Minimal demo of a working passive keyboard grab in X11 from a kitten for kitty terminal emulator

minimal_popup.py

#!/usr/bin/env python3

import os
import sys
from Xlib import X
from typing import List

from kitty.constants import is_macos

# Installation: place minimal_popup.py in your ~/.config/kitty
# Usage: kitty +kitten minimal_popup <command>

def setup_x11_window(win_id: int) -> None:

    import ctypes
    from kitty.fast_data_types import x11_display

    X11 = ctypes.CDLL("libX11.so")

    class Display(ctypes.Structure):
        """ opaque struct """

    # The Pixmap, Colormap, and Cursor types in Xlib are all defined as "XID".
    # If Xlib has been built with _XSERVER64 defined (see X.h +59), then XID is
    # defined as "unsigned long" (which on a typical "64 bit" system is 8
    # bytes)
    # Otherwise, XID is defined as a CARD32 (see Xmd.h +115) which, on a *non*
    # "64 bit" system (one where an unsigned long is 4 bytes), is also defined
    # as an unsigned long.  All that to say, it *should* be safe to consider
    # XID to be always an ulong except if we are using a 32 bit xserver in a 64
    # bit environment, such that ctypes defines c_ulong as 8 bytes but Xlib's
    # ulong is 4.  I'm not sure what a reliable way to detect that would be, so
    # for now we let sleeping dragons lie~
    XID_type = ctypes.c_ulong

    override_redirect_mask = ctypes.c_long(1<<9)

    # Xlib.h +298
    class XSetWindowAttributes(ctypes.Structure):
        _fields_ = [
            ('background_pixmap',     XID_type),       #Pixmap
            ('background_pixel',      ctypes.c_ulong),
            ('border_pixmap',         XID_type),       #Pixmap
            ('border_pixel',          ctypes.c_ulong),
            ('bit_gravity',           ctypes.c_int),
            ('win_gravity',           ctypes.c_int),
            ('backing_store',         ctypes.c_int),
            ('backing_planes',        ctypes.c_ulong),
            ('backing_pixel',         ctypes.c_ulong),
            ('save_under',            ctypes.c_bool),	
            ('event_mask',            ctypes.c_long),
            ('do_not_propagate_mask', ctypes.c_long),
            ('override_redirect',     ctypes.c_bool),
            ('colormap',              XID_type),       #Colormap
            ('cursor',                XID_type),       #Cursor
        ]

    dpy = x11_display()
    dpy = ctypes.cast(dpy, ctypes.POINTER(Display))
    X11.XMapWindow.restype = ctypes.c_int
    window_attributes = XSetWindowAttributes()
    window_attributes.override_redirect = True
    X11.XChangeWindowAttributes(dpy, win_id,
                                override_redirect_mask,
                                ctypes.pointer(window_attributes)
                                )
    X11.XMapWindow(dpy, win_id)
    X11.XGrabKeyboard(dpy, win_id, False, X.GrabModeAsync, X.GrabModeAsync, X.CurrentTime)


def main(sys_args: List[str]) -> None:
    global args
    if is_macos or not os.environ.get('DISPLAY'):
        raise SystemExit('Currently the popup kitten is supported only on X11 desktops')
    items = sys_args[1:]
    if not items:
        raise SystemExit('You must specify the program to run')
    sys.argv = ['kitty']
    sys.argv.extend(items)
    from kitty.main import main as real_main, run_app
    run_app.first_window_callback = setup_x11_window
    real_main()


if __name__ == '__main__':
    main(sys.argv)