utils/gatelock
Krzysztof kuhy Rudnicki 24abb22de0 gatelock: preempt a weaker holder blocking a stronger claim's grab
wait_for_turn only helps a weaker locker arriving after a stronger
one; it does nothing when the weaker one is already the incumbent.
On 2026-08-21 diet_guard (rank 100) held the grab for ~3 minutes
against a newly-arriving screen_locker (rank 200), which just
retried and logged instead of ever making progress.

Fix: when a grab is blocked by a holder that outranks-us-not, SIGTERM
it once. The holder's own signal handler already converts SIGTERM
into its normal close() teardown (VT restore, arbiter release,
app-specific on_close) -- this reuses that path rather than adding a
new one, and never signals upward (never disturbs an incumbent that
outranks us), so it cannot become a way to bypass a stronger lock.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018M5gKyYzxWG6QkCaj1wWfk
2026-08-21 12:57:41 +02:00
..
gatelock gatelock: preempt a weaker holder blocking a stronger claim's grab 2026-08-21 12:57:41 +02:00
.pre-commit-config.yaml Stop the recovery tick stealing our own grab, and fix pre-commit for the monorepo 2026-07-26 15:08:41 +02:00
LICENSE Initial gatelock: shared lock-window + HMAC log-integrity backend 2026-06-19 17:39:44 +02:00
pyproject.toml gatelock: preempt a weaker holder blocking a stronger claim's grab 2026-08-21 12:57:41 +02:00
README.md gatelock: warm-tint the unified-design-system palette, add on-fill token 2026-07-21 21:11:07 +02:00
requirements.txt Initial gatelock: shared lock-window + HMAC log-integrity backend 2026-06-19 17:39:44 +02:00

gatelock

Shared fullscreen lock-window + HMAC log-integrity backend, extracted from three personal automation tools that each independently implemented "lock the screen with a blocking overlay until a condition is met": diet_guard, wake_alarm, and screen-locker.

Why

All three reimplemented the same tkinter fullscreen mechanics (overrideredirect, input grab, VT-switch disable) at different levels of maturity, and the HMAC-signed-state module had already been hand-copied between two of them because they live in separate repos. gatelock is the one place that logic now lives.

Install

pip install "gatelock @ git+https://github.com/kuhyx/utils@gatelock-v0.1.1#subdirectory=gatelock"

Usage

import tkinter as tk
from gatelock import GateRoot, LockConfig, LockWindow

class MyGate:
    def __init__(self, *, demo_mode: bool) -> None:
        self.root = GateRoot()
        self.root.on_callback_error = self._handle_callback_error
        config = LockConfig(mode="soft" if demo_mode else "hard")
        self._lock = LockWindow(self.root, config, hooks=self)
        self._lock.setup()
        # ... build your widgets ...
        self._lock.grab_input()

    def on_focus_ready(self) -> None:
        self.my_entry.focus_force()

    def on_callback_error(self) -> None:
        self.close()

    def on_close(self) -> None:
        ...  # release any hardware/state held while locked

    def close(self) -> None:
        self._lock.close()

    def run(self) -> None:
        self._lock.run()

LockConfig's mode preset bundles the common combination ("soft" = topmost only, typeable, WM-escapable; "hard" = overrideredirect + global grab + VT-disable). Each axis (overrideredirect, grab, disable_vt, grab_retry_ms) can be set explicitly to reproduce a consumer's exact prior behavior where it diverges from the preset.

gatelock.log_integrity ports the HMAC-signed state module used by all three projects; DEFAULT_HMAC_KEY_FILE (/etc/workout-locker/hmac.key) is unchanged so existing signed history keeps verifying.

Development

python -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt
pytest
pre-commit install && pre-commit install --hook-type pre-push