ROOT CAUSE (verified by multi-agent compare vs Apollo + adversarial review):
set_active_mode() applied the SudoVDA mode with CDS_UPDATEREGISTRY | CDS_GLOBAL
| CDS_SET_PRIMARY + DM_POSITION(0,0) — promoting the freshly-added IDD to
PRIMARY at the virtual-screen origin and persisting it globally. On this box
(baseline active display = a 1024x768 basic 'WinDisc') that primary-promotion
contests the existing display so the desktop topology never reaches a stable
fixed point → every DuplicateOutput/AcquireNextFrame during the unending
settle returns DXGI_ERROR_MODE_CHANGE_IN_PROGRESS (0x887A0025). Apollo, live
on this EXACT box with an empty config, never promotes primary and captures
the same SudoVDA at 5120x1440 with zero DXGI errors. (Ruled out earlier on the
live box: win32u hook, DPI, independent-flip/overlay, isolation, render pin.)
Fixes (subtractive, gated per adversarial review):
- sudovda.rs set_active_mode: default to CDS_UPDATEREGISTRY only (no primary
promotion, no GLOBAL, no DM_POSITION) = Apollo-parity for the multi-display
default. Promote to primary (CDS_GLOBAL|CDS_SET_PRIMARY+DM_POSITION) ONLY
when PUNKTFUNK_ISOLATE_DISPLAYS=1 (sole display, where a blank extended IDD
would otherwise yield no frames). Avoids regressing headless/isolated +
mid-stream Reconfigure.
- dxgi.rs acquire: treat MODE_CHANGE_IN_PROGRESS (0x887A0025) as a TRANSIENT
(Ok(None), repeat last frame, wait it out) instead of falling through to the
fatal Err arm → cold-rebuild → create()→set_active_mode (which re-issued the
mode change and amplified the storm).
- dxgi.rs acquire: remove the born-lost cold-rebuild escape — it re-created the
SudoVDA (IOCTL REMOVE/ADD = the audible PnP chime the user heard) and never
converged; now repeat last frame in-process (never tear the IDD down mid-
session, like Apollo). Overlay + cheap-spin/HDR recovery left intact.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
enricobuehler
769fd96b87