NAME
    Vi::QuickFix - Support for vim's QuickFix mode

SYNOPSIS
      use Vi::QuickFix;
      use Vi::QuickFix <errorfile>;
      use Vi::QuickFix <options>;
      use Vi::QuickFix <options> <errorfile>;

    where "<options>" is one or more of "silent", "sig", and "tie".

DESCRIPTION
    When "Vi::QuickFix" is active, Perl logs errors and warnings to an
    *error file* named, by default, "errors.err". This file is picked up
    when vim is called in QuickFix mode as "vim -q". Vim starts editing the
    perl source where the first error occured, at the error location.
    QuickFix allows you to jump from one error to another, switching files
    as necessary. Type ":help quickfix" in vim for a description.

    To activate QuickFix support, add

        use Vi::QuickFix;

    or, specifying an error file

        use Vi::QuickFix '/my/errorfile';

    early in the main program, before other "use" statements.

    To leave the program file unaltered, Vi::QuickFix can be invoked from
    the command line as

        perl -MVi::QuickFix program
    or
        perl -MVi::QuickFix=/my/errorfile program

    "Vi::QuickFix" is meant to be used as a development tool, not to remain
    in a distributed product. When the program ends, a warning is issued,
    indicating that "Vi::QuickFix" was active. This has the side effect that
    there is always an entry in the error file which points to the source
    file where "Vi::QuickFix" was invoked, normally the main program. "vi
    -q" will edit this file when other error entries don't point it
    elsewhere. Use the "silent" option with "Vi::QuickFix" to suppress this
    warning.

    It is a fatal error when the error file cannot be opened. If the error
    file is empty (can only happen with "silent"), it is removed at the end
    of the run.

USAGE
    The module file .../Vi/QuickFix.pm can also be called as an executable.
    In that mode, it behaves (roughly) like the "cat" command, but also
    monitors the stream and logs Perl warnings and error messages to the
    error file. The error file can be set through the switches "-f" or "-q".
    No warning about QuickFix activity is issued in this mode.

    Called with -v, it prints the version and exits.

IMPLEMENTATION
    For a debugging tool, an implementation note is in order.

    Perl offers to obvious ways to watch and capture its error output. One
    is through the (pseudo-) signal handlers $SIG{__WARN__} and
    $SIG{__DIE__}. The other is through "tie"-ing the "STDERR" file handle.

    "Vi::QuickFix" can use either method to create the error file. As it
    turns out, the ability to tie "STDERR" is relatively new with Perl, as
    of version 5.8.1. With Versions 5.8.0 and earlier, a number of internal
    errors and warnings don't respect tie, so this method cannot be used.
    With Perl versions ealier than 5.8.1, "Vi::QuickFix" uses %SIG handlers
    to catch messages. With newer versions, "Vi::Quickfix" ties "STDERR" so
    that it (additionally) writes to the error file.

    A specific method can be requested through the options "sig" and "tie",
    as in

        use Vi::QuickFix qw( sig);

    Requesting "tie" with a Perl version that can't handle it is a fatal
    error, so the only option that does anything useful is "sig" with a
    new-ish Perl. It can be useful when "tie"-ing STDERR conflicts with the
    surrounding code.

CONFLICTS
    Such a conflict can occur with the "sig" method as well, and it can
    happen in two ways. Either "Vi::QuickFix" already finds a resource (a
    %SIG handler or a tie on "STDERR") occupied at "use" time, or the
    surrounding code commandeers the resource after the fact.

    All such conflicts can be avoided by using "Vi::QuickFix" in a separate
    process, as noted under ""USAGE".

    However, if "STDERR" is already tied when "Vi::QuickFix" is "use"d, it
    cannot employ the "tie" method, and by default reverts to "sig". If the
    "tie" method is specifically requested, a fatal error results.

    If the "sig" method finds one of the handlers ("__WARN__" and "__DIE__")
    already occupied, it chains to the previous handler after doing its
    thing, so that is not considered an obstacle. "Chaining" file ties is
    harder, and has not been attempted.

    If "Vi::QuickFix" is already active, the surrounding code may later
    occupy a resource it is using. There is little that can be done when
    that happens, except issue a warning which is also logged to the error
    file. This can help in finding the source of the conflict. In "silent"
    mode, no such warning is given.

    The warning is triggered when the corresponding resource is overwritten,
    except when the overwriting program keeps a copy of it. It is then
    assumed that the program will keep it functioning. Since we're still
    talking implementation -- it is actually triggered through a DESTROY
    method when the corresponding object goes out of scope. %SIG handlers
    are code objects just for this reason.

BUGS
    "no Vi::QuickFix" has no effect

AUTHOR
            Anno Siegel
            CPAN ID: ANNO
            siegel@zrz.tu-berlin.de
            http://www.tu-berlin.de/~siegel

COPYRIGHT
    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

    The full text of the license can be found in the LICENSE file included
    with this module.

SEE ALSO
    perl(1), vim(1).