - filename.length();
     _NSGetExecutablePath(buffer, &bufsize);
     char* canonical_path = realpath(buffer, NULL);
-    strncpy(buffer, canonical_path, 2048 - filename.length());
+    strncpy(buffer, canonical_path, 2048 - (int)filename.length());
     free(canonical_path);
 #else
 # error "finding executable path is not implemented on this platform"
@@ -778,7 +778,7 @@ void register_commands()
     cm.register_command("wq!", write_and_quit<true>);
 
     PerArgumentCommandCompleter buffer_completer({
-        [](const Context& context, const String& prefix, size_t cursor_pos)
+        [](const Context& context, const String& prefix, CharCount cursor_pos)
         { return BufferManager::instance().complete_buffername(prefix, cursor_pos); }
     });
     cm.register_commands({ "b", "buffer" }, show_buffer, buffer_completer);
@@ -786,7 +786,7 @@ void register_commands()
 
     cm.register_commands({ "ah", "addhl" }, add_highlighter,
                          [](const Context& context, const CommandParameters& params,
-                           size_t token_to_complete, size_t pos_in_token)
+                           size_t token_to_complete, CharCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -800,7 +800,7 @@ void register_commands()
                          });
     cm.register_commands({ "rh", "rmhl" }, rm_highlighter,
                          [](const Context& context, const CommandParameters& params,
-                            size_t token_to_complete, size_t pos_in_token)
+                            size_t token_to_complete, CharCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -814,7 +814,7 @@ void register_commands()
                          });
     cm.register_commands({ "af", "addfilter" }, add_filter,
                          [](const Context& context, const CommandParameters& params,
-                            size_t token_to_complete, size_t pos_in_token)
+                            size_t token_to_complete, CharCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -828,7 +828,7 @@ void register_commands()
                          });
     cm.register_commands({ "rf", "rmfilter" }, rm_filter,
                          [](const Context& context, const CommandParameters& params,
-                            size_t token_to_complete, size_t pos_in_token)
+                            size_t token_to_complete, CharCount pos_in_token)
                          {
                              Window& w = context.window();
                              const String& arg = token_to_complete < params.size() ?
@@ -857,21 +857,21 @@ void register_commands()
                          [](const CommandParameters& params, Context& context)
                          { set_option(GlobalOptionManager::instance(), params, context); },
                          PerArgumentCommandCompleter({
-                             [](const Context& context, const String& prefix, size_t cursor_pos)
+                             [](const Context& context, const String& prefix, CharCount cursor_pos)
                              { return GlobalOptionManager::instance().complete_option_name(prefix, cursor_pos); }
                          }));
     cm.register_commands({ "setb", "setbuffer" },
                          [](const CommandParameters& params, Context& context)
                          { set_option(context.buffer().option_manager(), params, context); },
                          PerArgumentCommandCompleter({
-                             [](const Context& context, const String& prefix, size_t cursor_pos)
+                             [](const Context& context, const String& prefix, CharCount cursor_pos)
                              { return context.buffer().option_manager().complete_option_name(prefix, cursor_pos); }
                          }));
     cm.register_commands({ "setw", "setwindow" },
                          [](const CommandParameters& params, Context& context)
                          { set_option(context.window().option_manager(), params, context); },
                          PerArgumentCommandCompleter({
-                             [](const Context& context, const String& prefix, size_t cursor_pos)
+                             [](const Context& context, const String& prefix, CharCount cursor_pos)
                              { return context.window().option_manager().complete_option_name(prefix, cursor_pos); }
                          }));
 }
diff --git a/src/completion.cc b/src/completion.cc
index 1d2a5e86..319da0f7 100644
--- a/src/completion.cc
+++ b/src/completion.cc
@@ -11,15 +11,15 @@ namespace Kakoune
 
 CandidateList complete_filename(const Context& context,
                                 const String& prefix,
-                                size_t cursor_pos)
+                                CharCount cursor_pos)
 {
     String real_prefix = prefix.substr(0, cursor_pos);
     String dirname = "./";
     String dirprefix;
     String fileprefix = real_prefix;
 
-    size_t dir_end = -1;
-    for (size_t i = 0; i < real_prefix.length(); ++i)
+    CharCount dir_end = -1;
+    for (CharCount i = 0; i < real_prefix.length(); ++i)
     {
         if (real_prefix[i] == '/')
             dir_end = i;
@@ -49,7 +49,7 @@ CandidateList complete_filename(const Context& context,
             String name = dirprefix + filename;
             if (entry->d_type == DT_DIR)
                 name += '/';
-            if (fileprefix.length() or filename[0] != '.')
+            if (fileprefix.length() != 0 and filename[0] != '.')
                 result.push_back(name);
         }
     }
diff --git a/src/completion.hh b/src/completion.hh
index 775d558e..60462975 100644
--- a/src/completion.hh
+++ b/src/completion.hh
@@ -16,25 +16,25 @@ typedef std::vector<String> CandidateList;
 struct Completions
 {
     CandidateList candidates;
-    size_t start;
-    size_t end;
+    CharCount start;
+    CharCount end;
 
     Completions()
         : start(0), end(0) {}
 
-    Completions(size_t start, size_t end)
+    Completions(CharCount start, CharCount end)
         : start(start), end(end) {}
 };
 
 CandidateList complete_filename(const Context& context,
                                 const String& prefix,
-                                size_t cursor_pos = -1);
+                                CharCount cursor_pos = -1);
 
 typedef std::function<Completions (const Context&,
-                                   const String&, size_t)> Completer;
+                                   const String&, CharCount)> Completer;
 
 inline Completions complete_nothing(const Context& context,
-                                    const String&, size_t cursor_pos)
+                                    const String&, CharCount cursor_pos)
 {
     return Completions(cursor_pos, cursor_pos);
 }
diff --git a/src/display_buffer.hh b/src/display_buffer.hh
index f48807c4..110b6be2 100644
--- a/src/display_buffer.hh
+++ b/src/display_buffer.hh
@@ -12,7 +12,7 @@ namespace Kakoune
 
 struct DisplayCoord : LineAndColumn<DisplayCoord>
 {
-    DisplayCoord(LineCount line = 0, int column = 0)
+    DisplayCoord(LineCount line = 0, CharCount column = 0)
         : LineAndColumn(line, column) {}
 
     template<typename T>
diff --git a/src/file.cc b/src/file.cc
index ec6a4f67..936b6fb3 100644
--- a/src/file.cc
+++ b/src/file.cc
@@ -24,14 +24,14 @@ String parse_filename(const String& filename)
     if (filename.length() > 2 and filename[0] == '~' and filename[1] == '/')
         return parse_filename("$HOME/" + filename.substr(2));
 
-    size_t pos = 0;
+    CharCount pos = 0;
     String result;
-    for (size_t i = 0; i < filename.length(); ++i)
+    for (CharCount i = 0; i < filename.length(); ++i)
     {
         if (filename[i] == '$' and (i == 0 or filename[i-1] != '\\'))
         {
             result += filename.substr(pos, i - pos);
-            size_t end = i+1;
+            CharCount end = i+1;
             while (end != filename.length() and isidentifier(filename[end]))
                 ++end;
             String var_name = filename.substr(i+1, end - i - 1);
diff --git a/src/filter_group.cc b/src/filter_group.cc
index eabe0427..ea44bffa 100644
--- a/src/filter_group.cc
+++ b/src/filter_group.cc
@@ -40,13 +40,13 @@ FilterGroup& FilterGroup::get_group(const String& id)
 
 
 CandidateList FilterGroup::complete_id(const String& prefix,
-                                            size_t cursor_pos)
+                                       CharCount cursor_pos)
 {
     return m_filters.complete_id(prefix, cursor_pos);
 }
 
 CandidateList FilterGroup::complete_group_id(const String& prefix,
-                                                  size_t cursor_pos)
+                                             CharCount cursor_pos)
 {
     return m_filters.complete_id_if(
         prefix, cursor_pos,
diff --git a/src/filter_group.hh b/src/filter_group.hh
index 7d1aa60f..8c93936b 100644
--- a/src/filter_group.hh
+++ b/src/filter_group.hh
@@ -19,8 +19,8 @@ public:
 
     FilterGroup& get_group(const String& id);
 
-    CandidateList complete_id(const String& prefix, size_t cursor_pos);
-    CandidateList complete_group_id(const String& prefix, size_t cursor_pos);
+    CandidateList complete_id(const String& prefix, CharCount cursor_pos);
+    CandidateList complete_group_id(const String& prefix, CharCount cursor_pos);
 
 private:
     idvaluemap<String, FilterFunc> m_filters;
diff --git a/src/filter_registry.cc b/src/filter_registry.cc
index a2a08266..65070bdf 100644
--- a/src/filter_registry.cc
+++ b/src/filter_registry.cc
@@ -31,7 +31,7 @@ void FilterRegistry::add_filter_to_group(FilterGroup& group,
 }
 
 CandidateList FilterRegistry::complete_filter(const String& prefix,
-                                              size_t cursor_pos)
+                                              CharCount cursor_pos)
 {
     return m_factories.complete_id(prefix, cursor_pos);
 }
diff --git a/src/filter_registry.hh b/src/filter_registry.hh
index cdae62ab..77763782 100644
--- a/src/filter_registry.hh
+++ b/src/filter_registry.hh
@@ -30,7 +30,7 @@ public:
                              const FilterParameters& parameters);
 
     CandidateList complete_filter(const String& prefix,
-                                  size_t cursor_pos);
+                                  CharCount cursor_pos);
 
 private:
     idvaluemap<String, FilterFactory> m_factories;
diff --git a/src/highlighter_group.cc b/src/highlighter_group.cc
index 5203f2a6..57b21a5c 100644
--- a/src/highlighter_group.cc
+++ b/src/highlighter_group.cc
@@ -39,13 +39,13 @@ HighlighterGroup& HighlighterGroup::get_group(const String& id)
 
 
 CandidateList HighlighterGroup::complete_id(const String& prefix,
-                                            size_t cursor_pos)
+                                            CharCount cursor_pos)
 {
     return m_highlighters.complete_id(prefix, cursor_pos);
 }
 
 CandidateList HighlighterGroup::complete_group_id(const String& prefix,
-                                                  size_t cursor_pos)
+                                                  CharCount cursor_pos)
 {
     return m_highlighters.complete_id_if(
         prefix, cursor_pos,
diff --git a/src/highlighter_group.hh b/src/highlighter_group.hh
index 79128ac7..9b4f1bf0 100644
--- a/src/highlighter_group.hh
+++ b/src/highlighter_group.hh
@@ -22,8 +22,8 @@ public:
 
     HighlighterGroup& get_group(const String& id);
 
-    CandidateList complete_id(const String& prefix, size_t cursor_pos);
-    CandidateList complete_group_id(const String& prefix, size_t cursor_pos);
+    CandidateList complete_id(const String& prefix, CharCount cursor_pos);
+    CandidateList complete_group_id(const String& prefix, CharCount cursor_pos);
 
 private:
     idvaluemap<String, HighlighterFunc> m_highlighters;
diff --git a/src/highlighter_registry.cc b/src/highlighter_registry.cc
index b2ca4e97..46038aa3 100644
--- a/src/highlighter_registry.cc
+++ b/src/highlighter_registry.cc
@@ -33,7 +33,7 @@ void HighlighterRegistry::add_highlighter_to_group(Window& window,
 }
 
 CandidateList HighlighterRegistry::complete_highlighter(const String& prefix,
-                                                        size_t cursor_pos)
+                                                        CharCount cursor_pos)
 {
     return m_factories.complete_id(prefix, cursor_pos);
 }
diff --git a/src/highlighter_registry.hh b/src/highlighter_registry.hh
index 92da5c66..2a3f740d 100644
--- a/src/highlighter_registry.hh
+++ b/src/highlighter_registry.hh
@@ -30,7 +30,7 @@ public:
                                   const HighlighterParameters& parameters);
 
     CandidateList complete_highlighter(const String& prefix,
-                                      size_t cursor_pos);
+                                      CharCount cursor_pos);
 
 private:
     idvaluemap<String, HighlighterFactory> m_factories;
diff --git a/src/idvaluemap.hh b/src/idvaluemap.hh
index f6627872..c65f35fc 100644
--- a/src/idvaluemap.hh
+++ b/src/idvaluemap.hh
@@ -65,7 +65,7 @@ public:
 
     template<typename _Condition>
     CandidateList complete_id_if(const String& prefix,
-                                 size_t cursor_pos,
+                                 CharCount cursor_pos,
                                  _Condition condition)
     {
         String real_prefix = prefix.substr(0, cursor_pos);
@@ -83,7 +83,7 @@ public:
     }
 
     CandidateList complete_id(const String& prefix,
-                              size_t cursor_pos)
+                              CharCount cursor_pos)
     {
         return complete_id_if(
             prefix, cursor_pos, [](const value_type&) { return true; });
diff --git a/src/keys.cc b/src/keys.cc
index d231cfac..5acfdaed 100644
--- a/src/keys.cc
+++ b/src/keys.cc
@@ -14,11 +14,11 @@ static std::unordered_map<String, Character> keynamemap = {
 KeyList parse_keys(const String& str)
 {
     KeyList result;
-    for (size_t pos = 0; pos < str.length(); ++pos)
+    for (CharCount pos = 0; pos < str.length(); ++pos)
     {
         if (str[pos] == '<')
         {
-            size_t end_pos = pos;
+            CharCount end_pos = pos;
             while (end_pos < str.length() and str[end_pos] != '>')
                 ++end_pos;
 
diff --git a/src/line_and_column.hh b/src/line_and_column.hh
index 3e03d1b9..cceaa459 100644
--- a/src/line_and_column.hh
+++ b/src/line_and_column.hh
@@ -10,9 +10,9 @@ template<typename EffectiveType>
 struct LineAndColumn
 {
     LineCount line;
-    int column;
+    CharCount column;
 
-    LineAndColumn(LineCount line = 0, int column = 0)
+    LineAndColumn(LineCount line = 0, CharCount column = 0)
         : line(line), column(column) {}
 
     EffectiveType operator+(const EffectiveType& other) const
diff --git a/src/ncurses.cc b/src/ncurses.cc
index b18e048e..c9dd6bde 100644
--- a/src/ncurses.cc
+++ b/src/ncurses.cc
@@ -113,7 +113,7 @@ void NCursesClient::draw_window(Window& window)
             String content = atom.content.content();
             if (content[content.length()-1] == '\n')
             {
-                addnstr(content.c_str(), content.length() - 1);
+                addnstr(content.c_str(), (int)content.length() - 1);
                 addch(' ');
             }
             else
@@ -139,9 +139,9 @@ void NCursesClient::draw_window(Window& window)
     static int last_status_length = 0;
     move(max_y, max_x - last_status_length);
     clrtoeol();
-    move(max_y, max_x - status_line.length());
+    move(max_y, max_x - (int)status_line.length());
     addstr(status_line.c_str());
-    last_status_length = status_line.length();
+    last_status_length = (int)status_line.length();
 }
 
 Key NCursesClient::get_key()
@@ -179,7 +179,7 @@ String NCursesClient::prompt(const String& text, const Context& context, Complet
     addstr(text.c_str());
     clrtoeol();
 
-    size_t cursor_pos = 0;
+    CharCount cursor_pos = 0;
 
     Completions completions;
     int current_completion = -1;
@@ -285,7 +285,7 @@ String NCursesClient::prompt(const String& text, const Context& context, Complet
             else
                 completion = completions.candidates[current_completion];
 
-            move(max_y-1, text.length());
+            move(max_y-1, (int)text.length());
             result = result.substr(0, completions.start) + completion;
             cursor_pos = completions.start + completion.length();
             break;
@@ -296,10 +296,10 @@ String NCursesClient::prompt(const String& text, const Context& context, Complet
             ++cursor_pos;
         }
 
-        move(max_y - 1, text.length());
+        move(max_y - 1, (int)text.length());
         clrtoeol();
         addstr(result.c_str());
-        move(max_y - 1, text.length() + cursor_pos);
+        move(max_y - 1, (int)(text.length() + cursor_pos));
         refresh();
     }
     return result;
diff --git a/src/option_manager.cc b/src/option_manager.cc
index 487fca6b..1a09361d 100644
--- a/src/option_manager.cc
+++ b/src/option_manager.cc
@@ -57,7 +57,7 @@ const Option& OptionManager::operator[](const String& name) const
 }
 
 CandidateList OptionManager::complete_option_name(const String& prefix,
-                                                  size_t cursor_pos)
+                                                  CharCount cursor_pos)
 {
     String real_prefix = prefix.substr(0, cursor_pos);
     CandidateList result;
diff --git a/src/option_manager.hh b/src/option_manager.hh
index f6d21bd2..221239fd 100644
--- a/src/option_manager.hh
+++ b/src/option_manager.hh
@@ -57,7 +57,7 @@ public:
     void set_option(const String& name, const Option& value);
 
     CandidateList complete_option_name(const String& prefix,
-                                       size_t cursor_pos);
+                                       CharCount cursor_pos);
 
     typedef std::unordered_map<String, Option> OptionMap;
     OptionMap flatten_options() const;
diff --git a/src/string.hh b/src/string.hh
index cd5cfe1d..58dd79b7 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -5,6 +5,7 @@
 #include <iosfwd>
 
 #include "memoryview.hh"
+#include "units.hh"
 
 namespace Kakoune
 {
@@ -23,8 +24,8 @@ public:
    template<typename Iterator>
    String(Iterator begin, Iterator end) : m_content(begin, end) {}
 
-   Character operator[](size_t pos) const { return static_cast<Character>(m_content[pos]); }
-   size_t    length() const { return m_content.length(); }
+   Character operator[](CharCount pos) const { return static_cast<Character>(m_content[(int)pos]); }
+   CharCount length() const { return m_content.length(); }
    bool      empty()  const { return m_content.empty(); }
 
    bool      operator== (const String& other) const { return m_content == other.m_content; }
@@ -43,7 +44,7 @@ public:
    memoryview<char> data()  const { return memoryview<char>(m_content.data(), m_content.size()); }
    const char*      c_str() const { return m_content.c_str(); }
 
-   String substr(size_t pos, size_t length = -1) const { return String(m_content.substr(pos, length)); }
+   String substr(CharCount pos, CharCount length = -1) const { return String(m_content.substr((int)pos, (int)length)); }
 
    class iterator
    {
diff --git a/src/units.hh b/src/units.hh
index 8a1180de..ca9eb39a 100644
--- a/src/units.hh
+++ b/src/units.hh
@@ -67,6 +67,9 @@ public:
     bool operator>=(const RealType& other) const
     { return m_value >= other.m_value; }
 
+    bool operator!() const
+    { return !m_value; }
+
     explicit operator ValueType() const { return m_value; }
 private:
    ValueType m_value;
@@ -82,6 +85,16 @@ inline LineCount operator"" _line(unsigned long long int value)
     return LineCount(value);
 }
 
+struct CharCount : public StronglyTypedInteger<CharCount, int>
+{
+    CharCount(int value) : StronglyTypedInteger<CharCount>(value) {}
+};
+
+inline CharCount operator"" _char(unsigned long long int value)
+{
+    return CharCount(value);
+}
+
 }
 
 #endif // units_hh_INCLUDED
diff --git a/src/window.cc b/src/window.cc
index cc60d1f1..c330a7ec 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -56,7 +56,7 @@ void Window::update_display_buffer()
         BufferIterator line_end   = buffer().iterator_at_line_end(pos);
 
         BufferIterator end;
-        if (line_end - pos > m_dimensions.column)
+        if (CharCount(line_end - pos) > m_dimensions.column)
             end = pos + m_dimensions.column;
         else
             end = line_end;
@@ -100,7 +100,7 @@ void Window::scroll_to_keep_cursor_visible_ifn()
     // (this is only valid if highlighting one line and multiple lines put
     // the cursor in the same position, however I do not find any sane example
     // of highlighters not doing that)
-    int column = 0;
+    CharCount column = 0;
     for (auto& atom : lines.back())
     {
         if (atom.content.has_buffer_range() and
@@ -136,7 +136,7 @@ String Window::status_line() const
     oss << buffer().name();
     if (buffer().is_modified())
         oss << " [+]";
-    oss << " -- " << (int)cursor.line+1 << "," << cursor.column+1
+    oss << " -- " << (int)cursor.line+1 << "," << (int)cursor.column+1
         << " -- " << selections().size() << " sel -- ";
     if (is_editing())
         oss << "[Insert]";