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fix(host/windows): per-thread Per-Monitor-V2 DPI awareness so DuplicateOutput1 succeeds

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The remaining born-lost ACCESS_LOST storm traces to ONE thing: our
IDXGIOutput5::DuplicateOutput1 returns E_ACCESSDENIED (0x80070005) ~4370x, so
we fall back to legacy DuplicateOutput, which yields a BORN-LOST duplication on
this hybrid box. Apollo's DuplicateOutput1 SUCCEEDS on the identical
desktop/output/4090-device → a working dup, clean capture.

Root cause: DuplicateOutput1 REQUIRES Per-Monitor-Aware-V2. At startup our
SetProcessDpiAwarenessContext(PER_MONITOR_AWARE_V2) FAILS with E_ACCESSDENIED
('already set' — a manifest/runtime locked the process to a lower awareness),
and GetAwarenessFromDpiAwarenessContext reports 2 for BOTH Per-Monitor V1 and
V2, so the earlier 'awareness=2' was misleading — the process is likely V1,
which DuplicateOutput1 rejects with E_ACCESSDENIED. (Legacy DuplicateOutput has
no V2 requirement, so it 'worked' but born-lost.)

Fix: SetThreadDpiAwarenessContext(PER_MONITOR_AWARE_V2) on the capture thread
in open() — a per-thread override that takes regardless of the process default,
so DuplicateOutput1 can succeed (the working dup Apollo gets). Logs set_ok +
thread_is_v2 (via AreDpiAwarenessContextsEqual) to confirm V2 actually applied.
Topology fixes (sole display, no MODE_CHANGE) and the recovery backstops stay.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Enrico Bühler
2026-06-16 15:29:17 +00:00
parent c60a05dbe9
commit c8fb4822a2
1 changed files with 25 additions and 0 deletions
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crates/punktfunk-host/src/capture/dxgi.rs
+25
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@@ -1026,6 +1026,31 @@ impl DuplCapturer {
// Stop DXGI hybrid-GPU output reparenting BEFORE we create the factory / enumerate outputs
// (the cause of the 0x887A0026 ACCESS_LOST churn on this hybrid box: RTX 4090 + AMD iGPU).
install_gpu_pref_hook();
// Force PER-MONITOR-AWARE-V2 on THIS (capture) thread. IDXGIOutput5::DuplicateOutput1
// REQUIRES V2 — without it the call returns E_ACCESSDENIED forever (the 4370x failures
// measured live), forcing the legacy DuplicateOutput fallback which yields a BORN-LOST
// duplication on this box → the ACCESS_LOST storm. SetProcessDpiAwarenessContext failed at
// startup ("already set" — a manifest/runtime locked the process to a LOWER awareness, and
// GetAwarenessFromDpiAwarenessContext can't tell V1 from V2: it reports 2 for both). The
// per-THREAD override works regardless of the process default, so DuplicateOutput1 can
// succeed (the working dup Apollo gets). Must run on the capture thread before any DXGI use.
{
use windows::Win32::UI::HiDpi::{
AreDpiAwarenessContextsEqual, GetThreadDpiAwarenessContext,
SetThreadDpiAwarenessContext, DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2,
};
let prev = SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
let is_v2 = AreDpiAwarenessContextsEqual(
GetThreadDpiAwarenessContext(),
DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2,
)
.as_bool();
tracing::info!(
set_ok = !prev.0.is_null(),
thread_is_v2 = is_v2,
"capture thread DPI awareness -> PER_MONITOR_AWARE_V2 (required for DuplicateOutput1)"
);
}
// Keep the IDD (SudoVDA) virtual display awake for the capture lifetime: an idle indirect
// display can be power-gated, which invalidates the duplication (a contributor to the
// "freezes randomly while streaming" loss). Restored to ES_CONTINUOUS on Drop. (Apollo does