focus_vim.py

#!/usr/bin/env python3

"""
The script accepts either an argument or stdin line as a Vim server name
and focuses on i3 window contaning that Vim instance.

Read `:help client-server
<http://vimdoc.sourceforge.net/htmldoc/remote.html#client-server>`_.

Requires ``psutil`` ::


    $ pip install psutil


Example usage ::


    $ vim --serverlist | rofi -dmenu -p "Choose Vim server" | focus_vim.py

    $ focus_vim.py <servername>


"""

import re
import sys

import psutil
import i3ipc


def get_window_id_by_pid(pid):
    """
    Find i3 window id by programm's pid.

    **Note**: OS specific, could need changing, works in ArchLinux.

    :param pid: Process id of the program to find window.
    :type pid: int
    :return: i3 window id or None.
    """
    with open('/proc/{}/environ'.format(pid), 'r') as env:
        try:
            pid_env = env.read()
        except (OSError, IOError):
            return None
    match = re.search(r'WINDOWID=(\d+)', pid_env)
    if match is not None:
        wid = int(match.group(1))
        return wid
    return None


def get_pid(server_name):
    """
    Find Vim instance by server name.

    :param server_name: Vim server name.
    :return: Process id.
    """
    for process in psutil.process_iter():
        if (
            '--servername {}'.format(server_name.lower())
            in ' '.join(process.cmdline()).lower()
        ):
            yield process.pid


def get_window_id(server_name):
    """
    Find i3 window id of Vim server instance with a `server_name` name
    of the Vim instance.

    :return: i3 window id.
    """
    pid = None
    wid = None
    while True:
        try:
            pid = next(get_pid(server_name))
        except StopIteration:
            break
        if pid is None:
            continue
        else:
            break
    if pid is not None:
        wid = get_window_id_by_pid(pid)
    return wid


def get_arg_from_stdin():
    """
    Read stdin until EOF or a non-empty line.

    :return: A non-empty line or None.
    """
    return next((line.strip('\n') for line in sys.stdin.readlines()), None)


def main():
    """
    Get a Vim server name either from command line argument or stdin's
    first non-empty line and focus on an i3 window containing Vim
    instance with that server name.
    """
    server_name = None

    if sys.argv[1:]:
        server_name = sys.argv[1]
    else:
        server_name = get_arg_from_stdin()

    if server_name is not None:
        vim_window_id = get_window_id(server_name)
        if vim_window_id is not None:
            con = i3ipc.Connection()
            con.command('[id=%s] focus' % vim_window_id)


if __name__ == "__main__":
    main()