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# deck-it - the virtual monitor setup
# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""The virtual monitor half: a headless Hyprland output sized to the tablet."""
import json
import os
import re
import shutil
import signal
import subprocess
import sys
import time
from pathlib import Path
def run(cmd, timeout=2):
try:
return subprocess.run(cmd, capture_output=True, text=True, timeout=timeout).stdout.strip()
except (OSError, subprocess.TimeoutExpired):
return ""
def tablet_resolution(cfg: dict, adb=None) -> str:
res = cfg.get("display", {}).get("resolution", "auto")
if res != "auto":
return res
read = adb or (lambda: run(["adb", "shell", "wm", "size"]))
m = re.search(r"(\d+)x(\d+)", read())
if not m:
sys.exit("Could not read the tablet resolution; set display.resolution in the config")
w, h = sorted(map(int, m.groups()), reverse=True)
return f"{w}x{h}"
def below_position(ref: dict, resolution: str, scale=1) -> str:
"""Center a monitor below `ref` (a hyprctl monitor dict)."""
width = round(int(re.match(r"(\d+)x", resolution).group(1)) / scale)
return f"{ref['x'] + (ref['width'] - width) // 2}x{ref['y'] + ref['height']}"
def hypr_lua(cfg: dict) -> bool:
mode = cfg.get("hyprland", "auto")
if mode == "auto":
return (Path.home() / ".config/hypr/hyprland.lua").is_file()
return mode == "lua"
def _swaybg_for(output: str, proc: Path = Path("/proc")):
"""(pid, image, mode) of the swaybg process painting `output`, from /proc."""
for cmdline in proc.glob("[0-9]*/cmdline"):
try:
argv = cmdline.read_bytes().decode(errors="replace").split("\0")
except OSError:
continue
if not argv or not argv[0].endswith("swaybg"):
continue
out = image = None
mode = "fill"
for i, arg in enumerate(argv):
if i + 1 >= len(argv):
break
if arg == "-o":
out = argv[i + 1]
elif arg == "-i":
image = argv[i + 1]
elif arg == "-m":
mode = argv[i + 1]
if out == output and image:
return int(cmdline.parent.name), image, mode
return None
def setup_display(cfg: dict, run_cmd=None, popen=None) -> None:
run_cmd = run_cmd or run
popen = popen or (lambda cmd: subprocess.Popen(
cmd, start_new_session=True, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL))
d = cfg.get("display", {})
mon = d.get("name", "TAB")
monitors = json.loads(run_cmd(["hyprctl", "monitors", "-j"]) or "[]")
if not any(m["name"] == mon for m in monitors):
run_cmd(["hyprctl", "output", "create", "headless", mon])
time.sleep(1)
# Creating the output can re-flow the layout, so read it again.
monitors = json.loads(run_cmd(["hyprctl", "monitors", "-j"]) or "[]")
mode = f"{tablet_resolution(cfg)}@{d.get('refresh', 60)}"
pos = d.get("position", "auto-right")
scale = d.get("scale", 1)
if pos in ("auto-below", "below"):
ref = next((m for m in monitors if m["name"] != mon), monitors[0])
pos = below_position(ref, mode, scale)
if hypr_lua(cfg):
run_cmd(["hyprctl", "eval",
f'hl.monitor({{output="{mon}", mode="{mode}", position="{pos}", scale={scale}}})'])
else:
run_cmd(["hyprctl", "keyword", "monitor", f"{mon},{mode},{pos},{scale}"])
if d.get("wallpaper", True):
others = [m["name"] for m in monitors if m["name"] != mon]
tool = shutil.which("awww") or shutil.which("swww")
if tool:
for line in run_cmd([tool, "query"]).splitlines():
if others and others[0] in line and "image: " in line:
run_cmd([tool, "img", "-o", mon, line.split("image: ", 1)[1]], timeout=10)
break
elif shutil.which("swaybg"):
# swaybg runs one process per output; copy the first monitor's image.
source = next((found for name in others if (found := _swaybg_for(name))), None)
if source:
existing = _swaybg_for(mon)
if existing:
try:
os.kill(existing[0], signal.SIGTERM)
except OSError:
pass
popen(["swaybg", "-o", mon, "-i", source[1], "-m", source[2]])
print(f"{mon}: {mode} at {pos}")
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