Fix performance of word completion with many different selections

Fixes #1228

src/buffer.hh

@@ -143,6 +143,7 @@ public:
     size_t         current_history_id() const noexcept;
 
     String         string(BufferCoord begin, BufferCoord end) const;
+    StringView     substr(BufferCoord begin, BufferCoord end) const;
 
     const char&    byte_at(BufferCoord c) const;
     ByteCount      distance(BufferCoord begin, BufferCoord end) const;

src/buffer.inl.hh

@@ -89,6 +89,12 @@ inline size_t Buffer::timestamp() const
     return m_changes.size();
 }
 
+inline StringView Buffer::substr(BufferCoord begin, BufferCoord end) const
+{
+    kak_assert(begin.line == end.line);
+    return m_lines[begin.line].substr(begin.column, end.column - begin.column);
+}
+
 inline ConstArrayView<Buffer::Change> Buffer::changes_since(size_t timestamp) const
 {
     if (timestamp < m_changes.size())

src/insert_completer.cc

@@ -90,25 +90,24 @@ InsertCompletion complete_word(const SelectionList& sels, const OptionManager& o
         return {};
 
     BufferCoord word_begin;
-    String prefix;
-    IdMap<int> sel_word_counts;
+    StringView prefix;
+    UnorderedMap<StringView, int> sel_word_counts;
     for (int i = 0; i < sels.size(); ++i)
     {
         Utf8It end{buffer.iterator_at(sels[i].cursor()), buffer};
         Utf8It begin = end-1;
-        if (not skip_while_reverse(begin, buffer.begin(),
-                                   [&](Codepoint c) { return is_word_pred(c); }))
+        if (not skip_while_reverse(begin, buffer.begin(), is_word_pred))
             ++begin;
 
         if (i == sels.main_index())
         {
             word_begin = begin.base().coord();
-            prefix = buffer.string(word_begin, end.base().coord());
+            prefix = buffer.substr(word_begin, end.base().coord());
         }
 
-        skip_while(end, buffer.end(), [&](Codepoint c) { return is_word_pred(c); });
+        skip_while(end, buffer.end(), is_word_pred);
 
-        auto word = buffer.string(begin.base().coord(), end.base().coord());
+        StringView word = buffer.substr(begin.base().coord(), end.base().coord());
         ++sel_word_counts[word];
     }
 
@@ -137,8 +136,8 @@ InsertCompletion complete_word(const SelectionList& sels, const OptionManager& o
     // Remove words that are being edited
     for (auto& word_count : sel_word_counts)
     {
-        if (get_word_db(buffer).get_word_occurences(word_count.key) <= word_count.value)
-            unordered_erase(matches, StringView{word_count.key});
+        if (get_word_db(buffer).get_word_occurences(word_count.first) <= word_count.second)
+            unordered_erase(matches, word_count.first);
     }
 
     if (other_buffers)
@@ -156,7 +155,7 @@ InsertCompletion complete_word(const SelectionList& sels, const OptionManager& o
         if (RankedMatch match{word, prefix})
             matches.emplace_back(match, nullptr);
 
-    unordered_erase(matches, StringView{prefix});
+    unordered_erase(matches, prefix);
     std::sort(matches.begin(), matches.end());
     matches.erase(std::unique(matches.begin(), matches.end()), matches.end());
 
@@ -206,7 +205,7 @@ InsertCompletion complete_filename(const SelectionList& sels,
     if (begin == pos)
         return {};
 
-    auto prefix = buffer.string(begin.coord(), pos.coord());
+    StringView prefix = buffer.substr(begin.coord(), pos.coord());
     if (require_slash and not contains(prefix, '/'))
         return {};
 
@@ -273,8 +272,7 @@ InsertCompletion complete_option(const SelectionList& sels,
 
         if (cursor_pos.line == coord.line and cursor_pos.column >= coord.column)
         {
-            StringView query = buffer[coord.line].substr(
-                coord.column, cursor_pos.column - coord.column);
+            StringView query = buffer.substr(coord, cursor_pos);
 
             const ColumnCount tabstop = options["tabstop"].get<int>();
             const ColumnCount column = get_column(buffer, tabstop, cursor_pos);

src/main.cc

@@ -237,6 +237,12 @@ static void check_timeout(const int& timeout)
         throw runtime_error{"the minimum acceptable timeout is 50 milliseconds"};
 }
 
+static void check_extra_word_char(const String& extra_chars)
+{
+    if (contains_that(extra_chars, is_blank))
+        throw runtime_error{"blanks are not accepted for extra completion characters"};
+}
+
 void register_options()
 {
     OptionsRegistry& reg = GlobalScope::instance().option_registry();
@@ -303,9 +309,10 @@ void register_options()
                        "%val{bufname} %val{cursor_line}:%val{cursor_char_column} "_str);
     reg.declare_option("debug", "various debug flags", DebugFlags::None);
     reg.declare_option("readonly", "prevent buffers from being modified", false);
-    reg.declare_option("completion_extra_word_char",
-                       "Additional characters to be considered as words for insert completion",
-                       ""_str);
+    reg.declare_option<String, check_extra_word_char>(
+        "completion_extra_word_char",
+        "Additional characters to be considered as words for insert completion",
+        ""_str);
 }
 
 static Client* local_client = nullptr;