Add automatic completion display in prompt mode

Controlled by the autoshowcompl option
Completers now take a CompletionFlag parameter, used to specify
we want fast completion (tag completion can be slow, we do not
want to run it if not explicitely wanted by the user).

README.asciidoc

@@ -394,6 +394,8 @@ Some options are built in kakoune, and can be used to control it's behaviour:
    candidates exist, enable completion with common prefix.
  * +incsearch+ _bool_: execute search as it is typed
  * +autoinfo+ _bool_: display automatic information box for certain commands.
+ * +autoshowcompl+ _bool_: automatically display possible completions when
+   editing a prompt.
  * +ignored_files+ _regex_: filenames matching this regex wont be considered
    as candidates on filename completion (except if the text being completed
    already matches it).

src/client.cc

@@ -410,9 +410,9 @@ public:
             const bool reverse = (key == Key::BackTab);
             CandidateList& candidates = m_completions.candidates;
             // first try, we need to ask our completer for completions
-            if (m_current_completion == -1)
+            if (candidates.empty())
             {
-                m_completions = m_completer(context(), line,
+                m_completions = m_completer(context(), CompletionFlags::None, line,
                                             line.byte_count_to(m_line_editor.cursor_pos()));
                 if (candidates.empty())
                     return;
@@ -451,13 +451,26 @@ public:
             // when we have only one completion candidate, make next tab complete
             // from the new content.
             if (candidates.size() == 1)
-                m_current_completion = -1;
+                candidates.clear();
         }
         else
         {
-            context().ui().menu_hide();
-            m_current_completion = -1;
             m_line_editor.handle_key(key);
+            m_current_completion = -1;
+            context().ui().menu_hide();
+
+            if (context().options()["autoshowcompl"].get<bool>()) try
+            {
+                m_completions = m_completer(context(), CompletionFlags::Fast, line,
+                                            line.byte_count_to(m_line_editor.cursor_pos()));
+                CandidateList& candidates = m_completions.candidates;
+                if (not candidates.empty())
+                {
+                    DisplayCoord menu_pos{ context().ui().dimensions().line, 0_char };
+                    context().ui().menu_show(candidates, menu_pos, get_color("MenuForeground"),
+                                             get_color("MenuBackground"), MenuStyle::Prompt);
+                }
+            } catch (runtime_error&) {}
         }
         display();
         m_callback(line, PromptEvent::Change, context());

src/command_manager.cc

@@ -312,7 +312,7 @@ void CommandManager::execute(const String& command_line,
     execute_single_command(params, context);
 }
 
-Completions CommandManager::complete(const Context& context,
+Completions CommandManager::complete(const Context& context, CompletionFlags flags,
                                      const String& command_line, ByteCount cursor_pos)
 {
     TokenPosList pos_info;
@@ -363,13 +363,14 @@ Completions CommandManager::complete(const Context& context,
     std::vector<String> params;
     for (auto token_it = tokens.begin()+1; token_it != tokens.end(); ++token_it)
         params.push_back(token_it->content());
-    result.candidates = command_it->second.completer(context, params,
+    result.candidates = command_it->second.completer(context, flags, params,
                                                      token_to_complete - 1,
                                                      cursor_pos_in_token);
     return result;
 }
 
 CandidateList PerArgumentCommandCompleter::operator()(const Context& context,
+                                                      CompletionFlags flags,
                                                       CommandParameters params,
                                                       size_t token_to_complete,
                                                       ByteCount pos_in_token) const
@@ -382,7 +383,7 @@ CandidateList PerArgumentCommandCompleter::operator()(const Context& context,
 
     const String& argument = token_to_complete < params.size() ?
                              params[token_to_complete] : String();
-    return m_completers[token_to_complete](context, argument, pos_in_token);
+    return m_completers[token_to_complete](context, flags, argument, pos_in_token);
 }
 
 }

src/command_manager.hh

@@ -18,6 +18,7 @@ struct Context;
 using CommandParameters = memoryview<String>;
 using Command = std::function<void (CommandParameters, Context& context)>;
 using CommandCompleter = std::function<CandidateList (const Context& context,
+                                                      CompletionFlags,
                                                       CommandParameters,
                                                       size_t, ByteCount)>;
 
@@ -25,6 +26,7 @@ class PerArgumentCommandCompleter
 {
 public:
     using ArgumentCompleter = std::function<CandidateList (const Context&,
+                                            CompletionFlags flags,
                                             const String&, ByteCount)>;
     using ArgumentCompleterList = memoryview<ArgumentCompleter>;
 
@@ -32,6 +34,7 @@ public:
         : m_completers(completers.begin(), completers.end()) {}
 
     CandidateList operator()(const Context& context,
+                             CompletionFlags flags,
                              CommandParameters params,
                              size_t token_to_complete,
                              ByteCount pos_in_token) const;
@@ -47,7 +50,7 @@ public:
                  memoryview<String> shell_params = {},
                  const EnvVarMap& env_vars = EnvVarMap{});
 
-    Completions complete(const Context& context,
+    Completions complete(const Context& context, CompletionFlags flags,
                          const String& command_line, ByteCount cursor_pos);
 
     bool command_defined(const String& command_name) const;

src/commands.cc

@@ -405,7 +405,8 @@ void define_command(CommandParameters params, Context& context)
     CommandCompleter completer;
     if (parser.has_option("file-completion"))
     {
-        completer = [](const Context& context, CommandParameters params,
+        completer = [](const Context& context, CompletionFlags flags,
+                       CommandParameters params,
                        size_t token_to_complete, ByteCount pos_in_token)
         {
              const String& prefix = token_to_complete < params.size() ?
@@ -416,9 +417,12 @@ void define_command(CommandParameters params, Context& context)
     else if (parser.has_option("shell-completion"))
     {
         String shell_cmd = parser.option_value("shell-completion");
-        completer = [=](const Context& context, CommandParameters params,
+        completer = [=](const Context& context, CompletionFlags flags,
+                        CommandParameters params,
                         size_t token_to_complete, ByteCount pos_in_token)
         {
+            if (flags == CompletionFlags::Fast) // no shell on fast completion
+                return CandidateList{};
             EnvVarMap vars = {
                 { "token_to_complete", to_string(token_to_complete) },
                 { "pos_in_token",      to_string(pos_in_token) }
@@ -743,8 +747,9 @@ void change_working_directory(CommandParameters params, Context&)
 template<typename GetRootGroup>
 CommandCompleter group_rm_completer(GetRootGroup get_root_group)
 {
-    return [=](const Context& context, CommandParameters params,
+    return [=](const Context& context, CompletionFlags flags,
-               size_t token_to_complete, ByteCount pos_in_token) {
+               CommandParameters params, size_t token_to_complete,
+               ByteCount pos_in_token) {
         auto& root_group = get_root_group(context);
         const String& arg = token_to_complete < params.size() ?
                             params[token_to_complete] : String();
@@ -759,8 +764,9 @@ CommandCompleter group_rm_completer(GetRootGroup get_root_group)
 template<typename FactoryRegistry, typename GetRootGroup>
 CommandCompleter group_add_completer(GetRootGroup get_root_group)
 {
-    return [=](const Context& context, CommandParameters params,
+    return [=](const Context& context, CompletionFlags flags,
-               size_t token_to_complete, ByteCount pos_in_token) {
+               CommandParameters params, size_t token_to_complete,
+               ByteCount pos_in_token) {
         auto& root_group = get_root_group(context);
         const String& arg = token_to_complete < params.size() ?
                             params[token_to_complete] : String();
@@ -810,7 +816,7 @@ void register_commands()
     cm.register_commands({"nop"}, [](CommandParameters, Context&){});
 
     PerArgumentCommandCompleter filename_completer({
-         [](const Context& context, const String& prefix, ByteCount cursor_pos)
+         [](const Context& context, CompletionFlags flags, const String& prefix, ByteCount cursor_pos)
          { return complete_filename(prefix, context.options()["ignored_files"].get<Regex>(), cursor_pos); }
     });
     cm.register_commands({ "e", "edit" }, edit<false>, filename_completer);
@@ -823,7 +829,7 @@ void register_commands()
     cm.register_command("wq!", write_and_quit<true>);
 
     PerArgumentCommandCompleter buffer_completer({
-        [](const Context& context, const String& prefix, ByteCount cursor_pos)
+        [](const Context& context, CompletionFlags flags, const String& prefix, ByteCount cursor_pos)
         { return BufferManager::instance().complete_buffername(prefix, cursor_pos); }
     });
     cm.register_commands({ "b", "buffer" }, show_buffer, buffer_completer);
@@ -857,7 +863,7 @@ void register_commands()
     cm.register_command("debug", write_debug_message);
 
     cm.register_command("set", set_option,
-                        [](const Context& context, CommandParameters params, size_t token_to_complete, ByteCount pos_in_token)
+                        [](const Context& context, CompletionFlags, CommandParameters params, size_t token_to_complete, ByteCount pos_in_token)
                         {
                             if (token_to_complete == 0)
                             {

src/completion.hh

@@ -26,10 +26,15 @@ struct Completions
         : start(start), end(end) {}
 };
 
-typedef std::function<Completions (const Context&,
+enum class CompletionFlags
-                                   const String&, ByteCount)> Completer;
+{
+    None,
+    Fast
+};
+using Completer = std::function<Completions (const Context&, CompletionFlags,
+                                             const String&, ByteCount)>;
 
-inline Completions complete_nothing(const Context& context,
+inline Completions complete_nothing(const Context& context, CompletionFlags,
                                     const String&, ByteCount cursor_pos)
 {
     return Completions(cursor_pos, cursor_pos);

src/normal.cc

@@ -249,7 +249,7 @@ void command(Context& context, int)
 {
     context.client().prompt(
         ":", get_color("Prompt"),
-        std::bind(&CommandManager::complete, &CommandManager::instance(), _1, _2, _3),
+        std::bind(&CommandManager::complete, &CommandManager::instance(), _1, _2, _3, _4),
         [](const String& cmdline, PromptEvent event, Context& context) {
              if (event == PromptEvent::Validate)
                  CommandManager::instance().execute(cmdline, context);

src/option_manager.cc

@@ -116,6 +116,7 @@ GlobalOptions::GlobalOptions()
     declare_option<bool>("complete_prefix", true);
     declare_option<bool>("incsearch", true);
     declare_option<bool>("autoinfo", true);
+    declare_option<bool>("autoshowcompl", true);
     declare_option<Regex>("ignored_files", Regex{R"(^(\..*|.*\.(o|so|a))$)"});
     declare_option<String>("filetype", "");
     declare_option<std::vector<String>>("completions", {});