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fix(host/windows): force-composed-flip overlay in the single-process DDA path

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CONFIRMED root cause via instrumented build: hook_hits=1+ (win32u hook fires,
verified-patched) and DPI awareness=2 (PER_MONITOR), yet the born-lost
ACCESS_LOST storm persists with 100% DuplicateOutput1 E_ACCESSDENIED. That
rules out reparenting (the hook works) and DPI -> it is fullscreen
independent-flip / MPO: the SudoVDA virtual display, isolated as the SOLE
active output, scans out one plane on one display, bypassing DWM composition,
so Desktop Duplication gets a born-lost duplication.

Apollo never hits this because it runs WITH a physical monitor attached
(multi-display is already DWM-composited); we isolate to sole-display, so we
must force composition ourselves. The fix already existed (ForceComposedFlip,
a tiny topmost layered overlay that disqualifies independent-flip) but was
only wired into the WGC relay path's secure branch, which PUNKTFUNK_NO_WGC=1
disables. Wire it into virtual_stream unconditionally (DDA owns the normal
desktop here, where the storm is). Held for the session; Drop tears it down;
PUNKTFUNK_FORCE_COMPOSED=0 disables.

Keeps the prior build's born-lost escape as a safety net.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-16 14:08:59 +00:00
parent 63b63a4010
commit 5f84c5785c
1 changed files with 13 additions and 0 deletions
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crates/punktfunk-host/src/m3.rs
+13
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@@ -2026,6 +2026,19 @@ fn virtual_stream(
let (mut capturer, mut enc, mut frame, mut interval) = let (mut capturer, mut enc, mut frame, mut interval) =
build_pipeline_with_retry(&mut vd, mode, bitrate_kbps, bit_depth)?; build_pipeline_with_retry(&mut vd, mode, bitrate_kbps, bit_depth)?;
// Windows single-process DDA path (PUNKTFUNK_NO_WGC=1): the SudoVDA virtual display, isolated as the
// SOLE active output, goes into fullscreen independent-flip (one plane on one display) which Desktop
// Duplication cannot capture → the born-lost ACCESS_LOST storm we measured on the RTX4090+iGPU box
// (hook verified-firing, DPI=2, yet 100% DuplicateOutput1 E_ACCESSDENIED + born-lost). A tiny topmost
// layered overlay disqualifies independent-flip and forces DWM composition, which DDA CAN capture.
// (Apollo never hits this because it runs WITH a physical monitor attached — multi-display is already
// DWM-composited; we isolate to sole-display, so we must force composition ourselves.) Unlike the WGC
// relay path — where WGC owns the normal desktop and the overlay is secure-only — here DDA owns the
// normal desktop too, so it must run unconditionally. Held for the session; Drop tears it down.
// Best-effort; disable with PUNKTFUNK_FORCE_COMPOSED=0.
#[cfg(target_os = "windows")]
let _composed_flip = crate::capture::composed_flip::ForceComposedFlip::start();
let perf = std::env::var("PUNKTFUNK_PERF").is_ok(); let perf = std::env::var("PUNKTFUNK_PERF").is_ok();
// Microburst cap (applied in send_loop/paced_submit): a frame ≤ this bursts out immediately; // Microburst cap (applied in send_loop/paced_submit): a frame ≤ this bursts out immediately;
// only a bigger frame's overflow is spread. PUNKTFUNK_PACE_BURST_KB overrides the 128 KB default. // only a bigger frame's overflow is spread. PUNKTFUNK_PACE_BURST_KB overrides the 128 KB default.