i3-switch-recent

#!/usr/bin/env python3
"""
Switch between 2 most recent containers.

This operation ignores scratchpads and explicitly unfocuses them when called to
switch between normal containers.

Ignoring scratchpads is implemented with a blacklist, the window::move
event provides the most authoritive information in container.scratchpad_state.
"""

import i3ipc

SCRATCHPAD_BLACKLIST = set()
WINDOW_STACK = []
SWITCH_KEYBIND = 'Mod4+BackSpace'  # see $HOME/.config/i3/config


def switch(conn, event):
    binding = '%s+%s' % ('+'.join(event.binding.mods), event.binding.symbol)
    if len(WINDOW_STACK) > 1 and binding == SWITCH_KEYBIND:
        # if currently focused window is scratchpad hide it. `scratchpad show`
        # actually toggles and doesn't just "show".
        if conn.get_tree().find_focused().id in SCRATCHPAD_BLACKLIST:
            conn.command('scratchpad show')

        window_id = WINDOW_STACK.pop()
        conn.command('[con_id="%s"] focus' % window_id)


def insert(conn, event):
    id_ = event.container.id
    if (id_ not in SCRATCHPAD_BLACKLIST
            # prevent a stack with the same id twice.
            and not (WINDOW_STACK and id_ == WINDOW_STACK[0])):
        WINDOW_STACK.insert(0, id_)
        # Only keep a list of max two elements. [focused, recent].
        del WINDOW_STACK[2:]


def blacklist(conn, event):
    global SCRATCHPAD_BLACKLIST
    # when a scratchpad is focused it is first moved in the tree. The state is
    # then set to fresh. This is the clearest point to identify a scratchpad
    # and to blacklist it. Also, a scratchpad can also have multiple clients,
    # so add all to the blacklist.
    if event.container.scratchpad_state == 'fresh':
        SCRATCHPAD_BLACKLIST |= {c.id for c in event.container.leaves()}


def clean(conn, event):
    # Prevent the blacklist from growing out of control.
    SCRATCHPAD_BLACKLIST.discard(event.container.id)


if __name__ == '__main__':
    conn = i3ipc.Connection()
    conn.on('binding::run', switch)
    conn.on('window::focus', insert)
    conn.on('window::move', blacklist)
    conn.on('window::close', clean)
    conn.main()