174 lines
6.8 KiB
Markdown
174 lines
6.8 KiB
Markdown
# Hyprland HDMI Revive
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Recover a black HDMI display after switching a shared physical monitor away from
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an Arch Linux / Hyprland workstation and back. A DRM hotplug event triggers a
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short switch away from the active graphical VT and back. There is no periodic
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DPMS toggle or polling timer.
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**Version 0.2.0.** The initial implementation and the review fixes are separate
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commits. See [the code review](docs/code-review.md) and [changelog](CHANGELOG.md).
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## Requirements
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A systemd-based Linux desktop with Hyprland, a local `seat0` Wayland session,
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Bash, coreutils (`timeout`, `stdbuf`, `stat`), `jq`, `flock`, `sudo` and
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`/usr/bin/chvt`. On Arch Linux:
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```bash
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sudo pacman -S --needed hyprland systemd bash coreutils jq util-linux kbd sudo
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```
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The intended setup is one local Hyprland session per user. The monitor must emit
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DRM `HOTPLUG=1` events when its physical input changes. No event means no automatic
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recovery. Hyprland must still expose the configured monitor over its IPC socket.
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## Install from the package
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Download `hyprland-hdmi-revive-0.2.0.tar.gz` and `SHA256SUMS` from the
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[Gitea release](https://gitea.jr-it-services.de/johannes/hyprland-hdmi-revive/releases).
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Run as your desktop user, **without sudo**:
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```bash
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sha256sum --ignore-missing -c SHA256SUMS
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tar -xzf hyprland-hdmi-revive-0.2.0.tar.gz
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cd hyprland-hdmi-revive-0.2.0
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./scripts/install.sh
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```
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This is a portable user installer bundle, not a pacman system package. It installs:
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- executables under `~/.local/bin/`;
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- shared code under `~/.local/lib/hyprland-hdmi-revive/`;
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- the unit under `${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user/`;
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- a new config under `${XDG_CONFIG_HOME:-$HOME/.config}/revive-monitor/config.env`.
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Existing configuration is preserved. A running instance is stopped before its
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files are replaced. Installation alone does not enable or start the service.
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Alternatively, clone the source and use the same installer:
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```bash
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git clone https://gitea.jr-it-services.de/johannes/hyprland-hdmi-revive.git
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cd hyprland-hdmi-revive
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./scripts/install.sh
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```
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## Configure
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Find the monitor name from a terminal inside Hyprland:
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```bash
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hyprctl monitors
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nano "${XDG_CONFIG_HOME:-$HOME/.config}/revive-monitor/config.env"
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```
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Example:
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```bash
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MONITOR=HDMI-A-2
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DEBOUNCE_SECONDS=30
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HDMI_SETTLE_SECONDS=5
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VT_SWITCH_DELAY_SECONDS=1
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VT_RETURN_SETTLE_SECONDS=2
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```
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Timing values are whole seconds: 0–300 for waits and 0–3600 for debounce. Config is
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trusted Bash sourced as your user; do not copy untrusted shell code into it.
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### Allow the VT switch
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Edit with `sudo visudo -f /etc/sudoers.d/revive-monitor-chvt`. Prefer explicit VT
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arguments when the machine always uses VT1 and VT2:
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```sudoers
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YOUR_USER ALL=(root) NOPASSWD: /usr/bin/chvt 1, /usr/bin/chvt 2
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```
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Replace `YOUR_USER`. For changing graphical VTs, a broader chvt-only rule is in
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`sudoers/revive-monitor-chvt.example`. Never grant sudo access to these scripts.
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The helper checks permission for both directions before leaving the desktop and
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uses `sudo -n` with command timeouts. A return failure gets one emergency retry.
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### Connect the Hyprland session
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The user service manager does not automatically inherit a terminal's Hyprland
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environment. Add this line to your Hyprland configuration (commonly
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`~/.config/hypr/hyprland.conf`):
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```ini
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exec-once = sh -c 'export XDG_CONFIG_HOME="${XDG_CONFIG_HOME:-$HOME/.config}"; systemctl --user import-environment HYPRLAND_INSTANCE_SIGNATURE XDG_CONFIG_HOME && systemctl --user restart revive-monitor-drm-watch.service'
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```
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It imports the current IPC instance at each Hyprland login, including after
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logging out and back in. A custom `XDG_CONFIG_HOME` must also be consistent with
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the user manager's unit search path. See the official
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[hyprctl documentation](https://wiki.hypr.land/configuring/core/advanced-configuration/using-hyprctl/)
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and [systemd environment documentation](https://www.freedesktop.org/software/systemd/man/latest/environment.d.html).
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For the current login, after configuring the output and sudoers:
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```bash
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./scripts/install.sh --start
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systemctl --user status revive-monitor-drm-watch.service
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journalctl --user -u revive-monitor-drm-watch.service -b
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```
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`--start` imports the current instance, reloads systemd, enables and restarts the
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unit. Use it for updates as well. The service remains attached to `default.target`
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because not every Hyprland setup activates `graphical-session.target`; session
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and IPC guards prevent pre-login VT switching.
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## Behavior and limits
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- Events are accepted only for this UID's active local Wayland session on seat0.
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A reported non-Hyprland desktop is excluded.
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- The helper independently verifies the requested VT and rechecks the session
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after settling and permission checks.
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- A private `XDG_RUNTIME_DIR` is required. Locks prevent duplicate watchers and
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overlapping recoveries; there is no shared `/tmp` fallback.
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- Missing IPC, invalid monitor names, command failures and lost event streams
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produce error logs. A terminated event stream causes systemd to restart the watcher.
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- Signals trigger a best-effort return to the graphical VT. SIGKILL, power loss
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and persistent sudo/kernel failures cannot be recovered by a shell trap.
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- DRM events are not reliably attributed to a particular monitor. Another
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output's hotplug can trigger this workaround too.
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- Debounce is a cooldown measured after a recovery attempt. It suppresses queued
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events, including events caused by the VT switch. It can also suppress a real
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rapid input return; if that happens, try a shorter `DEBOUNCE_SECONDS` or run
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the helper manually with the correct graphical VT.
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## Uninstall
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From the unpacked bundle or checkout:
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```bash
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./scripts/uninstall.sh
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```
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The user manager must be reachable. Config and sudoers remain intact. Remove the
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Hyprland startup line and, if no longer needed, the dedicated sudoers entry with
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`visudo`. Failure state for unrelated services is preserved.
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## Build and validate
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Python 3 is needed only for tests; ShellCheck is a development dependency.
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```bash
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for script in scripts/*.sh lib/*.sh; do bash -n "$script" || exit; done
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shellcheck -x scripts/*.sh lib/*.sh
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python3 -B -m unittest discover -s tests -v
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./scripts/build-release.sh
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```
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The release builder requires clean tracked files and packages **committed HEAD**.
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It creates a `.tar.gz` installer bundle, source ZIP, Base64 ZIP and `SHA256SUMS` in
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`dist/`. Untracked files and local config are excluded. The Base64 ZIP can also
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be decoded on Windows with `certutil -decode <file.zip.b64> <file.zip>`.
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Tests mock loginctl, Hyprland IPC, udev, sudo and systemd. They never switch the
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real display. A hardware input-switch test after installation remains necessary.
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CI runs the shell checks and behavioral tests on a configured Gitea Actions runner.
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See [architecture](docs/architecture.md), [troubleshooting](docs/troubleshooting.md)
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and [security notes](SECURITY.md). MIT license: [LICENSE](LICENSE).
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