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feat(vdisplay/kwin): group-aware exclusive — never disable a sibling output (Stage 5 §6.1)

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The critical latent bug Stage 3 introduced: per-slot output names mean a 2nd
exclusive session's other_enabled_outputs() (which disabled 'everything not named
Virtual-punktfunk') would black out the 1st session's Virtual-punktfunk-<id>
output. Fix: recognise the whole managed group by the shared Virtual-punktfunk
prefix — exclusive now disables only NON-managed outputs (bootstrap/physical),
never a group sibling. Plus first-slot-wins for the group primary
(a_managed_output_is_primary): a later session joins as a secondary monitor of the
shared desktop instead of stealing the shell off the first. Unit-tested.

Start of Stage 5 (§6A many-clients-one-desktop). Remaining: Mutter/wlroots
group-aware analogues, layout (auto-row/manual + /display/layout + console),
per-group topology restore, gamescope groups.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-07-05 11:44:41 +00:00
parent 23446fa177
commit eddcd91f48
2 changed files with 164 additions and 32 deletions
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crates/punktfunk-host/src/vdisplay/linux/kwin.rs
+84 -22
View File
@@ -242,11 +242,17 @@ fn read_active_refresh(output: &str) -> Option<u32> {
Some(hz.round() as u32)
}
/// Names of currently-ENABLED outputs other than our `Virtual-punktfunk` — i.e. the headless
/// session's bootstrap output(s), which hold the desktop by default. Parsed from `kscreen-doctor -j`
/// (same source as [`read_active_refresh`]).
fn other_enabled_outputs(name: &str) -> Vec<String> {
let ours = format!("Virtual-{name}");
/// The prefix EVERY managed KWin output shares — Stage 3 names them `punktfunk` / `punktfunk-<id>`,
/// which KWin exposes as `Virtual-punktfunk` / `Virtual-punktfunk-<id>`. Group membership (§6.1) is
/// recognised by this prefix, so we never have to thread the live set through the backend.
const MANAGED_PREFIX: &str = "Virtual-punktfunk";
/// Names of currently-ENABLED outputs that are **not managed by us** — the headless session's
/// bootstrap output(s) + any physical monitor, i.e. exactly what `exclusive` must disable.
/// **Group-aware (§6.1):** excludes the WHOLE managed family (the [`MANAGED_PREFIX`]), not just this
/// session's own output — so a 2nd `exclusive` session (with a distinct per-slot name) never disables
/// the 1st session's live output. Parsed from `kscreen-doctor -j` (same source as [`read_active_refresh`]).
fn other_enabled_outputs() -> Vec<String> {
let out = match std::process::Command::new("kscreen-doctor")
.arg("-j")
.output()
@@ -262,19 +268,46 @@ fn other_enabled_outputs(name: &str) -> Vec<String> {
.and_then(|o| o.as_array())
.map(|outs| {
outs.iter()
.filter(|o| {
o.get("enabled").and_then(|e| e.as_bool()).unwrap_or(false)
&& o.get("name").and_then(|n| n.as_str()) != Some(ours.as_str())
})
.filter_map(|o| o.get("name").and_then(|n| n.as_str()).map(String::from))
.filter(|o| o.get("enabled").and_then(|e| e.as_bool()).unwrap_or(false))
.filter_map(|o| o.get("name").and_then(|n| n.as_str()))
.filter(|n| !n.starts_with(MANAGED_PREFIX))
.map(String::from)
.collect()
})
.unwrap_or_default()
}
/// Set `Virtual-punktfunk` primary and disable the bootstrap output(s) so it becomes the sole
/// desktop (KWin re-homes plasmashell + windows onto it). Returns the disabled outputs for the
/// keepalive to re-enable on teardown. Best-effort: on failure, streaming continues (just possibly
/// True if any managed group member (the [`MANAGED_PREFIX`] family) is ALREADY the KWin primary —
/// first-slot-wins support (§6.1) so a later exclusive session doesn't steal primary from the group's
/// first member. Best-effort: if kscreen reports no primary flag we treat it as "none" (the session
/// then sets itself primary — the pre-group behavior). Recent kscreen marks the primary with
/// `"priority": 1`; older builds used a `"primary": true` bool — accept either.
fn a_managed_output_is_primary() -> bool {
let Ok(out) = std::process::Command::new("kscreen-doctor").arg("-j").output() else {
return false;
};
let Ok(doc) = serde_json::from_slice::<serde_json::Value>(&out.stdout) else {
return false;
};
doc.get("outputs")
.and_then(|o| o.as_array())
.map(|outs| {
outs.iter().any(|o| {
let managed = o
.get("name")
.and_then(|n| n.as_str())
.is_some_and(|n| n.starts_with(MANAGED_PREFIX));
let primary = o.get("primary").and_then(|p| p.as_bool()).unwrap_or(false)
|| o.get("priority").and_then(|p| p.as_u64()) == Some(1);
managed && primary
})
})
.unwrap_or(false)
}
/// Set `Virtual-punktfunk` primary and disable the bootstrap output(s) so the managed group becomes
/// the sole desktop (KWin re-homes plasmashell + windows onto it). Returns the disabled outputs for
/// the keepalive to re-enable on teardown. Best-effort: on failure, streaming continues (just possibly
/// showing only the wallpaper) rather than failing the session.
fn apply_virtual_primary(name: &str) -> Vec<String> {
let ours = format!("Virtual-{name}");
@@ -285,16 +318,21 @@ fn apply_virtual_primary(name: &str) -> Vec<String> {
.map(|s| s.success())
.unwrap_or(false)
};
// Make ours primary — KWin usually then re-homes the desktop and disables the bootstrap on its
// own. Let that settle, then belt-and-suspenders: disable anything still enabled besides ours so
// the streamed output is unambiguously the sole desktop regardless of KWin's implicit behaviour.
if !kscreen(&[format!("output.{ours}.primary")]) {
tracing::warn!(
"KWin: could not set the virtual output primary; client may see only the wallpaper"
);
// First-slot-wins (§6.1): only grab primary if no managed group member is primary yet — so a 2nd
// exclusive session joins as a secondary monitor of the shared desktop instead of stealing the
// shell off the 1st session's output. KWin usually then re-homes the desktop + disables the
// bootstrap on its own; the belt-and-suspenders disable below covers the rest.
if !a_managed_output_is_primary() {
if !kscreen(&[format!("output.{ours}.primary")]) {
tracing::warn!(
"KWin: could not set the virtual output primary; client may see only the wallpaper"
);
}
std::thread::sleep(Duration::from_millis(200));
}
std::thread::sleep(Duration::from_millis(200));
let others = other_enabled_outputs(name);
// Disable everything still enabled that ISN'T a managed group member (bootstrap / physical), so
// the group is unambiguously the desktop — never a sibling session's output (group-aware filter).
let others = other_enabled_outputs();
if !others.is_empty() {
let args: Vec<String> = others
.iter()
@@ -555,3 +593,27 @@ fn run(
let _ = conn.flush();
Ok(())
}
#[cfg(test)]
mod tests {
use super::MANAGED_PREFIX;
/// Group-aware exclusive (§6.1): with two managed group members + a physical panel enabled,
/// exclusive disables ONLY the non-managed panel — never a sibling session's per-slot output
/// (the Stage-3 naming would otherwise make a 2nd exclusive session black out the 1st).
#[test]
fn exclusive_disables_only_non_managed() {
let enabled = [
"Virtual-punktfunk", // base name (shared identity)
"Virtual-punktfunk-1", // client A's per-slot output
"Virtual-punktfunk-7", // client B's per-slot output
"eDP-1", // a physical panel
];
let to_disable: Vec<&str> = enabled
.iter()
.copied()
.filter(|n| !n.starts_with(MANAGED_PREFIX))
.collect();
assert_eq!(to_disable, vec!["eDP-1"]);
}
}