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fix(host/windows): keep multi-display (Apollo parity) instead of sole-display isolation

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CONFIRMED on the live RTX4090+iGPU box: hook fires+verified, DPI=2, overlay
running, yet the stream STILL freezes -- born-lost dropped but MODE_CHANGE_IN_
PROGRESS (0x887A0025) churn took over (2284x) and frames go stale. Root cause
is the topology itself: create() makes SudoVDA the SOLE active display
(CDS_SET_PRIMARY + isolate_displays + isolate_displays_ccd), and a sole display
on a hybrid box goes into fullscreen independent-flip / MPO that Desktop
Duplication cannot capture.

Apollo is rock solid on this EXACT box because it does the opposite: it keeps
the physical monitor ACTIVE and arranges the virtual display alongside it
(rearrangeVirtualDisplayForLowerRight, 'Do not change the primary'). Multi-
display is DWM-composited, so the output never independent-flips.

Make isolation OPT-IN (PUNKTFUNK_ISOLATE_DISPLAYS=1) and default to NOT
isolating -- match Apollo's multi-display topology. SudoVDA stays primary (so
it carries the shell -> frames) but other monitors stay active, which disables
independent-flip. reassert_isolation honors the same flag (re-isolating mid-
stream would itself trigger the storm). Keeps the overlay + born-lost escape
as belt-and-suspenders.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-16 14:23:20 +00:00
parent 5f84c5785c
commit cd72164db2
1 changed files with 25 additions and 5 deletions
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crates/punktfunk-host/src/vdisplay/sudovda.rs
+25 -5
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@@ -564,6 +564,11 @@ unsafe fn restore_displays_ccd(saved: &SavedConfig) {
/// nothing besides `gdi_name` is attached, [`isolate_displays`] finds nothing to detach and commits
/// nothing — so this is safe to call on every throttled recovery tick (no display thrash).
pub(crate) fn reassert_isolation(gdi_name: &str) {
// Only when sole-display isolation is explicitly opted into (see create()): otherwise re-isolating
// would itself trigger the independent-flip storm we're avoiding.
if std::env::var("PUNKTFUNK_ISOLATE_DISPLAYS").is_err() {
return;
}
unsafe {
let _ = isolate_displays(gdi_name);
}
@@ -745,11 +750,26 @@ impl VirtualDisplay for SudoVdaDisplay {
tracing::info!("SudoVDA target {} -> {n}", ao.target_id);
// ADD only advertises the mode; force it active so DXGI captures the requested size.
set_active_mode(n, mode);
// Detach every other display so the secure desktop (Winlogon/UAC) renders here too.
// CCD isolation is the one that works on a hybrid box (the legacy GDI enum misses the
// iGPU-attached monitor); the legacy pass stays as a no-op fallback.
isolated = unsafe { isolate_displays(n) };
ccd_saved = unsafe { isolate_displays_ccd(ao.target_id) };
// Display isolation (detach all other monitors → SudoVDA becomes the SOLE display) is
// OPT-IN now. On a hybrid GPU box a SOLE active display goes into fullscreen
// independent-flip / MPO, which Desktop Duplication CANNOT capture → the born-lost
// ACCESS_LOST + MODE_CHANGE_IN_PROGRESS storm measured live on the RTX4090+iGPU box
// (hook verified-firing, DPI=2, overlay running — yet still frozen). Apollo stays rock
// solid on this exact box precisely because it KEEPS the physical monitor active and just
// arranges the virtual display alongside it (multi-display is DWM-composited, so the
// output never independent-flips). So default to NOT isolating — match Apollo's topology.
// Set PUNKTFUNK_ISOLATE_DISPLAYS=1 to force the old sole-display behaviour (a truly
// headless box with no attached monitor, where the secure/Winlogon desktop would
// otherwise render on a detached physical output).
if std::env::var("PUNKTFUNK_ISOLATE_DISPLAYS").is_ok() {
isolated = unsafe { isolate_displays(n) };
ccd_saved = unsafe { isolate_displays_ccd(ao.target_id) };
} else {
tracing::info!(
"display isolation SKIPPED (Apollo-parity multi-display — avoids sole-display \
independent-flip; set PUNKTFUNK_ISOLATE_DISPLAYS=1 to force sole-display)"
);
}
thread::sleep(Duration::from_millis(1500)); // let the topology settle before capture opens
}
None => tracing::warn!(