punktfunk/docs-site/content/docs/virtual-displays.md

title, description

title	description
Virtual displays	Control how punktfunk creates, keeps alive, and arranges the virtual displays it streams — presets, keep-alive, exclusive vs. extend, and persistent per-client scaling.

When a client connects, punktfunk creates a virtual display sized to exactly that client's resolution and refresh, renders your desktop or game onto it, and streams it. This page is about the policy for that display: how long it survives a disconnect, whether it takes over your physical monitors, what happens when a second client connects, and how desktop environments remember per-client settings like scaling.

You set this policy in the web console (Host → Virtual displays), or by editing ~/.config/punktfunk/display-settings.json directly (%ProgramData%\punktfunk\display-settings.json on Windows). A change applies to the next connection — a running session keeps the display it opened on.

You rarely need to touch this. The default behavior matches how punktfunk has always worked. Reach for a preset when you want a specific experience — a dedicated couch/gaming box, a desktop you also use in person, or a multi-monitor workstation.

What's live today: keep-alive (linger, or forever), topology (extend / primary / exclusive), conflict handling, per-client identity + persistent scaling (Windows and KDE/KWin), and multi-monitor layout (several clients as monitors of one desktop) are all enforced. A reconnect always resumes the kept display — even a fast one — instead of spawning a second. The remaining gaps are noted inline: the Linux primary physical-keep effect, Sway exclusive, and multi-display for a single client (that last is the next stage).

Pick a preset

A preset is the easy way in — select one in the console and you're done. Each expands to a bundle of the individual options documented further down.

Preset	What it's for
Default	Today's behavior. A short linger absorbs reconnects, the streamed output becomes the sole desktop, and extra clients each get their own view.
Gaming rig	A dedicated couch/headless box. The game and its display survive disconnects indefinitely (keep-alive forever), and whoever connects takes the box over. Release it from the console when you're done.
Shared desktop	A desktop you also use in person. punktfunk never blanks your real monitors and never leaves a ghost display behind; concurrent viewers each get a view.
Hot-desk	One user at a time with fast reattach — roaming between your own devices. A second user is told the box is busy, and each device+resolution keeps its own scaling.
Workstation	The multi-monitor daily driver. Your displays come back exactly where you arranged them, with per-client identity and an exclusive desktop.

Options reference

Choose Custom in the console to set these directly.

Keep alive

How long the virtual display survives after your last session disconnects. On a gamescope game host, this also keeps the game itself running so you can reconnect straight back into it.

• Off — tear the display down at session end (nothing lingers).
• A duration (seconds) — keep it for that long; a reconnect inside the window drops you straight back in, with no re-negotiation and no desktop reshuffle.
• Forever — keep it until you stop the host or release it from the console (Host → Virtual displays → Release). This is the gaming-rig model.

Default: 10 seconds. Windows has always lingered 10 s; the Linux backends previously tore down immediately — a short linger makes reconnects smoother on both.

A reconnect always resumes the kept display — the host recognises your device and hands back the same display, even if you reconnect a second or two after dropping (before it has noticed you left). Deliberately quitting (closing the client, not a network drop) tears the display down at once, skipping the linger, so you don't leave a ghost behind. How quickly a dropped client is noticed is the QUIC idle timeout — 8 s by default, tunable with PUNKTFUNK_IDLE_TIMEOUT_MS (see Legacy environment knobs) if you want kept displays freed sooner.

Keep-alive + Exclusive keeps your physical monitors dark after you disconnect, until the linger expires or you release the display. That's intentional for a dedicated gaming box, but don't set a long/forever keep-alive together with Exclusive on a machine whose monitors you also use in person — use Shared desktop there instead.

Topology

What punktfunk does with your monitor layout while it streams.

• Extend — add the virtual display alongside your real monitors; touch nothing else.
• Primary — make the virtual display your primary output; your physical monitors stay on.
• Exclusive — the virtual display becomes your only enabled output (physical monitors are disabled, then restored when streaming ends). This is what makes the streamed surface be the desktop, so panels and windows land on it.
• Automatic (default) — Exclusive on Windows and on an auto-detected KDE/GNOME desktop ("stream this desktop" means the streamed output is the desktop); Extend when you've pinned a specific compositor with PUNKTFUNK_COMPOSITOR (a test/CI posture).

Per-backend support:

	KWin	Mutter/GNOME	Sway/wlroots	Windows
Extend	✅	✅	✅	✅
Primary	✅	✅	⚠️ treated as Extend	✅
Exclusive	✅	✅	⏳ following release	✅

Conflict handling · identity · layout

• Conflict handling — what happens when a different client connects while one is already streaming and asks for a different resolution: give it its own display (separate), take the box over (steal), share the existing display at its current mode (join), or refuse it (reject). On Linux, separate gives each client its own display on the shared desktop. On Windows a second client is rejected (a clean "host busy") even under separate — two clients can't yet share one virtual display's capture there (that's a later stage), so the live session is protected instead. A same-client reconnect never conflicts — it resumes.
• Identity — whether each client gets a stable display identity so your desktop environment remembers its settings (see Persistent scaling): one shared identity, one per client, or one per client + resolution.
• Layout / max displays — when several clients each become a monitor of one desktop, this places them side by side (auto) or exactly where you arrange them in the console (manual, keyed to each client), up to max displays. Arrange them under Host → Virtual displays once two or more are streaming.

Persistent scaling

Set your display scaling once and have it stick across reconnects. This works by giving each client a stable display identity, so your desktop environment keys its per-monitor settings to it.

Host	Supported	How
Windows	✅ today	Connect, set scaling in Settings while streaming — Windows remembers it per client.
KDE / KWin	✅ today	Set scaling in System Settings while streaming; KWin keys it to a stable per-client output name and reapplies it on reconnect. Validated live (150 %/125 % survive a full disconnect + reconnect).
GNOME / Mutter	❌	GNOME's virtual-monitor API exposes no stable identity to key config on.
Sway / wlroots	❌	Headless outputs can't carry a stable identity; pin scale in your sway config instead.

Legacy environment knobs

These PUNKTFUNK_* variables still work, but the console (and display-settings.json) supersede them — when a settings file exists, it wins.

Legacy knob	Now expressed as
PUNKTFUNK_MONITOR_LINGER_MS	Keep alive → duration (Windows)
PUNKTFUNK_NO_ISOLATE	Topology → Extend (Windows)
PUNKTFUNK_KWIN_VIRTUAL_PRIMARY / PUNKTFUNK_MUTTER_VIRTUAL_PRIMARY	Topology → Exclusive (when set) / Extend (when 0)

One knob has no console equivalent — it's a transport tuning, not display policy:

• PUNKTFUNK_IDLE_TIMEOUT_MS (host, default 8000) — how long the host waits before declaring a dropped client gone, which is when a kept display starts its linger (or is freed). Lower it (e.g. 3000) to reclaim kept displays sooner after an ungraceful drop; it's clamped to ≥1 s and its keep-alive ping scales with it, so a live session never false-disconnects. A deliberate quit is instant regardless. Also --idle-timeout-ms on punktfunk1-host.

Troubleshooting

My physical monitors stayed off after I disconnected. You have keep-alive set together with Exclusive topology — the display (and your isolated desktop) is being kept for the linger window. Release it from the console (Host → Virtual displays), or switch to the Shared desktop preset so streaming never disables your real monitors.

The virtual output shows only my wallpaper. Your topology is Extend, so the streamed display is an empty extension. Use Primary or Exclusive so your desktop actually lands on it.

KWin virtual outputs need KWin ≥ 6.5.6. Older KWin can't create the virtual output at all — see requirements.