EncoderCaps::blends_cursor's contract said the HOST must fall back to
capturer-side compositing when a cursor-as-metadata session lands on an
encoder that can't composite — but that host half was never built: open_video
warned and the session streamed WITHOUT a pointer (confirmed on the VAAPI
dmabuf and libav-NVENC CUDA paths; latent on vulkan RGB-direct/native-NV12).
The negotiation is now caps-aware, ahead of capture, on both planes:
* pf-encode grows cursor_blend_capable() — the pre-open dispatch mirror
(sibling of linux_native_nv12_ok) answering whether the resolved backend
composites frame.cursor; its pure core is test-pinned arm by arm.
* Native plane: handshake::cursor_forward grants the cursor channel only
where the resolved backend can blend (the capture-mouse flip makes the host
draw the pointer on demand); denied sessions keep the pre-channel path —
the compositor EMBEDS the pointer, never cursorless, never doubled. The
Welcome's HOST_CAP_CURSOR bit is computed once and read back at both
session-wiring sites instead of recomputed. SessionPlan::output_format
additionally keeps every cursor-blend session off producer-native NV12 (the
arm with no CSC to fold a cursor into), and vulkan RGB-direct now yields to
a cursor-blend session even when pinned (EFC cannot composite; the open
logs the override). Windows plans cursor_blend=false via the new shared
cursor_blend_for() rule — the IDD capturer composites the pointer itself,
and asking the encoder anyway fired the blends-cursor warn spuriously on
every cursor-channel session.
* GameStream plane: the hardcoded cursor_blend=true is gone. The portal
source asks for cursor-as-metadata only when the resolved backend blends,
otherwise negotiates an Embedded pointer (choose_cursor_mode's new ladder);
the capturer pool now also keys on that mode. The virtual-output source
passes false — its capture embeds the pointer where it can.
The per-arm warns in vulkan_video (RGB-direct, native-NV12) are now
structurally unreachable and removed. open_video's post-open check stays as
the single backstop for what planning cannot see: a Vulkan-open falling back
to VAAPI mid-session, and the gamescope residual (no embedded mode exists
there, so a never-blending backend — H.264-on-AMD VAAPI, software — still
streams cursorless; fixing that needs a compositing stage, deliberately not
built in this pass). Zero-copy is preserved throughout — every fallback is a
capture-negotiation change, never a readback.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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