feat(display): persist monitor settings to compositor config on confirm

[pir0c0pter0]

Summary

PR #2330 adds excellent display configuration management (scale, mode, refresh rate, VRR, transform, position) but changes are only applied at runtime via compositor IPC commands (niri msg, hyprctl, swaymsg). Settings are lost on logout/reboot since they are never written to the compositor's config file.

Current behavior

1. User changes scale/mode/VRR in Settings > Display > Monitor
2. Changes are applied via runtime commands (e.g. niri msg output eDP-1 scale 1.5)
3. Confirmation dialog appears → user clicks "Keep"
4. On reboot, compositor loads its config file with the old values → settings lost

Expected behavior

When the user confirms display changes ("Keep"), the settings should be persisted to the compositor's config file so they survive reboot.

Suggested approach

On confirmChange(), write the confirmed targetConfig to the compositor's config:

• Niri: generate output blocks in ~/.config/niri/config.kdl (or modular cfg/display.kdl if present)
• Hyprland: update monitor lines in hyprland.conf
• Sway: update output lines in sway config

A reference implementation for niri using a Python helper script is available — happy to open a PR if there's interest.

Environment

• Noctalia Shell: v4.7.1 + PR feat(display): add display configuration management #2330
• Compositor: niri
• OS: CachyOS (Arch-based)

[pir0c0pter0]

Workaround

While waiting for official persistence in #2330, here's a working workaround using a Python helper script called from DisplayService.confirmChange().

1. Add Scripts/persist-display.py

#!/usr/bin/env python3
"""Persist niri display configuration to config.kdl on confirm."""
import sys, json, os, re

def main():
    payload = json.loads(sys.argv[1])
    config_dir = os.path.expanduser("~/.config/niri")
    display_kdl = os.path.join(config_dir, "cfg", "display.kdl")
    main_kdl = os.path.join(config_dir, "config.kdl")
    target_file = display_kdl if os.path.isfile(display_kdl) else main_kdl

    with open(target_file, "r") as f:
        content = f.read()

    transform_map = {
        "Normal": "normal", "90": "rotation 90", "180": "rotation 180",
        "270": "rotation 270", "Flipped": "flipped", "Flipped90": "flipped-rotation 90",
        "Flipped180": "flipped-rotation 180", "Flipped270": "flipped-rotation 270",
    }

    content = re.sub(r"\n?/?-?\s*output\s+\"[^\"]+\"\s*\{[^}]*\}", "", content)
    content = content.rstrip() + "\n"

    for name, cfg in payload.items():
        if not cfg.get("enabled", True):
            content += f'\noutput "{name}" {{\n    off\n}}\n'
            continue
        lines = [f'output "{name}" {{']
        mode = cfg.get("modeStr", "")
        if mode:
            lines.append(f'    mode "{mode}"')
        scale = cfg.get("scale", 1.0)
        if scale != 1.0:
            s = int(scale) if scale == int(scale) else scale
            lines.append(f"    scale {s}")
        t = transform_map.get(cfg.get("transform", "Normal"), "")
        if t and t != "normal":
            lines.append(f"    transform {{ {t} }}")
        if cfg.get("vrr_enabled", False):
            lines.append("    variable-refresh-rate")
        px, py = cfg.get("position_x", 0), cfg.get("position_y", 0)
        if px != 0 or py != 0:
            lines.append(f"    position x={px} y={py}")
        lines.append("}")
        content += "\n" + "\n".join(lines) + "\n"

    with open(target_file, "w") as f:
        f.write(content)

if __name__ == "__main__":
    main()

2. Patch DisplayService.confirmChange()

function confirmChange() {
    root.awaitingConfirmation = false;
    root.pendingRevert = null;
    root.revertCountdown = 0;
    _persistCurrentConfig();
}

function _persistCurrentConfig() {
    const hint = _getDisplayBackendHint();
    if (hint !== "niri") return;

    const payload = {};
    for (const name in root.targetConfig) {
        const cfg = root.targetConfig[name];
        if (!cfg) continue;
        payload[name] = {
            enabled: cfg.enabled !== false,
            scale: cfg.scale || 1.0,
            modeStr: cfg.modeStr || "",
            transform: cfg.transform || "Normal",
            vrr_enabled: cfg.vrr_enabled || false,
            position_x: cfg.x !== undefined ? Math.round(cfg.x) : 0,
            position_y: cfg.y !== undefined ? Math.round(cfg.y) : 0
        };
    }

    const scriptPath = Quickshell.shellRoot + "/Scripts/persist-display.py";
    Quickshell.execDetached(["python3", scriptPath, JSON.stringify(payload)]);
}

Tested on CachyOS + niri. Persists scale, mode, VRR, transform, and position. Supports both modular (cfg/display.kdl) and single-file (config.kdl) niri configs.

Note: I see @maxinglo already has a persistence branch — this is just an interim workaround for anyone running the PR as-is.

[turannul]

The problem doing that may or may not work on everyone, no doubt this is intended way to do it.
In detail: my niri config has separate outputs.kdl for someone that would be displays.kdl and that is only English part... but you get the problem

@pir0c0pter0 That's why i didn't suggested anything about this one