A freshly-added IddCx virtual display lands in CLONE/duplicate mode when a
physical display is already active (a laptop panel, an attached monitor): the
cloned output shares that display's source, so the OS never commits a distinct
path for it, never calls ASSIGN_SWAPCHAIN, and capture sees no frames - the
session fails "not an active display path / needs a WDDM GPU to activate" and
tears down with 0 frames (seen live on an Intel-iGPU + NVIDIA-Optimus laptop).
force_extend_topology() applies the EXTEND preset (the programmatic Win+P
"Extend") right after ADD so the IDD comes up as its own active path; the
existing resolve_gdi_name -> set_active_mode -> isolate_displays_ccd bring-up
then proceeds. Idempotent / no-op on a sole-display (headless single-GPU) box,
so it's safe on the path that already worked.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
8e87e617df