feat(windows-host): IDD-push attach fallback to DDA, not the 20s black bail (audit §5.1)

open() now hands the keepalive BACK on failure (the WGC attach_keepalive pattern) so the caller can fall back instead of tearing the virtual display down. Added a bounded wait_for_attach() that polls the driver's DRV_STATUS_OPENED — it checks ATTACH status, not frame arrival, so it never false-fails on an idle desktop that has composed no frame yet. An attach failure (e.g. a hybrid-GPU render mismatch -> DRV_STATUS_TEX_FAIL, or the driver never opening the ring within 4s) now fails open() -> capture.rs falls back to DDA, instead of next_frame's 20s deadline leaving the session black. Pairs with the driver SET_RENDER_ADAPTER fix (0a7ae5e). Verified: host clippy (nvenc) clean on the RTX box. Behavioral validation (fallback trigger + happy-path attach timing) needs an on-glass session. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-25 13:09:28 +00:00
parent e5c9ee8327
commit ed583650a6
2 changed files with 77 additions and 7 deletions
@@ -351,8 +351,20 @@ pub fn capture_virtual_output(
        // the host can't revive it. The driver's recreate crash (target id resolved to 0) is fixed by
        // stamping target_id onto the monitor context. The ring is always FP16 (the driver composes
        // the IDD in FP16); `want_hdr` selects the per-frame conversion (FP16 → Rgb10a2 vs Bgra).
-        return idd_push::IddPushCapturer::open(target, pref, want_hdr, keep)
-            .map(|c| Box::new(c) as Box<dyn Capturer>);
+        // If IDD-push can't open OR the driver doesn't attach to the ring within a few seconds (e.g. a
+        // hybrid-GPU render mismatch), fall back to DDA so the session is NEVER left black (audit §5.1).
+        // `open()` hands the keepalive back on failure so DDA can take ownership of the virtual display.
+        match idd_push::IddPushCapturer::open(target.clone(), pref, want_hdr, keep) {
+            Ok(c) => return Ok(Box::new(c) as Box<dyn Capturer>),
+            Err((e, keep)) => {
+                tracing::warn!(
+                    error = %format!("{e:#}"),
+                    "IDD-push open/attach failed — falling back to DDA"
+                );
+                return dxgi::DuplCapturer::open(target, pref, keep, false)
+                    .map(|c| Box::new(c) as Box<dyn Capturer>);
+            }
+        }
    }
    // WGC (Windows.Graphics.Capture) is the default: it captures the COMPOSED desktop including the
    // overlay/independent-flip planes DXGI Desktop Duplication misses (the frozen-HDR-animation bug),