command-center/omp-docs/tools/niri/displays.md

---
type: reference
title: Display Configuration
description: Niri output configuration on blankpad — EDID-identity-keyed desk profiles, hotplug auto-switching, portrait transforms, position pinning, the phantom-mode fallback trap, and GPU notes (AMD Cezanne now; Intel Arc render-node pin is dankware-legacy).
tags:
  - niri
  - display
  - monitors
  - rotation
  - desk-profiles
verified: 2026-10-21
---

# Display Configuration

Niri output config on **blankpad** is a **desk-profile system**: the laptop
travels between desks, connector names (`DP-2`, `HDMI-A-1`) reshuffle per
dock, so panels are configured by **EDID identity** (manufacturer model
serial), and *positions* live in per-desk files. A hotplug watcher and a
manual picker keep the live layout matched to reality.

**Mechanism:** `~/.config/niri/cfg/display.kdl` is a **symlink** to the
active profile (`desk-1-home.kdl`, `desk-2-portable.kdl`, …).
`config.kdl` includes it with `include optional=true` so a missing link is a
warning, not a parse failure.
**Probe:** `niri msg outputs` is authoritative (connector, full EDID long
name, modes, transform, scale, position, VRR). Per-output changes go live with
`niri msg output <name> <mode|scale|transform|position|off|on>` and are
temporary — never written to the config file. `wlr-randr` is **not installed**
on blankpad (`pacman -Qs wlr` matches nothing, verified 2026-10-21); pages that
list it as an installed tool are stale.

---

## The desk-1 rig (home)

```
┌──────────────┬──────────────────────────────┬──────────┐
│  PM1601      │   Sceptre M34 ultrawide      │  eDP-1   │
│  portrait    │   3440x1440 @ 180.000        │ 1920x1080│
│  1200x1920   │   landscape, scale 1         │ scale 1  │
│  rot 90      │   position 1581,-600         │ 5021,-240│
└──────────────┴──────────────────────────────┴──────────┘
  HDMI-A-1            DP-1 (focus-at-startup)     eDP-1 (fallback focus)
Connector names are today's (`niri msg outputs`, 2026-10-21). They reshuffle with
the dock and the cable, which is why the config keys on the EDID long name instead.
```

| Panel | EDID long name | Keyed by | Notes |
|-------|----------------|----------|-------|
| Sceptre M34 ultrawide | `Sceptre Tech Inc Sceptre M34 Unknown` | identity | `mode "3440x1440@180.000"`, **deliberate** — the panel also offers `3440x1440@239.998`, `144.001` and `120.000`; 180 is driven while the link is degraded (see the law below) — `focus-at-startup` |
| PM1601 portrait | *not captured* | connector `HDMI-A-1` | dock-dependent; run `desk.sh capture` when plugged in, then re-key |
| eDP-1 laptop panel | `Lenovo Group Limited 0x40A9 Unknown` | identity | scale **1.0** (deliberate; Ghostty grid at 1.25 rejected 2026-10-09), second `focus-at-startup` |

VRR: the M34 supports it (its connector today is `DP-1`); **left disabled by
decision** (2026-10-09). Add `variable-refresh-rate` per output if that ever changes.

`focus-at-startup` on both M34 and eDP-1: niri focuses in config order, so
the ultrawide wins when present and the laptop panel is the fallback.

## Desk switching

```mermaid
graph LR
    P[plug / unplug] --> E[niri event-stream<br/>WorkspacesChanged → output-set diff]
    E --> M[desk-autoswitch.sh<br/>debounced matcher]
    M --> R{profile requires<br/>subset of connected?}
    R -->|best match| A[desk.sh apply:<br/>validate - relink - reload - notify]
    R -->|none| K[keep current + notify]
    D[Mod+Shift+D] --> C[desk.sh cycle] --> A
```

- **Matcher:** each profile declares `// requires: <long name>` (all must be
  connected) and `// optional:` comment lines; the most-specific eligible
  profile wins.
- **Apply order is load-config-safe:** `niri validate` the *current* config
  first, relink `display.kdl`, then `niri msg action load-config-file`,
  then a noctalia notification names the active desk. A profile that fails
  validation can never go live.
- **Manual override:** `Mod+Shift+D` cycles profiles (wrong auto-pick, or
  same panels, new layout).
- **New desk:** `desk.sh capture` prints connected long names → copy into a
  new `desk-N-<name>.kdl` (see `desk-2-portable.kdl` skeleton, portable
  monitor EDID pending first capture).
- Unit: `blankpad-desk-autoswitch.service` (systemd user,
  `ConditionHost=blankpad`).

## The config pattern

```kdl
// desk-1-home.kdl — one block per panel, keyed by identity
output "Sceptre Tech Inc Sceptre M34 Unknown" {
    mode "3440x1440@180.000"
    scale 1
    transform "normal"
    position x=1581 y=-600
    focus-at-startup
}
```

Four rules learned the hard way:

1. **One output, one block.** Two blocks matching the same output (connector
   name *and* long name) fight over properties — transform reverts are the
   classic symptom. Desk profiles are self-contained: a panel's identity,
   mode, transform, **and** position live in exactly one block per file.
   `desk-1-home.kdl` still carries legacy connector-keyed `DP-1` / `DP-2`
   blocks next to the identity block. Their modes were aligned to 180 Hz on
   2026-10-21 so a connector-named reconnect cannot drop the panel to 120, but
   they belong folded into the identity block.
2. **Key by EDID identity, not connector.** Connector names swap between
   docks; the EDID long name travels with the panel. Serials on these panels
   read `Unknown`, so the full long name (manufacturer model serial) is the
   match string — copy it verbatim from `niri msg outputs`.
3. **Positions are absolute, not relational.** A disconnected panel leaves
   a hole; that is exactly why positions belong to the *desk profile*, not a
   global file.
4. **Ask only for modes the panel reports, and copy the string exactly.** The M34's
   `Available modes` (`niri msg outputs`, 2026-10-21) are `3440x1440@239.998`,
   `3440x1440@180.000`, `144.001`, `120.000`, … with `59.998` marked preferred. niri
   matches mode strings **verbatim** and does not round, so `239.999` — one digit from
   the real mode, which is what this file and the config both carried for weeks — is not
   `239.998`. A mode it cannot find does **not** leave the output dark: niri logs
   `configured mode … could not be found, falling back to preferred` and quietly drives
   the panel at its EDID *preferred* mode — **60 Hz**. Nothing looks broken except the
   refresh rate, and every reconnect repeats the fallback. Check Hz, not just
   resolution, after any "monitor is acting up".
5. **180 Hz here is a decision, not a ceiling.** The panel offers 239.998 and is driven
   at 180.000 deliberately: the link trained at `x8 32.0 GT/s` against a max of `x16`,
   and the display engine is throwing `DMCUB` errors with `EINVAL` page flips after
   s2idle, so the 240-class mode is not driven until a reboot clears that state. Before
   changing the mode, re-read `niri msg outputs` **and** the link sysfs; treat "restore
   240" as a change to verify on a healthy link, never as the obvious fix. Refs #60.

## "The monitors are broken" — three layers, three signatures

A display complaint belongs to one of three layers. Sort it before editing
config, because the config is usually innocent — and when it is guilty, the
guilt may have been copied from this page.

| Layer | Log signature | Reality | Move |
|-------|---------------|---------|------|
| Config | `configured mode … could not be found, falling back to preferred` | a mode/scale the panel never offered | re-read the mode list with `niri msg outputs` and correct the file; do **not** trust a documented mode |
| Link | `disconnecting connector: "DP-1"` followed seconds later by `new connector: DP-1`, recurring | the DP link itself dropping — cable, dock, the monitor's DP-version/DSC setting, or panel power saving | every drop re-runs mode selection, so a config error is re-enacted in public; swap the cable before blaming the compositor |
| Driver | `Page flip commit failed … (Invalid argument)` plus kernel `*ERROR* … DMCUB error` | amdgpu's display engine wedged, typically after an s2idle resume | survives until a reboot; niri keeps running while the panel keeps dropping. No config edit clears it |

Probes, in this order:

```bash
niri msg outputs                    # connector, EDID long name, real mode list, current mode
journalctl --user -b | grep -E 'disconnecting connector|Page flip commit failed|falling back to preferred'
journalctl -k -b  | grep -iE 'amdgpu.*(ERROR|DMCUB)|PM: suspend exit'
```

Correlate the drop timestamps against `PM: suspend exit` first. A resume a
minute before the first drop is the cause; the config file is not.

To fix a refresh rate without disturbing the session, use the temporary
per-output path — it touches one output, applies no config, reloads nothing:

```bash
niri msg output "Sceptre Tech Inc Sceptre M34 Unknown" mode "3440x1440@180.000"
```

It is temporary by design, so correct the profile too and let the next
reconnect or `load-config-file` make it permanent. With the display engine
already throwing `EINVAL`, prefer the per-output path over a full config
reload; on a healthy machine either is fine.

## GPU assignment

blankpad is a **single AMD Cezanne iGPU** (`/dev/dri/renderD128`, PCI
`07:00.0`). No render-node pin exists in `misc.kdl` — and must not: the
blankpad override file deliberately deletes the pin.

The `environment { render-node "/dev/dri/renderD129" }` pin found in the
*base* `misc.kdl` is **dankware-legacy** (Intel Arc iGPU + discrete GPU
hybrid; pin kept the iGPU as display owner and sidesteps the suspend/resume
deadlock documented in the sleep-wake investigation). Deploying that base
file on blankpad pins a render node that does not exist — this is why
blankpad runs the `zz-blankpad` override layer (see [[index|the per-host
symlink matrix]]).

## Reload

`niri msg action load-config-file` reloads live. Never `SIGHUP` the process
— see [[tips]].

## See Also

- [Niri](/tools/niri/index.md) — compositor overview and config layout
- [[tips|tips]] — reload path, `niri msg layers/casts`, includes
- [[noctalia-shell|noctalia-shell]] — notification shown on desk switch
- [[cachyos|cachyos]] — operating system