Remember display layout and settings

[judokan9]

Describe the bug
I am using a three-monitor setup connected via DisplayPort daisy chaining through a docking station.
The laptop is equipped with an Intel Core i7-8550U and an Intel UHD Graphics 620, which supports up to three displays.

In order to use all three external monitors, the internal laptop display must be disabled.

After unplugging the laptop from the dock or rebooting the system, none of the display settings are preserved.
The monitor layout, orientation and scaling configuration are reset every time.
This requires manually reconfiguring the entire display setup after each reboot or reconnect.

Observed issues after reboot or undocking:

• Monitor orientation (e.g. a portrait/90° rotated monitor) is reset
• Scaling (e.g. 150%) is lost
• Primary display assignment changes
• Monitor positions are mixed up
• Disabled internal display may be re-enabled

To Reproduce
Steps to reproduce the behavior:

1. Connect the laptop to a docking station with three external monitors via DisplayPort daisy chaining
2. Open Settings → Displays
3. Disable the internal laptop display
4. Configure the external monitors:
   • Set one monitor to portrait (90° rotation)
   • Apply 150% scaling to the "primary" display
   • Arrange the monitor layout correctly
5. Reboot the system or unplug the laptop from the docking station
6. Reconnect the dock (if unplugged) and log back in
7. Everything is mixed up

Expected behavior
The display configuration (monitor layout, orientation, scaling and disabled internal display) should be persisted and automatically re-applied after rebooting or reconnecting the docking station.

Desktop (please complete the following information):

• OS: Pop!_OS 24.04 LTS
• Hardware model: Razer Blade Stealth 13 RZ09-0239x
• Memory: 16GB
• Processor: Intel Core i7-8550U
• GPU: Intel UHD Graphics 620
• System architecture: x86_64
• Kernel version: 6.17.9-76061709-generic
• Desktop environment: COSMIC
• Windowing system: Wayland

Additional context

~/.local/state/cosmic-comp/outputs.ron

(
    config: {
        [
            (
                connector: "eDP-1",
                make: "Sharp Corporation",
                model: "LQ133Z1JW26",
            ),
        ]: [
            (
                mode: ((3200, 1800), Some(59982)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (0, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
        ],
        [
            (
                connector: "DP-2",
                make: "Dell Inc.",
                model: "DELL U2723QE",
            ),
            (
                connector: "eDP-1",
                make: "Sharp Corporation",
                model: "LQ133Z1JW26",
            ),
        ]: [
            (
                mode: ((3840, 2160), Some(59997)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (1600, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((3200, 1800), Some(59982)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (0, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: true,
            ),
        ],
        [
            (
                connector: "DP-3",
                make: "Dell Inc.",
                model: "DELL U2723QE",
            ),
            (
                connector: "DP-5",
                make: "Dell Inc.",
                model: "DELL U2414H",
            ),
            (
                connector: "DP-7",
                make: "Dell Inc.",
                model: "DELL U2515H",
            ),
            (
                connector: "eDP-1",
                make: "Sharp Corporation",
                model: "LQ133Z1JW26",
            ),
        ]: [
            (
                mode: ((3840, 2160), Some(59997)),
                vrr: r#false,
                scale: 1.5,
                transform: Normal,
                position: (1080, 206),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((1920, 1080), Some(60000)),
                vrr: r#false,
                scale: 1.0,
                transform: _90,
                position: (0, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((2560, 1440), Some(59951)),
                vrr: r#false,
                scale: 1.0,
                transform: Normal,
                position: (3640, 206),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((3200, 1800), Some(59982)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (6400, 0),
                enabled: r#false,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
        ],
        [
            (
                connector: "DP-3",
                make: "Dell Inc.",
                model: "DELL U2723QE",
            ),
            (
                connector: "DP-6",
                make: "Dell Inc.",
                model: "DELL U2414H",
            ),
            (
                connector: "DP-9",
                make: "Dell Inc.",
                model: "DELL U2515H",
            ),
        ]: [
            (
                mode: ((3840, 2160), Some(59997)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (1600, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((1920, 1080), Some(60000)),
                vrr: r#false,
                scale: 1.0,
                transform: Normal,
                position: (6080, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((2560, 1440), Some(59951)),
                vrr: r#true,
                scale: 1.0,
                transform: Normal,
                position: (3520, 0),
                enabled: r#false,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
        ],
        [
            (
                connector: "DP-3",
                make: "Dell Inc.",
                model: "DELL U2723QE",
            ),
            (
                connector: "DP-6",
                make: "Dell Inc.",
                model: "DELL U2414H",
            ),
            (
                connector: "DP-9",
                make: "Dell Inc.",
                model: "DELL U2515H",
            ),
            (
                connector: "eDP-1",
                make: "Sharp Corporation",
                model: "LQ133Z1JW26",
            ),
        ]: [
            (
                mode: ((3840, 2160), Some(59997)),
                vrr: r#false,
                scale: 1.5,
                transform: Normal,
                position: (1080, 249),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((1920, 1080), Some(60000)),
                vrr: r#false,
                scale: 1.0,
                transform: _90,
                position: (0, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((2560, 1440), Some(59951)),
                vrr: r#false,
                scale: 1.0,
                transform: Normal,
                position: (3640, 249),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((3200, 1800), Some(59982)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (0, 0),
                enabled: r#false,
                max_bpc: Some(12),
                xwayland_primary: true,
            ),
        ],
        [
            (
                connector: "DP-3",
                make: "Dell Inc.",
                model: "DELL U2723QE",
            ),
            (
                connector: "eDP-1",
                make: "Sharp Corporation",
                model: "LQ133Z1JW26",
            ),
        ]: [
            (
                mode: ((3840, 2160), Some(59997)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (1600, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((3200, 1800), Some(59982)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (0, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: true,
            ),
        ],
        [
            (
                connector: "DP-3",
                make: "Dell Inc.",
                model: "DELL U2723QE",
            ),
            (
                connector: "DP-6",
                make: "Dell Inc.",
                model: "DELL U2414H",
            ),
            (
                connector: "eDP-1",
                make: "Sharp Corporation",
                model: "LQ133Z1JW26",
            ),
        ]: [
            (
                mode: ((3840, 2160), Some(59997)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (1600, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((1920, 1080), Some(60000)),
                vrr: r#false,
                scale: 1.0,
                transform: Normal,
                position: (3520, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: false,
            ),
            (
                mode: ((3200, 1800), Some(59982)),
                vrr: r#false,
                scale: 2.0,
                transform: Normal,
                position: (0, 0),
                enabled: r#true,
                max_bpc: Some(12),
                xwayland_primary: true,
            ),
        ],
    },

Maybe also related to #2777

[BiglifeMatt]

I'm not sure if this is related but I had an issue where I would open my laptop and it would sit on a grey screen with a cursor for awhile until the greeter screen appeared. Sometime not even until I restarted the greeter. However I had this happen for the first time while plugged into my multi port display dock and the side screens did come on with the greeter while the internal display was showing the grey screen with cursor. I just thought that was of interest.

[ebuc-nam]

This also happens after sleep on desktop with both displays connected to the same video card.

[codingforfun]

I hit this with a specific, reproducible root cause that might be worth
tracking separately or folding into this issue: the persisted output
profile in outputs.ron is keyed by DRM connector name + make + model, but
for docks that tunnel DisplayPort over Thunderbolt/USB4, the connector name
assigned to a given physical monitor is not stable across dock (re)connects
— even though the monitor's EDID serial number is.

Setup

• Laptop (ThinkPad, i915/Iris Xe) connected to a Lenovo ThinkPad
  Thunderbolt 5 Smart Dock 7500 (USB4).
• Two identical external monitors (both Dell Inc. DELL U2415), one of them
  physically rotated 90° into portrait and positioned to the right, the
  other landscape in the middle, laptop panel on the left.
• /sys/class/drm/ exposes a fixed pool of ~12 DP connector slots
  (DP-1..DP-12) that exist regardless of whether anything is plugged in
  (confirmed via cat /sys/class/drm/card*-DP-*/status) — connectors are not
  destroyed/recreated on hotplug, they're a static pool.

Evidence of non-deterministic connector assignment

Over time, ~/.local/state/cosmic-comp/outputs.ron accumulated 8 distinct
connector-name pairs for what is physically always the same 2 external
monitors + laptop panel:

(DP-4,  DP-5,  eDP-1)
(DP-5,  DP-7,  eDP-1)
(DP-6,  DP-7,  eDP-1)
(DP-7,  DP-9,  eDP-1)
(DP-11, DP-8,  eDP-1)
(DP-11, DP-9,  eDP-1)
(DP-11, DP-12, eDP-1)
(DP-12, DP-7,  eDP-1)

Each time the dock (re)connects, the 2 monitors can land on a different
pair of these 12 slots. Since outputs.ron's lookup key requires an exact
match on connector name (not just make/model), any pair it hasn't seen
before falls back to the default unrotated/auto-arranged layout — which
looks like "cosmic forgot my rotation and monitor order," even though the
correct profile is sitting right there in the file under a different
connector-name key.

Cold boot (with the dock already attached) reliably lands on the same
pair every time (consistent across the last 5 boots I checked), which
matches a saved profile and looks "correct" — while hot dock/undock cycles
during a running session land on effectively random pairs from the pool.
This is why a reboot "fixes" it but nothing short of a reboot does.

The monitors ARE distinguishable — just not by the key currently used

I checked the EDID of both external monitors directly
(dd if=/sys/class/drm/card1-DP-X/edid bs=128, descriptor block at offset
54, tag 0xff): they have distinct serial numbers (two different
manufacturer serial strings) despite identical make/model. The
information needed to correctly identify "which physical monitor is this,
regardless of which connector it landed on" already exists in the EDID —
outputs.ron just doesn't store or match on it.

Suggested fix

Extend the output-identity key used for persisting/matching profiles in
outputs.ron to include the EDID serial number (ProductInfo/
vendor+model+serial — smithay's Output/PhysicalProperties should
already have access to this from the EDID it parses for make/model), and
match by (make, model, serial) first, falling back to
(connector, make, model) only when a serial isn't present (some panels/
cheap monitors omit it). That alone would make saved layouts survive dock
reconnects without needing an exact connector-name match, independent of
whatever a TB4/USB4 DP-tunneling dock decides to enumerate this time.

Happy to provide the full outputs.ron history or test a patch if useful.