Initial Motivation

This indenter (initially) was designed to help code typing in a boost::mpl style (i.e. w/ leading comma in formatted (template) parameters list). One may read rationale of such approach in the “C++ Template Metaprogramming: Concepts, Tools, and Techniques from Boost and Beyond” by David Abrahams and Aleksey Gurtovoy. It is really easy to miss a comma when invoke metafunctions and it would lead to really complicated compile errors (a lot of). This technique help to visually control syntax and prevent stupid errors like missed comma.


typedef typename boost::mpl::fold<
    typename boost::mpl::transform_view<
      , boost::remove_pointer<boost::mpl::_>
  , boost::mpl::long_<0>
  , boost::mpl::eval_if<
        boost::mpl::less<boost::mpl::_2, boost::mpl::_1>
      , boost::mpl::_2
      , boost::mpl::_1
  >::type type;

In practice I’ve noticed that this style also can be used to format a long function calls or even for statements. Actually, everything that can be split into several lines could be formatted that way. And yes, it is (really!) convenient to have a delimiter (comma, semicolon, whatever) as a leading character to make it visually noticeable.

// Inheritance list formatting
struct sample
  : public base_1
  , public base_2
  , ...
  , public base_N
    // Parameter list formatting
    void foo(
        const std::string& param_1                      ///< A string parameter
      , double param_2                                  ///< A double parameter
      , ...
      , const some_type& param_N                        ///< An user defined type parameter
        // Split `for` parts into few shortter lines
        for (
            auto first = std::begin(param_1)
          , last = std::end(param_1)
          ; it != last && !is_found && !is_exit_requested
          ; ++it
            auto val = check_some_condition()
              ? get_then_value()
              : get_else_value()

It looks unusual for awhile :) but later it become (quite) “normally” and easily to read and edit :) Really! When you want to add another one parameter to a function declaration, it takes less typing if compare to a “traditional” way :) (especially if you have some help from an editor, like move/duplicate the current line and/or a selected block up/down by a hot-key or having an indenter like this :)

Next improvements was designed to simplify typing C++ code, using most common syntactic rules, like “add spaces around operators and after a comma”, “add space after control keywords, but not after a function name in a call expression”, & etc.

Further improvements bring to the “indenter” some cute features and nowadays I’d prefer to consider it similar to a T9 (an input method for cell phones) for C++ coding, but not as a real indenter in contrast to others, shipped with kate out of the box :) Particularly this indenter exploit can see “impossible” syntax and (try to) transform it to something “reasonable” – i.e. just like T9 it tries to be a predictive.

For example, if you have autobrackets plugin turned ON, when typing some(nested( gives you some(nested(|)) w/ | indicating a current cursor position. If you press , at this position, it gives you the following snippet some(nested(), |) supposing that you want to add one more parameter to a some() call. While typing ; looks like you’ve done with that nested calls and gives you the some(nested());| snippet. Both cases help you to avoid couple of redundant key presses ;)

… but do not even try to use this indenter to (re)format blocks of code! :) It can do some really simple/primitive formatting, but far from good – as I’ve mentioned above: this “not quite indenter”™ designed to help you to “do little more with little less typing” for C++ and code formatting is not a “primary” task for it ;-)

Some features in brief

  • to start a C-style comment block type /* and press ENTER key – it gives you ```cpp /*
  • | */ ```
  • to start doxygen comment block use /** + ENTER. Every following ENTER just extends the current block.
  • to start C++ style comment just type // it will add a one space after ;)
  • I prefer to have on-line-comments (i.e. C++-style comments after some expression) to be aligned at 60th position. So typing // will automatically move comment to that position if there was some code before. Moreover the indenter tries to keep that comments when you use ENTER key to break some complex expressions into a few lines
    // Before pressing ENTER at position marked by '|'
    some_call_with_long parameters_list(|param1, ..., paramN);  // Comment starts here...
    // After pressing ENTER: keep comment at the original line
    some_call_with_long parameters_list(                        // Comment starts here...
      |param1, ..., paramN);
  • …also try to use ENTER in the middle of a comment text ;-)
  • typing /// gives you /// (with a space) or ///< depending on presence of code at the current line
  • from time to time I use grouping in a doxygen documentation, so typing //@ gives you:
  • always add a space after , character – simple, but really convenient! really soon you’ve stopped typing a space after any comma and feel yourself inconvenient with other indenters ;)
  • typing < without a space after some identifier adds a closing angle bracket (like notorious autobrackets plugin do for other bracket types), because template instantiation guessed. So typing std::vector<| gives you std::vector<|>. But std::cout<|> turns into std::cout << | after pressing one more < ;-)
  • a lot punctuation characters being typed withing parenthesis is a some operator (or at least part of), so will be moved out of parenthesis (most likely call expression). Try to type various punctuators at marked position in the following snippet some(|)
  • typing a backslash in on a line of a long MACRO definition cause realign all others to fit to a longest line:
    #define PP_FORM_A_ROW(State, Data, Elem)    \
    {                                         \
      {                                       \
          field_path(                         \
              BOOST_PP_TUPLE_ELEM(2, 0, Data) \
            , BOOST_PP_TUPLE_ELEM(2, 1, Data) \
            , BOOST_PP_TUPLE_ELEM(2, 0, Elem) \
            )                                 \
        , BOOST_PP_TUPLE_ELEM(2, 1, Elem)     \
      }                                       \
    , manage_config_keys::action::GET         \
  • typing R" will initiate a raw string literal
  • alsto try to split a string literal across multiple lines pressing ENTER in the middle ;-)

This not-quite-indenter™ has some other (smaller) features to reduce typing. Hope, you’ll like them if found! ;)

PS: The other things I’ve found useful when typing C++ code can be plugged w/ some Python plugins dedicated to C++.


  • Unfortunately JS indenters in kate nowdays can’t have any GUI, so it is impossible to have a “user firendly” configuration…

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