fix(host/encode): negotiate the cursor around what the encoder can blend

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>

crates/pf-capture/src/lib.rs

@@ -447,14 +447,24 @@ pub mod synthetic_nv12;
 /// `want_hdr` offers the GNOME 50+ HDR formats (10-bit PQ/BT.2020 dmabufs) instead of the SDR
 /// set — pass it only when the mirrored monitor is actually in HDR mode (the host probes
 /// DisplayConfig) or the negotiation runs into its 10 s timeout and latches the SDR downgrade.
-/// The [`ZeroCopyPolicy`] carries the pre-resolved encode-backend facts (the one-way edge).
+/// `want_metadata_cursor` asks for cursor-as-metadata (`SPA_META_Cursor`) — pass it only when
+/// the session's encode path composites `CapturedFrame::cursor` (the host consults
+/// `pf-encode`'s `cursor_blend_capable`); otherwise the portal EMBEDS the pointer so it is
+/// never silently lost. The [`ZeroCopyPolicy`] carries the pre-resolved encode-backend facts
+/// (the one-way edge).
 #[cfg(target_os = "linux")]
 pub fn open_portal_monitor(
     anchored: bool,
     want_hdr: bool,
+    want_metadata_cursor: bool,
     policy: ZeroCopyPolicy,
 ) -> Result<Box<dyn Capturer>> {
-    linux::PortalCapturer::open(anchored, want_hdr && !hdr_capture_failed(), policy)
+    linux::PortalCapturer::open(
+        anchored,
+        want_hdr && !hdr_capture_failed(),
+        want_metadata_cursor,
+        policy,
+    )
     .map(|c| Box::new(c) as Box<dyn Capturer>)
 }
 

crates/pf-capture/src/linux/mod.rs

@@ -105,16 +105,21 @@ impl PortalCapturer {
     /// RemoteDesktop grant and never raises a separate ScreenCast dialog; `false` uses a plain
     /// ScreenCast session (wlroots, which has no RemoteDesktop portal). `want_hdr` offers the
     /// GNOME 50+ HDR formats (10-bit PQ/BT.2020, dmabuf-only) instead of the SDR set.
-    pub fn open(anchored: bool, want_hdr: bool, policy: ZeroCopyPolicy) -> Result<PortalCapturer> {
+    pub fn open(
+        anchored: bool,
+        want_hdr: bool,
+        want_metadata_cursor: bool,
+        policy: ZeroCopyPolicy,
+    ) -> Result<PortalCapturer> {
         // Portal handshake (async) on its own thread; hands back the PW fd + node id.
         let (setup_tx, setup_rx) = std::sync::mpsc::channel::<Result<(OwnedFd, u32), String>>();
         thread::Builder::new()
             .name("punktfunk-portal".into())
             .spawn(move || {
                 if anchored {
-                    portal_thread_remote_desktop(setup_tx)
+                    portal_thread_remote_desktop(setup_tx, want_metadata_cursor)
                 } else {
-                    portal_thread(setup_tx)
+                    portal_thread(setup_tx, want_metadata_cursor)
                 }
             })
             .context("spawn portal thread")?;
@@ -647,19 +652,23 @@ pub fn gnome_hdr_monitor_active() -> bool {
     }
 }
 
-/// Pick the ScreenCast cursor mode from what the backend advertises (`AvailableCursorModes`),
+/// Pick the ScreenCast cursor mode from what the backend advertises (`AvailableCursorModes`).
-/// preferring **cursor-as-metadata**: the compositor keeps its cheap hardware cursor plane and
+/// With `want_metadata` the ladder prefers **cursor-as-metadata**: the compositor keeps its cheap
-/// ships the pointer as PipeWire `SPA_META_Cursor` metadata (position + an occasional bitmap),
+/// hardware cursor plane and ships the pointer as PipeWire `SPA_META_Cursor` metadata (position +
-/// which the consumer composites itself. That avoids forcing the producer to burn the cursor into
+/// an occasional bitmap), which the consumer composites itself — avoiding the producer burning the
-/// every frame — the `Embedded` mode — which on gamescope would defeat its HW cursor plane. Falls
+/// cursor into every frame (`Embedded`), which on gamescope would defeat its HW cursor plane.
-/// back to `Embedded`, then `Hidden`, and (if the property query fails, e.g. an older portal)
+/// Without it — the session's encode path has no compositing stage for a metadata cursor
-/// keeps the prior `Embedded` behavior so the cursor is never silently lost.
+/// (`pf-encode`'s `cursor_blend_capable` said the resolved backend can't blend) — the ladder
+/// prefers `Embedded`, so the pointer is in the pixels instead of in metadata nothing would draw.
+/// Both ladders fall through to the other mode, then `Hidden`; a failed property query (an older
+/// portal) keeps the prior `Embedded` behavior so the cursor is never silently lost.
 async fn choose_cursor_mode(
     proxy: &ashpd::desktop::screencast::Screencast,
+    want_metadata: bool,
 ) -> ashpd::desktop::screencast::CursorMode {
     use ashpd::desktop::screencast::CursorMode;
     match proxy.available_cursor_modes().await {
-        Ok(avail) if avail.contains(CursorMode::Metadata) => {
+        Ok(avail) if want_metadata && avail.contains(CursorMode::Metadata) => {
             tracing::info!(
                 ?avail,
                 "ScreenCast: requesting cursor-as-metadata (SPA_META_Cursor)"
@@ -667,12 +676,30 @@ async fn choose_cursor_mode(
             CursorMode::Metadata
         }
         Ok(avail) if avail.contains(CursorMode::Embedded) => {
+            if want_metadata {
                 tracing::info!(
                     ?avail,
                     "ScreenCast: cursor metadata unavailable — requesting Embedded cursor"
                 );
+            } else {
+                tracing::info!(
+                    ?avail,
+                    "ScreenCast: requesting Embedded cursor (this session's encoder does not \
+                     composite a metadata cursor)"
+                );
+            }
             CursorMode::Embedded
         }
+        Ok(avail) if avail.contains(CursorMode::Metadata) => {
+            // Embedded wanted but not offered. Metadata still beats Hidden: the CPU capture
+            // path composites `SPA_META_Cursor` inline, so part of the matrix keeps a pointer.
+            tracing::warn!(
+                ?avail,
+                "ScreenCast: Embedded cursor not advertised — requesting cursor-as-metadata \
+                 (only CPU-path frames will composite it)"
+            );
+            CursorMode::Metadata
+        }
         Ok(avail) => {
             tracing::warn!(
                 ?avail,
@@ -692,7 +719,10 @@ async fn choose_cursor_mode(
 
 /// The portal handshake: connect ScreenCast, select a single monitor, start, open the
 /// PipeWire remote, hand the fd + node id back, then keep the session alive.
-fn portal_thread(setup_tx: std::sync::mpsc::Sender<Result<(OwnedFd, u32), String>>) {
+fn portal_thread(
+    setup_tx: std::sync::mpsc::Sender<Result<(OwnedFd, u32), String>>,
+    want_metadata_cursor: bool,
+) {
     use ashpd::desktop::screencast::{Screencast, SelectSourcesOptions, SourceType};
     use ashpd::desktop::PersistMode;
     use ashpd::enumflags2::BitFlags;
@@ -722,7 +752,7 @@ fn portal_thread(setup_tx: std::sync::mpsc::Sender<Result<(OwnedFd, u32), String
                 .create_session(Default::default())
                 .await
                 .context("create_session")?;
-            let cursor_mode = choose_cursor_mode(&proxy).await;
+            let cursor_mode = choose_cursor_mode(&proxy, want_metadata_cursor).await;
             proxy
                 .select_sources(
                     &session,
@@ -781,7 +811,10 @@ fn portal_thread(setup_tx: std::sync::mpsc::Sender<Result<(OwnedFd, u32), String
 /// path — also covers screen capture, with no separate ScreenCast dialog (which has no such
 /// bypass). Yields the same PipeWire fd + node id as the standalone path; the consumer is
 /// identical.
-fn portal_thread_remote_desktop(setup_tx: std::sync::mpsc::Sender<Result<(OwnedFd, u32), String>>) {
+fn portal_thread_remote_desktop(
+    setup_tx: std::sync::mpsc::Sender<Result<(OwnedFd, u32), String>>,
+    want_metadata_cursor: bool,
+) {
     use ashpd::desktop::remote_desktop::{DeviceType, RemoteDesktop, SelectDevicesOptions};
     use ashpd::desktop::screencast::{Screencast, SelectSourcesOptions, SourceType};
     use ashpd::desktop::PersistMode;
@@ -826,7 +859,7 @@ fn portal_thread_remote_desktop(setup_tx: std::sync::mpsc::Sender<Result<(OwnedF
                 .context("select_devices")?
                 .response()
                 .context("select_devices rejected")?;
-            let cursor_mode = choose_cursor_mode(&screencast).await;
+            let cursor_mode = choose_cursor_mode(&screencast, want_metadata_cursor).await;
             screencast
                 .select_sources(
                     &session,

crates/pf-encode/src/enc/codec.rs

@@ -307,8 +307,11 @@ pub struct EncoderCaps {
     ///
     /// This makes the answer queryable instead of assumed. It is deliberately a plain fact about the
     /// encoder, not a policy: what to DO when a session wants blending and the backend cannot is the
-    /// host's call, since only the host can re-plan capture (fall back to capturer-side compositing).
+    /// host's call, since only the host can re-plan capture. That call is wired now — the
-    /// `open_video` can only warn, which it does.
+    /// negotiation consults the pre-open mirror ([`cursor_blend_capable`](crate::cursor_blend_capable))
+    /// to gate the cursor channel and to keep capture on embedded-cursor / CSC-capable shapes for
+    /// any backend that can't blend; `open_video`'s post-open check remains as the backstop for
+    /// open-time fallbacks the plan can't see.
     pub blends_cursor: bool,
 }
 

crates/pf-encode/src/enc/linux/vulkan_video.rs

@@ -76,9 +76,11 @@ fn quality_request() -> u32 {
 /// (design/vulkan-rgb-direct-encode.md): the captured RGB frame is the encode source and the
 /// VCN EFC front-end does the 709-narrow CSC inline — no compute CSC, no plane copies, one
 /// queue submit per frame (unaligned modes go through the padded-copy staging blit). B2
-/// default: ON wherever the probe passes, EXCEPT sessions that may need the CSC's cursor
+/// default: ON wherever the probe passes, EXCEPT sessions that need the CSC's cursor blend
-/// blend (see [`VulkanVideoEncoder::open`]). `=0` disables outright; `=1` forces it even on
+/// (see [`VulkanVideoEncoder::open`]). `=0` disables outright; `=1` forces it on non-cursor
-/// cursor-blend sessions (the pointer will be missing from the stream); unset = the default.
+/// sessions; unset = the default. A cursor-blend session IGNORES `=1` — EFC cannot composite
+/// the pointer, and the caps-aware negotiation promised the client a composited one, so the
+/// pointer outranks the lab pin (the open logs the override).
 ///
 /// Parses like every sibling knob (`matches!(v.trim(), …)`): anything unrecognised — including
 /// an empty value and a value that is only whitespace — falls back to the default rather than
@@ -614,10 +616,6 @@ pub struct VulkanVideoEncoder {
     /// GPU reset (those paths keep their aligned-size sources/staging).
     native_nv12: bool,
 
-    /// One-shot warning latch: a cursor bitmap arrived on an RGB-direct or native-NV12 session
-    /// (neither has a compositing stage — the cursor will be missing from the stream until the
-    /// CSC path is used).
-    warned_cursor: bool,
     /// A [`reconfigure_bitrate`](Encoder::reconfigure_bitrate) rate not yet installed in the video
     /// session. The next `record_submit` emits an `ENCODE_RATE_CONTROL` control command carrying it
     /// (mid-stream) or folds it into the first frame's RESET+RC install, then promotes it into
@@ -671,7 +669,16 @@ impl VulkanVideoEncoder {
         cursor_blend: bool,
     ) -> Result<Self> {
         let native_nv12 = format == PixelFormat::Nv12;
-        let want_rgb = !native_nv12 && rgb_request().unwrap_or(!cursor_blend);
+        // A cursor-blend session must keep the compute-CSC path — the only arm with the cursor
+        // blend — so it outranks an explicit RGB-direct pin (EFC cannot composite; the
+        // negotiation promised the client a composited pointer).
+        if cursor_blend && rgb_request() == Some(true) {
+            tracing::info!(
+                "PUNKTFUNK_VULKAN_RGB_DIRECT=1 ignored for this session — it composites the \
+                 pointer, which the EFC front-end cannot; using the compute-CSC path"
+            );
+        }
+        let want_rgb = !native_nv12 && !cursor_blend && rgb_request().unwrap_or(true);
         Self::open_opts_inner(
             codec,
             width,
@@ -1448,7 +1455,6 @@ impl VulkanVideoEncoder {
             cpu_expand: Vec::new(),
             rgb: rgb_cfg,
             native_nv12,
-            warned_cursor: false,
             pending_bitrate: None,
             width: w,
             height: h,
@@ -2621,17 +2627,10 @@ impl VulkanVideoEncoder {
                 d.modifier
             );
         }
-        // No compositing stage exists here (like RGB-direct/EFC): gamescope embeds its pointer
+        // No compositing stage exists here (like RGB-direct/EFC) — and none is needed: the
-        // in the produced pixels, but any other NV12 producer's metadata cursor would be lost —
+        // session plan negotiates native NV12 only for a non-cursor-blend session
-        // say so once instead of silently.
+        // (`SessionPlan::output_format` gates `nv12_native` on `!cursor_blend`), so no cursor
-        if frame.cursor.is_some() && !self.warned_cursor {
+        // bitmap ever reaches this arm. Gamescope embeds its pointer in the produced pixels.
-            self.warned_cursor = true;
-            tracing::warn!(
-                "cursor bitmap on a native-NV12 session — nothing composites it; the cursor \
-                 will be missing from the stream (unset PUNKTFUNK_PIPEWIRE_NV12 for \
-                 metadata-cursor captures)"
-            );
-        }
         let dev = self.device.clone();
         let cmd = self.frames[slot].cmd;
         let fence = self.frames[slot].fence;
@@ -2691,16 +2690,9 @@ impl VulkanVideoEncoder {
         let query_pool = self.frames[slot].query_pool;
         let bs_buf = self.frames[slot].bs_buf;
         let ts_pool = self.frames[slot].ts_pool;
-        // EFC cannot composite the cursor bitmap the metadata-cursor captures hand us — say so
+        // EFC cannot composite a cursor bitmap — and never has to: `open` refuses the RGB-direct
-        // once instead of silently losing the pointer (gamescope, the flagship, embeds it).
+        // shape for a cursor-blend session (the pin override above), so no cursor bitmap ever
-        if frame.cursor.is_some() && !self.warned_cursor {
+        // reaches this arm. Gamescope, the flagship, embeds its pointer in the produced pixels.
-            self.warned_cursor = true;
-            tracing::warn!(
-                "cursor bitmap on an RGB-direct session — EFC cannot composite it; the cursor \
-                 will be missing from the stream (unset PUNKTFUNK_VULKAN_RGB_DIRECT for \
-                 metadata-cursor captures)"
-            );
-        }
         let padded = self.rgb.as_ref().is_some_and(|r| r.padded);
         // Only the padded Dmabuf arm below records timestamps (via `record_pad_blit`); the
         // CPU-upload arm records its own command buffer and writes none. Default to "not written"

crates/pf-encode/src/lib.rs

@@ -203,14 +203,15 @@ pub fn open_video(
         }
     };
     // The session asked for a composited pointer; say so loudly if the backend that actually opened
-    // cannot deliver one. `cursor_blend` was a REQUEST with no answer for most of this crate's life
+    // cannot deliver one. Since the negotiation became caps-aware ([`cursor_blend_capable`] gates
-    // (`let _ = cursor_blend;` below), and the result was a stream with no mouse cursor and nothing
+    // the cursor channel, and the session plan keeps cursor sessions off the native-NV12/RGB-direct
-    // in the logs — confirmed on the VAAPI dmabuf path and the libav-NVENC CUDA path.
+    // shapes), no PLANNED path reaches this: capture negotiates embedded-cursor mode wherever the
-    //
+    // resolved backend can't blend. What remains reachable is the open-time divergence the plan
-    // A warning is deliberately all this does. `open_video` cannot re-plan capture, so refusing here
+    // cannot see — a Vulkan Video open failing back to VAAPI mid-`open_amd_intel`, and the
-    // would only trade a missing pointer for a dead session; the host owns `plan.cursor_blend` and is
+    // gamescope residual (gamescope has no embedded mode, so a never-blending backend there —
-    // the only layer that can fall back to capturer-side compositing. This makes the condition
+    // H.264→VAAPI, software — still streams cursorless). This is the backstop that keeps those
-    // visible and queryable (`EncoderCaps::blends_cursor`) so that decision can be made upstream.
+    // honest in the logs; `open_video` cannot re-plan capture, so a warning is deliberately all
+    // it does.
     if cursor_blend && !inner.caps().blends_cursor {
         tracing::warn!(
             backend,
@@ -989,6 +990,87 @@ pub fn linux_native_nv12_ok(codec: Codec) -> bool {
     }
 }
 
+/// Whether the encode backend this session will resolve to composites [`CapturedFrame::cursor`]
+/// ([`EncoderCaps::blends_cursor`]) — answered BEFORE capture opens, so the host plans cursor
+/// delivery honestly instead of discovering a cursorless stream after the fact (the
+/// `blends_cursor` audit finding): a blend-capable backend takes cursor-as-metadata capture
+/// (pointer-free frames + host composite on demand — the cursor channel's contract); for
+/// anything else the host must have the compositor EMBED the pointer. The sibling verdict of
+/// [`linux_native_nv12_ok`], threaded into the same negotiation.
+///
+/// `cuda_planned` is the caller's prediction of a CUDA capture payload (NVIDIA + zero-copy — the
+/// prediction `SessionPlan` already makes); `ten_bit` the negotiated depth. Both shift the
+/// dispatch: a CPU payload keeps NVIDIA on libav NVENC (no blend), and a 10-bit HDR session
+/// skips Vulkan Video for libav VAAPI's P010/Main10 wiring (no blend).
+#[cfg(target_os = "linux")]
+pub fn cursor_blend_capable(codec: Codec, cuda_planned: bool, ten_bit: bool) -> bool {
+    // A negotiated PyroWave session routes to that backend before the pref is consulted
+    // (`open_video_backend_linux`), and its wavelet CSC composites the metadata cursor.
+    if codec == Codec::PyroWave {
+        return true;
+    }
+    let direct_nvenc = {
+        #[cfg(feature = "nvenc")]
+        {
+            nvenc_direct_enabled()
+        }
+        #[cfg(not(feature = "nvenc"))]
+        {
+            false
+        }
+    };
+    let vulkan_csc = {
+        // The compute-CSC arm — the one that blends. Eligibility mirrors `open_amd_intel`;
+        // the device probe runs last (it opens a Vulkan instance, cached per GPU+codec).
+        #[cfg(feature = "vulkan-encode")]
+        {
+            matches!(codec, Codec::H265 | Codec::Av1)
+                && vulkan_encode_enabled()
+                && vulkan_encode_available(codec)
+        }
+        #[cfg(not(feature = "vulkan-encode"))]
+        {
+            false
+        }
+    };
+    let backend = resolve_linux_backend(
+        pf_host_config::config().encoder_pref.as_str(),
+        linux_auto_is_vaapi,
+        cuda_planned,
+    );
+    cursor_blend_capable_for(backend, cuda_planned, ten_bit, direct_nvenc, vulkan_csc)
+}
+
+/// The dispatch-mirroring core of [`cursor_blend_capable`], device-free for the unit tests.
+/// `direct_nvenc` = the direct-SDK NVENC path is compiled in and enabled; `vulkan_csc` = the
+/// Vulkan Video compute-CSC arm (the one that blends) is compiled in, enabled, and
+/// device-supported for the session's codec.
+#[cfg(target_os = "linux")]
+fn cursor_blend_capable_for(
+    backend: Option<LinuxBackend>,
+    cuda_planned: bool,
+    ten_bit: bool,
+    direct_nvenc: bool,
+    vulkan_csc: bool,
+) -> bool {
+    match backend {
+        // The wavelet CSC composites the metadata cursor (`linux/pyrowave.rs`).
+        Some(LinuxBackend::Pyrowave) => true,
+        // Only the direct-SDK arm blends (VkSlotBlend), and it only takes CUDA payloads —
+        // a CPU-payload session stays on libav NVENC, which cannot blend.
+        Some(LinuxBackend::Nvenc) => cuda_planned && direct_nvenc,
+        // The Vulkan Video compute-CSC path blends; a 10-bit HDR session skips it for libav
+        // VAAPI (no blend). The session plan keeps a cursor-blend session off the native-NV12
+        // and RGB-direct shapes (`SessionPlan::output_format` / `VulkanVideoEncoder::open`),
+        // so CSC eligibility IS the answer.
+        Some(LinuxBackend::AmdIntel) | Some(LinuxBackend::Vulkan) => !ten_bit && vulkan_csc,
+        // CPU frames: the capturer composites the metadata cursor inline before the encoder
+        // runs, but the ENCODER blends nothing — the cursor channel's on-demand composite
+        // contract can't be honored. Report the encoder's truth.
+        Some(LinuxBackend::Software) | None => false,
+    }
+}
+
 /// Can this GPU + driver actually open a Vulkan Video **encode** session for `codec`? Cached per
 /// (selected GPU, codec) — the [`can_encode_10bit`] idiom, with the probe run outside the lock.
 ///
@@ -1754,6 +1836,72 @@ mod tests {
         assert_eq!(none.wire_mask(), None);
     }
 
+    /// The cursor-blend capability mirror, arm by arm — the table the caps-aware negotiation
+    /// (cursor channel grant, metadata-vs-embedded capture) stands on. Each row names the arm's
+    /// blending stage or the reason there is none.
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn cursor_blend_capability_mirrors_the_dispatch() {
+        use LinuxBackend::*;
+        // PyroWave: the wavelet CSC composites, always.
+        assert!(cursor_blend_capable_for(
+            Some(Pyrowave),
+            false,
+            false,
+            false,
+            false
+        ));
+        // NVIDIA: only the direct-SDK arm blends (VkSlotBlend), and only for CUDA payloads.
+        assert!(cursor_blend_capable_for(
+            Some(Nvenc),
+            true,
+            false,
+            true,
+            false
+        ));
+        assert!(
+            !cursor_blend_capable_for(Some(Nvenc), false, false, true, false),
+            "a CPU payload stays on libav NVENC, which cannot blend"
+        );
+        assert!(
+            !cursor_blend_capable_for(Some(Nvenc), true, false, false, false),
+            "PUNKTFUNK_NVENC_DIRECT=0 (or a build without the feature) is the libav path"
+        );
+        // AMD/Intel: the Vulkan Video compute-CSC arm blends; VAAPI never does.
+        assert!(cursor_blend_capable_for(
+            Some(AmdIntel),
+            false,
+            false,
+            false,
+            true
+        ));
+        assert!(
+            !cursor_blend_capable_for(Some(AmdIntel), false, false, false, false),
+            "no eligible Vulkan CSC arm (H.264, PUNKTFUNK_VULKAN_ENCODE=0, unsupported \
+             device) resolves to libav VAAPI, which cannot blend"
+        );
+        assert!(
+            !cursor_blend_capable_for(Some(AmdIntel), false, true, false, true),
+            "a 10-bit HDR session skips Vulkan Video for VAAPI's P010 wiring — no blend"
+        );
+        assert!(cursor_blend_capable_for(
+            Some(Vulkan),
+            false,
+            false,
+            false,
+            true
+        ));
+        // Software / unknown pref: CPU frames; the encoder blends nothing.
+        assert!(!cursor_blend_capable_for(
+            Some(Software),
+            false,
+            false,
+            true,
+            true
+        ));
+        assert!(!cursor_blend_capable_for(None, false, false, true, true));
+    }
+
     /// WP7.7 guard (the cheap half): every `Encoder` trait method must be explicitly forwarded by
     /// `TrackedEncoder`. A defaulted trait method that isn't forwarded silently no-ops through the
     /// wrapper — the trap has bitten three times (`set_wire_chunking`'s §4.4 chunking probe,

crates/punktfunk-host/src/capture.rs

@@ -66,8 +66,14 @@ fn zero_copy_policy(
 /// Open a live capturer for a client-sized monitor via the xdg ScreenCast portal. `want_hdr`
 /// offers the GNOME 50+ 10-bit PQ/BT.2020 formats (pass it only when the session negotiated HDR
 /// AND the mirrored monitor is in HDR mode — see [`pf_capture::gnome_hdr_monitor_active`]).
+/// `want_metadata_cursor` asks for cursor-as-metadata — pass it only when the session's encode
+/// backend composites `CapturedFrame::cursor` (`encode::cursor_blend_capable`); otherwise the
+/// portal embeds the pointer, so no backend × cursor-mode combination streams cursorless.
 #[cfg(target_os = "linux")]
-pub fn open_portal_monitor(want_hdr: bool) -> Result<Box<dyn Capturer>> {
+pub fn open_portal_monitor(
+    want_hdr: bool,
+    want_metadata_cursor: bool,
+) -> Result<Box<dyn Capturer>> {
     // On RemoteDesktop-capable desktops (KWin/GNOME) anchor ScreenCast to a RemoteDesktop
     // session so it inherits that grant headlessly; wlroots/Sway has no RemoteDesktop portal,
     // so use a plain ScreenCast session there.
@@ -76,11 +82,19 @@ pub fn open_portal_monitor(want_hdr: bool) -> Result<Box<dyn Capturer>> {
     // passthrough is virtual-output-only; the global encoder-pref lever still applies inside.
     // Native NV12 stays off too: the mirror path doesn't resolve the codec here, and the desktop
     // compositors it mirrors (GNOME/KWin) don't produce NV12 anyway.
-    pf_capture::open_portal_monitor(anchored, want_hdr, zero_copy_policy(false, false))
+    pf_capture::open_portal_monitor(
+        anchored,
+        want_hdr,
+        want_metadata_cursor,
+        zero_copy_policy(false, false),
+    )
 }
 
 #[cfg(not(target_os = "linux"))]
-pub fn open_portal_monitor(_want_hdr: bool) -> Result<Box<dyn Capturer>> {
+pub fn open_portal_monitor(
+    _want_hdr: bool,
+    _want_metadata_cursor: bool,
+) -> Result<Box<dyn Capturer>> {
     anyhow::bail!("portal capture requires Linux (xdg-desktop-portal + PipeWire)")
 }
 

crates/punktfunk-host/src/gamestream/stream.rs

@@ -33,10 +33,14 @@ pub struct StreamConfig {
     pub hdr: bool,
 }
 
+/// A pooled capturer plus the two PipeWire-negotiation-time properties reuse must match on —
+/// its HDR-ness and its metadata-cursor mode; a mismatch on either needs a fresh screencast
+/// session (see `AppState::video_cap`).
+pub type PooledCapturer = (Box<dyn Capturer>, bool, bool);
+
 /// Slot for the persistent screen capturer, shared with the control plane and reused across
-/// streams so a reconnect doesn't open a second (conflicting) screencast session. The `bool` is
+/// streams so a reconnect doesn't open a second (conflicting) screencast session.
-/// the pooled capturer's HDR-ness (see `AppState::video_cap`).
+pub type CapturerSlot = Arc<std::sync::Mutex<Option<PooledCapturer>>>;
-pub type CapturerSlot = Arc<std::sync::Mutex<Option<(Box<dyn Capturer>, bool)>>>;
 
 /// A pending client reference-frame-invalidation range (lost `firstFrame..=lastFrame`), set by the
 /// control plane and drained by the video thread (see [`AppState::rfi_range`](super::AppState)).
@@ -136,7 +140,7 @@ fn run(
     running: &Arc<AtomicBool>,
     force_idr: &AtomicBool,
     rfi_range: &std::sync::Mutex<Option<(i64, i64)>>,
-    video_cap: &std::sync::Mutex<Option<(Box<dyn Capturer>, bool)>>,
+    video_cap: &std::sync::Mutex<Option<PooledCapturer>>,
     // Shared stats recorder for the web-console capture/graph. Threaded into `stream_body` (the
     // encode loop); per-frame sample emission is wired by a later pass.
     stats: &Arc<crate::stats_recorder::StatsRecorder>,
@@ -250,6 +254,12 @@ fn run(
         return stream_body(
             &mut capturer,
             Some(&rebuild),
+            // The virtual-output source never selects cursor-as-metadata (`set_hw_cursor` is
+            // never called → the compositor EMBEDS the pointer where it can), so the encoder
+            // is handed nothing to composite. gamescope remains the pointerless residual —
+            // its capture carries no cursor either way (the native plane's XFixes source is
+            // not wired on this plane).
+            false,
             &sock,
             cfg,
             running,
@@ -266,13 +276,34 @@ fn run(
     // pooled capturer's HDR-ness matching this stream's negotiated `cfg.hdr` — the depth is a
     // PipeWire-negotiation-time property of the screencast session, so an HDR↔SDR change needs a
     // fresh session (same pattern as the audio capturer's channel-count gate).
+    // Cursor-as-metadata only where the encode backend this session resolves to composites
+    // `frame.cursor` (the caps-aware negotiation — mirror of the native plane's); otherwise ask
+    // the portal to EMBED the pointer so no backend × cursor-mode combination streams
+    // cursorless. Synthetic frames carry no pointer either way.
+    let metadata_cursor = {
+        #[cfg(target_os = "linux")]
+        {
+            // Same CUDA-payload prediction SessionPlan/`handshake::cursor_forward` make:
+            // the NVIDIA resolution plus the zero-copy master switch.
+            let cuda_planned =
+                !crate::encode::linux_zero_copy_is_vaapi() && crate::zerocopy::enabled();
+            crate::encode::cursor_blend_capable(cfg.codec, cuda_planned, cfg.hdr)
+        }
+        #[cfg(not(target_os = "linux"))]
+        false
+    };
     let pooled = match video_cap.lock().unwrap().take() {
-        Some((c, was_hdr)) if was_hdr == cfg.hdr => Some(c),
+        Some((c, was_hdr, was_meta)) if was_hdr == cfg.hdr && was_meta == metadata_cursor => {
-        Some((c, was_hdr)) => {
+            Some(c)
+        }
+        Some((c, was_hdr, was_meta)) => {
             tracing::info!(
                 was_hdr,
                 want_hdr = cfg.hdr,
-                "video source: pooled capturer depth mismatch — opening a fresh screencast session"
+                was_metadata_cursor = was_meta,
+                want_metadata_cursor = metadata_cursor,
+                "video source: pooled capturer depth/cursor-mode mismatch — opening a fresh \
+                 screencast session"
             );
             drop(c);
             None
@@ -285,8 +316,13 @@ fn run(
             c
         }
         None if pf_host_config::config().video_source.as_deref() == Some("portal") => {
-            tracing::info!(hdr = cfg.hdr, "video source: portal desktop capture");
+            tracing::info!(
-            capture::open_portal_monitor(cfg.hdr).context("open portal capturer")?
+                hdr = cfg.hdr,
+                metadata_cursor,
+                "video source: portal desktop capture"
+            );
+            capture::open_portal_monitor(cfg.hdr, metadata_cursor)
+                .context("open portal capturer")?
         }
         None => {
             tracing::info!("video source: synthetic test pattern");
@@ -298,6 +334,7 @@ fn run(
     let result = stream_body(
         &mut capturer,
         None,
+        metadata_cursor,
         &sock,
         cfg,
         running,
@@ -308,7 +345,7 @@ fn run(
         on_lost,
     );
     capturer.set_active(false);
-    *video_cap.lock().unwrap() = Some((capturer, cfg.hdr));
+    *video_cap.lock().unwrap() = Some((capturer, cfg.hdr, metadata_cursor));
     result
 }
 
@@ -646,6 +683,10 @@ fn stream_body(
     // Re-open the video source on capture loss (virtual-display path → follow a Desktop<->Game switch);
     // `None` for the portal/synthetic source, which has nothing to re-detect (propagate the error).
     rebuild: Option<&dyn Fn() -> Result<Box<dyn Capturer>>>,
+    // The capture hands the encoder cursor bitmaps to composite (cursor-as-metadata negotiated
+    // because the resolved backend blends — see the callers). `false` = the pointer is embedded
+    // in the pixels (or absent), so the encoder is asked to composite nothing.
+    cursor_blend: bool,
     sock: &UdpSocket,
     cfg: StreamConfig,
     running: &Arc<AtomicBool>,
@@ -681,9 +722,9 @@ fn stream_body(
         // GameStream/Moonlight stays 4:2:0 — stock Moonlight clients can't decode 4:4:4, and the
         // Windows IDD-push capturer can't yet deliver full-chroma frames. 4:4:4 is punktfunk/1-native only.
         encode::ChromaFormat::Yuv420,
-        // Desktop monitor capture negotiates cursor-as-metadata where available — the encoder
+        // True only when THIS session's capture negotiated cursor-as-metadata — which the
-        // may be handed cursor bitmaps to composite.
+        // callers grant only where the resolved backend composites (`cursor_blend_capable`).
-        true,
+        cursor_blend,
     )
     .context("open video encoder for stream")?;
     // Tell the encoder how deep the capturer lets it pipeline. Without this an in-place backend
@@ -855,7 +896,7 @@ fn stream_body(
                     frame.is_cuda(),
                     gs_bit_depth(frame.format),
                     encode::ChromaFormat::Yuv420, // GameStream stays 4:2:0
-                    true,                         // metadata-cursor capture — see the first open
+                    cursor_blend,                 // same capture cursor mode — see the first open
                 )
                 .context("reopen encoder after rebuild")?;
                 // A rebuilt encoder starts unconfigured — same reason as the first open above.

crates/punktfunk-host/src/native.rs

@@ -1012,9 +1012,10 @@ async fn serve_session(
     // just never fires then.
     let (cursor_shape_tx, cursor_shape_rx) =
         tokio::sync::mpsc::unbounded_channel::<punktfunk_core::quic::CursorShape>();
-    // Negotiated cursor forwarding: MUST match the HOST_CAP_CURSOR bit the Welcome advertised
+    // Negotiated cursor forwarding: the HOST_CAP_CURSOR bit the Welcome advertised, read back
-    // (handshake::cursor_forward is the single predicate both read).
+    // rather than recomputed (`handshake::cursor_forward` computed it once, with the encoder
-    let cursor_forward = handshake::cursor_forward(hello.client_caps, compositor);
+    // blend-capability gate — re-running it here could drift, and would re-probe).
+    let cursor_forward = welcome.host_caps & punktfunk_core::quic::HOST_CAP_CURSOR != 0;
     // Who renders the pointer RIGHT NOW (client `CursorRenderMode`, flipped live by the mouse-
     // model chord): `true` = client draws (exclude + forward), `false` = host composites (the
     // capture model). Starts true — the pre-message behavior for cap sessions. Control task

crates/punktfunk-host/src/native/handshake.rs

@@ -12,31 +12,46 @@ use super::*;
 /// the client asked ([`CLIENT_CAP_CURSOR`](punktfunk_core::quic::CLIENT_CAP_CURSOR)) AND the
 /// capture path can deliver cursor metadata separately from the frame — the Linux portal
 /// `SPA_META_Cursor` path (not gamescope, whose capture paints no cursor at all), or Windows
-/// with a proto-v5 pf-vdisplay driver (the IddCx hardware-cursor channel, M2c). THE single
+/// with a proto-v5 pf-vdisplay driver (the IddCx hardware-cursor channel, M2c) — AND, on
-/// predicate: the Welcome's `HOST_CAP_CURSOR` bit and the session's forwarding/blend-off
+/// Linux, the encode backend this session resolves to can composite the pointer on demand
-/// wiring both read it, so they can never disagree.
+/// (`encode::cursor_blend_capable`): the channel's capture-mouse flip (`CursorRenderMode`,
+/// `client_draws = false`) makes the HOST draw the pointer, and on Linux the encoder is that
+/// compositing stage — granting the channel over a backend that can't blend (libav
+/// VAAPI/NVENC, software) shipped a cursorless stream on every capture-mode flip. Denied, the
+/// session keeps the pre-channel path: the compositor EMBEDS the pointer and the client never
+/// draws — never cursorless, never doubled. THE single predicate: the Welcome's
+/// `HOST_CAP_CURSOR` bit is computed from it, and the session wiring reads that bit back.
 pub(super) fn cursor_forward(
     client_caps: u8,
     compositor: Option<crate::vdisplay::Compositor>,
+    codec: crate::encode::Codec,
+    bit_depth: u8,
 ) -> bool {
     if client_caps & punktfunk_core::quic::CLIENT_CAP_CURSOR == 0 {
         return false;
     }
     #[cfg(target_os = "linux")]
     {
+        // CUDA-payload prediction — the same one `SessionPlan` makes: the NVIDIA resolution
+        // plus the zero-copy master switch. It decides direct-SDK NVENC (blends) vs libav
+        // NVENC (doesn't) inside the capability mirror.
+        let cuda_planned = !crate::encode::linux_zero_copy_is_vaapi() && crate::zerocopy::enabled();
         compositor.is_some_and(|c| c != crate::vdisplay::Compositor::Gamescope)
+            && crate::encode::cursor_blend_capable(codec, cuda_planned, bit_depth == 10)
     }
     #[cfg(target_os = "windows")]
     {
         // Windows (M2c): the pf-vdisplay driver must speak the v5 hardware-cursor channel —
         // DWM composites the pointer into the IDD frame otherwise, and forwarding a second
-        // copy would double it. The probe latches by opening the control device once.
+        // copy would double it. The probe latches by opening the control device once. The
-        let _ = compositor;
+        // encoder is deliberately NOT consulted: the IDD capturer itself composites on the
+        // capture-mouse flip (`set_cursor_forward`), so no Windows encode backend blends.
+        let _ = (compositor, codec, bit_depth);
         crate::vdisplay::manager::hw_cursor_capable()
     }
     #[cfg(not(any(target_os = "linux", target_os = "windows")))]
     {
-        let _ = compositor;
+        let _ = (compositor, codec, bit_depth);
         false
     }
 }
@@ -488,9 +503,10 @@ pub(super) async fn negotiate(
                 0
             }
             // Cursor channel granted (client asked + this capture path can deliver cursor
-            // metadata out of the frame) — the client turns its local renderer on ONLY when
+            // metadata out of the frame + the resolved encoder can composite on the
-            // it sees this bit, and serve_session wires forwarding from the same predicate.
+            // capture-mouse flip) — the client turns its local renderer on ONLY when it sees
-            | if cursor_forward(hello.client_caps, compositor) {
+            // this bit, and serve_session wires forwarding by reading the bit back.
+            | if cursor_forward(hello.client_caps, compositor, codec, bit_depth) {
                 punktfunk_core::quic::HOST_CAP_CURSOR
             } else {
                 0
@@ -536,9 +552,9 @@ pub(super) async fn negotiate(
             let (ctx_tx, ctx_rx) = std::sync::mpsc::sync_channel::<SessionContext>(1);
             let client_identity = endpoint::peer_fingerprint(conn);
             let client_hdr = hello.display_hdr;
-            // Same predicate the Welcome's HOST_CAP_CURSOR bit used — the prepared display and
+            // The bit the Welcome just advertised — read back rather than recomputed, so the
-            // the session wiring must agree with what we just advertised.
+            // prepared display and the session wiring cannot disagree with it.
-            let cursor_fw = cursor_forward(hello.client_caps, Some(comp));
+            let cursor_fw = welcome.host_caps & punktfunk_core::quic::HOST_CAP_CURSOR != 0;
             let (mode, shard_payload) = (hello.mode, welcome.shard_payload);
             let trace = bringup.clone();
             std::thread::Builder::new()

crates/punktfunk-host/src/native/stream.rs

@@ -1022,8 +1022,13 @@ pub(super) fn virtual_stream(ctx: SessionContext, prepared: Option<PreparedDispl
         // pointer compositor-EMBEDDED (`vd.set_hw_cursor(false)` → no cursor metadata, nothing to
         // blend), keeping the zero-cost pre-channel path. gamescope is the exception (Phase C):
         // it can't embed the pointer, so the host ALWAYS composites the XFixes-sourced cursor —
-        // the blend must be built for every gamescope session.
+        // the blend must be built for every gamescope session. (`cursor_forward` is already
-        ctx.compositor == pf_vdisplay::Compositor::Gamescope || ctx.cursor_forward,
+        // blend-gated: `handshake::cursor_forward` grants the channel only where
+        // `encode::cursor_blend_capable` says the resolved backend composites.)
+        crate::session_plan::cursor_blend_for(
+            ctx.cursor_forward,
+            ctx.compositor == pf_vdisplay::Compositor::Gamescope,
+        ),
         ctx.cursor_forward,
     );
     // gamescope: the XFixes cursor source feeds the always-on composite (Phase C). Set after
@@ -2098,8 +2103,10 @@ pub(super) fn virtual_stream(ctx: SessionContext, prepared: Option<PreparedDispl
                                         // capture-mode channel); a switch AWAY restores the prior
                                         // gating. `plan` is `Copy` — this is the value the rebuild
                                         // (and its `build_pipeline` attach) reads.
-                                        plan.cursor_blend = plan.cursor_forward
+                                        plan.cursor_blend = crate::session_plan::cursor_blend_for(
-                                            || c == crate::vdisplay::Compositor::Gamescope;
+                                            plan.cursor_forward,
+                                            c == crate::vdisplay::Compositor::Gamescope,
+                                        );
                                         plan.gamescope_cursor =
                                             c == crate::vdisplay::Compositor::Gamescope;
                                         gamescope_composite =
@@ -2987,7 +2994,10 @@ pub(super) fn prepare_display(
         // non-gamescope sessions get the pointer compositor-EMBEDDED, nothing to blend; the
         // mid-stream `CursorRenderMode` flip strips/keeps `frame.cursor` per tick for channel
         // sessions). gamescope (Phase C) can't embed → always composites the XFixes cursor.
-        compositor == pf_vdisplay::Compositor::Gamescope || cursor_forward,
+        crate::session_plan::cursor_blend_for(
+            cursor_forward,
+            compositor == pf_vdisplay::Compositor::Gamescope,
+        ),
         cursor_forward,
     );
     plan.gamescope_cursor = compositor == pf_vdisplay::Compositor::Gamescope;

crates/punktfunk-host/src/session_plan.rs

@@ -104,9 +104,13 @@ pub struct SessionPlan {
     /// AUs stay shard-aligned across mode/bitrate/stall rebuilds. `None` for the H.26x codecs.
     pub wire_chunk: Option<usize>,
     /// The session may hand the encoder cursor bitmaps to composite (cursor-as-metadata
-    /// captures — every non-gamescope compositor; gamescope embeds the pointer itself).
+    /// captures). Set via [`cursor_blend_for`] — the single platform rule — so it is `true` only
-    /// Encoders whose fast path cannot blend (the Vulkan EFC RGB-direct source) stay on their
+    /// where the ENCODER is the compositing stage (Linux cursor-forward and gamescope sessions);
-    /// blending path when this is set, so the pointer never silently vanishes from the stream.
+    /// Windows is always `false` (the IDD capturer composites the pointer itself). Encoders
+    /// whose fast path cannot blend (the Vulkan EFC RGB-direct source, native NV12) stay off
+    /// those shapes when this is set — see [`Self::output_format`] and
+    /// `encode::cursor_blend_capable`, the pre-open mirror that gates the cursor channel — so
+    /// the pointer never silently vanishes from the stream.
     pub cursor_blend: bool,
     /// The session negotiated the cursor-forward channel (M2/M2c): the client draws the pointer
     /// locally, so `cursor_blend` is off AND (on Windows) the capturer sets the driver's
@@ -198,13 +202,15 @@ impl SessionPlan {
             // Producer-native NV12 (gamescope) is consumable only by the Linux Vulkan Video
             // backend — resolved HERE from the plan's codec so the capturer never reaches back
             // into encode (the same one-way edge as `gpu` above). BUT the native-NV12 encode path
-            // has no CSC stage to fold the cursor into (it assumes gamescope embeds its pointer,
+            // has no CSC stage to fold the cursor into — so ANY cursor-compositing session
-            // which it does NOT into the PipeWire node) — so a gamescope-cursor session (Phase C)
+            // (gamescope Phase C, whose XFixes pointer is absent from the PipeWire node, AND a
-            // must capture RGB instead, routing to the compute-CSC / VkSlotBlend blend that draws
+            // cursor-forward session, whose capture-mouse flip needs the host composite on
-            // `frame.cursor`. Costs the RGB→NV12 CSC we'd otherwise skip; the native-NV12 cursor
+            // demand) must capture RGB instead, routing to the compute-CSC / VkSlotBlend blend
-            // blend is the perf-preserving follow-up.
+            // that draws `frame.cursor`. Costs the RGB→NV12 CSC we'd otherwise skip; the
+            // native-NV12 cursor blend is the perf-preserving follow-up. (`cursor_blend`
+            // subsumes `gamescope_cursor` — see [`cursor_blend_for`].)
             #[cfg(target_os = "linux")]
-            nv12_native: crate::encode::linux_native_nv12_ok(self.codec) && !self.gamescope_cursor,
+            nv12_native: crate::encode::linux_native_nv12_ok(self.codec) && !self.cursor_blend,
             #[cfg(not(target_os = "linux"))]
             nv12_native: false,
         }
@@ -217,6 +223,26 @@ pub(crate) fn resolve_topology() -> SessionTopology {
     SessionTopology::SingleProcess
 }
 
+/// THE rule for [`SessionPlan::cursor_blend`], shared by every resolve caller (initial plan and
+/// the mid-stream compositor re-gate) so they can't drift:
+/// * **Linux**: the encoder is the compositing stage — blend for a cursor-forward session (the
+///   capture-mouse flip needs the host composite on demand) and for gamescope (its capture
+///   carries no pointer at all; the XFixes-sourced cursor must be drawn into the video).
+/// * **Windows**: never — the IDD capturer composites the pointer itself (`cursor_blend.rs` /
+///   DWM), and no Windows encode backend reads `frame.cursor`. Asking the encoder anyway made
+///   `open_video`'s blends-cursor backstop fire spuriously on every cursor-channel session.
+pub(crate) fn cursor_blend_for(cursor_forward: bool, gamescope: bool) -> bool {
+    #[cfg(target_os = "windows")]
+    {
+        let _ = (cursor_forward, gamescope);
+        false
+    }
+    #[cfg(not(target_os = "windows"))]
+    {
+        cursor_forward || gamescope
+    }
+}
+
 #[cfg(target_os = "windows")]
 fn resolve_encoder() -> EncoderBackend {
     match crate::encode::windows_resolved_backend() {

crates/punktfunk-host/src/spike.rs

@@ -94,7 +94,9 @@ pub fn run(opts: Options) -> Result<()> {
                 want_hdr,
                 "spike source: xdg ScreenCast portal (live monitor)"
             );
-            capture::open_portal_monitor(want_hdr).context("open portal capturer")?
+            // Embedded cursor: the spike passes `cursor_blend = false` to its encoder open, so
+            // a metadata pointer would be composited by nothing.
+            capture::open_portal_monitor(want_hdr, false).context("open portal capturer")?
         }
         Source::KwinVirtual => {
             let compositor = crate::vdisplay::detect().unwrap_or(crate::vdisplay::Compositor::Kwin);